Bat Rabies Research Articles

The occurrence of rabies in pre-Columbian Central America: an historical search

Rabies is considered one of the oldest infectious diseases known to humans. However, the first written reports on rabies cases in the Americas did not appear until the first decade of the 18th century from Mexico. In an attempt to clarify if the disease was already present in pre-Columbian times, we searched for evidence in the Maya and Aztec cultures. Other sources of information were early manuscripts written by the conquistadors and early explorers. We did not identify any unequivocal direct evidence that the disease rabies was known in pre-Columbian Central America but sufficient circumstantial evidence is available suggesting that (bat) rabies was already present in these early times.

Rabies Postexposure Prophylaxis in a UK Travel Clinic: Ten Years' Experience

In 2009, 58.6 million UK residents traveled abroad. Of these, 49.5 million (84.5%) visits were to Europe and North America and 9.1 million (15.5%) were to other parts of the world. Rabies is widely distributed and continues to be a major public health issue in many developing countries. The UK is free of rabies in carnivore host species, although cases of rabies in bats have been reported. This study examined the rabies postexposure prophylaxis (PEP) service from 2000 to July 2009 at the Liverpool School of Tropical Medicine. Medical records of patients who attended the clinic for rabies PEP were reviewed. During the study period, 139 patients were treated for possible rabies exposure. The mean age was 35 years. Thailand and Turkey each accounted for 31 (22.3%) cases. Sixty-nine (49.6%) of those seen were due to dog bites. Most injuries involved a lower limb (n = 67, 48.2%) or hands (n = 26, 18.7%). Eighty-six (61.9%) cases had initiated rabies PEP overseas, but only 3 of the 78 (3.8%) meeting UK criteria for rabies immunoglobulin (RIG) received it while overseas. Only an additional 11 patients received RIG on return to the UK; most were seen more than 7 days after initiation of PEP. The median time from exposure to receiving rabies PEP was 1 day (range: 0-1,720). Only 14 (10.1%) had received preexposure rabies vaccination. The majority of travelers seeking PEP at this clinic initiated treatment overseas. Most had not received RIG abroad, when it would have been appropriate. Initiation of appropriate treatment is often delayed and is a concern to those without preexposure rabies immunization. In view of the scarcity of RIG, travelers need to be aware of the risks, consider preexposure immunization, and present early for PEP.

Rabies-related knowledge and practices among persons at risk of bat exposures in Thailand.

BackgroundRabies is a fatal encephalitis caused by lyssaviruses. Evidence of lyssavirus circulation has recently emerged in Southeast Asian bats. A cross-sectional study was conducted in Thailand to assess rabies-related knowledge and practices among persons regularly exposed to bats and bat habitats. The objectives were to identify deficiencies in rabies awareness, describe the occurrence of bat exposures, and explore factors associated with transdermal bat exposures.MethodsA survey was administered to a convenience sample of adult guano miners, bat hunters, game wardens, and residents/personnel at Buddhist temples where mass bat roosting occurs. The questionnaire elicited information on demographics, experience with bat exposures, and rabies knowledge. Participants were also asked to describe actions they would take in response to a bat bite as well as actions for a bite from a potentially rabid animal. Bivariate analysis was used to compare responses between groups and multivariable logistic regression was used to explore factors independently associated with being bitten or scratched by a bat.FindingsOf 106 people interviewed, 11 (10%) identified bats as a potential source of rabies. A history of a bat bite or scratch was reported by 29 (27%), and 38 (36%) stated either that they would do nothing or that they did not know what they would do in response to a bat bite. Guano miners were less likely than other groups to indicate animal bites as a mechanism of rabies transmission (68% vs. 90%, p = 0.03) and were less likely to say they would respond appropriately to a bat bite or scratch (61% vs. 27%, p = 0.003). Guano mining, bat hunting, and being in a bat cave or roost area more than 5 times a year were associated with history of a bat bite or scratch.ConclusionsThese findings indicate the need for educational outreach to raise awareness of bat rabies, promote exposure prevention, and ensure appropriate health-seeking behaviors for bat-inflicted wounds, particularly among at-risk groups in Thailand.

