Sarcoptes species — pigs

Adult mites of the genus Sarcoptes live in the stratum corneum of the skin of pigs.


Summary

Adult mites of the genus Sarcoptes live in the stratum corneum of the skin of pigs. The entire life cycle occurs on the host. Clinically, sarcoptic mange (scabies) is characterised initially by intense pruritus and erythema and papulocrustous eruptions, and later by a range of pathological changes in the skin including particularly epidermal hyperplasia. Mites can often be recovered from the ears of pigs although other areas of the body can be affected. Sarcoptes mites are transmitted most often by direct contact between hosts, although fomites can be involved. The infestation is highly contagious. There is still unceratinty regarding taxonomy and host specificity within the genus Sarcoptes. There are a number of products approved in Canada for the treatment of sarcoptic mange in pigs.  Most likely each host species has a species/subspecies/strain, but some of these can infest other species of host. For example, Sarcoptes mites from pigs can infest people, and the reverse may also occur. People also have their own Sarcoptes.

Taxonomy

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, and on pigs and people. Sarcoptes on other susceptible domestic animal hosts, for example cattle, horses and 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.

Morphology

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.

Host range and geographic distribution

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 it is of primary importance in dogs and pigs.

Life cycle - direct

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

Epidemiology

Sarcoptes mites spread easily among their hosts by direct contact and also, to a lesser extent, by fomites. In pigs these would include pens and perhaps bedding. The mites 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.

Pathology and clinical signs

The primary clinical sign is intense pruritus, which is largely immune-mediated. The itching causes the pigs to seek relief, and this may result in hair loss from rubbing and sometimes severe skin damage. Any area of the body may be affected, and mites in affected pigs can often be recovered from the ears.

Diagnosis

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.

Treatment and control

Products containing doramectin (DECTOMAX), ivermectin (VARIOUS) and malathion (MALATHION 50 INSECTICIDE) are approved in Canada for treatment of sarcoptic mange in pigs. It is very important to isolate infested animals, and to treat all pigs at risk.

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

Public health significance

Sarcoptes mites from animals can establish on people (especially from dogs, and much less commonly pigs), although such infestations are usually short-lived.
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