Deer and Lyme Disease, Research on the Relationship
This page presents a collection of the latest research on the deer-Lyme disease relationship.  Lyme disease is named for the rural Connecticut town where it was first identified in 1975. 

Ecology of Infection Disease:  A Special Report (On Lyme Disease) National Science Foundation
... Areas of patchy woods, which are very common in cities and suburban and rural areas, may have higher populations of Lyme-disease carrying ticks than forest fragments, which generally have fewer species than continuous habitat. This is because some species thrive in smaller places.  White-footed mice, for example, are more abundant in forest fragments in some parts of the country, likely because fewer predators and competitors remain there. These mice are particularly abundant in patches smaller than about five acres, which could spell trouble for people living nearby: the mice are the main carriers of Lyme disease-causing bacteria ...
     "Our results suggest that efforts to reduce the risk of Lyme disease should be directed toward decreasing fragmentation of deciduous forests of the northeastern United States, particularly in areas with a high incidence of Lyme disease ...The creation of forest fragments smaller than five acres should especially be avoided."

Where foxes thrive, Lyme disease doesn't September 10, 2012 New York, Poughkeepsie Journal
... Taal Levi has studied environments from Brazil to Alaska ... His statistical analysis showed little correlation between the prevalence of deer and the incidence of Lyme. If that were the case, Levi said, “then why is Lyme disease so relatively rare in Western New York when deer are more abundant than in places here that have lots of Lyme disease?” ...Levi used statistical data to show that as fox populations went down, Lyme went up. The statistical connection between Lyme and other species wasn’t as consistent. The study was published in the Proceedings of the National Academy of Sciences in June... 

Effects of abundant white-tailed deer on vegetation, animals AL Shelton, JA Henning, P Schultz, K Clay Forest Ecology and Management 2014
... we simultaneously examine effects of excluding white-tailed deer on responses of woody and herbaceous vegetation, terrestrial and subterranean animals, mycorrhizal fungi, and soil characteristics. This study was conducted in a forest preserve with high deer densities in the central hardwoods region of the Midwestern US, using a series of 
replicated deer exclosures (15  15 m) and adjacent unfenced controls that ranged in age from two to  seven years... We also found differences in terrestrial animals with higher densities of white-footed mice (Peromyscus leucopus) and dog ticks (Dermacentor variabilis) inside deer exclosures. However, there were no differences in salamanders or earthworms....

Co-Infections Possible from Tick Bites June 24, 2014 Massachusetts,  Boston 
... New to this study, said co-author Felicia Keesing, is that the small mammals the ticks feed on also carry multiple infections... Ticks resort to feeding exclusively on small mammals when there aren’t larger animals, like raccoons or deer, to feast upon. ... scientists at Bard College, Sarah Lawrence College and the Cary Institute of Ecosystem Studies...

Have deer gotten a false rap for Lyme disease? August 3, 2012 Earthwise [includes pictures and podcast]
... While deer host lots of ticks, so do other vertebrates, including raccoons, skunks, and white-footed mice. Eliminate deer, and ticks will feed on other hosts. Also, while deer don’t transmit the Lyme bacterium to ticks—the smaller mammals do. Rick Ostfeld, a senior scientist at the Cary Institute of Ecosystem Studies, has written a book on Lyme disease ecology… 

... "Homeowners trying to kill ticks in their own yards need to target the rodents that carry the Lyme disease bacteria," says the CDC's Division of Vector-Borne Diseases Director Lyle Petersen in its recent report.  That's how Tick Tubes target deer ticks. Developed at the Harvard School of Public Health, Damminix relies on the natural nesting instincts of rodents that carry Lyme disease and is the only rodent-targeting deer tick control solution on the market today.  "Historically, people focused on deer as the culprit, but it's mice that spread Lyme disease," says Damminix Company Director Ariana Ganak. "When deer ticks hatch, they are disease free. Immature ticks feed on mice twice a year, and when they bite the infected mouse they become carriers of Lyme and pass it on to the unsuspecting general public. At long last people are becoming aware that mice are the real cause of this public health epidemic ...

