The viability of Newcastle Disease Vaccine strain I-2 distributed and sold in Tanzania

Abstract

Newcastle disease (ND) is responsible for significant losses in chicken production worldwide. Vaccination against ND using live vaccines demands the use of viable and properly handled vaccines. The viability of the vaccine is, therefore, a critical component in the control of the disease. This study aimed at assessing the viability of ND vaccines available at the veterinary drug shops in selected areas of Tanzania. A total of 167 samples of live ND vaccine strain I-2 (TEMEVAC^®) vials of six different batches were randomly collected from 42 vaccine vendors in the Southern Highlands and Eastern zones in Tanzania. The samples were tested for viability through propagation into 9-days embryonated chicken eggs followed by the Haemagglutination test. The Least Square Mean (LSM) titre of infectivity of TEMEVAC^® virus was slightly higher (8.52±0.06) in the Southern Highlands zone compared to the Eastern zone (8.51±0.06) although the difference was not statistically significant (p = 0.12). There were statistically significant differences (p<0.05) in LSM infectivity titre among batches of collected TEMEVAC^® vaccine, particularly when a pairwise comparison was done between Batch_1 and Batch_3 to Batch_5. Also, there were statistically significant differences (p<0.05) in LSM infectivity titre among batches when Batch_3 was compared to Batch_6, Batch_4 compared to Batch_6, and Batch_5 compared to Batch_6. The present study revealed that the TEMEVAC^® vaccine available in veterinary drug vendors in Tanzania was viable and contained an adequate infectivity titre when used as recommended.