Mites

Psoroptic mange

The structural change in modern animal husbandry creates favourable conditions for the multiplication of ectoparasites such as mange mites, sucking lice and biting lice. The subclinical form of the infestation which reduces productivity considerably, is well recognised.

For this reason the metaphylactic hygiene programme involving the entire herd as opposed to the therapeutic treatment is getting increasingly important.
In the management of livestock both for production and breeding purposes, the parasites mainly responsible for causing mange are Psoroptes, Chorioptes and Sarcoptes mites. The structural change in modern animal husbandry creates favourable conditions for the multiplication of ectoparasites such as mange mites, sucking lice and biting lice. The subclinical form of the infestation which reduces productivity considerably, is well recognised. For this reason the metaphylactic hygiene programme involving the entire herd as opposed to the therapeutic treatment is getting increasingly important.

In the management of livestock both for production and breeding purposes, the parasites mainly responsible for causing mange are Psoroptes, Chorioptes and Sarcoptes mites.

Epizootology of mange and its control

Mange mites are mostly transmitted from animal to animal by contact, and the demonstration of mites in one animal justifies the assumption that the entire herd is infected. Of particular significance is the transmission from the dam to the young and from the male to the female breeding animal.

Infection of a hitherto mange free herd occurs usually as a result of buying-in mite-carrying stock, which often show no clinical symptoms of mange.

Sheds, boxes and pasture fencing must be considered as sources of reinfestation because mange mites are able to survive outside the host.

Reasons for spreading of mange

• Increase livestock trade
• Absence of veterinary regulations for ectoparasite control in the movement of live stock across national borders
• Separation of breeding and fattening farms
• Concentration of animals of different origins in fattening units
• Irregular ectoparasite control
• Ignorance of the clinical picture and negligence in the treatment have survived from mange-free times
• Favourable conditions for the development of mange because of intensive animal husbandry.

Problems in mange control

• Mange mites have areas of retreat on concealed parts of the body such as the thigh folds, under the tail, in ears and fossa infraorbitalis in sheep
• During spraying a strict sequence must be observed
• Start at the head, finish at the tail, and spray all areas of the body thoroughly
• There is no acaricide yet with which the eggs of the mange mites can be reliably destroyed
• A second treatment is necessary to kill the larvae which have hatched from the eggs in the meantime
• The optimal interval between the first and the second treatment is 7 days in psoroptic and chorioptic mange and 14 days in sarcoptic mange
• The mites are often concealed in the crusts and scabs where they are often not reached directly by the acaricide during spraying
• A mange remedy with vapour effect should be favoured
• Thick scabs and crusts should be loosened or removed mechanically with a curry comb before spraying
• Mange mites do not cause visible mange in every animal
• The entire herd must be treated
• In sheep flocks the sheep dogs must also be included in the treatment
• Mange mites survive outside the host
• Animal houses and pasture fences must be sprayed as well
• In late autumn the rapid spread of mange begins.
• A treatment on return from the pasture is therefore advisable, with a repeat treatment after one week indoors.
• Treat bought-in animals twice in the quarantine house before they are allowed to join the herd

Pedicel and sucker of Psoroptes ovis
Psoroptic mange

Psoroptes ovis

Psoroptes mites prefer hairy parts of the body; by piercing the skin and sucking lymph fluid they cause pustules which spread rapidly, burst and form typical yellowish-sticky scabs and crusts.

They are particularly active in the cold season and infest sheep, cattle, especially fattening bulls, and also horses.

Because of the short life cycle the disease develops relatively quickly. The animals suffer from intense itching, become restless, bite and rub the affected parts and the hair or wool becomes detached. In young animals growth is arrested at first, followed by severe emaciation and death if the infestation is heavy. While in the past psoroptic mange in cattle was considered rare, it is today one of the main problems in bull fattening management. Restlessness due to itching and incipient crust formation and loss of hair along the dorsal line are the first signs of Psoroptes infestation in the herd. The disease is usually spread by bought-in cattle; there is evidence that psoroptic mites can be transmitted from sheep to cattle. Off the host psoroptic mites can survive for some time, ranging from 10 days to 6 weeks.

Sarcoptic mange

Sarcoptes mites prefer hairless parts of the body, which is why mange in the pig for example is always sarcoptic mange. The mites burrow tunnels in the skin, suck lymph and feed on young epidermal cells. At first acute symptoms such as skin reddening and pustules are observed on the affected parts of the skin, causing severe itching. Typical signs of advanced sarcoptic mange are thickening of the skin and fold formation (elephant skin). In the pig allergic skin reactions are often encountered which occur after a sensitising incubation phase of approx. 10 days; even a few mites can cause severe clinical symptoms.

Sarcoptes bovis - Sarcoptic mange

In horses and sheep Sarcoptes mites cause the so-called "head mange", in susceptible horses this can spread to the neck and shoulder region. In cattle sarcoptic mange can become a problem particularly in dairy herds, the sites of predeliction being the head, neck and udder.

Sarcoptes mites can also cause mange in dogs and cats. Off the host Sarcoptes mites can survive for approx. 2 weeks.

Chorioptic mange

Chorioptes mites attack by preference escutcheon, fetlocks and the base of the tail, where they chew at the skin surface thus causing inflammations, scaly lesions and a powdery coating. The so-called foot and rump or tail mange can occur in the horse, sheep and especially in dairy cows. Another characteristic sign is the itching which, especially in the horse, leads to a festinating gait.

Chorioptes mites can survive for 3-4 weeks off the host.

Itch mite infestation

Chorioptes bovis Chorioptic mange

Itch mite infestation, or Australian itch, is contagious but slow-spreading and is caused by a very small mite. It is of economic importance in Australia and South Africa. The parasites live in the surface layers of the skin of wool sheep and cause chronic irritation with severe itching which leads characteristic to fleece damage.

Demodectic mange

This is caused by small lancet-shaped follicular mites whose parasitism is not always accompanied by pathological lesions.

These mites are also encountered in healthy animals and man and need additional factors in order to produce clinical demodicosis. The disease has greatest significance in dogs. In other species such as horse, cattle, pig, sheep, goat and rabbit host-specific Demodex species can occur, but they rarely cause disease.

Diagnosis

The clinical symptoms described and illustrated above enable the veterinary surgeon to diagnose mange infestation with a reasonable degree of accuracy.

For parasitological confirmation and species indentification, skin scrapings should be taken with a sharp curette or scalpel from the edge of the mange lesion where it meets the healthy skin tissue and placed into closed glass tubes.

When the tube is warmed with the hands the busily moving mites inside it are often visible with the naked eye or with a magnifying glass. For the microscopic examination of mites particularly in scab samples, the skin scraping can be enriched in 5 ml of a 10% solution of caustic potash (KOH) by carefully heating the tube, decanting the supernatant and placing the sedimented material on a slide for examination.