Depluming Mites in Chickens: Symptoms, Causes and Treatment

Knemidocoptes laevis is a small (0.2mm) burrowing mite that spends its entire lifecycle on the host, tunneling into the epidermis at the feather follicle base.

• Direct bird-to-bird contact: K. laevis completes its lifecycle entirely on the host and survives only hours off the bird. Transmission requires direct physical contact between birds. Introduction of an infested bird into a clean flock spreads the mite to all birds in contact over 2-4 weeks.
• Distinguish from K. mutans: Knemidocoptes mutans (scaly leg mite) burrows under leg scales. K. laevis burrows into feathered body skin. Both cause crusting but at different body locations. Treatment is similar for both.
• Long-term subclinical carriage: Mite populations can remain at low levels for months before the bird's immune response fails to contain them, causing sudden apparent onset of symptoms. This explains why birds can appear healthy for months and then develop sudden severe depluming.
• Stressed or immunocompromised birds: Malnourished or immunosuppressed birds develop much more severe depluming mite infestations than healthy birds exposed to the same mite load.

Depluming mites are confirmed by microscopic examination of feather base scrapings.

• Scraping technique: Grasp a feather with obvious crust at its base and pull firmly. The crust and surrounding skin debris collected at the base is placed on a microscope slide with a drop of mineral oil. Cover slip and examine at 40-100x for mites and eggs.
• Clinical differentiation: Feather pecking from flock mates causes feather breakage at varying heights. Depluming mite self-plucking is recognized by the bird's constant preening attention to its own feathers and the characteristic crust at feather bases.
• Differentiate from nutritional deficiency: Methionine, lysine, or protein deficiency can cause feather pulling and poor feather quality. Depluming mites show crust at feather follicles; nutritional deficiencies show poor feather quality without crust.

Ivermectin is the most reliable treatment for depluming mites.

Ivermectin: 0.2 mg/kg body weight applied topically (1% ivermectin solution) to the bare skin on the back of the neck, or administered orally. Repeat in 14 days to kill mites that hatched after the first treatment. Do not use in birds producing eggs for human consumption; observe withdrawal periods per your country's regulations.

Lime sulfur dip: Dilute lime sulfur solution (8% concentration) applied as a whole-body dip or spray weekly for 3-4 weeks is effective for depluming mites. Wear gloves and eye protection; lime sulfur has a strong odor and is caustic to human skin.

Isolation: Isolate all affected birds from the flock immediately to prevent spread. Treat the entire flock, not just visibly affected birds, as subclinical carriers facilitate reinfection.

• Quarantine all new birds for 30 days before flock integration. Inspect for crust at feather bases and self-plucking behavior during quarantine.
• Examine the feather base condition of flock birds monthly, especially during winter when mites tend to proliferate faster under dense feathering.
• Maintain good nutrition. Well-nourished birds with healthy immune function contain depluming mite populations far more effectively than stressed or malnourished birds.
• Treat any newly acquired birds prophylactically with ivermectin before introducing them to the flock, regardless of apparent health.