Serological Surveillance of Rabies in Free-Range and Captive Common Vampire Bats Desmodus rotundus.

The control of vampire bat rabies (VBR) in Brazil is based on the culling of Desmodus rotundus and the surveillance of outbreaks caused by D. rotundus in cattle and humans in addition to vaccination of susceptible livestock. The detection of anti-rabies antibodies in vampire bats indicates exposure to the rabies virus, and several studies have reported an increase of these antibodies following experimental infection. However, the dynamics of anti-rabies antibodies in natural populations of D. rotundus remains poorly understood. In this study, we took advantage of recent outbreaks of VBR among livestock in the Sao Paulo region of Brazil to test whether seroprevalence in D. rotundus reflects the incidence of rabies in nearby livestock populations. Sixty-four D. rotundus were captured during and after outbreaks from roost located in municipalities belonging to three regions with different incidences of rabies in herbivores. Sixteen seropositive bats were then kept in captivity for up to 120 days, and their antibodies and virus levels were quantified at different time points using the rapid fluorescent focus inhibition test (RFFIT). Antibody titers were associated with the occurrence of ongoing outbreak, with a higher proportion of bats showing titer >0.5 IU/ml in the region with a recent outbreak. However, low titers were still detected in bats from regions reporting the last outbreak of rabies at least 3 years prior to sampling. This study suggests that serological surveillance of rabies in vampire bats can be used as a tool to evaluate risk of outbreaks in at risk populations of cattle and human.

Rabies virus monitoring in bat populations in Rondônia state, Brazil.

INTRODUCTION: The Jirau hydroelectric power plant built in Rondônia state has environmental impacts that could be relevant to rabies outbreaks. METHODS: Bat populations were monitored for rabies by fluorescent antibody testing and simplified fluorescent inhibition microtesting between 2010 and 2015. RESULTS: All 1,183 bats tested negative for rabies. The prevalence of rabies antibodies was 17.5% in 1,049 bats. CONCLUSIONS: The rabies antibody dosage was not reactive in samples collected before the environmental changes, and there was a progressive increase in subsequent collections that could indicate an increase in rabies virus circulation among bats and risk of a rabies outbreak.

Bat Influenza A(HL18NL11) Virus in Fruit Bats, Brazil.

Screening of 533 bats for influenza A viruses showed subtype HL18NL11 in intestines of 2 great fruit-eating bats (Artibeus lituratus). High concentrations suggested fecal shedding. Genomic characterizations revealed conservation of viral genes across different host species, countries, and sampling years, suggesting a conserved cellular receptor and wide-ranging occurrence of bat influenza A viruses.

Rabies virus monitoring in bat populations in Rondônia state, Brazil

Abstract INTRODUCTION: The Jirau hydroelectric power plant built in Rondônia state has environmental impacts that could be relevant to rabies outbreaks. METHODS: Bat populations were monitored for rabies by fluorescent antibody testing and simplified fluorescent inhibition microtesting between 2010 and 2015. RESULTS: All 1,183 bats tested negative for rabies. The prevalence of rabies antibodies was 17.5% in 1,049 bats. CONCLUSIONS: The rabies antibody dosage was not reactive in samples collected before the environmental changes, and there was a progressive increase in subsequent collections that could indicate an increase in rabies virus circulation among bats and risk of a rabies outbreak.

Seroprevalence of rabies virus antibodies in bats from high risk areas in Brazilian Amazonia between 2013 and 2015.

Background: The outbreaks of human rabies that occurred between 2004 and 2005 in the Brazilian Amazon highlight the importance of bats in the transmission of this zoonosis. Ten years after, this region is still considered to be a risk area. Methods: Serum and brain tissue samples were obtained from bats captured between 2013 and 2015. The sera were tested for the presence of rabies antibodies, using the rapid fluorescent focus inhibition test, and the brain tissue samples were tested for the presence of the rabies antigen by the direct immunofluorescence method and intracerebral inoculation in mice. Results: A total of 64% (148/230) of the serum samples were seropositive, although none of the brain samples were positive for rabies infection. The seroprevalence was significantly higher in the second year of the study (p<0.001). This figure was detected in all variables (sex, age, season) and in most of the bat species. Conclusions: Our results indicate the possible occurrence of a recent peak in infection by the rabies virus in these bat populations, which represents an important alert, given that attacks by hematophagous bats are a constant threat in the study area, contributing to the probability of the occurrence of new cases of rabies.

Rabies Virus Exposure of Brazilian Free-ranging Wildlife from Municipalities without Clinical Cases in Humans or in Terrestrial Wildlife.

