Vectors and epidemiology of Theileria orientalis on the Northern Tablelands

Summary

Bovine theileriosis caused by the Theileria orientalis complex is a tick-borne disease of red blood cells causing a mild persistent infection with severity dependent on the infecting genotype and host exposure status.

In response to ongoing clinical cases, a cross-sectional study was conducted in the area around Armidale NSW between December 2017 and April 2018 with the aim to identify Theileria genotypes present in the region and potential vectors involved.

All three common genotypes (Buffeli, Chitose, Ikeda) were found in 73% of cattle. Ticks were only found on one of six farms surveyed and they were all Wallaby tick (Haemaphysalis bancrofti). Using PCR, T orientalis was also found in sucking lice in the project area.

Objectives

This project addressed the following questions:

• what are the likely vectors involved in the transmission of T. orientalis in this area and are they biological or mechanical vectors?
• what is the spatial and seasonal variation in abundance of biting insects and ticks on cattle properties in the study area?
• what is the current prevalence of infection with the different genotypes of T. orientalis on the northern tablelands of NSW and the proportion of the population susceptible to infection? 

Key findings

• Pasture sampling found ticks on one of six farms.
• The ticks recovered from pasture were all Haemaphysalis bancrofti.
• The three common genotypes of T orientalis were found - all three of them in 73% of the cattle.
• Bovine theileriosis is endemic in the Northern Tablelands region.

Benefits to industry

Producers in the survey area can now be better prepared when planning to introduce new cattle to the area.

Producers planning to purchase cattle from the New England area can be more aware of the potential risk of introducing a new infection, if their property has thus far been free.

MLA action

MLA continues to look for interventions to minimise losses from clinical cases of theileriosis (prevention and therapy). The outputs from this project adds to the knowledge of this disease which emerged since the turn of the century.

Future research

Future research should:

• establish the degree of anaemia suffered by infected cattle under conditions of enzootic stability
• improve understanding of the role of lice in the transmission of Theileria
• study the role of repeated mechanical transmission on possible attenuation of the parasite.

Related resources

MLA publications

• Prophylaxis and treatment of Theileria orientalis, MLA final report, 24 November 2020
• 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