Cryptosporidiosis

Cryptosporidiosis (crypto) is an illness caused by a parasite. The parasite lives in soil, food and water. It may also be on surfaces that have been contaminated with waste. You can become infected if you swallow the parasite.The most common symptom of crypto is watery diarrhea. Other symptoms include

• Dehydration
• Weight loss
• Stomach cramps or pain
• Fever
• Nausea
• Vomiting

Most people with crypto get better with no treatment, but crypto can cause serious problems in people with weak immune systems such as in people with HIV/AIDS. To reduce your risk of crypto, wash your hands often, avoid water that may be infected, and wash or peel fresh fruits and vegetables before eating.

Infectious agent:

Cryptosporidium parvum is a coccidian protozoon.

Identification:

Clinical features :

Cryptosporidiosis is a parasitic infection that commonly presents as gastroenteritis. Enteric symptoms usually include watery diarrhoea associated with cramping abdominal pain, bloating, vomiting and fever. The disease is usually mild and self-limiting. In persons with impaired immunity, particularly those with AIDS, it may be prolonged and lifethreatening. Cryptosporidiosis infection may less commonly involve the lungs (bronchitis or pneumonia), gall bladder (cholecystitis) or pancreas (pancreatitis).

Symptoms usually last four to twenty-one days.

Method of diagnosis:

As tests for Cryptosporidium are not routinely conducted in some facilities laboratories should be informed if cryptosporidiosis is suspected. Oocysts may be identified by microscopy of faecal smears treated with a modified acid-fast stain. A monoclonal antibody test is useful for detecting oocysts in faecal and environmental samples. Oocyst excretion is most intense during the first days of illness. Oocysts are

rarely recovered from solid faeces. ELISA assays have been developed for the detection of antibodies but these are not in routine use.

Incubation period:

The incubation period is estimated to be one to twelve days, with an average of seven days.

Public health significance and occurrence:

Cryptosporidiosis occurs worldwide. Young children, the families of infected persons, men who have sex with men, travelers, health care workers and people in close contact with farm animals comprise most reported cases. Substantial outbreaks linked to public water supplies have been reported in the United States. Multiple outbreaks associated with public swimming pools and spas have been reported in Australia and worldwide. The risk of infection for Melbourne residents has been greater for people exposed to public swimming pools and household contacts of infected persons.

Reservoir:

Reservoirs include humans, cattle and other domestic animals.

Mode of transmission:

Transmission occurs by the faecal-oral route (person to person and animal to person), and via ingestion of contaminated foods and water.

Period of communicability:

Cases may be infectious for as long as oocysts are excreted in the stool. Asymptomatic excretion may persist for several weeks after symptoms resolve. Under suitable conditions oocysts may survive in soil and be infective for up to six months..

Susceptibility and resistance:

Everyone is susceptible to infection. People with normal immune systems usually have asymptomatic or self-limited gastrointestinal disease. People with impaired immunity may experience prolonged illness.

Control measures:

Preventive measures:

Encourage good personal hygiene, particularly following contact with animals or infected persons. Particular attention to hand washing is required during calving seasons on cattle properties. Filter or boil contaminated drinking water, as chemical disinfectants such as chlorine are not effective against oocysts

at the concentrations used in water treatment.

Control of case:

Treatment is symptomatic and particularly involves rehydration. Antibiotics are not indicated. Exclude symptomatic persons from food handling, direct care of hospitalised and institutionalised patients and care of children in child care centres until asymptomatic. Disinfect soiled articles.

As oocyst excretion may persist for extended periods it is not advisable for adults to swim in public pools for a period of seven days and children for a period of four weeks after their diarrhea has ceased. Showering before swimming is recommended at all times.

Control of contacts:

The diagnosis should be considered in symptomatic contacts.

Control of environment:

Faecal contamination of pools requires prompt action by the pool operator including disinfection, but oocysts resist standard chlorination. Refer to the Department of Human Services’ Pool operators’ handbook.

Outbreak measures:

An outbreak investigation is required if two or more cases are clustered in a geographic area or institution. Investigate potential common sources such as contact with farm animals, consumption

of contaminated water or unpasteurized milk or exposure to a common recreational swimming area.

The Department of Human Services considers cases may be linked to a public swimming facility if two or more people with Cryptosporidium infection (confirmed by a pathology laboratory) have used the same pool within two weeks of their illness. In this situation pool owners may need to close the affected swimming pool until it has been treated and superchlorinated with at least 14 mg/L free chlorine for at least 12 hours. It is important to ensure that the total chlorine level in a treated pool is less than 8 mg/L before re-opening it to the public. If an outbreak is particularly large, the Department may request additional steps to be undertaken.

sources of information

• Victorian Department of Human Services 2000, Pool operators’ handbook, http://www.health.vic. gov.au/environment

·         The blue book: Guidelines for the control of infectious diseases

·         http://www.nlm.nih.gov