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

Research (Published online: 08-01-2024)

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

I Made Kardena, Anak Agung Ayu Mirah Adi, I Nyoman Mantik Astawa, Ida Bagus Made Oka, Shafi Sahibzada, Mieghan Bruce, and Mark O’Dea

Veterinary World, 17(1): 89-98

I Made Kardena: Department of Pathobiology, Faculty of Veterinary Medicine, Udayana University, Jalan PB Sudirman, Denpasar, Bali, 80234, Indonesia; School of Veterinary Medicine and Centre for Biosecurity and One Health, Harry Butler Institute, Murdoch University, Perth, Western Australia, 6150, Australia.

Anak Agung Ayu Mirah Adi: Department of Pathobiology, Faculty of Veterinary Medicine, Udayana University, Jalan PB Sudirman, Denpasar, Bali, 80234, Indonesia.

I Nyoman Mantik Astawa: Department of Pathobiology, Faculty of Veterinary Medicine, Udayana University, Jalan PB Sudirman, Denpasar, Bali, 80234, Indonesia.

Ida Bagus Made Oka: Department of Pathobiology, Faculty of Veterinary Medicine, Udayana University, Jalan PB Sudirman, Denpasar, Bali, 80234, Indonesia.

Shafi Sahibzada: School of Veterinary Medicine and Centre for Biosecurity and One Health, Harry Butler Institute, Murdoch University, Perth, Western Australia, 6150, Australia; Australian Centre for Disease Preparedness, Commonwealth Scientific and Industrial Research Organization, Geelong, VIC 3220, Australia.

Mieghan Bruce: School of Veterinary Medicine and Centre for Biosecurity and One Health, Harry Butler Institute, Murdoch University, Perth, Western Australia, 6150, Australia.

Mark O’Dea: School of Veterinary Medicine and Centre for Biosecurity and One Health, Harry Butler Institute, Murdoch University, Perth, Western Australia, 6150, Australia.

Background and Aim: Despite the endemicity of Japanese encephalitis virus (JEV) in humans and animals in the Province of Bali, Indonesia, there is little data on whether seroconversion to the virus occurs in pigs, JEV genotypes circulating, and it’s potential mosquito vectors in the area. The aims of this study were to (i) Determine whether JEV infection in Balinese pigs occurs before reaching their sexual maturity, (ii) identify the genotypes of circulating JEV, and (iii) identify potential JEV mosquito vectors at the study sites in urban and peri-urban areas of Bali.

Materials and Methods: Sixteen 1-week-old Landrace piglets from two different sows were housed in Denpasar. Similarly, 18 one-week-old mixed-breed piglets of two different sows were housed in Badung Regency. The piglets were bled every 1 to 4 weeks for up to 24 weeks. Serum samples from the 11 piglets were tested for antibodies against JEV, and seroconversion-suspected sera were titrated using an enzyme-linked immunosorbent assay. Blood of seroconverted sera from pigs were tested using polymerase chain reaction (PCR) to detect the genetic sequence of JEV. The mosquitoes in the sentinels were trapped throughout the study period to identify the potential mosquito vectors of JEV.

Results: Antibodies were detected in most of the selected piglets’ sera from weeks 1 to 24 of their age. However, sera of pig B9 collected from the sentinel setting in Badung Regency showed a four-fold increase in antibody titer from week 4 to week 8, indicating seroconversion. PCR testing of blood from B9 (pooled blood sample collected from week 5 to week 8) identified JEV nucleic acids, which were phylogenetically classified as belonging to the JEV genotype III. Meanwhile, 1271 of two genera of mosquitoes, Anopheles spp. and Culex spp. were trapped in the pig sentinels.

Conclusion: JEV seroconversion likely occurs before the pig reaches sexual maturity in Badung Regency. Sequence data indicate that JEV genotype III is circulating in the pig sentinel setting in the regency; however, circulating genotypes need to be clarified through increased surveillance. Meanwhile, Culex spp. and most likely Culex quinquefasciatus and Anopheles spp. were the dominant mosquitoes present in the study sites set in the urban area of Denpasar and peri-urban areas of Badung, Bali, indicating that these are likely vectors in spread of JEV in the region.

Keywords: genotyping, Japanese encephalitis virus, pig sentinel setting, potential mosquito vectors, seroconversion.