Biology of Ticks and Mites

L. Hannah Gould, MS, PhD

Bacterial Diseases BranchDivision of Vector-Borne Infectious DiseasesCenters for Disease Control and Prevention

Fort Collins, CO

Overview

• Ticks, mites, and their identification

• Tick-borne diseases in the United States– Lyme disease– Rocky Mountain Spotted Fever– Ehrlichiosis– Babesiosis– Tularemia– Tick-borne relapsing fever

• Mites

Ticks, mites, and their identification

Ticks and Mites

• Not insects• Four life stages

– Egg– Larva (6 legs)– Nymph (8 legs)– Adult (8 legs)

• Ticks: ≈ 80 species in US, 12 of public health/veterinary importance

• Mites: 45,000 described species!

Ixodes scapularis

• Blacklegged tick, deer tick

• Transmits Lyme disease, babesiosis, ehrlichiosis

• Found on eastern and north central United States

• Feed on wide variety of mammals and birds

Dermacentor variabilis and D. andersoni

• Dog tick, wood tick• Vector of Rocky

mountain spotted fever, tularemia

• Widely distributed, common

• Adults feed on dogs, other medium to large mammals; larvae/nymphs feed on small rodents

Amblyomma americanum

• Lone star tick• Vector of human

monocytic ehrlichiosis, STARI

• Widely distributed in southeastern US, Atlantic Coast

• Wide host range

Soft Ticks

• Take brief (< 30 minute) blood meals at night

• Vector of tick-borne relapsing fever

• Widely distributed• Wide host range • Live in burrows,

caves, nests Soft tick, Carios (Ornithodorus) kelleyi

Scientific Name Common Name Notes

Ixodes pacificus Western blacklegged tick

Lyme disease

Ixodes cookei Woodchuck tick Powassan virus

Rhipicephalus sanguineus

Brown dog tick Tick infestations

Dermacentor albipictus

Winter tick Large animals; hunters

Other ticks of public health importance

Tick-borne Diseases in the US

Selected vector-borne diseases, United States, 2001-2005

0

5000

10000

15000

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25000

2001 2002 2003 2004 2005

Cas

es r

epo

rted

Lyme disease HGE HME RMSF West Nile virus

Lyme Disease

• Identified in 1976

• Caused by Borrelia burgdorferi

• Transmitted by Ixodes scapularis and I. pacificus ticks

• Reservoirs include small mammals and birds

• Deer enhance tick populations, not a reservoir

2-year cycle of Lyme disease

Symptoms of Lyme Disease

From: Nadelman RB, Wormser GP. Erythema migrans and early Lyme disease. Am J Med 1995; 98(suppl 4A): 15S-24S.

Erythema migrans

• Occurs in 60-80% of cases

• ~7-14 days after tick bite

• Expands over days

• Rarely painful, puritic

Lyme disease cases reported to CDC,United States, 1992-2005

0

5,000

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1992 1994 1996 1998 2000 2002 2004

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es

Reported Lyme disease cases by age and sex—United States, 2003-2005

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0-4 5-9 10-14

15-19

20-24

25-29

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75-79

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Age (years)

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es

Male

Female

Percent of reported Lyme disease cases by month of onset, U.S., 2003-2005

Lyme disease incidence by county, 1997

Legend

Legend

Lower48_counties

1997LDcountyincidence.RATE97

0.00 - 9.99

10-49

50-99

100-199

200-499

500+

Incidence per 100,000 persons

Reported Lyme disease incidence by county of residence—United States, 2005

Lyme disease incidence by county, 2005

Lyme disease incidence by county, 1997Lyme disease incidence by county, 2005

Lyme disease incidence by county, 1997

Legend

Legend

Lower48_counties

1997LDcountyincidence.RATE97

0.00 - 9.99

10-49

50-99

100-199

200-499

500+

Incidence per 100,000 persons

1997 2005

Lyme disease high incidence counties, Northeastern United States

Lyme Disease – Emergence

Source: http://biology.usgs.gov/luhna/harvardforest.html

Source:Source: http://rockpiles.blogspot.com/2006_05_21_archive.htmlhttp://rockpiles.blogspot.com/2006_05_21_archive.html

