Botulism is a rare and strange disease. Occasional cases can be seen in individual animals or as a herd outbreak due to contaminated feed or water. A herd outbreak in goats was reported in South America secondary to a diet too low in phosphorus – the goats started chewing bones of dead animals to meet their mineral needs, but meat on the bones was contaminated with the botulism toxin.
Botulism is caused by toxin(s) produced by the bacterium Clostridium botulinum. This organism and its spores are very common in soil, water sediment, and mammalian intestinal tracts. Mammals can contract the disease three ways:
- Animals ingest pre-formed toxin in contaminated feed or water (most common means)
- In the absence of oxygen, C. botulinum contaminates wounds, abscesses, or damaged tissues and produces toxin
- Intestinal C. botulinum “activates” and produces toxin
The most common sources of pre-formed toxins that result in foodborne botulism include carcasses of animals that died from botulism; decaying plant material, including hay, grain, or silage; and water, soil, or feedstuffs contaminated by such carcasses or decaying plant material. A case of equine botulism was attributed to grass lawn clippings placed in black garbage bags and given to the horse over a period of a few days. Being in an unsealed garbage bag meant the grass neither dried down to hay nor fermented properly into silage; it rotted in the bag and created the perfect environment for C. botulinum spores to activate and produce toxin.
Signs of botulism can include generalized weakness, inability to stand or hold the head up, twisted necks, and recumbency. Animals have difficulty eating, chewing, and swallowing. In the early stages, they may show voice changes, muscle tremors, and uncoordinated gaits. They may lie down with their chin resting on the ground because they can’t support the weight of their head. Excessive drooling, regurgitation, urine retention, and progressive paralysis are often seen; aspiration pneumonia secondary to paralysis is common. There are eight types of C. botulinum toxins, and signs of toxicity vary depending on the specific toxin involved. Some forms cause gastrointestinal signs without significant paralysis.
Diagnosis relies on identifying botulism toxin in feed, intestinal contents, or other samples. However, a presumptive diagnosis can be based on clinical signs, ruling out other neurologic diseases and/or finding the organism in feed or patient samples.
Treatment is often fruitless; outcomes are usually grave if animals are recumbent. Supportive nursing care, stomach lavage, and enemas to remove toxin and botulinum antitoxin may be helpful. In the case of wound botulism, antibiotics and debridement are indicated. A vaccine is available for use in high-risk areas, but it is approved for use only in horses. Its use in goats would require working with your veterinarian regarding appropriate dosage, route of administration, and meat and milk withholding times.
Fortunately, botulism toxins are deactivated by sunlight within a few hours. They are also destroyed by a 0.1% bleach solution or boiling for 10 minutes. C botulinum is killed by a 1% bleach solution or 70% ethanol. The spores are very resistant but can be deactivated by 248°F of moist heat for at least 15 minutes. This is important information for home canners to prevent botulism through improperly processed food preservation at home.