Host and viral ecology determine bat rabies seasonality and maintenance

Rabies is an acute viral infection that is typically fatal. Most rabies modeling has focused on disease dynamics and control within terrestrial mammals (e.g., raccoons and foxes). As such, rabies in bats has been largely neglected until recently. Because bats have been implicated as natural reservoirs for several emerging zoonotic viruses, including SARS-like corona viruses, henipaviruses, and lyssaviruses, understanding how pathogens are maintained within a population becomes vital. Unfortunately, little is known about maintenance mechanisms for any pathogen in bat populations. We present a mathematical model parameterized with unique data from an extensive study of rabies in a Colorado population of big brown bats (Eptesicus fuscus) to elucidate general maintenance mechanisms. We propose that life history patterns of many species of temperate-zone bats, coupled with sufficiently long incubation periods, allows for rabies virus maintenance. Seasonal variability in bat mortality rates, specifically low mortality during hibernation, allows long-term bat population viability. Within viable bat populations, sufficiently long incubation periods allow enough infected individuals to enter hibernation and survive until the following year, and hence avoid an epizootic fadeout of rabies virus. We hypothesize that the slowing effects of hibernation on metabolic and viral activity maintains infected individuals and their pathogens until susceptibles from the annual birth pulse become infected and continue the cycle. This research provides a context to explore similar host ecology and viral dynamics that may explain seasonal patterns and maintenance of other bat-borne diseases.

Infectious Diseases Associated with Caves

In recent times, caving has become increasingly popular, with almost 2 million people visiting national park caves each year in the United States. Although the 2 million tourist visits are extremely low risk, smaller numbers of sport cavers are at risk for some high risk conditions, and expedition cavers are at risk for some obscure infections. Infectious diseases like histoplasmosis, rabies, leptospirosis, and tick-borne relapsing fever may be transmitted by the underground fauna. To reduce the risk of illness or injury while caving, knowledge of potential risks before engaging in this activity is important. Caving preparation needs to be carefully planned and executed, including vaccinations, prophylactic medications, and advice regarding safe conduct and behaviors.

Active surveillance of bat rabies in France: A 5-year study (2004–2009)

Active surveillance of bats in France started in 2004 with an analysis of 18 of the 45 bat species reported in Europe. Rabies antibodies were detected in six indigenous species, mainly in Eptesicus serotinus and Myotis myotis, suggesting previous contact with the EBLV-1 rabies virus. Nineteen of the 177 tested bats were shown serologically positive in seven sites, particularly in central and south-western France. Neither infectious viral particles nor viral genomes were detected in 173 and 308 tested oral swabs, respectively. The presence of neutralising antibodies in female bats (18.6%) was significantly higher than in males (5.6%).

Laboratory Surveillance of Rabies in Humans, Domestic Animals, and Bats in Madagascar from 2005 to 2010

Background. Rabies virus (RABV) has circulated in Madagascar at least since the 19th century. Objectives. To assess the circulation of lyssavirus in the island from 2005 to 2010. Materials and Methods. Animal (including bats) and human samples were tested for RABV and other lyssavirus using antigen, ribonucleic acid (RNA), and antibodies detection and virus isolation. Results. Half of the 437 domestic or tame wild terrestrial mammal brains tested were found RABV antigen positive, including 54% of the 341 dogs tested. This percentage ranged from 26% to 75% across the period. Nine of the 10 suspected human cases tested were laboratory confirmed. RABV circulation was confirmed in 34 of the 38 districts sampled. No lyssavirus RNA was detected in 1983 bats specimens. Nevertheless, antibodies against Lagos bat virus were detected in the sera of 12 among 50 Eidolon dupreanum specimens sampled. Conclusion. More than a century after the introduction of the vaccine, rabies still remains endemic in Madagascar.

An overview of rabies - history, epidemiology, control and possible elimination.

Rabies remains the most important zoonotic disease in many countries. Public concern and fears are most focused on dogs as the source of rabies infection to humans and other domestic animals. Several bat species are reservoir hosts of rabies and therefore can be a public health hazard. The possibility of a carrier state or asymptomatic form of rabies deserves serious evaluation. Rabies in most countries was successfully controlled through mass vaccination of dogs, long before the recognition of bat and other wildlife rabies and the availability of modern vaccines. Though, the epidemiology, virology, transmission, pathology, clinical manifestations, diagnosis, treatment and control of rabies infection have been described extensively, the incidence is increasingly on the high side. However, experts have recognized for decades that rabies is wholly eradicable from all species except bats through targeted mass immunization, and the chief obstacle to eradicating rabies especially in bats is that no one has developed an aerosolized vaccine that could be sprayed into otherwise inaccessible caves and tree trunks. Inventing such a vaccine is considered difficult but possible. Forestalling this problem will require active epidemiological surveillance of wild and domestic animals with a wide range of modern molecular and ancillary epidemiological tools. This also demands government and private sector intervention, funding and collaboration of professionals in human and veterinary medicine with those in the environmental sciences. Recently, the heroic recovery of an unvaccinated teenager from clinical rabies offers hope of future specific therapy. While post-exposure vaccination is essential and should be continued with improvement to achieve consistently positive results, progress toward eliminating rabies has been markedly faster in nations that have emphasized preventive vaccination of animals. Key words: Control, epidemiology, history, mass vaccination, surveillance, zoonotic disease.

