Japanese encephalitis virus (JEV) is one of the leading causes of acute encephalitis in
humans. The virus is spread by mosquitoes, mainly belonging to the Culex species. The main
reservoirs are considered to be birds and pigs, with pigs constituting the most important
reservoir in regard to human infection. During the last few decades the production of pork has
increased significantly in Vietnam. With 90% of pigs being kept in households owning 10
pigs or less, pigs are widely spread across most parts of the country. Due to the ongoing
urbanization of Vietnam, the need for urban agriculture and animal husbandry has increased,
resulting in an increasing amount of pigs/reservoirs being kept in urban environments. In the
city of Can Tho, located in the Mekong delta, almost 100 % of the pigs have been found to be
JEV positive, and vectors needed for transmission of JEV have been shown to be present in
the urban areas of the city. The objectives of this study was to examine the seroprevalence of
JEV in dogs and pigs in an endemic region, and to evaluate if dogs make suitable sentinels
and could be used to evaluate the risk that JEV may pose to humans living in urban areas. To
do this, blood samples were collected from dogs and pigs. A total number of 127 dog samples
and 176 pig samples were collected from Can Tho city province and 65 samples were
collected for comparative purposes from dogs originating from Ho Chi Minh City. The
samples from Can Tho were divided into two equal parts. One part was frozen and sent to
Sweden to be tested for JEV antibodies, using a competitive IgG ELISA. One part of the
samples from Can Tho was also tested at Can Tho University using an in house HI-test. Due
to denaturation as a result of high temperature inactivation of the sera, none of the samples
that were sent to Sweden could be tested using the competitive IgG ELISA. The HI-results
showed that 27 of the 127 dog samples and 159 of the 176 pig samples, all originating from
Can Tho city province, had measurable antibody titres against JEV. Twenty three per cent of
the dogs originating from the urban district of Ninh Kieu had measurable antibody titres
against JEV. Although the seroprevalence was much higher among dogs mainly kept outdoors
than dogs mainly kept indoors, it is notable that more than 16% of the dogs mainly kept
indoors were also seropositive for JEV. These results indicate not only that JEV does pose a
risk to people living in the urban areas of Can Tho city, but also that dogs may be good
sentinels for human infection and can be used for evaluating the risk that JEV poses to
humans living in urban areas.