TEO
Well-known member
Since Lyme Disease is an often popular, and certainly relevant topic here, I thought people would be interested in this article: http://www.boston.com/lifestyle/hea...g_to_check_the_spread_of_lyme_disease/?page=1.
Lyme Disease: the Deer-Lyme Disconnect?
- Thread starter TEO
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DougPaul
Well-known member
Attacking a single vector in a situation where there are multiple parallel vectors seems unlikely to succeed...
I have read of tests using permethrin treated cotton being set out for mice to use as nesting material achieving a significant degree of success. (The author seemed unaware of this...) However permethrin is toxic to cats and many aquatic organisms.
Doug
I have read of tests using permethrin treated cotton being set out for mice to use as nesting material achieving a significant degree of success. (The author seemed unaware of this...) However permethrin is toxic to cats and many aquatic organisms.
Doug
una_dogger
Well-known member
Decrease habitat fragmentation = increase small mammal diversity= decrease Host pool for bacteria
The Answer lies within the ecology of Lyme Disease
The Answer lies within the ecology of Lyme Disease
DougPaul
Well-known member
una_dogger
Well-known member
Not really following that line of thinking, Doug? Do you mean deer predators?
Deer aren't the sole problem, they are the distribution vector, and studies have shown that decreasing their numbers has little effect on the reservoir of Borrelia burgdorferi in the system (see below). A larger problem is that the overall small mammal pool is narrowed significantly in the past 25 years. Habitat fragmentation, the rabies epidemic in the late 80s that wiped out the racoons and many possums, the stress on Oaks that lead to increase acorn masting (and increased white footed mouse populations), all contributors to creating an ecosystem that favors Borrelia burgdorferi. In normal, diverse ecosystems crowding and competition would keep populations of all mammals lower; thereby diluting the reservoir bacteria in the White footed mouse pool. Decrease habitat, decrease biodiversity, increase food for white footed mouse, increase population of mouse, increase food for ticks, and provide a vector to distribute ticks between habitat patches (deer) and you have a very unbalanced ecosystem that favors the disease and its transmission. In short, hello suburban Northeastern America, you are the perfect home. The bacteria was first isolated almost a hundred years ago, as was the disease...the rise in the disease is really pretty new.
From:
http://www.americanscientist.org/issues/feature/the-ecology-of-lyme-disease-risk/6
Perhaps most interesting, the model suggested that infection rates of juvenile ticks, and hence the risk of Lyme disease, are lower when the host community is highly diverse than when only a few species of hosts are available. Because only one species of host, the white-footed mouse, is a highly competent reservoir for B. burgdorferi, any increase in the species diversity of hosts will dilute the effect of mice by offering ticks alternative, reservoir-incompetent hosts from which to feed. This result is consistent with empirical results obtained from the southeastern and western United States by Robert Lane of the University of California at Berkeley and his colleagues. In these areas the host community includes several species of reservoir-incompetent rodents and lizards, and the infection rate of Ixodes ticks is much lower than in the northeastern and north-central United States. A key implication of the model is that maintaining high species diversity in vertebrate communities, for instance by maintaining high habitat diversity or high predator density, may reduce the risk of Lyme disease.
Recently Josh Van Buskirk and I extended the simulation model to a landscape consisting of several different types of habitat patches among which both rodent and deer hosts were able to move. We arranged these habitat patches according to our understanding of the nature of semirural and suburban landscapes in Lyme-disease-endemic areas of the northeastern United States. In these areas, patches are relatively small compared to the dispersal capabilities of mammals, and some habitat types constitute "source patches," as they are net exporters of emigrants, whereas others constitute "sink patches" because they are net importers of immigrants.
One key result of the model was that considerable densities of highly infected ticks can be maintained in “sink” habitats even when the average density of rodent hosts is low. The density of infected ticks in any particular habitat type is a consequence of the proximity of other patch types and the dispersal patterns of rodent and deer hosts, which our empirical studies demonstrate are affected by acorn availability. Thus, our model and field data indicate that the local risk of Lyme disease cannot be predicted simply by focusing on conditions within the local habitat. Rather, land-use policy makers must also consider the dynamics of mice and ticks in the surrounding landscape.
