First survey on seroprevalence of Japanese encephalitis in long-tailed macaques (Macaca fascicularis) in Bali, Indonesia

Abstract

Background and Aim: Japanese encephalitis (JE) is a zoonotic infectious inflammatory brain disease caused by the JE virus (JEV). Considerable research into the seroprevalence of JE in domestic animals has been conducted, but there have been no reports of its occurrence in wild animals, including long-tailed macaques (Macaca fascicularis). This study aimed to estimate the seroprevalence of JEV infection and its determinants in long-tailed macaques in Bali and the prevalence of mosquito vectors. Materials and Methods: Blood samples (3 mL) were collected from a population of M. fascicularis (92 heads) inhabiting a small forest with irrigated rice field nearby (wetland area) in Ubud, Gianyar, and from two populations in dryland areas with no wet rice field (Uluwatu, Badung, and Nusa Penida, Bali Province, Indonesia). The collected sera were tested for antibodies against JEV using a commercially available enzyme-linked immunosorbent assay kit (qualitative monkey JE Immunoglobulin G antibody kit). The seropositivity of the antibodies was then compared based on different variables, namely, habitat type, age, and sex. Results: The seroprevalence of the JEV antibodies in all the samples tested was found to be 41.3%. The seropositivity of the monkey serum samples collected from the wetland area was 46.4%, which was higher than the seropositivity of the sera samples collected from the dried field areas (1.25%). Monkey sera collected from the wetland areas were 6.1 times (odds ratio [OR]: 6.1; 95% confidence interval [CI]: 0.71-51.5, p>0.05) more likely to be seropositive compared to the monkey sera collected from the dried field areas. Meanwhile, female monkeys were 1.79 times (OR: 1.79; 95% CI: 0.76-4.21; p>0.05) more likely to be seropositive to JEV than males. Similarly, juvenile monkeys were 2.38 times (OR: 2.38; 95% CI: 0.98-5.79); p>0.05) more likely to be seropositive against the JEV than adult monkeys. However, none of these differences achieved statistical significance. Regarding the JEV mosquito vector collection, more Culex mosquitoes were found in the samples from the wetland areas than from the dried field areas. Conclusion: The study confirms the existence of JEV infection in long-tailed macaques in Bali. There were patterned seropositivity differences based on habitat, age, and sex of the monkeys, but these were not significant. The possibility of monkeys as a JEV reservoir and the presence of the mosquitoes as the JEV vector are suggested but require more study to confirm.

A Serosurvey of Japanese Encephalitis Virus in Monkeys and Humans Living in Proximity in Thailand

“…However, our understanding of this zoonotic virus is still incomplete. Since the presence of JEV antibodies in NHPs is clearly reported in previous studies [ 11 , 12 , 13 ], we investigate seropositivity against JEV in monkeys at an animal–human interface in Thailand. We chose two provinces close to the capital Bangkok with a high density of monkeys living in proximity to human populations for this study.…”

“…In agreement with JEV seroprevalence in monkeys ( Macaca fascicularis ) in Malaysia [ 13 ] and the study in captive monkeys ( Macaca nemestrina ) in Northern Thailand [ 21 ], the seropositivity rate observed from monkeys living in study site 1 was 14.3%. However, studies conducted on monkeys ( Macaca fascicularis ) in Indonesia and the Philippines had a higher seropositivity rate of 41.3% and 35.2%, respectively [ 11 , 12 ]. Even captive monkeys ( Macaca fuscata ) in Japan showed a higher seropositivity rate of 44% [ 22 ].…”

“…In contrast to domestic animals, the role of wild vertebrates such as monkeys in the JEV transmission cycle has not been intensively studied. There have been a few studies reporting the seroprevalence of JEV in long-tailed macaques ( Macaca fascicularis ) with varying results [ 11 , 12 , 13 ]. The presence of antibodies in these long-tailed macaques indicates natural infection.…”

Diversity of mosquito species and potential arbovirus transmission in long-tailed macaque (Macaca fascicularis) breeding facilities

“…Stegomyia is the major subgenus among Aedes mosquitoes from which ZIKV has been isolated (nine species). A serosurveillance of JEV in longtailed macaques was recently reported in Bali and found 41.3% positivity for JEV antibodies [11].…”

Seroconversion, genotyping, and potential mosquito vector identification of Japanese encephalitis virus in pig sentinel settings in Bali, Indonesia

“…Therefore, to determine which mosquito populations contribute to JEV transmission, assessing potential mosquito vectors in the areas where human JE cases are detected is important. In addition, although four of the five genotypes (genotypes I to IV) have been documented in Indonesia [13], despite the endemicity of JEV in humans and animals in Bali [14], there is little data provided on which JEV genotypes are circulating in the area. To better understand the existence and circulation of the virus circulating in Bali compared to other areas in the country, studies on genotyping the virus circulating in Bali are required.…”