Fly Control for Biosecurity in Swine Farms
House flies (Musca domestica) are important in public health because they can vector many species of diseasecausing 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. Equally important, however, is the ability of house flies to transmit diseasecausing microorganisms originating from outside the hog barn into healthy pigs. There are times, such as right now, when we have to worry about house flies transmitting potentially devastating diseases that can impact all production phases of swine. Table 1 lists diseases that can be vectored by house flies in swine. Some of these diseases such as Campylobacter infection, E. coli infection, Salmonella infection, and Streptococcus suis infection can also harm human health.
Efficient vectors of disease
The house fly [Fig. 1] is a very common insect pest in swine production and processing facilities in the U.S. They alight and feed on the bodily secretions and excretions of hogs, 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. 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 2 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.
Controlling flies for biosecurity
Biosecurity aims to protect hogs from diseases; fly control is a component of biosecurity in hog barns.
Effective and economical fly control products are available to hog 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 hog barns 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, hogs 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 hogs 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 hogs 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 hogs to safely treat with residual insecticides listed in Table 4, the hogs 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]. Also available are ready-to-use aerosol sprays [Table 6] for quick-acting treatments around the swine farm.