Bat Rabies and Other Lyssavirus Infections

Bat Rabies and Other Lyssavirus Infections

Pathogenicity of different rabies virus isolates and protection test in vaccinated mice

This study was aimed to evaluate and compare the pathogenicity of rabies virus isolated from bats and dogs, and to verify the efficacy of a commercial rabies vaccine against these isolates. For evaluation of pathogenicity, mice were inoculated by the intramuscular route (IM) with 500MICLD₅₀/0.03 mL of the viruses. The cross-protection test was performed by vaccinating groups of mice by the subcutaneous route and challenged through the intracerebral (IC) route. Isolates were fully pathogenic when inoculated by the IC route. When inoculated intramuscularly, the pathogenicity observed showed different death rates: 60.0% for the Desmodus rotundus isolate; 50.0% for dog and Nyctinomops laticaudatus isolates; 40.0% for Artibeus lituratus isolate; 9.5% Molossus molossus isolate; and 5.2% for the Eptesicus furinalis isolate. Mice receiving two doses of the vaccine and challenged by the IC route with the isolates were fully protected. Mice receiving only one dose of vaccine were partially protected against the dog isolate. The isolates from bats were pathogenic by the IC route in mice. However, when inoculated through the intramuscular route, the same isolates were found with different degrees of pathogenicity. The results of this work suggest that a commercial vaccine protects mice from infection with bat rabies virus isolates, in addition to a canine rabies virus isolate.

Rabies surveillance in the United States during 2009

During 2009, 49 states and Puerto Rico reported 6,690 rabid animals and 4 human rabies cases to the CDC, representing a 2.2% decrease from the 6,841 rabid animals and 2 human cases reported in 2008. Approximately 92% of reported rabid animals were wildlife. Relative contributions by the major animal groups were as follows: 2,327 (34.8%) raccoons, 1,625 (24.3%) bats, 1,603 (24.0%) skunks, 504 (75%) foxes, 300 (4.5%) cats, 81 (1.2%) dogs, and 74 (1.1%) cattle. Compared with 2008, numbers of rabid raccoons and bats that were reported decreased, whereas numbers of rabid skunks, foxes, cats, cattle, dogs, and horses that were reported increased. Fewer rabid raccoons, compared with 2008, were reported by 12 of the 20 eastern states where raccoon rabies is enzootic, and number of rabid raccoons decreased by 2.6% overall nationally. Despite a 10% decrease in the number of rabid bats that were reported and a decrease in the total number of bats submitted for testing, bats were the second most commonly submitted animal, behind cats, during 2009. The number of rabid skunks that were reported increased by 0.9% overall. The proportion of rabid skunks in which infection was attributed to the raccoon rabies virus variant decreased from 473% in 2008 to 40.9% in 2009, resulting in a 12.7% increase in the number of rabid skunks infected with a skunk rabies virus variant. The number of rabid foxes increased 11.0% overall from the previous year. Four cases of rabies involving humans were reported from Texas, Indiana, Virginia, and Michigan. The Texas case represented the first presumptive abortive human rabies case, with the patient recovering after the onset of symptoms without intensive care. The Indiana and Michigan cases were associated with bat rabies virus variants. The human rabies case in Virginia was associated with a canine rabies virus variant acquired during the patient's travel to India.

Bat Rabies in Massachusetts, USA, 1985–2009

To investigate rabies in Massachusetts, we analyzed bat rabies test results before and after introduction of raccoon variant rabies and after release of revised 1999 US Advisory Committee on Immunization Practices recommendations for rabies postexposure prophylaxis. Bat submissions were associated with level of rabies awareness and specific postexposure recommendations.

