Cryptic rabies refers to infection from unrecognized exposure to

rabies virus Rabies virus (''Lyssavirus rabies'') is a neurotropic virus that causes rabies in animals, including humans. It can cause violence, hydrophobia, and fever. Rabies transmission can also occur through the saliva of animals and less commonly throu ...

. It is often

phylogenetically In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

traced to

bat Bats are flying mammals of the order Chiroptera (). With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their very long spread-out ...

s. It is most often seen in the

southern United States The Southern United States (sometimes Dixie, also referred to as the Southern States, the American South, the Southland, Dixieland, or simply the South) is List of regions of the United States, census regions defined by the United States Cens ...

Silver-haired bat The silver-haired bat (''Lasionycteris noctivagans'') is a solitary migratory species of vesper bat in the family Vespertilionidae and the monotypic, only member of the genus ''Lasionycteris''. Etymology The species name translates as night-wand ...

s (''Lasionycteris noctivagans'') and tricolored bats (''Perimyotis 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 The big brown bat (''Eptesicus fuscus'') is a species of vesper bat distributed widely throughout North America, the Caribbean, and the northern portion of South America. It was first described as a species in 1796. Compared to other microbats ...

. That species is common throughout the United States and often roosts in buildings and homes where human contact is more likely.

Transmission

Cryptic rabies refers to instances where rabies occurs in an individual with no clear history of exposure to a rabies vector. Determining history of contact, usually via the bite of an infected animal, can be difficult if the patient is unconscious or incoherent by the time an attempt is made to collect patient history. Thus, friends and family are needed to fill in patient history of possible bite exposure. Additionally, bites from a vector can be overlooked, particularly for some small bat species. Bites from a bat can be so small that they are not visible without magnification equipment, for example. Outside of bites, rabies virus exposure can also occur if infected fluids come in contact with a mucous membrane or a break in the skin. Rabies virus has also been transmitted when an infected human unknowingly dies of rabies, and their organs are transplanted to others. While it has been speculated that rabies virus could be transmitted through aerosols, studies of the rabies virus have concluded that this is only feasible in limited conditions. These conditions include a very large colony of bats in a hot and humid cave with poor ventilation. While two human deaths in 1956 and 1959 had been tentatively attributed to aerosolization of the rabies virus after entering a cave with bats, "investigations of the 2 reported human cases revealed that both infections could be explained by means other than aerosol transmission".

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 tricolored bats, but it is believed that the strain of rabies virus in these species is particularly

virulent Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most cases, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host. The pathogenicity of an organism—its abilit ...

References

External links

* {{DEFAULTSORT:Rabies Virus

virus A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...

Lyssaviruses