Connections of top-flight gallopers Sacred Kingdom and California Memory may have to wait another week for definitive Nipah virus test results before they know when their horses will be able to leave Singapore.
California Memory and two British horses, Presvis and Wigmore Hall, have shown a positive reaction to screening tests indicating the possible presence of the deadly virus after running in the Singapore International Airlines Cup last weekend.
Sacred Kingdom, who has not shown the same results, is being kept in Singapore pending final results of testing in Australia as he was stabled close to California Memory.
'As I understand it, the original screening tests have been rerun and confirmed the first results,' said Dr Brian Stewart, the Hong Kong Jockey Club's head of veterinary regulation and international liaison.
'However, that is not unusual as they are very sensitive tests which often give a false positive.
'Samples have been sent to Australia for the only definitive test that exists.
'It is quite a complicated test and can only be performed in one laboratory so it may be even another week before a definitive result is available.
'These horses are cross-reacting in some way with the screening test but it could be something very minor and it does seem unusual that it would occur in three horses in a quarantine situation.
'The purpose of screening test is just to demand a closer look, so that is what they are doing now.'
The Nipah virus, which is carried by fruit bats, can be fatal to both horses and humans.