Animal Health - Botulism

Factsheet - ISSN 1198-712X   -   Copyright King's Printer for Ontario
Agdex#: 400/660
Publication Date: January 2013
Order#: 13-001
Last Reviewed:
Written by: Tim Pasma

Table of Contents

  1. Cause
  2. Clinicial Signs
  3. Treatment
  4. Protection and Management
  5. Transmission to Humans
  6. Reporting

Botulism is a rare disease that causes weakness and paralysis and can lead to the death of an animal or human. Botulism can be prevented by providing good quality feed and ensuring proper sanitation and, in humans, by following proper food canning techniques.


A bacterium called Clostridium botulinum produces the toxin that causes botulism. The bacteria produce spores that can remain inactive in the environment for a long time. When dead animals and plants decay, they create warm, moist and low-oxygen conditions that cause the spores to germinate, grow and produce toxins that affect the nervous system.

Botulism outbreaks occur when animals eat improperly stored or spoiled silage, decaying vegetation, poultry manure, or feed and water contaminated with bird or rodent carcasses. Outbreaks can also occur in large numbers of aquatic birds (Figure 1). Occasionally, the bacteria cause a disease of young foals called "shaker foal syndrome" (Figure 2). It can also infect surgical or injection sites.

Two ducks swimming on a pond.

Figure 1. Ducks can be affected by botulism. Source:

Mare with her foal standing on a pasture.

Figure 2. Botulism can occasionally cause a disease in young foals called "shaker foal syndrome".

Clinical Signs

The disease usually affects cattle, horses, sheep and birds, and rarely occurs in dogs, cats and pigs. In the early stages of the disease, animals show signs of restlessness, tremors and incoordination. In rare mild cases, animals will recover over time, but most animals become weak, paralyzed and eventually die or have to be humanely euthanized. In some outbreaks, large numbers of animals can be found dead or down over a short period of time.


Your veterinarian can diagnose and provide treatment and advice for botulism. Treatment involves providing care and support for the animals; an antiserum may be available in some areas. Treatment of botulism is usually not successful in the advanced stages of the disease. It is important to identify and remove the source of the botulism when an outbreak occurs. Clean wounds infected with botulism thoroughly.

Prevention and Management

Never give animals spoiled feed. Dispose of carcasses properly. Do not spread poultry litter on pasture that is to be grazed, baled or harvested for silage. A vaccine is available in some countries where the disease is common, but it is not available in Canada.

Transmission to Humans

Botulism in animals cannot be directly transmitted to humans. Botulism can occur in humans when the toxin is ingested or if the bacteria grow in the intestines or wounds and the toxin is released there. Food-borne botulism is spread by consuming food contaminated with the botulism toxin or spores. Foods commonly associated with botulism include inadequately home-canned foods with low acid content, such as asparagus, green beans, beets and corn; and lightly preserved foods such as fermented, salted or smoked fish and meat products. Cases of botulism have also occurred in infants; some of these cases have been traced to the feeding of raw honey contaminated with botulism spores.

Symptoms of botulism in humans include blurred or double vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth and weakness. If untreated, these symptoms may progress to paralysis and death.

People with symptoms of botulism should immediately seek medical attention.


Veterinary laboratories in Ontario and veterinarians who use a laboratory outside of Ontario must notify the Ontario Ministry of Agriculture and Food and Ministry of Rural Affairs (OMAF and MRA) if a case of botulism is diagnosed in Ontario. OMAF and MRA will work with veterinarians to ensure that the disease is being controlled in animals.

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