     Spritzing deer with tick insecticide is one way to fight Lyme disease September 1, 2013 New Hampshire, Nashua Telegraph
...  the black-legged tick picks up the bacteria – a spirochete, to get technical – as a larva from the blood of the white-footed mouse, which carries the bacteria. ... They aren’t called “deer ticks” anymore ...  even if every deer in New Hampshire became tick-free, we could still get Lyme from ticks via the white-footed mouse...  the population of white-footed mice has exploded ... A variant of the deer feeding station idea is available for ticks: cardboard tubes filled with cotton balls treated with permethrin, a tick insecticide. Mice take the cotton back to their nests as building material, and it kills the ticks...

... Deer don't experience severe winter tick infestations. They tend to groom off questing winter ticks in autumn...Overwintering deer ticks may be reduced by extreme cold. That good news translates into a reduction in future rates of human Lyme disease... 

East Hampton, Deer in Town Sights July 5, 2012 New York, East Hampton Star 
... As for Lyme disease, the Group for Wildlife suggests that the town do more to educate the public about how to avoid tick bites and to prohibit the hunting of turkeys, which eat immature ticks. Because Lyme disease is also spread by ticks that feed on the white-footed mouse, the report says, “it’s unlikely that any reduction of deer populations can alleviate the disease.” ... if deer were eliminated, the ticks would feed on other animals ... two recent studies show that “four-poster” stations, where deer are exposed to tick-killing chemicals, reduced ticks by 69 to 100 percent.... 

... Efforts to reduce Lyme disease with deer hunting are ineffective because the ticks feed on a wide variety of host species ... The only places where hunting is effective are in isolated areas—islands and peninsulas–where the ticks have few alternate hosts. To reduce the incidence of Lyme disease in humans on the mainland, the number of ticks needs to be reduced, not the number of deer. A 2011 study published in Public Health Reports found that a tick-killing device led to a reduction in the incidence of Lyme disease in humans in the area, while deer hunting “did not show a clear decreasing trend.” ...

Missing Foxes Fuel Lyme Disease Spread June 18, 2012 LiveScience.com
Researchers used to think the increases were due to increasing deer populations ,,, However, the new data show these increases were independent of deer population levels... "Increases in Lyme disease in the Northeastern and Midwestern United States over the past three decades are frequently uncorrelated with deer abundance and instead coincide with a range-wide decline of a key small-mammal predator, the red fox, likely due to expansion of coyote populations,"... in the journal Proceedings of the National Academy of Sciences (June 18, 2012 article). 

... County data shows the deer management program racked up 5,598 deer kills during the 2012-2013 seasons, 5,571 in 2011-2012, 5,969 in 2010-2011 and 5,599 in 2009-2010.  Despite those totals...      In the case of Lyme disease, which some dispute is related to deer overpopulation, the numbers have also remained steady. There were 297 confirmed and probably cases of Lyme disease in the county in 2011 and 296 in 2010, the two most recent years that those statistics were available.

Surprise Culprits of Lyme Disease Boom June 18, 2012 Discovery News
Deer are not to blame for rising rates of Lyme disease ... Foxes don’t spread Lyme disease directly. Instead, they cull populations of small mammals, which are responsible for the bulk of infectious ticks. Where foxes are thriving, the risk of disease drops. But when fox numbers fall – often because coyotes move in, small mammal populations surge and Lyme disease flourishes. 

Killing deer is no solution [to Lyme Disease] September 17, 2013 Connecticut, The Advocate, Laura Simon
Preventing Lyme disease is a vital goal, but killing deer isn't a solution ... Even when deer numbers are drastically lowered, ticks have no trouble finding other hosts and reproducing merrily.... Mice and chipmunks are important hosts for the immature stages of the tick, and popular songbirds bring ticks to new areas... National health authorities, such as the Centers for Disease Control and World Health Authority, as well as Connecticut State Health Department, are not calling for increased hunting because it will not effectively reduce human disease risk...

Predators, Prey and Lyme Disease June 18, 2012 New York Times (blog)
... While people used to blame deer for the spread of Lyme disease, Dr. Levi said that scientific evidence has indicated that deer probably aren’t significant transmitters of B. burgdorferi bacteria because their systems tend to quickly flush it out. ... models showed higher numbers of Lyme disease cases in places where there are fewer foxes. They detected no significant relationship between numbers of deer and numbers of Lyme disease cases.

