Fly Control for Biosecurity in Swine Farms

By Mike Catangui, Ph. D |

Flies are vectors or carriers of disease-causing microorganisms.

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.

Fly
Fig. 1. An adult house fly (Musca domestica).
Diseases that can be vectored by house flies on swine farms

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.

“Fly specks” or regurgitated stomach contents and feces deposited by house flies on a transparent surface.
Fig. 2. "Fly specks" or regurgitated stomach contents and feces deposited by house flies on a transparent surface.

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.

House fly baits for use in and around swine farms
+ Enlarge Prior to using any product mentioned in this article, carefully read and follow all available instructions, warnings and safety information made available by the product’s manufacturer. ** Restricted use insecticide in AK, IN, MI, and VT.
On-animal sprays for house fly control on swine farms
+ Enlarge Prior to using any product mentioned in this article, carefully read and follow all available instructions, warnings and safety information made available by the product’s manufacturer.
Empty-barn residual sprays for swine farms
+ Enlarge Prior to using any product mentioned in this article, carefully read and follow all available instructions, warnings and safety information made available by the product’s manufacturer. *Restricted use insecticide.
House fly larvicides for use on swine farms
+ Enlarge Prior to using any product mentioned in this article, carefully read and follow all available instructions, warnings and safety information made available by the product’s manufacturer. *Restricted use insecticide.
Ready-to-use aerosol on-animal sprays for swine farms
+ Enlarge Prior to using any product mentioned in this article, carefully read and follow all available instructions, warnings and safety information made available by the product’s manufacturer. * Do not ship animals for slaughter within 5 days of last treatment.
References Cited:
Allison G., P. Gauger, et al. 2018. PEDV, PRRSV, and Seneca Valley virus PCR positive flies (Musca domestica). What now? Proceedings of the 49th American Association of Swine Veterinarians Meeting.
Allison, G., P. Gauger, J. Zhang, and G. Spellman. 2019. PEDV positive bioassay reveal houseflies (Musca domestica) can transmit infectious PEDV to pigs. Proceedings of the 50th American Association of Swine Veterinarians Meeting.
Barber, D.A., P.B. Bahnson, R. Isaacson, C.J. Jones, and R.M. Weigel. 2002. Distribution of Salmonella in swine production ecosystems. Journal of Food Protection 65(12):1861-1868.
Dee, S.A., J.A. Schurrer, R.D. Moon, E. Fano, C. Trincado, and C. Pijoan. 2004. Transmission of porcine reproductive and respiratory syndrome virus under field conditions during a putative increase in the fly population. Journal of Swine Health and Production 12:242-245.
Enright, M. R., T.J. Alexander, and F.A. Clifton-Hadley. 1987. Role of houseflies (Musca domestica) in the epidemiology of Streptococcus suis type 2. The Veterinary Record 121(6):132-133.
Gough, P.M., and R.D. Jorgenson. 1983. Identification of porcine transmissible gastroenteritis virus in house flies (Musca domestica Linneaus). American Journal of Veterinary Research 44(11):2078-2082. Murvosh, C. M., and C.W. Taggard. 1966. Ecological studies of the house fly. Annals of the Entomological Society of America 59:534-547.
Nichols, G. L. 2005. Fly transmission of Campylobacter. Emerging Infectious Diseases 11(3):361-365.
Sasaki, T., M. Kobayashi, and N. Agui. 2000. Epidemiological potential of excretion and regurgitation by Musca domestica (Diptera: Muscidae) in the dissemination of Escherichia coli 0157:H7 to food. Journal of Medical Entomology 37(6):945-949

About the Author

Dr. Mike Catangui

Mike Catangui, Ph. D

Entomologist, Parasitologist
MWI Animal Health
Dr. Catangui is a member of MWI's Technical Services groups. As a team, this group provides our clients with targeted expertise in integrated pest management, proactive disease/pathogen and performance management, animal drinking water quality improvement, biosecurity, and cleaning and disinfection. 
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