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Scaly Leg Mites

Knemidocoptiasis

The scaly leg mite (Knemidocoptes mutans) is an ectoparasite (external parasite) of chickens that causes damage to the legs and feet. K. mutans is one of three different burrowing mite species from the Knemidocoptes genus. The other two species--K. gallinae and K. pilae are more commonly found on pet birds than chickens, and cause different disease manifestations and clinical signs.

K. mutans invades the feather follicles and epidermis, in which it burrows into and feeds on the keratin contained in the scales of the feet and legs. K. mutans are small, round mites with stumpy legs, claw like structures and tactile hairs. They are too tiny to be able to see with the naked eye, and can only be seen with the use of a microscope. It takes K. mutans 10-14 days to complete their life cycle, in which they spend their entire time on their host.

Clinical signs
Healthy chickens have scales that appear smooth and lie flat against the surface. When chickens are affected by K. mutans, the condition of their legs and feet will start to slowly deteriorate. Early signs include flaking, crusting, peeling, roughening or uneven-looking scales, with some lifting upwards. With time, K. mutans will cause more extensive damage and pain. One or multiple flock members might be affected, since the mites will move from bird to bird. Eventually, the heavy crusting on the legs can start to interfere with joint flexion, resulting in lameness and deformity. Signs of K. mutans infestations can be complicated by secondary bacterial infections and gross tissue inflammation.

When K. mutans attack feather-legged breeds, it is much more difficult to spot and to treat. Unfortunately, feather-legged chicken breeds are more susceptible to invasion by scaly leg mites.

Transmission
K. mutans are spread between birds by direct contact with infested flock members. They are initially introduced into the flock through the presence of wild birds, rodents, or by already being present within the soil and surrounding environment. K. mutans are found on both domestic and wild birds including hawks and owls.

Symptoms

Irritable behavior
Brittle, flaky or powdery legs/feet
Thickening and crusting
Raised scales
Lameness

Diagnosis

  • History
  • Clinical signs
  • Physical exam
  • Skin culture

Treatment

MethodDetails
Soak feetSoak the chicken's feet and legs in a small bowel or bucket with lukewarm water for 10 minutes.

Gently wash legs and feet using mild baby shampoo and a soft toothbrush.

Towel dry the feet and legs and gently exfoliate any dead, loose scales.
Suffocate the mites
Apply topical oil-based product or spray over the bird's feet and legs. There are several different types of oil products used, including paraffin oil, mineral oil, linseed oil, vegetable oil, olive, olive mixed with cayenne pepper and a few drops of sweet orange essential oil, coconut oil, petroleum jelly (Vaseline), VetRX, a petroleum jelly (1/2 cup), and many more.

Repeat application of topical product daily until the old scales fall off and new healthy scales are intact.
IvermectinOrally or topically at 0.2 mg/kg of body weight. Repeat in 10 to 14 daysG Butcher, C Beck UF
MoxidectinOrally or topically at 0.2 mg/kg once every two weeks
DO NOTEver cut or pick off scales as this can cause damage to their legs and feet.

Prevention

  • Provide flock with a dust bathing area
  • Maintain a clean environment

Prognosis

Depends on how quick the birds are treated.

Scientific References

Good Overviews

Blogs

Age Range

They are most often found on older, backyard chicken flocks.

Risk Factors

  • Feather-legged chicken breeds are more vulnerable
  • Recent relocation to a new environment

Patient Cases