Roadside ecology and epidemiology of tick-borne diseases

When humans, pets and livestock walk along roads, they may encounter questing ticks and tick-borne pathogens. A new field of environmental science called road ecology can help researchers study the complex epidemiology of tick-borne diseases in the unique roadside environment. This paper reviews some of the important ways that roads alter the distribution, abundance and behaviour of wildlife species that are involved in the enzootic cycles of tick-borne diseases. Compared to the surrounding landscape, roadways often constitute a different environment and hence there is no assurance that disease risk along roads will be the same as in the adjacent landscape, or that disease control measures taken in the surrounding landscape will work in the adjacent roadway. Since roadways have their own special ecological conditions, are used extensively by the human populace and play strategic roles in community security, we believe that roadways should be one of the habitats where tick-borne diseases are studied. It is amazing that at this late period of human history, epidemiological research along such important corridors has been almost completely ignored.     

Evidence of rickettsial spotted fever and ehrlichial infections in a subtropical territory of Jujuy, Argentina.

Between November 1993 and March 1994, a cluster 6 pediatric patients with acute febrile illnesses associated with rashes was identified in Jujuy Province, Argentina. Immunohistochemical staining of tissues confirmed spotted fever group rickettsial infection in a patient with fatal disease, and testing of serum of a patient convalescing from the illness by using an indirect immunofluorescence assay (IFA) demonstrated antibodies reactive with spotted fever group rickettsiae. A serosurvey was conducted among 16 households in proximity to the index case. Of 105 healthy subjects evaluated by IFA, 19 (18%) demonstrated antibodies reactive with rickettsiae or ehrlichiae: 4 had antibodies reactive with Rickettsia rickettsii, 15 with Ehrlichia chaffeensis, and 1 with R. typhi. Amblyomma cajennense, a known vector of R. rickettsii in South America, was collected from pets and horses in the area. These results are the first to document rickettsial spotted fever and ehrlichial infections in Argentina.     

Efficient use of a small genome to generate antigenic diversity in tick-borne ehrlichial pathogens

Ehrlichiae are responsible for important tick-transmitted diseases, including anaplasmosis, the most prevalent tick-borne infection of livestock worldwide, and the emerging human diseases monocytic and granulocytic ehrlichiosis. Antigenic variation of major surface proteins is a key feature of these pathogens that allows persistence in the mammalian host, a requisite for subsequent tick transmission. In Anaplasma marginale pseudogenes for two antigenically variable gene families, msp2 and msp3, appear in concert. These pseudogenes can be recombined into the functional expression site to generate new antigenic variants. Coordinated control of the recombination of these genes would allow these two gene families to act synergistically to evade the host immune response.     

New aspects of the epidemiology of tick-borne encephalitis

Profound studies of the mechanisms of virus transfer by bites and the behaviour of the infected ticks of male Ixodes ticks in the virus transfer and establish the effect of early and short-term suction of ticks in the onset of the disease. Preservation of saliva cement stopper in the skin of the infected vertebral host is of particular importance in the epidemiology and epizootiology of tick-borne encephalitis, as the cement cone in the skin may contain the quantity of the virus comparable with its concentration in the whole body of the tick. The experimental data suggest the predominant and more successful virus multiplication in the most viable and active ticks of the population as well as virus-induced stimulation of searching activity in the infected ticks. The attention is attracted to possible retention of the natural virus store by its elimination with the saliva of male ticks and virus exchange by sucking of the infected saliva from the affected focus on the skin by noninfected ticks fed together with infected insects, insensitive to tick-borne encephalitis virus.     

Ecology and epidemiology of tick-borne borreliosis in the Ul'ianovsk region

The parameters that characterize the affection and spread of ticks in the Ulyanovsk Region are presented. A risk for Ixodes tick-borne borreliosis among the urban population is shown.     

Scrub typhus and rickettsial diseases in international travelers: A review

Physicians caring for febrile returned travelers face the difficult task of recognizing the typical and atypical features of more than 16 known rickettsial diseases and separating these diseases from potentially serious nonrickettsial diseases. Currently available diagnostic tools are inadequate for timely diagnosis. This review summarizes the English-language literature concerning imported rickettsial diseases in international travelers and describes important clinical principles in diagnosis and treatment of these illnesses. Travelers with imported rickettsial disease often become sick before or within a few days of return from an endemic region. Illness that begins more than 18 days after return is unlikely to be rickettsial in origin. The absence of a skin rash or exposure to a vector should not dissuade clinicians from considering the possibility of a rickettsial disease in a returned traveler. Finally, if empiric therapy does not result in defervescence within 48 hours, an alternative nonrickettsial illness should be strongly considered.