The Importance of Wild Canids in the Epidemiology of Rabies in Northeast Brazil: A Retrospective Study

Cross-correlation and time series analysis of rabies in different animal species in Nepal from 2005 to 2018

Rabies is a fatal zoonotic disease, resulting in human and livestock deaths. In Nepal, animal rabies has posed a significant challenge to public health. Because animals are the primary source of rabies in humans, a better understanding of rabies epidemiology in animals is necessary. The objectives of this study were to determine the correlation between rabies occurrences in dogs and livestock animals and to detect the trends and change points of the disease using longitudinal data. The nationwide rabies dataset from 2005 to 2018 was analyzed using cross-correlation, multiple change points, and time series methods. Autoregressive Integrated Moving Average (ARIMA) and Neural Network Autoregression (NNAR) were applied to the time series data. The results show a positive correlation between canine rabies and livestock rabies occurrences. Three significant change points were detected in the time series data, demonstrating that the occurrences were high in the initial years but stabilized before peaking to an upward trend in the final years of the study period. Nonetheless, there was no seasonality pattern in rabies occurrences. The most suitable models were ARIMA (2,1,2) and NNAR (5,1,4) (12). Based on the study findings, both locals and tourists in Nepal need to have enhanced awareness of the potential dangers posed by rabies in canines and livestock. This study offers much-needed insight into the patterns and epidemiology of animal rabies which will be helpful for policymakers in drafting rabies control plans for Nepal.

Fifty Years of the National Rabies Control Program in Brazil under the One Health Perspective

In 1973, the National Rabies Program was created in Brazil through an agreement between the Ministry of Health and Agriculture. Since its beginning, it developed integrated action through access to free post-exposure prophylaxis (PEP) for people at risk, dog vaccination campaigns, a joint surveillance system, and awareness. This study aims to describe human rabies in Brazil under the One Health perspective in recent decades, including achievements in the control of dog-mediated cases and challenges in human cases transmitted by wild animals. This paper also explores possible drivers of human rabies in the Northeast Region with half of the cases. The first part of this study was descriptive, presenting data and examples by periods. Statistical analysis was performed in the last period (2010-2022) to explore possible drivers. Dog-mediated human cases decreased from 147 to 0, and dog cases decreased from 4500 to 7. A major challenge is now human cases transmitted by wild animals (bats, non-human primates, and wild canids). Most current human cases occur in municipalities with a tropical and subtropical moist broadleaf forest biome and a Gini index higher than 0.5. In the multivariable analysis, an association with temperature was estimated (OR = 1.739; CI95% = 1.181-2.744), and primary healthcare coverage (OR = 0.947; CI95% = 0.915-0.987) was identified as a protector. It is possible to significantly reduce the number of dog-mediated human rabies cases through the efforts presented. However, Brazil has wildlife variants of the rabies virus circulating. The association of human cases with higher temperatures in the Northeast is a concern with climate change. To reduce human cases transmitted by wild animals, it is important to continue distributing free PEP, especially in remote at-risk areas in the Amazon Region, and to increase awareness.

Role of Brazilian bats in the epidemiological cycle of potentially zoonotic pathogens

Bats (Chiroptera) are flying mammals of great biodiversity and habits. These characteristics contribute for them being natural reservoirs and part of the epidemiological cycle of several potentially zoonotic pathogens, such as viruses, protozoa, fungi and bacteria. Brazil hosts approximately 15% of the world's bat diversity, with 181 distinct species, 68 genera and 9 families. About 60% of infectious diseases in humans are of zoonotic origin and, in the last decades, the detection of zoonotic pathogens in bats and their environment has been reported, such as Rabies virus (RABV) and Histoplasma capsulatum. Thus, the aim of this work was to review the reports of zoonotic pathogens associated with bats in Brazil in the past ten years. We reviewed the main pathogenic microorganisms described and the species of bats most frequently involved in the epidemiological cycles of these zoonotic agents. The obtained data show an upward trend in the detection of zoonotic pathogens in Brazilian bats, such as RABV, Bartonella sp., Histoplasma capsulatum and Leishmania spp., with emphasis on the bat species Artibeus lituratus, Carollia perspicillata, Desmodus rotundus and Molossus molossus. These findings highlight the importance of monitoring bat-associated microrganisms to early identify pathogens that may threaten bat populations, including potentially zoonotic microrganisms, emphasizing the importance of the One Health approach to prevent and mitigate the risks of the emergence of zoonotic diseases.

