Botulism is a severe illness caused by potent toxins produced by a highly lethal toxin produced by the bacteria,Clostridium botulinum. The bacteria grow in low oxygen (anaerobic) environments. The bacteria is also found in soil which multiplies in rotting vegetation or carcasses. Botulin toxins are the most potent known. Illness occurs either by ingesting the toxin or the bacteria (which grows and then produces toxin). Botulism affects many species, including humans. The signs of illness are the same in all. The onset is rapid and can be fatal without treatment.
Botulism is a paralyzing disease which kills most affected animals. Once it is absorbed the toxin travels via the bloodstream to the nerve endings and blocks the transmission of nerve impulses to muscles resulting in paralysis. Animals that can be affected by botulism toxin include cattle, sheep, horses, mink, and ferrets. The disease also affects humans. Outbreaks in waterfowl are common. Botulism can be confused with hypocalcaemia or milk fever. Milk fever generally occurs in recently-calved older cows and the response to calcium injection is usually rapid
Botulism usually involves multiple cases, has no association with calving and does not respond to calcium injections. Ephemeral fever (3 day sickness) can also resemble botulism but affected animals usually have a fever and are usually down for only a few days. They often improve with calcium injections and cases tend to be seasonal affecting many herds within a region.
Toxin detection in feeds or animal tissues is usually unrewarding. C. botulinum is found worldwide within the intestinal tracts of mammals and fish and can also be found in soil or sediment.
- Animals become infected by ingesting vegetation that is contaminated with the botulin toxin (such as decaying hay or grain)
- Through direct contact with soil that contains the bacteria.
- Cattle or sheep that are phosphorus (a mineral) deficient are prone to chew on bones increasing their chance of ingesting botulin bacteria or its toxin from the environment.
Symptoms and Diagnosis
- Botulism causes a progressive paralysis and animals die of respiratory failure from paralysis of the breathing muscles.
- Affected cattle tend to have a stiff gait and saliva drools from their mouth.
- They are usually found sitting down, unable to rise and their breathing becomes progressively more labored.
- Frequently they extend their hind legs behind them in a frog legged position to make breathing easier.
- Some animals have tongues that hang out and do not retract when pulled.
- Animals affected early in the outbreak tend to have a short clinical course (12-24 hours) and die quickly but later in the outbreak they can have a longer clinical course and some may even survive. Losses can be seen for up to 17 days after ingestion of a contaminated feed.
- Diagnosis: The diagnosis of botulism is difficult early in an outbreak when losses are not great. Laboratory tests are often falsely negative and there are no specific lesions seen at autopsy. In extensive areas, bones may be found in the stomach indicating bone chewing. Usually the diagnosis is a clinical one based on the symptoms, the history and the exclusion of an alternate diagnosis by laboratory tests.
Treatment and control
There is no specific treatment for animals affected by botulism only supportive treatment. Because the symptoms are due to a toxin rather than a bacteria there is little rationale to the use of antibiotics. Animals should be given shade. They may not be able to eat or drink if paralysis is advanced.
- The main preventative strategy is to vaccinate the herd. Single dose and two dose vaccines are available and it is recommended that producers talk to their animal health advisor (Mokenti) to get assistance in choosing the appropriate vaccination program for their particular situation. Once an outbreak has started, vaccination is unlikely to make much of an impact, so it is important to vaccinate on a regular basis before you get a problem.
- In the pastoral areas where botulism is endemic vaccination is widely adopted and it provides good protection. In the intensive industries botulism is still uncommon but for individual producers the financial consequences can be dire and vaccination is recommended for all producers who are feeding cattle silage, grain, by-products or mixed rations.
- Preventing stock access to animal carcasses.
- Controlling animals to reduce the risk of spread of putrid material.
- Providing nutritional supplements of protein and phosphorus to reduce bone chewing among pastoral-zone cattle.
- Taking care with the harvesting and storage of feeds to reduce the possibility of small animals contaminating feeds.
- Checking water sources for organic matter contamination.
Effects of Botulism in humans
People can get botulism, but not by direct contact with other people or animals. People are infected by ingesting(oral) food containing the toxins or the bacteria itself. Reported outbreaks have occurred most commonly from home-canned vegetables and fish, sausage, and honey. Exposure can occur by direct contact of wounds or cuts with contaminated soil, but this is rare. Botulism in humans has a rapid onset (18 to 36 hours). Initiallyyou may have nausea, vomiting and abdominal pain.This rapidly develops to paralysis starting in the head and neck region and moves down the body to the arms, legs and chest. This can lead to difficulty breathing and possibly death.