Outbreaks of Salmonellosis in Canterbury stock

Press, 22 February 1980, Page 15

Outbreaks of Salmonellosis in Canterbury stock

; Some diseases tend to .'-have a seasonal incidence. Salmonellosis is one of these, occurring mainly in -the summer in sheep. It is currently causing losses in some Canterbury sheep flocks. ’ The disease is caused by a bacterium Salmonella, which usually causes scouring and death, and is usually associated with heavy stocking rates. Outbreaks can be controlled provided a rapid and accurate diagnosis is made by a veterinarian. The usual method of control .is to spread the affected flock over a wide area. We have diagnosed outbreaks of salmonellosis in Canterbury sheep, mainly ewe flocks, since December in two or three flocks each fortnight. Reported losses have been low, rarely over one per cent of the affected flock. This Jias probably been because of prompt veterinary action. Z‘ Salmonella bacteria may be present in healthy carrier animals. These animals continuously shed

small numbers of bacteria into the environment. A few of these are always ingested by other animals. However, these Salmonella bacteria are prevented from causing disease by the great variety and numbers of bacteria normally present in the gut of healthy animals. Stress in animals can be caused by many things and has many effects. In the summer ewe mobs are frequently closely stocked. This makes them more susceptible to Salmonella by reducing the number of normal gut bacteria. Operations such as yarding, shearing, dipping, and trucking, and starvation and water deprivation have a similar effect, resulting in outbreaks of salmonellosis over the following week. Once in a susceptible animal Salmonella bacteria damage the gut wall, interfering with the digestion. and absorption of food and fluids, and causing a thin watery scour, frequently light green in colour and with an offen-

sive odour. The bacteria may then invade the whole body through the blood, setting up foci of infection in other organs. Death usually follows rapidly in such cases. Affected sheep are usually found terminally ill or dead. Intensive antibiotic therapy, under veterinary supervision, is necessary for successful treatment of affected animals. Rapid veterinary investigation of disease outbreaks may lead to a diagnosis suggestive of salmonellosis. " Laboratory examination of faeces or specimens from dead animals is necessary to confirm the diagnosis. Once a presumptive di-

agnosis has been made, spread to other sheep can be prevented by decreasing the stocking rate, e.g. smaller mobs and larger paddocks. Salmonella bacteria can infect many animals and also man, where, it is sometimes responsible for outbreaks of food poisoning. This should be remembered when handling live or dead infected animals and strict attention should be paid to personal hygiene. ’ Foals and cattle have also been affected with salmonellosis in the past two months. Affected animals have scoured for several days to weeks before death in spite of antibiotic theraphy. Salmonellosis is usually an uncommon disease in

.Canterbury. Accurate and rapid diagnosis and prompt management! changes, all done under veterinary' supervision, will minimise losses from the disease.

The yriter of the accompanying item on outbreaks of salmonellosis in Canterbury stock this season is R. C. Gumbrell, veterinary investigation officer, Animal Health Laboratory, Ministry .of Agriculture and Fisheries, Lincoln.