Array ( [0] => {{Short description|Human helminthiasis (infection by parasite)}} [1] => {{cs1 config|name-list-style=vanc}} [2] => {{Redirect|Elephant skin|the type of Precambrian and Cambrian seabed found fossil|Matground}} [3] => {{Infobox medical condition (new) [4] => | name = Onchocerciasis [5] => | synonyms = River blindness, Robles disease [6] => | image = Onchocerca volvulus emerging from a black fly.jpg [7] => | caption = An adult [[Simulium yahense|black fly]] with the parasite ''[[Onchocerca volvulus]]'' coming out of the insect's antenna, magnified 100× [8] => | pronounce = {{IPAc-en|ˌ|ɒ|ŋ|k|oʊ|s|ɜːr|ˈ|s|aɪ|ə|s|ᵻ|s|,_|-|ˈ|k|aɪ|-}} [9] => | field = [[Infectious disease (medical specialty)|Infectious disease]] [10] => | symptoms = Itching, bumps under the skin, [[blindness]] [11] => | complications = [12] => | onset = [13] => | duration = [14] => | causes = ''[[Onchocerca volvulus]]'' spread by a [[black fly]] [15] => | risks = [16] => | diagnosis = [17] => | differential = [18] => | prevention = Avoiding bites ([[insect repellent]], proper clothing) [19] => | treatment = [20] => | medication = [[Ivermectin]], [[doxycycline]] [21] => | prognosis = [22] => | frequency = 15.5 million (2015){{Cite journal |last1=Vos |first1=Theo |last2=Allen |first2= Christine |last3=Arora |first3=Megha |last4=Barber |first4=Ryan M |last5= Bhutta |first5=Zulfiqar A |last6=Brown |first6=Alexandria |last7= Carter |first7= Austin |last8=Casey |first8=Daniel C |last9=Charlson |first9=Fiona J |last10= Chen |first10=Alan Z |last11=Coggeshall |first11=Megan |last12=Cornaby |first12= Leslie |last13=Dandona |first13= Lalit |last14=Dicker |first14= Daniel J |last15=Dilegge |first15=Tina | display-authors = 3|date=8 October 2016 |title=Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990–2015: a systematic analysis for the Global Burden of Disease Study 2015 |journal= The Lancet |language=en |volume=388 |issue=10053 |pages=1545–1602 |doi=10.1016/S0140-6736(16)31678-6 |pmc=5055577 |pmid=27733282}} [23] => | deaths = [24] => }} [25] => [26] => '''Onchocerciasis''', also known as '''river blindness''', is a disease caused by infection with the [[parasitic worm]] ''[[Onchocerca volvulus]]''.{{cite web| title= Onchocerciasis Fact sheet N°374| url=https://www.who.int/mediacentre/factsheets/fs374/en/|website= who.int | publisher= World Health Organization |access-date=20 March 2014| date= March 2014|url-status=live|archive-url=https://web.archive.org/web/20140316195959/http://www.who.int/mediacentre/factsheets/fs374/en/|archive-date=16 March 2014}} Symptoms include severe itching, bumps under the skin, and [[blindness]]. It is the second-most common cause of blindness due to infection, after [[trachoma]]. [27] => [28] => [29] => The parasitic worm is spread by the bites of a [[black fly]] of the ''[[Simulium]]'' type. Usually, many bites are required before infection occurs.{{cite web| title= Parasites – Onchocerciasis (also known as River Blindness) Epidemiology & Risk Factors| url= https://www.cdc.gov/parasites/onchocerciasis/epi.html| work= CDC.gov | publisher = Centers for Disease Control and Prevention | place= US |access-date= 20 March 2014|date=21 May 2013 |url-status=live|archive-url= https://web.archive.org/web/20140419014141/http://www.cdc.gov/parasites/onchocerciasis/epi.html|archive-date=19 April 2014}} These flies live near rivers, hence the common name of the disease.{{cite web| title= Parasites: Onchocerciasis (also known as River Blindness) |work= CDC.gov | publisher = Centers for Disease Control and Prevention | place= US | url= https://www.cdc.gov/parasites/onchocerciasis/ |access-date=20 March 2014| date=21 May 2013| url-status=live |archive-url= https://web.archive.org/web/20140226071647/http://www.cdc.gov/parasites/onchocerciasis/|archive-date=26 February 2014}} Once inside a person, the worms create [[larvae]] that make their way out to the skin, where they can infect the next black fly that bites the person. There are a number of ways to make the diagnosis, including: placing a [[biopsy]] of the skin in [[normal saline]] and watching for the larva to come out; looking in the eye for larvae; and looking within the bumps under the skin for adult worms.{{cite web |title= Onchocerciasis (also known as River Blindness) Diagnosis |work= CDC.gov | publisher = Centers for Disease Control and Prevention |place= US |url= https://www.cdc.gov/parasites/onchocerciasis/diagnosis.html |access-date=20 March 2014 |date=21 May 2013 |url-status=live |archive-url= https://web.archive.org/web/20140419025103/http://www.cdc.gov/parasites/onchocerciasis/diagnosis.html |archive-date=19 April 2014 }} [30] => [31] => [32] => A [[vaccine]] against the disease does not exist. Prevention is by avoiding being bitten by flies.{{cite web |title=Onchocerciasis (also known as River Blindness) Prevention & Control |url= https://www.cdc.gov/parasites/onchocerciasis/prevent.html |work= CDC.gov | publisher = [[Centers for Disease Control and Prevention]] |place= US |access-date=20 March 2014 |date= May 21, 2013 |url-status= live |archive-url=https://web.archive.org/web/20140419012306/http://www.cdc.gov/parasites/onchocerciasis/prevent.html |archive-date=19 April 2014 }} This may include the use of [[insect repellent]] and proper clothing. Other efforts include those to decrease the fly population by spraying [[insecticide]]s. Efforts to eradicate the disease by treating entire groups of people twice a year are ongoing in a number of areas of the world. Treatment of those infected is with the medication [[ivermectin]] every six to twelve months. This treatment kills the larvae but not the adult worms.{{cite book|last=Brunette|first=Gary W.|title=CDC Health Information for International Travel 2012: The Yellow Book|year=2011|publisher=Oxford University Press| isbn= 978-0-19-983036-7| page= 258| url= https://books.google.com/books?id=5vCQpr1WTS8C&pg=PA258|url-status= live|archive-url= https://web.archive.org/web/20170908221523/https://books.google.com/books?id=5vCQpr1WTS8C&pg=PA258|archive-date=2017-09-08}} The antibiotic [[doxycycline]] weakens the worms by killing an [[endosymbiont|associated]] bacterium, ''[[Wolbachia]]'', and is recommended by some as well. The lumps under the skin may also be removed by surgery.{{cite book |last=Murray |first=Patrick |title= Medical microbiology |year=2013 |publisher= Elsevier Saunders |location= Philadelphia |isbn=978-0-323-08692-9 |page=792 |url= https://books.google.com/books?id=RBEVsFmR2yQC&pg=PA792 |edition= 7th |url-status=live |archive-url=https://web.archive.org/web/20170908221523/https://books.google.com/books?id=RBEVsFmR2yQC&pg=PA792 |archive-date=2017-09-08 }} [33] => [34] => [35] => According to the Center for Disease Control and Prevention, as of 2017, about 20.9 million people were infected with Onchocerciasis, and an estimated 1.15 million have some amount of loss of vision from the infection. Most infections occur in [[sub-Saharan Africa]], although cases have also been reported in [[Yemen]] and isolated areas of [[Central America|Central]] and [[South America]]. In 1915, the physician [[Rodolfo Robles]] first linked the worm to eye disease.{{cite book |editor1=Eldridge, Bruce F. |editor2=Edman, John D. |editor3=Edman, J. |title=Medical entomology |year=2004 |publisher= Kluwer Academic |location=Dordrecht |isbn=978-1-4020-1794-0 |page=301 |chapter-url=https://books.google.com/books?id=C7OxOqTKYS8C&pg=PA301 |edition=Revised |author1=Lok, James B. |author2= Walker, Edward D. |author3= Scoles, Glen A. |chapter=9. Filariasis |url-status=live |archive-url=https://web.archive.org/web/20170908221523/https://books.google.com/books?id=C7OxOqTKYS8C&pg=PA301 |archive-date=2017-09-08 }} It is listed by the [[World Health Organization]] (WHO) as a [[neglected tropical disease]]. In 2013 Colombia became the first country to eradicate the disease.