Rabies surveillance in wild mammals in South of Brazil

Investigation of Rabies virus in wild mammals of the atlantic forest in Rio de Janeiro, Brazil

With the successful control of rabies transmitted by dogs in Brazil, wild animals have played a relevant epidemiological role in the transmission of rabies virus (RABV). Bats, non-human primates and wild canines are the main wild animals that transmit RABV in the country. It is worth highlighting the possibility of synanthropic action of these species, when they become adapted to urban areas, causing infections in domestic animals and eventually in humans. This work aimed to evaluate the circulation of RABV in the Pedra Branca Forest, an Atlantic Forest area, located in the state of Rio de Janeiro, Southeast Brazil. Saliva and blood samples were obtained from 60 individuals of eight species of bats, captured with mist nets, and 13 individuals of callitrichid primates, captured with tomahawk traps. Saliva samples were subjected to Reverse Transcription Polymerase Chain Reaction (RT-PCR), targeting the RABV N gene, with all samples being negative. Blood samples of all animals were submitted to the Rapid Fluorescent Focus Inhibition Test (RFFIT) to detect neutralizing antibodies (Ab) for RABV. Six bat samples (8%) were seropositive for RABV with antibody titers greater than or equal to 0.1 IU/mL. The detection of Ab but not viral RNA indicates exposure rather than current RABV transmission in the analyzed populations. The results presented here reinforce the importance of serological studies in wildlife to access RABV circulation in a region.

Rabies virus circulation in a highly diverse bat assemblage from a high-risk area for zoonoses outbreaks in the Brazilian Amazon

Bats are the second most diverse order of mammals and play a central role in ecosystem dynamics. They are also important reservoirs of potentially zoonotic microorganisms, of which rabies virus is the most lethal among the bat-transmitted zoonotic pathogens. Importantly, recent outbreaks of human rabies have been reported from the Brazilian Amazon. Here we present a survey of bat species and rabies virus (RABV) circulation in a bat assemblage in the Marajó region, northern Brazil. Using data from mist-net captures and bioacoustic sampling, 56 bat species were recorded along the Jacundá River basin over a 10-day expedition in November 2022. For the investigation of RABV, we used the direct fluorescent antibody test (DFAT) and the rapid fluorescent focus inhibition test (RFFIT). In total, 159 bat individuals from 22 species were investigated for RABV. Five adults of the common vampire bat, Desmodus rotundus, showed RABV-specific antibodies in serum samples. Additionally, we report on local residents with injuries caused by D. rotundus bites and the occurrence of colonies of non-hematophagous bats from different species roosting inside human residences. This scenario raises concerns about the risks of new cases of human rabies and other zoonotic diseases associated with bats in the region and highlights the need for epidemiological surveillance and mitigation measures to prevent outbreaks of emerging infectious diseases.

Spatial clusters, temporal behavior, and risk factors analysis of rabies in livestock in Ecuador

Rabies, a globally distributed and highly lethal zoonotic neglected tropical disease, has a significant impact in South America. In Ecuador, animal rabies cases are primarily linked to livestock, and hematophagous bats play a crucial role in disease transmission. This study aims to identify temporal trends, spatial patterns, and risk factors for animal rabies in Ecuador between 2014 and 2019. Epidemiological survey reports from the official Animal Rabies Surveillance Program of the Phyto and Zoosanitary Regulation and Control Agency of Ecuador (AGROCALIDAD) were used. The Animal Rabies Surveillance Program from AGROCALIDAD consists of an official passive surveillance program that receives reports from farmers or individuals (both trained or untrained) who have observed animals with neurological clinical signs and lesions compatible with bat bites, or who have seen or captured bats on their farms or houses. Once this report is made, AGROCALIDAD personnel is sent for field inspection, having to confirm the suspicion of rabies based on farm conditions and compatibility of signs. AGROCALIDAD personnel collect samples from all suspicious animals, which are further processed and analyzed using the Direct Fluorescent Antibody (DFA) test for rabies confirmatory diagnosis. In this case, study data comprised 846 bovine farms (with intra-farm sample sizes ranging from 1 to 16 samples) located in different ecoregions of Ecuador; out of these, 397 (46.93%) farms tested positive for animal rabies, revealing six statistically significant spatial clusters. Among these clusters, three high-risk areas were identified in the southeast of Ecuador. Seasonality was confirmed by the Ljung-Box test for both the number of cases (p < 0.001) and the positivity rate (p < 0.001). The Pacific Coastal lowlands and Sierra regions showed a lower risk of positivity compared to Amazonia (OR = 0.529; 95% CI = 0.318 - 0.883; p = 0.015 and OR = 0.633; 95% CI = 0.410 - 0.977; p = 0.039, respectively). The breeding of non-bovine animal species demonstrated a lower risk of positivity to animal rabies when compared to bovine (OR = 0.145; 95% CI = 0.062 - 0.339; p < 0.001). Similarly, older animals exhibited a lower risk (OR = 0.974; 95% CI = 0.967 - 0.981; p < 0.001). Rainfall during the rainy season was also found to decrease the risk of positivity to animal rabies (OR = 0.996; 95% CI = 0.995 - 0.998; p < 0.001). This study underscores the significance of strengthening the national surveillance program for the prevention and control of animal rabies in Ecuador and other countries facing similar epidemiological, social, and geographical circumstances.

