Shigellosis Health Dictionary

A clinical state arising from invasive colo-rectal disease; it is accompanied by abdominal colic, diarrhoea, and passage of blood/mucus in the stool. Although the two major forms are caused by Shigella spp. (bacillary dysentery) and Entamoeba histolytica (amoebic dysentery), other organisms including entero-haemorrhagic Escherichia coli (serotypes 0157:H7 and 026:H11) and Campylobacter spp. are also relevant. Other causes of dysentery include Balantidium coli and that caused by schistosomiasis (bilharzia) – Schistosoma mansoni and S. japonicum infection.

Shigellosis This form is usually caused by Shigella dysenteriae-1 (Shiga’s bacillus), Shigella ?exneri, Shigella boydii, and Shigella sonnei; the latter is the most benign and occurs in temperate climates also. It is transmitted by food and water contamination, by direct contact, and by ?ies; the organisms thrive in the presence of overcrowding and insanitary conditions. The incubation is between one and seven days, and the severity of the illness depends on the strain responsible. Duration of illness varies from a few days to two weeks and can be particularly severe in young, old, and malnourished individuals. Complications include perforation and haemorrhage from the colo-rectum, the haemolytic uraemic syndrome (which includes renal failure), and REITER’S SYNDROME. Diagnosis is dependent on demonstration of Shigella in (a) faecal sample(s) – before or usually after culture.

If dehydration is present, this should be treated accordingly, usually with an oral rehydration technique. Shigella is eradicated by antibiotics such as trimethoprimsulphamethoxazole, trimethoprim, ampicillin, and amoxycillin. Recently, a widespread resistance to many antibiotics has developed, especially in Asia and southern America, where the agent of choice is now a quinolone compound, for example, cipro?oxacin; nalidixic acid is also e?ective. Prevention depends on improved hygiene and sanitation, careful protection of food from ?ies, ?y destruction, and garbage disposal. A Shigella carrier must not be allowed to handle food.

Entamoeba histolytica infection Most cases occur in the tropics and subtropics. Dysentery may be accompanied by weight loss, anaemia, and occasionally DYSPNOEA. E. histolytica contaminates food (e.g. uncooked vegetables) or drinking water. After ingestion of the cyst-stage, and following the action of digestive enzymes, the motile trophozoite emerges in the colon causing local invasive disease (amoebic colitis). On entering the portal system, these organisms may gain access to the liver, causing invasive hepatic disease (amoebic liver ‘abscess’). Other sites of ‘abscess’ formation include the lungs (usually right) and brain. In the colo-rectum an amoeboma may be di?cult to di?erentiate from a carcinoma. Clinical symptoms usually occur within a week, but can be delayed for months, or even years; onset may be acute – as for Shigella spp. infection. Perforation, colo-rectal haemorrhage, and appendicitis are unusual complications. Diagnosis is by demonstration of E. histolytica trophozoites in a fresh faecal sample; other amoebae affecting humans do not invade tissues. Research techniques can be used to di?erentiate between pathogenic (E. dysenteriae) and non-pathogenic strains (E. dispar). Alternatively, several serological tests are of value in diagnosis, but only in the presence of invasive disease.

Treatment consists of one of the 5nitroimidazole compounds – metronidazole, tinidazole, and ornidazole; alcohol avoidance is important during their administration. A ?ve- to ten-day course should be followed by diloxanide furoate for ten days. Other compounds – emetine, chloroquine, iodoquinol, and paromomycin – are now rarely used. Invasive disease involving the liver or other organ(s) usually responds favourably to a similar regimen; aspiration of a liver ‘abscess’ is now rarely indicated, as controlled trials have indicated a similar resolution rate whether this technique is used or not, provided a 5-nitroimidazole compound is administered.... dysentery

Increased fluidity, frequency, or volume of bowel movements. It may be acute or chronic. Diarrhoea can be very serious in infants and elderly people because of the risk of severe, potentially fatal, dehydration.

Acute diarrhoea is usually a result of consuming food or water contaminated with certain bacteria or viruses (see food poisoning). Infective gastroenteritis also causes diarrhoea and may be acquired as a result of droplet infection. Other causes of acute diarrhoea include anxiety and, less commonly, amoebiasis, shigellosis, typhoid fever and paratyphoid fever, drug toxicity, food allergy, and food intolerance.

Chronic diarrhoea is generally repeated attacks of acute diarrhoea. It may be the result of an intestinal disorder such as Crohn’s disease, ulcerative colitis, cancer of the colon (see colon, cancer of), or irritable bowel syndrome. Diarrhoea that recurs, persists for more than a week, or is accompanied by blood requires medical investigation.

The water and electrolytes (salts) lost during a severe attack of diarrhoea need to be replaced to prevent dehydration. Ready-prepared powders of electrolyte

mixtures can be bought (see rehydration therapy). Antidiarrhoeal drugs, such as diphenoxylate and loperamide, should not be taken to treat attacks of diarrhoea due to infection; they may prolong it. Drugs may help if the diarrhoea is disabling or if there is abdominal pain.