{{Cite web| title=Onchocerciasis (river blindness) |url=https://www.who.int/news-room/fact-sheets/detail/onchocerciasis|date=11 January 2022|access-date=2022-02-06|website= who.int | publisher= World Health Organization |language=en}} [36] => [37] => ==Cause== [38] => Onchocerciasis is a [[Parasitism|parasitic]] infection caused by the roundworm species ''[[Onchocerca volvulus]]''. The larvae of ''O. volvulus'' enter a human host when an infected female adult fly from the family ''Simulium'' bites them. After that, it can take up to three months for the worms to mature under the skin of its host.{{Cite journal |last=Burnham |first=Gilbert |date=May 1998 |title=Onchocerciasis |journal=The Lancet |language=en |volume=351 |issue=9112 |pages=1341–1346 |doi=10.1016/S0140-6736(97)12450-3|pmid=9643811 |s2cid=265737560 |doi-access=free }} The worms mainly get nutrients for growth in humans from blood, but they have also been seen to rely on other bodily fluids such as cerebrospinal fluid, and urine. It is common to see nodules formed in the skin where the adult worms reside and mate. However, these worms will often travel throughout the body using blood vessels in connective tissues and will even settle behind the cornea.{{Cite web |last=Dalton |first=Mark |date=2001 |title=Onchocerca volvulus |url=https://animaldiversity.org/accounts/Onchocerca_volvulus/#food_habits |access-date=2023-11-18 |website=Animal Diversity Web}} [39] => [40] => ===Life cycle=== [41] => The life of the parasite can be traced through the black fly and the human hosts in the following steps:{{Cite web|url=https://www.cdc.gov/parasites/onchocerciasis/biology.html|title=Parasites - Onchocerciasis (also known as River Blindness)|date=2019-04-19|website=Centers for Disease Control and Prevention}}{{Cite web|url=https://web.stanford.edu/class/humbio103/ParaSites2006/Onchocerciasis/life%20cycle.html|title=Life Cycle|website=Stanford University|access-date=2018-10-06|archive-date=2020-08-06|archive-url=https://web.archive.org/web/20200806034959/https://web.stanford.edu/class/humbio103/ParaSites2006/Onchocerciasis/life%20cycle.html}} [42] => [43] => # A ''Simulium'' female black fly takes a blood meal on an infected human host, and ingests microfilaria. [44] => # The microfilaria enter the gut and thoracic flight muscles of the black fly, progressing into the first larval stage (J1.). [45] => # The larvae mature into the second larval stage (J2.), and move to the proboscis and into the saliva in its third larval stage (J3.). Maturation takes about seven days. [46] => # The black fly takes another blood meal, passing the larvae into the next human host's blood. [47] => # The larvae migrate to the subcutaneous tissue and undergo two more molts. They form nodules as they mature into adult worms over six to 12 months. [48] => # After maturing, adult male worms mate with female worms in the subcutaneous tissue to produce between 700 and 1,500 microfilaria per day. [49] => # The microfilaria migrate to the skin during the day, and the black flies only feed in the day, so the parasite is in a prime position for the female fly to ingest it. Black flies take blood meals to ingest these microfilaria to restart the cycle. [50] => [51] => ==Signs and symptoms== [52] => It is possible for the larvae to move through the body without triggering a response from the host's immune system, so some people who are infected with the parasite experience no symptoms; the Global Burden of Disease Study estimated that in 2017 there were at least 20.9 million people infected worldwide, of which 14.6 million had skin disease symptoms and 1.15 million experienced symptoms that impacted vision.{{cite web |title=Onchocerciasis FAQs |url=https://www.cdc.gov/parasites/onchocerciasis/gen_info/faqs.html |access-date=18 November 2023 |website=Center for Disease Control |date=17 September 2020 |publisher=CDC}} After a blackfly bite, it can take 12–18 months for the larvae to develop into mature adult worms that will produce their own larvae, which is what leads to the development of symptoms.{{cite web |title=Onchocerciasis FAQs |url=https://www.cdc.gov/parasites/onchocerciasis/gen_info/faqs.html |access-date=18 November 2023 |website=Center for Disease Control|date=17 September 2020 }} Almost all the clinical manifestations of onchocerciasis are due to localized host inflammatory responses to dead or dying microfilariae (larvae).{{cite journal |last1=Burnham |first1=Gilbert |date=May 2, 1998 |title=Onchocerciasis |url=https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(97)12450-3.pdf |journal=The Lancet |volume=351 |issue=9112 |pages=1341–1346 |doi=10.1016/S0140-6736(97)12450-3 |pmid=9643811 |s2cid=265737560 |access-date=18 November 2023}} The signs and symptoms of onchocerciasis are usually divided into two categories, skin and eye symptoms. [53] => [54] => Skin symptoms will develop years before any vision problems. These symptoms include:{{Cite web |title=Defeating River Blindness - USF Magazine Summer 2013 |url=http://dev.magazine.usf.edu/2013/summer/features/defeating-river-blindness.aspx |access-date=2023-12-11 |website=dev.magazine.usf.edu}} [55] => [56] => * Intense itching [57] => * Swelling [58] => * Inflammation [59] => * Depigmentation [60] => * Hyperpigmentation [61] => * Rash [62] => * Nodules under the skin [63] => * Skin atrophy [64] => * Hanging groin (folds of inelastic atrophic skin in the groin associated with enlarged lymph nodes) [65] => [66] => Eye symptoms include:{{cite web |title=Onchocerciasis (River Blindness) |url=https://my.clevelandclinic.org/health/diseases/24868-onchocerciasis-river-blindness |access-date=18 November 2023 |website=Cleveland Clinic}} [67] => [68] => * Vision impairment, low vision, or permanent blindness. [69] => * Clouding of the cornea [70] => * Light sensitivity [71] => * Lesions on eyes [72] => * Glaucoma [73] => * Eye pain [74] => * Eye redness [75] => [76] => Eye symptoms provides the common name associated with onchocerciasis, river blindness, and may involve any part of the eye from conjunctiva and cornea to [[uvea]] and posterior segment, including the [[retina]] and [[optic nerve]]. The microfilariae migrate to the surface of the [[cornea]]. Punctate [[keratitis]] occurs in the infected area. This clears up as the inflammation subsides. However, if the infection is chronic, sclerosing keratitis can occur, making the affected area become [[Opacity (optics)|opaque]]. Over time, the entire cornea may become opaque, thus leading to blindness. Some evidence suggests the effect on the cornea is caused by an immune response to bacteria present in the worms. [77] => [78] => === Mazzotti reaction === [79] => {{main|Mazzotti reaction}} [80] => [81] => The Mazzotti reaction, first described in 1948, is a symptom complex seen in patients after undergoing treatment of onchocerciasis with the medication [[diethylcarbamazine]] (DEC). Mazzotti reactions can be life-threatening, and are characterized by [[fever]], [[urticaria]], [[Lymphadenopathy|swollen and tender lymph nodes]], [[tachycardia]], [[hypotension]], [[arthralgias]], [[oedema]], and [[abdominal pain]] that occur within seven days of treatment of microfilariasis.{{cite journal |last1=Babalola |first1=Olufemi |date=2011 |title=Ocular onchocerciasis: current management and future prospects |journal=Clinical Ophthalmology |volume=5 |pages=1479–1491 |doi=10.2147/OPTH.S8372 |pmid=22069350 |pmc=3206119 |doi-access=free }} [82] => [[File:Epikutanni-test.jpg|thumb|[[Patch test]]]] [83] => The phenomenon is so common when DEC is used that this drug is the basis of a [[Patch test|skin patch test]] used to confirm that diagnosis. The drug patch is placed on the skin, and if the patient is infected with ''O. volvulus'' microfilaria, localized [[pruritus]] and urticaria are seen at the application site.