It is the practitioner's duty to recommend a safe and effective treatment regimen, but this proves difficult when treating mange in sheep and goats. In the USA, ectoparasiticides are regulated by the Environmental Protection Agency (EPA) or the FDA Center for Veterinary Medicine. As a general rule, if a product is applied topically to an animal to treat ectoparasites, it likely falls under the jurisdiction of the EPA. If a topical product is used to treat both external and internal parasites, it likely falls under jurisdiction of the FDA. This distinction is important for practitioners to recognize, because there is no legal extra-label use of products regulated by the EPA. Label directions must be followed regarding species treated, product concentration, product dosage, individuals allowed to administer application, and re-treatment interval. Because products regulated by the FDA are approved animal drugs, extra-label drug use may be allowed under the Animal Medicinal and Drug Use and Clarification Act (AMDUCA). (See also Ectoparasiticides and see Anthelmintics.) The Food Animal Residue Avoidance Databank (FARAD) can be consulted for extra-label drug use recommendations and calculated meat and milk withdrawal times.
Hot lime sulfur spray or dip is labeled for use against sarcoptic, psoroptic, and chorioptic mites in sheep. Treatment should be repeated every 12 days if needed. Certain formulations of permethrin sprays are labeled for mange in sheep and goats. As with cattle, permethrin is generally not considered the compound of choice, but if used, the animals should be thoroughly wet with the product and re-treated in 10−14 days. Topical treatments are more likely to be effective if sheep are freshly shorn. Oral ivermectin sheep drench is not labeled for treatment or control of mange. Although single doses of oral ivermectin have been shown to reduce the number of Psoroptes ovis mites within 24 hr, a single oral dose is not considered curative. For these reasons, extra-label drug use of macrocyclic lactones in sheep and goats is common. However, practitioners should consider compounds labeled for a large range of species, the production system of the animals treated, and any warnings against use in species not listed on the label. Outside the USA, injectable ivermectin is approved to treat P ovis in sheep at the labeled dosage of 200 mcg/kg, two doses given 7 days apart.
Sarcoptes scabiei var ovis infests sheep, and S scabiei var caprae infests goats, throughout the world. However, S scabiei var ovis is rare in the USA. This mite infests nonwooly skin, usually on the head and face. Typical of scabies, lesions manifest with formation of crusts and intense pruritus. Affected animals have decreased reproduction, meat gain, and milk yield. In goats, S scabiei var caprae is responsible for a generalized skin condition characterized by marked hyperkeratosis. Lesions start usually on the head and neck and can extend to the inner thighs, hocks, brisket, ventral abdomen, and axillary region. Both S scabiei var ovis and S scabiei var caprae are zoonotic. Consistent with other animal variants of Sarcoptes, zoonoses are initiated from direct contact with infested animals but are self-limiting infestations.
Chorioptes bovis infests sheep and goats worldwide. Prevalence of C bovis is more common in rams than ewes or lambs. Infestation of C bovis on goats is fairly common, with most of a herd infested. Distribution of lesions is the same as that in cattle, with papules and crusts seen on the feet and legs. Most sheep are subclinically infested with C bovis. However, C bovis can cause exudative dermatitis on the lower legs and scrota of rams (scrotal mange). Semen quality may be affected, presumably due to increased temperature of infested scrota.
Psoroptes ovis is a highly contagious and severe infestation of sheep. This mite has been eradicated from sheep in Canada, New Zealand, and the USA. However, sheep scab persists in many countries, including some in Europe. Intense pruritus leads to large, scaly, crusted lesions that develop in more densely haired or woolly parts of the body. Lesions begin on the back and side but may become generalized and cover a large portion of the body. Animals bite, lick, and scratch in response to the pruritus, which results in wool loss and secondary bacterial infection. If affected sheep are not treated, infested animals may become emaciated and anemic and possibly die.
Psoroptic mange (ear mange) in goats and sheep is caused by P cuniculi, which is likely a variant of P ovis. P cuniculi typically infests the ears of goats but can spread to the head, neck, and body. Infestation of P cuniculi in goats can be common, with 80%–90% of a herd infested. Disease can range from subclinical to scaling, crusting, inflammation, alopecia, ear scratching, head shaking, and rubbing of ears and head to alleviate irritation. Although the course is chronic, the prognosis is good with appropriate treatment.
Demodex ovis infests sheep, and D caprae infests goats. Demodectic mange in sheep is not common, whereas D caprae are relatively common in goats. Lesions are similar to those in cattle. In goats, nonpruritic papules and nodules develop, especially over the face, neck, shoulders, and sides or udder. Demodectic mange in goats occurs most commonly in kids, pregnant does, and dairy goats. The nodules contain a thick, waxy, grayish material that can be easily expressed; mites can be found in this exudate. The disease can become chronic. Historically, in some cases, localized lesions in goats have been managed by incision, expression, and infusion with Lugol’s iodine or rotenone in alcohol (1:3). This practice should not be continued or condoned. Rotenone, a plant-derived ketone once a popular pesticide and ectoparasiticide approved for use in organic farming, is now available only as a piscicide in the USA and Canada.
Psorobia ovis (formerly Psorergates ovis) is a common skin mite of sheep in Africa, Australia, New Zealand, and South America. Most infested sheep are not affected. However, intense generalized pruritus and scaliness, with matting and loss of wool can result from infestation with P ovis. All breeds of domestic sheep are susceptible. Because of their small size, the mites are difficult to find in skin scrapings. This disease can cause significant economic losses through weight loss and wool damage. Treatments effective against sarcoptic, chorioptic, and psoroptic mange in sheep are expected to be efficacious for psorergatic mange.