Psoroptic Mange in California Bighorn Sheep
Causative Agent
  • Psoroptes ovis is a non-burrowing ectoparasitic mite belonging to the family Psorptidae (Order: Acarina)
  • It is the cause of psoroptic mange, also referred to as “sheep scab”, psoroptic scabies or Psoroptes infestation, a highly contagious and devastating condition that can affect domestic and wild sheep.
  • Psoroptic mange has been the cause of significant economic loss in domestic sheep farms due to reduced condition and damage to the fleece in infested animals, and, accordingly, has been listed as an annually notifiable disease by the Canadian Food Inspection Agency (CFIA) under the Health of Animals Act.
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Psoroptic Mange - California Bighorn Sheep
Ram affected with psoroptic mange from Olalla, British Columbia.
  • Psoroptic mange is a newly recognized health issue of wild sheep in the Similkameen Valley of southern BC.
  • Despite occurring worldwide, Psoroptes mites are considered uncommon in domestic sheep and cattle as they are easily controlled with injectable pharmaceuticals.
  • Because it is so easily controlled, psoroptic mange was eradicated from Canadian domestic sheep in 1924.
  • While it is still present to varying degrees in some populations of bighorn sheep in the US, it has never before been reported in Canada prior to February 2011.
  • Mite populations are generally lower in the spring and summer, with increases in the fall/winter.
Hosts, Transmission and Life Cycle
  • In BC, California Bighorn Sheep (Ovis canadensis).
  • Transmission is typically through direct contact with infested individuals, making psoroptic mange a herd disease; it only takes a single gravid female mite to establish an infestation on an individual and, hence, the entire herd.
  • Fomites, such as contaminated fence posts, feeders, or chutes, are sources of infection in domestic animals, and similar contaminated objects in nature may play a role in transmission and maintenance of the mite among and within bighorn sheep populations.
Life Cycle:
  • Psoroptes ovis is an obligate ectoparasite - its entire life cycle occurs on a single host.
  • As mites abrade the skin and incite a potent inflammatory response, the subsequent exudate and crust that forms provides a perfect environment for mites to thrive and reproduce in.
  • A single female mite can deposit anywhere between 35-100 eggs in her adult lifetime, which is approximately 30-60 days.
  • Once hatched, mites proceed through one larval stage and two nymphal stages before finally molting into their adult form.
  • This entire lifecycle, from egg to egg, takes approximately two weeks, but may vary with environmental conditions.
Signs and Symptoms
  • In some locations and in some animals, a severe disease occurs where animals develop heavy crusts in and around their ears and over their bodies, lose hair and body condition, and subsequently may die.
  • The disease is considered an animal welfare issue due to the intense pain and irritation caused by the mites.
  • Signs in individual sheep may include:
    • yellowish, scaly crusts are usually seen on the ears/shoulders/neck in mild cases or early stages of the disease, and may spread with time to other regions of the body;
    • the animal is very itchy and will damage its skin by scratching, rubbing and biting, often causing secondary bacterial infections;
    • decreased appetite, weight loss, anemia and emaciation can occur in animals with severe skin lesions;
    • it is unknown why some animals develop severe disease, but it may be a result of poor immune systems or the presence of other health issues;
    • adult sheep can regrow hair and recover with time, but may continue to carry mites in their ears. Such “carrier” animals may or may not show signs associated with the mites, such as ear rubbing or head shaking.
Meat Edible?
  • Meat is edible, but heavy infesta­tions can result in secondary bacterial infections that preclude consumption of the meat.
Human Health Concerns and Risk Reduction
  • Captive or domestic animals are quarantined and treated with specific doses of injectable drugs; however, all animals must be treated, in some cases more than once, to eliminate the mites. If not, the untreated sheep will re-infest the herd.
  • Attempts to eliminate the mites from wild sheep populations have not been successful to date.
  • Psoroptes mites can spread to other herds of bighorns and potentially to other wild and domestic ungulates that are in close contact.
  • Mites are not contagious to humans.
Samples for Diagnosis
  • Photographs of affected animals and samples collected in alcohol from live or dead animals with confirmation by a laboratory experienced with mite identification is necessary for proof of Psoroptes infestation.
Similar Diseases
Further Reading
Return to Manual Home Page Disease List - Body Region Affected Disease List - Causative Agent or Risk Factor Disease Surveillance Form Glossary Contact Information
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