Viral gastroenteritis in a child can damage the lining of the intestine, which may lead to lactose intolerance and further diarrhoea. Seek medical attention if diarrhoea in an infant persists for more than 48 hours. Call a doctor urgently if the infant is dehydrated. (See also rehydration therapy.)... diarrhoea

Diseases prevalent in the tropics because of living conditions and diet include malnutrition, measles, diphtheria, tuberculosis, typhoid fever, shigellosis, cholera, amoebiasis, and tapeworm infestation.

Diseases spread through the tropics by insects include malaria, yellow fever, sleeping sickness, and leishmaniasis.

Exposure to strong sunlight in the tropics causes an increased tendency to skin cancer, and may lead to pinguecula and pterygium.... tropical diseases

Acquired immune deficiency syndrome, a deficiency of the immune system due to infection with HIV (human immunodeficiency virus). In most countries, illness and death from is a growing health problem, and there is, as yet, no cure or vaccine.

does not develop in all people infected with. The interval between infection and the development of is highly variable. Without treatment, around half of those people infected will develop within 8–9 years.

is transmitted in body fluids, including semen, blood, vaginal secretions, and breast milk. The major methods of transmission are sexual contact (vaginal, anal, or oral), blood to blood (via transfusions or needle-sharing in drug users), and mother to fetus. has also been transmitted through blood products given to treat haemophilia, artificial insemination by donated semen, and kidney transplants; but improved screening has greatly reduced these risks. is not spread by everyday contact, such as hugging or sharing crockery. The virus enters the bloodstream and infects cells that have a particular receptor, known as the CD4 receptor, on their surface. These cells include a type of white blood cell (a CD4 lymphocyte) responsible for fighting infection and cells in other tissues such as the brain. The virus reproduces within the infected cells, which then die, releasing more virus particles into the blood. If the infection is left untreated, the number of CD4 lymphocytes falls, resulting in greater susceptibility to certain infections and some types of cancer.

Some people experience a short-lived illness similar to infectious mononucleosis when they are first infected with. Many individuals have no obvious symptoms; some have only vague complaints, such as weight loss, fevers, sweats, or unexplained diarrhoea, described as -related complex.

Minor features of infection include skin disorders such as seborrhoeic dermatitis. More severe features include persistent herpes simplex infections, oral candidiasis (thrush), shingles, tuberculosis, and shigellosis. may also affect the brain, causing a variety of neurological disorders, including dementia.

Certain conditions, known as AIDSdefining illnesses, are characteristic of full-blown. These include cancers (Kaposi’s sarcoma and lymphoma of the brain), and various infections (pneumocystis pneumonia, cytomegalovirus infection, toxoplasmosis, diarrhoea due to CRYPTOSPORIDIUM or ISOSPORA, candidiasis, disseminated strongyloidiasis, and cryptococcosis), many of which are described as opportunistic infections.

Confirmation of infection involves testing a blood sample for the presence of antibodies to. Diagnosis of fullblown is based on a positive test along with the presence of an AIDSdefining illness.

The risk of infection with can be reduced by practising safer sex. Intravenous drug users should not share needles. There is a small risk to health workers handling infected blood products or needles, but this risk can be minimized by safe practices.

Treatment of infection with a combination of antiviral drugs can slow the disease’s progress, and may prevent the development of full-blown. The 2 main types of antiviral drug used are protease inhibitors, such as indinavir, and reverse transcriptase inhibitors such as zidovudine. Treatment is also available for -defining illnesses.... aids

The passage of blood from the rectum or anus. The blood may be red, dark brown, or black. It may be mixed with, or on the surface of, faeces or passed separately, and there may be pain. Haemorrhoids are the most common cause of rectal bleeding. Small amounts of bright red blood appear on the surface of faeces or on toilet paper. Anal fissure, anal fistula, proctitis, or rectal prolapse may also cause rectal bleeding.Cancer of the colon (see colon, cancer of) or the rectum (see rectum, cancer of), or polyps can also cause bleeding. Disorders of the colon such as diverticular disease may cause dark red faeces. Black faeces (melaena) may be due to bleeding high in the digestive tract. Bloody diarrhoea may be due to ulcerative colitis, amoebiasis, or shigellosis. Diagnosis may be made from a rectal examination, from proctoscopy, sigmoidoscopy, colonoscopy, or a double-contrast barium X-ray examination.

rectal examination Examination of the anus and rectum, performed as part of a general physical examination, to assess symptoms of pain or changes in bowel habits, and to check for the presence of tumours of the rectum or prostate gland. rectal prolapse Protrusion outsid.

nent in elderly people. If the prolapse is large, leakage of faeces may occur.

Treatment is with a fibre-rich diet.

Surgery may also be performed.... rectal bleeding