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Botulism - Cow      Botulism - Swan      Botulism - Horse


Botulism is a disease caused by ingesting Clostridium botulinum toxin and has been described in most animal species and occasionally in people. The disease is caused by consuming material contaminated by a toxin produced by Clostridium botulinum bacteria. There are 7 types of C botulinum toxins in existence (Types A, B, C1, D, E, F and G) and different toxins tend to be responsible for the disease in animals and people. Type D and C toxins are more commonly found in animals and wild bird botulism cases. Humans are considered refractory. Botulism cases in people are generally caused by toxin types A, B, E and rarely F and are usually not linked to animal production.

The bacteria that produces Type D and C toxin readily multiplies in decaying animal and sometimes plant material. Horses, cattle, chickens and waterfowl are most susceptible to Botulism intoxication while cats, dogs and pigs are more resistant. Disease relating to toxins Type F and G is uncommon in either people or animals.There is no vaccine licenced for use in the EU or specific treatment for Botulism intoxication and Prevention (as detailed below) remains the only effective control.

What to look for?

Outbreaks of botulism have occurred in cattle and waterfowl in Ireland in recent years often involving significant numbers of animals.  Outbreaks tend to occur typically between March and November and are often associated with warm weather. However winter outbreaks have occurred in association with contaminated silage.

Clinical Signs include:

  • Progressive Weakness
  • Posterior Ataxia
  • Progressive Flaccid Paralysis
  • Drooling
  • Animals are Generally Alert
  • Difficulty Swallowing
  • Death

What to do if you suspect your stock is affected by Botulism?

Contact your Veterinary Surgeon.

(i) Botulism Information Note for Vets & Farmers and
(ii) Instructions for Veterinary Surgeons

Often a presumptive diagnosis is made on clinical signs only however it is important to use laboratory testing, to demonstrate where possible, which neurotoxins are involved. Most frequently Type D and C toxins are demonstrated in these incidences. There is no vaccine licenced for use in the EU and no specific treatment other than supportive therapy of clinical signs is indicated. The only effective Control against Botulism is Prevention.


This requires minimising animal contact with carrion and decaying matter and preventing ingestion of feedstuffs contaminated with decaying materials where possible such as:

(i) Decaying grasses or spoiled silage, hay, or grains
N.B. Be aware of the potential for small quantities of contaminated feed (e.g. one loader scoop) to reach larger numbers of animals when using feeder/mixer wagons.
(ii) Decaying animal/ bird carcasses in feedstuffs e.g. silage pits/bales, grain stores, or on grassland,

Wildlife and poultry carcasses can produce particularly high levels of toxins and inappropriate storage or disposal of poultry litter or poultry carcasses can pose a risk of Botulism for animals.

Both Poultry Producers, Farmers and Hauliers who transport and spread poultry litter on or adjacent to farmland should adhere to Codes of Good Practice for:

(iii) Legal Obligations and Code of Good Practice Guidelines for Poultry Farmers (pdf 254Kb) 
(iv) Legal Obligations and Code of Good Practice Guidelines for End Users of Poultry Litter (pdf 141Kb) 
(V) Legal Obligations and Code of Good Practice Guidelines for Poultry Litter Hauliers (pdf 243Kb) 

Botulism is not a notifiable disease in Ireland, but cases should be reported your local DVO or Regional Veterinary Laboratory so the incidence of the disease in Ireland is monitored.

Further advice may be sought from your Regional Veterinary Laboratory, Local District Veterinary Office (DVO) or the Central Veterinary Research Laboratory at (01) 6157100.