Effects of Bluetongue Vaccination on Milk Yield in Sardinian Sheep in the District A.S.L. 1 of Sassari (Sardinia)

Effects of Bluetongue Vaccination on Milk Yield in Sardinian Sheep in the District A.S.L. 1 of Sassari (Sardinia) Francesco Sgarangella1, Caterina Suelzu1, Giuseppe Bitti1, Pietro Desini1, Manlio Fadda2, Cesare Cuccuru2 1Animal Health Service ASL Sassari, Italy 2Department of Veterinary Medicine – Sassari University, Italy Bluetongue is an arthropod‐borne viral disease to which all species of ruminants are susceptible, although sheep are most severely affected by this disease. To date, 26 distinct Blue Tongue Virus (BTV) serotypes have been identified. The first outbreak of serotype 2 bluetongue virus in Sardinia occurred in summer of 2000. More of 6200 outbreaks occurred during 2000 epidemics and 246.908 sheep died. In the following years, several outbreaks caused by different serotypes spread through Mediterranean countries were observed. To control disease a massive vector control and a vaccination program was performed in Italy. The first vaccination program started in 2002. All the ewes and goats and 90% of bovine were immunized using a modified live virus (MLV). During 2004 vaccination using serotypes 2,4 and 16 MLV vaccine caused adverse effects respectively in 25,83% and 49.22% of Sardinian and A.S.L. 1 sheep farms. Typical symptoms and lesions of the disease as well as a decrease in milk production were recorded. In consequence during the following years sheep farmers refused vaccination. In the year 2006, 2008, serotypes 1 and 8 appeared (the latter just only in A.S.L. 2). From 2010 onward more secure inactivated vaccine were exclusively used. In spite of this fact many farmers continue to adverse immunization. The aim of this work is to evaluate the presence of adverse effects on milk production due to inactivated vaccine. During the 2014 vaccination campaign a random sample of 30164 sheep from 65 flocks was investigated to evaluate the variations of pre‐post vaccination mean daily milk production/head. The sheep were inoculated twice, the second injection after 21‐28 days from the first (36 flocks were vaccinated against both BTV‐1 and BTV‐8, 29 flocks only against BTV‐1). A random sample of 12073 sheep from 25 flocks, not yet vaccinated, has been chosen as a control during the same period of vaccination program. Data were collected in a database and submitted to statistical analysis. After the first inoculation the mean milk production increased in both groups, vaccinated and unvaccinated (+1.18÷+1.86%), while same parameter decreased in both groups after the second vaccination (‐5.86÷‐2.03%) Statistical analysis shows not significant variations between groups. There were only small differences of milk production between vaccinated and control groups after first and second injection period. The vaccinated group appears to shows a moderate tendency to more pronounced variations in milk production of not relevant statistical significance. It most likely depends on the transitory disturbance induced on the flock by the vaccination procedures rather than the effect of the inactivated vaccine employed. The decrease of milk yield after the second vaccination in both groups appears associated to the seasonal decrease of lactation curve in sardinian sheep breed.