Rabies Elimination: Is It Feasible without Considering Wildlife?

Rabies is a vaccine-preventable fatal viral disease that is zoonotic in nature. In this article, we provide a justification why the agreement of the World Health Organization (WHO), the Food and Agriculture Organization (FAO), the World Organization for Animal Health (OIE), and Global Alliance for Rabies Control (GARC) on The Global Strategic Plan to End Human Deaths from Dog-mediated Rabies by 2030 should also include a more holistic approach and ecologic views.

Clinical aspects of human rabies in the state of Ceará, Brazil: an overview of 63 cases

INTRODUCTION

Rabies is considered one of the most relevant public health problems owing to its high fatality rate and the high number of deaths worldwide.

METHODS

We included patients with human rabies who attended a reference hospital in the state of Ceará during 1976-2019.

RESULTS

Data were available for 63 out of 171 (36.8%) patients. Of these patients, 48 (76.2%) were attacked by dogs. In recent years, wild animals have been the most common aggressor species (marmosets and bats). Only 39 (70%) patients were initially correctly suspected with rabies. Bites were the most frequent exposure (56; 96%), most commonly on the hands (21; 42%) and the head (9; 18.4%). Only 14 (22%) patients had sought medical assistance before the onset of symptoms, and only one completed post-exposure prophylaxis. The most prevalent signs and symptoms included aggressiveness/irritability (50; 79.4%), fever (42; 66.7%), sore throat/dysphagia (40; 63.5%), and myalgia (28; 44.4%). Hydrophobia was present in 17 patients (22.0%).

CONCLUSIONS

Most cases of human rabies in Ceará occurred due to the failure to seek medical assistance and/or the failure of the health system in initiating early post-exposure prophylaxis. There is a need for specific information and education campaigns focusing on the cycle of sylvatic rabies as well as prevention measures. Health professionals should undergo refresher training courses on the signs and symptoms of rabies and on the specific epidemiological features of the disease in Brazil.

EXPOSURE OF WILD BOAR (SUS SCROFA) TO THE COMMON VAMPIRE BAT AND LACK OF IMMUNE PROTECTION TO RABIES VIRUS IN BRAZILIAN HUNTERS

Rabies virus is recognized as one of the most fatal zoonotic agents affecting all mammals. Wild boars (Sus scrofa), classified as a large-size exotic invasive species in Brazil with nationwide hunting permitted, may serve as an extra blood source for the common vampire bat (Desmodus rotundus). Our aim was to document wild boar exposure to vampire bats to determine the seroprevalence of rabies virus antibodies in wild boars and to determine the immune status of hunters in southern and central-western Brazilian regions. Serum samples were collected from 80 wild boars and 49 hunters from natural and degraded areas of the Atlantic Forest biome of southern Brazil and in degraded areas of the Cerrado biome of central-western Brazil. The rabies-modified rapid fluorescent focus inhibition test was performed to detect the presence of rabies virus neutralizing antibodies in wild boars and considered seropositive when ≥0.10 IU/mL. The simplified fluorescence inhibition microtest was used for samples from hunters with a titer of ≥0.50 IU/mL and considered indicative of seroconversion. While 11% (9/80) of wild boars had serum titers for rabies exposure (≥0.10 IU/mL), 88% (43/49) of corresponding hunters lacked immune protective titers (<0.50 IU/mL). Wild boars showed serum titers for rabies likely due to contact with contaminated saliva of vampire bats or from infected carcass consumption. Additionally, Brazilian wild boars can be exposed to rabies and may play an important role in the sylvatic rabies cycle by providing a blood supply for vampire bats, highlighting the possibility of direct transmission of rabies virus to hunting dogs and hunters. These findings suggested hunters are a potential risk group for contracting rabies, and the World Health Organization may consider adding this occupation to their recommendations of who should receive the pre-exposure rabies vaccination.