{{cite web |title=Mazzotti Reaction | MicrobLog: Microbiology Training |url=http://microblog.me.uk/420 |url-status=live |archive-url=https://web.archive.org/web/20101220070921/http://microblog.me.uk/420 |archive-date=2010-12-20 |access-date=2011-01-25}} [84] => [85] => ===Nodding disease=== [86] => {{Main|Nodding disease}} [87] => [88] => This is an unusual form of epidemic epilepsy associated with onchocerciasis although definitive link has not been established. This syndrome was first described in [[Tanzania]] by Louise Jilek-Aall, a Norwegian psychiatric doctor in Tanzanian practice, during the 1960s. It occurs most commonly in [[Uganda]] and [[South Sudan]]. It manifests itself in previously healthy 5–15-year-old children, is often triggered by eating or low temperatures and is accompanied by cognitive impairment. Seizures occur frequently and may be difficult to control. The [[electroencephalogram]] is abnormal but [[cerebrospinal fluid]] (CSF) and magnetic resonance imaging (MRI) are normal or show non-specific changes. If there are abnormalities on the MRI, they are usually present in the [[hippocampus]].{{cite journal |vauthors=Dowell SF, Sejvar JJ, Riek L, Vandemaele KA, Lamunu M, Kuesel AC, Schmutzhard E, Matuja W, Bunga S, Foltz J, Nutman TB, Winkler AS, Mbonye AK |year=2013 |title=Nodding syndrome |journal=[[Emerg Infect Dis]] |volume=19 |issue=9 |pages=1374–3 |doi=10.3201/eid1909.130401 |pmc=3810928 |pmid=23965548}} [89] => [90] => ==Diagnosis== [91] => [92] => When a clinical diagnosis of onchocerciasis is obtained, doctors take small snips of skin containing 3–5 mg of skin tissue. The skin samples taken are only from the upper [[dermis]].{{Cite journal |last=Klarmann-Schulz |first=Ute |date=2017-09-12 |title=Treatment of lymphatic filariasis and onchocerciasis – current and new therapeutic approaches |website=dx.doi.org|doi=10.26226/morressier.5991c409d462b80292388d01 }} These samples will then be soaked in saline and examined underneath a microscope to check for the presence of [[microfilaria]]. If the number of microfilaria is undetectable in the samples, the Mazzotti test is then used. In this test, 6 mg of [[diethylcarbamazine]] is administered to the affected area. If the patient experiences intense inflammation or itching in the affected area Microfilaria is present. Slit lamp eye exams are used to identify signs of the parasites in and around the eyes of patients whose eyes are affected. Antibody tests when available can aid in the diagnosis of Onchocerciasis.{{citation needed|date=March 2023}} [93] => [94] => ===Classification=== [95] => Onchocerciasis causes different kinds of skin changes, which vary in different geographic regions; it may be divided into the following phases or types:{{cite book |author1=James, William D. |author2=Berger, Timothy G. |author3=Elston, Dirk M |author4=Odom, Richard B. |title=Andrews' Diseases of the Skin: clinical dermatology |publisher=Saunders Elsevier |year=2006 |edition=10th |isbn=978-0-7216-2921-6 |oclc=62736861 }}{{rp|440–441}}{{Verify source|date=May 2010}} [96] => [97] => ;''Erisipela de la costa'' [98] => :An acute phase, it is characterized by swelling of the face, with [[erythema]] and [[itching]].{{rp|440}} This skin change, ''erisípela de la costa'', of acute onchocerciasis is most commonly seen among victims in Central and South America.{{cite web |url=http://emedicine.medscape.com/article/1109642-overview |title=Filariasis |author=Marty AM |access-date=2009-10-22 |work=eMedicine |url-status=live |archive-url=https://web.archive.org/web/20090927035901/http://emedicine.medscape.com/article/1109642-overview |archive-date=2009-09-27 }} [99] => [100] => ;''Mal morando'' [101] => :This cutaneous condition is characterized by [[inflammation]] accompanied by [[hyperpigmentation]].{{rp|440}} [102] => ;''Sowda'' [103] => :A cutaneous condition, it is a localized type of onchocerciasis.{{rp|440}} [104] => [105] => Additionally, the various skin changes associated with onchocerciasis may be described as follows:{{rp|440}} [106] => [107] => ;Leopard skin [108] => :The spotted [[depigmentation]] of the skin that may occur with onchocerciasis{{rp|440}} [109] => ;Elephant skin [110] => :The thickening of human skin that may be associated with onchocerciasis{{rp|440}} [111] => ;Lizard skin [112] => :The thickened, wrinkled skin changes that may result with onchocerciasis{{rp|441}} [113] => [114] => ==Prevention== [115] => Various control programs aim to stop onchocerciasis from being a [[public health]] problem.{{Cite web |title=Onchocerciasis (river blindness) |url=https://www.who.int/news-room/fact-sheets/detail/onchocerciasis |access-date=2023-11-16 |website=www.who.int |language=en}} The Onchocerciasis Control Programme (OCP) launched in 1974, and at its peak, covered 30 million people in the following countries: Benin, Burkina Faso, Côte d'Ivoire, Ghana, Togo, Mali, and Niger. The OCP utilized the following initiatives: the use of [[larvicide]] spraying into fast-flowing rivers to control black fly populations, and from 1988 onwards, the use of [[ivermectin]] to treat infected people as a core treatment therapy. Alongside the OCP, a joint effort of the [[World Health Organization]], the [[World Bank]], the [[United Nations Development Programme]], and the UN [[Food and Agriculture Organization]], was considered to be a success in controlling onchocerciasis, and in 2002 shifted from control of onchocerciasis to elimination. According to the World Health Organization, four countries have eradicated onchocerciasis that include: Colombia (2013), Ecuador (2014), Mexico (2015), and Guatemala (2016). Continued monitoring ensures onchocerciasis cannot reinvade the area through the OCP.{{Cite web |date=2009-11-24 |title=WHO {{!}} Onchocerciasis Control Programme (OCP) |url=http://www.who.int/blindness/partnerships/onchocerciasis_OCP/en/index.html |access-date=2023-12-10 |archive-url=https://web.archive.org/web/20091124092752/http://www.who.int/blindness/partnerships/onchocerciasis_OCP/en/index.html |archive-date=2009-11-24 }} Other effective prevention efforts include personal protection from black fly bites. Recommended protection measures from the CDC include using insect repellents and wearing long sleeves and pants to eliminate exposed skin. Using insect repellent that contains N,N-Diethyl-meta-toluamide ([[DEET]]) as well as clothing treated with [[permethrin]].{{Cite web |last=Prevention |first=CDC-Centers for Disease Control and |date=2019-09-09 |title=CDC - Onchocerciasis - Prevention & Control |url=https://www.cdc.gov/parasites/onchocerciasis/prevent.html |access-date=2023-12-10 |website=www.cdc.gov |language=en-us}} [116] => [117] => === Elimination === [118] => In 1995, the African Programme for Onchocerciasis Control (APOC) initiated to eliminate onchocerciasis from African countries in which the disease was endemic.{{Cite journal |last=Amazigo |first=U. |date=September 2008 |title=The African Programme for Onchocerciasis Control (APOC) #:~:text=The%20African%20Programme%20for%20Onchocerciasis%20Control%20(APOC)%20was%20launched%20in,which%20the%20disease%20was%20endemic. |journal=Annals of Tropical Medicine and Parasitology |volume=102 |pages=19–22 |doi=10.1179/136485908X337436 |issn=0003-4983 |pmid=18718149|s2cid=25432708 }} The initiative relied primarily on the use of the antiparasitic drug [[ivermectin]]. The initiative was to set up community-directed treatment with ivermectin for those at risk of infection. Overall transmission has declined.