Surveillance and Risk Analysis for Bovine Babesiosis in England and Wales to Inform Disease Distribution

SIMPLE SUMMARY: The distribution of ticks is expanding across Europe and the incidence of human and animal tick-borne disease is increasing. This trend is set to continue due to predicted changes in the climate and land use, which alter the interlinked environmental factors required for the feeding and breeding activities of the tick. Babesia divergens is a tick-borne piroplasm which poses a major disease threat to cattle in Great Britain and can also cause significant illness in humans. Surveillance of B. divergens infection in cattle is currently limited, rendering disease monitoring and mitigation strategies against evolving environmental conditions impossible. This surveillance project collected spatial and temporal data on B. divergens infection in British cattle and analysed the risk factors for disease. B. divergens was detected in 47.4% of submitted samples. The infections occurred throughout the grazing season. The majority of the cases were diagnosed in South West England; however, other geographical risk areas were identified. These data support future assessment of disease dynamics in the face of evolving environmental conditions. No significant herd- or animal-level disease risk factors were identified. The PCR methods used in this case offer improvements in identifying Babesia at species level and offer compatibility with current human diagnostic guidelines. ABSTRACT: Babesia divergens is a zoonotic piroplasm that infects both cattle and humans in Europe. Disease transmission occurs through Ixodes ricinus tick bites, a species that is increasing in abundance and distribution across Europe in response to climate and land-use changes. Developments in agri-environment policy and changing consumer demands may also have unintended consequences on tick-borne disease rates. Currently, B. divergens surveillance in British cattle is limited, rendering temporal trend analysis and the detection of potential zoonotic hotspots impossible. The objective of this study was to assess syndromic surveillance as a means of determining babesiosis distribution in British cattle, and to evaluate the intrinsic disease risk factors in order to respond to disease threats posed by changing environments. Samples from 95 clinically affected cattle on 70 unique holdings were screened for Babesia spp., using established blood smear examination techniques and a B. divergens-specific PCR method, between April and December 2021. B. divergens was detected in 45/95 animals (47.4%), with PCR offering the advantage of identification at species level. Infection with Anaplasma phagocytophilum was detected in 19/95 animals (20%). Co-infection was detected in five animals. The cases were recorded across multiple geographic regions and throughout the sampling period. Univariate logistic regression analysis failed to identify any statistically significant risk factors for B. divergens presence. This study demonstrates that bovine babesiosis is geographically widespread throughout England and Wales, placing a large proportion of the cattle population at risk of infection, with the potential for zoonotic transmission to humans.