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This article was published in 1984
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Bovine Enterocolitis (associated with Yersinia pseudotuberculosis)
D.B. UNGER, B.V.Sc., Veterinary Inspector, CASINO
Disease in cattle associated with Yersinia (Pasteurella) pseudotuberculosis is a recognised clinical entity overseas but has been rarely if ever reported in Australia and never in an outbreak form.
Overseas cattle references are to isolated, acute fatal infections, and incrimination in bovine mastitis and abortion. (Obwolo 1976).
This report refers to an outbreak during winter and early spring of 1983 in the northern rivers region of coastal New South Wales of an acute to peracute enterocolitis associated with Y. pseudotuberculosis. It should be noted that a similar condition has been seen for many years, particularly during cool, wet conditions, and is known variously as flood mud scours and swamp scours.
The first case noted was on a small Angus stud on the lower mid Richmond on 30th June.
This animal was a 6 year old lactating Angus which was noticed to have a foul watery scour and died within 12 hours.
Further cases of death followed scouring with an observed course of 12 to 48 hours. A few surviving animals scoured for 4 to 10 days.
The problem persisted on this property for 23 days. The eventual morbidity rate in the herd of 88 was 9% and the mortality rate was 62.5%.
The majority of herds with this syndrome were recognised in July with the last confirmed case being early September. Cases were seen first on the Richmond then later in the Clarence Valley and possibly Kempsey.
The worst outbreak involved a herd of 340 head with 20 dead and 80 others sick, giving a morbidity rate of 29% and mortality rate of 20% [Editor calculates this at 6%].
AGE
The majority of animals were mature adults with the youngest confirmed case 15 months. (Range 15 months to 15 years).
The crude death rate over the observed herds has been determined as 7.5% with case mortality rate as 46%.
CLINICAL SIGNS
Affected animals presented either as sudden death or with depression and inappetence followed by profuse diarrhoea. The scour was very thin, watery and of a grey-brown or olive-green colour sometimes tinged with blood.
In many cases death followed within a few hours of observed sickness.
Generally treatment was successful only if given very early in the course of the disease. In some animals the condition was less acute and lasted for several days.
Temperatures of scouring animals were raised approximately 1°C above unaffected herd members.
PATHOLOGY
In most cases there were moderate to severe subepicardial haemorrhages. Occasionally similar haemorrhaging was observed in the spleen.
The most striking and consistent findings involved the gastrointestinal tract.
Severe oedema of the abomasum, particularly the folds, was a common finding along with inflammation and in some cases erosion and diffuse haemorrhage.
The duodenum was grossly normal in some or had fine petechiation to severe haemorrhagic, necrotic lesions in others.
More consistently from the jejunum and distally there were severe congestion, diffuse haemorrhage, fibrinous and necrotic enteritis.
Intestinal contents were abundant and watery, varying in colour from olive green to pink-brown to bloody. In some cases there were numerous cream coloured mucopurulent or fibrinous floccules up to 8mm in diameter
Numerous pinpoint necrotic foci may be seen in the caecum and colon.
CLINICAL PATHOLOGY
Leucocytosis, haemoconcentration and hypoproteinaemia were noted in several cases which were submitted to haematology.
HISTOPATHOLOGY
The following changes were recorded:
Abomasum moderate to marked diffuse submucosal oedema.
Small intestine mild to severe acute enteritis associated with small to large numbers of bacillary bacteria. There was diffuse necrosis and infiltration of the mucosa and submucosa with neutrophils, histiocytes and lymphoid cells.
Large Intestine superficial necrosis with multifocal bacterial colonisation and infiltration with polymorphs and mononuclear leucocytes.
Spleen may be foci of acute bacterial splenitis and diffuse depletion of lymphoid follicles.
Mesenteric 1. nodes may see medullary histiocytosis.
DIAGNOSIS
The following conditions were considered early in the outbreak.
Acute Mucosal disease, Arsenic poisoning, Salmonellosis and internal parasitism including acute paramphistomiasis.
The finding of mucosal disease virus and antigen in an early case confused the issue for a time, but numerous later cases were negative.
Toxicological tests for arsenic were negative. Salmonella was never isolated in any cases.
Internal parasites were found to be in moderate to heavy numbers in some individuals but their presence did not really explain the entire signs.
Acute paramphistomiasis can be responsible for acute scouring and sudden deaths. However the animals in question were expected to be resistant in view of their age and history and the presence of mature stomach fluke in most cases. No immature paramphistomes were seen nor the lesions typical of that disease.
Response to early antibiotic and electrolyte treatment pointed to a bacterial aetiology.
EPIDEMIOLOGY
The Gram-negative, pleomorphic, bipolar staining Y. pseudotuberculosis was consistently isolated once problems of identification were resolved.
This organism is a common cause of epizootics in aviaries and small animal colonies both in Australia and overseas. (Obwolo 1976; Schultz 1981; Butler 1978).
Birds and rats and mice are principal reservoirs of infection (Obwolo 1976, Butler 1978) in these outbreaks.
The source of infection in this bovine outbreak is unknown but ingestion of contaminated feed is a well documented cause of infection in other situations.
It is of interest to note reports of similar outbreaks in recent years in sheep in Victoria (Jones 1983) and deer and sheep in New Zealand (Wilson 1979, Henderson 1983).
The cases in deer in New Zealand are strongly correlated with periods of stress, predominantly in winter when cool, wet conditions and lack of grazing combined.
Similar stress patterns apply in outbreaks in small animals and aviary situations.
This parallels the local outbreak of bovine enterocolitis with all cases seen in winter or very early spring with the weather being unusually wet and many cases occurring on wet, swampy or even recently flooded paddocks. (Hence the name flood-mud scours),
It is important to note also that Yersiniosis is an uncommon but potentially fatal zoonotic (Stevenson and Hughes 1980) (Eamens 1981).
TREATMENT
Very early treatment with oxytetracycline and electrolyte fluids was successful.
Any delay was usually fatal, although a small percentage of animals had a more chronic sickness of several days duration.
REFERENCES
Butler (1978) Sydney University Proceedings No. 36 Fauna - Part B
Eamens, G.J. (1981) Sydney University Proceedings No. 55 Aviary & Caged Birds
Henderson (1983) N.Z. Vet. Journal 31:221-224. Yersiniosis in deer from the Otago-Southland region of New Zealand.
Jones (1983) Control and Therapy 1649 Yersiniosis in Sheep
Obwolo, M.J. (1976) A review of Yersiniosis Vet. Bull. 46:167-171
Schultz, D.J. (1981) Sydney University Proceedings No. 55 Aviary & Caged Birds
Stevenson and Hughes (1980) in Synopsis of Zoonoses in Australia Commonwealth Department of Health Publication Refresher Course.