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Black Flies
Published in Jerome Goddard, Public Health Entomology, 2022
In the tropics, black flies are vectors of the parasite Onchocerca volvulus, which causes a chronic nonfatal disease with fibrous nodules in subcutaneous tissues (onchocerciasis) and sometimes visual disturbances and blindness (river blindness) (Figure 15.3). The World Health Organization estimates that about 17 million people have onchocerciasis in Africa and Latin America.7
Infestations, insect bites, and stings
Published in Rashmi Sarkar, Anupam Das, Sumit Sethi, Concise Dermatology, 2021
This is caused by the parasite Onchocerca volvulus and is found in equatorial West Africa. The disorder is spread by the bite of the blackfly Simulium damnosum, which is found around rivers. The larval forms, known as microfilariae, are injected into the skin by the blackfly and develop after some years into adult onchocercal worms. These are extremely long (up to 1 m) but very thin (1–2 mm in diameter) creatures that live curled up in the subcutis surrounded by a palpable, host-supplied fibrous capsule. The adult worm procreates by producing enormous numbers of microfilariae, which invade the subcutis of large areas of truncal skin.
Onchocerciasis in the Sierra Parima and Upper Orinoco Regions, Federal Territory of Amazonas, Venezuela *
Published in Max J. Miller, E. J. Love, Parasitic Diseases: Treatment and Control, 2020
Onchocerciasis was first identified in Venezuela in 1949, when adult Onchocerca volvulus were found in a nodule removed from a 7-year old girl.1 In the succeeding decade the disease was found to be distributed in two large foci in the eastern and central parts of the coastal mountain range (Figure 1)2-4 and concentrated in premontane forest areas between 200 and 1300 m above sea level with a seasonal rainfall of 500 to 2200 mm per annum.5 Fortunately, transmission of onchocerciasis in these areas by the principal vector, Simulium metallicum,6 appears to be at a low level, with only 2.5% of the population being infected before a campaign of control was started.5 Dermal lesions and lymphatic involvement were absent, and ocular lesions were initially found in 30% of the infected population, half with punctate keratitis and none with sclerosing keratitis. Nodules were present in 23% of the cases and were concentrated around the pelvic region. An active campaign of control since 1962, based on diagnosis by the Mazzotti test, confirmation by skin biopsy, and follow-up treatment with suramin, has been effective, and the infection rate was halved in the first 10 years of the campaign.5
Development of a recombinant vaccine against human onchocerciasis
Published in Expert Review of Vaccines, 2021
David Abraham, John Graham-Brown, Darrick Carter, Sean A. Gray, Jessica A. Hess, Benjamin L. Makepeace, Sara Lustigman
Human onchocerciasis (‘river blindness’), caused by the filarial nematode parasite Onchocerca volvulus, is a major cause of infectious blindness, skin disease, and chronic disability. It infects many millions worldwide with 99% of the cases sustained in 31 countries of Sub-Saharan Africa- resulting in widespread vision impairment and blindness. Current estimates put 120 million people at risk [1,2]. The Global Burden of Disease Study estimated in 2017 that there were 20.9 million people infected worldwide, of which 14.6 million had skin disease and 1.15 million had vision loss [3,4] (Figure 1). Importantly, it has become apparent in recent years that onchocerciasis-associated epilepsy (OAE) is also an important public health problem caused by onchocerciasis. In a recent door-to-door survey in Mvolo, an onchocerciasis endemic region in South Sudan, the prevalence of epilepsy in this population was higher (5.1%) than blindness (2.8%) [5].
Infectious diseases among Ethiopian immigrants in Israel: a descriptive literature review
Published in Pathogens and Global Health, 2021
Yulia Treister-Goltzman, Ali Alhoashle, Roni Peleg
Onchocerciasis is a systemic disease caused by the filarial parasite Onchocerca volvulus. It is endemic in Africa and South America and transmitted by the Simulium blackfly. Most EI, especially those who arrived in Israel up to 1991, came from Gondar province in western Ethiopia where the prevalence of Onchocerciasis is not very high. The first reports on this disease among EI appeared in the 1990s [67]. A large proportion of EI who arrived after 1992 came from the Kuwara highland in northwest Ethiopia, which is considered a very endemic area where the prevalence of Onchocerciasis reaches 84%. Israeli investigators screened a large group of EI from this endemic area to identify Onchocerciasis [68]. They found a high rate of skin involvement, particularly in the lower extremities. In over 40% of the patients who were suspected of having eye damage based on their complaints, there was corneal pathology including scars, infiltrates, and even microfilariae. The disease caused uveitis, keratitis, and even secondary glaucoma [68,69]. The disease was diagnosed by a skin snip test or serological testing. Prior to that study [68] none of the infected EI received this diagnosis, due to a low level of awareness of the disease by physicians, nonspecific and mild clinical findings, and lack of training in the conduct of the skin snip test. Blindness is one of the most severe results of this disease, so it was very important to raise the level of awareness and knowledge of physicians on Ochocerciasis in EI, especially from the Kuwara region.
Seroprevalence of onchocerciasis in Ogun State, Nigeria after ten years of mass drug administration with ivermectin
Published in Southern African Journal of Infectious Diseases, 2018
OA Surakat, SO Sam-Wobo, T De Los Santos, D Faulx, A Golden, K Ademolu, L Yokobe, MA Adeleke, SO Bankole, ON Adekunle, WA Abimbola, CF Mafiana
Onchocerciasis is an irreversible blinding disease associated with infection with the parasite Onchocerca volvulus, which is transmitted by insect vectors of the Simulium species. It is distributed mostly along communities with fast-flowing rivers with rocky vegetation, which serves as suitable breeding ecology for the vectors.1–3 The disease is of global concern as it is found in 31 African countries, Yemen and South America with confirmed elimination in Mexico, Ecuador, Guatemala and Colombia.4–8 Nigeria ranks among those countries with the highest burden of the disease in the world, accounting for about a third of the global prevalence.9–12