Deer, predators, and the emergence of Lyme disease Proceedings of the National Academy of Science. June 18, 2012. Taal Levi, A. Marm Kilpatrick, Marc Mangel, and Christopher C. Wilmers
Abstract
Lyme disease is the most prevalent vector-borne disease in North America, and both the annual incidence and geographic range are increasing. The emergence of Lyme disease has been attributed to a century-long recovery of deer, an important reproductive host for adult ticks. However, a growing body of evidence suggests that Lyme disease risk may now be more dynamically linked to fluctuations in the abundance of small-mammal hosts that are thought to infect the majority of ticks. The continuing and rapid increase in Lyme disease over the past two decades, long after the recolonization of deer, suggests that other factors, including changes in the ecology of small-mammal hosts may be responsible for the continuing emergence of Lyme disease. We present a theoretical model that illustrates how reductions in small-mammal predators can sharply increase Lyme disease risk. We then show that increases in Lyme disease in the northeastern and midwestern United States over the past three decades are frequently uncorrelated with deer abundance and instead coincide with a range-wide decline of a key small-mammal predator, the red fox, likely due to expansion of coyote populations. Further, across four states we find poor spatial correlation between deer abundance and Lyme disease incidence, but coyote abundance and fox rarity effectively predict the spatial distribution of Lyme disease in New York. These results suggest that changes in predator communities may have cascading impacts that facilitate the emergence of zoonotic diseases, the vast majority of which rely on hosts that occupy low trophic levels.

Climate, Deer, Rodents, and Acorns as Determinants of Variation in Lyme-Disease Risk Ostfeld RS, Canham CD, Oggenfuss K, Winchcombe RJ, Keesing F (2006) Climate, Deer, Rodents, and Acorns as Determinants of Variation in Lyme-Disease Risk. PLoS Biol 4(6): e145. doi:10.1371/journal.pbio.0040145
Indices of deer abundance had no predictive power, and precipitation in the current year and temperature in the prior year had only weak effects on entomological risk. The strongest predictors of a current year's risk were the prior year's abundance of mice and chipmunks and abundance of acorns 2 y previously. In no case did inclusion of deer or climate variables improve the predictive power of models based on rodents, acorns, or both. We conclude that interannual variation in entomological risk of exposure to Lyme disease is correlated positively with prior abundance of key hosts for the immature stages of the tick vector and with critical food resources for those hosts.

Biodiversity and Disease Risk: The Case of Lyme Disease Richard S. Ostfeld and Felicia Keesing
Conservation Biology Vol. 14, No. 3 (Jun., 2000), pp. 722-728
"A positive correlation between Lyme disease per capita and species richness of ground dwelling birds . . ."
Full Abstract: Utilitarian arguments concerning the value of biodiversity often include the benefits of animals, plants, and microbes as sources of medicines and as laboratory models of disease. The concept that species diversity per se may influence risk of exposure to disease has not been well developed, however. We present a conceptual model of how high species richness and evenness in communities of terrestrial vertebrates may reduce risk of exposure to Lyme disease, a spirochetal (Borrelia burgdorferi) disease transmitted by ixodid tick vectors. Many ticks never become infected because some hosts are highly inefficient at transmitting spirochete infections to feeding ti cks. In North America, the most competent reservoir host for the Lyme disease agent is the white-footed mouse (Peromyscus leucopus), a species that is widespread and locally abundant. We suggest that increases in species diversity within host communities may dilute the power of white-footed mice to infect ticks by causing more ticks to feed on inefficient disease reservoirs. High species diversity therefore is expected to result in lower prevalence of infection in ticks and consequently in lower risk of human exposure to Lyme disease. Analyses of states and multistate regions along the east coast of the United States demonstrated significant negative correlations between species richness of terrestrial small mammals (orders Rodentia, Insectivora, and Lagomorpha), a key group of hosts for ticks, and per capita numbers of reported Lyme disease cases, which supports our "dilution effect" hypothesis. We contrasted these findings to what might be expected when vectors acquire disease agents efficiently from many hosts, in which case infection prevalence of ticks may increase with increasing diversity hosts. A positive correlation between per capita Lyme disease cases and species richness of ground-dwelling birds supported this hypothesis, which we call the "rescue effect." The reservoir competence of hosts within vertebrate communities and the degree of specialization by ticks on particular hosts will strongly influence the relationship between species diversity and the risk of exposure to the many vector-borne diseases that plague humans.

