Mite infestation is life threatening infection in wildlife. Mites infect human, domestic and wild animals. If humans got infected this is known as scabies and if animals got infection, known as mange.
Sarcoptic mange is a contagious infection, whose causative agent is Sarcoptes scabiei. Sarcoptes scabiei belongs to family Sarcoptidae, which is microscopic organism, make burrows in the skin. It has been reported that sarcoptic mange has 10 orders, 27 families and about 104 species.
Commonly found in wild mammals. Wild animal host range include Red foxes (Vulpes vulpes), coyotes (Canis latrans), grey wolves (Canis lupus), dingoes(Canis lupus), cheetah (A. jubatus), Lynx (Lynx lynx), Wombats, Koalas(P. cinereus), Mountain gorillas(Gorilla gorilla graueri), Chimpanzee(Pan troglodytes), Impala (Aepyceros melampus), Gazelles, Ibex (Capra ibex), Antelopes, Wild buffalo(Bubalus arnee), and chamois (Rupicapra rupicapra) etc.
These burrowing organisms have separate sexes, male and female. Life cycle have 3 stages, firstly, female lay eggs and they develop into Nymph. Nymphal stage is divided into two forms include, protonymphs and tritonymphs. The female lay eggs in dermis at the level of stratum granulosum layer of epidermis.
S. scabiei has various strains which are host specific. So according to this phenomenon, there is wide range of wild hosts and they have less degree of cross infection. Wild animals get infected with scabies, when they get in contact with domestic animals, because due to urbanization, the wildlife habitat got disturbed when they get in-contact domestic animals either for food or other means.
S. scabiei burrows the skin below the stratum cornium and at level of stratum granulosum. S, scabiei has cutting mouth parts which are chelicerae and gnathosoma. Legs are equipped with hooks. Mites feed on the tissue’s fluid. There is very less information about substances which are secreted by mites to digest the host tissue and feed on it.
These substances include keratin digesting keratinases and proteolytic enzymes which aid in tissue digestion. These things lead to excessive disruption of skin layers and lead to infection called as mange in wild animals. if the number of mites is excessive there will be sort of allergic reaction, which can be fatal in some cases.
The cause of this allergic reaction are debris, dead tissue and dead mites and egg shells of mites. Types I and Type IV hypersensitivity have been reported in wild canids (red foxes) and wild boars. Initially there are non-pruritic lesions as infection progresses, it led to increase in number of mites and severe reaction. Severe crusty dermatitis and serosanguineous exudate are seen in wild ruminants (Ibex, Chamois and red deer).
Microscopic examination of skin indicates the erythrocytes in stratum cornium, inflamed hair follicles and sebaceous glands. There is also edema, initially there is neutrophils infiltration and large number of eosinophils, later lead to infiltration of lymphocytes as infection progresses. Mites can be seen sometimes in microscopic examination of skin.
In gross examination of skin there are erythematous patches on the skin & seborrheic dermatitis are seen early and here number of mites is abundant. Later, hypersensitivity reaction is seen in immune-competent hosts and lesion which were non-pruritic early become pruritic. When infection is at peak, skin disfunction is there, skin of animal become thickened, wrinkled, hyperkeratotic, darkly pigmented and marked alopecia, skin become greyish in color.
These lesions are seen on skin of forelimbs, hind quarter, shoulders, flanks and at the back of head. Crusts formed on skin surface causes hemorrhages and fissure formation in skin, which are mostly self-inflicted, because of continuous irritation to skin animal rub skin with solid surfaces and lead to self-inflicted injuries and It will lead to loss of animal vigor, animal become anorexic, emaciated and dehydrated. Ultimately, debilitated animal die.
It’s difficult to diagnose the S. scabiei infestation. Mostly diagnosed on basis of gross examination and clinical signs. The confirmatory test is skin scrapping, which Is performed by using 10% potassium hydroxide (KOH) solution.
Skin debris which is obtained from scrapping is dissolved by KOH and seen under microscope. It is easily identified under microscope by presence of idiosomal denticles and club shaped setae. ELISA is also used as one of its confirmatory tests.
Avermections are used most commonly for its treatment. Ivermectin has shown best results in treating different wild animal species. In wild canids and felines multiple treatments are given in form of ivermectin to knockout the infection.
Authors: Hammad Ur Rehman Bajwa1, Muhammad Kasib Khan1, Arsalan Zafar1, Zaheer Abbas1, Wasim Yousaf2
- Department of Parasitology
- Department of Animal Breeding and Genetics
University of Agriculture, Faisalabad