History and exam

Key diagnostic factors

common

presence of risk factors

Key risk factors include young age (3 years or younger), especially if attending day care; T-cell immune deficiency (advanced HIV infection, leukemia, lymphoma, primary T-cell immune deficiency) or immunosuppression; malnutrition; international travel (especially to non-industrialised countries); contact with farm animals; drinking contaminated water; swimming pool or recreational water exposure; contact with others with diarrhoea; and toileting/changing nappies of young children.

diarrhoea

Diarrhoea is found in virtually all cases and may continue for up to 3 weeks or sometimes longer; it may also have a relapsing and remitting nature. Stools tend to be watery and voluminous in nature. In immunocompromised patients the diarrhoea may be chronic and intractable.

Other diagnostic factors

common

abdominal pain

Found in most cases.[38][83]

vomiting

Found in about half to two-thirds of cases.[38][83]

loss of appetite

Found in about half to two-thirds of cases.[38][83]

low-grade fever

Found in one third to two-thirds of cases.[38][83]

loss of weight

In acute disease, diarrhoea can continue for up to 4 weeks, and significant weight loss can occur. In patients with T-cell immune deficiency, large-volume diarrhoea is often associated with profound weight loss.

uncommon

right upper quadrant abdominal pain

Cholangitis is a feature of pancreatobiliary disease, which is occasionally found in severely immunocompromised people.

jaundice

May signify sclerosing cholangitis, which can eventually lead to liver cirrhosis but occurs only in severely immunocompromised people.

nasal discharge and facial pain

Sinusitis has very rarely been described in severely immunocompromised patients.[64][65]

cough and dyspnoea

Tracheobronchial involvement has occurred rarely in immunocompromised patients.

Risk factors

strong

contact with farm animals, especially calves and lambs

C. parvum, but not C. hominis, is a zoonosis that can be acquired on farm visits, particularly where young ruminants are present.[38][67][68]

international travel

Travellers, especially to developing countries, are at risk, and particularly backpackers or hikers who may drink water from contaminated sources.[38][67][69]​​

age: 3 years or younger

Children aged 3 years or younger are particularly at risk, and outbreaks in day care nurseries have been described.[70]

immune deficiency: T-cell-mediated

Those with impaired T-cell immunity are at risk of severe disease with Cryptosporidium infection. T-cell immune deficiencies include advanced HIV infection, leukemia, lymphoma, and primary T-cell immune deficiency.

swimming and recreational water sports

As the oocysts resist chlorination, outbreaks have been associated with swimming pools and water parks, and infection can occur during water-based activities in other settings such as lakes and streams.[33][67]​​[71][72]

drinking unfiltered water

Contamination of community drinking-water supplies has the potential to cause large outbreaks of cryptosporidiosis, because Cryptosporidium is not killed by standard chlorination. The largest outbreak was in Milwaukee in 1994.[73] Because of the size of Cryptosporidium oocysts (3 to 6 micrometres), point-of-use filters used for control must be appropriate for this purpose (reverse osmosis or absolute 1 micrometre filters, for example).

toileting or changing nappies of young children

Contact with others with diarrhoea, and toileting or changing nappies of young children, pose a risk of transmission of cryptosporidiosis.

Malnutrition

Studies suggest an estimated prevalence of 10% to 20% of cryptosporidiosis in children with acute malnourishment.[3]

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