Could a rabies incursion spread in the northern Australian dingo population? Development of a spatial stochastic simulation model

Australia, home to the iconic dingo, is currently free from canine rabies. However northern Australia, including Indigenous communities with large free-roaming domestic dog populations, is at increased risk of rabies incursion from nearby Indonesia. We developed a novel agent-based stochastic spatial rabies spread model to evaluate the potential spread of rabies within the dingo population of the Northern Peninsula Area (NPA) region of northern Australia. The model incorporated spatio-temporal features specific to this host-environment system, including landscape heterogeneity, demographic fluctuations, dispersal movements and dingo ecological parameters—such as home range size and density—derived from NPA field studies. Rabies spread between dingo packs in nearly 60% of simulations. In such situations rabies would affect a median of 22 dingoes (approximately 14% of the population; 2.5–97.5 percentiles: 2–101 dingoes) within the study area which covered 1,131 km², and spread 0.52 km/week for 191 days. Larger outbreaks occurred in scenarios in which an incursion was introduced during the dry season (vs. wet season), and close to communities (vs. areas with high risk of interaction between dingoes and hunting community dogs). Sensitivity analyses revealed that home range size and duration of infectious clinical period contributed most to the variance of outputs. Although conditions in the NPA would most likely not support a sustained propagation of the disease in the dingo population, due to the predicted number of infected dingoes following a rabies incursion and the proximity of Indigenous communities to dingo habitat, we conclude that the risk for human transmission could be substantial.

Although Australia is free from canine rabies, an incursion from nearby rabies-infected Indonesian islands is a realistic threat. The ubiquitous presence of dingoes in the wild, in association with large populations of free-roaming domestic dogs from northern Australian Indigenous communities, increases the risk of a rabies outbreak. Using a newly developed simulation model, we investigated the potential spread of rabies in a northern Australian dingo population. Nearly 60% of model simulations resulted in more than one pack infected. When spread did occur, outbreaks affected a median of 22 dingoes (an estimated 14% of the population in this area). The duration of infection, proportion of the population infected and spatial spread of the outbreak was greatest when rabies was introduced during the dry season and close to communities. Our results demonstrate that an incursion of rabies into the northern Australian dingo population would likely lead to a rabies outbreak, which would in turn pose a substantial threat to Indigenous communities in northern Australia.

Using host traits to predict reservoir host species of rabies virus

Wildlife are important reservoirs for many pathogens, yet the role that different species play in pathogen maintenance frequently remains unknown. This is the case for rabies, a viral disease of mammals. While Carnivora (carnivores) and Chiroptera (bats) are the canonical mammalian orders known to be responsible for the maintenance and onward transmission of rabies Lyssavirus (RABV), the role of most species within these orders remains unknown and is continually changing as a result of contemporary host shifting. We combined a trait-based analytical approach with gradient boosting machine learning models to identify physiological and ecological host features associated with being a reservoir for RABV. We then used a cooperative game theory approach to determine species-specific traits associated with known RABV reservoirs. Being a carnivore reservoir for RABV was associated with phylogenetic similarity to known RABV reservoirs, along with other traits such as having larger litters and earlier sexual maturity. For bats, location in the Americas and geographic range were the most important predictors of RABV reservoir status, along with having a large litter. Our models identified 44 carnivore and 34 bat species that are currently not recognized as RABV reservoirs, but that have trait profiles suggesting their capacity to be or become reservoirs. Further, our findings suggest that potential reservoir species among bats and carnivores occur both within and outside of areas with current RABV circulation. These results show the ability of a trait-based approach to detect potential reservoirs of infection and could inform rabies control programs and surveillance efforts by identifying the types of species and traits that facilitate RABV maintenance and transmission.

