Evaluation of variability in antibody response induced by vaccination against Peste des petits ruminants (PPR) in Malpura and Avikalin sheep

- Vaccine response to PPRV vaccine in sheep is highly variable and influenced by environmental (breed, cohort, season and age at vaccination) and genetic components (additive variance).
- Higher Pre-vaccination titre is indicative of maternal antibody titre in lambs.
- Moderate estimate of heritability for vaccine response augurs selection of Avikalin sheep for higher response. Malpura sheep had meagre additive variance for vaccine response.

Amongst several trans-boundary diseases of small ruminants in India, Peste des petits ruminants (PPR) is a devastating disease due to its spread and economic importance. The main strategy for prevention of this disease is the vaccination with attenuated whole virus vaccine. Present study was carried out to identify the sources of variation and also to unravel the genetic variance in the PPR virus (PPR) vaccine elicited immune response in 231 Avikalin and 398 Malpura sheep lambs maintained at organized institute flocks in the semi-arid region of India. Average age at vaccination was 108.5 days. Sera were tested by competitive ELISA (C-ELISA), an attenuated PPR (Sungri) was used as the coating antigen. Results revealed significant variability for response to vaccination. Per cent inhibition (PI) values at 0 day of vaccination (0DPrV) was 33.9% and 29.8% in Avikalin and Malpura lambs, respectively. At 28 days post vaccination (28DPV) PI was 62.7% in Avikalin and 58.7% in Malpura lambs. On 28DPV, the protective titre (PI > 50%) was shown by 82.4% Avikalin lambs and 76.2% Malpura lambs. Among environmental determinants, breed, cohort, season and age at vaccination proved to be significant sources of variation (P < 0.05). Factors determining the better odds of protection need to be exploited properly to assure protection. The estimate of heritability (h2 ± SE) at 28DPV was 0.02 ± 0.12 in Malpura sheep, however it was 0.54 ± 0.28 in Avikalin sheep.