This case report describes a case of watery diarrhoea, weight loss, submandibular oedema and deaths affecting a herd of goats in North West NSW from December 2020 to February 2021. While these clinical signs can also be consistent with internal parasitism, this differential diagnosis was ruled out during an investigation and a diagnosis of yersiniosis was made after Yersinia enterocolitica was cultured from the gastrointestinal system of an affected animal.
Yersiniosis is not a frequent diagnosis in our region, particularly during the summer months.
During December 2020 the owners of a 260-head goat herd observed watery diarrhoea and submandibular oedema affecting all ages and classes of animals. They performed an autopsy on the first animal to die, a doe, and found Haemonchus contortus in the abomasum. They drenched the herd with Avomec®-Duel (Dose administered 1.5ml/5kg; abamectin 1g/L and closantel 50g/L, Boehringer Ingleheim). However, illness persisted, and a number of goats continued to develop watery brown diarrhoea, lose condition, become inappetent, become weak, and die over a period of 10-14 days. The owners performed a second autopsy but failed to find any worms. Despite not finding worms they drenched the herd with Q-drench® (Dose administered 1.5ml/5kg; 40.0 g/L levamisole hydrochloride, 37.5 g/L closantel, 25.0 g/L albendazole, 1.0 g/L abamectin, Jurox), and then again a week later with Startect® (Dose administered 1.5ml/5kg; derquantel 10 mg/mL, abamectin 1 mg/mL, Zoetis). The owners noted that it appeared the diarrhoea abated following the Startect® drench, although sick goats with diarrhoea were still present in the herd. From December to January, they lost five does, two wethers and one billy. These were from varying age groups - does up to five years of age, one-year-old wether kids and the billy was four years old. They then sought veterinary assistance as the goats had received three drenches and changed paddocks over December and January, yet the problem persisted.
While the mob was generally in good condition the affected goats were noticeably poorer, body condition score (BCS) 1/5, and had rough hair coats. There was evidence of diarrhoea in both does and kids, but not all animals with diarrhoea were in poor body condition. Some does and kids had submandibular or facial oedema.
Four goats were examined, three does aged four to five years and eighteen months and a one-year-old wether kid. Clinical signs in the most severely affected animals included watery brown diarrhoea - some with mucous and specks of blood, poor body condition, pale pink mucous membranes, and submandibular oedema in one doe and the kid. Another kid presented with submandibular and facial oedema but did not have diarrhoea at the time of the visit. One doe had intermittent watery diarrhoea and submandibular oedema. Another sick doe presented with signs of respiratory illness.
The owners commented that since they had started supplementing with grain and lucerne hay the goats had picked up condition and the oedema had subsided. However, if they stopped supplementation oedema would return.
An 18-month-old doe was selected for post-mortem. She had a 12-week-old kid and had been ill for seven days with brown watery diarrhoea. She had reportedly lost condition rapidly and was BCS 1/5. Post-mortem findings included subacute bronchopneumonia, but the most significant gross pathology was in the gastrointestinal system. Findings included focal erythema in the mucosa of the jejunum and caecum, as well as erythema and ulceration in the mucosa of the distal colon and rectum. The mesenteric lymph nodes were enlarged and oedematous.
Faecal worm egg count on herd samples ruled out intestinal parasitism and coccidiosis – the strongyle count was low with a mean of seven with low numbers of coccidia in five samples.
Biochemistry results for the doe and wether kid showed they were low in creatinine, hypoproteinaemic, hypoalbinaemic and hypocalcaemic. They were also hypophosphataemic, which can be associated with gastrointestinal disease.
Histological findings in the small and large intestine were typical of yersiniosis.
Small intestine morphological diagnosis: "enteritis, superficial, suppurative, subacute, multifocal, moderate with superficial erosion and bacterial colonies." (Patrick Staples)
Large intestine morphological diagnosis: "Colitis, superficial and suppurative, subacute, multifocal, minimal with bacterial colonies." (Patrick Staples). A few coccidia were present but not considered to be currently significant.
Lung findings were consistent with a bacterial pneumonia; however, lung tissue was not cultured.
A profuse growth of Yersinia enterocolitis was cultured from the ileum, which was sensitive to all antibiotics tested, (ampicillin, neomycin, tetracycline, amoxycillin-clavulanic acid, cephalosporin, and trimethoprim-sulfamethoxazole).
Other differentials considered were Johne’s Disease and the chronic form of enterotoxaemia that presents in goats as intermittent diarrhoea. There were no histological findings consistent with Johne’s Disease found in this case, and enterotoxaemia was excluded with negative epsilon test and no histopathological evidence of focal symmetrical encephalomyelitis (FSE) in the brain.