Dilution Effect, "the scientific evidence as I’ve reviewed it, without any preconceived notion or political agenda or any other agenda, does not support the notion that tick numbers and Lyme disease risk are strongly correlated with deer numbers, and the data do not suggest that if you manage deer by hunting, you’ll reduce the number of Lyme cases.” Dr. Richard S. Ostfeld Disease Ecologist Ph.D., 1985, University of California. Buy the book on Amazon: Lyme Disease: The Ecology of a Complex System

Acorns And Mice Driving Unusual Lyme Disease Risks (ICEID 2) March 14, 2012, Wired News
Dr. Richard S. Ostfeld of the Cary Institute of Ecosystem Studies in Millbrook, New York, explained .. Mice also can survive in much smaller areas than the larger animals, chiefly deer, that are usually blamed for perpetuating Lyme, Ostfeld pointed out. In sampling of “forest fragments” sliced up by development in three northeastern states, his team has not found a parcel in which mice did not thrive. Larger parcels with more balanced ecosystems, with natural mouse predators and larger mammals, actually tend to have lower Lyme density ...

White-tailed deer live throughout Minnesota, but blacklegged ticks are not found everywhere that deer live
From Michigan Department of Natural Resources (Lyme disease): The relationship between deer and the disease is complex. Deer show no symptoms of the disease. Deer may carry small numbers of the spirochete that causes Lyme disease but they are dead-end hosts for the bacterium. Deer cannot infect another animal directly and no deer hunter has acquired the disease from dressing out a deer. Infected ticks that drop from deer present little risk to humans or other animals since the ticks are now at the end of their life cycle and will not feed again. There is no evidence that humans can become infected by eating venison from an infected deer. In addition, the Lyme organism is killed by the high temperatures that would be reached when venison is cooked or smoked. Deer supply the tick that transmits the bacterium with a place to mate and provides a blood meal for the female tick prior to production of eggs. Research has shown that white-tailed deer are important to the reproductive success of the black-legged tick. In the absence of deer, this tick will opportunistically feed on other medium sized mammals and humans. As a management tool for Lyme Disease, there is still debate in the scientific community as to whether reducing the number of deer present in an area will effectively or dramatically reduce Lyme Disease "risk".

Research Summary: Deer are immune to Lyme disease and do not carry the diseases. If an infected tick bites a deer, the disease does not spread to other ticks that may bite the deer as it would if the tick bit a mouse. Reducing the number of deer may reduce the number of ticks, but because of the dilution effect, the result can be a higher percentage of remaining ticks with the disease since the ticks will choose other hosts that may be carriers of the disease. Deer also browse on the vegetation that provide tick habitat. While deer may provide a meal for the adult tick, research shows the risk of Lyme disease is statistically correlated to mice, chipmunks, and ground dwelling birds. Deer groom themselves, eliminating many ticks. Lyme disease originated in Connecticut

Duke Forest, Our illogical war on deer February 9, 2013 North Carolina, The Durham News, Karin Yates
...   According to John Rohm of the Virginia Department of Game and Inland Fisheries, “Reducing deer density by X will not = X percentage reduction in Lyme disease cases. ... Deer should not be blamed for the current Lyme disease situation. Integrated pest management would be more effective than focusing solely on deer.”

Deer ticks thriving in Ohio December 3, 2013  StarBeacon.com
... “Migratory birds probably brought them to Ohio from Pennsylvania,” Needham said [Glen Needham, Ph. D., a deer tick expert and associate professor emeritus at Ohio State University] ... “Deer ticks will feed on anything despite their name,” ..

Explanation for Chronic Lyme Disease
Does this new study put an end to the chronic Lyme Disease controversy? Allentown Morning Call   November 16, 2012 
... It's not one stubborn infection that is making them ill, states a study released this week by the New England Journal of Medicine, but multiple new infections.  Researchers at the University of Pennsylvania and New York Medical College studied 17 patients, who had the classic erythema migrans rash associated with Lyme disease, more than once in a span of 20 years. They analyzed the genetic makeup of the Lyme-causing bacteria in those who had been sick several times. Each time, they were infected by different strains of the bacteria, ruling out relapses.