Using Surveillance of Animal Bite Patients to Decipher Potential Risks of Rabies Exposure From Domestic Animals and Wildlife in Brazil

Direct contact with domestic animals and wildlife is linked to zoonotic spillover risk. Patients presenting with animal-bite injuries provide a potentially valuable source of surveillance data on rabies viruses that are transmitted primarily by animal bites. Here, we used passive surveillance data of bite patients to identify areas with high potential risk of rabies transmission to humans across Brazil, a highly diverse and populous country, where rabies circulates in a range of species. We analyzed one decade of bite patient data from the national health information system (SINAN) comprising over 500,000 patients attending public health facilities after being bitten by a domestic or wild animal. Our analyses show that, between 2008 and 2016, patients were mostly bitten by domestic dogs (average annual dog bite patients: 502,043 [436,391-544,564], annual incidence per state: 258 dog bites/100,000 persons) and cats (76,512 [56,588-97,580] cat bites, 41 cat bites/100,000/year), but bites from bats (4,172 [3,351-5,365] bat bites, 2.3/100,000/year), primates (3,320 [3,013-3,710] primate bites, 2.0/100,000/year), herbivores (1,908 [1,492-2,298] herbivore bites, 0.9/100,000/year) and foxes (883 [609-1,086] fox bites, 0.6/100,000/year) were also considerable. Incidence of bites due to dogs and herbivores remained relatively stable over the last decade. In contrast bites by cats and bats increased while bites by primates and foxes decreased. Bites by wild animals occurred in all states but were more frequent in the North and Northeast of Brazil, with over 3-fold differences in incidence between states across all animal groups. Most bites reported from domestic animals and wildlife occurred in urban settings (71%), except for bites from foxes, which were higher in rural settings (57%). Based upon the Ministry of Health guidelines, only half of patients received the correct Post-Exposure Prophylaxis following a bite by a suspect rabid animal. We identified areas and species of high-risk for potential zoonotic transmission of rabies in Brazil and reveal that, despite increasing human encroachment into natural ecosystems, only patients reporting bites by bats increased. Our study calls for future research to identity the socio-ecological factors underlying bites and the preventive measures needed to reduce their incidence and potential risk of rabies transmission.

Increased detection of rabies virus in bats in Ceará State (Northeast Brazil) after implementation of a passive surveillance programme

The intensification of dog, cat and livestock vaccination campaigns significantly reduced rabies cases in humans and domestic animals in Ceará State, Brazil. However, sylvatic animals-bats (order Chiroptera), wild canids, raccoons and non-human primates- remain as reservoirs for the virus. Our hypothesis is that surveillance and monitoring of rabies virus in bats, especially passive surveillance, is of fundamental importance, besides the implementation of health education and strengthening of surveillance actions in humans exposed to aggressions. Thus, we assessed the occurrence of rabies virus in animals focusing on bats, before and after launching of the Sylvatic Rabies Surveillance Program in 2010. Surveillance data from the 184 municipalities of Ceará State were analysed, collected during the periods 2003-2010 (active surveillance) and 2011-2016 (passive surveillance), respectively. A total of 13,543 mammalian samples were received for rabies diagnosis from 2003 to 2016. Of these, 10,960 were from dogs or cats (80.9%), 1,180 from bats (8.7%), 806 from other sylvatic animals (foxes, marmosets, raccoons; 6.0%) and 597 from herbivores (cattle, goats, sheep, equines, pigs; 4.4%). A total of 588 (4.3%) samples were positive for rabies. About 8.4% (99/1,180) of the bat samples were infected with rabies virus, 92 (92.9%) of these were from non-haematophagous bat species and 7 (7.1%) from haematophagous species. The number of bat samples received and infection rates increased considerably, after a shift from active surveillance (9/355 [2.5%] samples positive), to passive surveillance (90/825 [10.9%] samples positive). Surveillance of rabies virus in bats is fundamental for human and domestic animal health in Ceará State. Bats have to be considered as targets in surveillance and control programmes. Virus lineages should be characterized to increase knowledge on transmission dynamics of sylvatic rabies virus to domestic animals and the human population, and to provide additional evidence for planning and implementation of improved control measures.

