Culicoides

Systematics/Taxonomy/Identification

The genus Culicoides is part of the suborder Nematocera. Members of the genus tend to be small, fragile insects with long antennae, from which they derive their name. Midges belong to the family Ceratopogonidae and are distinguished by their 15-segmented antennae, sexual dimorphism and distinctive wing venation. The important bloodsucking species are found in the genera Culicoides and Leptoconops. Feeding of Culicoides midges is largely restricted to the night. Most Culicoides have a wing pattern that is composed of grey and white spots that are unique to each species.

Biology/Ecology

All Culicoides species display a typical holometabolous life cycle and only the females, which need blood for the completion of the gonotrophic cycle, are haematophagous and pool feeders. The bites of these midges are painful. The immature stages are always aquatic or semi-aquatic. Both the males and females feed on plant juices.

Distribution

With the exception of Antarctica and New Zealand, Culicoides midges are found virtually worldwide. The most important Culicoides vectors of orbiviruses include C. imicola in Africa, C. sonorensis in North America, C. insignis in South and Central America, C. wadai, C. brevitarsis and C. actoni in Australia, C. fulvus, C. schultzei in Asia and C. imicola, C. ulicaris and C. obsoletus in Europe.

Importance

Female Culicoides midges feed on a broad spectrum of hosts including reptiles, mammals, birds, humans, and even blood-engorged mosquitoes. Their bites may be a severe nuisance to humans in certain parts of the world and can cause an acute allergic dermatitis in horses. They are biological vectors of viruses, protozoa and filarial nematodes in birds, humans, and a range of domestic and wild animals. Among the viruses that are transmitted by Culicoides species are those causing bluetongue, African horse sickness, equine encephalosis and epizootic haemorrhagic disease which are all of major veterinary importance.

Around livestock, Culicoides can occur in remarkable high numbers especially on warmer nights and during periods of excessive rainfall. During these periods more than 1 000 000 C. imicola can be captured in a single light-trap. It is estimated this may represent less than 0.001% of the number of midges active on a particular night. This illustrates the intensity of attacks that may occur on exposed animals.

Control

Most of the Culicoides-transmitted diseases can be controlled by vaccination, stabling of animals at night, meshing of stables, and application of insect repellents both to the animal and its stable environment.

Sampling /Collection methods

Only a limited number of suction light traps, the primary monitoring tools for the collection of midges, are commercially available. These traps make use of a light source to attract Culicoides midges and a fan to draw them into a holding cage or container. The variation in the trap types used by different laboratories/research groups makes direct comparison between investigations difficult. The number of Culicoides collected in light traps is not necessarily comparable to species diversity and host bite rate.