... Borrelia burgdorferi, the bacterium that causes Lyme disease, hitchhikes in ticks for dissemination to mammalian hosts–including humans. An article in the 19 December issue of PLOS Pathogens identifies HrpA, an RNA helicase, as a crucial player in the transmission from ticks to mammals... The authors say, “We now know that HrpA is involved in both parts of the B. burgdorferi lifecycle: animal infection and tick transmission, making it a very important protein in B. burgdorferi gene regulation and establishing gene regulation through an RNA helicase as an important regulatory pathway in the Lyme spirochete.”

Other Motives for the Lyme Disease Hunts
Odgen Dunes, Deer Management Task Force Publishes Findings/Opinions July 12, 2012 Indiana, SaveOurDeer.Org
... Ogden Dunes has not come to a consensus on whether there is an overabundance of deer in Ogden Dunes. But they have come to a consensus that killing deer will not eliminate the risk of Lyme Disease ... Despite this development, the threat of a deer cull within Town limits seems to remain. Why? ... It appears the real reason for the deer cull was never to protect young families from the risk of Lyme Disease. The Town government was using the fear factor of Lyme Disease to promote the idea of a deer cull when the real reason was to kill deer to keep them from eating the plants of prominent town residents... 

Moose Die-Off Alarms Scientists October 14, 2013 New York, New York Times
... Across North America ... moose populations are in steep decline. And no one is sure why... Minnesota had two geographically separate moose populations. One of them has virtually disappeared since the 1990s, declining to fewer than 100 from 4,000... In New Hampshire, a longer fall with less snow has greatly increased the number of winter ticks, a devastating parasite... Deer are grooming animals, so they are able to keep tick numbers fairly low ...




Information about the 4-poster System Used to Control Ticks on Deer 

Lyme Disease - Will Shelton go the Wrong Way? June 29, 2014 Connecticut, Shelton Patch 
...  After reviewing the numbers from the last four years,  provided by both the Connecticut Health Department and the CT DEEP we see that the deer population is now down 60% + and that Lyme disease, reported cases in Redding are up  62.5%.  In 2010 the Redding, CT reported Lyme cases were  8  and in 2013 they are now 13.  What happened to all the " Wildlife Experts " that said, " Less Deer = Less Lyme " ?  ...

A dismissal of correlation between deer, Lyme disease September 11, 2013 Connecticut, Greenwich Time
... The public needs to be provided with facts and not fear-mongering. Required reading should be "Lyme Disease: The Ecology of a Complex System" by Dr. Richard Ostfeld published last year, which synthesized just about every study written on this topic. He concluded that there is little to no correlation between deer and Lyme disease and no studies that correlate a reduction in the deer population to a reduction in the incidence of the disease. There are four small mammals, including the white-footed mouse that account for 90 percent of infected ticks...

Culling deer won't reduce Lyme disease June 20, 2013 British Columbia, Victoria Times Colonist
... According to the B.C. Centre for Disease Control, there is no evidence to support an epidemic of Lyme disease in B.C. ,,, Culling deer does not reduce Lyme disease occurrence... unless we want to eradicate all small mammals as well as the songbird population, our dogs and horses and the deer, we will have to learn to tolerate the western black-legged tick ...

The automatic association of Lyme disease with deer may be flawed August 27, 2014 Massachusetts, Martha's Vineyard Times 
... The abundance of deer and near absence of ticks in Aquinnah’s lush wetland forest, and abundance of ticks despite a lower number of deer in Chilmark’s dry oak forest suggest that the differences go deeper than the relationship between deer and their parasites...One of the chief differences between them is that oak forests produce more starch in the form of acorns that squirrels can hoard, leaving plenty for other rodents such as white-footed mice, which serve as the hosts for immature deer ticks. The mice are a crucial carrier of the ticks, which thrive, even when there aren’t many deer ...

Strange events will lead to increase of Lyme disease this year March 22, 2012 Fox News 
... But don't blame the deer. The predicted rise in ticks that carry Lyme disease is actually the result of a cascade of ecological events that started back in 2010 and involves acorns and mice, says Richard S. Ostfeld, a disease ecologist at the Cary Institute of Ecosystem Studies in Millbrook, N.Y.... The white-footed mouse is the perfect host for ticks (low to the ground and not bothered by the parasites), said Ostfeld, who has published several studies showing the population of mice, not deer, is more directly correlated to the tick population

Duke Forest, Our illogical war on deer February 9, 2013 North Carolina, The Durham News, Karin Yates
...  I recently witnessed a buck lying down in a yard in Chapel Hill with an arrow protruding form his left hind quarter... It is important for us to understand that deer do not “carry” or “spread” Lyme disease. In fact, deer provide a buffer between the host (white-footed mouse) and humans by “collecting” the ticks on themselves.  According to John Rohm of the Virginia Department of Game and Inland Fisheries, “Reducing deer density by X will not = X percentage reduction in Lyme disease cases. ... Deer should not be blamed for the current Lyme disease situation. Integrated pest management would be more effective than focusing solely on deer.”

