Cryptic bat rabies

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Cryptic bat rabies
Free-tailed bats.jpg
Bats outside Frio Cave in Texas. The cave is estimated to house over 20 million Mexican Free-tailed bats and their young.
Virus classification
Group: Group V ((-)ssRNA)
Order: Mononegavirales
Family: Rhabdoviridae
Genus: Lyssavirus
Species: Rabies virus

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.[1][2]


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.[3] In 1967, rabies virus was isolated from the air in Frio Cave.[4][5]

Air-borne transmission of rabies virus between bats has been shown to be possible since rabies virus has been isolated from the nasal mucosa of bats who are naturally infected with the virus.[6][7]

Species specific reservoir[edit]

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.[8][9][10]

See also[edit]


  1. ^ Sharon L. Messenger, Jean S. Smith, Lillian A. Orciari, Pamela Yager, and Charles Rupprecht. Emerging Patterns of Rabies Deaths and Increased Viral Infectivity. Research. Volume 9, Number 2: February 2003.
  2. ^ Sharon L. Messenger, Jean S. Smith, Charles Rupprecht. Emerging Epidemiology of Bat-Associated Cryptic Cases of Rabies in Humans in the United States. Clin Infect Dis. (2002) 35 (6): 738-747.
  3. ^ Denny G. Constantine. Rabies transmission by nonbite route. Public Health Rep. 1962 April; 77(4): 287–289.
  4. ^ Winkler, W. G. 1968. “Airborne Rabies Virus Isolation.” Bull. Wildlife Disease Assoc. Vol. 4, April 1968, pp. 37-40. Available online at:
  5. ^ Messenger SL, Smith JS, Rupprecht CE (2002). "Emerging epidemiology of bat-associated cryptic cases of rabies in humans in the United States". Clin. Infect. Dis. 35 (6): 738–47. doi:10.1086/342387. PMID 12203172. 
  6. ^ Constantine, D. G., Emmons, R. W. & Woodie, J. D. (1972). Rabies virus in nasal mucosa of naturally infected bats. Science 175, 1255–1256.
  7. ^ Gibbons RV. Cryptogenic rabies, bats, and the question of aerosol transmission. Ann Emerg Med. 2002 May;39(5):528-36.
  8. ^ Warrell, M. J. & Warrell, D. A. (2004). Rabies and other lyssavirus diseases. Lancet 363, 959–969.
  9. ^ Winkler, W. G. (1968). Airborne rabies virus isolation. Wildl Dis 4, 37–40.Winkler, W. G., Baker, E. F., Jr & Hopkins, C. C. (1972).
  10. ^ An outbreak of non-bite transmitted rabies in a laboratory animal colony. Am J Epidemiol 95, 267–277.

External links[edit]