Occurrence: Worldwide. Mosquitoes are common in areas near still or stagnant water or in damp climates.   Species affected: All.   Age affected: All.

Cause: Order Diptera includes all flies (species of Culicoides, Simulium, Musca and Fannia) and mosquitoes (Culex and Psorophora spp.).

Effects: Adult flies and mosquitoes are ideal vectors of disease. Can be so numerous as to create a health and public relations concern.

The order Diptera includes biting and non-biting flies and mosquitoes. All dipterans have two wings in the adult stage (except degenerate wingless forms) and pass through a complete metamorphosis including a maggot-like larva and puparium resting stage. Adult mouthparts are of the piercing-sucking or sponging types. Because of the intermittent nature of their feeding and extensive flight range, adult flies are ideal vectors of disease. Certain species develop in poultry manure and may become so numerous as to create a health and public relations problems. In hot weather the housefly can complete its life cycle in 8 days, in cold weather this can take over 6 weeks.

Poultry production facilities that utilise lagoons can have problems with mosquitoes breeding in the lagoon.

Although mosquitoes are not as important to poultry as to human beings and other mammals, many species feed on poultry and transmit disease, including fowl pox. Some 140 species of mosquito have been described in North America alone and a number of these are known to suck avian blood. Mosquitoes may attack poultry in dense numbers, carrying and transmitting viral agents of Eastern Equine Encephalomyelitis (EEE), St Louis Encephalitis (SLE) and Western Equine Encephalomyelitis (WEE). Fowl pox virus is transmitted by Aedes stimulants, A. aegypti, A. vexans, and many species of culicoides-biting midges. Aedes stimulants may harbour the virus for 2 days, whereas A. vexans may infect birds up to 39 days after contacting the virus of fowl pox and pigeon pox.

Flies and mosquitoes are commonly found around poultry houses and can be identified by sight.

Adult flies have wings, are active during the daytime and lay eggs in poultry manure, in moist soil, spilled feed or on the carcasses of dead birds. Adult flies, larvae (maggots) and pupae will all be seen in and around the poultry house. Although flies do not commonly cause direct health concerns, they may transmit disease agents.

Most species of mosquito are about 5mm in length and their wings are commonly veined and scaled. Their legs and abdomen are long and the female is provided with elongated mouthparts for piercing the skin. The male does not suck blood. Mosquitoes deposit eggs on pools of water, moist soil, or surfaces subject to flooding. Larval and pupal stages develop in water, with adults emerging from pupal cases to mate and then seek a host. In warm weather the life cycle is completed in about 7-14 days. Adults are most active towards evening and at night. Mosquitoes may attack poultry in dense numbers. Birds may be seen to be agitated and in severe cases anaemia and anorexia may be seen. On close examination bites may be seen on the skin of birds.

Adult flies, larvae (maggots) and pupae will all be seen in and around the poultry house. Diagnosis is made by visual identification of adult flies and mosquitoes or their larvae. Larvae (maggots) may be seen in and around manure and spilled feed. Adults are active during the day.

Flies can be controlled by management practices such as manure composting, which will generate enough heat to control fly development. The use of dry cups in the house and automatic feeders will keep the litter dry and free of feed. Use of pits and lagoons in cage layer house will keep faeces from building up in the house. Slats under feeders and waterers will keep the house litter dry and will also allow for easier treatment of the faeces with chemicals.

Pyrethrum fly sprays can be fogged in houses or on ranges to obtain quick kill of mosquitoes in an outbreak, but control will not last more than a few hours. Residual sprays of carbaryl, malathion, propoxpur or stirofos can be applied to exterior surfaces of buildings or outdoors to vegetation from which poultry are excluded. If needed, breeding areas can be treated with larvicides or a biological control agent.

Commercial baits are formulated as granules and should be placed in pans or in protected areas. Bait can be placed on fly-traps. To increase the effectiveness of dry bait, such as methomyl, one part field-grade molasses may be diluted with three parts water in a 5-gallon (20 litre) can and covered with a removable window screen lid on which the dry bait is placed. Some commercial baits add a fly attractant.

Control of fly larvae in manure is done with a larvicide, which can be applied as a liquid, dry or in the bird’s feed. Larvicide treatment should only be done on a spot treatment, where large numbers of larvae are seen, as larviciding manure disturbs the natural balance of predators and parasites to the larvae. One exception tot his rule is the larvicide cyromazine, which is toxic to fly larvae, but not to their predators or parasites.

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