Tick...Tick...Tick, white-footed mouse main reservoir for Lyme disease March 16, 2011 Rhode Island Patch.com Directed, produced, and narrated by Mary Healey Jamiel, "Hidden in the Leaves" is a 24-minute film about deer ticks. The DVD features the work of Thomas N. Mather, Ph.D., Director of the University of Rhode Island's Center for Vector-Borne Disease. ...

Why Killing Deer Doesn't Prevent Lyme Disease - Double click for full screen



One study often cited as an example of reducing Lyme disease by reducing the deer population, was done on an offshore island with little biodiversity so few alternate hosts for ticks. Rand, P.W., et al. 2004. Abundance of Ixodes scapularis (acari:Ixodidae) after complete removal of deer from an isolated offshore island, endemic for Lyme disease. Journal of Medical Entomology 41:779-784 

TICK CONTROL B Trapping, H Munugement - Biology of Ticks, 2013, p. 427
... some years after deer reduction tick densities were similar to those in some years before deer reduction (Deblinger, 1993).  Indeed, a meta-analysis of deer exclusion data sugged that small deer exclosures can actually increase densities of some tick species (Perkins, 2006).  These conflicting results apparently are derived from interacting factors that influence tick numbers beyond the effects of host density alone (e.g. the movement of small vertebrates hosts, physical conditions in differend habitat types, exclosure size and habitat fragmentation effects), and some of these can shift in importance from year to year.  For example... The numbers of nymphs in these exclosures declined after 3 years their levels within exclosures had increased enough to be comparable to outside control areas.

WILSON, M. L., DUCEY, A. M., LITWIN, T. S., GAVIN, T. A. and SPIELMAN, A. (1990), Microgeographic distribution of immature Ixodes dammini ticks correlated with that of deer. Medical and Veterinary Entomology, 4: 151–159. doi: 10.1111/j.1365-2915.1990.tb00273.x
ABSTRACT. In order to determine whether the small-scale distribution of immature Ixodes dammini Spielman et al. corresponds closely to the activity patterns of white-tailed deer, Odocoileus virginianus (Zimmerman), these relationships were examined in a site on Long Island, New York, U.S.A. We first determined the extent and temporal pattern of adult ticks feeding on deer by examining twenty-three resident deer tranquilized during September-December 1985.1, dammini adults infested deer throughout this fall period, most abundantly during October and November. With radio-telemetry collars attached to deer we determined the relative frequency that they occupied 0.25 ha quadrats of the study site. During the following summer, we examined white-footed mice, Peromyscus leucopus (Rafmesque), that inhabited these quadrats and removed immature ticks from each. 8975 larval and 163 nymphal /. dammini were removed from 208 mice trapped in forty-three such quadrats. The frequency of deer using these quadrats was positively correlated with both the number of larval and of nymphal ticks per mouse. These results suggest that risk of I.dammini-borne zoonotic disease may be decreased by locally reducing deer density in sites that experience intense human activity.

Localized Deer Absence Leads to Tick Amplification
Localized Deer Absence Leads to Tick Amplification
Sarah E. Perkins, Isabella M. Cattadori, Valentina Tagliapietra, Annapaola P. Rizzoli and Peter J. Hudson Ecology Vol. 87, No. 8 (Aug., 2006), pp. 1981-1986 Published by: Ecological Society of America
Deer support high tick intensities, perpetuating tick populations, but they do not support tick-borne pathogen transmission, so are dilution hosts. We test the hypothesis that absence of deer (loss of a dilution host) will result in either an increase or a reduction in tick density, and that the outcome is scale dependent. We use a complementary methodological approach starting with meta-analysis, followed up by a field experiment. Meta-analysis indicated that larger deer exclosures reduce questing (host-seeking) tick density, but as the exclosure becomes smaller (&lt2.5 ha) the questing tick density is increased (amplified). To determine the consequences for tick-borne pathogen transmission we carried out a field experiment, comparing the intensity of ticks that fed on hosts competent for tick-borne pathogen transmission (rodents) in two small (&lt1 ha) deer exclosures and their replicated controls. Intensity of larval ticks on rodents was not significantly different between treatments, but nymph intensity, the tick stage responsible for tick-borne encephalitis (TBE) transmission, was higher in deer exclosures. TBE seropositive rodents were found in a deer exclosure but not in the controls. We propose that localized absence of deer (loss of a dilution host) increases tick feeding on rodents, leading to the potential for tick-borne disease hotspots.

