Salmonella bacteria is one of the worst causes of this disease in cows and calves. Salmonella bacteria can affect all ages of dairy cattle, including calves, and signs of Salmonella disease take on several forms. There are many different types of Salmonella that cause disease in cattle. These different types are all part of the same species, Salmonella enterica, but are distinguished from one another based on antibody binding in the laboratory, also called serotyping. When you read about different types of Salmonella on dairies (e.g. Salmonella Newport, Salmonella Typhimurium, etc.), they are referring to the specific serotype of bacteria found on that farm. Another important point about Salmonella bacteria is that people can get infected with Salmonella also, and it can make you very sick. It is very important that people handling any animals with diarrhea wear gloves and wash hands, equipment, and clothing before eating, going home to their family, or handling other animals.
In adult cows, the most common sign of Salmonella infection is a severe, foul-smelling, bloody diarrhea, often with a high fever. One might also see chunks of a yellow material from the intestine, called fibrin. Salmonella is a very serious infection and many cows do not survive even if the infection is caught early and aggressively treated. Even cows that recover from the infection may not regain the milk production they lost during their illness, which may result in them being culled. In very severe cases, one might see cows dying with no previous indication of illness or diarrhea. Diagnosis in that case would be based on the findings of a necropsy, as well as bacterial cultures of affected tissues.
In calves, Salmonella attacks in a very similar manner, in that the most common sign of Salmonella infection in baby calves is foul-smelling, often bloody, diarrhea with a high fever. Very young calves might also get infected through the colostrum, or an infected umbilical stump, resulting in a blood-borne infection that often results in death. Salmonella also shows up occasionally in older calves, often after weaning and movement into group pens. Salmonella in these older calves often looks like pneumonia. As with many diseases that cause diarrhea, it is tempting to try to diagnose Salmonella as a cause of cow or calf scours without performing laboratory tests, such as culture. However, many different diseases look very similar, and it is important to confirm a diagnosis of Salmonella by sending a fecal culture from that animal to a laboratory for culture. Otherwise, you may end up making management changes specific to Salmonella when another pathogen is causing the diarrhea, instead of focusing on the real pathogen that is causing the problem. The best way to diagnose Salmonella infection in a cow or calf is to take a fecal sample and send in to a laboratory for culture. In most cases, the laboratory also tests different antibiotics in the laboratory to see how well they work against the Salmonella isolated from a particular case. This is called antibiotic sensitivity testing.
Treatment of Salmonella infection can be very challenging. One of the most important parts of therapy in a cow or calf is to replace all the fluids and electrolytes that the cow lost during her diarrhea. Fluids and electrolytes can be given orally or IV. Because Salmonella bacteria can sometimes hide in cells, sometimes treatment with antibiotics is not very effective because it is hard to get the medicine into the cell where the bacteria is hiding – but sometimes treatment makes a big difference. Salmonella bacteria have grown resistance to many of our antibiotics; so use the antibiotic sensitivity report to help guide a choice of antibiotic treatment. Activated charcoal given orally can help to bind toxins released by bacteria in the intestine, as well as coat and protect the intestinal tissue itself. Another important part of treating Salmonella infection is lowering the fever. A cow with a high fever does not feel good and will not eat. It is important to a cow’s recovery that they go off feed as little as possible, so keeping them comfortable and their appetites up is important. Anti-inflammatory medicines such as Flunixin meglumine or aspirin are good choices for fever. Since the conditions on every farm are different, it is best to work with the herd veterinarian to design treatment protocols that fit the individual dairy.
There are several important factors in preventing Salmonella infection: good sanitation and good overall nutrition are two of the most important. Any animals sick with diarrhea should be moved to a separate, isolated area immediately so that the Salmonella shed in the diarrhea does not infect other cows. It may also be beneficial to test any new animals coming into the herd for Salmonella before they are mixed into the herd. There are also several nutritional products that make the cows’ guts healthier, allowing them to resist Salmonella. In baby calves, it is recommended to make sure the calf gets enough colostrum from a cow that has been vaccinated against Salmonella, so that antibodies in the colostrum can be absorbed by the calf. The most important part of any Salmonella prevention and treatment program is that dairy personnel work with the veterinarian to develop a Salmonella prevention program that works for the conditions on each individual dairy. EL