I work as a medical adviser to the Travel Medicine and Vaccination Centre, a private clinic that assesses travelers for destination-specific health risks and provides them with appropriate advice, including vaccines and antimalarial prescriptions. One of the commonest vaccines that travelers receive is for hepatitis A. It has come to our attention over the past year that several travelers who had received hepatitis A vaccine were later diagnosed as having had acute hepatitis A after they developed post-travel illness. This diagnosis appears to have been based on serological testing of antiHAV antibodies. Although this is possible, the likelihood of contracting acute hepatitis A following immunization is extremely low, as this vaccine is highly immunogenic with efficacy rates near 100% in healthy individuals.[1,2]
Unfortunately, lab tests for hepatitis may be confusing and the measurement of antiHAV antibodies may not distinguish between infection and vaccine-induced antibodies. An HAV IgG or “total” IgG/IgM result that reads as “reactive” may refer to the previous hepatitis A vaccination. Only direct measurement of HAV IgM antibody will generally distinguish acute cases of hepatitis A.
A provincial protocol for viral hepatitis testing was drawn up in 1998 and can be found at the following web site: www.healthservices.gov.bc.ca/msp/protoguides/gps/vihep.html.
Although this algorithm may be useful for more clear-cut cases of hepatitis with jaundice and elevated liver enzymes, it does not include a differential diagnosis for the numerous possible causes of hepatitis-like illness, and in particular does not address the additional aspect of travel-related illness.
As with other illnesses acquired during travel, it is important to obtain a careful history of destinations visited and all possible risk factors. Transient jaundice syndromes and/or elevated liver enzymes may be the result of several infections, including hepatitis A, cytomegalovirus, Epstein-Barr virus, or leptospirosis. Hepatitis E is also not uncommon in developing countries and, like hepatitis A, is transmitted through a fecal-oral route and has an incubation time of 2 to 9 weeks. Although it is relatively benign, there is a mortality rate of 1% to 2% overall and a high rate of mortality (20%) in pregnant women. Serology for Hepatitis E is not readily available and may require referral to a national laboratory.
Although hepatitis B has a longer incubation time than hepatitis A and E, it would be important to check hepatitis B surface antigen, particularly if the patient was not previously immunized and there were additional risk factors for blood-borne or sexually transmitted disease. In some individuals it may also be necessary to rule out other non-infectious causes of jaundice (drug-induced, neoplasia, obstruction, autoimmune, etc.).
Any patient who presents with fever following travel to a malarial country should also be immediately evaluated with thick and thin blood smears. These smears should be read “stat” by a laboratory technologist who is familiar with identifying plasmodium parasites. P. falciparum carries a high mortality rate and should be treated promptly by an infectious disease expert. Canada now has the Canadian Malaria Network that provides quick access to the medications (quinine) and expertise needed to treat acute malaria. (www.hc-sc.gc.ca/pphb-dgspsp/tmp).
It is our hope that all patients who develop travel-associated illness, including hepatitis syndromes, would be fully investigated using a wide differential diagnosis that includes knowledge of the countries visited. Consultation with tropical infectious disease experts and medical microbiologists may enable more accurate serological and other investigations.
—Caroline Penn, MD
Travel Medicine and Vaccination Centre
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