Rabies surveillance in wild mammals in South of Brazil

Abstract

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.

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

“…In particular, most human deaths and livestock losses from rabies in the continent are now attributed to spillover from vampire bats, Desmodus rotundus ( 6 – 8 ). Foxes (specifically the crab-eating fox Cerdocyon thous ) and primates (specifically the marmoset Callithrix jacchus ) are also considered reservoirs of specific RABV variants ( 9 – 12 ), while serological studies show evidence of rabies exposure in several other primate and marsupial species but without evidence of clinical infections ( 13 , 14 ).…”

“…In large and biodiverse countries such as Brazil, rabies circulates among a wide range of wild species including bats, primates, and foxes, complicating the establishment of preventative measures aiming to limit rabies spillover to humans and domestic animals ( 15 – 17 ). The high cost and current uncertainties in the interpretation of serological data among wildlife has restricted the implementation of serology to a small number of wild populations and specific regions of the country ( 12 ). In the Northeast region, crab-eating fox and bats have been frequently found exposed or infected, while transmission of RABV from foxes to domestic dogs has been reported ( 16 , 18 ).…”

“…Marmosets are also host to a distinct RABV variant in the Northeast region of Brazil ( 9 , 11 ). In the states of São Paulo and Rio Grande do Sul (RGS) in Southern Brazil, RABV circulation has been detected in vampire bats, insectivorous bats, capuchin monkeys, and crab-eating foxes ( 12 – 14 , 19 – 21 ). These reports suggest the circulation of rabies among different wildlife populations in several regions of the country, posing risks to humans and domestic animals that will depend upon contacts between these populations.…”

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

“…In Brazil, RABV was controlled in domestic dogs by intense public vaccination campaigns (Freire de Carvalho et al, 2018). However, the circulation of RABV in wildlife has become a major concern for public health (Antunes et al, 2018;Campos et al, 2019;Rocha et al, 2017), where biting of humans by wild animals has been reported. Moreover, crabeating foxes were identified as reservoirs of RABV variants (Campos et al, 2019;Rocha et al, 2017).…”

Predicting the presence and titre of rabies virus‐neutralizing antibodies from low‐volume serum samples in low‐containment facilities

“…Titres ≤ 0.1 IU/ml were considered RVNA‐negative and > 0.1 IU/ml were considered RVNA‐positive. Other serology studies in wildlife have used similar thresholds to detect RVNA (Araujo et al., 2014; Campos et al., 2019; Marcelo Azevedo de Paula Antunes et al, 2017; Silva et al., 2010). To predict RVNA titres, a GLMM with a log‐normal distribution was fit to the infected cell counts across the SRIG concentration series.…”