Salmonella describes several different kinds of bacteria. These bacteria typically infect the gut of a host animal. Physical illness may or may not result from the infection. When physical illness does occur from Salmonella infection it is referred to as Salmonellosis. With high levels of Salmonella exposure and low levels of cattle resistance, any one of the many kinds of Salmonella can cause Salmonellosis. There are, however, some strains of Salmonella that are more likely to cause illness. Salmonella typhimurium is one such strain. Salmonella typhimurium is the most common type of Salmonella found in Michigan dairy cattle, cows and calves. It is also the most likely type of Salmonella to result in physically ill cattle.

Salmonellosis has numerous possible symptoms. Symptoms include diarrhea, bloody stool, fever, dehydration, anorexia/emaciation, rapid breathing, unusual or foul odor stool, sloughing of skin from extremities, and sudden death. Treatment of Salmonellosis can be costly, impractical, and in some instances ineffective. An on-farm outbreak of Salmonellosis is costly because of veterinary expenses, reduced animal performance, involuntary culling, death loss, and lost reputation as a healthy herd.

Cattle with Salmonellosis are not the only Salmonella infected cattle of concern. Some animals may harbor Salmonella in their gut and show no symptoms. These "carriers" can be shedding Salmonella into the environment in their manure for extended periods of time without giving any indication of an infection. Carriers may not become ill because of low levels of exposure and high tolerance; however, they can still transmit the disease to other animals. Salmonella can remain prevalent and undetected in a dairy herd until a stress lowers animal tolerance. A stress of any kind can potentially compromise the immune system and permit Salmonellosis to occur.

Salmonella most commonly causes illness in calves; however, it can effect cattle of all ages. It is usually passed from animal to animal by fecal-oral contact. On-farm contamination of feed is the most common source of Salmonella infection. Given a cool, damp, and dark environment, Salmonella can survive outside of a host animal for days, weeks, and even months. Manure and other organic materials can support the bacteria while it is waiting to be ingested by an unsuspecting new host.

Salmonella is more prevalent in dairy cattle than one might realize. A 1991-92 study conducted by the U.S.D.A. National Animal Health Monitoring System (NAHMS) found that 20.5 of every 1,000 or 2 percent of dairy calves in the Midwest tested positive for Salmonella. A NAHMS study conducted in 1996 revealed that during the warmer, moister months of the year 11 percent of all cows on dairy farms in the United States were shedding Salmonella. The number of positive cows was less than 2 percent during winter months. The 11 percent of dairy cows shedding during warmer, moister months represented 38.2 percent of U.S. dairy farms. Cattle shedding during the winter months represented 21.1 percent of dairy farms.

The 1996 NAHMS study showed a fairly strong correlation between Salmonella shedding and herd size. In reality, the correlation may be to the number of purchased cattle rather than herd size. Michigan is currently undergoing a tremendous number of herd expansions, meaning a tremendous number of cattle purchases. At the same time, very few Michigan dairy farms are following recommended biosecurity guidelines when purchasing cattle. Without adequate preventive steps, acquiring more cattle equals acquiring enormous risk of infectious disease. Thus, it is likely that the incidence of Salmonella outbreaks on Michigan dairy farms is on the increase. Salmonella incidence will continue to grow until all Michigan dairy farmers, not just those who are expanding, tighten on-farm biosecurity.

Biosecurity! Biosecurity! Biosecurity! This word has been beaten to death over the past year, but it has been abused with good reason. A few simple practices in biosecurity can save you from an on-farm health disaster. The old cliché still holds true, "An ounce of prevention is worth a pound of cure."

Total biosecurity involves many areas of management from vaccination programs to farm visitor management. Unfortunately, an effective vaccine against Salmonella in adult cows is not likely in the near future, so preventing animal exposure is the key. Preventing exposure implies that you must know how Salmonella might get onto your farm.

There are two basic ways Salmonella can get onto your farm, animal transmission and inanimate transmission:

· Incoming cattle – Whether you are purchasing cattle or just temporarily housing cattle for someone else, you must be certain that they are Salmonella-free. A veterinarian can have the animals tested; however, repetitive tests of every animal over an extended period of time are required. Repetitive fecal sampling is the best way of ensuring Salmonella-free animals, but this can be a slow and bothersome process. Fortunately, there is another way, know the health history of the source herd(s). This alternative is not foolproof, but it does greatly reduce the risk of introducing many diseases, not just Salmonella.

