Flies, Gnats, and Mosquitoes of Poultry

Though many different species of flies may be found in poultry systems, the house fly Muscsa domestica and little house fly Fannia canicularis are usually the most abundant and significant, especially if manure is wet. Eggs are laid in moist manure, where larvae then feed and develop, completing three instars in as little as 4–7 days. They pupate in drier manure (eg, near the manure surface or edge of a pile) or will crawl away to some drier but concealed location up to a few meters away. The whole cycle from egg to adult can be completed in 7–10 days. Little house flies closely resemble house flies, but adults are smaller and larvae (maggots) are brown and spiny in contrast to the white, smooth house fly. Little house flies develop more slowly, prefer cooler temperatures, and tend to be a nuisance early in the spring before house fly populations have had a chance to escalate.

Adult flies of both species are a nuisance and can vector several poultry disease agents, including Newcastle virus. Flies rest at night near roofs and eaves, leaving regurgitation and fecal spots that can be used to estimate relative fly populations. Elimination of larval development sites is the best way to decrease fly populations. This can be done by drying out manure or by flooding manure, which makes it too wet for maggots. Insecticidal baits are a typical control method for adults.

Culicoides spp (Ceratopogonidae) feed on blood and transmit blood parasites to birds. They are vectors for transmission of Haemoproteus to ducks and geese in Canada and to turkeys in North America, and of Leucocytozoon to chickens in Southeast Asia and Japan. They also transmit the skin mite Myialges anchora (Epidermoptidae). Midge bites are reddish and itch for as long as 3 days. Midges feed at twilight or night, and typical mesh screens do not keep them out. Insecticides can provide temporary control.

Simulium spp (Simuliidae), also known as buffalo gnats and turkey gnats, are bloodsuckers and transmit leucocytozoonosis to ducks, turkeys, and other birds. They are most abundant in the north temperate and subarctic zones, but many species are found in tropical areas. They often attack in swarms and cause weight loss, reduced egg production, anemia, and death of birds either directly or through disease transmission. Control is extremely difficult because immature stages are restricted to running water, which is often some distance from the poultry farm. Larval control can be achieved with applications of Bacillus thuringiensis israelensis during early spring before adults emerge. Chemical larvicides can also be used. Screens of 24 mesh per inch (2.54 cm) or smaller are required for adult control. However, black flies rarely enter shelters.

The pigeon fly, Pseudolynchia canariensis (Hippoboscidae), is an important bloodsucking parasite of pigeons in warm or tropical areas. It can transmit the blood parasites Haemoproteus and Trypanosoma, the skin mite Myialges anchora (Epidermoptidae), and pigeon lice (Columbicola columbae). It may also cause heavy losses in squabs. The pigeon loft should be cleaned every 20 days, and squabs can be dusted with insecticides.

Mosquitoes that feed on poultry blood usually belong to the genera Culex, Aedes, or Psorophora. Large numbers can decrease egg production or cause death. Mosquitoes transmit Plasmodium gallinaceum (chicken malaria), P hermani (in turkeys), and other Plasmodium species causing avian malaria. They also transmit many viruses, including Eastern and Western equine encephalomyelitis, St. Louis encephalitis, fowlpox, and West Nile viruses. West Nile virus is transmitted from infected birds to other birds primarily by mosquitoes, particularly Culex spp in the USA, and has been found in >200 species of birds in America, including chickens, turkeys, pigeons, budgerigars, cockatiels, ducks, finches, and birds of prey.

Removal of mosquito-breeding habitats by emptying water-filled containers, clearing pool and pond edges of emergent vegetation, draining swampy areas, and filling low areas that collect water are the best physical control measures. Insecticidal control should target larval development sites. Insect growth regulators such as methoprene and diflubenzuron are also effective. Microbial control of mosquito larvae uses Bacillus thuringiensis israelensis and, against Culex spp, Bacillus sphaericus. Screening to prevent mosquito entry, residual wall sprays, and fogging within poultry houses also aid in control.