Further Studies on the Development of Onchocerca spp. (Nematoda: Filarioidea) in Nearctic Black Flies (Diptera: Simuliidae)

J. B. LokDepartment of Pathobiology, The School of Veterinary Medicine H1, University of Pennsylvania, Philadelphia, Pennsylvania 19104

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E. W. CuppDepartment of Entomology, Cornell University, Ithaca, New York 14853

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M. J. BernardoDepartment of Entomology, Cornell University, Ithaca, New York 14853

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R. J. PollackDepartment of Pathobiology, The School of Veterinary Medicine H1, University of Pennsylvania, Philadelphia, Pennsylvania 19104

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Of three species of Nearctic black flies tested, Simulium pictipes Hagen proved the most efficient laboratory vector of the bovine parasite Onchocerca lienalis. Among flies inoculated intrathoracically with 40 microfilariae, numbers of 3rd-stage larvae per fly were 7.63 for S. pictipes, 7.54 for S. vittatum Zetterstedt, and 0.83 for S. decorum Walker. S. pictipes survived the longest under laboratory conditions, with 83.3% of the females remaining alive 10 days after inoculation with 40 microfilariae of O. lienalis. Using an artificial membrane feeding system, S. pictipes could be routinely infected with O. lienalis by mouth. This black fly was also susceptible to infection with the Guatemalan strain of O. volvulus. Among flies injected with 10 microfilariae the rate of infection with 3rd-stage larvae was 93%, with a mean of three 3rd-stage larvae per fly. Successful techniques for the large-scale recovery and cryopreservation of 3rd-stage larvae of O. lienalis were also developed. A motility rate of 92.7% was observed in larvae cryopreserved within vector black flies.

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