Watery mouth in lambs: arises from a build-up of E coli bacteria after lambing

Cause

Sub-optimum husbandry conditions help the spread of the disease in a lambing flock. Dirty lambing and individual pens, as well as ewes with faecal contamination on their wool, are a hotbed for disease caused by E coli bacteria. If a lamb’s mouth gets contaminated with dung or dirty bedding material before they take in colostrum, bacteria will build up in their intestine, causing illness and, in the majority of cases, death.

The disease develops quickly and affects lambs as young as 12 to 72 hours of age. Once established in a flock, it can quickly spread, and has been known to affect 20-30% of lambs. In a normal lambing, antibodies are ingested through colostrum and provide lambs with a defence mechanism against bacteria. The problem occurs where lambs receive insufficient colostrum or delayed access to colostrum and are also exposed to bacteria in the environment they are born into (bedding, fleece etc). In the absence of sufficient colostrum, bacteria quickly get established in the lamb’s system and there is no immune system there to prevent infection becoming established.

The first lambs to get struck by watery mouth are usually lambs from multiple births (double or triplet-born lambs) because there is more competition for colostrum from the ewe compared with single-born lambs.

Symptoms

Lambs with watery mouth are often difficult to identify early on. In the initial stages of the disease, their intestine becomes overgrown with bacteria and a build-up of partially digested milk becomes trapped, which creates the illusion that their bellies are full. Lambs will frequently be lying in the corner of the pen with full bellies and most farmers who are busy lambing won’t notice they are sick until it is too late.

More obvious signs of the disease include lambs that stop feeding, are dull and weak and have saliva drooling from their mouth. The lamb’s mouth may also be very cold and wet. As the disease advances, a lamb’s stomach may become swelled or bloated. This gives the classical symptom of rattle belly as the lamb will exhibit a rattle sound when shaken gently.

Treatment

For treatment of sick lambs, oral rehydration and the administration of a laxative as soon as possible may help.

Treatment success of infected lambs is dependent on the degree of infection. It involves administering antibiotics daily to treat the infection and electrolytes to prevent dehydration and provide animals with energy. Stomach tubing will be required where lambs have stopped suckling. Lambs may also require artificial heat via a red lamp as their body will find it difficult to generate sufficient heat. Treatment should be continued until lambs are suckling satisfactorily again.

Dead lambs should be sent to a veterinary laboratory for a cultured sensitivity test to assess what strain of bacteria is causing the fatalities, because only then a suitable antibiotic can be chosen to treat sick lambs. However, the PM examination will be of limited value where antibiotics have been administered as the bacteria won’t be cultured.

Prevention and control

One way of preventing the disease is to ensure all lambs receive sufficient colostrum at birth (approximately 50ml/kg in first six hours of life). This may require supplementing twin or triplet born lambs with artificial or stored colostrum.

Hygienic lambing conditions are also a must. The best approach to prevent disease build-up is to clean lambing pens daily but where this is not possible, it is important to apply a disinfectant such as lime or other specially designed powder disinfectants. A good bed of fresh straw is essential and the aim should be to put down a fresh bed every day.

A mistake that is often made even where lambing conditions are hygienic is that feeding equipment is not washed and sterilised between feeds. Bottles, teats, stomach tubes etc should be all thoroughly cleaned to minimise the risk of disease build-up and spread. Once ewes and lambs have developed a strong bond and you are happy lambs are suckling sufficiently, releasing these animals to grass will also help to limit disease risk.

There is a vaccination available for watery mouth that can be given to the ewes one to two weeks before lambing. The vaccine is acquired through passive immunity, meaning vaccination will only be worthwhile as long as lambs are getting enough colostrum.