Deer-free areas may be haven for ticks, disease Penn State Study

Reduced abundance of immature Ixodes dammini (Acari: Ixodidae) following incremental removal of deer. J Med Entomol. 1993 Jan;30(1):144-50 Deblinger RD, Wilson ML, Rimmer DW, Spielman A. Trustees of Reservations, Beverly, MA 01915.
Abstract:  
The abundance of immature Ixodes dammini Spielman, Clifford, Piesman & Corwin was monitored for 9 yr (1983-1991) before and during the controlled, limited hunting of white-tailed deer, Odocoileus virginianus (Zimmerman), at a coastal Massachusetts site. Deer abundance was reduced from an estimated 350 during 1985 to approximately 60 during 1991. Although annual fluctuations were large, mean larval I. dammini abundance declined from 20.8 per white-footed mouse, Peromyscus leucopus (Rafinesque), during 1983-1986 before deer reduction to 10.3 per mouse following deer reduction (1987-1991). Similarly, mean nymphal I. dammini abundance declined from 2.7 per mouse before intervention to 1.6 per mouse after intervention. Immature I. dammini population fluctuations were not associated with those of P. leucopus. The total population of larvae infesting P. leucopus declined from 3,596 ticks before intervention to 1,535 ticks after intervention. Concurrently, the total nymphal population declined from 417 ticks before intervention to 187 ticks after intervention. The number of feeding adult female I. dammini on deer increased as deer density decreased.

Freehold Township > Tick Borne Disease Ecology > Current Research Study Results. After three seasons, the estimated deer population was reduced by 46.7 %, from the 2002 post-fawning estimate of 2,899 deer (45.6 deer/km2) to a 2005 estimate of 1,540 deer (24.3 deer/km2). There was no apparent effect of the deer culling program on numbers of questing nymphal ticks in the culling areas and the overall numbers of host-seeking ticks in the culling areas appeared to increase in the second year of the program. The Lyme disease incidence rate generated by both passive and active surveillance systems showed no clear trend among years and did not appear to vary with declining deer density. Cayuga Heights, NY: Richard Ostfeld, PhD Senior Scientist, the Cary Institute of Ecosystem Studies Author of Lyme Disease: The Ecology of a Complex System(2010, Oxford Univ. Press)
• DEIS incorrectly states that linear correlations exist between deer and ticks • No scientific data support the existence of a deer density threshold below which ticks decline to low numbers • Deer actually reduce the prevalence of Lyme infection in tick populations • Adult blacklegged ticks feed on at least 27 mammal species, not just deer • It’s misleading for DEIS to use Monehgan Island study to predict what will happen in Cayuga Heights. Read Statement

Cayuga Heights, NY: Tamara Awerbuch, PhD ,Instructor, Department of Population and International Health, Harvard School of Public Health
• Incorrect assumptions are made in DEIS about the relationship between deer and “deer ticks”, which have no basis in science • There is no linear correlation between killing deer and the tick population • White-footed mice, and not deer, are the carriers of the agent of Lyme disease • In Ipswich, MA, Lyme disease kept growing following deer-killing program • “there is NO scientific justification for a deer killing program in your community”. Read Statement