No Evidence of Rabies Exposure in Wild Marmosets (Callithrix jacchus) of Northeast Brazil

Rabies transmitted by wildlife is the main source of human rabies mortality in Latin America and considered an emerging disease. The common marmoset Callithrix jacchus of Brazil is the only known primate reservoir of rabies worldwide. We tested whether alive free-ranging C. jacchus were exposed to rabies in four northeast states that have previously reported rabies-positive dead C. jacchus (Pernambuco and Bahia) or not (Paraíba and Rio Grande do Norte). Our results show no evidence of rabies antibodies or infection in the sampled C. jacchus, suggesting that apparently healthy marmosets are not widely exposed to rabies over their natural range.

Spatio-temporal dynamics of rabies and habitat suitability of the common marmoset Callithrix jacchus in Brazil

Rabies transmitted by wildlife is now the main source of human rabies in the Americas. The common marmoset, Callithrix jacchus, is considered a reservoir of rabies causing sporadic and unpredictable human deaths in Brazil, but the extent of the spillover risk to humans remains unknown. In this study, we described the spatiotemporal dynamics of rabies affecting C. jacchus reported to Brazil’s Ministry of Health passive surveillance system between 2008 and 2020, and combined ecological niche modelling with C. jacchus occurrence data to predict its suitable habitat. Our results show that 67 outbreaks (91 cases) of rabies affecting C. jacchus were reported by 41 municipalities between January 2008 and October 2020, with a mean of 5 outbreaks/year [range: 1–14]. The maximum number of outbreaks and municipalities reporting cases occurred in 2018, coinciding with higher surveillance of primate deaths due to Yellow Fever. A mean of 3 [1–9] new municipalities reported outbreaks yearly, suggesting potential spatial expansions of the C. jacchus variant in northeastern Brazil and emerging rabies spillover from vampire bat Desmodus rotundus to C. jacchus in the north and south. Outbreaks were concentrated in the states of Ceará (72%) and Pernambuco (16%) up to 2012, but are now reported in Piauí since 2013, in Bahia since 2017 (D. rotundus’ antigenic variant, AgV3) and in Rio de Janeiro since 2019 (AgV3). Besides confirming suitable habitat for this primate in the northeast and the east coast of Brazil, our Maximum Entropy model also predicted suitable habitat on the north and the west states of the country but predicted low habitat suitability among inland municipalities of the Caatinga biome reporting rabies. Our findings revealed new areas reporting rabies infecting C. jacchus, highlighting the need to implement strategies limiting spillover to humans and to better understand the drivers of C. jacchus rabies dynamics.

Rabies virus is the deadliest virus affecting mammals. In Brazil, rabies transmitted by the common marmoset primate is emerging and causing unpredictable human deaths. This primate once endemic to the northeast of the country has now invaded regions in the south throughout human-mediated introductions. However, the dynamics of rabies in this primate and the extend of spillover risk to humans remain unknown. We found that outbreaks of rabies in this marmoset reported to the Ministry of Health are continuously reported in new areas, including three new states since 2012 and three states reporting rabies originated from the common vampire bat. We also showed that this primate has suitable habitat to invade other states in the north and west of Brazil. Preventive strategies should be implemented to limit further rabies spillover to humans in new areas.

Fecal bacterial communities of wild black capuchin monkeys (Sapajus nigritus) from the Atlantic Forest biome in Southern Brazil are divergent from those of other non-human primates

Gut microbiota are influenced by factors such as diet, habitat, and social contact, which directly affect the host's health. Studies related to gut microbiota in non-human primates are increasing worldwide. However, little remains known about the gut bacterial composition in wild Brazilian monkeys. Therefore, we studied the fecal microbiota composition of wild black capuchin monkey (Sapajus nigritus) (n=10) populations from two different Atlantic Forest biome fragments (five individuals per fragment) in south Brazil. The bacterial community was identified via the high-throughput sequencing and partial amplification of the 16S rRNA gene (V4 region) using an Ion Personal Genome Machine (PGMTM) System. In contrast to other studies involving monkey microbiota, which have generally reported the phyla Firmicutes and Bacteroidetes as predominant, black capuchin monkeys showed a high relative abundance of Proteobacteria ( χ ¯ = 80.54%), followed by Firmicutes ( χ ¯ = 12.14%), Actinobacteria ( χ ¯ = 4.60%), and Bacteriodetes ( χ ¯ = 1.31%). This observed particularity may have been influenced by anthropogenic actions related to the wild habitat and/or diet specific to the Brazilian biome's characteristics and/or monkey foraging behavior. Comparisons of species richness (Chao1) and diversity indices (Simpson and InvSimpson) showed no significant differences between the two groups of monkeys. Interestingly, PICRUSt2 analysis revealed that metabolic pathways present in the bacterial communities were associated with xenobiotic biodegradation and the biosynthesis of secondary metabolites, which may suggest positive effects on monkey health and conservation in this anthropogenic habitat. Infectious disease-associated microorganisms were also observed in the samples. The present study provides information about the bacterial population and metabolic functions present in fecal microbiota, which may contribute to a better understanding of the ecology and biology of black capuchin monkeys living in forest fragments within the Atlantic Forest biome in southern Brazil. Additionally, the present study demonstrates that the fecal bacterial communities of wild black capuchin monkeys in this area are divergent from those of other wild non-human primates.

