Animal Health: Diseases and Parasites

What you need to know

• A healthy animal is alert, feeds well, has a smooth glossy coat, bright eyes, a moist muzzle, normal dung and urine, steady weight and steady milk or egg output. Signs of ill health are dullness and separation from the herd, loss of appetite, a rough staring coat, nasal or eye discharge, diarrhoea, coughing, abnormal temperature, lameness and a sudden drop in production.
• Normal body temperatures worth memorising are cattle about 38.5 degrees Celsius, sheep and goats about 39 degrees Celsius, pigs about 39 degrees Celsius and poultry about 41 to 42 degrees Celsius. A reading outside the normal range is one of the first objective signs of disease.
• Newcastle disease is the most destructive viral disease of Nigerian poultry. It causes greenish diarrhoea, gasping and coughing, twisting of the neck and paralysis, a sharp drop in egg production and mortality that can reach the whole flock. There is no cure, so control is by vaccination: Lasota given in drinking water or by eye drop, and Komarov given by injection to older birds, with strict biosecurity.
• Other important poultry diseases are Gumboro or infectious bursal disease, a viral disease of young birds causing prostration and whitish diarrhoea, controlled by vaccination; fowl pox, giving wart-like scabs on the comb and wattles; fowl typhoid and fowl cholera, bacterial diseases treated with antibiotics under veterinary direction; and coccidiosis, a protozoan disease showing blood-stained droppings in chicks, controlled by a coccidiostat in the feed and by keeping the litter dry.
• Anthrax is a bacterial disease of cattle, sheep and goats caused by Bacillus anthracis, showing sudden death with dark tarry blood oozing from the nose, mouth and anus and failing to clot. It is a zoonosis that kills humans, so the carcass must never be opened; it is burnt or buried deep in quicklime, the area is quarantined and the remaining stock are vaccinated.
• Blackleg or black quarter, caused by Clostridium chauvoei, attacks young cattle, giving lameness, hot painful swellings on the heavy muscles of the hindquarters that crackle under the hand, high fever and death within days. It is prevented by vaccination and by avoiding grazing on known contaminated ground.
• Contagious abortion or brucellosis causes abortion in late pregnancy, retained afterbirth and infertility, and it infects humans through raw milk, so it is controlled by testing and culling reactors, vaccination of heifers and pasteurisation of milk. Contagious bovine pleuropneumonia, caused by a mycoplasma, gives painful coughing, laboured breathing with the elbows turned out and fever, and is controlled by vaccination and movement restriction.
• Foot and mouth disease is a highly contagious viral disease of cattle, sheep, goats and pigs, showing blisters on the tongue, gums, muzzle, teats and between the hooves, with profuse drooling, lameness, loss of condition and a collapse in milk yield. Mortality is low but production losses are severe. Control is by quarantine, restriction of animal movement, disinfection and vaccination.
• African swine fever is a viral disease of pigs with very high mortality, showing high fever, reddening of the skin on the ears and belly, huddling and sudden death. There is no vaccine and no treatment, so control rests entirely on biosecurity, quarantine, a ban on feeding uncooked swill and the slaughter of infected herds. Peste des petits ruminants performs the same role in sheep and goats and is controlled by vaccination.
• Trypanosomiasis or nagana is a protozoan disease transmitted by the tsetse fly, Glossina. It causes intermittent fever, progressive anaemia with pale membranes, emaciation despite feeding, swollen lymph nodes, watery eyes and abortion, and it is the single greatest barrier to cattle keeping in southern Nigeria. Control is by clearing tsetse breeding bush, trapping and spraying the fly, prophylactic and curative trypanocides, and the use of trypanotolerant breeds such as Muturu, N'Dama and West African Dwarf.
• Ectoparasites live on the outside of the animal. Ticks suck blood, cause anaemia, damage hides and transmit babesiosis and anaplasmosis; lice and mites cause intense itching, rubbing and mange with hair loss; fleas, biting flies and the tsetse fly also transmit disease. Control is by dipping or spraying with an acaricide, hand picking, pasture rotation and keeping housing clean and dry.
• Endoparasites live inside the animal. The liver fluke, Fasciola gigantica, needs a water snail as intermediate host and damages the liver of cattle and sheep grazing marshy ground, causing bottle jaw and weight loss. Roundworms, tapeworms, hookworms and lungworms cause pot belly, diarrhoea, anaemia, coughing and stunted growth. Control is by routine deworming, avoiding grazing wet low-lying land early in the morning, draining marshy pasture, destroying snails, and not overstocking.
• Diseases spread by direct contact with sick animals, by contaminated feed, water, litter and pasture, by vectors such as ticks and tsetse flies, by infected equipment and clothing, through the air, through the placenta and through the introduction of new stock without quarantine.
• The general principles of disease prevention are vaccination to a written programme, quarantine of all new and sick animals for at least two weeks, regular cleaning and disinfection of housing and equipment, a foot dip at the entrance to poultry houses, adequate balanced feeding and clean water, correct stocking density, routine deworming and dipping, prompt disposal of carcasses by deep burial or burning, and keeping treatment records. Prevention is cheaper than cure, and many diseases such as Newcastle and African swine fever have no cure at all.