Oftentimes, the biggest hurdle in knowing the health history of an incoming animal’s source herd is identifying the source herd. Knowing where an animal comes from is simple, if you are buying directly from the dairy producer who bred the animal.

Knowing where an animal has been becomes much more difficult, if not impossible, when purchasing animals through sale barns or cattle brokers. Buying from a sale barn or broker usually means that the animals have been exposed to a "community" handling facility, barn, and trailer. These facilities and equipment have been used and manured on by hundreds, if not thousands, of animals from who knows where. With the contaminated facilities and trailer, it is almost impossible to completely realize to what pathogens, including Salmonella, the animals have been exposed

Once you know the source herd(s), get permission from the owner(s) to talk with the respective farm’s veterinarian. Assuming that the veterinarian has a valid working relationship with the source herd, he or she should be able answer your questions about the current and past health status of that herd.

· Other resident animals – Salmonella not only resides in the fecal material of cattle but of many animals. Birds, rodents, and cats are of primary concern on dairy farms. Contamination of feed with fecal material from any one of these other animals could potentially introduce Salmonella into your herd.

Since Salmonella can survive outside of a host animal in organic material for quite some time, one can easily envision how Salmonella might move from farm to farm without animal movement. Any inanimate object with a little organic material on it can transport the Salmonella bacterium.

Think about it! What might be able to pick-up Salmonella at one farm and transport it to another farm? Who might inadvertently bring Salmonella onto your farm?

Since you cannot keep all of these people off of your farm, what can you do about it? You may not be able to keep the people away, but you can prevent them from bringing unwanted guests, like Salmonella, with them.

Since new infections are most commonly a result of contaminated feed, additional measures should be taken to reduce the likelihood of feed contamination. As you review the following list of other preventive measures, consider the practices on your farm and how you might further reduce the risk of Salmonella infections in your herd.

1.) Do NOT use same loader bucket for both manure and feed handling. Preferably have separate equipment for these two tasks. If this is not practical, at minimum clean and disinfect the equipment between uses.

2.) Do NOT track manure onto feeding surfaces with tires while discharging feed from mixer or pushing-up feed.

3.) Control wild birds in order to prevent droppings from landing on feed while it is in storage or in manger.

4.) Regularly clean and sanitize calf milk buckets/bottles.

5.) Keep all feeding surfaces and water troughs clean.

6.) Do NOT spread or irrigate manure directly onto forages intended for grazing or feeding as green-chop

Discuss with your veterinarian other possible preventive measures for your farm.

Salmonella is zoonotic. In other words, the same Salmonella bacterium that infects dairy cattle can also infect people. Young and older people are the most susceptible to becoming seriously ill; however, anyone can suffer from Salmonellosis.

Salmonella is a serious but manageable health concern on Michigan dairy farms. It is not just your neighbors’ problem because they might have a few sick animals or Salmonella shedding cows. This is a dairy industry-wide concern. Over one in three farms have Salmonella shedding cows during the summer months, and this may be increasing with so many expanding herds. The dairy industry can take action now through biosecurity and suppress the potentially prevalent Salmonella organism. Or the dairy industry can do nothing and permit what is currently a manageable animal health concern to become a public health concern and media frenzy.

Take charge of your farm and industry’s future, implement basic biosecurity practices on your dairy farm.

"Bovine Salmonellosis, Salmonella in Cattle", Consultant; A Diagnostic Support System For Veterinary Medicine. (http//:www.vet.cornell.

edu/consultant/consult.asp) Cornell University Veterinary Medicine. August 1998.

Dargatz, David A. et.al.. "The Veterinarian’s Role in Diagnosis, Treatment, and Prevention of Multidrug Resistant Salmonella typhimurium DT104" USDA-APHIS-VS. 1998.

"Salmonella in Dairy Calves". USDA-APHIS-VS National Animal Health Monitoring System. 1994.

Wells, Scott, et.al.. "E. coli O157 and Salmonella – Status on U.S. Dairy Operations", NAHMS Dairy ’96. USDA-APHIS-VS National Animal Health Monitoring System. 1996