“In Connecticut, the number of deer has increased from about 12 in 1896 to 76,000 today.” [Kirby StaffordConnecticut Agriculture Experiment Station]

Reforestation, Deer Populations, and Lyme Disease Expansion

The Lyme disease incidence is rising due to…– Overabundant deer

populations

– Increased numbers of ticks

– Expansion of suburbia into wooded areas

– Increased exposure opportunities

Source: K. Stafford, CAES

Southern Tick-associated Rash Illness (STARI)

• Causes rash similar to that of Lyme disease

• Transmitted by Amblyomma americanum

• Southeastern and south-central United States

Photo: Wormser et al CID 2005

Rocky Mountain Spotted Fever (RMSF)

• Caused by Rickettsia rickettsii

• Transmitted most commonly by Dermacentor variabilis and D. andersoni

• 250-1200 cases/year in United States

Incidence of RMSF in the United States

Age distribution of RMSF in the United States

RMSF: Signs and Symptoms

• Symptoms– Fever, chills, headache,

malaise, myalgias– Rash appears on day 3-

5• Maculopapular and

petichial – 1st on extremities

• Untreated mortality 20%; treated mortality 3-5%

Early (macular) rash on sole of foot

Late (petechial) rash on palm/forearm

Ehrlichiosis (Anaplasmosis)

Ehrlichia chaffeensis (Human Monocytic Ehrlichiosis)– Transmitted by Amblyomma americanum– Southeastern and south central United States

E. ewingii– Rare, immunosuppressed patients– Few cases in central United States

E. phagocytophila (Human Granulocytic Ehrlichiosis)– Approximately 1200 cases per year in United States– Northeast, upper mid-Western United States– Transmitted by Ixodes scapularis and I. pacificus

Ehrlichiosis (Anaplasmosis)

• Ehrlichia chaffeensis (Human Monocytic Ehrlichiosis, HME)

– Transmitted by Amblyomma americanum– Southeastern and south central United States

• E. phagocytophila (Human Granulocytic Ehrlichiosis, HGE)

– Approximately 1200 cases per year in United States– Northeast, upper mid-Western United States– Transmitted by Ixodes scapularis and I. pacificus

• E. ewingii– Rare, immunosuppressed patients– Few cases in central United States

Distribution of 3 Tick Species for HME and HGA

Ixodes scapularis

Ixodes pacificus

Amblyomma americanum

Overlapping distribution (I. Scapularis and A. americanum)

Reported annual incidence of HME and HGE

Clinical Presentation of Human Ehrlichioses

Signs and symptoms• Fever• Malaise• Headache• Myalgia/Arthralgia• Anorexia• Chills/Sweating• Nausea/Vomiting• Rash • Cough • Diarrhea• Abdominal pain

Severe clinical spectrum• Disseminated intravascular

coagulation• Pancytopenia• Encephalitis• Meningitis• Pulmonary Infiltrates• Gastrointestinal bleeding• Respiratory failure• Renal failure• Fatalities

Babesiosis

• Caused by Babesia microti• Transmitted by Ixodes scapularis• Reservoir in white-footed mice• Northeastern and mid-Western US• Rare, few cases each year• Clinically more severe in

immunocompromised and elderly

Tularemia

• Caused by bacterium, Franciscella tularensis• Transmitted by:

– Tick (Dermacentor variabils, D. andersoni, Ambloymma americanum) or deerfly bite

– handling infected sick or dead animals– eating or drinking contaminated food or water– inhaling airborne bacteria

• 200 cases per year in United States• Most cases in south-central and western

United States• Symptoms dependent on the route of infection

Tick-borne Relapsing Fever(TBRF)

• Caused by Borrelia hermsii, B. parkeri, B. turicatae

• Transmitted by Ornithodoros spp. soft ticks• Ticks feed quickly and painlessly at night• Rodents are primary reservoirs• Sporadic cases in the western U.S. (~25/year)• Associated with rustic cabins, high altitude• Recurrent fevers

Reported Cases of Tick Borne Relapsing Fever by County-- United States, 1990-2000

Number of Cases:

