Parasites are a source of significant illness worldwide. In the United States,
giardiasis,
cryptosporidiosis,
cyclosporiasis, and
trichinellosis are nationally notifiable conditions. Pinworm, the most common intestinal parasite in children, is not a locally notifiable
infection. Intestinal parasites have a wide range of acute and chronic symptoms but should be suspected in those who present with
diarrhea lasting more than seven days.
Infections most often occur through a fecal-oral route. Symptoms tend to be worse for children, older adults, or immunocompromised individuals. To diagnose
Giardia infection, stool microscopy with direct fluorescent antibody testing is recommended;
metronidazole,
nitazoxanide, or
tinidazole is used for treatment. Microscopy with immunofluorescence is sensitive and specific for diagnosing
Cryptosporidium infection. This
infection is often self-resolving, but treatment with
nitazoxanide is effective for symptoms lasting more than two weeks. Microscopy or polymerase chain reaction assays are recommended to diagnose
Cyclospora infections, and
sulfamethoxazole/
trimethoprim may be used to treat patients with persistent
diarrhea. Trichinella
infection is diagnosed by serum antibody testing, and severe symptoms are treated with
albendazole in patients older than one year.
Pinworm infections are diagnosed visually or by a tape test or paddle test;
albendazole and
pyrantel pamoate are both effective treatments.