The owners treated the sick goats with oxytetracycline (1ml/10kg, Engemycin®, MSD Animal Health), resulting in a return of appetite, reduction in diarrhoea and an improvement in body condition. The herd was also supplemented with grain and lucerne hay.
Yersinia spp. may be shed in the faeces of asymptomatic animals in the flock or by rodents and wild birds in the environment (Corrie C et al. 2007). This disease event occurred during a period when this farm, and many others in the area, were experiencing a mouse plague that had started during harvest the previous spring and continued to increase through the summer months. At the time of the investigation, we considered testing mice for Y. enterocolitica, however it would have been difficult to attribute an infection in mice as being the source of the bacteria as both goats and mice were potentially exposed to Y. enterocolitica from the environment.
Outbreaks of yersiniosis are often associated with stressful circumstances (Corrie C et al. 2007). Weaner sheep on poor quality feed and under stress due to weaning, helminth burdens or hot weather may be more likely to succumb to Y. enterocolitica (Slee KJ & Button C 1990).
In this case the goats were initially affected by haemonchosis and possibly other internal parasites. Despite being treated with three different drenches over a period of two months the problem continued. It has been noted that as Yersinia spp. cause diarrhoea there is potential for overuse of anthelmintics and antimicrobials as animals are inappropriately treated (Slee KJ & Button C 1990).
The first deaths were noted after a period of rain followed by a drop in ambient temperature in the early summer period. The owners noticed the goats during this time would seek shelter in the sheds and would not graze. Pastures consisted of native and introduced tropical grasses and, although green, they may not have provided sufficient nutrients for growing kids and lactating does. This nutritional issue may have been another predisposing stress factor. Improvements in condition and clinical signs were noted once supplementary feeding with grain and lucerne hay was commenced.
Yersinia spp. organisms survive and grow in the environment at low temperatures and in cool weather environmental contamination by the bacteria may lead to high oral challenge (Corrie C et al. 2007).
However, studies on the excretion of Yersinia spp. in sheep and goats found Y. enterocolitica occurred throughout the year, whereas Y. pseudotuberculosis occurred in the winter and spring (Slee KJ 1988; Slee K.J & Button C 1990). Greater prevalence of Y. enterocolitica was found in summer and autumn (Slee KJ & Skilbeck NW 1991). In this case we have Y. enterocolitica infection occurring during mid-summer.
Studies of the effect of temperature and water on the survival of Yersinia in the environment found Y. enterocolitica had reduced environmental survival (19 days at 20°C and watered) compared with Y. pseudotuberculosis (40 days at 20°C and watered). This study suggested that Y. enterocolitica may be more reliant on survival in the host and cycling through several hosts to build up environmental contamination that allows transmission to new hosts, and that this hypothesis is consistent with the shedding of Y. enterocolitica seen throughout the year (Thomson et al. 2015).
Studies also found that lambs less than one year of age were more likely to be excreting pathogenic Y. enterocolitica serovars than sheep over one year of age (Slee KJ & Skilbeck NW 1991). Goats less than one year of age are more likely to be infected than those 1-2 years of age and older, and goats 1-2 years of age were more likely to be excreting pathogenic Yersinia than older animals (Lanada et al. 2015). Infection was rare in aged sheep, possibly because past infection induced immunity to further challenge (Slee KJ & Skilbeck NW 1991).
In this case goats of all ages were affected by clinical disease. A case of Yersinia pseudotuberculosis causing enteritis in adult sheep has been reported (Gillan N 2015). There were similar concurrent stressors including wet weather and internal parasites. This investigation was also instigated after a failure to respond to anthelmintics.
Studies on Yersiniosis in goats found that they develop immunity to pathogenic strains of Yersinia spp. (Lanada et al. 2015). As all ages were affected in this case, it seems that the infection may have been introduced into the herd either with introduced goats as they were building their herd, or from other species contaminating the environment.
In January 2022 Y.enterocolitica infection has again been diagnosed in this herd affecting the weaners, 3-5 months of age, and introduced does, 18 months of age. The first cases and deaths occurred in late November 2021, just prior to weaning in December. The young goats were presenting with diarrhoea and weight loss with 12% mortality from December 2021 to mid-January 2022.
Yersiniosis is a differential diagnosis to be considered when investigating gastrointestinal disease in goats in any season. In this outbreak disease was associated with stress factors, including climatic and environmental stressors and internal parasitism.