Horse populations are severely underestimated in a region at risk of Hendra virus spillover

OBJECTIVE

To identify the size and distribution of the horse population in the Northern Rivers Region of NSW, including changes from 2007 to 2021, to better understand populations at risk of Hendra virus transmission.

METHODS

Census data from the 2007 Equine Influenza (EI) outbreak were compared with data collected annually by New South Wales Local Land Services (LLS) (2011-2021), and with field observations via road line transects (2021).

RESULTS

The horse populations reported to LLS in 2011 (3000 horses; 0.77 horses/km2) was 145% larger than that reported during the EI outbreak in 2007 (1225 horses; 0.32 horses/km2). This was inconsistent with the 6% increase in horses recorded from 2011 to 2020 within the longitudinal LLS dataset. Linear modelling suggested the true horse population of this region in 2007 was at least double that reported at the time. Distance sampling in 2021 estimated the region's population at 10,185 horses (3.89 per km2; 95% CI = 4854-21,372). Field sampling and modelling identified higher horse densities in rural cropland, with the percentage of conservation land, modified grazing, and rural residential land identified as the best predictors of horse densities.

CONCLUSIONS

Data from the 2007 EI outbreak no longer correlates to the current horse population in size or distribution and was likely not a true representation at the time. Current LLS data also likely underestimates horse populations. Ongoing efforts to further quantify and map horse populations in Australia are important for estimating and managing the risk of equine zoonoses.

Multimodal approach to screening for ovarian cancer

1010 postmenopausal women were recruited for an ovarian cancer screening programme incorporating serum CA-125 measurement and vaginal examination as initial tests and real-time ultrasonography as a secondary procedure in selected cases. The normal range for serum CA-125 in postmenopausal women was established. The specificity for ovarian cancer of serum CA-125 measurement and vaginal examination were 97.0% and 97.3%, respectively. The combinations of serum CA-125 measurement with ultrasound and vaginal examination with ultrasound achieved specificities of 99.8% and 99.0%, respectively. 100% specificity was achieved by serum CA-125 measurement with vaginal examination and by the combination of all three tests. The findings indicate that no individual screening test has acceptable specificity for ovarian cancer in postmenopausal women. However, the combination of CA-125 measurement with ultrasound did achieve acceptable specificity and offers the most hope of a specific and sensitive method for early detection.