Piesman

Lyme Disease Ecology : 

Lyme Disease Ecology Lyme disease spirochete transmission cycle extremely efficient in the Northeastern United States Differences from North to South B. lonestari status Future needs for research

Lyme Disease: 

Lyme Disease Caused by the spirochete Borrelia burgdorferi sensu stricto Transmitted by Ixodes scapularis Reservoirs for the spirochete include Small mammals (mice, squirrels, chipmunks, etc.) Birds Hosts for the tick include Small mammals (larvae & nymphs) Deer and other large mammals (adults) Deer required for tick population maintenance

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Photo by R Johnson

Lyme Disease Transmission Cycle: 

Lyme Disease Transmission Cycle Larvae: Aug-Sept (Year 1) Nymphs: May-July (Year 2) Adults: Oct-Dec & Mar-Apr (Year 2) Egg production: May-June (new cycle)

Key Point #1: Proportion of I. scapularis infected with Bb extremely high in NE: 

Key Point #1: Proportion of I. scapularis infected with Bb extremely high in NE Larvae: Uninfected Nymphs: 15-25% + Adult Females: 40-50% + Why is cycle so efficient? Immature ticks focus on competent hosts

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Peromyscus Tamias Microtus Photos from varied internet sites & field guides

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Photo from internet site or field guide Sciurus

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Photo from internet site or field guide Didelphis Syviligus

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Odocoileus virginianus

Hanincova et al. 2006Lake Gaillard, CT: 

Hanincova et al. 2006 Lake Gaillard, CT White-footed mouse Gray Squirrel Pine vole Eastern chipmunk Virginia opossum Raccoon Questing nymphs 90% + 32% + 26% + 23% + 10% + 8% + 69/178 = 39% +

Key Point #2: 

Key Point #2 Nymphs are small (<2 mm) and can feed for the >48 hrs required for transmission and escape detection

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FREQUENTLY ESCAPES NOTICE BECAUSE OF ITS SMALL SIZE BITING NYMPH Photo Provided by D Fish

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T = (1 ‑ exp[-λγ (t ‑ G)γ ] ) × k From DesVignes et al

Key Point #3: 

Key Point #3 In hyperendemic regions of the NE, lots of questing infected nymphal I. scapularis bite people

Nymphal I. scapularis bites from health department records: 

Nymphal I. scapularis bites from health department records Westchester County, NY N=444 from 1985-1989 Falco et al. 1996 Am J Epidemiol Westchester County, NY Deterministic Model 1991-94 Estimate of 178,889 bites per year Campbell et al. 1998 Am J Epidemiol CT Agric Exp Station; accepts ticks statewide for testing Average # nymphal I. scapularis approx 5,000 per year (K Stafford, personal communication)

SO WHAT IS DIFFERENT IN THE LYME DISEASE CYCLE FROM NORTH TO SOUTH?ONE MAJOR DIFFERENCE---: 

SO WHAT IS DIFFERENT IN THE LYME DISEASE CYCLE FROM NORTH TO SOUTH? ONE MAJOR DIFFERENCE---

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Photo by R Eisen

Immature I. scapularis focus on lizards rather than small mammals in the southeastern US: 

Immature I. scapularis focus on lizards rather than small mammals in the southeastern US Durden et al. 2002 Exp Appl Acarol; St Catherine’s Is., Liberty Co, GA; 309 reptiles exm; broad-headed skink, southeastern 5-lined skink, eastern glass lizard-heavily infested w I. scapularis (>51 larvae & >7 nymphs per lizard) Levine et al. 1997 J Med Entomol; museum specimens from 80 N Carolina counties; 117 lizards infested with I. scapularis immatures (max #=179). Most (+) from coastal plains.

