Cryptic bat rabies
|Cryptic bat rabies|
|Bats outside Frio Cave in Texas. The cave is estimated to house over 20 million Mexican Free-tailed bats and their young.|
|Group:||Group V ((-)ssRNA)|
Cryptic bat rabies refers to infection from unrecognized exposure to rabies virus that can be phylogenetically traced to bats. It is most often seen in the southern United States. Silver-haired bats (Lasionycteris noctivagans) and Eastern pipistrelles (Pipistrellus subflavus) are the two most common bat species associated with this form of infection, though both species are known to have less contact with humans than other bat species such as the Big brown bat. That species is common throughout the United States and often roosts in buildings and homes where human contact is more likely. 
Non-bite transmission of rabies virus is believed to be through aerosolized inhalation of bat saliva, urine, and/or feces. Droplets containing the virus can pass through mucous membranes in the eyes, nose, mouth, or intestine. Experiments in the early 1960s by Dr. Denny Constantine, a veterinarian, in Texas demonstrated transmission of the virus to animals such as caged coyotes and foxes who had been placed inside Frio Cave with bats. Some of the animals cages were designed to exclude the bats while others were permeable to them. All the test animals became infected with the rabies virus. The conditions in the cave were severe with high temperatures and an ammonia haze rising from the bat guano.  In 1967, rabies virus was isolated from the air in Frio Cave. 
Species specific reservoir
It is not well understood why most, but not all, cases of cryptic bat rabies can be traced to Silver-haired bats and Eastern pipistrelles, but it is believed that the strain of rabies virus in these species is particularly virulent. 
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