In eastern, central and southern Africa, improvement in livestock production efficiency has been severely constrained by several tick-borne diseases of cattle. The most important of these diseases is East Coast fever (ECF), caused by the protozoan parasite Theileria parva. The losses in the form of high morbidity and mortality, especially among improved (exotic or cross-bred) cattle, are particularly important in the case of the dairy industry. Milk is a highly valued commodity that is in short supply throughout the region. In addition to being an important source of dietary protein and minerals, milk also provides cash income to dairy farmers to purchase essential inputs. In many communities, it is the women who have responsibility for the management of the dairy enterprises.
The prevailing strategy for control of ECF is based on the use of acaricides to control the tick vector, Rhipicephalus appendiculatus. This method is limited by the high cost of acaricides, increasing problem of resistance to acaricides in some tick species, and negative environmental impact. An immunization approach known as the Infection and Treatment Method (ITM), based on the inoculation of cattle with a potentially lethal dose of cryopreserved Theileria parasites and simultaneously treating them with a long-acting antibiotic, has been adopted on a limited scale, but has some drawbacks. Scientists at the International Livestock Research Institute (ILRI) have developed a prototype vaccine for ECF that is based on the major surface protein of the infective sporozoite stage of the parasite. Immunization of boran (Bos indicus) cattle with a recombinant of the p67 protein, formulated in adjuvant, has consistently reduced the incidence of severe ECF in 50% of vaccinated animals, in both laboratory and field trials. The vaccine is easily administered and protection is not strain specific. A strict cold chain is not required for its deployment.
Grant purpose The objective was to evaluate the impact of a new recombinant vaccine
against ECF in smallholder dairy systems of eastern Africa.
Particular objectives were to:
- confirm the efficiency of the p67 recombinant vaccine in smallholder dairy units in different agro-ecological zones and countries of eastern Africa;
- evaluate mechanisms for the optimal delivery, adoption and impact of the p67 vaccine;
- determine the impact of the vaccine in smallholder dairy systems on a series of livestock productivity and economics indicators; and
- evaluate the socio-economic benefits to livestock breeders and consumers of livestock products of reduced ECF risk.
Development of a comprehensive design for the study
A comprehensive design was developed to ensure the inclusions of all indicators relevant to the evaluation of vaccine impact on the range of end-users and project beneficiaries.
Data analysis, impact assessment and study of vaccine delivery mechanisms
Data collected from productivity and socio-economic components was assembled and analysed; an impact assessment study on livestock productivity and socio-economic indicators was carried out, including studies of (i) the demand by smallholder farmers for genetically improved dairy cattle, (ii) the demand for forage and feed, and (iii) the link between changes in disease-control expenditure and milk production with enhanced human welfare, income, employment and family education opportunities. A comparative study on appropriate vaccine delivery mechanisms was also implemented.
- The vaccine being tested (p67) proved less effective than expected as a standalone product and although it was evaluated in controlled field trials at the Kenya coast and in the highlands, it was not possible to evaluate it in smallholder dairy systems as planned. Consequently, ILRI’s research on a recombinant vaccine is now focused on stimulating cell-mediated immunity using a schizont-based approach. Excellent external collaborations have been established, model vaccine delivery systems in the host have been validated, and the first set of candidate antigens could be available for testing shortly. The eight-year programme for this research is well on target.
- When it became clear that the p67 vaccine could not be evaluated as a deliverable ECF vaccine, the original project objectives and workplan were modified to pave the way for future vaccine application and predict optimal delivery and adoption pathways, and the impact of the vaccine in smallholder farming systems. In these respects, the project has made excellent progress, and a number of significant findings emerged.
- There would be a ready willingness to pay for an ECF vaccine amongst smallholder farmers, which might translate into high demand. An effective vaccine would have a major impact on poverty reduction.
- With the expansion in zero-grazing practices and the recent fall in milk prices, the demand for vaccine is declining in some areas of the smallholder dairy sector. However, smallholder dairying is also expanding to marginal areas where disease risk and demand remain high. Furthermore, there is a rapidly increasing need and demand for vaccine amongst some pastoralist and agro-pastoralist farmers. The future focus for vaccine should therefore be expanded to include these sectors. The greatest potential for impact on poverty also lies here.
- Farmers regard safety and efficacy of vaccine as more important than cost.
- The use of ECF control technologies is influenced by farmers’ perceptions of the risk of the disease, which does not always correspond to the biological risk in some production systems.
- Delivery pathways need improving to ensure reliable vaccine availability and supply. Whereas the use of para-vets and animal health assistants for vaccine administration could be adopted more widely in the market-oriented smallholder dairy areas, this has been hampered by policy regulations. Delivery in agropastoral (and possibly pastoral) areas requires a different approach.
- Current physical cold-chain networks for both liquid-nitrogen-stored and refrigerated products appear adequate to handle an expanded ITM delivery, and future delivery of sub-unit ECF vaccines. The most significant constraints to effective delivery of ITM are the need for continuous product quality regulation throughout the cold chain, and liability issues
- Revised strategies need to be developed for the control of ticks and other tick-borne diseases following successful control of ECF, so that farmers can be given appropriate objective advice.
- Models for predicting risk of ECF and the impact of vaccination, particularly through use of Geographical Information System (GIS) technology, will soon be completed and provide valuable tools for underpinning policy decisions on application of vaccine in different agro-ecological and socio-economic situations.
- Theoretical predictions of risk and impact need to be validated through application of models in actual vaccine situations. In this respect, ITM is being widely applied in Tanzania (and to lesser extent in Uganda and Kenya), with great effect. ITM should now form the focus of vaccine delivery and impact studies until an improved vaccine becomes available.
- With the prospect of increased cattle survival within pastoralist systems following the success of ECF vaccination, consideration needs to be given to conducting environmental impact studies pre- and post-vaccination, and to reviewing opportunities for increasing cattle offtake through appropriate marketing strategies.
