CDC Reminds Americans Traveling Abroad of the Dangers of Rickettsiosis From Ticks, Fleas, and Chiggers

As many Americans prepare to travel internationally this summer, epidemiologists with the US Centers for Disease Control and Prevention (CDC) are reminding travelers and health care providers about the risk of vector-borne rickettsial diseases abroad.

Each year, international travelers from the United States are exposed to tickborne diseases such as African tick bite fever, Mediterranean spotted fever, scrub typhus, and others caused by obligate intracellular, gram-negative bacteria belonging to the order Rickettsiales. In an interview with Contagion^®, CDC veterinary epidemiologist Cara Cherry, DVM, MPH, DACVPM, explained that although most of the cases of rickettsial diseases that occurred in American travelers from 1996-2008 were acquired in sub-Saharan Africa, the full scope of rickettsiosis infections is not known. “Several publications have looked at travel-associated rickettsioses among certain populations, but no national data are available noting all travel-associated cases.”

Cherry recently co-presented a webinar on travel-associated rickettsiosis guidance through the CDC’s Clinician Outreach and Communication Activity (COCA) program, discussing the nearly worldwide distribution of vector-borne rickettsial diseases and their risk to travelers. The webinar covered information on the epidemiology, clinical presentation, diagnosis, and treatment of African tick bite fever, Mediterranean spotted fever, and scrub typhus, 3 of the most common travel-associated rickettsial diseases.

According to an analysis of 280 cases of rickettsial disease acquired by international travelers from 1996 to 2008, 87.6% of spotted fever rickettsiosis cases were acquired in sub-Saharan Africa. Among these rickettsial diseases, African tick bite fever is the most commonly acquired by international travelers and commonly occurs in clusters of cases among tour groups and families. It is caused by Rickettsia africae bacteria and also occurs in several Caribbean islands. Symptoms of African tick bite fever include fever, headache, rash, myalgia, and small lesions at the site of tick bites.

Mediterranean spotted fever is a more serious illness endemic to the Mediterranean basin region—including southern Europe and northern Africa—and is caused by Rickettsia conorii bacteria. The condition is marked by an abrupt onset of high fever, chills, and myalgia, and severe cases can result in neurological manifestations from meningoencephalitis, deep vein thrombosis, and can affect several organs. Related conditions include Israeli spotted fever found in Israel, Portugal, and Sicily, as well as Astrakhan spotted fever in areas of Russia, Chad, and Kosovo.

Scrub typhus is the second most prevalent rickettsial disease among those traveling abroad, and occurs in a geographical triangle extending from far eastern Russia to northern Australia to Afghanistan, though new cases have been found in countries such as Chile, Dubai, and Cameroon. Transmitted by chigger bites spreading Orientia tsutsugamushi bacteria, scrub typhus symptoms are typically mild but can have severe manifestations including acute respiratory distress, pneumonitis, meningoencephalitis, gastrointestinal bleeding, and acute renal failure.

For all travel-associated rickettsial diseases, doxycycline is the antibiotic treatment of choice, and Cherry emphasizes the importance of avoiding treatment delays. “If you get sick after returning from international travel go see your healthcare provider right away,” said Cherry. “Make sure to inform your healthcare provider about your recent travel, where you went, and what activities you participated in during your trip.”

To minimize the risk of acquiring rickettsioses while you travel this summer, Cherry recommends learning which diseases are common to your destinations through the CDC’s traveler’s health page. Minimize your risk of tick, flea, and chigger bites by avoiding areas with thick vegetation and high grass, walking in the center of trails when hiking, and using insect repellants containing DEET, picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol, or 2-undecanone during outdoor activities. Check your body for ticks after spending time outdoors and bathe or shower as soon as possible after coming indoors to wash off and more easily find crawling ticks before they bite you. Remove all attached ticks as soon as possible.