A review of common ectoparasites of backyard chickens

By Olivia A. Petritz, DVM, DACZM

Backyard poultry ownership in the United States has increased dramatically in the last couple of years, with an estimated total of 85 million backyard chickens. In the United Kingdom, backyard chickens have overtaken rabbits as the third most popular pet.¹

Backyard poultry are often considered pets by their owners, but they are also considered a major food-producing species in the U.S., along with cattle, pigs, and turkeys. Therefore, they are also subject to additional federal/state regulations, including those related to topical or systemic medications. Importantly, these regulations hold true regardless of the owner's perception of their chicken's role, whether pet or food-producing animal.

According to a survey of backyard poultry owners, 57 percent stated their chickens were solely kept as pets, but their eggs were consumed.² As a vast majority of backyard poultry live outdoors in a variety of different coops, ectoparasites are very common. According to one survey of backyard poultry on the West Coast of the U.S., 61 percent of all chickens examined at multiple farms had at least one ectoparasite.³ Let's review the most common ectoparasites of backyard hens and treatment options in the United States, as laws regarding the treatment of food animals, including chickens, vary from country to country.

Lice

Lice are one of the most prevalent ectoparasites of U.S. backyard poultry flocks, according to several published surveys.^3,4 In fact, 97 percent of all ectoparasites collected from poultry in one survey were lice, and only three percent were mites.³ The two most common are the chicken body louse (Menacanthus stramineus) and the shaft louse (Menopon gallinae).⁵ These lice are 3- to 6-mm long, with a flattened, ovoid body shape (Figure 1). As both are chewing lice, they do not take blood from the host; instead, they feed by chewing feathers and the skin around the feather base. All portions of their life cycle occur on the host bird, and eggs (nits) often are seen as white clumps at the base of the feather shafts (Figure 1).

Interestingly, the presence of lice often limits the prevalence of mites.⁶ Unlike other ectoparasites, lice can be found all over the host bird, and not in a particular location. Poultry lice have a predilection for poultry but can infect other birds if their preferred host is unavailable. They are not zoonotic and will not survive on humans or other mammals.⁵

Birds are often asymptomatic for mild lice infestations, but dermatitis, poor feather quality, and reduced egg production can be seen for more significant infestations, which tend to be worse in the fall and winter months.⁷

Lice can be easier to treat than mites due to their longer life cycle and short life span off the host.⁵ Poultry lice do not serve as vectors for any pathogens known to date. Beak trimming to prevent conspecific aggression in backyard poultry flocks is less common than in commercial flocks, which are often housed in close proximity to one another. However, chickens with trimmed beaks often have higher loads of ectoparasites (mites and lice) than chickens with normal beak occlusion.⁸

Mites

The three most common mites of backyard chickens are the northern fowl mite (Ornithonyssus sylviarum), the chicken mite or red mite (Dermanyssus gallinae), and the scaly leg mite (Knemidocoptes mutans). While lice are more prevalent in backyard flocks, mites, particularly the northern fowl mite, have more significant health implications for both commercial and backyard poultry flocks.^5,6

Northern fowl mite

The northern fowl mite is less than 1-mm long but is still visible with the naked eye as a tiny mobile black dot that may appear redder in color after feeding (Figure 2). They spend their entire life cycle on the host and can infect both domestic and wild birds.

Northern fowl mites prefer cooler temperatures and thus are most often found around the vent and uropygial (preen) gland. They also tend to be more of a problem in the fall and winter months in temperate climates.⁵

Survival times off the host are minimal (seven to 35 days under optimal conditions) compared to other mite species, and transmission via wild birds and fomites is common. These mites are not considered zoonotic, but they can be found crawling on people handling infested chickens, so appropriate precautions should be taken.

As these feed on blood, severe infestations can lead to clinically important anemia in addition to localized dermatitis and overall reduced egg production (10-15 percent in commercial flocks).⁶

It is estimated heavy infestations with this mite can lead to a six percent total body blood loss each day.⁶ A recent study evaluated chicken behaviors following experimental infestation with northern fowl mites compared with control flocks.⁹ Unsurprisingly, mite infestations increased preening behavior and the presence of skin lesions, but the authors stressed the potential negative impacts both of these findings could have on animal welfare.

Chicken mite

The chicken mite (Dermanyssus gallinae), also known as the red mite or roost mite, is another common mite and can also infect other birds. Similar to the northern fowl mite, the chicken mite is not considered zoonotic. Humans and all mammals can have transient infections, but are not competent hosts.

