Increased Tick Prevalence: The Battleground Shifts with More Pets at Risk. July 18-31, 2011

Transcription

1 Increased Tick Prevalence: The July 18 31, 2011 By Michael Dryden, DVM, PhD & Susan Little, DVM, PhD AAHA gratefully acknowledges Merial, Ltd. for their sponsorship of this webcast. Increased Tick Prevalence: The Battleground Shifts with More Pets at Risk Michael W. Dryden, DVM, PhD University Distinguished Professor College of Veterinary Medicine Kansas State University Manhattan, Kansas Susan E. Little, DVM, PhD Regents Professor and Krull-Ewing Endowed Chair in Veterinary Parasitology Oklahoma State University Stillwater, Oklahoma 1

2 Species of Interest - U.S. Amblyomma americanum - Lone Star Tick Amblyomma maculatum - Gulf Coast Tick Dermacentor albipictus Winter Tick Dermacentor andersoni - Rocky Mountain Wood Tick Dermacentor occidentalis - Pacific Coast Tick Dermacentor variabilis - American Dog Tick Ixodes pacificus Western Black-legged Tick Ixodes scapularis - Black Legged Tick Otobius megnini - Spinose Ear Tick Rhipicephalus sanguineus - Brown Dog Tick Tick Life Cycles Most hard ticks of importance to dogs and cats in North America are termed 3-host ticks. Each life stage feeds on a separate host. 1. Larva hatches from egg, feeds on a host for a few days, falls off & molts. 2. Nymph finds a host and feeds, falls off & molts. 3. Adult finds a host and feeds, then falls off to lay eggs (female) and then dies. Molt in 3wks several months Adult Eggs Nymph Engorge in 6 14 days Typical 3-host tick Not uncommon to take 2 to 3 years to complete life cycle. Eggs hatch in days Larva Engorge in 3 8 days Molt in 3 14 days Engorge in 3 9 days 2

3 Factors Supporting Tick Populations Hosts Wildlife, domestic animals (cattle, horses), untreated pets Habitat Wooded area, understory, leaf litter, tall grass, brush piles/debris Climate Temperature, humidity Hosts With the exception of the Brown dog tick (Rhipicephalus sanguineus), the vast majority of the immature and reproducing tick populations (>99%) are not on dogs or cats, but on their natural wildlife hosts. Natural Hosts 3

4 Natural Tick Hosts The distribution and abundance of Ixodes scapularis and Amblyomma americanum are linked to the distribution and abundance of their primary reproductive host, the White- Tailed deer (O. virginianus) and a deciduous forest canopy. White-Tailed Deer Repopulation Deer were plentiful in the central and eastern North American up to the early 1800s. Hunters, homesteaders and Army units killed hundreds and occasionally thousands to feed and clothe troops and themselves. Using dogs, guns, steel traps, and wire snares, a skilled hunter could average ten deer a day. In December, 1872, Litchfield, Minnesota, shipped six tons of dressed venison to markets in Boston. In 1880, the freight offices in Michigan alone handled more than one hundred thousand deer destined for Chicago and the East. The return of the white-tailed deer American Heritage Magazine 21(2) February

5 White-Tailed Deer Repopulation By 1890 the deer population in North America hit rock bottom. The Appalachians and most of the country west to the Rockies were practically without deer. Rhode Island, Connecticut, Maryland, West Virginia, New Jersey, Ohio, Kentucky, Tennessee, Indiana, Illinois, Iowa, Kansas, Missouri, and Nebraska counted their whitetail herds at near zero. The last deer in Indiana was shot near Red Cloud in Deer extirpated from Southern Maine and southern New Hampshire. The return of the white-tailed deer American Heritage Magazine 21(2) February 1970 White-Tailed Deer Repopulation 1890: T. S. Palmer of the U. S. Biological Survey (antecedent of the U. S. Fish and Wildlife Service) estimated the wild white-tailed deer population of the United States and Canada at around 300,000. The return of the white-tailed deer American Heritage Magazine 21(2) February 1970 White-Tailed Deer Repopulation Then began a period of: Restricted hunting (permits & bag limits ). Game conservation, repopulation/relocation, federal law (the Lacey Act of 1900) banned interstate shipment of wild game meat - ending market hunting. Forest management and changes in land use (mixed hardwood-coniferous forest), changes in agricultural practices; leading to more edge habitat. Natural predators also had been eliminated (wolves, cougars, bear). The return of the white-tailed deer American Heritage Magazine 21(2) February

6 White-Tailed Deer Repopulation 2005: Estimated 27,700,000* An almost 100 fold (92.3x) increase in the White-tailed deer population in the U.S. in a little over 100 years. * Quality Deer Management Association 2005 Deer Distribution Map & individual state records (Florida, Indiana, Kansas & Pennsylvania) Quality Deer Management Association 2005 Deer Distribution Map Amblyomma americanum Excellent host for immature ticks 6

7 Wild Turkey in the U.S. By the Great Depression, very few wild turkeys remained in the entire country. Late 1930s < 30, ,400,000 National Wild Turkey Federation Factors Supporting Tick Populations Hosts Wildlife, domestic animals (cattle, horses), untreated pets Habitat Wooded area, understory, leaf litter, tall grass, brush piles/debris Climate Temperature, humidity Habitat Bale, 1987 Burks, 1996 Duffy, 1994 Needham, 1991 Important in determining: Availability of hosts Food and cover Off-Host Survival of Ixodid Ticks Conservation of body water Protection from freezing + Wide variation among tick species and studies» Ixodes scapularis -8 C to 16 C (Schmid 1992)» LLT2h (lowest lethal temperature) of I. scapularis, A. americanum and D. variabilis was negligible at temperatures > -9 C (16F) 7

