Section 24
Chapter 23,844

The development of Onchocerca volvulus in Simulium damnosum

Blacklock, D.B.

Annals of Tropical Medicine and Parasitology 20(1): 1-48


ISSN/ISBN: 1364-8594
DOI: 10.1080/00034983.1926.11684476
Accession: 023843177

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A list of insects that have been suspected of transmitting the larvae of O. volvulus and a review of literature are given. Examination of 123 African natives and 441 sections of nodulated skin from 4 regions of the body (scapula, loin, thigh, and ankle) was made. Of 93 natives, 45 were positive in 1 or more of the 4 regions; larvae were found more commonly in the waist region. S. damnosum is common along streams and in such localities natives usually are bitten. A total of 780 flies were examined for gut infestation; 2.6% were positive. The larvae in the gut were more active than those from the native's skin. The thoraxes of 1,320 flies were examined and more than 1% yielded larvae in different stages. The examinations of the heads of 1,140 flies were negative. Out of 10 flies which fed on the loins of a boy, 1 showed developmental stages of O. volvulus. Out of a larger number of flies which fed on any part of the body, 22 were examined and 32% were infected in the thoraxes. Of 22 flies, which bit a band of nodulated skin 4 inches wide, 82% showed infection in the thoraxes. Larvae obtained by aspiration of nodules in the skin were of 2 types the large forms were 295-358[mu] long and 6-9[mu] broad; the small forms were 221-287[mu] long by 5-7[mu] broad. The larvae from the gut of the fly measured 200-334[mu] in length by 5-8[mu] in breadth. The movements of the larvae in the human and ecdysis in S. damnosum are discussed.

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