Culicoides variipennis (Diptera: Ceratopogonidae) complex in Virginia

Area of Science:

• Veterinary Entomology
• Molecular Ecology
• Medical Entomology

Background:

• Culicoides variipennis (Coquillett) is a complex of subspecies with varying roles in bluetongue virus transmission.
• Understanding the distribution and genetic distinctiveness of these subspecies is crucial for livestock health and international trade.

Purpose of the Study:

• To assess the taxonomic status and distribution of Culicoides variipennis subspecies in Virginia using isozyme electrophoresis.
• To determine the genetic relationship between Culicoides v. variipennis and Culicoides v. sonorensis populations in Virginia.

Main Methods:

• Sampling of immature Culicoides variipennis from aquatic habitats across 22 Virginia counties.
• Rearing of collected specimens to adult stage for analysis.
• Isozyme electrophoresis to analyze genetic variation and population structure.

Main Results:

• Culicoides v. variipennis was found to be widespread and genetically similar to populations in Maryland.
• Culicoides v. sonorensis, the primary North American bluetongue virus vector, was predominantly found in a dairy wastewater lagoon.
• Genetic analysis confirmed distinctness between the subspecies, with no evidence of introgression despite sympatry.

Conclusions:

• The distribution of C. v. variipennis and the localized presence of C. v. sonorensis in Virginia have implications for bluetongue virus epidemiology.
• Physico-chemical factors may influence the distribution of immature C. variipennis complex populations.
• Accurate knowledge of C. variipennis complex distribution supports regionalization of livestock exports to bluetongue-free countries.