Previous bulletins have detailed the underlying causes of mortality in newborn lambs and ways to reduce losses. In this bulletin specific diseases are discussed in detail including the clinical signs, diagnosis, treatment and control.
Watery mouth disease is a colloquial term (others include rattle belly) used to describe a collection of clinical signs in newborn lambs which includes lethargy, failure to suck, profuse salivation, bloating and retained meconium. The condition is caused by colonisation of the small intestine by E. coli with rapid multiplication and release of toxins.
Initial infection results from a high environmental bacterial challenge from dirty, wet conditions in the lambing shed and pens, and from ewes with faecal staining of the wool of the tail and back end. Colonisation of the gut and rapid bacterial growth is facilitated by inadequate or delayed colostrum intake. These risks are higher in lambs of low birthweight, from ewes in poor condition or ill health, in multiples, following difficult births and due to mismothering.
Figure 1. Lambs with watery mouth are initially dull, lethargic, depressed and reluctant to suck.
Figure 2. Watery mouth disease can quickly progress to coma and death.
Watery mouth disease is commonly encountered in twins and especially triplet lambs aged 12 to 36 hours kept in unhygienic conditions. Affected lambs are dull, lethargic, depressed and reluctant to suck. They frequently lie in the corner of the pen and rarely stretch or show interest in sucking when encouraged to stand. Within 2 to 6 hours there is profuse salivation, a wet lower jaw and increasing abdominal distension, despite the lamb not feeding. The condition can quickly progress to coma and death.
Watery mouth can be diagnosed based on the clinical signs in the live lamb. If there are high levels of mortality, fresh lamb carcasses should be submitted for post mortem examination to confirm the diagnosis. Blood samples from live lambs less than one week of age can also be tested easily to see if colostrum intake was adequate and help identify risk factors which may be contributing to an outbreak.
Despite bloating, lambs with watery mouth disease need oral electrolyte therapy at a rate of 50 mls per kg four times daily to prevent dehydration. During the early stages soapy water enemas such as diluted washing-up liquid, or other laxatives may be used to promote gut activity and expulsion of meconium. Oral antibiotics may be effective during the early phase of the disease but veterinary advice should be sought to ensure treatment protocols are appropriate.
Problems with watery mouth disease are often worse in housed flocks towards the end of the lambing period as the bacterial challenge builds up. All attempts must be made to improve hygiene standards in the lambing shed. Wherever possible, the remaining pregnant ewes should be moved to another building, or weather permitting, turned out to pasture. It is important to ensure lambs receive enough good quality colostrum to ensure adequate immunity.
Routine antibiotic administration to prevent watery mouth disease in lambs is not justified. The industry has targeted stopping antibiotic use for this purpose as part of its commitment to tackle antibiotic resistance. All efforts to prevent the disease should be made and veterinary advice sought if disease outbreaks occur.
Navel ill is common in young lambs born into unhygienic conditions and when there is inadequate navel treatment. It is more common during poor weather and in male lambs because urination delays drying of the umbilicus and removes some of the iodine solution.
Umbilical infections may remain localised and develop into a discrete abscess involving the body wall or they can spread inside the body to involve the abdominal cavity, joints, meninges (brain), lungs, kidneys, and endocardium (heart valves) where the consequences for the lamb may not be fully appreciated until some weeks later after considerable suffering.
Treatment of localised abscesses may be worthwhile but the prognosis for infections of the body cavity, liver, brain and joints is very poor.
Figure 3. The iodine solution has not been correctly applied to the umbilicus which is still wet.
Hepatic necrobacillosis is a fatal condition caused by the spread of an umbilical infection with the bacteria Fusobacterium necrophorum (footrot bacteria) to the liver. Typically, affected lambs are first noted from 10 to 14 days old when they appear dull and depressed, and in poor condition. They have an empty, gaunt appearance and are easily caught in the field. Affected lambs may not follow the ewe and are found sheltering behind walls and hedgerows. They stand with an arched back and all four legs drawn together. Treatment is hopeless.
