Sidd
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Posted on 22. Dec 2023
Clostridium botulinum is gram positive anaerobic spore bearing bacilli that widely distributed in soil, sediments of lakes, ponds and decaying vegetation. Seven different strains of the organisms (A-G) are classified based on serologic specificity and another neurotoxin.Most human outbreaks are associated with fish and sea food products. Botulism in animals is predominantly due to type C and D. All toxin producing strains have placed into 4 groups.Group I contain the proteolytics, Group II the non-proteolytic and group IV serological type G. Group III consists of type C and D (Hall, McCroskey, Pincomb, & Hatheway, 1985).Epidemiology
Sporadic outbreaks occur in most countries; it has no geographical limitations. The sources of exposure to the toxin and risk for the disease differ between regions because of difference in the food storage feeding and management practices.In a study conducted in the USA, the type A was found in neutral and alkaline soil in the west while type B and C in damp or wet soil. Spores of are present throughout the world, although most of recorded outbreaks of botulism have reported in North of the tropic of cancer with exception of Argentina.The geographical prevalence of the disease necessitates some important observations such as home canning fruits and vegetables in most tropical countries (Jay, 2000; Radostits, Gay, Hinchlif, & Constable, 2007).Pathogenesis
During their growth, C. botulinum produce a high potent neurotoxin that cause neuroparalytic disease known as botulism in humans and animals without the development of histological lesion. Botulism may lead to death due to respiratory muscle paralysis unless treated properly (Jay, 2000).The toxin is released only after the death and lysis of cells. The toxin resists digestion and is absorbed by the upper part of the GI tract and then into the blood.It then reaches the peripheral neuromuscular synapses where the toxin binds to the presynaptic stimulatory terminals and blocks the release of the neurotransmitter acetylcholine. This affects muscle of respiration, which leads to death due to respiratory failure. This results in flaccid paralysis.Symptoms
Incubation period may be 12-36 hours. The most common features include vomiting, thirst, dryness of mouth, constipation, ocular paresis (blurred-vision), difficulty in speaking, breathing and swallowing. Death occurs due to respiratory paralysis within 7 days).Detection of toxin
Diagnosis of botulism requires demonstration of toxin in plasma or tissue before death or from fresh carcass. Demonstration of the toxin in feedstuff, fresh stomach content or vomitus supports diagnosis of botulism.The spoilage of food or swelling of cans or presence of bubbles inside the can indicate clostridial growth. Food is homogenized in broth and incubated in Robertson cooked meat medium and blood agar or egg yolk agar.It is incubated anaerobically for 3-5 days at 37°C. The toxin can be demonstrated by injecting intra peritoneal the extract of food or culture into mice or guinea pig (Hirsh, Maclachian, & Walker, 2004).Prevention and control
Preformed toxin in food can completely be destroyed by exposure to a temperature of 80°C for 30 minutes or boiling for 10 minutes. Therefore, all canned low acid foods should be boiled before tasting for consumption. Never taste a food if it has an odour and shows gas formation.Prevention of food borne botulism also depends on ensuring effective control of commercially and home canned foods are destroying all C. botulinum spores. This requires cooking at 121°C or higher.Vegetables that are home canned should be boiled and stirred for at least 3 minutes prior to serving to destroy botulism toxins. Foods with apparent off odours or suspected odour should not be opened (Jay, 2000).Its occurrence is worldwide particularly frequent among Alaskan populations. Case fatality ratio in industrialized countries is 5-10%.References
- Hall, J., McCroskey, L., Pincomb, B., & Hatheway, C. (1985). Isolation of an Organism Resembling Clostridium barati which Produces Type F Botulinal Toxin from an Infant with Botulism. Journal of Clinical Microbiology, 21, 654-655.
- Hirsh, D., Maclachian, J., & Walker, R. (2004). Botulism in Veterinary Microbiology (2nd ed.). Washington, DC: Blackwell Publishing.
- Jay, J. (2000). Modern Food Microbiology (6th ed.). Gaithersburg, Maryland: Aspen Publications.
- Radostits, O., Gay, C., Hinchlif, K., & Constable, P. (2007). Veterinary Medicine Text Book of Diseases of Cattle, Horses, Sheep, Pigs and Goats (10th ed.). Philadelphia: Saunders.
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