Important respiratory diseases

Dear Prof McCrindle,

I farm in Tshapfutshe near Beitbridge in Zimbabwe. Please would you explain what is meant by lung sickness and respiratory diseases in small stock? And how do I treat them? Kind regards,

Langalanga Farming

Dear Anonymous,

Respiratory diseases, including lung sickness, can be caused by viruses, bacteria, protozoa or even parasites. In general, the best way to prevent pneumonia is to keep your small stock warm and dry, vaccinate them regularly and control parasites.

The treatment of respiratory diseases in sheep and goats depends largely on the cause. For example, high levels of intestinal parasites such as roundworm, tapeworm or coccidia can reduce immunity to bacteria and viruses, causing pneumonia. External parasites such as botflies lay their eggs in the nostrils of the animals, and the larvae can cause breathing difficulties, which may lead to pneumonia. Ivermectin is an effective treatment.

The main cause of pneumonia in sheep and goats is pasteurellosis, caused by the bacterium Pasteurella (Mannheimia) haemolytica. Stress and cold lower immunity, enabling the bacteria to multiply in lung tissue. As a result, outbreaks often follow exposure to cold, wet weather, particularly after shearing or weaning. Affected sheep and goats breathe with difficulty, or cough, and their mucus membranes may look blueish. On post-mortem, large red patches are seen in the lungs (hence bontlong in Afrikaans).

Fortunately, a vaccine is available, and lambs or kids should be vaccinated for the first time at six months of age, then annually in autumn. Never treat pasteurellosis with tetracycline, as this can produce fatal shock. The antibiotics of choice are injectable sulphonamides, enrofloxacin or penicillin registered for use in sheep and goats. Enrofloxacin (Baytril) and penicillin can only be prescribed by a veterinarian. Vitamin B12 can also be injected intramuscularly to increase oxygen levels in the red blood cells. Gently wash out the animals’ nostrils so that they can breathe.

Corynebacterium pseudotuberculosis can cause respiratory disease. It results in abscesses in the skin, lymph nodes, and sometimes the lungs, but it is seldom fatal and a vaccine is available.

Chronic pneumonia caused by the Maedi-visna lentivirus is called lung sickness, jaagsiekte or pulmonary adenomatosis. Infected sheep or goats lose condition, and have difficulty in breathing if chased. The animals get weaker and many die, usually at about four years of age. Survivors remain carriers for life. Transmission is through close contact, for example via droplets of nasal mucus. Infected ewes can also infect newborn lambs through their colostrum. A post-mortem typically reveals enlarged, firm lungs that are pale in colour.

Kind regards,

Prof Cheryl McCrindle

Source: MacKay, E. 2022. ‘Overview of Respiratory Diseases of Sheep and Goats’. MSD Veterinary Manual. msdmnls.co/3oYyd8k.

Cheryl McCrindle is an emeritus full professor in the Faculty of Veterinary Science at the University of Pretoria, and has extensive experience in animal health. Email her at farmersweekly@caxton.co.za. Subject line: Ask our vet.