Epsilon Archive for Student Projects

Abstract

Japanese encephalitis is the leading cause of encephalitis in Asia. The disease is caused by
Japanese encephalitis virus (JEV), a vector-borne virus that has an enzootic cycle involving
mosquitoes, pigs and birds. Surveillance programs for detection of virus activity can function
as an early warning system of increased risk of transmission and disease outbreak. Surveillance
of JEV infection is often performed using sentinel animals like pigs. Dogs have recently been
shown to be good sentinels as well. The objective of this study was to determine the
seroprevalence and to assess the host factors in pigs and dogs favoring JEV infection in
Vietnam. For this purpose, 114 blood samples were collected from dogs in rural areas in the
provinces of Hai Duong and Thai Binh in northern Vietnam. Ten blood samples were retrieved
from pigs in the same areas. In addition, 250 blood samples were collected from pigs originating
from all over Vietnam, in a slaughterhouse in Hanoi. Blood samples were tested for antibodies
against JEV using a competitive ELISA method. A total of 30% pigs (n =78) and 72% of dogs
(n=82) were JEV seropositive. The seroprevalence in pigs found in this study is much lower
than the previously found; in the range of 60-100%.This could be indicative of a reduced
infection pressure due to the ongoing depopulation of pigs as a result of the recent outbreak of
African swine fever in the country. Further, the seroprevalence was lower in the south and
south-central areas (19-26%) compared to the north (87%). The seroprevalence among dogs
was higher than in earlier studies suggesting that people in these areas are exposed to JEV in
high extent. The results from the dog samples show a possible correlation between age and JEV
seropositivity. Also breed seems to play a role for the risk of being seropositive.