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Laboratory Testing

In many cases it is important to identify the cause of the disease in travellers, not only to treat the individual but also to prevent transmission and to document the prevalence of the specific disease, both in returning travellers and in the countries they visited.

The specific tests that should be ordered depends entirely on the symptoms that the returned traveller exhibits. Testing for some of the more common travel related infections seen in Australians returning from abroad are discussed below. 

Causes of bacterial diarrhoea may be identified with a stool culture, or PCR test. Parasitic causes of diarrhoea can be identified through the microscopy of the faeces, to identify the mature parasite or their ova (eggs), or cyst (dormant) forms. Microscopy is performed on a fresh or specially preserved stool sample. For some parasites, such as Giardia intestinalis (lamblia), cryptosporidium and Entamoeba histolytica PCR tests have been developed, which are more rapid and have superior diagnostic performance characteristics compared with traditional microscopy. For some centres where microscopy or PCR are not readily available, antigen (proteins associated with the parasite) tests may be used. 

PCR tests are now routinely available for a range of common causes of viral diarrhoea. These tests are rapid and accurate, and can help to indentify the cause of an individuals symptoms which may be useful in a returned traveller where there are many potential causes. 

The most common travel related infection is a viral respiratory tract infection, such as influenza (the flu) or the common cold. Investigation of a returned traveller, with a fever, should in most cases include PCR testing of a nasopharyngeal swab (taken from the back of the nose/throat) for the more common respiratory viruses. 

Dengue fever is common in Indonesia (including Bali) and Thailand which are common travel destinations for Australian tourists. In individuals with a fever returning from Dengue endemic areas a sample of blood for antigen/PCR testing is performed to detect the presence of this condition. Later in the illness IgG and IgM antibodies may also be detected. Full blood count may also be performed to monitor the severity and progression of the illness utilising the haematocrit

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 travellers’ diseases can be identified either by culturing the microorganism, observing it under the microscope, and/or testing for antibodies or antigens. 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.  

Typhoid fever is a serious, systemic bacterial infection spread through the consumption of contaminated food or drink. In returned travellers with a fever a sample of blood for culture is indicated to attempt to identifiy this condition.

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.

Last Review Date: August 14, 2017