Environmental variables influencing tick anaphylaxis presentations: An observational study

Ixodes holocyclus, the predominant tick species on the eastern coast of Australia, is responsible for the increasing incidence of tick anaphylaxis (TA) presentations. While ticks thrive under warm and humid conditions, the influence of environmental conditions on TA incidence remains unclear.

This study aimed to correlate environmental variables with TA presentations in New South Wales (NSW), Australia, to predict tick seasons and forewarn residents of tick-endemic regions.

Monthly temperature, rainfall, dewpoint, and fire extent data were collected from open-access government resources for Northern and Southern Coastal NSW, and Greater Sydney regions. These were compared with tick bite locations and dates from 278 TA patients from 2005 to 2022, using Pearson's correlation.

In Greater Sydney, TA cases were weakly correlated with rainfall (r = -0.15), temperature (r = 0.26), and dewpoint (9 am: r = -0.22; 3 pm: r = -0.22), and a strong negative correlation with percentage area burned (r = -0.94). Northern and Southern coastal NSW TA cases exhibited similarly weak correlations with rainfall, temperature, dewpoint, and percentage area burned.

Larger bushfires may reduce TA presentations through tick habitat destruction. However, the role of weather variables remains inconclusive, highlighting the need for further research to better understand tick ecosystems, which may aid public health initiatives for tick awareness.