The risk of acquiring North Asian tick typhus (infection by the bacterium Rickettsia sibirica from tick bites) is unknown during travel to regions of Asia where this disease is endemic.
North Asian tick typhus is similar to Rocky Mountain spotted fever (endemic to the US) caused by Rickettsia rickettsia. In a prospective study, Matthew R. Lewin from the University of California San Francisco, USA, and colleagues analysed the health diaries and blood samples of 13 paleontologists from the American Museum of Natural History (New York City) who had been on expeditions to Mongolia.
Four paleontologists suffered an acute illness which included fever, rash, and headache; analysis of their blood revealed the presence of antibodies to R sibirica. Those paleontologists with no illness and paleontologists who went on expeditions in other parts of the world (the control group) did not have antibodies to R sibirica. Of the four paleontologists who had tick typhus, only two were aware that they had been bitten by ticks.
Matthew R. Lewin comments: "Business, international relief, ecotourism, and adventure attract increasing numbers of travellers to Mongolia, China, and other north Asian republics every year. Travellers and their physicians should suspect this arthropod-borne illness in patients who return from endemic regions with a characteristic syndrome, even in the absence of a recognised tick bite."
Contact: Dr. Matthew R Lewin, Division of Emergency Medicine, Box 0208, University of California, San Francisco 94143-0208 USA; T): 415-353-1634; F): 415-927-7250; E): aplysia99@yahoo.com.
Journal
The Lancet