Rabies is a zoonosis that causes thousands of animal and human deaths worldwide. Serological studies provide information concerning rabies virus circulation among animals and humans. We evaluated the circulation of the rabies virus in wildlife in nine municipalities of São Paulo State, Brazil. We took blood samples from 27 terrestrial animals of nine different mammalian species in locations without cases of rabies in human and wild terrestrial mammals. Sera were tested with the use of the rapid fluorescent focus inhibition test (RFFIT) for the detection of rabies virus-neutralizing antibodies (RVNA). The RFFIT was positive in 100% of the samples, with many (81.48%) showing protective titer levels (>0.5 IU/mL) with other samples (18.52%) showing titers representing exposure (<0.5 IU/mL). We report RVNA in novel species (e.g., Alouatta caraya and Tapyrus terrestris). Wild animals were exposed to rabies virus in municipalities without a history of human rabies cases, which demonstrated a need for research to understand the role of these animals in the circulation and transmission of the disease.

Persistence of Rabies Virus-Neutralizing Antibodies after Vaccination of Rural Population following Vampire Bat Rabies Outbreak in Brazil.

BACKGROUND: Animal control measures in Latin America have decreased the incidence of urban human rabies transmitted by dogs and cats; currently most cases of human rabies are transmitted by bats. In 2004-2005, rabies outbreaks in populations living in rural Brazil prompted widespread vaccination of exposed and at-risk populations. More than 3,500 inhabitants of Augusto Correa (Pará State) received either post-exposure (PEP) or pre-exposure (PrEP) prophylaxis. This study evaluated the persistence of rabies virus-neutralizing antibodies (RVNA) annually for 4 years post-vaccination. The aim was to evaluate the impact of rabies PrEP and PEP in a population at risk living in a rural setting to help improve management of vampire bat exposure and provide additional data on the need for booster vaccination against rabies. METHODOLOGY/PRINCIPAL FINDINGS: This prospective study was conducted in 2007 through 2009 in a population previously vaccinated in 2005; study participants were followed-up annually. An RVNA titer >0.5 International Units (IU)/mL was chosen as the threshold of seroconversion. Participants with titers ≤0.5 IU/mL or Equivalent Units (EU)/mL at enrollment or at subsequent annual visits received booster doses of purified Vero cell rabies vaccine (PVRV). Adherence of the participants from this Amazonian community to the study protocol was excellent, with 428 of the 509 (84%) who attended the first interview in 2007 returning for the final visit in 2009. The long-term RVNA persistence was good, with 85-88.0% of the non-boosted participants evaluated at each yearly follow-up visit remaining seroconverted. Similar RVNA persistence profiles were observed in participants originally given PEP or PrEP in 2005, and the GMT of the study population remained >1 IU/mL 4 years after vaccination. At the end of the study, 51 subjects (11.9% of the interviewed population) had received at least one dose of booster since their vaccination in 2005. CONCLUSIONS/SIGNIFICANCE: This study and the events preceding it underscore the need for the health authorities in rabies enzootic countries to decide on the best strategies and timing for the introduction of routine rabies PrEP vaccination in affected areas.

VIROLOGICAL AND SEROLOGICAL DIAGNOSIS OF RABIES IN BATS FROM AN URBAN AREA IN THE BRAZILIAN AMAZON / Diagnóstico virológico e sorológico de raiva em morcegos de uma área urbana na Amazônia Brasileira

The outbreaks of rabies in humans transmitted by Desmodus rotundus in 2004 and 2005, in the northeast of the Brazilian State of Para, eastern Amazon basin, made this a priority area for studies on this zoonosis. Given this, the present study provides data on this phenomenon in an urban context, in order to assess the possible circulation of the classic rabies virus (RABV) among bat species in Capanema, a town in the Amazon basin. Bats were collected, in 2011, with mist nets during the wet and dry seasons. Samples of brain tissue and blood were collected for virological and serological survey, respectively. None of the 153 brain tissue samples analyzed tested positive for RABV infection, but 50.34% (95% CI: 45.67-55.01%) of the serum samples analyzed were seropositive. Artibeus planirostris was the most common species, with a high percentage of seropositive individuals (52.46%, 95% CI: 52.31 52.60%). Statistically, equal proportions of seropositive results were obtained in the rainy and dry seasons (c2 = 0.057, d.f. = 1, p = 0.88). Significantly higher proportions of males (55.96%, 95% CI: 48.96-62.96%) and adults (52.37%, 95% CI: 47.35-57.39%) were seropositive. While none of the brain tissue samples tested positive for infection, the high proportion of seropositive specimens indicates that RABV may be widespread in this urban area.

