Prophylaxis and treatment of Theileria orientalis

Summary

The internal parasite Theileria orientalis has rapidly spread across south-eastern Australia, negatively impacting the health of local cattle since 2006. The industry would benefit greatly from measures to reduce the impact of the initial infection either by means to control the vector (ticks) or the early stages of the start of infection.

This project aimed to confirm the vector capability and transmission of Theileria orientalis ikeda by the tick Haemaphysalis longicornis, plus trials of two interventions to reduce infection in cattle.

This study is the first confirmation that the carrier state persisting in cattle that have recovered from the initial parasitosis from Theileria orientalis, establishes some type of resistance to subsequent, seasonal tick challenge. This result would require confirmation in the field to determine dose rates and confirm efficacy and reliability.

Objectives

This research project aimed to clarify:

• how capable the tick Haemaphysalis longicornis is of transmitting Theileria orientalis ikeda
• whether chemotherapy would remove the infection and reduce chances of relapse and transmission to ticks
• whether artificial infection with piroplasms could protect against sporozoite challenge
• whether immunisation (either via natural routes or artificially) could protect against sporozoite challenge with homologous or heterologous genotypes.

Key findings

• Results from this project confirm Haemaphysalis longicornis (Bush tick) as a vector for Theileria orientalis ikeda, but also revealed the role played by Haemaphysalis bancrofti and Haemaphysalis humerosa (the Wallaby and Bandicoot ticks).
• While buparvaquone significantly reduced the number of parasites in the bloodstream over the first 2 weeks after administration, T orientalis ikeda DNA was still detectable two months later, which means it was not completely eliminated.
• This project also confirmed speculation that carrier cattle possess some premunity (infection immunity) that protects against the severity of repeated, seasonal tick challenges.

Benefits to industry

NSW Department of Primary Industries have estimated that Theileria orientalis costs an average of $59,000 for dairy producers and $11,600 for beef producers, which equates to AUD $131/head for dairy cattle and AUD $67/head for beef cattle for businesses impacted by the parasite; all costing around $20 million pa nationally. These losses are made up of lost live weight and mortalities.

Therefore, best practice information that can reduce the effects of Theileria orientalis infection will drastically improve animal welfare and the productivity and profitably of the Australian beef industry.

MLA action

The greatest need is for prevention and treatment against Theileria orientalis, both of which require pharmaceutical industry engagement.

Future research

• The seasonal distribution of Haemaphysalis ticks should be more definitively mapped to determine danger zones for cattle movements.
• Dose response trials (for marketing) and field trials (to determine efficacy and validation) would be needed to mitigate failure.
• Field studies would also determine any mitigation against production loss.

Related resources

MLA publications

• Transmission of Theileria orientalis in cattle, MLA final report, 25 August 2016
• Bovine theileriosis molecular diagnosis and strain analysis, MLA final report, 16 March 2016
• Buparvaquone tissue residue study, MLA final report, 04 October 2013
• Bovine Theileriosis - distribution and significance of major piroplasm surface protein (MPSP) types, MLA final report, 18 January 2012
• Theileria orientalis vaccine development potential, MLA final report, 18 January 2012
• Assess the efficacy of Buparvaquone for the treatment of bovine theileriosis, MLA final report, 08 November 2011