Botulism is caused by botulinum neurotoxin of Clostridium botulinum. Predominantly type C, but occasionally type A and E are seen. Botulinum neurotoxin cleaves the SNARE proteins, preventing neurotransmitter release resulting in flaccid muscle paralysis. This condition most commonly affects waterfowl but has been seen sporadically in poultry. Clostridium botulinum grows in warm (86 to 98.6 C) oxygen-free conditions such as in decaying vegetation in warm stagnant water, carcasses, or infected wounds. Toxin exposure may be from consuming preformed toxins that bioaccumulate in insects or rotting food or toxin forming Clostridium botulinum bacteria actively living in the body.
The severity and onset of symptoms are dependent on how much toxin is consumed. Patients initially develop pelvic limb weakness that progresses to paralysis of the wings, neck, and eyelids over the course of hours to days. A large enough dose of the toxin can lead to suffocation due to paralysis of muscles of breathing. Waterfowl may also drown due to the inability to lift their head out of the water. Poultry may exhibit labored breathing, fluffed feathers, and diarrhea with excessive urates (white part of the droppings). In many cases, multiple birds are affected at once.
Similar symptoms can be seen with lead or ionophore toxicity. Infections such as duck viral enteritis, fowl cholera, avian influenza, or Marek’s disease in chickens can also appear similar clinically. Limb or spinal trauma or vitamin B deficiency may also mimic this condition.
A definitive diagnosis is made by detecting the toxin in serum via an ELISA test. However, generally, this condition is diagnosed via clinical history and lack of clinical findings that would suggest other diagnoses. X-rays may be recommended to rule out trauma or check for evidence of ingested heavy metals such as lead. Complete blood count and serum biochemistry testing is often normal but will rule out infection as a cause.
Botulism is treated with hospitalization on IV fluids, administration of Botulism Type C Antitoxin, and activated charcoal or cholestyramine to adsorb the type A botulinum neurotoxin. Antibiotics are only warranted when the toxin is as the result of wound infection. When wounds are suspected to be the source, surgical debridement and flushing of wounds should be performed as well. Affected birds should be removed from environments where drowning or predation can occur and kept warm. Assist feeding and intravenous fluids should be given until the bird can eat and drink. The source of the toxin should be invested and removed from the environment as well.
The prognosis is poor to grave depending on the dose ingested. If the Antitoxin is available for treatment, the prognosis improves to fair.
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