Sarcoptes scabiei

Morphology
1. Small roughly circular mites. Females about 500 microns in diameter, Gnathosoma visible above

2. Large number of triangular denticles on the dorsal of the idiosoma

3. Legs appear paired anteriorly and posteriorly. Anterior legs are visible from the dorsal side but the posterior legs cannot be seen

4. Females have suckers on long unjointed pedicles on legs I and II

5. In the male legs I and II and IV end in suckers and leg III in setae

Hosts
It is generally accepted that there is a single species with a wide range of hosts. Some list these as different varieties e.g. Sarcoptes scabiei var. bovis, Sarcoptes scabiei var. canis and other as separate species eg. S.bovis, S.canis, S.suis, S.equi.

Life cycle
The newly fertilized female burrows into the horny layer of the skin and goes no deeper. Within hours of beginning to burrow she lays eggs singly at a rate of 2 per day for about 2 months.

The eggs hatch after 2 days and the hexapod larvae either leave the burrow or remain in it and moult into nymphs. Larvae on the surface enter hair follicles and moult to protonymphs and form a new burrow.

The protonymphs moult into deutonymphs which may remain in old burrow or form a new one and subsequently moult. Adults mate on the surface and the male remains on the surface. After mating the female forms a permanent burrow.

The life cycle is complete in 10-14 days. Transmission probably takes place via the newly fertilized females, before they start burrowing and can move fairly rapidly.Geographic distributionSarcoptes scabiei is a cosmopolitan species. It is common on both animals and humans in South Africa.

Distribution on hosts·
Humans: Webs of the fingers, wrists, arms, insteps, genitals and buttocks· Dogs: Stomach, hock, root of tail, head, muzzle. Intense pruritus, red spots like flea bites, papulets, yellowish crusts, skin thickened·

Cattle: Flank, tail root, legs and neck·

Pigs: Behind and on ears, back, inner thighs, around the eyes. Hypersensitivity and pruritis.· Goats and hairy sheep: muzzle, abdomen and goats may die· Horses: head and neck·

Rabbits: starts on legs, spreads to nose where crusty protuberance develop and they may die.

Economic importance and diseases caused.

Itching, severe irritation and exudation and there is a forming of a thickened crust on the surface. There is also loss of hair and the skin thickens where infestations are severe.

Economic Period.

Infestations are usually seen towards the end of winter.

In addition, for the sake cat pet owners, mites on cats: The cat scabies mite is known as Notoedres cati and is similar to the S. scabies.

1. They are small (0,5mm), anus situated, dorsally and not terminally.
2. Dorsal surface without spines but has a scale-like pattern on integument.
3. Anterior pair of legs visibly and not dorsally, but not posterior pairs
4. Suckers on long stalks

Hosts
Cats, sometimes dogs and also man.

Life cycle and disease caused.

Burrows in the skin of the face and ears where it cause mange like legions. May spread over the head and along the back. Thickening of the skin, hair loss and grey in colour.