Rabies in Latin America

Objective: To review and discuss the available literature for rabies control in Latin America.Methods: A literature search was conducted in PubMed through October 2008. Articles in English, Spanish and Portuguese were reviewed.Results: Recent reports indicate that the region is close to achieve the goal of eliminating human rabies transmitted by dogs even though there are some isolated cases reported. However, insectivorous and vampire bats continue to expose humans and animals. These cases have been reported with increasing frequency.Discussion: Many challenges to the successful eradication of canine and non-canine rabies have been identified: among these are issues related to vaccine supply, the increase in transmission of canine rabies in certain areas, the presence of bat rabies in geographically inaccessible areas and lack of active action at local level. New strategies for systems information, networking and education are needed. Effective decentralization, adequate reallocation of resources, constant active surveillance, active local community participation and aggressive health education, might be some of the strategies that could prove to be helpful. More investment (funding and resources) and a very strong political commitment are needed to be able to eradicate this deadly disease.

First encounter of European bat lyssavirus type 2 (EBLV-2) in a bat in Finland

In Finland, rabies in bats was suspected for the first time in 1985 when a bat researcher, who had multiple bat bites, died in Helsinki. The virus isolated from the researcher proved to be antigenically related to rabies viruses previously detected in German bats. Later, the virus was typed as EBLV-2b. Despite an epidemiological study in bats 1986 and subsequent rabies surveillance, rabies in bats was not detected in Finland until the first case in a Daubenton's bat (Myotis daubentonii) was confirmed in August 2009. The bat was paralysed, occasionally crying, and biting when approached; it subsequently tested positive for rabies. The virus was genetically typed as EBLV-2. This is the northernmost case of bat rabies ever detected in Europe. Phylogenetic analyses showed that the EBLV-2b isolate from the human case in 1985 and the isolate from the bat in 2009 were genetically closely related, demonstrating that EBLV-2 may have been circulating in Finland for many years.

“Early death” and the contraindication of vaccine during treatment of rabies

Administration of rabies vaccine or rabies immune globulin (RIG) during symptomatic rabies is ineffective, and there are concerns about the phenomenon of “early death” reported in animals that develop rabies after receipt of rabies vaccine or immune globulin. Survival analyses of the original animal data confirm these findings in two species, whereas analyses of human case reports and the Milwaukee Protocol registry suggest lower risk of “early death” in humans. There may be a deleterious interaction of rabies vaccine and RIG with bat rabies in humans. Animal studies of bat rabies virus with bat-origin vaccines and RIG are urgently needed.

Experimental infection of serotine bats (Eptesicus serotinus) with European bat lyssavirus type 1a

The serotine bat (Eptesicus serotinus) accounts for the vast majority of bat rabies cases in Europe and is considered the main reservoir for European bat lyssavirus type 1 (EBLV-1, genotype 5). However, so far the disease has not been investigated in its native host under experimental conditions. To assess viral virulence, dissemination and probable means of transmission, captive bats were infected experimentally with an EBLV-1a virus isolated from a naturally infected conspecific from Germany. Twenty-nine wild caught bats were divided into five groups and inoculated by intracranial (i.c.), intramuscular (i.m.) or subcutaneous (s.c.) injection or by intranasal (i.n.) inoculation to mimic the various potential routes of infection. One group of bats was maintained as uninfected controls. Mortality was highest in the i.c.-infected animals, followed by the s.c. and i.m. groups. Incubation periods varied from 7 to 26 days depending on the route of infection. Rabies did not develop in the i.n. group or in the negative-control group. None of the infected bats seroconverted. Viral antigen was detected in more than 50% of the taste buds of an i.c.-infected animal. Shedding of viable virus was measured by virus isolation in cell culture for one bat from the s.c. group at 13 and 14 days post-inoculation, i.e. 7 days before death. In conclusion, it is postulated that s.c. inoculation, in nature caused by bites, may be an efficient way of transmitting EBLV-1 among free-living serotine bats.

Bats in the Bedroom, Bats in the Belfry: Reanalysis of the Rationale for Rabies Postexposure Prophylaxis

We assessed the scientific basis and practical implications of recommendations made since the late 1990s to offer rabies postexposure prophylaxis (RPEP) for occult bat encounters, including recommendations to offer RPEP to persons with bedroom exposure to a bat while sleeping without evidence of direct physical contact. The number needed to treat after bedroom exposure to a bat was calculated as the percentage of population exposed multiplied by the inverse of crude rabies incidence. Bedroom exposure was estimated in a population survey of 14,453 households. Incidence was based on reported human cases in Canada and the United States, 1990-2007. In the population surveyed, bedroom bat exposure while sleeping and without known physical contact occurred at an annual rate of 0.099%. We estimate that <5% of eligible persons with bedroom exposure receive RPEP as recommended. The incidence of human rabies due to bedroom bat exposure without recognized contact was 1 case per 2.7 billion person-years. The number needed to treat to prevent a single case of human rabies in that context ranges from 314,000 to 2.7 million persons. A total of 293-2500 health care professionals working full-time for a full year would be required to prevent a single human case of bat rabies due to bedroom exposure without recognized contact. Amounts of Can $228 million to Can $2.0 billion are additionally required for associated material costs. Human rabies acquired through bedroom exposure to a bat while sleeping and without recognized contact is rare. Conversely, such exposures are not uncommon in the population, and the resources required for associated RPEP are orders of magnitude higher than those required for most interventions that are considered to be reasonable. Current RPEP recommendations related to occult bat contact should be reconsidered.