Deer aren't the sole problem, they are the distribution vector, and studies have shown that decreasing their numbers has little effect on the reservoir of Borrelia burgdorferi in the system (see below). A larger problem is that the overall small mammal pool is narrowed significantly in the past 25 years. Habitat fragmentation, the rabies epidemic in the late 80s that wiped out the racoons and many possums, the stress on Oaks that lead to increase acorn masting (and increased white footed mouse populations), all contributors to creating an ecosystem that favors Borrelia burgdorferi. In normal, diverse ecosystems crowding and competition would keep populations of all mammals lower; thereby diluting the reservoir bacteria in the White footed mouse pool. Decrease habitat, decrease biodiversity, increase food for white footed mouse, increase population of mouse, increase food for ticks, and provide a vector to distribute ticks between habitat patches (deer) and you have a very unbalanced ecosystem that favors the disease and its transmission. In short, hello suburban Northeastern America, you are the perfect home. The bacteria was first isolated almost a hundred years ago, as was the disease...the rise in the disease is really pretty new.
From:
http://www.americanscientist.org/issues/feature/the-ecology-of-lyme-disease-risk/6
Perhaps most interesting, the model suggested that infection rates of juvenile ticks, and hence the risk of Lyme disease, are lower when the host community is highly diverse than when only a few species of hosts are available. Because only one species of host, the white-footed mouse, is a highly competent reservoir for B. burgdorferi, any increase in the species diversity of hosts will dilute the effect of mice by offering ticks alternative, reservoir-incompetent hosts from which to feed. This result is consistent with empirical results obtained from the southeastern and western United States by Robert Lane of the University of California at Berkeley and his colleagues. In these areas the host community includes several species of reservoir-incompetent rodents and lizards, and the infection rate of Ixodes ticks is much lower than in the northeastern and north-central United States. A key implication of the model is that maintaining high species diversity in vertebrate communities, for instance by maintaining high habitat diversity or high predator density, may reduce the risk of Lyme disease.
Recently Josh Van Buskirk and I extended the simulation model to a landscape consisting of several different types of habitat patches among which both rodent and deer hosts were able to move. We arranged these habitat patches according to our understanding of the nature of semirural and suburban landscapes in Lyme-disease-endemic areas of the northeastern United States. In these areas, patches are relatively small compared to the dispersal capabilities of mammals, and some habitat types constitute "source patches," as they are net exporters of emigrants, whereas others constitute "sink patches" because they are net importers of immigrants.
One key result of the model was that considerable densities of highly infected ticks can be maintained in “sink” habitats even when the average density of rodent hosts is low. The density of infected ticks in any particular habitat type is a consequence of the proximity of other patch types and the dispersal patterns of rodent and deer hosts, which our empirical studies demonstrate are affected by acorn availability. Thus, our model and field data indicate that the local risk of Lyme disease cannot be predicted simply by focusing on conditions within the local habitat. Rather, land-use policy makers must also consider the dynamics of mice and ticks in the surrounding landscape.
Raven
Well-known member
Another great example of how maintaing a diverse and healthy ecosystem is vitally important for humans in spite of the fact that as a society we seem to believe we are not part of it. Topple the ecological "house of cards" holding us up and we will most likely take a long fall with it.
Una - Thanks for the great detail. This fills in alot of "gaps" in my understanding of the spread of Lyme Disease.
And I have to say, I really appreciate the fact that you supported this with a peer-reviewed, respected journal from the scientific community and not with a 10-second google search and wikipedia reference...which holds about as much water as a shaky second opinion.
Thanks for taking the time.
una_dogger
Well-known member
I worked at the Institute of Ecosystem Studies for 7.5 years (forest health/climate change), though not for Dr Ostfeld, I was very much interested in his approach to studying the ecological factors that were driving the increase in Lyme Disease Risk -- and he's also a great guy to talk to. Epidemiological Ecology is a REALLY interesting field -- and Lyme Disease Risk is one of the most promising drivers of land use policy I think there has ever been. Lets hope it helps change the way we develop our land !
