key: cord-0041737-7jwkchjd
authors: Bazeley, Katrine
title: An outbreak of Salmonellosis in a Somerset dairy herd
date: 2010-09-30
journal: nan
DOI: 10.1111/j.2044-3870.2006.tb00046.x
sha: 119fc95e4a6c3bb9b38698a73e261533e846ad98
doc_id: 41737
cord_uid: 7jwkchjd

nan

In this herd, diagnosis of Salmonella Dublin was confirmed by culture of vaginal swabs from aborted cows. The clinical signs, pyrexia, milk drop and scouring, were also strongly suggestive of salmonellosis.

Affected calves were all more than 4 weeks old so infection with E. coli, Rotavirus or Coronavirus was unlikely. Other common causes of scour for calves of this age are coccidiosis and cryptosporidiosis, though neither is generally associated with such severe clinical signs, rapid deterioration or high mortality as in this herd (Bazeley 2003) . The incidence of Salmonellosis as a cause of disease in calves is probably higher than recognised, and in a UK survey of diarrhoeic calves, salmonellae were isolated in 12% of sick calves and in 24% of outbreaks (Jones, Watson and Wallis, 2004) .

A number of salmonella serotypes cause disease in cattle, although in the UK, S. Dublin and S.

This is a family farm run by father and son, with a dairy herd of about 100 cows, average yield 7,000L. Heifer dairy calves are reared as replacements and some beef calves are reared to be sold at weaning. Calves are reared in single pens to one week old then moved into groups of 5 in a barn next to the milking parlour.

During 2005 two bulls were bought from different farms, and 6 heifers were bought from a neighbour as they calved in. No calves were purchased.

Seven cows and one heifer aborted in a period of nine weeks. Generally they were profoundly sick, with severe milk drop (in some cases for 2-3 days before abortion), diarrhoea and pyrexia.The heifer died one week after abortion. Two freshly calved heifers also became clinically ill. Calves began to scour about 4 weeks after the first abortion and 7 of the 15 affected calves died within 1-2 days despite antibiotics, electrolytes and nursing. The calves that survived remained extremely poor and failed to thrive.

A low level (figures vary, but a target of less than 2% can be used) of foetal loss can be considered 'normal' or unavoidable, but higher losses are caused by a range of infectious and non-infectious agents. The common infectious causes of abortion and associated clinical signs are listed in Table 1 typhimurium are by far the most common. Most transmission of disease occurs directly from animal to animal, although it may also be transmitted via contaminated feed, pasture spread with contaminated animal waste or human sewage sludge, or contaminated water. S. Dublin is a cattle-specific organism, and is therefore less likely to be spread by birds or rodents, as other serotypes may, although there is fairly good evidence for local bird spread in SW Scotland. Infected cattle shed vast numbers of organisms in the faeces. Adult cattle often become carriers of S. Dublin, excreting the organism mainly at times of stress, for example after sale or around calving. S. Dublin is often harboured in the gall bladder and the disease is sometimes associated with liver fluke infestation.

In this herd there was a history of introduction of a purchased heifer that had 'calved early'; it is possible that this animal brought the disease with her. It is also possible that this outbreak was simply the reemergence of disease carried within the herd for a prolonged period. 

Once the adult cows were infected it was easy for disease to spread to the young calves either via contaminated milk, or spread on boots and clothing.

Ideally, the following control measures should be adopted: 1. Immediate investigation of the cause of abortion, and early investigation of the cause of diarrhoea. 2. Isolation of aborting cows and disposal and disinfection of all aborted material and bedding contaminated by affected cows 3. Institution of strict hygiene measures to control spread of disease. These should include use of separate overalls and disposable gloves for handling infected cattle and the use of a boot dip made up to specified concentration and changed daily. 4. Careful personal hygiene. Although S. Dublin rarely infects humans, it can cause serious disease. 5. Treatment for liver fluke In this herd, cows were not kept fully isolated following abortion and a boot dip and other hygiene measures were not put in place immediately and may have allowed spread of disease from cows to calves. There were no further cases in calves once the infected animals were moved out and the house was thoroughly cleaned and disinfected using FAM 30 (an iodine-based chemical).

Ideal: 1. Stop buying in cattle 2. Alternatively, if cattle must be bought-in, quarantine for one month. Bacteriological investigation may or may not identify carrier animals during this period 3. Keep feed in vermin-proof containers 4. Make sure that water sources are free from contamination 5. Control liver fluke and other debilitating disease 6. Calve cows in single pens and clean and disinfect between occupants 7. Ensure that all calves receive at least 2 litres of colostrum within 6 hours of birth, and continue to be fed colostrum for a minimum of 24 hours. 8. All-in, all-out policy for calf-rearing accommodation 9. Try to identify carrier cows by sampling three times on consecutive days at calving time 10. Vaccinate the herd.

In this herd, in-calf heifers have been vaccinated and will continue to be vaccinated, on the basis that the heaviest losses are those due to abortion. Hygiene levels are good, and the situation will be reviewed. There has been no disease for three months. This improvement may not be the result of vaccination.

Losses continued for approximately two months after the first cow aborted.

According to these calculations (Tables 2 and 3 

Cattle Practice Calf Pneumonia Costs

Practice Investigation of diarrhoea in the neonatal calf

Cattle Practice 10:4 Cattle Abortion: what samples when?

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