Septic peritonitis occurs when umbilical infections spread to the body cavity. The clinical signs vary with the extent and nature of the peritonitis. Lambs which develop septic peritonitis within the first five days of life appear very dull and weak. They stand with their back arched and head lowered, and spend long periods lying in the corner of the pen. The rectal temperature may be low. These lambs do not suck but increasing loss of fluid into the peritoneal cavity causes bloating of the abdomen in contrast to the lamb's gaunt appearance. Affected lambs rapidly become dehydrated and die within a few days of clinical signs first appearing. Treatment is hopeless.
Figure 4. Lamb with septic peritonitis appearing very dull, weak and standing with its back arched.
Figure 5. Comparison between a healthy five day-old twin (left) and litter-mate with septic peritonitis (right).
Figure 6. Necropsy of lamb with septic peritonitis - note the large amount of pus (infection) on the left of this image.
Navel ill can be readily prevented through good hygiene and thorough application of 10% iodine solution to the umbilicus as soon as possible after birth. This should be repeated after two to four hours. Antibiotic sprays are not as effective and the use of topical antibiotics for this purpose is not justified.
Figure 7. The umbilicus (navel) must be fully immersed in 10% iodine within the first 15 minutes of life and repeated 2 to 4 hours later.
Localisation of bacteria within joint(s) causes infectious arthritis. This leads to moderate to severe lameness and is a major economic and welfare problem for the industry. Bacteria spread through the bloodstream in neonatal lambs from entry via the gut, upper airways, tonsils, and untreated navels. Bacterial challenge is much greater when lambs are kept in unhygienic conditions with delayed or inadequate colostrum intake.
Figure 8. Bacterial challenge is much greater when lambs are born in unhygienic conditions
Figure 9. Bacteria loads are greater at high stocking density
Joint infections with the bacteria Streptococcus dysgalactiae are acquired during the first few days of life with lameness visible from five to 10 days old. The number of infected joints varies; only one joint is affected in approximately 50 per cent of lambs with two to four joints in the remainder. The joints most commonly affected, with decreasing frequency, are the carpus (the “knee” on the front leg), hock, fetlock, and stifle joints. The affected joint(s) are swollen, hot, and painful. Infection causes considerable muscle wastage due to lack of use of the limb, and after only one week lambs with polyarthritis are smaller than their twin and in poorer body condition.
Figure 10. Severe lameness of the right carpus of 5-7 days duration. The lamb has poor body condition and an open fleece.
Figure 11. Joint ill affecting the right hock (and possibly other joints).
Lameness affecting a single leg may also result from a fracture, a foot abscess, a lesion between the claws, a dog bite or an injury to the joint (where the stifle is most commonly affected).
Diagnosis of an infected joint is based on clinical findings although it may prove difficult to differentiate injuries from early infective conditions. In lambs less than one month-old all lameness and swollen joints should be considered septic until proven otherwise.
Procaine penicillin is the drug of choice for infected joints where the bacteria Streptococcus dysgalactiae and Erysipelis rhusiopathiae are the most common and account for over 90 per cent of joint fluid culture results. Penicillin administered once daily for at least five consecutive days during the early stages of lameness has a good cure rate in many infections. Dead bacteria and white blood cells within the joint cause inflammatory changes and some degree of lameness often persists.
Lambs with polyarthritis that continue to show moderate to severe lameness after two courses of antibiotic therapy do not grow well and represent a major welfare concern. These lambs must be euthanased for welfare reasons.
Figure 12. Lambs with polyarthritis that continue to show moderate to severe lameness after two courses of antibiotic therapy must be euthanased for welfare reasons.
Treating all lambs with penicillin in the first few days of life to prevent joint infections is not a justifiable use of antibiotics. All efforts to prevent infection should be made instead and veterinary advice sought if joint infections start to occur.
The risk of bacteria entering the bloodstream are reduced by ensuring adequate intake of quality colostrum and by lowering the environmental bacterial challenge. The lamb must ingest 200 mls per kg bodyweight during the first 24 hours of life and 50 mls per kg within the first 2 hours. The navel must be fully immersed in 10% iodine within the first 15 minutes after birth and repeated 2 to 4 hours later. Turnout to pasture for outdoor lambing for the late high risk period can reduce the number of lambs affected.
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