{{Cite web |date=2009-08-28 |title=WHO {{!}} African Programme for Onchocerciasis Control (APOC) |url=http://www.who.int/blindness/partnerships/APOC/en/index.html |access-date=2023-12-10 |archive-url=https://web.archive.org/web/20090828025547/http://www.who.int/blindness/partnerships/APOC/en/index.html |archive-date=2009-08-28 }} The APOC ended in 2015 and aspects of its work has been taken over by the WHO Expanded Special Programme for the Elimination of Neglected Tropical Diseases (ESPEN). As in the Americas, the objective of ESPEN is working with Government Health Ministries and partner non-governmental organizations, toward elimination of transmission of onchocerciasis. This requires consistent annual treatment of 80% of the population in endemic areas for at least 10–12 years, the life span of the adult worm. No African country has so far verified elimination of onchocerciasis, but treatment has stopped in some areas (e.g. Nigeria), following epidemiological and entomological assessments that indicated that no ongoing transmission could be detected.{{Cite journal |last1=Rebollo |first1=Maria P |last2=Zoure |first2=Honorat |last3=Ogoussan |first3=Kisito |last4=Sodahlon |first4=Yao |last5=Ottesen |first5=Eric A |last6=Cantey |first6=Paul T |date=March 2018 |title=Onchocerciasis: shifting the target from control to elimination requires a new first-step—elimination mapping |journal=International Health |volume=10 |issue=Suppl 1 |pages=i14–i19 |doi=10.1093/inthealth/ihx052 |issn=1876-3413 |pmc=5881272 |pmid=29471341}} [119] => [120] => In 1992, the Onchocerciasis Elimination Programme for the Americas (OEPA), was launched.{{Cite web |date=2011-04-16 |title=WHO {{!}} Onchocerciasis Elimination Program for the Americas (OEPA) |url=http://www.who.int/blindness/partnerships/onchocerciasis_oepa/en/index.html |access-date=2023-12-10 |archive-url=https://web.archive.org/web/20110416031503/http://www.who.int/blindness/partnerships/onchocerciasis_oepa/en/index.html |archive-date=2011-04-16 }} On July 29, 2013, the [[Pan American Health Organization]] (PAHO) announced that after 16 years of efforts, [[Colombia]] had become the first country in the world to eliminate onchocerciasis.{{Cite web |date=2013-07-30 |title=News Scan for Jul 30, 2013 {{!}} CIDRAP |url=https://www.cidrap.umn.edu/foodborne-disease/news-scan-jul-30-2013 |access-date=2023-12-10 |website=www.cidrap.umn.edu |language=en}} Countries that received verification of elimination were Colombia in 2013, Ecuador in 2015, and Guatemala in 2016.{{Cite web |title=Onchocerciasis (river blindness) |url=https://www.who.int/news-room/fact-sheets/detail/onchocerciasis |access-date=2023-12-10 |website=www.who.int |language=en}} The key factor in elimination was mass administration of ivermectin. The OEPA projection was that the disease would be eliminated from all remaining countries in the Americas by 2012.{{Cite journal |last=Sauerbrey |first=M. |date=July 2013 |title=The Onchocerciasis Elimination Program for the Americas (OEPA) |url=http://www.tandfonline.com/doi/full/10.1179/136485908X337454 |journal=Annals of Tropical Medicine & Parasitology |language=en |volume=102 |issue=sup1 |pages=25–29 |doi=10.1179/136485908X337454 |pmid=18718151 |s2cid=39612786 |issn=0003-4983}} In September 2015, the OEPA announced that onchocerciasis only remained in a remote region on the border of Brazil and Venezuela.{{Cite web |last=Staff |date=2015-09-29 |title=Brazil and Venezuela border is the last place in the Americas with river blindness |url=https://outbreaknewstoday.com/brazil-and-venezuela-border-is-the-last-place-in-the-americas-with-river-blindness-13946/ |access-date=2023-12-10 |website=Outbreak News Today |language=en-US}} The area is home to the [[Yanomami]] indigenous people. [121] => [122] => No vaccine to prevent onchocerciasis infection in humans is available. This is due to two potential target product profiles (TPPs) that have to be in consideration when developing a vaccine for onchocerciasis.{{Cite web |title=Target product profiles |url=https://www.who.int/observatories/global-observatory-on-health-research-and-development/analyses-and-syntheses/target-product-profile/who-target-product-profiles |access-date=2023-12-10 |website=www.who.int |language=en}} This includes the development of a preventive vaccine for use in children five years or less in age, as this population does not receive ivermectin. Development of a therapeutic vaccine is also necessary that targets adult worms, microfilariae, and the causative agents of pathology and transmission, or both, for children and adults with ''O. volvulus'' infection.{{Cite journal |last1=Hotez |first1=Peter J. |last2=Bottazzi |first2=Maria Elena |last3=Zhan |first3=Bin |last4=Makepeace |first4=Benjamin L. |last5=Klei |first5=Thomas R. |last6=Abraham |first6=David |last7=Taylor |first7=David W. |last8=Lustigman |first8=Sara |date=2015-01-29 |title=The Onchocerciasis Vaccine for Africa—TOVA—Initiative |journal=PLOS Neglected Tropical Diseases |volume=9 |issue=1 |pages=e0003422 |doi=10.1371/journal.pntd.0003422 |issn=1935-2727 |pmc=4310604 |pmid=25634641 |doi-access=free }} [123] => [124] => ==Treatment== [125] => [[File:68-4062-1 (ATED).jpg|thumb|The burden of onchocerciasis: children leading blind adults in Africa]] [126] => In [[mass drug administration]] (MDA) programmes, the treatment for onchocerciasis is [[ivermectin]] (trade name: Mectizan). [[Ivermectin]] is administered four times a year and will be continually administered for 10–14 years due to the lifespan of the adult worm. Intense skin itching is eventually relieved, and the progression towards blindness is halted. The drug works by reducing the release of larvae from the adult worm but the drug does not kill it. However the drug does not prevent transmission of Onchocerciasis.{{Cite journal |last1=Borsboom |first1=Gerard JJM |last2=Boatin |first2=Boakye A |last3=Nagelkerke |first3=Nico JD |last4=Agoua |first4=Hyacinthe |last5=Akpoboua |first5=Komlan LB |last6=Alley |first6=E William Soumbey |last7=Bissan |first7=Yeriba |last8=Renz |first8=Alfons |last9=Yameogo |first9=Laurent |last10=Remme |first10=Jan HF |last11=Habbema |first11=J Dik F |date=2003-03-24 |title=Impact of ivermectin on onchocerciasis transmission: assessing the empirical evidence that repeated ivermectin mass treatments may lead to elimination/eradication in West-Africa |journal=Filaria Journal |volume=2 |issue=1 |page=8 |doi=10.1186/1475-2883-2-8 |issn=1475-2883 |pmid=12769825|pmc=156613 |doi-access=free }} It however reduces morbidity and has shown promising results to eliminate in some endemic areas of Africa{{Cite journal |last1=Diawara |first1=Lamine |last2=Traoré |first2=Mamadou O. |last3=Badji |first3=Alioune |last4=Bissan |first4=Yiriba |last5=Doumbia |first5=Konimba |last6=Goita |first6=Soula F. |last7=Konaté |first7=Lassana |last8=Mounkoro |first8=Kalifa |last9=Sarr |first9=Moussa D. |last10=Seck |first10=Amadou F. |last11=Toé |first11=Laurent |last12=Tourée |first12=Seyni |last13=Remme |first13=Jan H. F. |date=2009-07-21 |title=Feasibility of Onchocerciasis Elimination with Ivermectin Treatment in Endemic Foci in Africa: First Evidence from Studies in Mali and Senegal |journal=PLOS Neglected Tropical Diseases |language=en |volume=3 |issue=7 |pages=e497 |doi=10.1371/journal.pntd.0000497 |pmid=19621091 |pmc=2710500 |s2cid=2049325 |issn=1935-2735 |doi-access=free }} [127] => [128] => Ivermectin treatment is particularly effective because it only needs to be taken once or twice a year, needs no refrigeration, and has a wide [[Therapeutic index|margin of safety]], with the result that it has been widely given by minimally trained community health workers.