# Lyssavirus Antibody Detection in Cave-Dwelling Bats on Cat Ba Island, Vietnam: Implications for Zoonotic Surveillance

## TL;DR

This study found evidence of lyssavirus exposure in cave-dwelling bats on Cat Ba Island, Vietnam, emphasizing the need for zoonotic disease surveillance in such environments.

## Contribution

The study provides new serological evidence of lyssavirus exposure in multiple bat species in a karst cave system in Vietnam.

## Key findings

- 29.0% of tested bats showed IgG antibodies against lyssavirus glycoprotein, indicating prior exposure.
- Lyssavirus-specific antibodies were detected in four out of five bat species, with the highest levels in Myotis pilosus.
- Caves are identified as high-risk environments for viral transmission due to close bat contact.

## Abstract

Vietnam is a significant hotspot for global biodiversity, particularly in its karst regions. The island of Cat Ba, located in the northern part of the country, features extensive cave systems that are home to diverse bat communities. We detected and quantified IgG anti-rabies viral glycoprotein in four out of the five studied cave-dwelling bat species on Cat Ba Island. These bat populations harbor lyssavirus loads, with potential implications for human and animal health.

Southeast Asia is a biodiversity hotspot for bats that can carry lyssaviruses, causing zoonotic diseases. This study detects and quantifies IgG antibodies against Lyssavirus glycoproteins in cave-dwelling bat populations on Cat Ba Island, northern Vietnam, to determine their past exposure history and the prevalence of immune responses. Samples were collected from five caves, encompassing three families and five key species (Hipposideros armiger, H. alongensis, H. poutensis, Taphozous melanopogon, and Myotis pilosus). Using ELISA with the Platelia™ Rabies II kit,(Bio-Rad Laboratories, Marnes-la-Coquette, France) 29.0% (18/62) of the bats tested positive, indicating prior exposure. The detection rate was slightly higher in females (35.7%) than in males (30.4%). Lyssavirus-specific antibodies were detected in four species, with the highest levels found in M. pilosus, followed by H. alongensis, H. armiger, and H. poutensis; no positives were found in T. melanopogon samples. One bat exhibited high seroconversion value (>4 EU/mL). The findings provide serological evidence of widespread lyssaviruses exposure in asymptomatic bats on Cat Ba Island, confirming their role as reservoirs that elicit an immune response without exhibiting rabies symptoms. This highlights the role of caves in facilitating close contact among bats, which may increase viral transmission, highlighting the need for continued surveillance in these unique roosting environments.