Cases of yersiniosis in cattle are seen each winter on the north coast. Ten cases were investigated by the author in the winter of 2012 over a 10 week period. A total of 19 cattle died on these 10 properties. A further 14 cases were reported by other veterinarians in the district. This case study describes a geographical and temporal cluster of three cases.
The three investigations occurred within a 15-day period between 23rd July 6th August 2012. Coincidentally the investigations were on sequential Monday mornings. The properties are located within 3km of each other in an area known as Greenridge, located about 10km south east of Casino on the mid Richmond floodplain.
Mortalities in the herds were; 1/19 in herd A, 2/42 in herd B and 2/52 in herd C.
On 23rd July 2012 Herd A had a Simmental bull found dead after 2 day history of lethargy, inappetence, acute weight loss and diarrhoea.
In herd B a 6 year old Murray Grey cow was found dead. Two weeks later on 30th July a 4-5 year old Murray Grey cow was recumbent and unable to rise with a 2 day history of weight loss and profuse diarrhoea. On examination, the cow was moribund, with labored breathing, was dehydrated, had slow mucous membrane refill and a rectal temperature of 35.5. The cow was euthanased and autopsied.
On 4th August in herd C a mature Angus X Hereford cow was found dead with signs of recumbency and diarrhoea. Two days later on 6th August a Brangus cow was found down. On examination the cow was under a fence, unable to rise, had evidence of diarrhoea, was groaning, teeth grinding and was unresponsive. It had a temperature of 38.8. Again the cow was euthanased and autopsied.
Autopsy findings in all 3 animals were very similar. There was typhlitis, colitis and ileitis. Changes to the mucosa included thickening, rugae which were difficult to reduce, inflammation, swollen ileocaecal valve and a thick white catarrhal exudate. There were casts present in the colon. The proximal ileum and duodenum were normal. There was minimal change in the intestinal lymph nodes.
Petechial haemorrhages were found throughout the carcase, including the omentum, mesentery, pleural surfaces and epicardium.
Yersinia pseudotuberculosis was isolated from the ileum and from intestinal content in the autopsy in herd B. Because the gross pathology is characteristic isolation is not attempted in all cases. Laboratory confirmation was undertaken on 4 of the 10 properties investigated.
Yersiniosis due to Yersinia pseudotuberculosis.
When yersiniosis is confirmed on a property, owners are advised to check the cattle at least twice a day for signs of lethargy, inappetence or diarrhoea. Any sick cattle should be treated with the long acting dose rate of oxytetracycline. As with most conditions a paddock shift to a drier paddock, if possible, is recommended.
In some outbreaks where cases continue there is a place for prophylactic administration of antibiotics in situations where a paddock shift is not possible. (Freeman pers com).
In this cluster, each of the herds had further suspect clinical cases after diagnosis that were treated.
Herd A had 1 further case 4 - 5 days later; an aged Angus X cow that became recumbent and had diarrhoea. Herd B had a 5 year old Murray Grey cow develop diarrhoea 2 days later. Herd C had 2 further cases; a mature Brangus cow the day after the property visit that became lethargic, then recumbent profuse diarrhoea the following day. Another Brangus cow 12 days later developed diarrhoea. All were treated with Oxytetracycline and responded. Convalescence varied from 24 hours to 10 days.
Yersiniosis is seen in the cooler, winter months on the north coast. It is more prevalent in wet years. In most years cases cease with the arrival of warm, westerly weather patterns. However the spring of 2010 was mild and wet and an outbreak was seen in early November.
Cattle of all breed are affected; this season deaths were seen dairy, Euro, British, Brahman and F1 Brahman. However Brahmans and their crosses do appear to be more susceptible. It is not unusual to have owners report that the F1 or Brahmans are affected, but not their British breed cohorts.
The north coast experience is that yersiniosis is a disease of mature age cattle. This was documented by Boyd Unger, DV Casino in 1985 (Hungerford 1990). The age distribution on the north coast differs from yersiniosis described as a disease of individual calves or yearlings by Parkinson et al (2010).
Some cases involve only an individual animal, but the majority occur as an outbreak. For example during July 2012, 4/80 Jersey milkers in dairy near Casino died within a few days with confirmed yersiniosis. For this reason owners are warned to closely monitor the cattle and treat early.
The duration of the disease is variable. The clinical course is usually 24 - 48 hours, with death following diarrhoea, sudden weight loss and dehydration. Some cattle may die before the onset of diarrhoea. Others may have dramatic weight loss and diarrhoea for a week. In the early stages of the disease the cattle are febrile however as the disease progresses hypothermia is seen prior to death.
Typically the disease is seen on low lying country, paddocks that have a swamp or have recently been flooded. It is associated with dry feed exposed to mud; and hence has the local name of Flood Mud Scours. However cases are also seen on high country. These are associated with wetter areas within a paddock such as drains, bogs or night camps (Freeman pers com). One memorable outbreak was seen by the author on a high hill with million dollar views over Byron Bay. Cases can be associated with hay packed into the mud around round bale feeders. For this reason routine recommendations are to remove or burn wasted hay and to feed small bales that can be consumed in the day.
The experience of the author is that the gross pathology of yersiniosis is reasonably consistent between individuals; with the caecum, large intestine and distal 1/3 of the small intestine affected. However some individuals have changes throughout the small intestine. Oedema of the abomasal mucosa has been seen, but it is not known whether this was due to concurrent Ostertagia infection.
The common differential diagnosis for acute onset diarrhoea in adult cattle during the winter months on the north coast is salmonellosis and Type II Ostertagiasis. For this reason producers are encouraged to seek veterinary advice.
Paul Freeman, Regional Veterinary Officer, NSW Department of Primary Industries, Wollongbar
Ian Poe Senior District Veterinarian, Mid Coast
Phil Sharman, Casino Veterinary Clinic
Joe McElearn, Fairymount Veterinary Clinic, Kyogle
Matt Ball, Senior District Veterinarian, North Coast