Predicting tick populations through ecology

By entering virtually any vegetation in parts of North America, one may be tempted to catch ticks that jump on exposed flesh. But at other times, a walk in the woods can produce no parasites.

Ecological conditions can predict tick populations, as well as pathogens that they may harbor, such as Lyme disease, anaplasmosis and babesiosis, according to a recently published study. journal Ecology .

The prediction model is based on 19-year detailed observations on parcels of land at the Cary Institute of Ecosystem Studies in the State of New York.

"This is the first time that we have synthesized the effects of ascending and descending control, as well as climate, on the abundance of infected ticks," said Richard Ostfeld, lead author of the 39, Institute Cary. "The length of this dataset, as well as the size of the sample of collected ticks and small mammals captured, are unprecedented in this context."

Observations began in the 1990s and continued until recently Six large woodlots in southeastern New York State were studied, trapping small mammals occurring every few weeks in May. to November

The catch was mbadive: more than 78 000 catches during the period studied, the catch being mice and chipmunks.The number of these creatures was a cross-reference with relative accounts of acorns and feeding sources.

Also studied: ticks, and many of them. Dredging tissues were used to remove leeches in 450-meter transects. Total catch: 11,115 nymphs and 147,238 larvae. According to the study, some rodents can harbor dozens of ticks and be perfect reservoirs of pathogens.

Predators were also counted using black diode traps at dozens of sites in Dutchess County for two periods (2012 and 2013)

The dynamics they found established that there is a feedback loop in the ecosystem that determines tick numbers, and the frequency of pathogens such as Borrelia burgdorferi . the following year, then a marked increase in the tick of the infected pupa the following year

The diversity of predators is essential to keep tick infection rates at a low level. For example, locations dominated by coyotes alone showed a high prevalence of infected ticks. But those with a number of foxes, bobcats, fishermen, raccoons and opossums have lower pathogens observed (about 7,000 nymphs were tested for germs during the year). study). The opossum is a particularly effective consumer of ticks, according to the newspaper.

The hot, dry climate, especially in spring and winter, reduces tick populations and tick diseases. Because ticks spend most of their time on the ground, they can easily dry out with the right combination of weather conditions.

A disaster scenario would be an abundant crop of acorns, followed by a relative shortage of food. source. The rodent population would thus sting and then crush. In the spring following this accident, there would be a lot of infected ticks, and less rodents to feast on. Ticks would then look for other hosts such as people.

Overall, Ostfeld and the team thought that they could find a way to have a warning system so that people near the areas at times crucial know to be on the lookout for leeches "Understanding disease systems can help us refine predictions of when and where the risk will be particularly high," Ostfeld said. "The dissemination of alerts based on these specific predictions, rather than messages of general interest, should, hopefully, counter the" annoying fatigue "and encourage people to take action. more proactive self-protection. "