{{cite journal |title=Ivermectin and River Blindness |vauthors=Rea PA, Zhang V, Baras YS |journal=[[American Scientist]] |volume=98 |issue=4 |pages=294–303 |year=2010 |url=http://www.americanscientist.org/issues/feature/2010/4/ivermectin-and-river-blindness |archive-url=https://web.archive.org/web/20100705115143/http://www.americanscientist.org/issues/feature/2010/4/ivermectin-and-river-blindness |archive-date=2010-07-05 |access-date=2010-06-20 }} Patients taking the drug for the treatment of onchocerciasis may have adverse effects within 1–2 days after the drug is administered. Symptoms of urticaria, pruritus, fever, dermatitis, myalgia, urticaria, swelling of face and limbs, or postural hypotension. [129] => [130] => ===Antibiotics=== [131] => For the treatment of individuals, [[doxycycline]] is used to kill the ''[[Wolbachia]]'' bacteria that live in adult worms. This adjunct therapy has been shown to significantly lower microfilarial loads in the host, and may kill the adult worms, due to the symbiotic relationship between ''Wolbachia'' and the worm.{{cite web |url=https://www.cdc.gov/parasites/onchocerciasis/treatment.html |title=CDC - Onchocerciasis - Treatment |access-date=2017-05-15 |url-status=live |archive-url=https://web.archive.org/web/20170524051749/https://www.cdc.gov/parasites/onchocerciasis/treatment.html |archive-date=2017-05-24 }}{{cite book |author1=Trattler, Bill |author2=Gladwin, Mark |title=Clinical Microbiology Made Ridiculously Simple |publisher=MedMaster |location=Miami |year=2007 |isbn=978-0-940780-81-1 |oclc=156907378 }}{{cite book |vauthors=Taylor MJ, Bandi C, Hoerauf A |title=''Wolbachia''. Bacterial endosymbionts of filarial nematodes |journal=Advances in Parasitology |series=[[Advances in Parasitology]] Vol. 60 |pages=245–84 |year=2005 |volume=60 |publisher=Academic Press |pmid=16230105 |doi=10.1016/S0065-308X(05)60004-8 |isbn=978-0-12-031760-8 }} In four separate trials over ten years with various dosing regimens of doxycycline for individualized treatment, doxycycline was found to be effective in sterilizing the female worms and reducing their numbers over a period of four to six weeks. Research on other antibiotics, such as [[rifampicin]], has shown it to be effective in animal models at reducing ''Wolbachia'' both as an alternative and as an adjunct to doxycycline.{{cite journal |title=Filariasis: new drugs and new opportunities for lymphatic filariasis and onchocerciasis |author=Hoerauf A |s2cid=26046513 |journal=[[Current Opinion in Infectious Diseases]] |year=2008 |volume=21 |issue=6 |pages=673–81 |pmid=18978537 |doi=10.1097/QCO.0b013e328315cde7}} However, doxycycline treatment requires daily dosing for at least four to six weeks, making it more difficult to administer in the affected areas. [132] => [133] => ===Ivermectin=== [134] => [[Ivermectin]] kills the parasite by interfering with the nervous system and muscle function, in particular, by enhancing inhibitory [[neurotransmission]]. The drug binds to and activates [[glutamate-gated chloride channel]]s. These channels, present in [[neurons]] and [[myocytes]], are not [[invertebrate]]-specific, but are protected in [[vertebrates]] from the action of ivermectin by the [[blood–brain barrier]]. Ivermectin is thought to irreversibly activate these channel receptors in the worm, eventually causing an [[inhibitory postsynaptic potential]]. The chance of a future [[action potential]] occurring in synapses between neurons decreases and the nematodes experience [[flaccid paralysis]] followed by death.{{cite journal |vauthors=Yates DM, Wolstenholme AJ |title=An ivermectin-sensitive glutamate-gated chloride channel subunit from Dirofilaria immitis |journal=International Journal for Parasitology |volume=34 |issue=9 |date=August 2004 |pages=1075–81 |doi=10.1016/j.ijpara.2004.04.010 |pmid=15313134}}{{cite journal |author=Harder A |s2cid=41860363 |title=Chemotherapeutic approaches to nematodes: current knowledge and outlook |journal=Parasitology Research |volume=88 |issue=3 |pages=272–7 |doi=10.1007/s00436-001-0535-x |pmid=11954915 |year=2002 }}{{cite journal |journal=Parasitology |year=2005 |volume=131 |issue=Suppl:S85–95 |title=Glutamate-gated chloride channels and the mode of action of the avermectin/milbemycin anthelmintics |vauthors=Wolstenholme AJ, Rogers AT |pmid=16569295 |pages=S85–95 |doi=10.1017/S0031182005008218|s2cid=14474894 }} [135] => [136] => Ivermectin is directly effective against the larval stage microfilariae of ''O. volvulus''; they are paralyzed and can be killed by [[eosinophils]] and [[macrophages]]. It does not kill adult females (macrofilariae), but does cause them to cease releasing microfilariae, perhaps by paralyzing the reproductive tract. Ivermectin is very effective in reducing microfilarial load and reducing number of punctate opacities in individuals with onchocerciasis.{{cite journal |vauthors=Ejere HO, Schwartz E, Wormald R, Evans JR |title= Ivermectin for onchocercal eye disease (river blindness) |journal=Cochrane Database Syst Rev |volume=8 |issue= 8 |pages= CD002219 |date=2012 |pmid= 22895928|doi= 10.1002/14651858.CD002219.pub2 |pmc=4425412}} [137] => [138] => ===Moxidectin=== [139] => After two decades of research, moxidectin was approved by the U.S. Food and Drug Administration in 2018 for use in ages 12 and older. Ongoing studies are looking to identify doses that will be safe for children ages 4–11.{{Cite web |title=Progress on moxidectin for onchocerciasis elimination |url=https://tdr.who.int/newsroom/news/item/14-03-2022-progress-on-moxidectin-for-onchocerciasis-elimination |access-date=2022-12-13 |website=tdr.who.int |language=en}} The oral dosage for moxidectin in adults and children 12 and up is 8 mg in a single dose.{{Cite web |title=Moxidectin (Oral Route) Proper Use - Mayo Clinic |url=https://www.mayoclinic.org/drugs-supplements/moxidectin-oral-route/proper-use/drg-20443828?p=1 |access-date=2022-12-13 |website=www.mayoclinic.org}} Moxidectin has been found to more strongly suppress the ''O.'' ''volvulus'' microfilariae for longer than ivermectin treatments, with peak clearance of microfilariae in the skin at one month after treatment. At six months post treatment, many individuals treated with moxidectin have no detectable microfilariae present in their skin.{{Cite journal |last1=Milton |first1=Philip |last2=Hamley |first2=Jonathan I. D. |last3=Walker |first3=Martin |last4=Basáñez |first4=María-Gloria |date=2020-11-01 |title=Moxidectin: an oral treatment for human onchocerciasis |journal=Expert Review of Anti-infective Therapy |language=en |volume=18 |issue=11 |pages=1067–1081 |doi=10.1080/14787210.2020.1792772 |pmid=32715787 |s2cid=220798707 |issn=1478-7210|doi-access=free |hdl=10044/1/81294 |hdl-access=free }} [140] => [141] => ==Epidemiology== [142] => [[File:Onchocerciasis world map - DALY - WHO2002.svg|thumb|upright=1.15|[[Disability-adjusted life year]] for onchocerciasis per 100,000 inhabitants{{Div col|small=yes|colwidth=10em}} [143] => {{legend|#b3b3b3|not endemic}} [144] => {{legend|#ffff65|less than 10}} [145] => {{legend|#fff200|10–50}} [146] => {{legend|#ffdc00|50–60}} [147] => {{legend|#ffc600|60–70}} [148] => {{legend|#ffb000|70–80}} [149] => {{legend|#ff9a00|80–90}} [150] => {{legend|#ff8400|90–100}} [151] => {{legend|#ff6e00|100–150}} [152] => {{legend|#ff5800|150–200}} [153] => {{legend|#ff4200|200–300}} [154] => {{legend|#ff2c00|300–400}} [155] => {{legend|#cb0000|>400}} [156] => {{div col end}}]] [157] => About 21 million people were infected with this [[parasite]] in 2017; about 1.2 million of those had vision loss.