Tests

Laboratory Testing
It is important to identify the cause of the disease in travelers, not only to treat the individual but also to prevent transmission and to document the prevalence of the specific disease, both in returning travelers and in the countries they visited.

Causes of bacterial diarrhea may be identified with a stool culture and may be treated with antimicrobial agents when symptoms appear and/or may resolve without further tests to identify the pathogen. Parasitic causes of diarrhea can be identified through the O&P (ova and parasite) stool test. This test is used to identify parasites and their eggs in a fresh or specially preserved stool sample. For some parasites, such as Giardia intestinalis (lamblia), antigen tests have been developed. These tests identify proteins associated with the parasite and can be useful when parasites are present in low numbers. Because identifying the cause of viral diarrhea is complex, viral causes of diarrhea may not be identified by specific cultures or tests unless the virus causes a large number of people to become ill, such as may occur on a cruise ship or in a hotel.

The parasite that causes malaria (Plasmodium spp.) infects red blood cells. It can be identified by collecting a blood sample and examining specially stained “thick and thin” blood smears on slides under the microscope. Many of the other traveler’s diseases can be identified either by culturing the microorganism, observing it under the microscope, and/or testing for antibodies (the immune system’s response to the infection) or antigens (proteins from the microorganism). Patients who return from travel with an acute or chronic condition should consult with their doctor, who may suggest a consultation with an infectious disease and/or tropical medicine specialist.

Non-Laboratory Tests
Sometimes x-rays or CT scans may be used to evaluate body organs, such as the lungs or liver, for evidence of infection or damage.