By Neil MacPherson, Te Awamutu
Salmonella infection in dairy cattle can cause severe illness and disease in dairy herds especially around calving time and in the early lactation period. It’s timely to look at control of salmonella as many herds are dried off and calving is not far away.
What causes Salmonellosis? The disease is caused by Salmonella bacteria. There are many types or serovars that affect cattle but Salmonella typhimurium and Salmonella bovismorbificans are the most common.
What are the clinical signs? Salmonellosis in adult cattle usually presents with a sudden onset of diarrhea. Affected cattle are usually dull, depressed and have an elevated temperature. They will have a sudden drop in milk production and a loss of appetite and usually develop profuse, watery and foul smelling diarrhea. Cattle become quickly dehydrated and lose weight rapidly and without early treatment death rates can be high. Some strains of Salmonella (e.g. brandenburg) can cause abortions in cows and ewes. Calves can also become infected and develop septicemia, diarrhea and joint ill or may even been found dead without any obvious clinical signs.
How do cattle get salmonella? Salmonella is usually spread via the fecal-oral route either by direct contact, or indirect contact via contaminated feed or water, effluent irrigated paddocks, or through vectors such as birds and rodents. The bacteria can survive long periods in the environment with reports of up to 28 weeks in effluent ponds. Milk can also become contaminated with salmonella, either by clinically infected or carrier animals.
What treatments are available? Early treatment with broad-spectrum antibiotics, anti-inflammatories and fluid therapy where appropriate.
How to diagnose? Diagnosis is by a faecal culture of affected animals.
What can you do to prevent Salmonellosis? Vaccination is effective in preventing disease, it is also useful in an outbreak situation to help reduced deaths and abortions. Vaccination should be considered when you have an outbreak of salmonellosis or had significant history of Salmonellosis in the herd. There is a vaccine registered for use in cattle in New Zealand which contains four Salmonella antigens. Cows should be vaccinated twice, 3-4 weeks apart and then a yearly booster. For colostral protection (for calves) the cows should be vaccinated 8 and 3 weeks before calving and then a yearly booster 3 weeks prior to calving. Colostrum from vaccinated cows should be fed to calves for at least 5 days following birth. Vaccination can help prevent or at least reduce the number of losses and clinical cases. Discuss a vaccination programme with your vet.
Other control measures include separating clinically affected animals so to reduce environmental contamination. Effluent should be stored in ponds for approximately a month and spread over pasture, ideally such pastures should be cropped or at least rested for at least 4-5 weeks following application. Rodent and bird control is important especially around grain silos, storage bunkers and in-shed feeding systems. Preventing access of cattle into feeding bins on feed pads so to prevent faecal contamination of feed.
Can people contract salmonellosis? Yes. Salmonellosis can cause serious illness in people. Infection occurs by direct or indirect contact with cows and calves, consumption of raw milk, consumption of contaminated food, drinking contaminated water or contact with untreated water. Clinical signs in people include diarrhea, severe stomach cramps, fever and dehydration lasting 4-7 days. Consult your doctor for medical advice and support.