{{cite web |title=Onchocerciasis (river blindness) |url=https://www.who.int/news-room/fact-sheets/detail/onchocerciasis |website=www.who.int |access-date=15 March 2020 |language=en}} As of 2017, about 99% of onchocerciasis cases occurred in [[Africa]]. Onchocerciasis is currently relatively common in 31 African countries, [[Yemen]], and isolated regions of South America.{{cite web |url=http://www.stanford.edu/class/humbio103/ParaSites2006/Onchocerciasis/Epidemiology.html |title=Epidemiology |publisher=Stanford University |year=2006 |url-status=live |archive-url=https://web.archive.org/web/20070922121742/http://www.stanford.edu/class/humbio103/ParaSites2006/Onchocerciasis/Epidemiology.html |archive-date=2007-09-22 }} Over 85 million people live in endemic areas, and half of these reside in Nigeria. Another 120 million people are at risk for contracting the disease. The ''Onchocerca volvulus'' main habitat is fast flowing rivers, Onchocerciasis is more commonly found along the large rivers in northern and central regions of Africa, with cases decreasing with distance from the rivers.{{Citation needed|date=December 2022}} Multiple exposure to ''Simulium'' blackflies raise the number of adult worms and microfilariae that are present in the host.{{Citation needed|date=December 2022}} Risk of contracting Onchocerciasis for casual travelers is low, since it often takes several exposures, while travelers that stay for longer visits such as missionaries or long-term volunteers have a greater risk of contracting Onchocerciasis.{{Citation needed|date=December 2022}} Onchocerciasis was eliminated in the northern focus in [[Chiapas]], [[Mexico]],{{cite journal |author1=Peña Flores G. |author2=Richards F. | year = 2010 | title = Lack of ''Onchocerca volvulus'' transmission in the northern focus in Chiapas | journal = Am. J. Trop. Med. Hyg. | volume = 83 | issue = 1| pages = 15–20 | doi=10.4269/ajtmh.2010.09-0626|pmid=20595471 |pmc=2912569 |display-authors=etal}} and the focus in [[Oaxaca]], Mexico, where ''Onchocerca volvulus'' existed, was determined, after several years of treatment with [[ivermectin]], as free of the transmission of the [[parasite]].{{cite journal |author1=Peña Flores G. |author2=Richards F. |author3=Domínguez A. | year = 2010 | title = Interruption of transmission of ''Onchocerca volvulus'' in the Oaxaca focus | journal = Am. J. Trop. Med. Hyg. | volume = 83 | issue = 1| pages = 21–27 | doi=10.4269/ajtmh.2010.09-0544|pmc=2912570 | pmid=20595472}} In April 2013, Colombia became the first country to achieve elimination of Onchocerciasis, verified by the World Health Organization. In the following three years, Ecuador and Guatemala, along with Mexico have been verified to have eliminated Onchocerciasis, with the use of ivermectin.{{Cite web |title=Onchocerciasis (river blindness) |url=https://www.who.int/news-room/fact-sheets/detail/onchocerciasis |access-date=2022-11-21 |website=www.who.int |language=en}} [158] => [159] => Cities in Nigeria, Cameroon, Ethiopia, Uganda, and the Congo by far have had the largest amount of infected individuals. [160] => [161] => The efforts of CDTI (Community-Directed Treatment with Ivermectin) was conducted to study Onchocerciasis associations with epilepsy. The results do not go unnoticed as they were able to decrease the number of microfilariae (larvae) loads. This was able to decrease the number of blind people due to onchocerciasis dramatically. However, another issue that arises is the fact that onchocerciasis is able to cause epilepsy, most likely because the level of microfilariae load required to develop epilepsy is much lower than to develop blindness.{{Cite journal |last1=Colebunders |first1=Robert |last2=Nelson Siewe |first2=F.J. |last3=Hotterbeekx |first3=An |date=March 2018 |title=Onchocerciasis-Associated Epilepsy, an Additional Reason for Strengthening Onchocerciasis Elimination Programs |url=https://linkinghub.elsevier.com/retrieve/pii/S1471492217302830 |journal=Trends in Parasitology |language=en |volume=34 |issue=3 |pages=208–216 |doi=10.1016/j.pt.2017.11.009|pmid=29288080 }} [162] => [163] => According to a 2002 WHO report, onchocerciasis has not caused a single death, but its global burden is 987,000 [[disability adjusted life year]]s (DALYs). The severe [[pruritus]] alone accounts for 60% of the DALYs. Infection reduces the host's immunity and resistance to other diseases, which results in an estimated reduction in life expectancy of 13 years. In 2017, the Global Burden of Disease study said that an estimated 220 million people needed preventive chemotherapy for onchocerciasis. Of those infected, 14.6 million had skin disease and 1.15 million experienced vision loss.{{Cite web |title=Onchocerciasis (river blindness) |url=https://www.who.int/news-room/fact-sheets/detail/onchocerciasis |access-date=2022-12-13 |website=www.who.int |language=en}} [164] => [165] => Onchocerciasis is the second leading cause of blindness from infectious causes. Main disease symptoms, such as blindness and itching, contribute to disease burden by limiting the infected individuals ability to live and work. Individuals most at risk are those who live or work in areas where ''Simulium'' blackflies are most common, mostly near rivers and streams. Rural agricultural areas in sub-Saharan Africa see the most disease burden by blackfly bites.{{Cite web |date=2019-09-09 |title=CDC - Onchocerciasis - Epidemiology & Risk Factors |url=https://www.cdc.gov/parasites/onchocerciasis/epi.html |access-date=2022-12-13 |website=www.cdc.gov |language=en-us}} Onchocerciasis common to tropical environments, like that of sub-Saharan Africa, where more than 99% percent of infected individuals occupy the 31 countries. Onchocerciasis can be linked to impoverished remote areas, as residents who experience symptoms can no longer tend to land or navigate the area.{{cite journal | doi=10.11604/pamj.2020.35.107.16036 | title=Prevalence of onchocerciasis, attitudes and practices and the treatment coverage after 15 years of mass drug administration with ivermectin in the Tombel Health District, Cameroon | year=2020 | last1=Nyagang | first1=Sharon Mumah | last2=Cumber | first2=Samuel Nambile | last3=Cho | first3=Jerome Fru | last4=Keka | first4=Elsie Indah | last5=Nkfusai | first5=Claude Ngwayu | last6=Wepngong | first6=Emerson | last7=Tsoka-Gwegweni | first7=Joyce Mahlako | last8=Fokam | first8=Eric Bertrand | journal=Pan African Medical Journal | volume=35 | page=107 | pmid=32637005 | pmc=7321683 }} Areas with high infection rates may experience up to one-third of residents affected by onchocerciasis symptoms. The age group most impacted by the disease are individuals age 61+ years.{{Cite journal |last1=Nyagang |first1=Sharon Mumah |last2=Cumber |first2=Samuel Nambile |last3=Cho |first3=Jerome Fru |last4=Keka |first4=Elsie Indah |last5=Nkfusai |first5=Claude Ngwayu |last6=Wepngong |first6=Emerson |last7=Tsoka-Gwegweni |first7=Joyce Mahlako |last8=Fokam |first8=Eric Bertrand |date=2020-04-08 |title=Prevalence of onchocerciasis, attitudes and practices and the treatment coverage after 15 years of mass drug administration with ivermectin in the Tombel Health District, Cameroon |journal=The Pan African Medical Journal |volume=35 |page=107 |doi=10.11604/pamj.2020.35.107.16036 |issn=1937-8688 |pmc=7321683 |pmid=32637005}} [166] => [167] => ==History== [168] => Onchocerca originated in Africa and was exported to the Americas by the slave trade, as part of the [[Columbian exchange]] that introduced other old world diseases such as yellow fever into the New World. Findings of a phylogenetic study in the mid-90s are consistent with an introduction to the New World in this manner. DNA sequences of savannah and rainforest strains in Africa differ, while American strains are identical to savannah strains in western Africa.