This page has been archived and is no longer updated. Find out more about page archiving.

Last updated at 15:36 GMT, Monday, 26 November 2012

Tick numbers increase


26 November 2012

Scientists in the US believe the return of the white-tailed deer to many parts of the country may be responsible for spreading diseases carried by ticks to humans. An estimated 30,000 people are infected with Lyme disease every year, but other illnesses are emerging that can be deadly.


Jane O'Brian

A tick feeding on a human leg

Ticks feed off the blood of animals and humans.


Click to hear the report


Babesiosis is a malaria-like illness that causes fever and fatigue and can prove fatal. It's one of a handful of diseases carried by ticks that are increasingly infecting people in the US. And while only a few hundred cases have been reported in recent years, scientists say that number is rapidly increasing. Dr Peter Krause, a specialist at the Yale School of Public Health, says the ticks are carried by white-tailed deer that were once almost extinct in parts of the country.

"Deer are very important in the life cycle of the ticks that transmit the diseases because they provide a place for the ticks to... over winter... to reproduce and to feed. And deer have markedly increased over the past 50 years in the northeast of the United States due to reforestation."

The return of the white-tailed deer is a conservation success story in America. But their numbers are now so great that many people regard them as a nuisance and a potential health threat. Controlling their population may be one way to help stop the spread of illnesses.

"There have been a few studies showing that, with a marked reduction in number of deer, the number of ticks drops dramatically, and in these studies the number of cases of Lyme disease drops dramatically. That's one of several approaches that researchers are looking at."

Other tick-borne diseases causing concern include Deer Tick Virus and Human Granulocytic Anaplasmosis. As with Babesiosis, relatively few cases have been reported so far, but scientists say they're worried by the rising trend.


Click here to hear the vocabulary



extreme physical or mental tiredness; weariness


capable of causing death


tiny insects which feed on blood


(a species that has) died out

life cycle

stages of development during life


generate offspring


planting new trees


preserving animals or the environment for the future

a nuisance

something which is annoying

drops dramatically

falls greatly