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

This study examines factors that influence the ingestion of an Onchocerca cervicalis microfilaria by a type of fly, Culicoides variipennis. The researchers find that the fly’s ingestion is independent of feeding time and engorged weight, but influenced by previous feeding activities.

Objective and Methodology

• This research aimed to identify the factors that impact the ingestion of Onchocerca cervicalis microfilaria (microscopic thread-like worms) by the Culicoides variipennis, a species of biting midges.
• Researchers used two ponies that exhibited seasonal changes in the skin density and distribution of the Onchocerca cervicalis microfilaria. These ponies were exposed to the flies under controlled conditions.
• Flies were allowed to feed on the umbilical area of the infected ponies in two different ways: either individually in a consecutive order at the same site, or by mass feeding.

Results

• It was observed that the seasonal changes in microfilarial skin density and skin distribution did not significantly affect the ingestion of microfilaria by the flies.
• Findings from the linear regression analysis revealed that the ingestion of microfilaria was independent of both the feeding time and the engorged weight of the fly. This means that the quantity of microfilaria ingested by a fly was neither influenced by how long the fly fed on the pony nor by how much the fly’s weight increased after feeding.
• In contrast, activity from previous feedings did impact future ingestion rates. Observations from individual feeding data showed a trend toward an increased ingestion of microfilaria as the feeding time increased, suggesting that longer feeding times could lead to greater ingestion.
• For mass feeding trials, it was suggested that early feedings by the flies may influence the ingestion rates of flies that feed on subsequent days.
• Out of 1,104 flies that fed on both ponies over a two-year period, 220 (or 20%) ingested microfilaria, while 99 (or 9% of all engorged flies) ingested only one microfilaria.

Conclusion

• This study sheds light on the feeding behavior and microfilarial ingestion patterns of Culicoides variipennis flies, which can aid in further studies related to vector behavior and the spread of diseases caused by these microfilarias.