{{cite journal|last1=Zimmerman|first1=PA|last2=Katholi|first2=CR|last3=Wooten|first3=MC|last4=Lang-Unnasch|first4=N|last5=Unnasch|first5=TR|title=Recent evolutionary history of American Onchocerca volvulus, based on analysis of a tandemly repeated DNA sequence family.|journal=Molecular Biology and Evolution|date=May 1994|volume=11|issue=3|pages=384–92|pmid=7516998|doi=10.1093/oxfordjournals.molbev.a040114|doi-access=free}} The microfilarial parasite that causes the disease was first identified in 1874 by an Irish naval surgeon, John O'Neill, who was seeking to identify the cause of a common skin disease along the west coast of Africa, known as "craw-craw".{{cite journal|last1=O'Neill|first1=John|title=O'Neill J. On the presence of a filaria in craw-craw|journal=The Lancet|date=1875|pages=265–266|url=https://web.stanford.edu/class/humbio103/ParaSites2006/Onchocerciasis/filaria_original_description.pdf|doi=10.1016/s0140-6736(02)30941-3|volume=105|issue=2686|url-status=live|archive-url=https://web.archive.org/web/20160202041235/https://web.stanford.edu/class/humbio103/ParaSites2006/Onchocerciasis/filaria_original_description.pdf|archive-date=2016-02-02}} [[Rudolf Leuckart]], a German zoologist, later examined specimens of the same filarial worm sent from Africa by a German missionary doctor in 1890 and named the organism ''Filaria volvulus''.{{cite web|title=A Short History of Onchocerciasis|url=https://www.scribd.com/doc/268204602/A-Short-History-of-Onchocerciasis|access-date=18 October 2015|url-status=live|archive-url=https://web.archive.org/web/20160304071504/https://www.scribd.com/doc/268204602/A-Short-History-of-Onchocerciasis|archive-date=4 March 2016}} [169] => [170] => Rodolfo Robles and Rafael Pacheco in Guatemala first mentioned the ocular form of the disease in the Americas about 1915. They described a tropical worm infection with adult Onchocerca that included inflammation of the skin, especially the face ('erisipela de la costa'), and eyes.{{cite journal|last1=Robles|first1=Roberto|title=Enfermedad nueva en Guatemala|journal=La Juventud Médica|date=1917}} The disease, commonly called the "filarial blinding disease", and later referred to as "Robles disease", was common among coffee plantation workers. Manifestations included subcutaneous nodules, anterior eye lesions, and dermatitis. Robles sent specimens to [[Émile Brumpt]], a French parasitologist, who named it ''O. caecutiens'' in 1919, indicating the parasite caused blindness (Latin "caecus" meaning blind).{{cite book|last1=Strong|first1=Richard|title=Stitt's Diagnosis, prevention and treatment of tropical diseases|date=1942|publisher=The Blakiston}} The disease was also reported as being common in Mexico.{{cite book|last1=Manson-Bahr|first1=Philip H|title=Tropical diseases; a manual of the diseases of warm climates [Internet]|date=1943|publisher=Williams & Wilkins Co|edition=11th}} By the early 1920s, it was generally agreed that the filaria in Africa and Central America were morphologically indistinguishable and the same as that described by O'Neill 50 years earlier.{{citation needed|date=January 2021}} [171] => [172] => Robles hypothesized that the vector of the disease was the day-biting black fly, ''Simulium''. Scottish physician Donald Blacklock of the [[Liverpool School of Tropical Medicine]] confirmed this mode of transmission in studies in Sierra Leone. Blacklock's experiments included the re-infection of Simulium flies exposed to portions of the skin of infected subjects on which nodules were present, which led to elucidation of the life cycle of the Onchocerca parasite.{{cite journal|last1=Blacklock|first1=DB|title=The Insect Transmission of Onchocerca Volvulus (Leuckart, 1893): The Cause of Worm Nodules in Man in Africa|journal=British Medical Journal|date=22 January 1927|volume=1|issue=3446|pages=129–33|pmid=20772951|doi=10.1136/bmj.1.3446.129|pmc=2453973}} Blacklock and others could find no evidence of eye disease in Africa. [[Jean Hissette]], a Belgian ophthalmologist, discovered in 1930 that the organism was the cause of a "river blindness" in the Belgian Congo.{{cite journal|last1=Kluxen|first1=G|last2=Hoerauf|first2=A|title=The significance of some observations on African ocular onchocerciasis described by Jean Hissette (1888-1965)|journal=Bull Soc Belge Ophtalmol|date=2008|volume=307|pages=53–8}} Some of the patients reported seeing tangled threads or worms in their vision, which were microfilariae moving freely in the aqueous humor of the anterior chamber of the eye.{{cite book|last1=Hisette|first1=Jean|title=Mémoire sur l'Onchocerca volvulus Leuckart et ses manifestations oculaires au Congo belge|date=1932|pages=433–529}} Blacklock and Strong had thought the African worm did not affect the eyes, but Hissette reported that 50% of patients with onchocerciasis near the Sankuru river in the Belgian Congo had eye disease and 20% were blind. Hisette Isolated the microfilariae from an enucleated eye and described the typical chorioretinal scarring, later called the "Hissette-Ridley fundus" after another ophthalmologist, [[Harold Ridley (ophthalmologist)|Harold Ridley]], who also made extensive observations on onchocerciasis patients in north west Ghana, publishing his findings in 1945.{{cite journal|last1=Ridley|first1=Harold|title=OCULAR ONCHOCERCIASIS Including an Investigation in the Gold Coast|journal=Br J Ophthalmol|date=1945|volume=29|issue=Suppl|pages=3–58|doi=10.1136/bjo.29.suppl.3|pmid=18170175|pmc=513929}} Ridley first postulated that the disease was brought by the slave trade. The international scientific community was initially skeptical of Hisette's findings, but they were confirmed by the Harvard African Expedition of 1934, led by [[Richard P. Strong]], an American physician of tropical medicine.{{cite web|last1=Kluxen|first1=G|title=Harvard African Expedition [Internet]|url=http://collections.countway.harvard.edu/onview/items/show/6157|access-date=18 October 2015|url-status=live|archive-url=https://web.archive.org/web/20151222160904/http://collections.countway.harvard.edu/onview/items/show/6157|archive-date=22 December 2015}} [173] => [174] => ==Society and culture== [175] => Since 1987, ivermectin has been provided free of charge for use in humans by [[Merck & Co.|Merck]] through the Mectizan donation program (MDP). The MDP works together with ministries of health and nongovernmental development organisations, such as the [[World Health Organization]], to provide free ivermectin to those who need it in [[endemic (epidemiology)|endemic]] areas.{{cite journal |journal=[[Trop Med Int Health]] |date=May 2008 |volume=13 |issue=5 |pages=689–96 |title=Operational lessons from 20 years of the Mectizan Donation Program for the control of onchocerciasis|vauthors=Thylefors B, Alleman MM, Twum-Danso NA |pmid=18419585 |doi=10.1111/j.1365-3156.2008.02049.x |doi-access=free }} Due to the joint efforts of NGOs and WHO, onchocerciasis is no longer an obstacle in socio-economic development.{{Cite journal |website=World Health Organization |date=2002 |title=Onchocerciasis control in Niger: achievements and prospects after OCP |hdl=10665/342987 |hdl-access=free |url=https://apps.who.int/iris/handle/10665/342987 |language=en | vauthors = Organization WH }} [176] => [177] => In 2015 [[William C. Campbell (scientist)|William C. Campbell]] and [[Satoshi Ōmura]] were co-awarded half of that year's [[Nobel Prize in Physiology or Medicine]] for the discovery of the [[avermectin]] family of compounds, the forerunner of ivermectin. The latter has come to decrease the occurrence of lymphatic filariasis and onchocerciasis.