Pregnancy Toxaemia

Also known as:

Twin Lamb Disease

Description

A disease affecting ewes during the last few weeks of gestation. Mainly affects twin or multiple bearing ewes. The condition occurs when the ewe does not recieve an adequate energy supply during a time when the rapidly growing foetuses drain carbohydrate stores. This results in a sub-clinical ketosis which can quickly progress to a clinical pregnancy toxaemia. It is a serious condition which can be fatal and most frequently affects lowland flocks.

Very similar to ketosis in cows.

Signalment

It is seen more frequently in older ewes and those carrying multiple lambs who are in poor body condition score.

Diagnosis

Can often be diagnosed on history and a clinical exam.

Differential diagnoses include listeriosis, pneumonia, and hypocalcaemia.

Clinical Signs

Mainly neurological signs are apparent as a result of the hypoglycaemic state of the animal. Ewes are often depressed and not aware of their surrounding, they can adopt an unusual posture which may progress to ataxia or recumbency. Some appear blind and there may be trembling and twitching of the face and ears. Ewes often grind their teeth and make chewing movements. They are also anorexic and may have breathing difficulties and a nasal discharge. Some ewes abort which may result in septicaemia.

Laboratory Tests

Biochmeistry will often reveal a hypoglycaemia and a hyperkalaemia due to ketoacidosis. Additionally a high ß hydroxybutyrate (BHB) (which is one of the ketone bodies) level will also be evident. BHB is a more reliable measure of disease as not all animals show hypoglycaemia on blood work and some even are hyperglycaemic.

On urine analysis ketones may be present.

Treatment

Treatment of advanced cases of pregnancy toxemia is often unsuccessful. Propylene glycol can be given orally that acts as a precursor to glucose. The addition of calciumm, potassium and insulin is also useful. Hypoglycaemia can also be treated by administering IV dextrose, follwed by an oral electrolyte solution.

If biochemistry reveals a hypocalcemia, this can be corrected by giving calcium IV. Severe ketoacidosis can be treated by administering oral potassium chloride (KCl). The contributing factors (eg, nutrition, housing, other stressors) should be corrected for the group and feeding management assessed (eg, adequate feeder space, feeding frequency, protection from adverse weather).

A blood sample should be taken from a number of ewes in late gestation and glucose and BHB levels measured. This will determine if there are any problems in the rest of the flock.

If it is thought that the ewe has aborted then prophylactic antibiotics should be administered. If foetuses are alive a caesarian section should be considered.

Prevention

Ewes should be in a good body score at tupping and should maintain a good body condition score throughout gestation. Good body condition can be maintained by good mangement of feeding. Ewes should recieve grain as a carbohydrate source and also a protein source so that the rumen microbes can make use of the carbohydrate. It is also important to separate out thin sheep and feed them seperately from the main flock. Ideally ewes should be ultrasound scanned to determine the number of foetuses they are carying and then separated into groups and fed accordingly.

Prognosis

Often fatal

References

Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial