Biology of Ticks and Mites L. Hannah Gould, MS, PhD Bacterial Diseases Branch Division of Vector-Borne Infectious Diseases Centers for Disease Control and Prevention Fort Collins, CO
Jan 15, 2016
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
20000
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
10,000
15,000
20,000
25,000
1992 1994 1996 1998 2000 2002 2004
Year
Cas
es
Reported Lyme disease cases by age and sex—United States, 2003-2005
0
500
1000
1500
2000
2500
3000
3500
4000
0-4 5-9 10-14
15-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
70-74
75-79
80-84
85-89
90+
Age (years)
Cas
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: [email protected]
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.