POPULATION AND COMMUNITY ECOLOGY,
Effects of Reduced Deer Density on the Abundance of Ixodes scapularis
(Acari: Ixodidae) and Lyme Disease Incidence in a Northern
New Jersey Endemic Area
ROBERT A. JORDAN,
TERRY L. SCHULZE, AND MARGARET B. JAHN
Freehold Area Health Department, 1 Municipal Plaza, Freehold, NJ
07728
J. Med. Entomol. 44(5): 752Ð757 (2007)
ABSTRACT We monitored the abundance of Ixodes scapularis Say (Acari: Ixodidae) and the Lyme
disease incidence rate after the incremental removal of white-tailed deer, Odocoileus virginianus Zimmermann, within a suburban residential area to determine whether there was a measurable decrease in the abundance of ticks due to deer removal and whether the reduction in ticks resulted in a reduction in the incidence rate within the human population. After three seasons, the estimated deer population was reduced by 46.7%, from the 2002 postfawning estimate of 2,899 deer (45.6 deer per km2) to a 2005 estimate of 1,540 deer (24.3 deer per km2). There was no apparent effect of the deer culling program on numbers of questing I. scapularis subadults in the culling areas, and the overall numbers of host-seeking ticks in the culling areas seemed to increase in the second year of the program. The Lyme disease incidence rate generated by both passive and active surveillance systems showed no clear trend among years, and it did not seem to vary with declining deer density. Given the resources required to mount and maintain a community-based program of sufficient magnitude to effectively reduce vector tick density in ecologically open situations where there are fe impediments to deer movement, it may be that deer reduction, although serving other community goals, is unlikely to be a primary means of tick control by itself. However, in concert with other tick control interventions, such programs may provide one aspect of a successful community effort to reduce the abundance of vector ticks.

Overpopulation problems December 20, 2010 Part 2 of 3 The Adirondack Daily Enterprise
Biologists Felicia Keesing and Richard Ostfeld reject the tick-Lyme disease connection, noting that studies in New York and New Jersey found no correlation between the number of deer and the number of ticks in a region. These researchers argue that when deer are scarce, ticks simply move to alternate hosts: raccoons, skunks, opossums and other medium sized animals. Keesing and Ostfeld note that Lyme disease is rare in Southeastern and most Midwestern states, regions of the country where deer are plentiful.
Lyme in U.S.




Tick Management for Deer Deer and Elk Farmers DIscussion
The dosage rate we use is 250ml of Ivomec (pour-on) per ton of feed. We prep the feed in the following manner. Using a small spray bottle, we mix 12 ml of ivomec to 2 pints of water. We then take 100# of feed and spread it out on a 4x8 sheet of untreated plywood. We spray a light coat( about 1/2 of the mixture) of the ivo/H20 mix over the feed, then allow to dry completely. If you use a feed with a water sheild on it, it less effective. Using a simple dust-pan, we scoop and flip the feed over, much like flipping a pancake on the griddle, then apply the remaining amount of the mixture to the other side of the feed and allow to dry completely. Replace it back into the bags and distribute it just like you are using normal feed. It is important to do this on a warm sunny day when possible, and always wear latex gloves. In our bulk trough feeders, we coat the top of the feed with the same dosage rate per pound, and allow the deer to eat through the layer of ivomec. We do this every6 months, alternating with Purina Exotic Animal De wormer on a 6 month rotation, providing a worming treatment every quarter. We try to time it as to not have any of the treatments closer than one month to the birthing of fawns. This is easy if you have a single species in the enclosure, but in multiple species populations, it requires a good deal of thought to maximize the gaps between birthing cycles. Having said that, we have had births in some of the horned species within days following a treatment with no adverse affects. This works well in helping control ticks. In addition to these treatments, we use powdered garlic in our feed at the rate of 2# per ton of feed throughout the year. I find it to be very effective in reducing ticks and the animals do not seem to mind the taste.

Some Contradictory Results from Connecticut

Reducing deer populations may reduce risk of Lyme disease Science Codex 2014 Kilpatrick, Howard J ... Journal of Medical Entomology, Volume 51, Number 4, Pages 725-906, pp. 777-784(8)
... After hunts were initiated, number and frequency of deer observations in the community were greatly reduced as were resident-reported cases of Lyme disease. Number of resident-reported cases of Lyme disease per 100 households was strongly correlated to deer density in the community... 

... The authors also examined the relationship between deer population density and human Lyme incidence rate. They analyzed data from Connecticut's Department of Environmental Protection and the Department of Public Health from 1999 through 2008 by deer management zone (DMZ) and town. For DVA incidence rate versus Lyme incidence rate for both DMZs and towns, most of the correlation coefficients computed yearly were moderate to strong and all of the p-values were significant. A weak correlation was observed between deer population density and Lyme disease incidence rate by DMZ. The authors propose DVAs as a proxy for measuring the interaction between coexisting populations of humans and deer.