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Ectoparasites - Sarcoptes

Sarcoptes scabiei: Itch mite, mange mite. Not reported in cattle in NZ but reported in other animal species including man.

General Description: Itch mites are small, about 330 to 600 microns by 250 to 400 microns, and roughly circular in shape. All legs are short; the third and fourth pairs do not project beyond the body margin. The upper surface has many small triangular scales. Females have a number of spines on this surface. Pretarsi are present.

Life Cycle: Typical mite life cycle in which the entire life cycle is spent on the host. Sarcoptes mites are very susceptible to drying. Females burrow a tunnel in skin and here lay 3 to 5 eggs daily to a total of 40 to 50 eggs. Larvae hatch in 3 to 5 days. Some larvae remain in the tunnel in which they hatched, while others wander over the skin surface before burrowing new tunnels. Mange is most prevalent in late winter and early spring.

Location: Sarcoptes mites prefer areas of thin hair, such as the neck, the back in front of the tail, the inner surface of the thighs and the udder.

Geographical Distribution: Widespread where cattle are kept in close quarters.

Significance: Mange may spread to involve all parts of the host´s body. Irritation to the host causes weight loss, emaciation, and possibly death. Skins of carcasses are of poor quality. Animals in poor condition due to mite attacks are subject to other diseases.

Effect on Host: Mites puncture the skin to feed on lymph and may also ingest skin cells. Irritation causes intense itching and scratching which results in dermatitis, accompanies by an exudate that coagulates and dries to form a crust. Skin becomes thickened and wrinkled; hair is lost.

Diagnostic Information: Mites may be found microscopically in scrapings of lesion. Instruments such as a knife must be used to scrape into deep layers of skin. This is the major difference between Sarcoptes mites and Psoroptes mites, which are found on the surface of the skin.

Control: Application of chemicals through washes, dips, or sprays is used to control Sarcoptes scabiei. Ivermectin is effective in the control of S. scabiei.

 
Sarcoptes – gravid female   Scanning electron microscope photo – sarcoptic mite
     
 
Mite eggs deposited in burrows in skin   Head of cow showing sarcoptic mange

 

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