Summary

Tick Borne Diseases (TBDs) are a major threat to the livestock industry in Zimbabwe, accounting for up to 65% of all cattle mortalities. The major TBDs of importance in Zimbabwe are Theileriosis, Anaplasmosis, Bovine Babesiosis and Erlichiosis. Zimbabwe has experienced devastating Theileriosis outbreaks during the past three years.According to the Division of Veterinary Services (DVS) more than 50 000 Theileriosis cattle deaths were reported in 2018. Many homesteads have been left without cattle, a situation which impacts negatively on many aspects of life of the rural household which rely on cattle for income, draught power and as a source of protein. The outbreaks were previously confined to known Theileria endemic areas due to limited distribution of the main vector, R appendiculatus. Change in vector tick distribution, uncontrolled cattle movement, climate change and acaricide resistance are thought to be contributing factors to the recent Theileriosis outbreaks which are now widespread in all regions of Zimbabwe.

There are several identified Theileria spp that infect cattle. The most pathogenic and economically important Theileria spp in Zimbabwe is T. parva. Other species of Bovine Theileriosis known to occur in Zimbabwe, Theileria mutans and Theileria taurotragi are of low or no pathogenicity in cattle. Though these species are considered of low or non-pathogenicity, their presence may affect the diagnosis and control of the pathogenic species .Furthermore, though T mutans has been generally considered as benign, reports indicate that some pathogenic strains do occur in the field. There is still limited information on the current circulating Theileria spp and strains in the recent Theileriosis outbreaks of Zimbabwe due to unavailability of locally adapted tests for species differentiation and further molecular characterisation of the parasites.

In Zimbabwe laboratories, giemsa staining of peripheral blood and lymph node smears is used for diagnosis of Theileriosis. PCR is only used to a lesser extent for further confirmation of the disease without species differentiation at DVS -Central Veterinary Laboratory (CVL). Though Giemsa remains useful as a cheap, rapid and easy technique for diagnosis of Theileriosis, the technique cannot differentiate and characterize Theileria spp .Furthermore detection of Theileria parasites using Giemsa staining can be difficult in low parasitaemia. Zimbabwe has relied on external sourcing of services for further characterisation of pathogens in regional or international laboratories, a situation which has been shown to be not cost effective and unsustainable. There is therefore a need to establish molecular tests that will enable diagnosis of Theileria parasites to species level and to build capacity for characterisation of theileria strains circulating. Characterisation of the pathogens provides tools important for understanding routes of transmission and spread, host susceptibility to disease, virulence of disease and postulating impact of disease and control strategies. This study will seek to improve Molecular diagnostic capacity of Theileriosis in Zimbabwe through establishment of Molecular techniques at the University of Zimbabwe followed by  use of the adapted diagnostic tools for characterisation of Theileria parasites.

Research Questions

1. Which molecular tools can be applied in the country to identify Theileria spp
2. Which molecular tools can be applied in the country to study genetic diversity of Theileria parva?
3. What is the Theileria spp causing clinical disease in outbreak areas?
4. Are we still dealing with the same species and strains of Theileria parasites as previously reported in Zimbabwe?

Is there any correlation of the identified different strains with clinical disease markers /pathophysiology and epidemiology of the disease?

Main objective

Development of molecular capacity to identify species and characterize strains of Theileria parasites circulating in Zimbabwe inorder to generate molecular epidemiological knowledge of Theileriosis for improved Tick and Tick-Borne Disease Control.

Specific objectives

1. To identify and implement  molecular tools to confirm species of Theileria parasites causing disease outbreaks in cattle
2. To use selected genotyping methods and sequencing techniques to identify Theileria species and strains that have recently caused or are causing disease outbreaks in cattle
3. To analyse the relationship between different Theileria spp or strains and clinical patterns
4. To provide science based recommendations on possible future prevention and control measures of Theileriosis in Zimbabwe.