Os surtos de raiva em humanos transmitida por Desmodus rotundus em 2004 e 2005 no nordeste do estado do Pará, Brasil, Amazônia Oriental, fizeram desta uma área prioritária para estudos sobre essa zoonose. Diante disso, o presente estudo fornece dados sobre esse fenômeno em contexto urbano, afim de avaliar uma possível circulação do vírus clássico da raiva (RABV) entre espécies de morcegos em Capanema, cidade localizada na bacia Amazônica. Os morcegos foram coletados em 2011, com auxílio de redes de espera durante as estações seca e chuvosa. Amostras de encéfalo e de sangue foram coletadas para o diagnóstico virológico e sorológico, respectivamente. Das 153 amostras de encéfalo analisadas, nenhuma encontrou-se positiva para infecção pelo RABV, porém, 50,34% (95% CI: 45,67-55,01) das amostras de soro analisadas estavam soropositivas. Artibeus planirostris foi a espécie mais comum, e seu percentual de indivíduos soropositivos foi bem elevado (52.46%, 95% CI: 52,31-52,60). Porções estatisticamente iguais de soropositivos foram registrados nas estações (c2 = 0,057, d.f. = 1, p = 0,88). Uma porção significativamente elevada de machos (55,96%, 95% CI: 48,96%-62,96%), e adultos (52,37%, 95% CI: 47,35%-57,39%) foram soropositivos. Apesar de nenhuma das amostras de encéfalo terem sido positivas para raiva, a alta proporção de espécimes soropositivos indica uma possível circulação do RABV nessa área urbana.

VIROLOGICAL AND SEROLOGICAL DIAGNOSIS OF RABIES IN BATS FROM AN URBAN AREA IN THE BRAZILIAN AMAZON.

The outbreaks of rabies in humans transmitted by Desmodus rotundus in 2004 and 2005, in the northeast of the Brazilian State of Para, eastern Amazon basin, made this a priority area for studies on this zoonosis. Given this, the present study provides data on this phenomenon in an urban context, in order to assess the possible circulation of the classic rabies virus (RABV) among bat species in Capanema, a town in the Amazon basin. Bats were collected, in 2011, with mist nets during the wet and dry seasons. Samples of brain tissue and blood were collected for virological and serological survey, respectively. None of the 153 brain tissue samples analyzed tested positive for RABV infection, but 50.34% (95% CI: 45.67-55.01%) of the serum samples analyzed were seropositive. Artibeus planirostris was the most common species, with a high percentage of seropositive individuals (52.46%, 95% CI: 52.31 52.60%). Statistically, equal proportions of seropositive results were obtained in the rainy and dry seasons (c2 = 0.057, d.f. = 1, p = 0.88). Significantly higher proportions of males (55.96%, 95% CI: 48.96-62.96%) and adults (52.37%, 95% CI: 47.35-57.39%) were seropositive. While none of the brain tissue samples tested positive for infection, the high proportion of seropositive specimens indicates that RABV may be widespread in this urban area.

Antibodies to rabies virus in terrestrial wild mammals in native rainforest on the north coast of São Paulo State, Brazil.

Rabies causes thousands of human and animal deaths worldwide each year. The emergent importance of rabies in wild animals demonstrates the necessity of epidemiologic studies of infection in these species toward the development of better strategies for prevention and control of rabies. We analyzed the circulation of rabies virus among wildlife species from a native rainforest in São Paulo State, Brazil. We used the rapid fluorescent focus inhibition test (RFFIT) to test for rabies virus-neutralizing antibodies in 139 captured terrestrial mammals and the fluorescent antibody test (FAT), mouse inoculation test (MIT), and reverse-transcriptase (RT)-PCR to test for virus in samples from the central nervous system of 53 animals found dead. The percentage of samples positive by RFFIT was 10.8%. All samples tested by FAT, MIT, and RT-PCR were negative. Research should be continued to obtain a better understanding of the role of wildlife in the circulation and transmission of rabies virus.

Kinetics of rabies antibodies as a strategy for canine active immunization

Rabies, a zoonosis found throughout the globe, is caused by a virus of the Lyssavirus genus. The disease is transmitted to humans through the inoculation of the virus present in the saliva of infected mammals. Since its prognosis is usually fatal for humans, nationwide public campaigns to vaccinate dogs and cats against rabies aim to break the epidemiological link between the virus and its reservoirs in Brazil. During 12 months we evaluated the active immunity of dogs first vaccinated (booster shot at 30 days after first vaccination) against rabies using the Fuenzalida-Palácios modified vaccine in the urban area of Botucatu city, São Pauto state, Brazil. Of the analyzed dogs, 54.7% maintained protective titers (≥0.5 IU/mL) for 360 days after the first vaccination whereas 51.5% during all the study period. The present results suggest a new vaccination schedule for dogs that have never been vaccinated. In addition to the first dose of vaccine, two others are recommended: the second at 30 days after the first and the third dose at 180 days after the first for the maintenance of protective titers during 12 months.

