Factors influencing the ingestion of Onchocerca cervicalis microfilariae by Culicoides variipennis (Diptera: Ceratopogonidae).

Culicoides variipennis were fed under controlled conditions on two ponies that exhibited seasonal changes in Onchocerca cervicalis microfilarial (mf) skin density and skin distribution. The seasonal changes did not radically affect mf ingestion. Flies were fed on the umbilicus of infected ponies by two methods: individual feeding in consecutive order at the same site, or by mass feeding. Linear regression analysis indicated that ingestion of microfilaria was independent of feeding time and engorged weight. In the individual feeding data, there was a trend toward an increased ingestion of mf as the feeding time increased. Mass feeding trials suggest early feedings by C. variipennis may influence mf ingestion rates of flies that feed on subsequent days. Of the 1,104 flies feeding on both ponies over a 2-year period, 220 (20%) ingested mf and 99 (9% of all engorged flies) ingested only one mf.