CATTLE DISEASE

Bovine Besnoitiosis

Bovine besnoitiosis is a disease of cattle caused by a protozoal organism called Besnoitia besnoiti.

Countries outside of Europe where this disease is present include Africa where it is widely distributed. Bovine besnoitiosis has recently been classed as an emerging disease in western and central Europe, due to a recent increase in reported cases and a geographic expansion of the disease in cattle herds in continental Europe.

The disease has been present in some parts of France, Spain and Portugal for many years. More recently, disease has been confirmed in a beef cattle herd in Germany, after cattle were imported from France. The disease has also been reported in Italy. Imported cattle from affected areas may pose a potential threat to countries where the disease has not been registered. This disease is not subject to statutory control in Europe. The disease results in both systemic and skin clinical signs.

Clinical signs in the acute phase

• Initially fever, which may reach 40-41OC and can persist for a week or more.
• Progressive inappetence and listlessness/weakness.
• Slow gait if forced to move or reluctance to move.
• Nasal and ocular discharges.
• Redness of the skin, particularly of the muzzle, skin around the eyes and scrotum of light skinned animals. Accumulation of fluid varies from a slight swelling of the face to thickening of the skin folds over the neck, back and chest or even subcutaneous oedema over the entire body in severe cases.
• Orchitis (inflammation of the testes) leading to swelling and sensitivity on palpation in bulls.
• Swelling of the superficial lymph nodes.
• Intolerance of light.
• Increased respiratory and heart rate.
• Less commonly seen are diarrhoea and abortion.

These signs have usually disappeared by the third week and there may be a break in some cases before the more advanced or chronic lesions develop.

Clinical signs in the chronic phase

• Progressive thickening, folding or wrinkling of the skin.
• Progressive hair loss.
• Dermatitis (inflammation of the skin).
• Hyperkeratosis (thickening of the outer layer of the skin).
• Scleroderma is a typical finding with the disease which is also sometimes called ‘elephant skin’ and usually occurs several weeks after the initial fever.
• Lesions may be widespread or localised although the skin on the legs is more often hard and may be very thickened, leading to slow and restricted movements in some. Skin lesions are also seen around the neck, shoulders and rump and the skin on the udder or scrotum and eyelids may be affected.
• Parts of the outer layer of the skin may be shed leaving greyish, hairless areas. There is often an exudate from the skin, which can dry to form large scabs, and deep raw fissures can form in the skin of the breech and over bony prominences.
• The superficial lymph nodes are almost invariably enlarged.
• Cysts can be seen in the sclera, conjunctiva and the vulval mucosa several weeks after the initial fever.
• A mucopurulent nasal discharge may be seen in some cases, and the crusts can block the nostrils.

Diagnosis

During the first weeks of infection acutely affected animals may be difficult to diagnose as clinical signs are non-specific. Characteristic clinical signs tend to be seen with the chronic stage of disease, with the development of tissue cysts.

In most affected herds, the prevalence of infection is high but the prevalence of clinical signs is low (i.e. most infected cattle do not show clinical signs).

There are currently no effective drugs or vaccines available in Europe.

Diagnostic approach

• Clinical examination can allow a tentative diagnosis, particularly if scleral/vaginal cysts are seen.
• Laboratory examination of peripheral blood smears and smears of lesions may be useful.
• Other skin diseases should be ruled out.
• Punch biopsy of skin lesions can be carried out for histopathology.
• Serological confirmation and PCR confirmation.

Epidemiological features

The routes of transmission and risk factors are unknown, however horizontal direct and indirect transmission seem responsible for the spread.

Biting arthropods, such as horseflies and deerflies, have been implicated as mechanical transmitters of the infection, from chronically or subclinically infected cattle. The potential for wild ruminant and rodent reservoirs has been suggested. The definitive host for Besnoitia besnoiti remains unknown.