researchPublished 2006
Removing deer can increase risk of tick-borne disease
A tick of the genus
Ixodes, in the nymphal
stage of its life cycle.
Image courtesy of the
Public Health Image
Library; image no. 3808.
Ticks can pass a variety of diseases from animals to humans; Lyme Disease and Tick Borne Encephalitis are two well-known examples. Ticks pick up the pathogens when they take blood meals from animal hosts. Since adult female ticks often feed on deer, removal of deer has been advocated as a tick — and disease — control strategy. However, depending on the size of the area concerned, removing deer might actually increase disease risk, as CIDD researchers point out in a 2006 paper in Ecology.
Sarah Perkins, Isabella Cattadori, Peter Hudson and collaborators in Italy have reanalyzed previously-published data to show that:
- Removing deer from large areas (over about 2.5ha) reduced the density of ticks seeking a blood meal
- But removing deer from small areas (under about 2.5ha) had the opposite effect: the number of questing ticks increased.
Tick (arrowed)
feeding on mouse.
The researchers also sampled rodents in 1ha areas from which deer had been excluded (for 16 years) and in control areas. Mice and voles in the deer exclosures had more ticks on them, on average, than did rodents outside the exclosures; tick intensities increased significantly towards the middle of the exclosures.
The researchers discuss the implications of these patterns for disease transmission. In the US and Europe, ixodid ticks are more likely to carry pathogens after feeding on rodents than after feeding on deer. Therefore, far from reducing the risk of tick-borne disease, removing deer could actually increase the prevalence of ticks carrying pathogens, particularly in small areas.
» Read the paper on the Ecology website