Rabies surveillance in bats in Northwestern State of São Paulo.

Daiene Karina Azevedo Casagrande,Danielle Bastos Araújo,Mileia Ricci Picolo,Monique Serra Lot,Cristiano De Carvalho,Luzia Helena Queiroz,Avelino Albas,Ana Beatriz Botto De Barros Da Cruz Favaro Favaro,Wagner André Pedro,Janaína Camila Borges Hernandez

doi:10.1590/0037-8682-0189-2014

Abstract

Introduction Rabies is an important zoonosis that occurs in mammals, with bats acting as Lyssavirus reservoirs in urban, rural and natural areas. Rabies cases in bats have been recorded primarily in urban areas in Northwestern State of São Paulo since 1998. This study investigated the circulation of rabies virus by seeking to identify the virus in the brain in several species of bats in this region and by measuring rabies-virus neutralizing antibody levels in the hematophagous bat Desmodus rotundus. Methods From 2008 to 2012, 1,490 bat brain samples were sent to the Universidade Estadual Paulista (UNESP) Rabies Laboratory in Araçatuba, and 125 serum samples from vampire bats that were captured in this geographical region were analyzed. Results Rabies virus was detected in the brains of 26 (2%) of 1,314 non-hematophagous bats using the fluorescent antibody test (FAT) and the mouse inoculation test (MIT). None of the 176 hematophagous bat samples were positive for rabies virus when a virus detection test was utilized. Out of 125 vampire bat serum samples, 9 (7%) had levels of rabies virus neutralization antibodies (RVNAs) that were higher than 0.5IU/mL; 65% (81/125) had titers between 0.10IU/mL and 0.5IU/mL; and 28% (35/125) were negative for RVNAs using the simplified fluorescent inhibition microtest (SFIMT) in BHK21 cells. The observed positivity rate (1.7%) was higher than the average positivity rate of 1.3% that was previously found in this region. Conclusions The high percentage of vampire bats with neutralizing antibodies suggests that recent rabies virus exposure has occurred, indicating the necessity of surveillance measures in nearby regions that are at risk to avoid diffusion of the rabies virus and possible rabies occurrences.

Highlights

Rabies is an important zoonosis that occurs in mammals, with bats acting as Lyssavirus reservoirs in urban, rural and natural areas
All samples were shipped to the Rabies Laboratory at the Universidade Estadual Paulista (UNESP) in Araçatuba for virus detection
1,314 (88.2%) were from non-hematophagous species and 176 (11.8%) were from Desmodus rotundus, which is the principal hematophagous species found in Northwestern São Paulo

Summary

Introduction

Rabies is an important zoonosis that occurs in mammals, with bats acting as Lyssavirus reservoirs in urban, rural and natural areas. Out of 125 vampire bat serum samples, 9 (7%) had levels of rabies virus neutralization antibodies (RVNAs) that were higher than 0.5IU/mL; 65% (81/125) had titers between 0.10IU/mL and 0.5IU/mL; and 28% (35/125) were negative for RVNAs using the simplified fluorescent inhibition microtest (SFIMT) in BHK21 cells. Rabies encephalitis is almost always fatal; it is caused by a virus of the Lyssavirus genus, and all mammalian species are susceptible[1,2] It is described as one of the most ancient diseases[3], it was only in 1911 that the role of bats as reservoirs and transmitters of rabies in Brazil was first considered[4]. Bats have been responsible for 70% of the human rabies cases over the past decade (2004-2013), followed by dogs, which caused 22% of the human cases[8,9]

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Results