Rabies surveillance in wild mammals in South of Brazil

The sylvatic cycle of rabies, caused by the Rabies lyssavirus (RABV), is maintained in the American Continent by aerial and terrestrial wild mammals. In this study, we combined passive surveillance of rescued wild animals with active serological surveillance in targeting areas at Rio Grande do Sul State and Santa Catarina State, south of Brazil, where bites of humans by wild animals have been reported. Circulation of RABV in Brazilian bats has been extensively demonstrated; however, the observation of such infections in unvaccinated terrestrial mammals is restricted to some regions of the Brazilian territory. The occurrence of rabies infection in unvaccinated animals has been identified by the detection of RABV antigens in brain tissues of dead animals or anti-rabies antibodies in live animals. Such strategies allow the surveillance of rabies and the assessment of spillover risks from infected animals to humans. Our aim included the identification of species of wild mammals that are involved in the sylvatic cycle of rabies virus in Southern Brazil and to assess the risk of rabies infection in patients bitten by wild animals in the state. To assess the anti-rabies seropositivity, sera were submitted to the Rapid Fluorescent Focus Inhibition Test (RFFIT). Among the 100 mammals tested, five animals were seropositive (5%) including three (one primate and two wild canids) with rabies virus neutralizing antibodies titres >0.5 IU/ml. Our results highlight the exposure to RABV of both primates and wild canids in Southern Brazil and suggest the occurrence of RABV exposure without the development of further symptoms. Further research should clarify the dynamics of rabies in wild canids and whether primates are accidental hosts or reservoirs for RABV at this region.

Safety and efficacy results of simulated post-exposure prophylaxis with human immune globulin (HRIG; KEDRAB) co-administered with active vaccine in healthy subjects: a comparative phase 2/3 trial

We conducted a clinical trial to assess the safety and putative efficacy of an additional human rabies immune globulin (HRIG; KEDRAB) versus an older product (Comparator, HyperRAB S/D® [Grifols]) and determine whether HRIG interferes with development of endogenous antibodies versus Comparator, when each is given with an active rabies vaccine. This was a prospective, double-blind, single-period, non-inferiority study in which subjects were randomized (1:1) to a single dose (20 IU/kg) of HRIG or Comparator on day 0 and rabies vaccine (RabAvert® [GlaxoSmithKline]; 1 mL of ≥2.5 IU/mL) on days 0, 3, 7, 14, and 28. Anti-rabies antibodies were measured by rapid fluorescent focus inhibition test on day 14, and subjects were followed until day 185. Rabies virus neutralizing antibody (RVNA) titers ≥0.5 IU/mL were considered seroconversion putatively indicative of protection. The non-inferiority criterion was the lower limit of the 90% confidence interval (CI) >–10%, for the between-group difference in the proportion of subjects achieving RVNA ≥0.5 IU/mL. On day 14, 98.3% of 59 subjects in the HRIG group and 100% of 59 in the Comparator group had RVNA ≥0.5 IU/mL (difference between proportions – 1.8%; 90% CI, – 8.2, 3.1; non-inferiority criterion met). One subject in the HRIG group did not meet the seroconversion criteria for anti-rabies antibody, and one subject in the Comparator group showed an anamnestic response, with much higher than expected anti-rabies antibody levels at both baseline and on day 14. Thus, HRIG allows for prophylactic anti-rabies antibody titers and is non-inferior to Comparator, when administered with rabies vaccine.

Atendimentos antirrábicos humanos pós-exposição: tendência temporal de sua prevalência no Ceará, de 2007 a 2015

