ScienceDaily (June 24, 2011) — The most common tick-borne disease in humans is Lyme borreliosis. Extensive field and laboratory tests have revealed that the Borrelia bacterium is present in a larger proportion of ticks than has been shown by earlier studies. Another finding is that migratory birds play an important role in the spreading of ticks and pathogenic agents borne by ticks.
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The researcher working on this project, Vivian Kjelland, found a strong correlation between the spread of Borrelia bacteria and birds in Norway - and discovered a decline in the hare population had little to do with Borrelia infection.
Perhaps the most interesting or surprising part of her research is this: Kjelland's doctoral thesis indicates that there is a lower incidence of the Borrelia bacterium in ticks that have sucked blood from deer and moose than in ticks collected from the ground/vegetation.
One thing to keep in mind with research in Norway as well as other countries is that the shouts of "kill all the deer" in order to stop Lyme disease may not be the best decision, as ticks will colonize other animals and take blood meals from them instead. What happens all depends on the local ecology and which host animals are available.
We can't kill all the potential hosts for ticks. Other solutions to fighting Lyme disease and related tickborne illnesses need to be found.
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CO,
ReplyDeleteI've read articles -- and particularly from Europe -- where researchers consider rodents to be more effective hosts/reservoirs of tick-borne illnesses than deer or other large mammals.
Rita A
Rita,
ReplyDeleteI think there are somewhat different competent hosts wherever you look - the point is effective hosts are a more diverse lot than has been or used to be stated in the US, where a chorus of many people in some states have shouted "kill the deer" - as if that's the solution to the spread of tickborne illness like Lyme disease. It isn't, and it isn't that simple.
In the UK, it's my understanding that hedgehogs and pheasants play a role in carrying ticks. In another European country (sorry, can't recall which at the moment), voles were a major host and mice weren't carrying many ticks. In certain states in the US, non-mice rodents may play a big role - in California it's the western squirrel.
Bb spirochetes are perfectly adaptable to this situation and their makeup provides the ability to adapt to a diverse number of host animals. Give them some blood to suck on and they are perfectly 'happy'; they don't particularly care too much on what.
I should have stated "give the ticks that are carrying them some blood to suck on and they are perfectly 'happy' - my sentence implied the spirochetes want blood to suck on when that's not their favorite domain.
ReplyDeleteMy statement as applied to ticks: "If it bleeds, it feeds."
CO,
ReplyDeleteAgreed, as I think ticks (and the spirochetes they may carry) are proving to be rather adaptive. I initially wrote "rodents and other small animals" -- with squirrels, chipmunks, voles and more in mind. I don't have the time or concentration for indepth research at the moment, but getting rid of deer in at least one area (of the U.S. if I'm not mistaken) actually increased the rates of spirochete-carrying ticks.
I'm not sure what the solution is, and I don't think our governments and public health officials have any particular strategy in mind -- other than continued denial that a problem exists (at least in Canada). That's why the focus may shift again to vaccination (if it hasn't already done so).
Rita A
CO,
ReplyDeleteI was surprised to find this related link:
http://news.illinois.edu/news/11/0621lyme_J_Rydzewski_NohraMateus-Pinilla.html
CHAMPAIGN, lll. — A new study offers a detailed look at the status of Lyme disease in Central Illinois and suggests that deer ticks and the Lyme disease bacteria they host are more adaptable to new habitats than previously appreciated.
“The deer tick will feed on a variety of mammals, birds and even reptiles,” she said. “But Borrelia burgdorferi, the bacterium that causes Lyme disease, replicates really well within white-footed mice, so white-footed mice are the main reservoir that passes that bacterium on to the immature ticks that are feeding on it.”
“Interestingly, all of the positive ticks from the prairie were from prairie voles, not the typical white-footed mouse,” Rydzewski said. There also were many more ticks per animal on the prairie voles than on the white-footed mice of the forest, she said.
This is the first study to report evidence that the prairie vole may potentially serve as a competent reservoir host for the Lyme disease bacterium, B. burgdorferi, said Nohra Mateus-Pinilla, a wildlife veterinary epidemiologist at the Illinois Natural History Survey who led the study with Rydzewski and natural resources and environmental sciences emeritus professor Richard Warner. (The Survey is a unit of the Prairie Research Institute at Illinois.)
You know, Rita, that may have been what I read. Not about a European country, as Illinois is nowhere near Europe... I am pretty sure I read it, in fact, and forgot where the voles were. But I would not be surprised at all to find out other voles in other countries are perfectly competent reservoir hosts.
ReplyDeleteCO,
ReplyDeleteHere's a small sampling of articles having to do with voles and other reservoir hosts:
Minnesota 1995: http://www.ncbi.nlm.nih.gov/pubmed/8871531
Japan 1996: http://www.ncbi.nlm.nih.gov/pubmed/8871531
Switzerland 1999: http://www.ncbi.nlm.nih.gov/pubmed/10070659
Poland 2004: http://www.sciencedirect.com/science/article/pii/S1433112804800330
Croatia 2004: http://ibmi.mf.uni-lj.si/acta-apa/acta-apa-01-4/lipozencic.html
In Europe, the infection rate of Ixodes ricinus ticks ranges from 3% to 45% (4.5% - 30.8% in Germany and Switzerland (33, 34), and 23.5% in Slovenia (35)). According to Golubić, 45% of Bb infected ticks are found in north-west Croatia (18). In the USA, white-leg mice are the main reservoir of Ixodes scapularis (36, 37). In Europe, major reservoirs of Borrelia are small rodents, wood mice, field mice, yellow-neck mice, voles and dormouses (38). Birds, deer, doe, boar, rabbit (39) and numerous domestic animals such as dog, horse, cattle, etc. are also significant reservoirs of Bb. (40-43).
2011 (chipmunks vs voles): http://aem.asm.org/cgi/content/abstract/AEM.01846-10v1
Rita, sounds like you've done a lot of homework there. Thanks for sharing this extensive list of links. In the future, could you please put a href tags around them so others can click on them rather than copy and paste? Thank you.
ReplyDeleteSo many animals have the capacity for being hosts - some better hosts than others. Unfortunately, humans are also part of this chain and suffer the consequences.
Sorry, CO, I keep forgetting about the ability to format comments.
ReplyDeleteYes, humans are now definitely part of the chain, and many don't get treated as well as their pets when it comes to Lyme disease.