Entamoeba histolytica

The Entamoeba histolytica parasite
This is a single cell organism (a protazoa) which forms part of the Entamoeba family. This genus contains 6 types of parasites which are found within the human digestive system but only one – the Entamoeba histolytica parasite causes this infection. This parasite exists in the form of cysts which are able to survive only for a short period of time outside their normal environment. They particularly thrive in warm or moist conditions, especially in connection with undercooked or improperly stored foods.

Causes of amoebiasis
This infection occurs as a result of ingestion or contact with parasitical cysts. These cysts are a form of the Entamoeba histolytica parasite which enter the human body through the mouth and cause amoebiasis.
Methods of transmission include:
• Consuming infected food or water
• Eating salads, fruits or vegetables which have been washed in infected water
• Contact with infected soil or animal faeces
• Handling objects which have already been infected or touching an infected surface.
Once these cysts are ingested they release smaller version of themselves in a process called ‘excystation’. ‘trophozoites’ are released which invade cells within the lining of the large intestine. These parasites burrow into the walls of the intestines causing large, crater like ulcers. This results in an infection which spreads into the bloodstream, enabling it to reach many parts of the body. The liver is usually affected but other areas include the heart, brain, lungs and spleen. Many people become infected with ‘asymptomatic amoebiasis’ In these cases, the infection remains without any symptoms: or if they are any symptoms they tend to be very mild,.here parasite lives within the digestive system but does not penetrate the cells within the intestine
Symptoms of amoebiasis
These symptoms appear very similar to bacterial dysentery although this illness is not caused by a bacteria but rather a parasite instead. But, the treatment is very similar for both bacterial and parasitical dysentery. Another common factor is good hygiene: both of these illnesses can be prevented by adopting a sensible hygiene plan.
Most people are asymptomatic in respect of this illness but there are others who, unfortunately, develop symptoms of this illness which include:
• Bloody diarrhoea
• Abdominal pain/cramps
• Lesions (within the intestinal wall)
• Tiredness
• Weight loss
• Nausea
• Vomiting
These symptoms appear between 2 to 4 weeks after first exposure to this parasite. The severity of these symptoms ranges from mild diarrhoea through to a severe, dysentery like illness with mucus and blood in the diarrhoea and a distended abdomen.
Complications of amoebiasis
• Liver abscess
• Brain abscess
• Lung abscess
Abscesses can also develop in other areas of the body. But whatever part of the body they do affect these are all serious medical conditions which require medical treatment.
Diagnosing amoebiasis
The symptoms of this are similar to bacterial dysentery or various forms of food poisoning so it easy to misdiagnose this illness.
The most efficient way of diagnosing this is to obtain a stool sample view under a microscope for signs of these parasitical cysts.
A physical examination will be performed followed by a series of tests. These include a blood test and an abnormal liver function test. Ultrasound or MRI/CT scans if the illness has spread to the liver.
Treatment for amoebiasis
This involves fluid replacement and medication (antibiotics). Medication such as metronidazole or tinidazole can be given which will ease any symptoms as well as treat liver abscesses.
Preventing amoebiasis
This parasite can infect food and water so food safety is of paramount importance. There are a few measures you can put in place to reduce the risk of amoebiasis which include:

• Washing your hands every time you visit the toilet or after you have been in contact with an infected animal.
• Ensuring that any cooked food is covered when left out to cool down
• Boiling untreated water especially when travelling or camping
• Ensuring that all food is cooked at the correct temperature
• Follow all cooking instructions carefully; this also includes microwave cooking times.
• Washing fruit and vegetables before eating them
• Washing your hands, utensils and kitchen worktops before and after food preparation.

Reference
http://www.medic8.com/healthguide/food-poisoning/entamoeba-histolytica.html