Rodents as Sentinels for the Prevalence of Tick-Borne Encephalitis Virus

Abstract

Introduction: Tick-borne encephalitis virus (TBEV) causes one of the most important flavivirus infections of the central nervous system, affecting humans in Europe and Asia. It is mainly transmitted by the bite of an infected tick and circulates among them and their vertebrate hosts. Until now, TBE risk analysis in Germany has been based on the incidence of human cases. Because of an increasing vaccination rate, this approach might be misleading, especially in regions of low virus circulation. Method: To test the suitability of rodents as a surrogate marker for virus spread, laboratory-bred Microtus arvalis voles were experimentally infected with TBEV and analyzed over a period of 100 days by real-time (RT)-quantitative polymerase chain reaction. Further, the prevalence of TBEV in rodents trapped in Brandenburg, a rural federal state in northeastern Germany with autochthonous TBE cases, was determined and compared with that in rodents from German TBE risk areas as well as TBE nonrisk areas. Results: In experimentally infected M. arvalis voles, TBEV was detectable in different organs for at least 3 months and in blood for 1 month. Ten percent of all rodents investigated were positive for TBEV. However, in TBE risk areas, the infection rate was higher compared with that of areas with only single human cases or of nonrisk areas. TBEV was detected in six rodent species: Apodemus agrarius, Apodemus flavicollis, Apodemus sylvaticus, Microtus agrestis, Microtus arvalis, and Myodes glareolus. M. glareolus showed a high infection rate in all areas investigated. Discussion and Conclusion: The infection experiments proved that TBEV can be reliably detected in infected M. arvalis voles. These voles developed a persistent TBE infection without clinical symptoms. Further, the study showed that rodents, especially M. glareolus, are promising sentinels particularly in areas of low TBEV circulation.

Correlation of TBE Incidence with Red Deer and Roe Deer Abundance in Slovenia

“…As non-viremic host, they are essential for transmission of TBEV by co-feeding of infected and non-infected ticks [20], [21], [22], [23]. Additionally, viremia in small mammals is sufficiently high and most likely not as short termed as previously thought to enable direct transmission of the virus to feeding ticks [24], [25], [26], [27]. Deer on the other hand are not competent hosts for TBEV transmission, but they are important in the enzootic cycle of TBEV since they support tick populations [3], [28], [29], [30], [31].…”

Chronic Infectious Inflammatory Diseases of the Central Nervous System

“…A poor outcome is associated with older age, severity of disease, impaired consciousness, seizures, hydrocephalus, HIV co-infection and delayed antituberculosis therapy (Achazi et al 2011 ;Hsu et al 2010 ;Cecchini et al 2009 ). Drug-resistant tuberculosis is associated with more severe manifestations and higher mortality (Garg et al 2013 ).…”

Epidemiological and Ecological Studies of Tick-borne Encephalitis Virus

“…TBEV infection can persist in rodents for several months and even throughout the years, but it is unclear how much this contributes to the transmission and overwintering of the virus [73][74][75][76].…”