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Scaly Leg Mite Infestation

Other Names: Knemidocoptiasis, Cutaneous Knemidokoptosis

Scaly leg mites (Knemidocoptes mutans) are a relatively common ectoparasite of chickens, affecting backyard and free range flocks worldwide. K. mutans are sarcoptic mites (burrowing mites) which burrow into the cornified epidermis of the skin, causing tissue damage. The mites are most often found on the legs and feet, but occasionally the comb, wattle, neck and/or beak. The presence of the mites causes irritation and hyperkeratotic lesions.

Prolonged infestations with K. mutans can lead to necrosis of the toes, lameness, and permanent deformation of the feet. In addition, the compromised skin barrier puts the birds at higher risk of developing secondary bacterial infections.

Clinical Signs of Scaly Leg Mites in Chickens


The scales on the chicken's legs and feet should normally appear smooth and flat. When infested with K. mutans the scales often appear dry, crusty, uneven and raised. The skin will be thickened.
Signs of scaly leg mites in chickens
Eventually, the heavy crusting of the scales can start to interfere with joint flexion, resulting in lameness, deformity, and necrosis.

Transmission of Scaly Leg Mites


K. mutans are spread between chickens by direct contact with infected birds. They are initially introduced into a flock through adding a new chicken who is infected already, or exposure to wild birds or rodents.

Treatment of Scaly Leg Mites in Chickens


In order to initially suffocate the mites and help promote growth of new scales, paraffin oil or petroleum jelly (Vaseline) is applied to the legs and feet of each infected bird. Repeated daily until the old, damaged scales have fallen off, and new healthy scales have grown in. In moderate to severe cases, administration of 1% Ivermectin or Moxidectin is needed.

Clinical Signs

Flaking, crusting, scaling, or roughened skin
Uneven or lifting of scales
Thickening of the skin
Increased itching
Damaged leg feathers

Diagnosis

  • History
  • Clinical signs
  • Physical exam
  • Skin scrapings

Reported Cases

  • Case 1: Digit necrosis in a Chickens In a flock of bantam chickens, proliferative skin lesions were observed on the shanks of 6 of 29 birds. Some of the birds also showed digit necrosis. Histologic examination of the necrotic digits revealed Knemidocoptes species in the stratum corneum. No new cases of scaly-leg mite infection occurred in the flock after administration of ivermectin, and treatment halted the progression of the disease process in infected chickens. Ref

Treatment

NameSummary
Paraffin oil, Coconut oil, Shea butter, or petroleum jelly (Vaseline)Apply over the bird's feet and legs.
IvermectinApplied topically or given orally at 0.2 mg/kg, once every two weeks. Two weeks after the first treatment, the scales should start sloughing off.
MoxidectinPour-on or injectable forms are both effective, and available in 0.5% and 1% preparations.
Dergall
Ectoblaster sprayTopical application to damaged areas of the skin.

Support

Prevention

  • Provide your flock with a dust bathing area
  • Maintain a clean environment
  • Keep rodents out of coops
  • Prevent contact with wild birds
  • Thoroughly clean and disinfect any tree branches brought in to be used as perches for birds.
  • Reduce stress

Prognosis

Depends on the severity

Scientific References

Good Overviews

Blogs

Age Range

More likely to occur in older birds.

Risk Factors

  • Increased age
  • Feather-legged chicken breeds are more susceptible.
  • Recent relocation to a new environment.
  • High populations of wild birds
  • Injured, sick, stressed or malnourished birds
  • Overcrowing

Case Stories