These mites are also approximately 1-mm long and can appear black or red following feeding. However, chicken mites spend the majority of their time off the host and only feed on chickens at night. This strategy makes them much more difficult to eradicate from chicken houses and coops, as they can survive in the environment for up to six months without feeding.⁵ This also means they rarely are a problem for people interacting with chickens during the day, caretakers, and veterinary staff alike. Clinical signs of infestation are identical to those seen with northern fowl mites, but identification of these mites is challenging due to their nocturnal feeding.

Chicken mites have been recorded to transmit fowl cholera (Pasteurella multocida) within chicken flocks.⁶

Scaly leg mite

Scaly leg mite (Knemidocoptes mutans) infestations lead to crusting and excessive keratin deposits on the distal pelvic limbs and toes of infected birds (Figure 3). These mites are not visible to the naked eye, as they burrow under the scaled skin of the pelvic limbs. Occasionally, infestations are noted around the beak of chickens, but they typically do not cause the pitted appearance and keratin overgrowth seen in psittacines infected with Knemidocoptes in this location. Severe infections can lead to deformed toes, lameness, and sloughed digits,¹⁰ which are rare in this author's clinical experience.

Scaly leg mites can survive off a host for several days and can infect many species of birds other than poultry.⁶ In addition to systemic antiparasitic medication, non-insecticidal treatments have been utilized for this mite, including coating the affected limbs in various forms of oil in an effort to suffocate the mites. Unfortunately, there are no studies evaluating these forms of topical therapy, which limits the specifics of treatment frequency, duration, and efficacy to only anecdotal reports.

Other parasites

Compared with domestic mammals, fleas and ticks are much less common in backyard poultry.

• Sticktight fleas (Echidnophaga gallinacean) can infect poultry, but also many other species, including cattle, goats, sheep, and even dogs and cats.⁵ If present, they are often found on the featherless regions of the face (comb, wattles, periorbital).Flea infestations can cause extreme pruritus in birds, and in severe infestations, anemia and death of juvenile birds.
• Fowl ticks (Argas persicus) are soft-bodied ticks more prevalent in warm, dry climates. They are approximately 8-mm long with an ovoid, flattened body shape. They are known to transmit several infectious diseases, including Borrelia anserina (Avian spirochetosis) and Aegyptionella pullorum (Aegyptianellosis).⁵ These ticks can be found on many avian species, both wild and domestic. They can bite humans, but such reports are rare.
• Common bed bugs (Cimex lectularius) are flat, wingless, light brown bugs that are 5- to 7-mm in diameter as adults, but will appear red after feeding (Figure 4). Bed bugs are obligatory hematophagous ectoparasites of humans. However, they can feed on other warm-blooded vertebrates, including chickens, rabbits, and mice.Bed bug control is challenging in any man-made structure due to their cryptic habits, the complexity of the environment, insecticide resistance, and the lack of labeled insecticides.

  There are increasing reports of severe bed bug infestations in commercial poultry farms; however, the prevalence in backyard poultry facilities remains unknown.¹¹
  

  

  Bed bugs do not serve as vectors for any known diseases, but can lead to dermatitis, feather loss, anemia, and reduced egg production. Currently, there are no effective products labeled for controlling bed bug infestations in poultry houses in the United States.

Treatments

Clinicians who treat chickens in the United States are strongly encouraged to review rules and regulations for treating major food-producing species, many of which are listed on the Food Animal Residue Avoidance Database (FARAD) website (www.farad.org).

Similar to mammalian food animals, certain drugs are prohibited for use in any chicken, including pets, regardless of their intended use. These mainly include antibiotics, antivirals, and indexed drugs. All U.S. Food and Drug Administration (FDA)-approved medications for laying hens must have a zero-day egg withdrawal period when used according to the label directions.

There are a few FDA-approved drugs for use in laying hens, and many of these drugs are available over the counter. For a complete list of recently approved drugs, visit the FARAD website.

Common topical ectoparasitic treatments in hens include ivermectin, permethrins, and tetrachlorvinphos. Many of these drugs are used anecdotally, with little to no published studies on effective and safe dosing regimens. Additionally, permethrin resistance in poultry mites is becoming increasingly common.⁵ It is imperative both veterinarians and owners follow labeled instructions and published egg withdrawal times for each of these medications. If withdrawal times are not known, please contact FARAD.

