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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
The existence of Mansonella ozzardi in the study area22 means that particular care must be taken when identifying microfilariae. Moraes et al.25 have suggested that the results of at least one study of onchocerciasis in Brazil have been biased by the unsuspected presence of M. ozzardi microfilariae in skin snips. By an examination of blood samples we have found that mansonelliasis is uncommon in our study area, and a mixed infection with O. volvulus was found in only a single individual.22 Nevertheless, this is an important point which must be considered in all work in the area, especially in transmission studies. Mansonelliasis is known to be endemic to the northwest of the present study area, and it is hoped to study the relationship between the two diseases in the region of overlap. As yet, we have little information about filarial reservoirs in animals in the Sierra Parima, which obviously are of great interest in investigations of a people who exist to a large extent by hunting. Our future plans include a search for such reservoirs and an extension of the study area to delimit the size of the endemic area of onchocerciasis in the Venezuelan territory of Amazonas and the scale of the problem in the indigenous population.
Diagnosing Parasitic Infections
Published in Firza Alexander Gronthoud, Practical Clinical Microbiology and Infectious Diseases, 2020
The microscopic examination of thick and thin peripheral blood smears stained with Giemsa or other appropriate stains is used for detection and identification of Plasmodium, Babesia and Trypanosoma species and of the filarial nematodes species (i.e. Brugia, Mansonella and Wuchereria).
Albendazole
Published in M. Lindsay Grayson, Sara E. Cosgrove, Suzanne M. Crowe, M. Lindsay Grayson, William Hope, James S. McCarthy, John Mills, Johan W. Mouton, David L. Paterson, Kucers’ The Use of Antibiotics, 2017
Infections with Mansonella perstans are generally asymptomatic, but are encountered in Africa and South America as a chance finding. Although data are limited, albendazole in a dose of 400 mg twice daily for 7 days appears to show efficacy against the adult worms but not against microfilariae (Sanguigni et al., 1990; Van den Enden et al., 1992; Lipani et al., 1997; Duong et al., 1998). A comparative study of albendazole, ivermectin, and the combination suggested that neither drug alone had any effect on microfilaria, but the combination produced a reduction (Asio et al., 2009a; Asio et al., 2009b). Thus, long-term follow-up, as with all filarial diseases, is needed to document an effect (Horton, 1998).
An unexpected peripheral blood finding: microfilaria
Published in Baylor University Medical Center Proceedings, 2020
John R. Krause, Meleissa Hutcheson, Rebecca Ardoin
The roundworm in our patient was Mansonella perstans, one of the three filarial species in the genus Mansonella (the other two being M. ozzardi and M. streptocerca), which are included in the category of serous cavity filariasis. In mammalian hosts, adult Mansonella worms are located in connective tissues or peritoneal, pleural, or pericardial cavities.4 Microfilaria of M. perstans will circulate in the blood and are approximately 190 to 200 μm in length × 4 μm (slightly smaller than the diameter of a red blood cell). The microfilariae are unsheathed; the tail tapers to a bluntly rounded end and nuclei extend to the end of the tail.5 Because the microfilariae are small, they can be overlooked in blood films. In the blood, they may be distinguished from other sympatric microfilariae including Loa loa or Wuchereria bancrofti, which are longer and sheathed and have larger terminal nuclei.5