Disentery, Shigella and Amoebae

Category : Farming / Food production, fecal contamination, food hygiene, Food Microorganisms, food poisoning, Food Processing / Packaging, food toxins, irrigation, Miscellaneous, Water Quality
Disentery, Shigella and Amoebaeby Andrew Routledgeon.Disentery, Shigella and AmoebaeMost of us in the western world think of dysentery or “Shigella” as a disease of the summer months. Have you ever thought why? Firstly, is it true? Is dysentery a disease of the summer months? Ok, now I’m going to confuse you a little more because the answer is yes and no. No because […]




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Most of us in the western world think of dysentery or “Shigella” as a disease of the summer months. Have you ever thought why? Firstly, is it true? Is dysentery a disease of the summer months?

Ok, now I’m going to confuse you a little more because the answer is yes and no. No because dysentery is not only a disease of the summer months and yes because it is mostly proliferated throughout the western world during the summer months, but why?

Dysentery is a disease that is spread via contaminated food and water. A lot of our summer produce is picked in warmer regions of the world where the water sourses osed to irrigate and to wash produce before packing may not be of the best quality and may contain many contaminants. In addition, workers who pick and pack produce may be carriers of certain types of dysentery causing bacteria.

Another major cause of dysentery during summer months for westerner’s is travelling to warmer climates. Whereas locals in many areas of the world may have developed immunities to many bacterial and protozoic species, all of these may be new for us. By being tempted to eat as the locals do we are often exposing ourselves to sources of food and water contamination.

Dysentery is caused by several major causes lets have a look at a couple of them.

Bacterial Dysentery. Bacterial dysentery is caused primarily by the bacterium Shigella dysenteriae. The disease it causes is called shigellosis. This bacterium is a gram negative, non motile, rod shaped, non spore forming facultative anaerobic species that produces a toxin called shiga toxin which is what causes the reaction which we know as dysentery.

Allow me to translate that mouthful of scientific jargon for you. Firstly Gram testing is a form of bacterial staining devised by a man called Mr. Gram which adheres to proteinous outer shells but not to fatty shells. As the vast majority of gram negative bacteria have a Lipopolysaccharide outer shell the dye will not stick, therefore the bacteria are classified as gram negative. Non motile means that they have no mechanism by which they can propel themselves within the medium they are in. Non spore forming means that the bacterium does not have the capability of reducing it’s structural size to permit it to survive periods when conditions are not suitable for bacterial growth, hibernating in short. Facultative anaerobic means that it can live in an oxygen rich environment or in one which is void of oxygen. It is usually when in the anaerobic phase that facultative bacteria will produce their toxins.

The symptoms of dysentery are high fever, vomiting, diarrhea, severe dehydration. Shega toxin is a potentially deadly toxin. Patients with dysentery may experience projectile diarrhoea and projectile vomiting simmultaneously. This is a very unpleasant condition which I have experienced personally. With this disease fluid intake is vital even if that means via infusion and a strict hygiene regeme is vital to rule out the possibility of re infection. Recovery usually takes anything between one to two weeks but in many areas of the world high mortality is common due to improper conditions with which to treat this condition. Mortality rate is particularly high in children and the elderly.

Amoebic Dysentery. This form of dysentery is also spread by the ingestion of contaminated food and water. It is caused by a cyst forming amoebic species. The disease is called intestinal amoebiasis.

This disease is most common in the developing world but not only. One case was reported in St. Petersburg which is quite close to the artic circle. Both bacterial and Ameobic Dysentery are prevelant in developing countries and often get confused. Most cases of travellers dysentary are in fact bacterial or viral in origin. Amoebic dysentery is a parasitical disorder and will not be effected by antibiotics. This form of dysentery may cause infection and enlargening of the liver and blood in stools. Other symptoms remain very much the same as in bacterial dysentery. Metronidazole is the preferred treatment for Amoebic Dysentaty.

Note. Not all species of amoebae are cyst forming.



Author: 

Andy has many years of experience in food preparation, Food Hygiene, Catering and staff Training

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