The causes and circumstances of diarrhea in neonatal lambs and kids are similar to those in newborn calves. Intensive lambing practices and the use of lambing sheds increase the potential for disease and accumulation of infectious agents and can be associated with serious outbreaks of diarrhea. The serotypes of enteropathogenic Escherichia coli that cause secretory diarrhea in calves also do so in lambs, and the approach to diagnosis, treatment, and control is similar.
Similarly, rotavirus, coronavirus, and cryptosporidia also cause outbreaks of diarrhea in lambs. Lamb dysentery caused by is a distinct intestinal disease of lambs in the first week of life. It occurs principally in hill breeds of sheep in the UK and is characterized by sudden death or diarrhea, dysentery, and toxemia. In the US, causes a similar syndrome. Watery mouth or rattle belly, a disease of uncertain etiology associated with overgrowth of nonenteropathogenic E coli in the neonate's digestive tract in combination with failure of transfer of passive immunity, occurs predominantly in the UK.
Coccidiosis of sheep and goats and GI helminthiasis, except for haemonchosis, are important causes of diarrhea in older nursing and weaned sheep. Terminal ileitis and villous atrophy, both of unknown etiology, are often present in the intestines of lambs culled because of poor growth.
GI helminthiasis is the most common cause of diarrhea in pastured sheep. Coccidiosis develops in association with overstocking or intensive indoor housing and poor sanitation.
Salmonellosis can cause diarrhea in sheep and goats of all ages; the circumstances in young lambs are similar to those in calves. It also can cause outbreaks of diarrhea late in pregnancy and is frequently accompanied by abortion. Salmonellosis is more common when sheep or goats are congregated intensively or stressed, particularly by shipping.
Yersinia pseudotuberculosis and Y enterocolitica have both been associated with enterocolitis and diarrhea in young pastured sheep that are debilitated from factors such as starvation and cold weather. Diarrhea can occur in sheep with bluetongue and is accompanied by typical mucosal lesions. In goats, diarrhea is often prominent in enterotoxemia associated with C perfringens type D. This is not a feature of the clinical disease in sheep but can be present in flockmates of affected sheep. In feedlot sheep, diarrhea is most commonly associated with grain overload, salmonellosis, or coccidiosis.
Other intestinal diseases of adult sheep can manifest with diarrhea. Infection with C perfringens type C ("struck") manifests with abdominal pain, tenesmus, and rapid death. Intestinal obstruction occurs sporadically. Sheep with paratuberculosis usually show progressive emaciation without diarrhea. Progressive emaciation is also the primary clinical sign in adult sheep with intestinal adenocarcinoma, which can be prevalent in certain areas associated with ingestion of bracken fern.
Watery Mouth Disease in Lambs
(Slavery Mouth, Slavers, Rattle Belly)
Watery mouth disease is a condition occurring in intensively reared lambs during the first days of life. Morbidity in a flock can be as high as 30%, and the mortality rate can exceed 80% (1). It is one of the main drivers of prophylactic and metaphylactic antimicrobial use in sheep flocks in some regions (1).
Etiology and Pathogenesis of Watery Mouth Disease in Lambs
Watery mouth disease in lambs has been associated with ingestion of gram-negative bacteria, particularly Escherichia coli, that survive in the neonatal GI tract and translocate from the gut to the bloodstream. The strains involved are F5 (K99) antigen negative and regarded normally as nonenteropathogenic and nonenterotoxigenic. The resultant bacteremia might be tolerated by the lamb; however, a bacterial count > 104 CFU/mL is associated withrelease of free endotoxin, resulting in endotoxemia and endotoxic shock (1).
Lambs 12–72 hours old with inadequate or delayed access to colostrum are at greatest risk. Other risk factors that have a negative effect on colostrum intake include being born in larger litters, being born to a dam with poor body condition, and stressors such as early castration.
Clinical Findings of Watery Mouth Disease in Lambs
Lambs affected with watery mouth disease exhibit the following clinical signs:
hypothermia
dull affect
anorexia
typically, long strings of saliva drooling from the mouth
abdominal tympany, which might co-occur with splashing sounds from the belly
In less obvious cases of watery mouth disease, the lamb might have a wet muzzle; or, it might show no external signs of excess salivation, but its mouth might be cold to the touch and contain frothy saliva. Lacrimation can also occur.
