Contributing+Factors+-+Lyme+Disease

=Contributing Factors= As mentioned above, rodents and deer usually carry the Lyme disease pathogen before ticks transfer it to humans. So incidence of the disease peaks when humans come in closer contact with the animal hosts. This section lists the most important ways in which circumstances bridge that gap for Lyme Disease, and how it's affected the disease's spread.

Urban Expansion & Deforestation
Suburbs have had a major impact on the proliferation of Lyme disease, largely due to the environmental effects of deforestation. Following the end of World War II in 1945, easy-to-build, affordable housing became a hot commodity due to the huge influx of returning GI's. Land developers (most notably William Levitt) bought thousands of acres outside of major urban areas––places where residential communities could have jobs in the cities but sidestep the new overpopulation problem. More rural than urban, these communities were often closer to forested areas, sometimes even pushing into the forests and displacing animals living there. Suburbs cropped up across the United States, and as more develop today, the prevalence of Lyme disease follows. Near forests, the chances of mice moving under a house's foundations or deer wandering into the residential areas are much higher, and, in turn, the chances of getting caught off-guard by a tick.

Before suburban development, Lyme disease was never a significant problem. While humans and forest animals came in contact with one-another, animal density was low enough to curb tick populations. But now that forested areas are shrinking and ticks have a perfect gateway to the human population via suburban housing, the chances of coming in contact with a tick carrying Lyme disease have greatly increased.



Environmental Inflation of Animal Density
In addition to human-induced animal displacement, environmental happenstance can have a huge impact on the disease's host. The ecologist Richard Ostfeld was the first to document the direct relationship between the number of acorns in a forest and the prevalence of Lyme Disease. Trees drop acorns according to cycles synchronized by regional weather. When these cycles peak, the large number of acorns feed both mice and deer, again increasing their population density on top of the displacement caused by deforestation. The ticks flourish in such abundance of food, resulting in an enormous tick population to follow. Put simply, "acorns attract deer and mice, mice infect ticks, and infected ticks give people Lyme disease."



Animal Diversity
Mice and chipmunks carrying Lyme disease have a 90% chance of transmitting the bacteria to ticks, whereas most other animals only have a 10% chance. Unfortunately, they also happen to be some of the most adaptable to human influence. So when suburban development really hit its stride, the developed areas' diversity dropped significantly, leaving a population of hardy hosts of the disease. Instead of a range of meals for ticks to choose from, they almost always bite the disease's host, becoming vectors for the bacteria to travel from animal to human.


 * References:**