The Challenge of Parasite Control
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2023
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.
Flies (Biting)
Gail Miriam Moraru, Jerome Goddard in The Goddard Guide to Arthropods of Medical Importance, Seventh Edition, 2019
Black flies (also called buffalo gnats, turkey gnats, and Kolumbtz flies) are small, humpbacked flies that are important as vectors of disease and as nuisance pests.1,2 In the tropics, black flies are vectors of the parasite Onchocerca volvulus, which causes a chronic nonfatal disease with fibrous nodules in subcutaneous tissues and sometimes visual disturbances and blindness (river blindness). The World Health Organization estimates that about 17 million people have onchocerciasis in Africa and Latin America (Figure 19.1).3 Since 1987 (and still ongoing), onchocerciasis control has been greatly aided by mass drug administration of ivermectin, which has been a gold standard antiparasitic drug. More recently, a structurally similar new drug, moxidectin, has shown even more efficacy. There is a goal of total elimination of onchocerciasis from most of Africa by 2025.4 Interestingly, an autoimmune response to infection with Onchocerca filarial worms has been reported, leading to a form of epilepsy and “nodding syndrome” in children in parts of Africa.5
Wuchereria bancrofti
Peter M. Lydyard, Michael F. Cole, John Holton, William L. Irving, Nino Porakishvili, Pradhib Venkatesan, Katherine N. Ward in Case Studies in Infectious Disease, 2010
There is now a collaboration of public and private parties to eliminate lymphatic filariasis. This is called the Global Alliance to Eliminate Lymphatic Filariasis (GAELF). The mainstay of elimination efforts is periodic mass chemotherapy. Entire, defined populations are given chemotherapy irrespective of whether they are microfilaremic or amicrofilaremic. This is simpler than testing every individual by blood films. Repeated administration at annual intervals is intended to reduce levels of microfilaremia so that it is less likely for mosquitoes to transmit infection. A high level of population coverage is required for this to work. Administration must also be repeated for a number of years. How many years depends on the efficacy of the drugs used in killing adult worms, but should be at least 4–6 years. Traditionally DEC has been the backbone of mass chemotherapy, to which now albendazole may be added. In areas where onchocerciasis is present DEC causes severe reactions in individuals co-infected with Onchocerca volvulus. Therefore in these areas ivermectin is used in preference to DEC.
The search for better treatment strategies for mansonellosis: an expert perspective
Published in Expert Opinion on Pharmacotherapy, 2023
Marcelo U. Ferreira, James Lee Crainey, Federico G. Gobbi
Microfilariae of M. ozzardi and M. perstans circulate in the peripheral blood, without showing clear evidence of periodicity, but are occasionally found in the skin [18–20]. Diagnosis is usually done with light microscopy, with concentration methods being often applied to blood samples [1,2]. Mansonella streptocerca microfilariae are found in the skin and subcutaneous tissues and typically detected in skin-snip biopsies. However, Mansonella parasites in the skin cannot be reliably identified using light microscopy because M. perstans and Onchocerca volvulus cannot be morphologically discriminated from one another and because both are commonly confused with M. ozzardi, M. streptocerca, and Loa loa [18–21]. Polymerase chain reaction (PCR) [22–27] and the field-deployable loop mediated isothermal amplification (LAMP) [28,29] are molecular techniques that can improve diagnostic sensitivity and specificity and help to distinguish between morphologically similar parasites. Quantitative PCR can estimate the peripheral-blood density of microfilariae [10] and identify co-infections [30] and could prove useful for the assessment of microfilaricide drug responses in clinical trials. The recent detection of O. volvulus metabolites in the urine of infected individuals [31] suggests that noninvasive diagnostics could be developed for filarial parasite infections including mansonellosis. However, it is presently impossible to diagnose any type of filarial infection using a urine sample.
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
Kelly Johnson-Arbor
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.
Related Knowledge Centers
- Angiogenesis
- Cuticle
- Trachoma
- Visual Impairment
- Circulatory System
- Onchocerciasis
- Neglected Tropical Diseases
- Host
- Simulium
- Filariasis