When you think about summer, do the words “heat” and “humidity” instantly come to mind? How about the words “salmonella” and “outbreak”? The truth is the heat and humidity of summer can create the ideal environment on a dairy for a salmonella outbreak.

Now is the time to help protect your dairy from salmonella by evaluating your risks and ensuring you aren’t leaving any doors open for the disease to enter your dairy.

Understanding the disease
Salmonella is an intestinal bacterium that can cause significant disease in dairy cattle of all ages. The bacteria typically are spread from the waste of one animal and then ingested by another. A carrier of the disease can appear healthy while shedding the bacteria to others.

If salmonella enters your herd, it can be hard to recognize. There are two common types of salmonella infections: clinical and subclinical.

While clinical salmonella can be damaging, with symptoms such as fever, diarrhea and death, subclinical salmonella could be more devastating and costly. Subclinical salmonella is even harder to spot than clinical disease.

Think of subclinical salmonella as the base of an iceberg that is hidden from view. Your cows already may be suffering from an infection with lower milk production, poor feed efficiency, weight loss and abortions. These signs aren’t as noticeable as those for clinical disease, making it more difficult to notice a problem.

Not only is the disease tough to recognize, the bacteria are also hard to keep off your operation. Salmonella can survive in the environment, making it easily transferable by cattle, rodents, birds, pets or objects.

And with prevalence of salmonella on the rise, the disease can spread easily. Having a tight biosecurity plan can help keep salmonella off your dairy.

Closing the door to salmonella
Even if you do practice some biosecurity measures, you still may be leaving the door open for the bacteria to enter.

A recently released National Animal Health Monitoring System (NAHMS) survey of heifer-raising operations sheds some light on areas where all dairymen can improve their biosecurity plans to help ward off salmonella and other diseases.

Potential open door: New cattle entering the dairy
Whenever cattle from another source enter the dairy, whether purchased from another dairy or returning to the milking operation from a heifer grower, there is the possibility that other diseases are tagging along.

Of the heifer raisers surveyed by NAHMS, 60 percent of operations commingled heifers from more than one dairy, and another 21 percent allowed heifers to have nose-to-nose contact with heifers from other dairies despite being housed separately. Both situations allow for the possibility of disease transmission.

Not only could the bacteria be living in the cattle but also on the trailer or truck transporting the cattle to your dairy. Fewer than one-third of those surveyed noted cleaning out and washing transportation vehicles after every shipment of calves.

How to close the door
Procedures for cattle entering your herd should be an important part of your biosecurity plan. Whether buying new cattle or bringing your heifers back, work with your veterinarian to establish testing and quarantine protocols before commingling the cattle with the rest of your herd.

And try to get the health history of any new cattle being purchased for your records.

Clean trailers transporting cattle – remove manure and disinfect surfaces – after every shipment of cattle. Work with the company and people transporting your cattle to discuss their biosecurity measures.

Potential open door: Rodents, wildlife, pets and other livestock on the dairy
Rodents and wildlife can drop by unexpectedly and may carry bacteria, such as salmonella, that can be transmitted to dairy cattle.

More than half of dairy heifer raisers had visits from deer, coyotes, foxes and raccoons at least once every month. Other pests such as birds and mice potentially can be carriers.

Many operations have pets, such as cats or dogs, while others also may be home to other livestock. A NAHMS study found 83 percent of heifer-raising operations also were home to a cat, while 63 percent also were home to a dog.

Additionally, up to 30 percent of heifer raisers also housed beef cattle; horses, donkeys or mules; or chickens or other poultry, which also could carry diseases that can be passed to dairy cattle.

How to close the door
While it may be impossible to keep wildlife and pets off your property, it is important to take steps to keep other animals away from your cattle to reduce the risk of disease transmission.

Additional fencing may be needed to keep wildlife out and to keep other livestock from contacting dairy cattle. Wildlife and rodents often are looking for food. Keep your feed storage clean and protected to keep animals out of those areas.

Potential open door: Employees, consultants and visitors on the dairy
People also can bring salmonella and other diseases to a dairy. Every day, lots of people – employees, veterinarians, nutritionists, visitors, etc. – can travel on and off your operation, as well as to and from cattle pens.

Nearly all heifer-raising operations with 20 to 999 head had one to five employees who cared for heifers. When surveying operations of more than 1,000 head, nearly 50 percent had six to 20 employees caring for heifers.

These numbers don’t include consultants such as veterinarians, artificial insemination (A.I.) technicians and nutritionists who visit dairies routinely and have close contact with cattle. Visitors were allowed in heifer housing areas on 40 percent of raising facilities.

How to close the door
For anyone going in or near cattle pens, properly managed footbaths can disinfect footwear that carry bacteria between groups of cattle. Veterinarians and A.I. technicians also should wear clean coveralls and boots before entering cattle pens.

Visitors should not be allowed to enter or go near the feeding areas or pens. If they need to, make sure they adhere to biosecurity measures, using footbaths and wearing protective clothing.

Develop a prevention plan
With many access points to the dairy, implementing a salmonella prevention plan is important for your dairy to help close doors to the disease.

Your veterinarian can help you review the areas where salmonella could enter your dairy as well as other management practices that can limit your risk of salmonella.

A good first step is to take a risk assessment; you can visit SalmonellaRisk.com/Assessment for one. The short questionnaire will help determine your risk.

After taking the assessment, work with your veterinarian to develop a salmonella prevention and biosecurity plan for your dairy. Vaccination is a key component of any salmonella control program. Vaccines can help prevent a clinical outbreak of salmonella Newport as well as limit economic damage due to subclinical disease.

A thorough prevention plan should cover biosecurity measures for traffic traveling on and off the dairy, as well as practices on the dairy where diseases could spread, such as colostrum management, feed storage and equipment use. Take proper steps to help reduce your risk of a devastating salmonella outbreak. PD

References omitted due to space but are available upon request. Click here to email an editor.

Neubauer has a DVM degree from the University of Minnesota and is employed by Zoetis as a senior manager for dairy technical services managing the Central and Eastern U.S.

Gary Neubauer
Senior Manager of Veterinary Operations
Zoetis