Sarcoptic Mange

The life cycle

This is direct and takes 14-15 days from adult to adult to complete. Fig.11-15.

The mite spreads directly from pig to pig, either by close skin contact or contact with recently contaminated surfaces. The boar helps to maintain infection in the herd because he is constantly in direct skin contact with breeding females and he remains a chronic carrier. If pigs are housed in groups there is increased opportunity for spread. The mite dies out quickly away from the pig, under most farm conditions, in less than five days. This is an important factor in control. If a herd is free from mange, it is one of the easiest of diseases to keep out because it can only be introduced by carrier pigs. However, once it is introduced it tends to be come permanently endemic unless control measures are taken.

Acute mange: The skin is covered by minute red pimples. Thick crusty deposits in the ear

Clinical signs

Acute disease
The common signs are ear shaking and severe rubbing of the skin against the sides of the pen. Approximately three to eight weeks after initial infection the skin becomes sensitised to the mite protein and a severe allergy may develop with very tiny red pimples covering the whole of the skin. These cause intense irritation and rubbing to the point where bleeding may occur. Head shaking is a common symptom and hairs are often rubbed away leaving bare patches. The incubation period to the appearance of clinical signs is approximately three weeks although it may be several months before signs are noticed in large pig populations, particularly in feeder pigs housed in pens with solid partitions.

Chronic disease
After the acute phase thick asbestos-like lesions develop on the ear, along the sides of the neck, the elbows, the front parts of the hocks and along the top of the neck. (Fig.11-16).

Diagnosis

Persistent skin irritation with small red spots on the skin developing into asbestos-like thickening suggests the presence of disease. The skins of pigs can also be examined at slaughter for evidence of the small red pimples. Herds with active disease always show a high level of grade 2 or grade 3 lesions (Fig.11-17). Average grade scores at slaughter indicate the degree of infection and its economic significances. Diagnosis is confirmed by demonstrating the presence of the mite. To do this scrapings are taken from suspicious lesions on the skin and particularly inside the ears. A teaspoon is an ideal instrument to scarify material from the interior of the ear. This material can be spread onto a piece of black paper and left for ten minutes. Mange mites which are rounded in shape and only 0.5mm in length may be just visible to the naked eye. However to positively identify the mite the scrapings should be submitted to a laboratory for microscopic examination.

Serology - The ELISA test is a very specific test for detecting antibodies to the mange mites with an 80% sensitivity in growing pigs but less in sows. Following an eradication programme the ELISA test can be used to confirm the success, however wait at least 12 weeks and test weaners of at least this age as sow antibody levels may persist for up to a year. The ELISA test is also of value in confirming mange free herds.

Average grade score of pigs examined at slaughter

• < 0.3 - Very low level, unlikely to be mange. Other factors such as fly bites can cause similar lesions.
• 0.5 - Disease well controlled no economic effect.
• 1 - 1.5 - Active disease, considerable irritation and rubbing.
• 2+ - Severe disease; expect losses of 0.1 in feed efficiency and 7-10 days extra to slaughter.

Similar diseases

Hyperkeritinization; Note flakey skin, not to be confused with Mange

Mange can be confused with the normal dead scurf of the skin (hyperkeratinization - see photo) that is often seen over the back and the neck but this flaky material can be rubbed away leaving normal skin beneath. The mange scabs on the other hand penetrate the skin surface, are not easily removed and skin damage is evident. Other diseases that might be confused with mange include greasy pig disease, swine pox and sun burn. Occasionally in mange free herds ear scrapings may reveal mite eggs and mites but no clinical disease. Such mites are indistinguishable from porcine Sarcoptes scabiei. This particularly occurs in pigs bedded on old straw that has been contaminated by other animals such as rats or birds with their own host specific mites. Such mites do not survive long or cause disease in the pig.

Hog Lice

Hog lice are bluish-black to brown with a black head and tail end. Adults range up to 1.4-inch long. Immature lice (nymphs) look much like the adults but are smaller. Adults and nymphs pierce the skin several times daily to suck blood. Crawling around on the hosts body and feeding produce irritation and itching. Hog lice may transmit eperythrozoonosis and possibly other swine diseases. Female lice live three to four weeks after reaching adulthood, and lay up to 90 eggs apiece. The yellowish-white eggs are attached to hair shafts or bristles and are easily seen. Eggs hatch in 12 to 20 days. Nymphs grow rapidly and may mature, mate, and begin laying eggs in as little as 12 days after hatching. Hog lice primarily spread by pig-to-pig contact. Lice that come off one host may infest another, but they seldom if ever survive more than three days off the host. In diagnosing swine for lice, look for the lice and their eggs, especially on and inside the ears, under the neck, and in the leg axillae or flanks. You may notice pinpoint reddened areas from feeding punctures. With prolonged infestations, the skin may become cracked, tender and sore. Swine behavior and skin condition caused by lice and sarcoptic mange are somewhat similar, and hogs often have lice and mange simultaneously.

DESCRIPTION

Egg -- The egg, called a nit, is glued to a hair bristle near the base. Eggs are 1.5 to 1.75 mm long and 0.5 to 0.75 mm wide. Pearly white when first laid, eggs soon become amber.

Nymph -- Nymphs are pale yellow with brownish mouthparts and claws. Nymphs resemble the adults in shape but are smaller.

BIOLOGY

Host -- Hog lice infest only wild and domestic swine.

Damage -- Hog lice irritate their hosts by taking small but frequent blood meals. Attempting to relieve the irritation, infested swine scratch themselves or rub against any available object, thereby injuring their skin and hair. In severe cases, hogs may eventually rub most of the hair off their bodies. Heavy infestations of hog lice arrest the growth of young pigs.

Life History -- The entire life cycle is spent on the host. Adult lice are frequently found in the folds of the neck and jowls, inside and at the base of the ears, on the inside of the legs, and on the flanks and backs of hogs. Most of the nymphs occur on the head region.

After feeding and mating, each female lays three to six eggs per day and about 90 eggs in all. Eggs are deposited along the lower half of the sides, on the back of the ears and on the neck, the shoulders, or the flanks. They hatch in 12 to 14 days, though in cool weather they may take 20 days. The young lice molt 3 times in 10 to 12 days as they grow. Feeding takes place in the more tender areas of the body. Hog lice are mature and ready to lay eggs about 12 to 14 days after hatching. The entire life cycle, from egg to egg-laying adult takes from 20 to 48 days. Six or more generations may be completed each year.

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