In addition, due to the off-host portions of the life cycle for many poultry ectoparasites, treatment of the environment is often required for complete eradication. Continued access to wild birds and rodents is an additional complicating factor that can limit treatment success and promote reinfestation of backyard poultry.

In 2025, fluralaner (Exzolt) became the first FDA-approved treatment for northern fowl mites in the United States by prescription only, for oral administration in drinking water. It is important to note that many published and/or approved antiparasitic treatments, including this formulation of fluralaner, are designed for administration via large volume water treatments for commercial poultry farms; an extrapolation for small backyard flocks can be challenging.

Unfortunately, many of these treatments are not permitted in organic egg production, which is a common reason for having backyard flocks.

A study found the provision of dust-baths with a combination of sand and food-grade diatomaceous earth (DE) to hens led to an 80 to 100 percent reduction of ectoparasites after one week compared with control flocks without the need for additional ectoparasiticides.¹² Food-grade DE is safe for accidental ingestion in small amounts in humans/animals. This is not the case for non-food-grade DE, which is dangerous to inhale or ingest, and should only be used for pool filtration.

For additional state-by-state information on registered ectoparasiticides in chickens and other species, veterinarians could consult this database: https://www.veterinaryentomology.org/vetpestx.¹³

Olivia A. Petritz, DVM, DACZM, graduated from Purdue University and then completed several internships and a residency in the field of zoo and exotic animal medicine at University of California, Davis. Dr. Petritz became a diplomate in the American College of Zoological Medicine in 2013, specializing in zoological companion animals (exotic pets). Petritz started an exotics service at a specialty hospital in Los Angeles, Calif., following her residency, and is currently an associate professor of Avian and Exotic Animal Medicine at North Carolina State University.

References

1. Mace, Jenny L., and Andrew Knight. "From the backyard to our beds: The spectrum of care, attitudes, relationship types, and welfare in non-commercial chicken care." Animals2 (2024): 288.
2. Elkhoraibi, C., et al. "Backyard chickens in the United States: a survey of flock owners." Poultry science11 (2014): 2920-2931.
3. Chambless, Kendra N., et al. "Diversity and prevalence of ectoparasites on poultry from open environment farms in the Western-United States of Washington, Idaho, Oregon, and California." Journal of Medical Entomology5 (2022): 1837-1841.
4. Murillo, Amy C., and Bradley A. Mullens. "Diversity and prevalence of ectoparasites on backyard chicken flocks in California." Journal of medical entomology3 (2016): 707-711.
5. Nair, Shakunthala Shaku, Dawn H. Gouge, and Amy C. Murillo. "Backyard chickens and ectoparasites: introduction and management." University of Arizona Cooperative Extension (2021). https://repository.arizona.edu/handle/10150/669985
6. Hinkle, Nancy C., and Robert M. Corrigan. "External parasites and poultry pests." Diseases of poultry (2020): 1135-1156.
7. Lennox, Angela. "Dermatological diseases." Backyard poultry medicine and surgery: A Guide for veterinary practitioners (2021): 259-274.
8. Chen, Brian L., Kathryn L. Haith, and Bradley A. Mullens. "Beak condition drives abundance and grooming-mediated competitive asymmetry in a poultry ectoparasite community." Parasitology6 (2011): 748-757.
9. Murillo, Amy C., et al. "Parasitic mites alter chicken behaviour and negatively impact animal welfare." Scientific reports1 (2020): 8236.
10. Morishita, Teresa Y., et al. "Scaly-leg mite infestation associated with digit necrosis in bantam chickens (Gallus domesticus)." Journal of Avian Medicine and Surgery3 (2005): 230-233.
11. Gonzalez-Morales, M.A., Thomson, A.E., Petritz, O.A., Crespo, R., Haija, A., Santangelo, R.G., and Schal, C. (2022). Systemic veterinary drugs for control of the common bed bug, Cimex lectularius, in poultry farms. Parasit Vectors 15, 431, 431. 10.1186/s13071-022-05555-1.
12. Martin, Christopher D., and B. A. Mullens. "Housing and dustbathing effects on northern fowl mites (Ornithonyssus sylviarum) and chicken body lice (Menacanthus stramineus) on hens." Medical and Veterinary Entomology3 (2012): 323-333.
13. Gerry, A. C. VetPestX: Database of pesticides for control of insect pests of animals (updated6/20/2024). Retrieved from https://www.veterinaryentomology.org/vetpestx