A review of recent research on Theileria parva: Implications for the infection and treatment vaccination method for control of East Coast fever

Authors: BISHOP, RICHARD - Washington State University; ODONGO, DAVID - University Of Nairobi; AHMED, JABBAR - Free University Of Berlin; MWAMUYE, MICKY - Free University Of Berlin; Fry, Lindsay; KNOWLES, DONALD - Washington State University; NANTEZA, ANNE - Makerere University; LUBEGA, GEORGE - Makerere University; GWAKISA, PAUL - Sokoine University Of Agriculture; CLAUSEN, PETER-HENNING - Free University Of Berlin; OBARA, ISAIAH - Free University Of Berlin

Submitted to: Transboundary and Emerging Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2019
Publication Date: 3/16/2020
Citation: Bishop, R.P., Odongo, D., Ahmed, J., Mwamuye, M., Fry, L.M., Knowles, D.P., Nanteza, A., Lubega, G., Gwakisa, P., Clausen, P., Obara, I. 2020. A review of recent research on Theileria parva: Implications for the infection and treatment vaccination method for control of East Coast fever. Transboundary and Emerging Diseases. 67(51):56-67. https://doi.org/10.1111/tbed.13325.
DOI: https://doi.org/10.1111/tbed.13325

Interpretive Summary: Theileria parva, an intracellular protozoan parasite, is the leading infectious cause of death of cattle in sub-Saharan Africa. Current preventive strategies are incredibly limited, and improved vaccination and treatment strategies are urgently needed to decrease the socioeconomic impact of this parasite. Currently, the most efficacious method of prevention is the infection and treatment method of immunization (ITM), in which cattle are infected with T. parva and co-treated with long-acting oxytetracycline to improve disease. Although very effective, several improvements to ITM are needed for widespread adoption in sub-Saharan Africa. This review compiles recent data on regional T. parva strain diversity and movement, efficacy of ITM in different regions, efficacy of ITM against buffalo-derived T. parva infection, and potential spread of ITM vaccine strains by ticks. This review will aid in the development of targeted research programs to improve ITM for greater adoption throughout sub-Saharan Africa.

Technical Abstract: The infection and treatment (ITM) live vaccination method for control of Theileria parva infection in cattle is increasingly being adopted, particularly in Maasai pastoralist systems. Several studies indicate positive impacts on human livelihoods. Importantly, the first detailed protocol for live vaccine production at scale has recently been published. However, quality control and delivery issues constrain vaccination sustainability and deployment. There is evidence that the distribution of T. parva is spreading from endemic areas in East Africa, North into Southern Sudan and West into Cameroon, probably as a result of anthropogenic movement of cattle. It has also recently been demonstrated that in Kenya, T. parva derived from cape buffalo can ‘breakthrough’ the immunity induced by ITM. However in Tanzania, breakthrough has not been reported in areas where cattle co-graze with buffalo. It has been confirmed that buffalo in North Uganda national parks are not infected with T. parva and R.appendiculatus appears to be absent, raising issues regarding vector distribution. Recently there have been multiple field population genetics studies using variable number tandem repeat (VNTR) sequences and sequencing of antigen genes encoding targets of CD8+ T cell responses. The VNTR markers generally reveal high levels of diversity. The antigen gene sequences present within the trivalent Muguga cocktail are relatively conserved among cattle transmissible T. parva populations. By contrast, greater genetic diversity is present in antigen genes from T. parva of buffalo origin. There is also evidence from several studies for transmission of components of stocks present within the Muguga cocktail, into field ticks and cattle following induction of a carrier state by immunization. In the short term this may increase live vaccines effectiveness, though a more homogeneous challenge, but the long term consequences are unknown.