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Scaly Leg Mite Infestation

Other Names: Knemidocoptiasis, Cutaneous Knemidokoptosis

Scaly leg mites (Knemidocoptes mutans) are a relatively common ectoparasite found in adult backyard chickens, turkeys, and pheasants worldwide. These mites are extremely tiny (not visible to the naked eye) and will spend their entire lives (10 to 14 days) burrowing tunnels underneath the cornified epidermis of the chicken’s skin.

K. mutans are normally found on the chicken’s legs and top of their feet, but on occasion may invade the comb, wattles, neck and/or beak. The tunneling action of the mites is damaging to the chicken’s skin tissue, resulting in hyperkeratotic lesions which appear as thickened, scaly skin, raised non-uniform scales, white crusting and seepage of tissue fluid. The presence of the mites is also very irritating and painful for the bird. Left untreated, it can lead to necrosis of the toes, lameness, and deformation of the legs and feet. Chickens infested with scaly leg mites have an increased risk of developing secondary bacterial infections due to the destruction of the skin barrier which if intact would help protect them invasion with harmful pathogens.

Transmission of Scaly Leg Mites


Scaly leg mites are spread between birds by direct contact with infected flock members. They are initially introduced into the flock through wild birds, rodents, or by already being present within the soil and surrounding environment.

Clinical Signs of Scaly Leg Mites in Chickens


Early signs of invasion with scaly leg mites in chickens are the appearance of flaking, scaly, crusting, and/or thickening of the skin on their legs and top of their feet. A normal, healthy chicken should have bright, smooth, uniform scales.
Signs of scaly leg mites in chickens
The scales of chickens infested with scaly leg mites will appear roughened, non-uniform, raised, and some may protrude upwards. If left untreated, parts of chicken's toes may slough off and the heavy crusting of the scales can start to interfere with joint flexion, resulting in lameness and deformity.

Diagnosis of Scaly Leg Mites


A diagnosis can be made by microscopic identification of the mites in skin scrapings, though clinical signs may be sufficient diagnostic in some cases.

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
Lameness
Reduced joint mobility
Necrosis of toes
Deformed feet

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