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The Parasitic Protozoa and Helminth Worms
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Human filariasis is caused by infections with several species of nematode worms, the females of which produce larvae that are released in the body of the host, often in the blood, until taken up by an arthropod vector. The most important manifestations are lymphatic filariasis and onchocerciasis. In lymphatic filariasis, caused by Wuchereria bancrofti, Brugia malayi, and Brugia timori and transmitted by mosquitoes, the adults live in the lymphatics, and the disease is characterized by lymphatic blockage resulting in swelling of the limbs, scrotum and other parts of the body causing the condition known as elephantiasis. In onchocerciasis, caused by Onchocerca volvulus and transmitted by blackflies belonging to the genus Simulium, the adults live in skin nodules, and the disease is characterized by blindness.
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
Biting insect and tick allergens
Published in Richard F. Lockey, Dennis K. Ledford, Allergens and Allergen Immunotherapy, 2020
Donald R. Hoffman, Jennifer E. Fergeson
There are over 18,000 species of Simulium, blackflies, identified worldwide. This species is also referred to as the bloodsucking blackfly due to the large amount of bleeding that can occur at the site of the bite. Studies on the saliva of blackflies are limited. Anticoagulation factors against thrombin in blackfly saliva may account for this abnormality in hemostasis [30,31]. Cupp et al. isolated and cloned a major protein of molecular weight 15.35 kDa with strong vasodilator activity manifested by rapid and persistent induction of erythema [31]. The enzyme apyrase is found in blackfly salivary gland secretions. Wirtz demonstrated easily measurable amounts of histamine, putrescine, spermine, N-monoacetyl-spermine and spermidine, as well as the presence of proteins with esterase activity in salivary gland secretion [32]. Almost all reactions to blackfly bites are not IgE mediated, and the dermatologic reactions are classified into six forms by Farkas [33]. These include edematous, erythematous-edematous, erysipeloid, inflammatory-indurative, hemorrhagic (plaques, nodules, or vesicles), and allergic.
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
Onchocerca ochengi is the most notable of these, sharing many key characteristics with O. volvulus in terms of its genome, biology, lifecycle and transmission including its arthropod vector (Simulium damnosum s.l.), the sedentary nodule-forming nature of adult females, microfilaridermia and presence of the endosymbiont Wolbachia [76–78]. Indeed, these two parasites are so similar it is hypothesized that O. volvulus evolved either directly from O. ochengi or another common cattle-infecting ancestor, jumping hosts in a speciation event coinciding with the recent introduction (in an evolutionary context) of domestic cattle to the African continent [79]. This theory is supported by numerous phylogenetic studies showing the close relationship of these two sister species [80,81]. Importantly in the context of vaccine development, this relationship also extends to antigenic homology [82,83]. Accordingly, a zooprophylactic effect against infection with O. volvulus has been inferred epidemiologically in humans that results from natural exposure to O. ochengi in co-endemic regions [84].
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