S. Singh et al., Impact of field vaccination with a Theileria annulata schizont cell culture vaccine on the epidemiology of tropical theileriosis, VET PARASIT, 101(2), 2001, pp. 91-100
Tropical theileriosis, caused by Theileria annulata, is an important tick-b
orne disease of cattle. A cell culture attenuated vaccine has been develope
d in our laboratory by long-term in vitro propagation of the schizont stage
of the parasite. A longitudinal study was conducted at selected farms hous
ing indigenous, cross-bred and exotic animals to investigate the effect of
vaccination on the epidemiology of the disease. A total of 120 animals in 4
age groups were vaccinated with the vaccine before the onset of disease se
ason. An equal number of age-matched animals were kept as controls at the s
ame sites. Animals were monitored for 14 months at monthly intervals. The 9
7.5% vaccinated animals showed a rise in antibody titres 1 month post-vacci
nation, as determined by single dilution ELISA. The 78.3% of non-vaccinated
animals became sero-positive over the period of observation. Mean antibody
titres were significantly higher in vaccinated than non-vaccinated animals
. Cross-bred animals showed higher antibody titres followed by exotic and i
ndigenous animals in both the vaccinated and non-vaccinated groups. However
, the antibody titres in animals of different ages were similar. The 36.7%
vaccinated and 64.2% non-vaccinated animals became carriers (<0.5% piroplas
ms in erythrocytes) during the observation period. Clinical cases of theile
riosis were recorded only in the non-vaccinated group suggesting that vacci
nated animals were sufficiently immune to withstand field tick challenge fo
r at least 14 months. (C) 2001 Elsevier Science B.V. All rights reserved.