Resumo Introdução A principal recomendação para o controle da raiva em humanos é a vacinação profilática. Objetivo Considerando-se a endemicidade da raiva no Brasil e o direcionamento das ações de controle, buscou-se caracterizar a tendência temporal dos atendimentos antirrábicos humanos pós-exposição no Ceará, de 2007 a 2015. Método O estudo é ecológico de tendência temporal e analítico. Os dados das fichas de atendimento antirrábico foram organizados em planilhas e calculados os coeficientes anuais de prevalência. Resultados Houve 231.694 atendimentos antirrábicos, com coeficientes de prevalência crescentes de 2007 a 2011 (35,09 por 10.000 habitantes; APC=13,5; p<0,001) e ápice em 2015 (40,35 por 10.000 habitantes; APC=5,5; p=0,005). Houve um aumento na faixa etária de 20 a 59 anos (APC=14,0; p<0,001), e residentes da zona urbana (APC=7,0; p<0,001). A espécie canina teve tendência crescente de 2007 a 2011 (APC=14,3; p<0,001). Das notificações, 95,8% apresentaram condutas inadequadas, com crescimento nos coeficientes de prevalência de 2007 a 2011 (APC=13,6; p<0,001). Conclusão As condutas profiláticas inadequadas aconteceram mais de 2007 a 2011. A análise temporal, com tendência crescente no período analisado, deve ser utilizada como componente contínuo das ações de vigilância da raiva no Ceará, para assistência adequada e segura aos pacientes vítimas de agressão animal.

Bat rabies surveillance and risk factors for rabies spillover in an urban area of Southern Brazil

BACKGROUND

Bat rabies surveillance data and risk factors for rabies spillover without human cases have been evaluated in Curitiba, the ninth biggest city in Brazil, during a 6-year period (2010-2015). A retrospective analysis of bat complaints, bat species identification and rabies testing of bats, dogs and cats has been performed using methodologies of seasonal decomposition, spatial distribution and kernel density analysis.

RESULTS

Overall, a total of 1003 requests for bat removal have been attended to, and 806 bats were collected in 606 city locations. Bat species were identified among 13 genera of three families, with a higher frequency of Nyctinomops in the central-northern region and Molossidae scattered throughout city limits. Out of the bats captured alive, 419/806 (52.0%) healthy bats were released due to absence of human or animal contacts. The remaining 387/806 (48.0%) bats were sent for euthanasia and rabies testing, which resulted in 9/387 (2.32%) positives. Linear regression has shown an increase on sample numbers tested over time (regression: y = 2.02 + 0.17×; p < 0.001 and r2 = 0.29), as well as significant seasonal variation, which increases in January and decreases in May, June and July. The Kernel density analysis showed the center-northern city area to be statistically important, and the southern region had no tested samples within the period. In addition, a total of 4769 random and suspicious samples were sent for rabies diagnosis including those from dogs, cats, bats and others from 2007 to 2015. While all 2676 dog brains tested negative, only 1/1136 (0.088%) cat brains tested positive for rabies.

CONCLUSION

Only non-hematophagous bats were collected during the study, and the highest frequency of collections occurred in the center-northern region of the city. Rabies spillover from bats to cats may be more likely due to the registered exposure associated with cats' innate hunting habits, predisposing them to even closer contact with potentially infected bats. Although associated with a very low frequency of rabies, cats should always be included in rabies surveillance and vaccination programs.

Re-emergence of rabies virus maintained by canid populations in Paraguay

Paraguay has registered no human cases of rabies since 2004, and the last case in dogs, reported in 2009, was due to a variant maintained in the common vampire bat "Desmodus rotundus". In 2014, a dog was diagnosed as positive for rabies with aggression towards a boy and all required measures of control were successfully adopted. Epidemiological investigation revealed that the dog was not vaccinated and had been attacked by a crab-eating fox, "zorro" (Cerdocyon thous). The sample was diagnosed by the Official Veterinary Service of the Country and sent to the Center on Rabies Research from the University of São Paulo, Brazil, for antigenic and genetic characterization. A second sample from a dog positive for rabies in the same region in 2015 and 11 samples from a rabies outbreak from Asuncion in 1996 were also characterized. The antigenic profile of the samples, AgV2, was compatible with one of the variants maintained by dogs in Latin America. In genetic characterization, the samples segregated in the canine (domestic and wild species)-related group in an independent subgroup that also included samples from Argentina. These results and the epidemiology of the case indicate that even with the control of rabies in domestic animals, the virus can still circulate in wildlife and may be transmitted to domestic animals and humans, demonstrating the importance of continuous and improved surveillance and control of rabies, including in wild species, to prevent outbreaks in controlled areas.