8 Microclimate Where ticks survive off-host (for molting or diapause) Decaying grass, leaf litter/mold, detritus forest floor Buffer from the elements Absorbs radiant energy Reduces evening heat loss Maintains relative humidity Sonenshine, 1993 Factors Supporting Tick Populations Habitat: Meadows, brush, shrubbery, forests and tall grass. Decrease penetration of sunlight and result in increased humidity and higher soil moisture. Offer excellent habitat for natural hosts such as mice, other small rodents, medium sized mammals, birds, deer, etc. Questing Ticks 8

9 Changing & Expansion of Tick Ranges and Densities & Increase Exposure Changes in agricultural practices Reforestation Wildlife conservation, relocation and restocking Natural climate fluctuations Decreased environmental pesticide application Increased human contact with natural areas Recreation, occupation, travel, housing developments in forested areas Other ANTHROPOGENIC FOREST CHANGE AND EMERGING TICK- BORNE DISEASE Janet Foley Paddock CD, Yabsley MJ. Ecological havoc, the rise of white-tailed deer, and the emergence of Amblyomma americanumassociated zoonoses in the United States. Curr Top Microbiol Immunol. 2007;315: Species of Interest U.S. Amblyomma americanum - Lone Star Tick Amblyomma maculatum - Gulf Coast Tick Dermacentor albipictus Winter Tick Dermacentor andersoni - Rocky Mountain Wood Tick Dermacentor occidentalis - Pacific Coast Tick Dermacentor variabilis - American Dog Tick Ixodes pacificus Western Black-legged Tick Ixodes scapularis - Black Legged Tick Otobius megnini - Spinose Ear Tick Rhipicephalus sanguineus - Brown Dog Tick 9

10 D. variabilis Tick Distribution A. americanum D. andersoni I. pacificus I. scapularis Changing & Expansion of Tick Ranges and Densities & Increase Exposure Reasons for the increase of some tick species are not fully understood; likely multifactorial. Also, while the general trend in populations has been upward there can be large year to year fluctuations. Snowfall, rainfall, floods, temperature, fire, etc. Tick populations (species & density) in a region are not uniformly distributed. Tick islands Changing Tick Ecology Ticks species occurring in locations that they previously did not exist. Tick transmitted diseases are occurring in locations they previously did not exist. Ticks are occurring throughout the year in many locations. Due to natural climate fluctuations and introduction of different tick species. Tick densities are significantly higher in many locations. Leads to perception changes concerning efficacy of products. 10

11 II. Examples of Increasing Tick Encounters West Texas and New Mexico Have seen surprising increase in Brown dog tick populations. Roswell, New Mexico In practice over 20 years in Roswell. Historically almost no ticks on dogs. In past few years, has seen a large increase in dogs with ticks. Some dogs hundreds Parks & Trails Near Los Angeles June

12 Hiking Trails Almost Unusable D. variabilis and D. occidentalis Ticks at Home and Away From Home Ticks at Home and Away From Home 12

13 Ticks at Home and Away From Home Ticks Around the Home Ticks Infesting Homes 13

14 Ticks Infesting Homes Ticks Infesting Veterinary Practices! Rhipicephalus sanguineus All three stages prefer dogs In favorable conditions, 2-4 generations / year New Ticks in New Areas Amblyomma maculatum: the Gulf Coast tick Historic/established Current/recent 14

15 The Slow, Steady Spread of Lyme Disease Lyme Borreliosis Lyme Borreliosis

16 Questing activity Meeting the Tick Control Challenge Year-round acaricide use Need to routinely re-evaluate protocols Tick-scaping to manage environment Encourage tick-safe habits and behaviors Pet management to limit tick exposure Year-round Acaricide Use Apply according to calendar Not when see ticks Proactive/prophylactic use year round Cannot predict precisely when questing will begin If seeing ticks on the dogs it is already too late Routine use decreases acquisition of tickborne diseases in hyperendemic areas Seasonal Activity Brown dog ticks Lone star ticks American dog ticks Black-legged ticks Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month 16

17 Manage Habitat Limit tick habitat Remove leaf litter Burn debris Barrier between wooded area and yard Exclude/discourage wildlife Exclude whenever possible Remove debris close to home where rodents may nest Options for treatment of wildlife Limit Exposure to Ticks Keep pets in low-tick areas Dogs behind a fence in a well-designed ticksafe area Cats indoors THANK YOU! Michael W. Dryden, DVM, PhD University Distinguished Professor College of Veterinary Medicine Kansas State University Manhattan, Kansas Susan E. Little, DVM, PhD Regents Professor and Krull-Ewing Endowed Chair in Veterinary Parasitology Oklahoma State University Stillwater, Oklahoma 17

18 1. To complete the evaluation, please go to the following website: 2. After completing the evaluation, you will automatically be linked to the Continuing Education Certificate. The CE certificate can only be accessed after the evaluation is completed. 3. Download the CE Certificate (in PDF format) to your computer and print enough copies for those persons viewing the web conference with you. Your input is very important! We take feedback seriously in order to provide you with the highest quality experience possible. If you have any questions about completing the evaluation or accessing your CE certificate, please us at or call 800/ Questions to the Speakers Please your questions to by Sunday, August 7, Drs. Dryden and Little will provide written responses to all of the questions and they will be posted on AAHA s website by Friday, August 19, AAHA gratefully acknowledges Merial, Ltd. for their sponsorship of this webcast. 18