Rabies neutralizing antibodies in terrestrial sylvatic animals from a region in Brazil endemic for two independent wildlife rabies variants

Abstract

Purpose: Rabies is a zoonotic viral disease that still presents importance in different regions of the World. Rabies lyssavirus (RBV) wildlife species has emergent importance in Brazil, in the Northeast region, two species of terrestrial mammals – marmosets and crab eating foxes were identified as reservoirs of independent RBV variants responsbible for annual cases in these species, domestic animals and humans. The aim of this study was the detection of rabies neutralizing antibodies (RVNAs) in terrestrial sylvatic mammals from an endemic region for wildlife rabies. Methods & Materials: Serum samples were collected from animals captured in peridomestic environments or kept as pets. RVNAs were detected using Rapid Fluorescent Focus Inhibition Test – RFFIT according to the WHO guidelines. A sample was considered positive when a complete neutralization was observed from the first dilution (1:5) and the cut-off value was established 0.11 IU/mL. Results: A total of 159 samples from 10 different species were tested. Out of these, 16 (10%) presented positive titers: 07 capuchin monkeys, 05 marmosets, 03 crab eating foxes and 01 raccoon. With the exception of the capuchin monkeys, all animals were free ranging and from regions presenting cases of RBV due to the two terrestrial wildlife variants from Brazil. The RVNAs observed indicate that the animals had previous contact with the virus. The ways in which animals can make contact with the virus in nature are unclear and can be a consequence of an insufficient amount of virus to produce the infection. The capuchin monkeys were kept as pets and were probably vaccinated during the vaccination campaigns for cats and dogs. Conclusion: The detection of RVNAs demonstrates the possibility of contact with RBV without apparent disease and the response to the misuse of the vaccine aimed to cats and dogs. There is a lack of data regarding RVNAs in sylvatic animals from wildlife rabies endemic regions, and Brazil does not have wildlife vaccination campaigns. Samplings of the animals were made considering animal, environmental and human interactions characteristics. These results can be important for the adoption of more efficient measures for wildlife rabies surveillance and control, as the implementation of specific terrestrial wildlife vaccination.