A novel oral rabies vaccine enhances the immunogenicity through increasing dendritic cells activation and germinal center formation by expressing U-OMP19 in a mouse model

Rabies remains a public health threat in most parts of the world. Dogs, especially stray dogs, are the main sources of rabies transmission in developing countries, while wild animals are primarily responsible for the spread of rabies in developed countries and play an emerging role in rabies transmission in developing countries. Oral vaccination is the most practical method for rabies control in these animals, and the greatest challenge for oral vaccination is the hostile environment and large quantity of proteases in the gastrointestinal tract. In the present study, a promising adjuvant with potential protease inhibitory activity, unlipidated outer membrane protein 19 (U-OMP19), was inserted into the genome of the recombinant rabies virus (rRABV) strain LBNSE, designated LBNSE-U-OMP19, and the immunogenicity of LBNSE-U-OMP19 was investigated. LBNSE-U-OMP19 could potentially protect viral glycoprotein from digestion by gastrointestinal fluids in vitro. The expression of U-OMP19 attenuated viral pathogenicity by restricting viral replication in the central nervous system (CNS) and repressing the production of inflammatory chemokines and cytokines. After oral vaccination, LBNSE-U-OMP19 recruited dendritic cells (DCs), follicular helper T (T_FH) cells and germinal center (GC) B cells, promoted the formation of GCs, and increased the population of plasma cells in immunized mice, resulting in higher levels of RABV-neutralizing antibodies and better protection in mice immunized with LBNSE-U-OMP19 than in those immunized with the parent virus LBNSE. Together, our data suggest that LBNSE-U-OMP19 is a promising candidate for oral rabies vaccines.

Virome of crab-eating (Cerdocyon thous) and pampas foxes (Lycalopex gymnocercus) from southern Brazil and Uruguay

Crab-eating (Cerdocyon thous) and Pampas foxes (Lycalopex gymnocercus) are wild canids distributed in South America. Domestic dogs (Canis lupus familiaris) and wild canids may share viral pathogens, including rabies virus (RABV), canine distemper virus (CDV), and canine parvovirus 2 (CPV-2). To characterize the virome of these wild canid species, the present work evaluated the spleen and mesenteric lymph node virome of 17 crab-eating and five Pampas foxes using high-throughput sequencing (HTS). Organ samples were pooled and sequenced using an Illumina MiSeq platform. Additional PCR analyses were performed to identify the frequencies and host origin for each virus detected by HTS. Sequences more closely related to the Paramyxoviridae, Parvoviridae and Anelloviridae families were detected, as well as circular Rep-encoding single-stranded (CRESS) DNA viruses. CDV was found only in crab-eating foxes, whereas CPV-2 was found in both canid species; both viruses were closely related to sequences reported in domestic dogs from southern Brazil. Moreover, the present work reported the detection of canine bocavirus (CBoV) strains that were genetically divergent from CBoV-1 and 2 lineages. Finally, we also characterized CRESS DNA viruses and anelloviruses with marked diversity. The results of this study contribute to the body of knowledge regarding wild canid viruses that can potentially be shared with domestic canids or other species.

Review of rabies in Nepal

Rabies is a global problem, but the burden is higher in less developed or developing countries of Asia and Africa. In Nepal, rabies is reported to kill around 500 animals and up to 32 human beings in recent years, with possible under-reporting of cases and deaths. As a prophylactic measure, around 30,000 livestock and 300,000 humans get vaccinated each year in Nepal. This review summarizes the past, present and future perspectives of rabies control and prevention in Nepal. The global strategic plan of World Health Organization (WHO) aims to bring human deaths from dog-transmitted rabies to zero by 2030. To achieve this goal of ‘Zero by 30’, the concerned governmental and non-governmental agencies in Nepal should work together using the One Health concept.

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Rabies is caused by Lyssa virus that is responsible for deaths of 55,000 people annually across the world.

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Dogs are responsible for 95% of rabies cases around the globe and 99% in endemic regions.

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Asia has the highest burden of rabies and India alone accounts for around 35% of world rabies cases.

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In Nepal, less than 35 people have died each year due to rabies.

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One health approach is mandatory to end dog mediated rabies by the year 2030.

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.