Impact of field vaccination with a Theileria annulata schizont cell culture vaccine on the epidemiology of tropical theileriosis.
Tropical theileriosis, caused by Theileria annulata, is an important tick-borne disease of cattle. A cell culture attenuated vaccine has been developed in our laboratory by long-term in vitro propagation of the schizont stage of the parasite. A longitudinal study was conducted at selected farms housing 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 season. An equal number of age-matched animals were kept as controls at the same sites. Animals were monitored for 14 months at monthly intervals. The 97.5% vaccinated animals showed a rise in antibody titres 1 month post-vaccination, 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 indigenous 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% piroplasms in erythrocytes) during the observation period. Clinical cases of theileriosis were recorded only in the non-vaccinated group suggesting that vaccinated animals were sufficiently immune to withstand field tick challenge for at least 14 months.
Singh
S
S
Department of Veterinary Epidemiology and Preventive Medicine, College of Veterinary Sciences, Chaudhary Charan Singh Haryana Agricultural University, Hisar 125004, India.
Khatri
N
N
Manuja
A
A
Sharma
R D
RD
Malhotra
D V
DV
Nichani
A K
AK
D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D002417:Cattle; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D007194:India / Q000453:epidemiology; D008137:Longitudinal Studies; D016052:Protozoan Vaccines / Q000276:immunology; D016036:Seroepidemiologic Studies; D016796:Theileria annulata / Q000276:immunology*; D013801:Theileriasis / Q000453:epidemiology / Q000517:prevention & control*; D014611:Vaccination / Q000662:veterinary; D014613:Vaccines, Attenuated / Q000276:immunology
D000913:Antibodies, Protozoan; D016052:Protozoan Vaccines; D014613:Vaccines, Attenuated