Page 479 - The Veterinary Laboratory and Field Manual 3rd Edition

416 Susan C. Cork

Table 10.8 continued

Clinical sign Cause Common host/comments
Sheep (sheep pox,
facial pyoderma due to
Staphylococcal infection, blow
fly myiasis, etc.)
Localised lesions Wounds and localized infection All species
Abscesses*

Note: *An abscess is a circumscribed infection which occurs under the skin or in an organ secondary to bacterial infection e.g.
Staphylococcus aureus following damage (i.e. infection/wound).

10.5 Ill thrift and chronic weight loss may also cause poor coat and weight loss in live-
stock (for example, ragwort poisoning in horses
There are a number of causes of poor condition and ruminants). Table 10.9 outlines the common
and weight loss (see section 10.2, diarrhoea). If causes of ill thrift, poor weight gain or weight
only an individual animal is affected the approach loss in livestock. As with any disease problem,
to the case will be a little different to that which the approach to the problem must be thorough.
is required where ‘ill thrift’ affects a whole herd
or flock. In both situations, it is necessary to 1 Take a clinical history. What is the duration of
perform a thorough clinical examination and to clinical signs? Level of morbidity? Mortality?
take a detailed case history. Ill thrift in individual Which age groups of animal(s) have been
animals may be due to a wide range of factors affected? Is there any data from previous
such as poor ability to compete, the presence of health screening or necropsy? What is the
mouth lesions, poor dentition, neoplastic dis- history of the property, that is, records pre-
ease or developmental disorders. If a group of vious trace element deficiencies, presence of
animals are affected it is important to check the toxic plants and so on?
husbandry, that is, evaluate the diet, test for the 2 Perform a thorough clinical examination.
presence of gastrointestinal parasites, examine Always examine the mouth, check faecal
stocking rates and breeding/replacement policy. samples and urine, check for evidence of
Does the animal have a good appetite, and want liver damage (swollen abdomen, jaundice,
to eat? The most common cause of weight loss oedema, anaemia, behavioural changes).
or poor weight gain in livestock is under or Other clinical signs?
malnutrition. Subclinical or clinical disease, for 3 Collect clinical samples (see Chapter 1 and
example, gastrointestinal parasitism may make the outline for a necropsy in Chapter 8 and
the situation worse but the lack of adequate Appendix 2).
nutrients may be the main pre-disposing factor.
Chronic sub-clinical or clinical gastrointestinal In disease(s) characterized by chronic wasting,
parasitism may be a significant cause of ill thrift affected animals are often culled and a necropsy
in young stock. In older animals, chronic dis- can provide valuable information. At necropsy,
eases such as tuberculosis (Mycobacterium bovis) special attention should be paid to the liver
or Johne’s disease (Mycobacterium avium para- and gastrointestinal system. Look for evidence
tuberculosis) may cause weight loss along with of irritation, hyperplasia or focal lesions in the
diarrhoea. Chronic ingestion of toxic substances intestinal tract, and the rumen and abomasum

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