JPC SYSTEMIC PATHOLOGY
Signalment (JPC #1747982): Chicken
HISTORY: Severe scaly, crusty lesions over the unfeathered portions of the legs
Histopathologic Description: Skin, stratum corneum: Diffusely there is abundant orthokeratotic hyperkeratosis. Multifocally, within the keratin, there are oval to elongate, 35 to 100um diameter clear spaces (mite tunnels) which frequently contain sections of arthropods that are oval to elongate, range from 125 to 250um in diameter, have an eosinophilic spiny chitinous exoskeleton, a hemocoel, striated muscle, and focal accumulations of deeply basophilic, 2um nuclei. Within the mite tunnels there are scattered accumulations of brown, granular and globular material (mite feces). There are frequent intracorneal abscesses composed of degenerate heterophils, eosinophilic cellular and karyorrhectic debris (necrosis), and occasional colonies of cocci and bacilli.
MORPHOLOGIC DIAGNOSIS: Skin, stratum corneum: Hyperkeratosis, orthokeratotic, diffuse, severe, with intracorneal mites and abscesses, chicken, avian.
ETIOLOGIC DIAGNOSIS: Cutaneous knemidokoptosis
CAUSE: Knemidokoptes (or Cnemidocoptes) mutans
- Mites of the genus Knemidokoptes, class Arachnida, order Acarina, family Knemidokoptidae
- mutans is common in chickens, turkeys and pheasants
- Found on older gallinaceous birds and non-hand-reared pet birds
- Affects non-feathered skin of the legs and occasionally the comb and wattles
- Usually found in older birds
- Entire life cycle is 2 weeks and is completed on/in the host's skin
- Eggs hatch into 6-legged larvae, molt into 8-legged nymphs and molt 3 more times into adults
- Transmitted by direct contact
- The mites penetrate and bore holes in the epithelium
TYPICAL CLINICAL FINDINGS:
- Lesions are usually not pruritic
- Hyperplastic lesions on the cere may obstruct nasal openings; hyperplastic lesions on the legs may cause decreased range of motion
TYPICAL GROSS FINDINGS:
- Scaly, hyperkeratotic encrustations on the featherless areas of the face and legs
- May encroach on the beak or claws
- If severely affected, beaks may become distorted, and affected toes may slough
- Minute pores visible on the surface
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Mild acanthosis and orthokeratotic hyperkeratosis
- Epidermis has dorsal, uninterrupted striations
- Possible granulocytic, lymphocytic or histiocytic inflammation in underlying dermis
- Microscopic characteristics of mites include: Spiny chitinous exoskeleton, jointed appendages, mouthparts, striated muscle
- Females are approximately 0.5mm in diameter with short, spherical legs that lack pretarsi
- Males are smaller and have longer legs with pretarsi and suckers
ADDITIONAL DIAGNOSTIC TESTS:
- Removal of affected scale may reveal mites on underside that are visible with a hand lens
- Carcinoma of the cere and beak (budgies)
- Passerine pox - intracytoplasmic inclusion bodies
- Papillomavirus - “tassel foot” in European goldfinches
- Neocheyletiella mites
- K. gallinae: Depluming mite of chickens, pigeons, pheasants and geese
- K. pilae: Scaly face mite of parakeets, finches and budgerigars
- K. jamaicensis: Golden thrush, canaries
- K. fossor: White-headed munia
- Altman RB, Clubb SL, Dorrestein GM, Quesenberry K. Avian Medicine and Surgery. Philadelphia, PA: W. B. Saunders; 1996: 341, 347, 549, 571, 884.
- Bowman DD. Georgis’ Parasitology for Veterinarians. 6th ed. Philadelphia, PA: W.B. Saunders; 1995: 66-67.
- Fitz-Coy SH. Parasitic diseases. In: Boulianne M., ed. Avian Disease Manual. 7th Jacksonville, FL: OmniPress; 2013:154.
- Gaudioso JM, LaPointe DA, Hart PJ. Knemidokoptic mange in Hawai’i’ Amakihi (Hemignathus virens) on the island of Hawai’i. J Wildl Dis. 2009;45(2): 497-501.
- Mainka SA, Melville DS, Galsworthy A, Black SR. Knemidocoptes on wild passerines at the Mai Po nature reserve, Hong Kong. J Wildl Di. 1994; 30(2):254-6.
- Hinkle NC, Corrigan RM. External parasites and poultry pests. In: Swayne DE, Glisson JR, McDougald LR, Nolan LK, Suarez DL, Nair V., eds. Diseases of Poultry. 13th ed. Ames, Iowa: Wiley Blackwell; 2013:1101-2.
- Pence DB, Cole RA, Brugger KE, Fischer JR. Epizootic podoknemodokoptiasis in American robins. J Wildl Dis. 1999;35(1):1-7.
- Randall CJ, Reece RL. Color Atlas of Avian Histopathology. London, England: Mosby-Wolfe; 1997: 46.