Foot and mouth disease (FMD) is a highly infectious and economically devastating disease of livestock. The vaccination is used for prevention of FMDV infection, while the evaluation of FMDV vaccine is mandatory to approve the efficacy of the vaccine but it consumed time and animals. This work, aimed to find the correlation between serum neutralization test (SNT) and challenge test by using FMDV serotype O (O/EGY/4/2012). Seventeen calves (6 months of age) were tested by SNT to be confirming their freedom from antibodies against serotype O. The calves were allotted into four groups. The first group (5 calves) was inoculated with field dose (1X) of a local inactivated FMDV vaccine (contain O/EGY/4/2012), the 2nd group (5 calves) was inoculated with half dose (1/2 X) of the same vaccine and the 3rd group (5 calves) was inoculated with one quarter dose (1/4 X) of the same previous vaccine, while the 4th group (2 calves) was kept as control. The sera were collected from group1, 2 and 3 at the 0, 14 and 28th day post vaccination. SNT was carried out against FMDV serotype O and the challenge test was carried out by inoculating all animals with 0.3 ml 104 BID50 (bovine infectious doses) of virulent FMDV type O. It was found that the SNT result after 28 days post vaccination for group1, group2 and group3 were 2.28, 1.74 and 0.96 (log10) TCID50/ml respectively while the protection percentage were 100%, 80% and 60% respectively. The recorded results reflect the correlation between serum neutralizing antibody titre and protective percentage in vaccinated calves which could be useful as alternative to challenge test in FMDV vaccine evaluation to minimize the cost of experimental animals use and suggested hazard.
Key words: Foot and mouth disease, FMDV evaluation, serotypes O, SNT and challenge test.
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