Studies of Arthropod-Borne Virus Infections in Chiroptera

Summary The present report concerns the susceptibility of three species of insectivorous bats (Tadarida brasiliensis mexicana, Myotis lucifugus lucifugus, Eptesicus fuscus fuscus) to experimental infection with several strains of Japanese B encephalitis (JBE) and St. Louis encephalitis viruses. All three bat species proved to be susceptible to subcutaneous inoculation with one or more virus strains, the intensity of the infection depending on the mouse-passage level and origin of the strain. In general, high mouse-passage strains were less infective for bats than recent isolates. The characteristics of experimental arbovirus infection in bats include a persistent viremia (15–30 days) and viral invasion and multiplication in interscapular brown adipose tissue and, to a lesser degree, in brain and kidney tissue. Intracerebral inoculation of JBE virus produced a more intense and widespread infection in the big brown bat (Eptesicus f. fuscus) than subcutaneous inoculation, yet evidence of viral pathology was not observed in sections of infected brain or brown fat. None of the infected bats showed evidence of disease, indicating that these viruses are capable of replicating in various tissues of the bat without noticeably damaging cells or producing overt signs of encephalitis. Reasons why bats might be effective reservoirs of arboviruses in various phases of the year-round transmission cycles are discussed and the application of these experimental studies in the planning of field work is indicated.