Abstract
Rabies is a fatal zoonotic disease that can affect all mammals.
Following the directives of the rabies ordinance of the Government of
Hong Kong, all wild macaques captured under an ongoing sterilization
program (since 2000) were vaccinated against rabies. The main objective
of this study was to assess the serological response to rabies
vaccination in the population of Hong Kong macaques. An inactivated
rabies vaccine was subcutaneously administered to captured macaques
under anesthesia. In a 2015 field survey, blood samples from the animals
were collected and stored in -80℃ freezer. In July 2021, all frozen sera
from vaccinated animals were prepared and tested for antibodies against
rabies virus using a commercial enzyme-linked immunosorbent assay
(ELISA) test. The test results were dichotomized at the recommended
cut-off point of the test kit. Sixty-five samples from the vaccinated
macaques were available for this study. All of these animals had
received at least one dose of vaccine (1 st
vaccination) between 2008 and 2015. The interval between the 1
st vaccination and blood sampling dates ranged from 21
to 2,779 days. Only five of the 65 macaques had a second vaccination
record at the time of sampling; all five had high antibody levels. Among
the remaining macaques, 77% (46/60) were positive for rabies
antibodies. No specific association was observed between the
post-vaccination period and the antibody titer of these macaques and no
adverse reactions to vaccination were reported. The current vaccination
strategy in Hong Kong macaques appears to effectively elicit rabies
antibodies in a high proportion of macaque populations in the wild
(78-87%). However, reaching the precise level of protection against a
potential challenge with the virus should further be investigated.