Clostridial vaccines are the most widely used vaccines in the beef industry. Almost all producers use them in their young calves, usually beginning at two to three months of age, primarily to prevent the disease blackleg.
Blackleg is caused by Clostridium chauvoei bacteria and causes muscle infections that can result in sudden death in young growing calves.
These vaccines protect against seven or eight different strains of the Clostridial bacteria related to Clostridium chauvoei, which can cause very different diseases.
I want to focus on the strains of the Clostridium bacteria called Clostridium perfringens, which can cause severe bloody diarrhea in calves as well as other digestive upsets.
All of these Clostridium bacteria are present everywhere in the soil and in the intestinal tract of ruminants. They all possess the ability to generate a number of potent toxins that can cause damage to the tissues of animals, such as the intestine and cause severe diseases with sudden onset.
The Clostridium perfringens bacteria can be subdivided into multiple strains and most of our vaccines help to protect against strains C and D. Both of these strains can cause a severe bloody diarrhea when the bacteria multiply and release their toxins in the intestine of a young calf.
Type C tends to cause disease in very young calves less than 10 days of age, while Type D also affects very young calves, but can occasionally cause problems in older calves. The main clinical sign is the sudden onset of very profuse bloody diarrhea.
Calves will be listless, reluctant to nurse and may show signs of colic. The toxins that are released by the bacteria cause severe damage to the intestine and often these calves die within hours of showing clinical symptoms.
These bacteria require special circumstances to allow them to overgrow within the intestine and release their potent toxins. The bacteria are normally present in the intestine of ruminants and are considered part of the normal flora at low levels.
However, if given large amounts of carbohydrate or protein to digest and if the gastrointestinal tract suffers from some incident that causes decreased motility, then these bacteria can multiply and produce their toxins, which cause disease.
Clostridium perfringens disease episodes are usually linked to calves consuming large volumes of milk at individual feedings. The disease tends to occur in calves from dams who are exceptionally good milk producers.
The disease can also be associated with events that cause calves to stop nursing for a period of time and then take an exceptionally large feeding, such as separation of calves from dams at branding or storms or inclement weather that may delay nursing.
Intestinal motility can be negatively affected by these events as well as by coexisting infections, viral infections or coccidiosis that may play a role in creating an environment conducive to Clostridial perfringens growth.
Diagnosis of these conditions can be somewhat problematic. The clinical signs of bloody diarrhea and sudden death in young calves are certainly distinctive, but confirmation by a veterinarian and a diagnostic laboratory help to rule out other possibilities.
Culture of the feces or intestine are of limited value because Clostridium perfringens is present in normal calves and can proliferate after the death of an animal in the intestinal tract.
The only way to definitively diagnose these diseases is to submit a sample of fresh or frozen intestine to the diagnostic lab. The tests are somewhat difficult and specialized and as a result, veterinarians may rely mainly on clinical signs to make a diagnosis.
Treatment is difficult and there is limited scientific evidence to support our treatment decisions when dealing with these cases. Many calves will require intravenous fluids to help restore fluid loss, as well as to correct electrolyte imbalances.
Antibiotics are usually recommended to try to stop the overgrowth of Clostridium perfringens in the gut, and penicillin is usually the antibiotic of choice for these particular bacteria.
Some veterinarians may prescribe penicillin orally as well as giving another antibiotic such as tetracycline by injection. This combination has been suggested by some authors as somewhat effective in treating these cases.
In many cases, calves are very close to death by the time they are discovered and it can be difficult to save them. In surviving calves, it may be necessary in some cases to restore normal bacterial flora of their gut, which can be done by transferring rumen fluid from a healthy animal.
Prevention is much more easily accomplished because we have fairly effective vaccines that will immunize animals against these diseases. Most producers will vaccinate young calves at two to three months of age and again at weaning with Clostridial vaccines.
There is some evidence that in some cases this four-month gap between vaccinations may be too long and allow immunity to wane in these calves. These herds may require a booster vaccination before weaning in those circumstances. To protect the very young calves from Clostridium perfringens enteritis, producers may need to vaccinate dams to provide immunity through the colostrum.