Fly Control for Biosecurity in Poultry Farms
House flies (Musca domestica) are important in public health because they can vector many species of disease-causing bacteria, viruses, helminths and protozoans to humans. Because human disease-causing microorganisms can originate from livestock, farm-level house fly control programs are mainly designed and implemented to prevent potential local and outward fly migration and disease transmissions from the farm to nearby human establishments and population centers. Thus, the U.S. Food and Drug Administration closely monitors house fly populations in egg-producing chicken farms to prevent Salmonella Enteritidis infections in humans (USFDA, 2011).
Equally important, however, is the ability of house flies to transmit disease-causing microorganisms originating from outside the poultry house into healthy chickens and turkeys. And there are times, such as right now, when we have to worry about house flies transmitting potentially devastating poultry diseases that can impact all production phases of susceptible turkeys, egg-laying hens and broiler chickens. There are currently no published studies that show house flies can vector the highly pathogenic avian influenza H5N2 virus in poultry in the United States. However, house flies have been shown to be competent vectors of the highly pathogenic avian influenza subtype H5N1 virus in chickens in Thailand (Wanaratana et al., 2013). And because of the long list of disease-causing microorganisms that house flies can vector, and the lag time before formal scientific studies can be conducted and published (if ever), house flies will need to be controlled right now to minimize the risk of probable avian influenza H5N2 disease transmissions by house flies into poultry houses. Table 1 presents serious diseases of poultry that can be vectored by house flies.
Flies are efficient vectors of diseases
The biology and behavior of house flies make them an efficient vector of diseases. The house fly [Fig. 1] is a very common insect pest in U.S. poultry production and processing facilities. They alight and feed on the bodily secretions and excretions of poultry, and on the feed and water provided to these farm animals. House flies occur year round on the farm; they can breed and multiply outdoors and indoors during the summer, and mostly indoors during the winter. During the spring and summer months, house flies may pick up disease-causing microorganisms from sources outside the barn (e.g., droppings from wild or migrating birds from nearby wetlands), then bring them inside the barns to start the infection process. House flies are notorious for depositing “fly specks” or regurgitated stomach contents and feces on surfaces wherever house flies feed and roost. These “fly specks” may be laden with disease-causing microorganisms. The number of “fly specks” [Fig. 2] on the walls and ceilings of the barn is usually proportional to the number of
active house flies in the area.
House flies can disperse to far distances. Most adult house flies stay within two miles of their breeding sites but some can migrate to up to 20 miles away (Murvosh and Taggard, 1966). It is also well known that house flies can “hitch a ride” in pickup trucks and other animal transport vehicles. In this manner, infected house flies can potentially disperse to clean sites several hundred miles away from the source.
Fly control products
Effective and economical fly control products are available to poultry producers. There are several effective and relatively inexpensive house fly insecticides to choose from [Tables 2-5]. House fly baits can be scattered in strategic exterior and interior areas of poultry houses to lure and kill house flies [Table 2]. Liquid or “sprayable” baits are also available for application on vertical surfaces or areas where solid baits are not practical. For immediate reduction in house fly numbers, poultry can be sprayed directly with insecticides that have “on-animal” labels [Table 3]. These “on-animal” sprays are quick-knockdown house fly insecticides with shorter residual action. During barn clean out, or when the birds are not in the barn, insecticides with longer residual effects can be applied on the surfaces of the empty barn where house flies will tend to congregate once the birds are placed inside. Empty-barn residual sprays [Table 4] can provide months of residual house fly control. Although the barns need to be empty of chickens or turkeys to safely treat with residual insecticides listed in Table 4, the birds can be placed immediately in the treated barns once the spray has dried out. For a more complete and longer lasting fly control program, the larval or maggot stage of the house fly can be treated in their breeding sites with effective larvicides [Table 5]. Lastly, because insecticide application equipment can greatly influence the efficacy and efficiency of any fly control program, poultry growers are encouraged to consider the recommended equipment listed in an articled entitled “Spray, mist or fog: Get to know your insecticide application equipment” (Catangui, 2019).