Immature I. scapularis in the southeast are few & far between on rodents: 

Immature I. scapularis in the southeast are few & far between on rodents Clark et al. 2001 J Parasitol; A total of 237 rodents from South Carolina 24 I. scapularis on 97 cotton mice (0.2@) 5 I. scapularis on 49 eastern woodrats (0.1@) 2 I. scapularis on 60 hispid cotton rats (0.03@) *Cryptic cycle involving I. minor, I. affinis, & woodrats

Key points derived from focus of immature I. scapularis on lizards in the Southeast: 

Key points derived from focus of immature I. scapularis on lizards in the Southeast In general*, lizard complement is lytic to B. burgdorferi sensu stricto so lizards are not reservoir competent for these spirochetes. Thus, spirochetal infection in southeastern I. scapularis is extremely rare. Nymphal I. scapularis do not quest above the leaf litter in the southeast so they don’t get picked up on drag samples and they don’t bite people *Some conflicting evidence in scientific literature

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WORST JOB IN SCIENCE: TICK COLLECTING Popular Science November 2004

Tick Dragger: Worst Science Jobs: 

Tick Dragger: Worst Science Jobs Go to remote, densely overgrown forest. Take out giant white corduroy sheet. Drag it behind you as you sing loudly to ward off bears. After 20 meters, stop. Do not tarry to smack mosquitoes, for you must immediately tweezer several hundred tiny potentially Lyme disease carrying ticks that have covered both you and your white cloth, and drop them into a jar. Repeat 50 times a day. No this is not the instruction set for hell week at Phi Delta Sade. It’s the protocol for a study assessing Lyme disease risk across the eastern U.S., headed by Yale University epidemiologist Durland Fish. From Popular Science Nov 2004

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Density of host-seeking Ixodes scapularis nymphs (2004 – 2006) Data by M Diuk-Wasser, Yale Univ. & Risk Map Study Group

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From Hayes & Piesman, NEJM 2003

Lone star tick : 

Lone star tick Most common person-biting tick in southeastern US All three stages bite people aggressively All three stages feed mainly on deer Will occasionally feed on birds but almost never on rodents Schulze et al. 1984 Science; spirochetes present in A. americanum from NJ

Barbour et al. 1996 J Infect Dis: 

Barbour et al. 1996 J Infect Dis 2% of A. americanum from MO, TX, NJ, NY infected with spirochetes Spirochetes could not be cultured in BSK PCR analysis based on 16S rRNA gene & flagellin gene showed that it was a unique spirochete (only 96% identity with B. burgdorferi on 16S) Provisionally named: B. lonestari

Current state of Knowledge on B. lonestari Biology & Ecology: 

Current state of Knowledge on B. lonestari Biology & Ecology There is a group of “Hard tick relapsing fever spirochetes” that include: B. miyamotoi sensu lato from Ixodes persulcatus, I. scapularis, I. ricinus B. lonestari from Amblyomma americanum B. theileri from Rhipicephalus (“Boophilus”) from Africa and Latin America These spirochetes are distinct from but closely related to classical TBRF organisms

Rapid Progress Made by S Little Lab (Univ GA & Okla St Univ): 

Rapid Progress Made by S Little Lab (Univ GA & Okla St Univ) Successful culture of B. lonestari in association with tick cells Lizard and mouse sera lytic for B. lonestari Deer develop spirochetemia when inoculated w B. lonestari whereas mice, calves, and dogs do not B. burgdorferi produces EM in rabbit model but B. lonestari has not, to date

Results of culture attempt: 

Results of culture attempt spirochetes found 14 days after inoculation with PCR-positive tick tissues LS-1 From S Little, Oklahoma St Univ

Results: Deer fawns (n=2): 

Inoculated B. lonestari spirochetes into deer  infected and spirochetemic PCR One or both deer PCR positive DPI 4,6,8,12,15,19,22,28 Blood smear Rare spirochetes on blood smears from one or both deer collected DPI 6,8,12,15 Culture B. lonestari re-isolated in tick cell co-culture from deer DPI 6, 12 Results: Deer fawns (n=2) From S Little Oklahoma State Univ

FUTURE: 

FUTURE Determine to what extent potential person-biting questing ticks are infected w B. burgdorferi sensu stricto in the southeast Elucidate the role of lizards as reservoirs of B. burgdorferi Determine whether B. lonestari plays any role in causing Lyme disease in the southeast Identify any unknown pathogens associated with ticks in the southeastern US