Tick Fever in the Northern Beef Industry: Prevalence, Cost/ Benefit of Vaccination, Considerations for Genotypes, Livestock Management and Live Cattle Export

Summary

While well documented for Bos taurus cattle, the factors that influence the eventual outcome of tick fever infection are not well understood for Bos indicus cattle and their crosses. Meat and Livestock Australia was approached by key northern producers to help address this deficiency and DAQ107 was developed and carried out by QDPI. This project aims to present the information that is available and provide new information to assess the risk of losses due to tick fever in northern herds and to define the benefit to cost of tick fever vaccination.

The project established the seroprevalence of the three tick fever parasites (A marginale, B bovis and B bigemina) in cattle by cross-sectional surveys on cattle properties in north-west Queensland over a period of 3 years. B indicus and crossbred cattle from north-west Queensland were moved to a highly endemic area and monitored to estimate losses due to tick fever in a worst case scenario. The information from the surveys and natural exposure as well as expert opinion was used in a spreadsheet model to produce disease prediction and production loss information linked to discounted cashflow analysis.

Endemic stability was not observed in any of the shires surveyed for any of the 3 tick fever parasites and large numbers of cattle in the region are naive for the three tick fever parasites. The exposure trials showed that B indicus cattle are very resistant to both babesia parasites, but they and crossbred cattle are very susceptible to A marginale. Crossbred cattle are resistant to B bigemina but B bovis will cause significant mortalities in crossbreds. Increasing the B taurus content of cattle will substantially increase the risk of tick fever losses. The spreadsheet model to predict the benefit cost of vaccination has been tested using this information. The producer's attitude to risk, as well as long-term view of markets and breed structure have to be considered, but the model allows producers to assess the risk more accurately for their particular herd and therefore make more informed decisions on tick fever control.