Elephant Skin Disease (Besnoitiosis)
Elephant Skin Disease, or Besnoitiosis, is a disease of the skin, subcutaneous tissue, blood vessels, mucous membranes and other tissues caused by a protozoal parasite. It affects cattle, horses and donkeys and several species of wildlife. Goats occasionally get the disease. The affected animals are intermediate hosts. The final host of the organism responsible for disease in cattle is the cat. That of the horse is presently unknown. The disease occurs worldwide.
Mode of spread
Besnoitia besnoiti is the parasite responsible for the disease in cattle and various African wild ruminants and Besnoitia bennetti is responsible in horses and donkeys. The final hosts excrete Besnoitia oocysts in their faeces, which are then ingested in contaminated feed or water by the intermediate host. For the cycle to be completed in the case of cattle, a cat has to eat cysts that have been formed in the tissues of an infected cow.
The disease may also be spread mechanically by biting flies, such as tsetse flies, or by needle transmission.
Signs of Elephant skin disease
Bovine besnoitiosis occurs in cattle over six months old. The disease occurs in two stages.
- About a week after infection, affected animals may have a high fever up to 41.67 °C
- They display photophobia (avoidance of direct sunlight)
- Odema (swelling) of the skin with warm painful swellings on the abdomen interfering with movement
- Lack of appetite, nasal discharge, diarrhoea and enlargement of superficial lymph nodes.
- Inflammation of the testicles and sterility may occur in bulls.
- Small cyst like structures may appear in the whites of the eyes. These are considered to be diagnostic.
- Up to 10% of affected animals die in the early stage.
- Survivors develop a chronic disease in which the parasites are in cysts underneath the skin. These cysts contain thousands of parasites.
- The skin becomes hard, thickened and wrinkled and the hair may fall out.
- Denuded areas of skin become scurfy, cracked, secondarily infected and fly-blown.
- Death occurs in severe cases.
- Recovered animals remain permanent carriers of cysts which contain numerous parasites.
- Cysts may develop in the eyes.
- Chronic damage and calcification of the testicles may occur.
- Severely affected animals become emaciated and bulls permanently sterile.
- Goats have lumps in their ears and around the genitals. They have white patches on their eyes.
- Pregnant goats abort and many become infertile. New-born goats are weak and some die.
The early stage of the disease can be confused with Malignant Catarrh. The later stages must be differentiated from skin conditions such as Lumpy Skin Disease, Photosensitization, Streptothricosis, Mange and Sweating Sickness.
Prevention and Control
- Separate sick animals from healthy ones.
- Control flies and ticks
- A live tissue culture vaccine has been developed in South Africa which gives good results, although it does not prevent infection.
There is no specific therapy but treatment of symptoms may be applied. Oxytetracycline appears to have some effect if given in the early stages of the disease.