Infectious diseases - Cholera

Clinical and Epidemiological Aspects
Diagnosis
Epidemiological Surveillance
Present Situation

Clinical and Epidemiological Aspects

Cholera is an acute intestinal infection, caused by the enterotoxin of the Vibrio cholerai, whose symptoms are, in its most serious form, watery and profuse diarrhea, with or without vomiting, abdominal pain and cramps. This situation, unless quickly treated, can develop into dehydration, acidosis and circulatory collapse, accompanied by kidney failure. More frequently, the infection is asymptomatic, with light diarrhea. Breast feeding protects children from infection. The infection produces an increase of antibodies and confers immunity for a limited time (approximately 6 months). It can be confused with all acute diarrheas.

The disease is transmitted by drinking water or by ingesting foods contaminated with feces or vomit from a cholera sufferer or carrier. Person to person contamination is less important in the epidemiological chain. The El Tor variety survives in water for a long time, which increases the probability of its spreading and transmission.

The disease is subject to national and international compulsory notification, and has to be investigated epidemiologically in the event of outbreaks in all the areas where the introduction of the V. cholerae is suspected.

Epidemiological agent - Vibrio cholerae 01 of the classic biotopes and El Tor (Inaba, Ogawa or Hikogrima serotypes); and also the 0139.Bacillus negative gram.

Breeding places - Mainly human beings. Recent studies suggest the existence of environmental reservoirs (eg: seafood).

Transmission period - Lasts while the vibrio is being eliminated in the feces, usually for a few days after cure has been effected. For surveillance purposes, the accepted timeframe is 20 days. Some individuals remain healthy, even though carrying the disease for months or even years. These are significant cases because they can be responsible for introducing the disease in previously safe areas. The incubation period can vary from a few hours to five days. In the majority of cases the period of incubation is between 2 and 3 days.

Complications - Result from dehydration: hypocalcemia and hypoglycemia. It can bring on abortion. Complications can be avoided with appropriate hydration.

Diagnosis:

a) Clinical - epidemiological: cases of diarrhea in which correlated clinical and epidemiological variables determine the diagnosis, without need for laboratorial investigation.
b) Laboratorial - the Vibrio cholerae can be isolated by means of a sample culture of the feces of patients or asymptomatic carriers. Collection of the material can be carried out by rectal or fecal swab or, feces in natura or on filter paper.

Epidemiological Surveillance

Objective - To reduce the incidence and lethality; to prevent or to make propagation of the vibrio more difficult.

Case definition -

a) Suspected : in areas with no circulation of the vibrio - any individual with diarrhea, regardless of age group, with a history of having been in an area where V. cholerae has been present or an individual with a suspected or confirmed case (return to the endemic area). In areas with the V. cholerae in circulation - any individual with acute diarrhea;

b) Confirmed: by laboratory (isolation of the agent in feces or vomit); by clinical-epidemiological criteria (correlated clinical and epidemiological variables).

c) Imported: A case infected in an area different from the one in which it was diagnosed.

Control measures - Give patient plenty of good quality water to drink; ensure excrement is correctly disposed of and treated; ensure garbage is properly disposed of; health education; control of airports, ports and bus-stations; food hygiene; disposal and correct handling of corpses. To check on causal agent circulation, it is recommended to monitor environment by placing a Moores Swab in strategic places (for culture). The chemoprophylaxis of contacts is no longer indicated on account of not being effective in containing the spread of cholera cases. Moreover, use of antibiotics alters the intestinal flora and modifies susceptibility to the infection, which could cause the appearance of resistant clumps.. Vaccination is not particularly effective and offers only short term immunity. Great care must be taken with feces and the vomit of persons sharing the same living space. It is important to ensure that hands are thoroughly washed and that basic hygiene is properly observed. In cases where patients are hospitalized, enteric isolation is called for, with concurrent disinfection of feces, vomit, clothes and bed linen of patients.

Present Situation

Since 1991, Brazil has been affected by the seventh cholera pandemic which began in Indonesia in 1961, as the result of the El Tor agent. The epidemic entered the country through the Amazon Region (High Solimões area) near the Peruvian border (the agent arrived on the American continent through Peru) and spread throughout the North of Brazil down the River Solimões, the River Amazon and its tributaries). In 1992, the disease hit the North East and South East of Brazil, travelling along the main roads. At present, cholera is endemic, with local outbreaks, depending on the various conditions which favor the spread of V. cholerae.

In 1999, 61 countries notified a total of 254.310 cases, with a resulting 9.175 deaths, representing a reduction of 13% in comparison with the total recorded in the previous year. Throughout the American continent, cholera cases decreased in total by 86%. It is hoped that this downward trend will continue during the present year.