Kinetics of rabies antibodies as a strategy for canine active immunization

Background Rabies, a zoonosis found throughout the globe, is caused by a virus of theLyssavirus genus. The disease is transmitted to humans through the inoculation of the virus present in the saliva of infected mammals. Since its prognosis is usually fatal for humans, nationwide public campaigns to vaccinate dogs and cats against rabies aim to break the epidemiological link between the virus and its reservoirs in Brazil.Findings During 12 months we evaluated the active immunity of dogs first vaccinated (booster shot at 30 days after first vaccination) against rabies using the Fuenzalida-Palácios modified vaccine in the urban area of Botucatu city, São Pauto state, Brazil. Of the analyzed dogs, 54.7% maintained protective titers (≥0.5 IU/mL) for 360 days after the first vaccination whereas 51.5% during all the study period.Conclusions The present results suggest a new vaccination schedule for dogs that have never been vaccinated. In addition to the first dose of vaccine, two others are recommended: the second at 30 days after the first and the third dose at 180 days after the first for the maintenance of protective titers during 12 months.(AU)

Kinetics of rabies antibodies as a strategy for canine active immunization.

BACKGROUND: Rabies, a zoonosis found throughout the globe, is caused by a virus of the Lyssavirus genus. The disease is transmitted to humans through the inoculation of the virus present in the saliva of infected mammals. Since its prognosis is usually fatal for humans, nationwide public campaigns to vaccinate dogs and cats against rabies aim to break the epidemiological link between the virus and its reservoirs in Brazil. FINDINGS: During 12 months we evaluated the active immunity of dogs first vaccinated (booster shot at 30 days after first vaccination) against rabies using the Fuenzalida-Palácios modified vaccine in the urban area of Botucatu city, São Pauto state, Brazil. Of the analyzed dogs, 54.7% maintained protective titers (≥0.5 IU/mL) for 360 days after the first vaccination whereas 51.5% during all the study period. CONCLUSIONS: The present results suggest a new vaccination schedule for dogs that have never been vaccinated. In addition to the first dose of vaccine, two others are recommended: the second at 30 days after the first and the third dose at 180 days after the first for the maintenance of protective titers during 12 months.

Serological investigation of rabies virus neutralizing antibodies in bats captured in the eastern Brazilian Amazon.

BACKGROUND: In 2004 and 2005 a total of 38 cases of human rabies transmitted by the hematophagous bat Desmodus rotundus were registered in the Brazilian state of Pará; 23 (60.5%) cases occurred in the northeastern region. Because of this, a serological investigation for the antibodies of rabies virus was performed in municipalities of the northeastern state of Pará, in order to assess whether the virus was circulating among different bat species. METHODS: Bats were collected in 2009 with mist-nets during the rainy and dry seasons and blood samples were collected for the serological survey. RESULTS: A total of 307 serum samples were obtained representing 28 bat species. The number of seropositives was high (50.8%, 156/307) and was significantly higher during the rainy season (67.4%, 95/141). No significant difference in rates was found between male and female or adult and juvenile. Seropositive individuals were recorded in 24 species sampled, the most prominent being Artibeus planirostris, with 52.2% (24/46) positive individuals. CONCLUSION: The serological proportion reported in this paper in a large numbers of individuals indicates that the rabies virus circulates quite actively in the study region, but, because of the production of antibodies, the expression of the disease in these individuals is low.

Experimental infection of the bat tick Carios fonsecai (Acari: Ixodidae) with the rabies virus.

INTRODUCTION: This study assessed the viability of the rabies virus in the argasid tick Carios fonsecai following experimental infection. METHODS: The mouse inoculation test (MIT), fluorescent antibody test (FAT) and polymerase chain reaction (PCR) were used. The rabies virus was administered to ticks via the intra-coelomic route, and the ticks were sacrificed at different time points. RESULTS: The inoculated ticks were negative for rabies according to the MIT. Ticks macerated with rabies virus were positive according to the MIT and FAT. All of the tick lots tested by PCR were positive. CONCLUSIONS The rabies virus became unviable shortly after its inoculation into tick bodies. Ticks are not likely to play an important role in the epidemiology of rabies.