Blow Flies and Dog Poop
Blow fly feeding.
Blow flies are usually metallic blue or green medium-sized flies. They are economically important because of their effects on public health, livestock and wildlife.
The breeding habits are diverse. Most species are attracted to carrion and even meat scraps in a garbage can. Others are attracted to animals (as well as humans) with injuries, sores and foul secretions and cause myiasis (invasion by fly larvae) and others are parasitic. It is generally recognized that the fly's body and feet are covered with germs and filth. However, their feeding habits make blow flies and their allies even more hazardous. Because of the structure of their mouthparts (see photo on the left), they can only feed in three ways: (1) suck up liquid food and filter out the larger particles, (2) moistening solid food with saliva or regurgitating a portion of its previous meal to liquefy it, and/or (3) suck up any viscous matter such as sputum, vomitus or feces with anything that is in it. I am sure the reader now has a greater appreciation of the public health significance of these insects that are closely associated with human activities.
The breeding habits are diverse. Most species are attracted to carrion and even meat scraps in a garbage can. Others are attracted to animals (as well as humans) with injuries, sores and foul secretions and cause myiasis (invasion by fly larvae) and others are parasitic. It is generally recognized that the fly's body and feet are covered with germs and filth. However, their feeding habits make blow flies and their allies even more hazardous. Because of the structure of their mouthparts (see photo on the left), they can only feed in three ways: (1) suck up liquid food and filter out the larger particles, (2) moistening solid food with saliva or regurgitating a portion of its previous meal to liquefy it, and/or (3) suck up any viscous matter such as sputum, vomitus or feces with anything that is in it. I am sure the reader now has a greater appreciation of the public health significance of these insects that are closely associated with human activities.
Five blow flies are dining on this dog poop.
I have studied the feeding habits of blowflies in California and Idaho. Dog feces (poop) is second only to carrion as a food source for adult blow flies. One study was conducted to determine blow fly breeding in dog poop collected in some Boise city parks. Although 17 species of flies were found breeding in the dog poop collected in the parks, no blow flies were reared. Nevertheless, blow flies and others are very important in the transmission of harmful organisms of public health importance.
In addition, the study revealed an alarming public health risk from dog poop in some of the city parks (study conducted in the late 70s and early 80s). Of importance was the density of poop around playground equipment. The worse case was 41 piles of dog poop within a 35-foot radius of a picnic table and four pieces of playground equipment. Dog poop exposure where people congregate presents not only a nuisance, but a serious public health problem. A number of diseases are transmitted to humans through dog poop. Most common is salmonellosis, since approximately 20 percent of the dogs may possess the bacteria of this disease. Some human cases of salmonellosis in the Treasure Valley have been associated with poop of the family pet (the dogs tested positive for the disease also). In these situations, transmission is fecal/oral -- humans unintentionally consuming dog poop. Another disease is toxocariasis which is primarily found in young children. The extent of the occurrence of this intestinal roundworm in dog poop in the Treasure Valley is not known. However, in Salt Lake City, the rate in dog feces is 4.5 percent.
As a result of community activism and regulation, the reduction of dog poop in Treasure Valley parks has significantly improved over the last three decades. I still have interest in this matter.
In addition, the study revealed an alarming public health risk from dog poop in some of the city parks (study conducted in the late 70s and early 80s). Of importance was the density of poop around playground equipment. The worse case was 41 piles of dog poop within a 35-foot radius of a picnic table and four pieces of playground equipment. Dog poop exposure where people congregate presents not only a nuisance, but a serious public health problem. A number of diseases are transmitted to humans through dog poop. Most common is salmonellosis, since approximately 20 percent of the dogs may possess the bacteria of this disease. Some human cases of salmonellosis in the Treasure Valley have been associated with poop of the family pet (the dogs tested positive for the disease also). In these situations, transmission is fecal/oral -- humans unintentionally consuming dog poop. Another disease is toxocariasis which is primarily found in young children. The extent of the occurrence of this intestinal roundworm in dog poop in the Treasure Valley is not known. However, in Salt Lake City, the rate in dog feces is 4.5 percent.
As a result of community activism and regulation, the reduction of dog poop in Treasure Valley parks has significantly improved over the last three decades. I still have interest in this matter.
References:
- Brothers, DR. 1967. An evaluation of a domestic fly population survey: I: population distribution. Unpublished paper. 22 pp.
- Brothers, DR. 1970. Notes on the saprophagous activity of Bufolucilia silvarum (Meigen) (Diptera: Calliphoridae). Pan Pacific Entomologist 46:198-200.
- Brothers, DR. 1984. Testimony presented to the Idaho Parks and Recreation Board. Unpublished paper. 7 pp.
- Brothers, DR. 1985. Public Health Significance of dog droppings. Unpublished presentation. Idaho Environmental Association. 5 pp.
- Brothers, DR. 1999. Blow flies (Diptera, Calliphoridae ) of Idaho: an annotated checklist. Western North American Naturalist (Great Basin Naturalist). 59(1):92-96.