Effects of immune system diversity and physical variation ofimmunotypic mixing on the dynamics of rabies in bats

The ecology and life history of rabies viruses in bats suggest a need for an integrated modelling treatment that extends beyond traditional epidemiological approaches. We modify our adaptive modelling approach to investigate the effects of immune system structure and immunological mixing events on the disease profile of the bat colony and subsequently on the dynamics of rabies viruses in bats. Our theoretical framework, which is based on individual (intra-host) models of the response of the host to a viral challenge and virus-specific disease mechanisms, integrates the individual components to provide information about the disease structure and the demographic composition of the bat colony. We focus on the changes in dynamics at the population level due to two processes: (1) immunological diversity in a biological process, reproduction, and (2) immunological diversity in a physical-physiological process, migration. The results suggest that immunotypic mixing plays a critical role in the disease progression within populations and it is an important factor in determining the persistence of rabies in exposed bat colonies.

Mitochondrial DNA signatures at different spatial scales: from the effects of the Straits of Gibraltar to population structure in the meridional serotine bat (Eptesicus isabellinus)

The meridional serotine bat Eptesicus isabellinus is found in North Africa and the Iberian Peninsula. We analyzed the genetic structure of E. isabellinus at two different geographic scales to reveal the historical and ecological patterns that have shaped its populations. The role of the Straits of Gibraltar as an isolating barrier between African and Iberian populations is evaluated and the degree of genetic structure and female-mediated gene flow was assessed at a local scale between neighboring colonies. Populations of E. isabellinus from Iberia and northern Morocco show little genetic divergence and share mtDNA haplotypes, indicating that the Straits of Gibraltar are neither an impediment to dispersal nor a cause of genetic differentiation. Our results also suggest that E. isabellinus may have dispersed from western Andalusia into northern Morocco after the last glacial period. At a smaller geographic scale, the colonies studied showed high variation in genetic variability and structure, indicating that no female-mediated gene flow is present. This pattern is consistent with a described pattern of independent endemic viral circulation of the bat rabies virus EBLV-1, which was found when studying rabies dynamics in the same serotine bat colonies.

ANIMAL RABIES IN MASSACHUSETTS, 1985–2006

In this study, we review annual rabies data from Massachusetts from 1985 to 2006, spanning the introduction of raccoon strain rabies in 1992. Of 52,034 animals tested, 9.7% (5,049/52,034) were rabid, representing 26 of over 67 species submitted. Bats were the most common rabid animals prior to 1992 (50 of 52), but raccoons (Procyon lotor) became the most common rabies-positive species upon arrival of raccoon strain rabies virus (38.2%, 2,728 of 7,138 tested), followed by striped skunks (Mephitis mephitis, 34.4%, 1,489 of 4,332), bats (5.3%, 427 of 8,053), foxes (red fox, Vulpes vulpes, and gray fox, Urocyon cinereoargenteus, 16.3%, 135 of 827), cats (0.8%, 136 of 18,050), and woodchucks (Marmota monax, 5.7%, 82 of 1,446). Cats were the most frequently tested animal (34.7%). Raccoon strain rabies spread from two foci of introduction with an initial epizootic phase of 4 yr, by which time most of the state was affected. In 1992, there was a transition from enzootic bat rabies, with little spillover to other animals, to terrestrial rabies associated with raccoon strain virus. Although raccoons were most affected by the raccoon strain virus, there was spillover to other species, particularly to skunks. The eastern United States raccoon rabies epizootic led to a marked increase in submissions for rabies testing and the number of positive animals detected; however, bat rabies cases remained at their previous levels. Wild animal rabies presents a significant threat to humans and domestic/companion animals and increased costs related to increased demand for rabies testing, postexposure prophylaxis as well as euthanasia of valuable domestic animals.