The influence of lowered body temperature and depressed metabolic rate of the cold-exposed bat on experimental arbovirus infection has been studied using three species of insectivorous bats, Tadarida b. mexicana, Myotis l. lucifugus, and Eptesicus f. fuscus. One strain of St. Louis encephalitis (SLE) virus and two strains of Japanese B encephalitis (JBE) virus were employed. Although the effects of low temperature on experimental arbovirus infection in bats varied with the bat species used and the relationship between inoculation of virus and the initiation of cold-exposure, the results obtained indicated that these animals would be ideal hosts for overwintering of arboviruses in nature. Generally, infection in bats was suppressed by low temperature but sustained by the animals for several months as evidenced by (1) the demonstration of low levels of virus in the blood and brown adipose tissue of the hibernating bat, and (2) the activation of viral multiplication upon transfer to 24°C producing more intense viremias and tissue involvement.
The course of JBE virus infection in bats maintained at 37°C was studied to determine if the increased body temperature and metabolic rate induced by the higher temperature would result in a more intense infection than occurs in bats held at 24°C. Results of experiments at 37°C showed that although viremia occurred more rapidly and reached higher levels, virus did not persist in the blood as long as in infected bats held at 24°C, there was no widespread dissemination of virus among the tissues, and the infection at 37°C produced no signs of encephalitis or damage to tissue.