Prevention and Treatment Techniques for Botulism in Mink

Botulism is an acute poisoning disease in mink caused by the exotoxin of Clostridium botulinum. It is characterized by muscle relaxation and paralysis of the limbs.

1. Pathogen

The pathogen of this disease is Clostridium botulinum, an anaerobic large bacillus that can produce 6 types of exotoxins (A, B, C, D, E and F) during reproduction, and the antigenicity of these toxins differs. The toxin is extremely virulent; 1 milligram of purified toxin contains approximately 10,000 human lethal doses or can kill 4×1000000000000 mice. Most studies have shown that mink poisoning is mostly caused by type C toxin.

2. Epidemiological Characteristics

This disease has no seasonality and can occur in all four seasons. The main source of infection for mink botulism is feed contaminated with this bacterium. When meat and fish feed is contaminated with Clostridium botulinum, large amounts of exotoxin are produced during storage, and mink become poisoned after eating it. Feed containing the toxin shows no abnormal appearance and is difficult to detect; even when this toxin-containing feed is stored in a low-temperature cold storage facility, the toxin is not destroyed. Therefore, the disease can occur in all four seasons, and animals of all ages and both sexes are susceptible.

3. Clinical Symptoms

The incubation period of this disease is 8-10 hours, rarely 24 hours. After being fed toxin-containing feed, large numbers of mink in the herd become ill and die. Most cases are peracute and acute, and the course of illness in longer cases is 2-3 days and nights.

Sick mink show inflexible movement, lie down and remain inactive, with the hindquarters becoming paralyzed first, gradually spreading to the forelimbs, and finally general paralysis, unable to stand. The muscles are highly relaxed, and when placed on the hand they hang down like a sock. Sick mink drool, foam at the mouth, have dilated pupils, protruding eyeballs that do not move, occasionally make crying sounds, rarely have diarrhea or vomiting, and generally die in a comatose state. A few have no symptoms before death and die suddenly from convulsions.

4. Anatomical and Pathological Changes

This disease shows no characteristic changes on necropsy. The carcass is in good nutritional condition, the gastrointestinal tract is empty, and there is rarely congestion and hemorrhage. The liver is congested and peach-colored, the kidneys are discolored, and there is hemorrhage in the lungs and pleura.

5. Diagnosis

A preliminary diagnosis can be obtained based on the sudden onset, mass deaths and the appearance of typical clinical symptoms such as muscle relaxation, paralysis and incomplete paralysis. For a confirmed diagnosis, the leftover feed and dead carcasses must be sent to the relevant laboratory to check for the presence of Clostridium botulinum toxin.

6. Prevention and Treatment

This disease often causes sudden onset and death, with no time for treatment. Generally there is no specific drug available, and antibiotics also have no good effect. The main approach is to prevent the occurrence of this disease. For specific prevention, Clostridium botulinum type C toxoid can be injected, 1 milliliter for all animals regardless of age. Prevent feed from being contaminated with Clostridium botulinum; meat feed should not be piled up at room temperature of around 10°C for too long. Suspected feed should be fed on a trial basis after high-temperature treatment.

When the toxin type has not been determined, polyvalent antitoxin serum can be used for treatment, administered intravenously or intramuscularly. Symptomatic treatment: use 5% sodium bicarbonate solution or 0.1% potassium permanganate solution for enema and gastric lavage, because Clostridium botulinum toxin is easily destroyed under alkaline conditions and its virulence is easily weakened under oxidation.