Modumo, Jacob, and Venter, Estelle H. (2012) Determination of the minimum protective dose for bluetongue virus serotype 2 and 8 vaccines in sheep. Journal of the South African Veterinary Association, 83 (1). pp. 1-6.

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Abstract

Recent outbreaks of bluetongue virus (BTV) serotypes 2 and 8 in many European countriesprovided an opportunity to investigate the possibility of improving the safety of the modified live vaccines administered mainly in South Africa. Modified live vaccines (MLV) released at a titre of 5 x 104 PFU/mL, raised concerns and prompted the need to determine the minimumtitre which will still be protective and also safe. The BTVserotypes 2 and 8 vaccines were produced at the following titres: 102 PFU/mL, 103 PFU/mL and 104 PFU/mL, and were injected into 24 sheep which were then monitored. Blood was collected on days 0, 3, 6, 9, 12, 15, 18, 21,25, 28 and 4 months post vaccination, for seroconversion and viraemia studies. These sheep were later challenged at 4 months post vaccination using BTV infected cell culture material,they were then observed and bled and again tested for viraemia. There was no viraemia post vaccination, however, a febrile reaction did occur and seroconversion was demonstrated at low titres for both BTV 2 and 8. Although viraemia was demonstrated post challenge, sheep vaccinated with the low titre BTV 2 vaccine showed more than a 90% protection index at a lower titre of 103 PFU/mL, compared with BTV 8 that showed a protection index above 90% at all the titres used It is recommended that for BTV 2 vaccine, sheep should be vaccinated at a titre of 103 PFU/mL and at a titre of 102 PFU/mL with BTV 8 vaccine.

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