Arizona 11

California 82

Colorado 30

Idaho 19

Nevada 13

New Mexico 4

Oregon 3

Texas 18

Utah 6

Washington 60

Wyoming 1

Tick Paralysis

• Caused by toxin produced by Dermacentor ticks

• Acute, ascending, flaccid paralysis• Reversed upon removal of tick• May result in death if tick is not removed• More frequent in young girls

Courtesy of CDPHE

Treatment of tick-borne diseases

Disease Antibiotic

Lyme disease Tetracyclines, penicillins

STARI

Rocky Mountain Spotted Fever Doxycycline

Babesiosis Clindamycin + quinine sulfate /azithromycin + atovaquone

Ehrlichiosis Doxycycline

Tularemia several

Tick-borne Relapsing Fever Tetracyclines, erythromycin

Tick Testing and Tick Bite Prophylaxis

• Neither generally recommended following tick bites

• For Lyme disease, tick bite prophylaxis (single 200 mg dose doxycycline) recommended only when:– Tick reliably identified and attached for ≥ 36 hours– Can be started w/in 24 hours– Infection rate ≥ 20%– Doxycycline not contraindicated

• Always monitor site of tick bite and health closely following a tick bite

Tick Attachment, Engorgement, and Spirochete Transmission

Vaccination against tick-borne diseases

• Vaccine for Lyme disease removed from market in 2002

• Vaccines not available for other tick-borne diseases

Proper Tick Removal

• Use fine-tipped tweezers to grasp tick close to skin

• Pull tick’s body away from skin (avoid crushing head)

• Clean skin with soap and water

• Properly dispose of tick

DON’T: use petroleum jelly, a hot match, nail polish, or other products to remove a tick.

Mites

Family Trombiculidae:Chiggers

• Eastern US; most common in southern states

• Larvae attach to skin for 4-6 days

• Cause intense itching and dermatitis

• Chigger mites can vector scrub typhus

http://mdc.mo.gov/nathis/arthopo/chiggers/

Scabies

• Scabies or Itch mite, Scarcoptes scabei

• Close contact/crowded conditions

• Female mites burrow into skin and lay eggs, larvae return to surface to molt

• Finger webs, folds of wrists, bends of elbows/knees

Other Mites Causing Dermatitis

• Many species cause dermatitis:– Chicken Mite– Northern fowl mite– Tropical rat mite– House mouse mite– Grain mite– Straw itch mite

• Cause intense itching and irritation

• Infestations common after floods, rat/bird control

Ornithonyssus bacotiTropical Rat Mite

Suspected Mite Dermatitis

Images: L.H. Gould, 2005

House Dust Mites

• Allergen-symptoms include sneezing, itchy, watery eyes, runny nose, respiratory problems, eczema and asthma

• Require damp environment

• Feed on dander• “Dust control”

http://creatures.ifas.ufl.edu/urban/house_dust_mite_fig1.htm

Useful Resources

• http://www.cdc.gov/ncidod/diseases/submenus/sub_lyme.htm

• http://www.cdc.gov/ncidod/dvbid/lyme/ld_resources.htm– Tick Management

Handbook– IDSA Guidelines for

Lyme Disease treatment

Tick Management Handbook A integrated guide for homeowners, pest control operators, and public health officials for the prevention of tick-associated disease

Prepared by: Kirby C. Stafford III Chief Scientist The Connecticut Agricultural Experiment Station, New Haven

Produced as part of the Connecticut community-based Lyme disease prevention projects in cooperation with the following Connecticut health agencies: The Connecticut Department of Public Health The Westport Weston Health District The Torrington Area Health District The Ledge Light Health District

Funding provided by

The Centers for Disease Control and Prevention

The Connecticut Agricultural Experiment Station

Additional information

Division of Vector-Borne Infectious DiseasesNational Center for Zoonotic, Vector-Borne, and Enteric DiseasesCenters for Disease Control and Prevention3150 Rampart RoadFort Collins, Colorado, 80522

Telephone: (970) 221-6400Fax: (970) 221-6476Email: dvbid@cdc.gov

Images (if not noted): http://phil.cdc.gov/phil/home.asp

The findings and conclusions in this presentation are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.