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

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 northern 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 genetic 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 vaccine effectiveness, through a more homogeneous challenge, but the long‐term consequences are unknown.

Genetic Diversity and Sequence Polymorphism of Two Genes Encoding Theileria parva Antigens Recognized by CD8+ T Cells among Vaccinated and Unvaccinated Cattle in Malawi

“…Similarly, longitudinal studies, unlike cross-sectional studies, can provide more insight into the impact of the infection and treatment method (ITM) in the control of ECF in endemic countries, like the one done in Tanzania [35]. These studies can also help to address some concerns associated with the long-term use of the MC [35,36]. Thus, there is a need to carry out longitudinal studies in Malawi to have a complete profile and impact of the MC on the population genetics of T. parva.…”

Development of a yeast-based vaccine forTheileria parvainfection in cattle

“…Animals treated with the ITM protocol can remain life-long carriers and can potentially spread vaccine strains into areas previously free from them. It requires a continuous cold chain in liquid nitrogen, cotreatment with oxytetracycline, skilled personnel for delivery and is laborious to produce (reviewed in 50 ). Consequently, the development of a subunit vaccine with minimal risks and easier production processes is necessary.…”

Pursuing effective vaccines against cattle diseases caused by apicomplexan protozoa

“…Despite inducing a protective immune response, ITM presents several constraints, such as high cost and complexity of the production of vaccine batches and need for a cold chain for distribution. Another downside of ITM is the establishment of persistent infection in vaccinated animals and the potential risk for tick transmission, even though recent studies showed that ITM parasites do not replace the local parasite population, which, at least in part, favors the use of ITM to mitigate acute ECF [44,45]. In addition, ITM relies on the use of oxytetracycline, which raises concerns on the spread of antibiotic resistance and contamination of food and dairy products.…”