Clostridiosis consists of a group of diseases caused by members of the Clostridium species (FAO). They occur worldwide and can affect many mammalian species, including elephants. Clostridium spp. are gram-positive, rod-shaped, anaerobic bacilli. They form spores that may persist in the soil for months or years. Some of these organisms may be found in the normal flora of the digestive tract and become pathogenic only if accessible tissue is damaged as a result of deep penetrating trauma to the muscle bundles or a compromised gastrointestinal mucosa.
Clostridial organisms produce exotoxins, with local and/or systemic effect; including hemolysis and local tissue necrosis. These toxins are produced when the organism grows in the host tissues with the exception of the toxin of Clostridium botulinum, which is formed outside the body and ingested orally by the host. Some Clostridial organisms can produce multiple toxins, each with a specific activity.
Clostridiosis in elephants
The following manifestations of clostridiosis have been described in elephants:
Botulism (C. botulinum)
Tetanus (C. tetani)
Malignant edema (C. septicum)
Enterotoxemia, type C (C. perfringens, type C)
Enterotoxemia, type D (C. perfringens, type D)
Blackleg (C. chauvei)
Botulism is caused by the toxin of Clostridium botulinum (FAO). Clostridial organisms are strict anaerobes, meaning they do not grow in the presence of oxygen or in healthy, well-oxygenated tissues. Clostridium botulinum produces seven different neurotoxins, each of which is distinct and different enough from the others that antibodies against one type do not protect an animal against botulism from another type. Botulinum toxin is one of the most potent biotoxins known. Sometimes the onset of Clostridial disease is so rapid that no clinical signs are ever manifested; animals are simply found dead.
The toxin is formed by the organisms outside the elephant under certain circumstances, characterized by an anaerobic environment (pH ± 4) and an environmental temperature between 10 and 50°C (FAO). Examples of these sources are poor-quality silage or poor-quality drinking water (anaerobic conditions in a pond without streaming water).
Botulism in elephants
Botulism was first reported in Asian elephants in a German zoo (Elze 1962). One adult elephant became paralyzed and died within one day. A cause of this sudden death could not be determined. Four days later an adult herd mate started to show the first signs of paralysis. Initially the animal remained standing with the neck stretched in forward direction, mouth opened, salivating and teeth grinding. The elephant only ate some fruits and was extremely weak in all its legs and the trunk. Pulse frequency was 68/minute. The animal went down sleeping several times, but with great strength it managed to get up by itself. On the second day a Botulism-antitoxin serum (Sachsisches Serumwerken A.G. Dresden, DDR) is administered (3x50 ml s.c.). On the next the animal is given 37 x 50 ml of this antitoxin serum, partly s.c., partly intramuscular in 50-100 ml portions in a time span of 2.5 hours. The total dose given was 20-40 times the dose given to humans. No adverse reactions were observed. During the first 8 hours after the administration of the antitoxin, the elephant went down and was almost unresponsive, until it managed to stand up again with the help of human manpower. In the following hours it started eating some fruits and hay. In the following week the animal recovered completely. The diagnosis ‘Botulism’ was made based on the symptoms and the positive reaction on the administration of the Botulism antitoxine. Other drugs that were given throughout the disease episode were caffeine, metamizole, calciumgluconate, Methiovert® (?), Algopyrin®, papaverine and streptomysine-penicilline.
A second case of botulism in elephants was reported by Gart et.al (1977). Unfortunately, no details of that report could be retrieved.
In 2017 a severe outbreak was reported in a captive bachelor herd of 6 Asian elephant bulls in Spain, which resulted in the death of 5 of the elephants. For the case report “Botulism in elephants”, click here.
Botulism has been reported in horses that were exposed to botulism toxin in the feed, usually involving type B and C toxin. Toxin might be present as a contaminant in feed, or if there are droppings or carcasses of small rodents in the feed bunk or water tub. One problem occurs when rodents or other animals die in a field of forage, and a carcass is incorporated into a bale during baling. Contaminated hay cubes have been responsible for at least one large outbreak of botulism in horses. Even if a carcass has undergone dessication (it’s dried out) or is unrecognizable in a flake of hay, enough spores can remain to kill a horse.
Toxico-infectious botulism is the second most common form of botulism in horses, and this arises when the bacterium itself is ingested from soil and colonizes the gastrointestinal tract. As it grows inside the body, it produces the toxin, and signs of disease become apparent as toxin is absorbed into the bloodstream from the intestinal tract. Clostridium botulinum type B has been associated with this form of botulism.
Symptoms of botulism in elephants
The typical symptoms include flaccid muscle paralysis. The major clinical signs consisted of gradually increasing general weakness, shivering, muscle fasciculations (involuntary contractions) or trembling and shaking, particularly in the shoulder and flank muscles, mild to heavy salivation, inability to swallow and stand and properly use the trunk and dilated pupils that respond poorly on light. Death can occur within a few days as a result of respiratory distress.
Treatment, diagnosis and prevention
Treatment of botulism is very challenging: when treatment is started in the early phase of the disease, the administration of specific antitoxins might be helpful, as suggested in the 1962 case. In horses respiratory support is important, however challenging in elephants. Soft bedding should be provided. Eye protection with an eye ointment is important when the elephant has gone into lateral recumbency. During the phase of complete paralysis, the administration of oxygen through the trunk will probably support the oxygen exchange in the elephant’s lungs.
A definitive diagnosis of botulism can only be made by performing a mouse bioassay test.
Prevention: there is no commercially available vaccine against botulism, except for type B (AAEP)
Elze, K. 1962. Botulism in an elephant (Über Eine Unter dem klinischen bild des botulismus verlaufend Erkrankung beim elephanten). 4th Verhandlungsbericht Internationalen Symposiums Erkrankungen Zoo und Wildtiere, Berlin, Akademie Verlag, pp. 259–271.
Fowler M.E. 2006. Infectious diseases. In: Biology, Medicine and Surgery of Elephants, Ed. Fowler and Mikota, Chapter 11, Infectious diseases
Garlt, C., Kiupel, H. and Ehrentraut, W. 1977. Botulism in elephants (Ein beitrag zum Botulismus bei elefanten). 21st Verhandlungsbericht Internationalen Symposiums ErkrankungenZoo und Wildtiere, Berlin, Akademie Verlag, pp. 207–211.
American Association of Equine Practicioners (AAEP): https://aaep.org/guidelines/vaccination-guidelines/risk-based-vaccination-guidelines/botulism