Don’t Forget Tetanus Prevention When Banding! Michelle Arnold Associate Professor, Ruminant Veterinarian
In the United States, more than 17 million bulls are castrated yearly that range in age from 1 day to 1 year-old. Tetanus is a life-threatening neurologic disease that can develop after castration, especially when banding heavier, older bulls. The disease results from wound contamination by soil containing spores of the Gram-positive bacterium Clostridium tetani. The early symptoms of tetanus are subtle and may include any or all of the following: straight stiff legs, ears held back toward the poll, moderate bloat, an erect tail, and an unusual “flick” of the third eyelid across the eye. Recognition of the initial signs leads to an accurate early diagnosis and allows treatment to begin when it is most effective. Any calf castrated with an elastrator band should be given tetanus prevention in the form of either tetanus toxoid (two doses required with the 2nd given two weeks prior to castration), tetanus antitoxin (given the day of banding or shortly after) or, in some cases, both are used concurrently or sequentially. Calves banded while very young are less likely to develop tetanus because the testicles are smaller and the scrotal sac falls off more quickly than in older calves, allowing little time for the tetanus organism to grow and produce toxin. Additional benefits of early castration by any method include a lower risk of bleeding and infection, the risk of injury to the person performing the castration is reduced, and the procedure is relatively quick and easy. In the soil, C. tetani can survive for years in its “spore” form which has an outer coat that protects it from being killed by disinfectants, drying, heat or freezing. The spores are found in neutral or alkaline soils and typically warm, humid environments but may also be passed in the feces of domestic animals, especially horses. Wounds in parts of the body in contact with soil are most at risk for contamination. These wounds may be small and hard to find and tetanus can even develop after wound healing. When spores enter deep wounds with little exposure to air and dead tissue surrounds the area, the spores germinate into actively growing bacteria and rapidly produce the neurotoxin TeNT. The toxin binds to the nerve endings and travels back to the spinal cord, causing a condition called “spastic paralysis” in which the muscles become hyperactive, rigid and stay contracted. Management practices that may create environments perfect for germination of C. tetani spores include elastrator band castration and dehorning, nose ring placement, tail docking, and injections with dirty needles. The incubation period, or time from contamination to development of first symptoms, averages seven to ten days but can be longer or shorter. The first detectable sign of tetanus in 18 • Cow Country • August
cattle is usually leg stiffness and reluctance to move. As the disease progresses, a stiff, stilted walk develops and the calf resembles a sawhorse when standing still due to muscle rigidity. A “pump-handle tail” is often described in which the animal’s tail is stiff and raised away from the body because of the rigid muscles along the lower spine. When the head and neck muscles go into extension, an affected calf may extend his head, flare his nostrils, the ears may stand up and then be pulled back towards the poll, and the eyelids may be held wide open so much of the white (sclera) is showing. Most producers will describe a “strange-looking eye blink” which is actually prolapse of the nictitans. This “flick” of the third eyelid is caused by spasm of the muscles pulling the eyeball inward and allowing the third eyelid to passively move across the eye. Rigidity of the jaw (masseter) and facial (temporal) muscles results in the inability to open the mouth (“trismus”) which is how tetanus got the nickname “lockjaw”. Affected cattle usually lose the ability to eat and drink, resulting in progressive weakness and dehydration. Rumen contractions become weak or disappear and cattle frequently bloat because they lose the ability to eructate (burp off) gas. Subtle muscle tremors may be seen early, but are much more obvious in later stages of disease. Convulsions may be triggered by loud noises, by handling the animal, or may occur spontaneously. Affected animals finally become recumbent (down on their side) and unable to rise due to stiffness of the legs and the inability to pull their legs underneath them. If left untreated, severe dehydration and death occur quickly. Even with supportive care, death may result from paralysis of diaphragm and respiratory muscles causing respiratory failure in 5-9 days or from bloat. The case history and distinctive clinical signs of
tetanus found on a routine physical examination are usually enough to make a diagnosis as there are no reliable diagnostic tests to confirm the disease. Basic principles for medical management of tetanus cases in cattle are to provide muscle relaxation, neutralize the circulating unbound TeNT toxin, begin establishment of active immunity, eliminate the C. tetani infection with antibiotics, maintain hydration and nutritional status, and provide good footing with deep bedding. Tranquilization by a veterinarian with sedatives such as acepromazine in the muscle will allow some muscle relaxation and help to control excessive sensitivity to stimuli, allowing easier treatment. Tetanus antitoxin, available over-the-counter and on the Internet, may catch and inactivate any circulating toxin but cannot undo the effects of toxin already bound to nerve receptors. The dose for tetanus antitoxin has a wide range from 10,000-50,000 units per animal but generally 15,000 units administered under the skin is recommended for initial therapy. To initiate production of antitoxin antibodies, a dose of tetanus toxoid should also be given. Once the wound or infection site is identified, then it must be thoroughly cleaned to remove all dead tissue and should be flushed with hydrogen peroxide to reduce toxin production by any remaining actively growing bacteria. In a recently banded calf showing signs of tetanus, the scrotal sac should be assessed by a veterinarian and removed if possible, and the area cleaned and flushed with peroxide. Penicillin G is usually recommended at an extra-label dose for at least 5-7 days. Good nursing care is very important to survival of tetanus patients. The animal should be placed in a stall with deep bedding to prevent “bedsores” and good footing to help them stand. The
