Backyard Chickens Harbor Greater Diversity of Mites and Lice than Farm-raised Chickens
By Meredith Swett Walker
Today’s backyard chickens are not your grandmother’s birds — they sport jaunty sweaters, go for walks on leashes, and dine on treats like “chunky chicken caviar.” As keeping chickens has become more popular, the bird’s status has been elevated from practical livestock to pampered pet. And though they may indulge in whimsy, the new generation of chicken keepers takes poultry husbandry seriously. They consider the nutritional needs of laying hens, carefully brood their baby chicks, and construct predator-proof (yet attractive) coops. But many backyard chicken fanciers have not considered the itchy subject of ectoparasites. Believe it or not, plucky Henrietta is probably harboring lice, mites or fleas.
Backyard chickens live a much sweeter life than their brethren on commercial poultry farms. But roaming green grass and scratching real dirt exposes these lucky birds to a different suite of parasites than those found in the controlled environments of most commercial facilities. Yet other than anecdotal reports of parasite problems by chicken owners, little is known about ectoparasites on backyard chickens in the United States. A paper in the latest issue of the Journal of Medical Entomology by University of California, Riverside scientists Amy C. Murillo and Bradley A. Mullens reveals what’s crawling on backyard birds, and the answer will likely make chicken fanciers itch.
The researchers surveyed 100 adult hens in 20 different backyards in southern California. The chickens were either sprayed with a mild pyrethrin insecticide or bathed with soap and water to stun or kill parasites. The birds were held in a dishpan during treatment to collect the parasites. In addition, the researchers searched crevices in coops where ticks and bed bugs may conceal themselves when not actively feeding on the birds. Samples of substrate from the coop were also collected and searched for ectoparasites.
Murillo and Mullens found a much greater diversity of ectoparasites on the backyard chickens than has been reported in commercial flocks. Ectoparasites were found on most of the flocks surveyed (80%) and lice were the most common and abundant. Six species of louse were found on the chickens, with the chicken body louse (Menacanthus stramineus) and the fluff louse (Goniocotes gallinae) being the most common. Some individual chickens had hundreds of lice. Sticktight fleas were found in only 20% of flocks, but infestations could be quite severe. The northern fowl mite (Ornithonyssus sylviarum) was the most common mite, but the scaly leg mite (Knemidocoptes mutans) and the chicken red mite (Dermanyssus gallinae) were also found.
Commercial poultry flocks are known to suffer from several of the same ectoparasites, including M. stramineus, O. sylviarum, and D. gallinae. But these birds are generally housed in “battery cages” that give them little contact with the ground or substrate that immature stages of parasites like fleas and some mites need to develop. In addition, these cages provide fewer crevices that might harbor ticks or bed bugs when they aren’t feeding on birds. Finally, birds in commercial flocks are generally all the same age and breed which may affect the suite of parasites that they host.
The results of this study suggest that some of the perks of being a backyard chicken, such as comfortable coops and access to the outdoors, might also increase the birds’ availability to ectoparasites. Many backyard chicken keepers may also be unaware of potential parasite problems. According to Murillo, many of the chicken owners that participated in this study were surprised to learn that their chickens had ectoparasites, and almost none of the owners were practicing parasite prevention.
“This is not surprising since products for ectoparasite control or prevention on chickens are not widely available,” she said. “Insecticides for use on cats or dogs, like Frontline, aren’t allowed for use on chickens.”
Fortunately, chicken ectoparasites don’t infest or bite humans. Nevertheless, they are distressing for the birds and may affect egg and meat production. While the researchers were able to remove ectoparasites by bathing chickens with soap and water, Murillo says this shouldn’t be done regularly as a means of parasite control.
“Chickens use naturally produced oils and dust bathing to keep their feathers in good shape, and too much washing would mess them up,” she said.
There is evidence that dust bathing does reduce parasite populations on individual birds, and that chicken keepers can aid this process by providing their birds with materials to bathe in, such as diatomaceous earth, kaolin clay, or sulphur powder. However, the success of these products depends on whether or not the chickens choose to bathe in them. Murillo also notes that because they are natural products that are not clinically tested or regulated like pesticides or veterinary drugs, their effectiveness may vary widely.
Further study of the ectoparasite community on backyard chickens in the U.S. will be necessary to develop effective prevention and treatment techniques. These birds may be enjoying the good life, but it turns out to be fairly itchy.
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Meredith Swett Walker is a former avian endocrinologist who now studies the development and behavior of two juvenile humans in the high desert of western Colorado. When she is not handling her research subjects, she writes about science and nature. You can read her work on her blogs http://picahudsonia.com and https://citizenbiologist.com or follow her on Twitter at @mswettwalker.
Editor’s Note: The headline of this article has been revised from an earlier version to remove reference to ticks. While the researchers whose work is summarized in this blog post note that “discussions with local poultry veterinarians suggest that [ticks] do become problems at times in inland southern California for chickens in backyard settings,” they were not found in the course of their study.