Sarcoptes species — sarcoptic mange or scabies in cattle

Burrowing mites of the genus Sarcoptes infest cattle, sheep, goats and a range of other hosts around the world.  In Canada sarcoptic mange used to be an occasional diagnosis in cattle, but as it is no longer reportable to the authorities good recent data on its occurrence in this host in this country are sparse.  Sarcoptes infestation are believed to be very rare or absent from sheep and goats in Canada.  It is unclear whether Sarcoptes of domestic animals are all within one species, or whether each host species has its own species, sub-species or strain of parasite.  Cross infection between animal host species appears to be very unusual, but infestation of people with Sarcoptes from animals, especially dogs, does occur.

The whole life cycle of Sarcoptes occurs on the host, although transmission can occur through life cycle stages that survive for short periods (probably days) in the environment.  The primary clinical sign of sarcoptic mange in cattle and sheep is intense pruritus, which may interfere with meat and ilk production, and there may also be scaliness and hair loss, as well as damage to the skin resulting from attempts to relieve the itching.

Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Subclass: Acari
Order: Astigmata (Sarcoptiformes)

As well as the Order Astigmata, the Subclass Acari consists of the Order Ixodidae containing the hard (Family Ixodidae) and soft (Family Argasidae) ticks, and several other Orders (Mesostigmata, Prostigmata and Orbatidae) containing the parasitic and free-living mites. Other members of the Order Astigmata of importance in veterinary medicine include Chorioptes, Otodectes and Psoroptes.

In Canada, Sarcoptes mites and sarcoptic mange are found on dogs and free-ranging canids, on pigs, very rarely on cattle, and on people. Sarcoptes on other susceptible domestic animal hosts, for example horses, sheep and goats, are probably very rare in Canada or do not occur. It is uncertain whether the mites on these different hosts are members of a single species.

Adult Sarcoptes are roughly circular in shape with a diameter of up to approximately 300μm. They are burrowing mites and in the adult stage they have four pairs of legs that barely extend past the body margin. Sarcoptes mites cannot be seen with the naked eye.

Sarcoptes and sarcoptic mange occur in a wide range of both domestic and free-ranging mammals, and in people, around the world. Currently in veterinary medicine in Canada, these mites are of primary importance in dogs and in pigs.

The life cycle of Sarcoptes occurs totally on the host. Adult mites mate in small depressions in the epidermis. Females dig tunnels in the outer epidermal layers where they lay eggs. These hatch to release six-legged larvae, which develop on the skin surface to eight-legged nymphs and then adults. The entire life cycle can be completed in a few weeks.

Life Cycle: Sarcoptes species

Sarcoptes mites spread easily among their hosts by direct contact and also, to a lesser extent, by fomites. In cattle these would include fencing, scratching posts and perhaps bedding. The mites probably cannot survive off the host for more than a few days.

On a global basis, the incidence and severity of human sarcoptic mange seems to follow an approximately ten year cycle, possibly because of the waxing and waning of an infestation-induced "herd immunity". The existence of such a cyclical pattern of disease in domestic animal hosts is less certain.

The primary clinical sign is intense pruritus, which is largely immune-mediated. Any area of the body may be affected, but the face, neck, shoulders and rump often show the most severe pruritus. The itching causes the cattle to seek relief, and this may result in hair loss from rubbing, and sometimes severe skin damage.

The history and clinical signs can be helpful. Recovery of the mites (and eggs) by deep skin scrapings, followed by microscopic examination, is the best method to confirm the diagnosis. Sometimes, however, it may be very difficult to find mites, even in animals with severe clinical signs and skin lesions.

There are several products approved in Canada for treatment of sarcoptic mange in cattle: injectable and topical (pour-on) doramectin (DECTOMAX), and ivermectin (VARIOUS) and topical moxidectin (CYDECTIN) and  eprinomectin (EPRINEX).  Some of these products have milk withdrawal and slaughter delay requirements.  

Additional information on the products mentioned is available from the Compendium of Veterinary Products (Twelfth Edition, 2011), or from the manufacturers.

For control of sacoptic mange in cattle it is very important to isolate infested animals, and to treat all cattle at risk.

 

Sarcoptes mites from animals can establish on people (especially from dogs, and much less commonly pigs), although such infestations are usually short-lived. Cattle, sheep and goats are probably a very rare source of Sarcoptes in people, especially in Canada.