Comparison of the efficacy of Chitongo Theileria Parva Sporozoites carried on ice to that carried in liquid nitrogen
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Theileria parva is a tick-transmitted protozoan parasite that causes an economically important disease of cattle called East Coast fever (ECF), in East, Central, and Southern Africa, including Zambia. Immunization against ECF by the infection and treatment method using the T. Parva chitongo strain in the Southern province has been found to be an efficient prophylactic technique to control the disease in the endemic areas. However, delivery of the vaccine to most rural areas is expensive because of the bulky transport medium which requires a four wheel drive vehicle to transport to the destination area. The aim of this study was to compare the efficacy of Theileria parva chitongo sporozoites carried on ice to that carried in liquid nitrogen in cattle. The study was done in two phases, phase one was a field trial, while phase two was an indoor trial. In the field trial, 305 cattle were vaccinated with T. parva chitongo stabilate carried in liquid nitrogen (VCLf), while another 291 cattle were vaccinated with a stabilate carried on ice (VCIf). These were aged 3 months and above with no history of immunization. His was done in 5 districts in the southern province of Zambia. The indoor trial, 17 male Friesian cattle aged between 3 months and 1 year, sourced from farms around Lusaka were used. Only cattle that tested negative for theileriosis on IFAT and microscopic examination of blood/lymph smears were included. The calves were randomly allocated to two treatment groups, one with calves vaccinated using conventional vaccine carried in liquid nitrogen (VGLi)(n1=9) and the other group vaccinated with the vaccine carried on ice (VGIi)(n2=8). Dual blood samples were aseptically collected from the jugular vein and stored in well labelled plain and EDTA tubes. Thin blood smears, PCV determination, temperature and IFAT for both field and indoor trials were done. However, blood smears, temperature and PCV for the field trial were only done before immunization. Differential white blood cell count was determined only for the indoor trial. The results of the study showed that, in the field trial, piroplasms on microscopy were detected in Choma, Kalomo, and Namwala districts before immunization with Namwala and Kalomo having the highest prevalence 16.67% (95% CI 9.96 - 23.38). The field trial also showed an overall seroprevalence on IFAT of 20% (95% CI 16.7 - 23.1) and 8.4% (95% CI 6.2 - 10.7) in the 1/40 and 1/80 dilution respectively before immunization. There was no significant difference in efficacy between T. parva chitongo stabilate carried on ice, and that carried on liquid nitrogen in both the 1/40 (p=0.450) and 1/80 (p=0.242) dilutions between group VCLf and group VCIf. In the indoor trial, the PCVs in both group VCLi and group VCIi were reducing as the trial went on, howevever, there was no significant difference in PCV (p=0.768). Differential white blood counts were done for both goups immunized wth VCLi and VCIi. The leucocyte count reduced as the study went on due to the reduction of the lymphocyte count. However, there was no significant difference between the two groups in lymphocyte counts (p=0.208). There was no significant in temperatures (p=0.0.248) between the group VCLi and group VCIi. There was also no significant difference in the probability of survival (p=0.829), the relative risk (p=0.889) and relative vaccine efficacy (95% CI -183 -59) between group VCLi and group VCIi. These results show that T. parva chitongo stabilate carried on ice has the same efficacy as that carried on liquid nitrogen. Carrying of the vaccine stabilate on ice after removal from the liquid nitroge would greatly reduce the cost of ECF immunisation and make the procedure more adoptable to rural livestock keepers.
University of Zambia
Thesis(MSc)-University of Zambia,2015
- Veterinary Medicine