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The Challenge of Parasite Control
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
Similarly, the transmission of filarial worms has been controlled by mass use of ivermectin. Adult worms in the definitive mammalian host are usually not killed. Both the infective L3 larvae, transmitted to humans through the bite of an arthropod vector, and the microfilariae produced by the adult worms are vulnerable. Consequently, if used prophylactically, ivermectin can render humans and other mammalian hosts refractory to infection. Because microfilariae are killed, arthropods in search of a blood meal on an infected mammalian host are unlikely to become infected if their host is taking ivermectin. In many cases of filariasis, of course, such as the elephantiasis caused by Wuchereria bancrofti, ivermectin will not assist the infected person, as pathology is the result of trauma caused by adult worms. A patient infected with Onchocerca volvulus, on the other hand, may benefit from ivermectin because circulating microfilariae cause the most serious symptoms of infection, including blindness. Box 9.2 describes a combination therapy that may include ivermectin, which improves treatment of canine heart-worm caused by the filarial parasite Dirofilaria immitis.
Corneal Disorders
Published in Ching-Yu Cheng, Tien Yin Wong, Ophthalmic Epidemiology, 2022
Darren S. J. Ting, Rashmi Deshmukh, Daniel S. W. Ting, Marcus Ang
Onchocerciasis, also known as “river blindness,” is caused by the filarial worm Onchocerca volvulus, which is transmitted by the bites of blackflies of Simulum spp. After trachoma, it is the second leading cause of corneal blindness in the world.51 Approximately 37 million people are estimated to be infected worldwide, and 300,000 of them are permanently blind.52
Introduction to Onchocerciasis
Published in Max J. Miller, E. J. Love, Parasitic Diseases: Treatment and Control, 2020
Further progress has been made, especially in the search for new chemotherapeutic substances, with the discovery of the efficacy of ivermectin on Onchocerca volvulus microfilariae, and in the development of immunologic studies in onchocerciasis. However, the present section will mainly focus on the socioeconomic factors in onchocerciasis, the methods used for vector control in West Africa and their results, and the assessment of the situation in the recently discovered South American foci of the disease. Each section has been prepared by the most competent scientist in the relevant field. It summarizes the state-of-the-art of the scientific knowledge in each specialized area.
Aqueous humor cytokines and cellular profiles in pediatric ocular granulomas caused by theTrematode Fluke Procerovum sp
Published in Ocular Immunology and Inflammation, 2022
Rathinam SR, Lalan Kumar Arya, R. Siva Ganesa Karthikeyan, Sagnik Sen
Ocular parasitosis are diseases caused by parasites, including protozoa, nematodes, trematodes, and cestodes.1,2 We have previously reported a large series of trematode granulomas in the eyes of south Indian children who were exposed to village pond or river water.3–5 After swimming in the village ponds, these children developed red-eye and itching and sometimes itching all over the body. Transient dermatitis disappeared on its own; however, some of them developed chronic eye inflammation leaving a granuloma either in the subconjunctival space or in the anterior chamber (Figure 1(a,b)). Histopathological study on subconjunctival nodules showed necrotizing granuloma, displaying the teguments of trematodes.3,4 On molecular analysis by DNA sequencing, the pathogen was found to be trematode Procerovum spp.6,7 Although parasite species belong to a large number of genera, only those that are responsible for great public health risks, such as Onchocerca volvulus (causing river blindness), Schistosoma mansoni (causing schistosomiasis and hepatic fibrosis), and Toxoplasma spp. (causing toxoplasmosis), have been the main focus of immunopathological research.1,2 Other rare parasites are under-reported and not extensively studied.
Ivermectin: a mini-review
Published in Clinical Toxicology, 2022
The avermectins are commonly used antiparasitic agents with activity against arthropods and nematodes [1]. Derived from Streptomyces bacteria found naturally in soil, the avermectin class of drugs, including abamectin, ivermectin, eprinomectin, doramectin, and selamectin, are structurally similar macrocyclic lactone compounds differentiated by the presence of A and B components [1]. Ivermectin is composed of avermectin B1 components and was initially marketed for animal use in 1981. In 1987, it was registered for human use as a treatment for onchocerciasis (river blindness) [1,2]. Currently, ivermectin is used in humans as a prescription medication for Strongyloides stercoralis, Onchocerca volvulus, and Ascariasis infections as well as lice, scabies, and rosacea.
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].