The abomasum can become distended with gas and liquid, giving the deceptive appearance of a well-fed lamb; however, if these lambs are lifted and shaken gently, a noise associated with the alternative name of “rattle belly” might be heard.
Although diarrhea (scours) occasionally occurs, this is not a characteristic feature of watery mouth disease. If the diarrhea is left untreated, affected lambs rapidly become hypoglycemic and hypothermic, and they die within 24 hours.
Lesions of Watery Mouth Disease in Lambs
Lesions of watery mouth disease, discoverable on necropsy, can include a bloated and inflamed GI tract, retained meconium, pale kidneys and muscle, dehydration, and enlarged and reactive mesenteric lymph nodes.
Diagnosis of Watery Mouth Disease in Lambs
Clinical signs, supported by necropsy findings
Watery mouth disease is a clinical diagnosis of unconfirmed etiology and pathophysiology. Accordingly, diagnosis is primarily based on clinical presentation and can be supported by postmortem findings. Biochemical and hematologic parameters are often unremarkable in the early stages of disease. Necropsy findings in lambs affected with watery mouth disease are consistent with endotoxemia and a clinical diagnosis of endotoxic shock. Terminally, lambs develop endotoxemia, leukopenia, severe hypoglycemia, and lactic acidemia.
Differential diagnoses for watery mouth disease in lambs include the following:
colibacillosis (neonatal lamb diarrhea)
joint ill (navel ill)
hypothermia
primary starvation
lamb d-lactic acidosis syndrome
Treatment of Watery Mouth Disease in Lambs
Supportive care
There is no specific treatment for watery mouth disease. Hydration must be maintained by offering milk or milk replacer in small amounts at short intervals. Systemic antimicrobial therapy with a gram-negative spectrum (eg, amoxicillin with clavulanic acid) and anti-inflammatory therapy with NSAIDs or corticosteroids to counteract the effects of endotoxemia should also be administered. Therapy should be continued until clinical signs resolve and the lamb is sucking again. Boosting body temperature by external warming might also be required.
Prevention of Watery Mouth Disease in Lambs
To prevent watery mouth disease in lambs, ewes should be well nourished to ensure a plentiful supply of colostrum. Yards, pens, ewes, and equipment should be kept as clean as possible throughout lambing to help control the buildup of E coli and keep disease incidence low. Supplementary feeding of lambs using stored colostrum (ewe, cow, or goat) or a commercial colostrum substitute should provide a minimum of 50 mL/kg within 6 hours after birth (2). Lambs should not be castrated in the first 24 hours of life because this depresses colostrum intake.
Pearls & Pitfalls
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In controlled experiments, a single dose of oral antimicrobial given within 2 hours after birth to colostrum-deprived lambs delivered into a contaminated indoor environment was as effective as ewe colostrum in preventing neonatal watery mouth disease and death in all lambs up to 3 days old, despite the absence of maternal antibodies (3). Thus, metaphylactic antimicrobial treatment of lambs at high risk might be an effective means of rapidly decreasing disease incidence in affected flocks. However, such treatment must be targeted to lambs in the high-risk categories (see Etiology and Pathogenesis), because indiscriminate dosing will encourage antimicrobial resistance.
For More Information
Eales FA, Small J, Gilmour JS, Donachie W, FitzSimons J, Dingwall WS. A field study of watery mouth: clinical, epidemiological, biochemical, haematological and bacteriological observations. Vet Rec. 1986;119(22):543-547.
References
Angell J, Duncan J. Watery mouth disease in neonatal lambs: a systematic literature review. Livestock. 2020;25(2):94-103. doi:10.12968/live.2020.25.2.94
Hodgson JC, Moon GM, Hay LA, Quirie M. Effectiveness of substitute colostrum in preventing disease in newborn lambs. BSAP Occasional Publication. 1992;15:163-165. doi:10.1017/S0263967X00004183
Hodgson JC, Brebner J, Mckendrick IJ. Efficacy of a single dose of oral antibiotic given within two hours of birth in preventing watery mouth disease and illthrift in colostrum-deficient lambs. Vet Rec. 1999;145(3):67-71. doi:10.1136/vr.145.3.67
