How to Diagnose Watery Mouth in Lambs

Welcome back to our blog! You may have seen the recent ‘On the Hoof’ article about neonatal clostridial disease in lambs, covering lamb dysentery and pulpy kidney disease. Today, we're looking at another common neonatal condition of lambs and kids: watery mouth disease, also known as E. coli endotoxaemia.

Understanding watery mouth disease

Watery mouth disease is a condition that primarily affects lambs between 24 and 72 hours old. It's closely related to colisepticaemia, and from a practical standpoint, these conditions often overlap. The root cause is typically inadequate colostrum intake, which is more common in twin or triplet lambs, especially those born to ewes in poor body condition.

Diagnostic challenges

Diagnosing watery mouth disease can be surprisingly tricky. Unlike other conditions, there are often no distinct gross postmortem findings. Lambs affected by this disease do not show signs of diarrhoea but may exhibit ptyalism (excessive salivation), dehydration, and sometimes retained meconium. The disease is also known as 'rattle belly' due to the distended abomasum and small intestine. Histopathology may reveal signs of toxaemia in some cases, but often, there is little to see.

Culturing E. coli

Submitting samples to confirm a diagnosis is typically not indicated. However, culturing E. coli from multiple systemic sites such as the liver, spleen, and kidney can be supportive if there is profuse, pure growth. It's essential to avoid contamination during this process. Since E. coli is a commensal organism in the GI tract, cultures from abomasal or faecal samples are not diagnostically useful. Pure growths from intestinal content may be significant, but their diagnostic value can be hard to determine.

Blood collection and ZST test

Collecting blood during a postmortem exam or from cohort animals can provide valuable diagnostic information. One of the most useful findings in investigating neonatal deaths is a low Zinc Sulphate Turbidity (ZST) test result, indicating failure of passive transfer. This can be a crucial indicator in understanding the causes of neonatal mortality.

Antibiotic sensitivity and management

In 2016, SRUC Veterinary Services reviewed antibiotic sensitivity results for 295 isolates of E. coli from lambs less than four weeks old:

• 52.5% of isolates were resistant to oxytetracycline
• 41.2% were resistant to ampicillin
• 29.8% were resistant to spectinomycin
• 25% of isolates were resistant to four or more antibiotics.

Using prophylactic antibiotics for watery mouth cases is inappropriate. In outbreak situations, the focus should be on improving hygiene and neonatal care to prevent failure of passive transfer. If metaphylaxis is justifiable, antimicrobials may be prescribed under the cascade. Many flocks have successfully reduced oral antibiotic use in lambs by enhancing hygiene, colostrum management, and ewe nutrition.

Conclusion

Diagnosing watery mouth disease in lambs requires a nuanced approach. While culturing E. coli and blood tests can provide supportive information, improving overall flock management and neonatal care is crucial in preventing this condition. By focusing on hygiene, colostrum intake, and ewe nutrition, we can make significant strides in reducing the incidence of watery mouth disease.

For monthly and quarterly disease surveillance reports from SRUC, visit www.sruc.ac.uk/vets

Posted by SRUC Veterinary Services on 10/04/2025