{{citation |url=https://www.nobelprize.org/nobel_prizes/medicine/laureates/2015/advanced-medicineprize2015.pdf |title=Avermectin and Artemisinin - Revolutionary Therapies against Parasitic Diseases |author1=Jan Andersson |author2=Hans Forssberg |author3=Juleen R. Zierath |publisher=The Nobel Assembly at Karolinska Institutet |date=5 October 2015 |access-date=5 October 2015 |url-status=live |archive-url=https://web.archive.org/web/20151005235033/http://www.nobelprize.org/nobel_prizes/medicine/laureates/2015/advanced-medicineprize2015.pdf |archive-date=5 October 2015 }} [178] => [179] => Uganda's government, working with the [[Carter Center]] river blindness program since 1996, switched strategies for distribution of Mectizan. The male-dominated volunteer distribution system had failed to take advantage of traditional kinship structures and roles. In 2014, the program switched from village health teams to community distributors, primarily selecting women with the goal of assuring that everyone in the circle of their family and friends received river blindness information and [[Mectizan]].Kinship Powerful in River Blindness Fight. ''Carter Center Update'', The Carter Center, Atlanta, Georgia. Summer, 2016. pp. 4-5. [180] => [181] => In 2021, Nigeria had the greatest prevalence of onchocerciasis infections globally, and attributed the infection to 30.2% of blindness cases in the country. A study from western Nigeria found that residents believed that the parasitic effects of the disease was necessary to stimulate fertility, and that the disease was thought to be carried by all residents.{{Cite journal |last=Ajaegbu |first=Okechukwu Odinaka |date=March 2021 |title=Socio-cultural factors in onchocerciasis control: a study of rural Southeast Nigeria |journal=Journal of Parasitic Diseases |language=en |volume=45 |issue=1 |pages=10–16 |doi=10.1007/s12639-020-01269-7 |issn=0971-7196 |pmc=7921230 |pmid=33746381}} [182] => [183] => == Research == [184] => Animal models for the disease are somewhat limited, as the parasite only lives in primates, but there are close parallels. ''Litomosoides sigmodontis '', which will naturally infect [[cotton rat]]s, has been found to fully develop in [[BALB/c]] mice. ''[[Onchocerca ochengi]]'', the closest relative of ''O. volvulus'', lives in intradermal cavities in cattle, and is also spread by black flies. Both systems are useful, but not exact, animal models.{{cite journal |vauthors=Allen JE, Adjei O, Bain O, Hoerauf A, Hoffmann WH, Makepeace BL, Schulz-Key H, Tanya VN, Trees AJ, Wanji S, Taylor DW |title=Of Mice, Cattle, and Humans: The Immunology and Treatment of River Blindness |journal=[[PLoS Negl Trop Dis]] |volume=2 |issue=4 |date=April 2008 |pmid=18446236 |pmc=2323618 |doi=10.1371/journal.pntd.0000217 |pages=e217 |editor1-last=Lustigman |editor1-first=Sara |doi-access=free}} [185] => [186] => A study of 2501 people in [[Ghana]] showed the prevalence rate doubled between 2000 and 2005 despite treatment, suggesting the parasite is developing resistance to the drug.{{cite news |url=http://news.bbc.co.uk/2/hi/health/6753003.stm |publisher=BBC News |title=River blindness resistance fears |access-date=2007-06-15 |date=2007-06-14 |url-status=live |archive-url=https://web.archive.org/web/20070808233457/http://news.bbc.co.uk/2/hi/health/6753003.stm |archive-date=2007-08-08 }}{{cite journal |vauthors=Osei-Atweneboana MY, Eng JK, Boakye DA, Gyapong JO, Prichard RK |s2cid=30650856 |title=Prevalence and intensity of Onchocerca volvulus infection and efficacy of ivermectin in endemic communities in Ghana: a two-phase epidemiological study |journal=Lancet |volume=369 |issue=9578 |pages=2021–9 |date=June 2007 |pmid=17574093|doi=10.1016/S0140-6736(07)60942-8 }} A clinical trial of another anti-parasitic agent, [[moxidectin]] (manufactured by [[Wyeth]]), began on July 1, 2009 ([http://clinicaltrials.gov/ct2/show/NCT00790998 NCT00790998]).{{Cite journal |last=Lancet |first=The |date=2009-07-11 |title=Fighting river blindness and other ills |url=https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(09)61262-9/fulltext |journal=The Lancet |language=English |volume=374 |issue=9684 |page=91 |doi=10.1016/S0140-6736(09)61262-9 |issn=0140-6736 |pmid=19595328|s2cid=13401341 }} [187] => [188] => A [[Cochrane (organisation)|Cochrane review]] compared outcomes of people treated with ivermectin alone versus doxycycline plus ivermectin. While there were no differences in most vision-related outcomes between the two treatments, there was low quality evidence suggesting treatment with doxycycline plus ivermectin showed improvement in [[uveitis|iridocyclitis]] and punctate keratitis, over those treated with ivermectin alone.{{cite journal |vauthors=Abegunde AT, Ahuja RM, Okafor NJ |title= Doxycycline plus ivermectin versus ivermectin alone for treatment of patients with onchocerciasis |journal=Cochrane Database Syst Rev |volume=1 |issue= 1 |pages= CD011146 |date=2016 |pmid= 26771164 |doi= 10.1002/14651858.CD011146.pub2|pmc=5029467 }} [189] => [190] => In 2017, WHO set up the Onchocerciasis Technical Advisory Subgroup (OTS) to further research and establish areas that require drug administration. The OTS also identifies co-endemic areas with lymphatic filariasis to properly treat Onchocerciasis and lymphatic filariasis.{{citation needed|date=March 2023}} [191] => [192] => WHO priorities research to achieve elimination of onchocerciasis. Research approaches include: improving outreach efforts to marginalized populations, expanding mapping of endemic areas of onchocerciasis, improve and standardize information on mass drug administration, develop diagnostic approaches, surveillance strategies, and therapeutic approaches.{{citation needed|date=March 2023}} [193] => [194] => ==See also== [195] => {{portal|Medicine}} [196] => * [[Carter Center]] River Blindness Program [197] => * [[List of parasites (human)]] [198] => * [[Neglected tropical diseases]] [199] => * [[Rodolfo Robles]] [200] => * [[United Front Against Riverblindness]] [201] => * [[Harold Ridley (ophthalmologist)]] [202] => [203] => ==References== [204] => {{Reflist}} [205] => [206] => ==External links== [207] => {{portal bar|Medicine}} [208] => * [https://web.archive.org/web/20131212092614/http://www.dpd.cdc.gov/dpdx/HTML/Filariasis.htm CDC Parasites of public health concern] [209] => {{Medical condition classification and resources [210] => | DiseasesDB = 9218 [211] => | ICD10 = {{ICD10|B|73||b|65}} [212] => | ICD9 = {{ICD9|125.3}} [213] => | ICDO = [214] => | OMIM = [215] => | MedlinePlus = [216] => | eMedicineSubj = med [217] => | eMedicineTopic = 1667 [218] => | eMedicine_mult = {{eMedicine2|oph|709}} [219] => | MeshID = D009855 [220] => }} [221] => {{Wiktionary}} [222] => {{Helminthiases}} [223] => {{Eye pathology}} [224] => {{Diseases of poverty}} [225] => {{Eradication of infectious disease}} [226] => {{Authority control}} [227] => [228] => [[Category:Spirurida]] [229] => [[Category:Tropical diseases]] [230] => [[Category:Helminthiases]] [231] => [[Category:Infectious diseases with eradication efforts]] [232] => [[Category:Parasitic infestations, stings, and bites of the skin]] [233] => [[Category:Wikipedia medicine articles ready to translate]] [234] => [[Category:Wikipedia infectious disease articles ready to translate]] [] => )
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Onchocerciasis

Onchocerciasis, also known as river blindness, is a disease caused by infection with the parasitic worm Onchocerca volvulus. Symptoms include severe itching, bumps under the skin, and blindness.

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