GF Bath & SO Vermeulen
A survey shows widespread occurrence in Angora goat flocks.
A QUESTIONNAIRE to determine the extent, occurrence, economic losses and possible contributory causes of swelling disease among Angora goats sent to Angora goat farmers has brought important new information and facts to light. Out of a total of 133 respondents, 104 (78 per cent) indicated that this disease occurred in their Angora goat flocks.
Although the incidence figure is very erratic and the economic importance of swelling disease is generally very slight, in certain flocks it affects up to as much as 50 per cent of the herd.
Because swelling disease is limited exclusively to Angora goats, it is found principally in the Eastern Cape. The disease, however, occurs throughout the year, under all climatic, soil and weather conditions.
Swelling disease is characterised by the sudden development of oedema (dropsy), which can persist for a period of from 2 to 14 days. The swelling is pronounced on the underside of the neck, chest and abdomen. It also occurs in the legs, especially at the joints, but never includes the scrotum or udder. The swelling is cold, painless and remains indented when pressed and varies in degree in the various parts of the body. When the skin is cut or punctured with a needle, clear liquid flows out freely and does not congeal.
Affected animals do not have a temperature, and the pulse, heartbeat and breathing show no abnormalities. Other symptoms include swollen (oedemous) lymph glands, slight listlessness and loss of appetite with consequent loss of mass, as well as diarrhoea in some cases. The percentage of animals affected in a flock varies from less than one per cent to more than 50 per cent, but is usually less than 10 per cent. The percentage of deaths is mostly lower than one per cent. However, if pneumonia or heavy worm infestation occurs at the same time, a higher percentage of deaths can be expected.
Moderate to pronounced subcutaneous oedema, as described under "symptoms", is observed, as well as oedema of the muscle septa in the mesenterium (broad band from which the intestines hang), as well as in the wall of the abomasum and the small intestine. Abnormal amounts of fluid also occur in the abdominal cavity, heart sac and chest cavity. Contrary to the case with the subcutaneous fluids, these fluids do congeal when allowed to stand for a time.
Lymph nodes are swollen and oedemous and often have a ring of pinpoint bleeding at the cortex-marrow junction. The spleen is sometimes slightly enlarged and some minor damage to the liver and kidneys is sometimes observed.
The precise cause or causes of swelling disease are still unknown. However, a good deal is already known regarding some of the factors that are connected with the occurrence of the disease:
- The disease occurs virtually exclusively in Angora goats.
- Swelling disease is most commonly found among stud goats.
- The disease is seldom found in kids before weaning. Most cases appear between the age of weaning (4 to 5 months) and the age of 18 months, but can sometimes also occur in older goats.
- There is almost always a history of non-specific stress conditions e g dipping, dosing, shearing, transportation, change of grazing and excessive handling before an outbreak of the disease.
Conditions under which swelling disease is often found include the following:
- The presence of open water sources such as swamps and springs.
- High concentration of animals, for example on high carrying capacity pastures.
- Infestation with internal parasites.
Swelling disease has already been experimentally caused by dosing animals with Brown stomach worm (Oestertagia circumcincta) larvae. The symptoms of swelling disease are, however, not always positively connected with the presence or number of brown stomach worms or other internal parasites.
The blood protein level (total plasma proteins) of affected goats is always lowered, and it is mainly the albumen part that is affected. It would appear that this lowered albumen concentration in the blood, probably the result of internal parasites, is the underlying cause of the disease. Undefined stress factors are probably responsible for triggering off an outbreak of the disease.
Because the cause is largely unknown, no specific treatment can be prescribed. Symptomatic treatment, such as dosing with worm remedies; treating coccidiosis, if it is a problem; supplementing with additional proteins; and possibly treating with diuretics sometimes has a positive effect. In many cases, however, goats recover spontaneously after a few days having received no treatment. Good care and treatment of the affected goats is nevertheless always advisable to avoid losses from secondary causes.
The following preventative measures are recommended:
- More intensive and better planned dosing programmes, in respect of both Round worms and coccidiosis. With regard to Round worms, special attention must be given to the Brown stomach worm.
- Eliminate stress factors as far as possible, for example cold and hunger or low nutritional level.
- Provide protein supplements and dry hay for goats on green pastures.
- Pay special attention to the care of young animals specifically with regard to general parasite control and nutrition. This is particularly important during shearing and cold weather conditions.
- Avoid a high degree of interbreeding, especially within a closed stud with small numbers of stud animals.
If the average percentage of goats which are affected annually (approximately 3 per cent) and die (approximately 0,6 per cent) as a result of swelling disease is taken into account, together with the estimated loss in condition and loss of mohair production, the actual economic importance of this disease is slight.
It would appear that other diseases that are confused with swelling disease e g infections which cause swelling, as well as secondary complications of swelling disease e g pneumonia, are of more importance with regard to actual losses than swelling disease itself. Nevertheless, swelling disease remains a troublesome problem, especially at shearing time and the general handling of the animals, and for this reason it deserves further investigation. In addition, such investigations may possibly throw more light on the sensitive physiological composition of the Angora goat.