Emerging Tick-borne Diseases of the Southern United States

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Emerging Tick-borne Diseases of theSouthern
United States

• William H. Dees1, Richard G. Robbins2
• and Jerome Goddard3
• 1McNeese State University, Lake Charles, LA
• 2Armed Forces Pest Management Board, Washington,
  DC
• 3Mississippi State Department of Health, Jackson,
  MS

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Abstract

• A review of the scientific literature published
  over the last ten years indicates that at least
  nine tick-borne diseases occur in the southern
  United States. A tenth disease, Q fever caused
  Coxiella burnetii, is not thought to be
  transmitted by ticks in the American South. All
  ten pathogens are briefly described herein,
  together with their principal vectors. This
  presentation was originally given in poster form
  at the 35th Annual Conference of the Society for
  Vector Ecology, Coeur dAlene, Idaho, 5-8 October
  2003.

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States of the Southern United States
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Tick-borne Diseases of the South

• Babesiosis
• Babesia microti
• Other Babesia spp. possibly associated with human
  infection continue to be discovered
• Borreliosis
• Borrelia burgdorferi (Lyme Disease - LD)
• B. lonestari (Southern Tick-Associated Rash
  Illness - STARI)
• B. turicatae (Tick-Borne Relapsing Fever - TBRF)
• Other Borrelia spp./strains possibly associated
  with human infection continue to be discovered
• Ehrlichiosis
• Ehrlichia chaffeensis
• Human Monocytic Ehrlichiosis (HME)
• E. ewingii/others
• Human disease/nonspecific

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• Anaplasma phagocytophilum
• Human Granulocytic Ehrlichiosis (HGE)
• Q Fever
• Coxiella burnetii
• Rickettsiosis
• Rickettsia rickettsii (RMSF)
• Other Rickettsia spp. possibly associated with
  human infection continue to be discovered
• Tularemia
• Francisella tularensis
• Affliction - Tick Paralysis

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• Babesiosis
• Protozoan parasite of red blood cells
• Babesia microti has been reported in Missouri
  (edge of Southern U.S.).
• Most infections are asymptomatic, although
  babesiois is a potentially fatal disease.
• Vector
• Ixodes scapularis
• Related disease agents
• Babesia canis in dogs Southern U.S.
• Babesia gibsoni in dogs Southern U.S.
• Babesia equi in horses FL

CDC
CDC
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• Lyme Disease (LD)
• Bacterium
• Borrelia burgdorferi
• Most cases reported from Northeast, Mid-Atlantic
  and North-Central U.S., although additional
  genetically varied strains and tick vectors may
  occur in the South.
• Has a high potential transmission rate.
• Principal vector
• Ixodes scapularis
• Secondary or potential vectors include
• Other Ixodes spp.
• Amblyomma spp.
• Dermacentor spp. (OK)

CDC
CDC
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Figure 1. Lyme Disease in TX and OKfrom MMWR1,
CDC21MMWR Morbidity and Mortality Weekly
Report2CDC Centers for Disease Control and
Prevention
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• Figure 1 shows fluctuations in the numbers of
  LD cases over the last ten years. The number of
  cases in TX ranged from 32 to 97 per year. OK
  reported a decrease in the number of cases.
  False-positive test results and over-diagnosis
  may have resulted in the increased numbers from
  1994-1997. Since 1998, only a few cases (lt13)
  have been reported in OK.

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Figure 2. Lyme Disease in Southeastern U.S.from
MMWR1, CDC21MMWR Morbidity and Mortality
Weekly Report2CDC Centers for Disease Control
and Prevention
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• Figure 2 shows fluctuations in the numbers
  of LD cases over the last ten years. Last years
  (2002) data indicate an increase in LD cases.
  This increase is due to the unusually large
  number of cases reported from NC and FL. NC
  reported 137 cases, which is almost half the
  cases shown for 2002 and is over three times the
  number of cases reported by NC in 2001. FL
  reported 81 cases, twice the number reported in
  2001. In light of the fact that immature Ixodes
  scapularis in the Southeast frequently feed on
  lizards and skinks, it is suspected that many of
  these cases are actually imports from other areas
  of the country, especially the Northeast.

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• Southern Tick-Associated Rash Illness (STARI)
• Bacterium
• Borrelia lonestari (?)
• Shows symptoms similar to Lyme disease.
• B. lonestari and closely related Borrelia species
  are present in nature in several southern states.
• Vector
• Amblyomma americanum
• found throughout the South
• Overall, the number one arthropod-borne disease
  of humans in the U.S. is Lyme disease, caused by
  Borrelia burgdorferi. However, this may not be
  the case in the southern states, where Borrelia
  lonestari and/or another undescribed
  Borrelia-like spirochete may cause borreliosis.

CDC
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Tick-borne Relapsing Fever

• Bacterium
• Borrelia turicatae
• Most cases reported from the Midwest and western
  U.S.
• Transmission by bite or coxal fluid.
• Vector
• Ornithodoros turicata (TX)

ForestryImages
James L. Occi
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• Ehrlichiosis
• Caused by at least three different agents.
• Recognized in U.S. since mid-1980s.
• Presents clinical features similar to Rocky
  Mountain spotted fever.
• Became notifiable by Centers for Disease Control
  and Prevention (CDC) in 1999.
• Bacterium
• Ehrlichia chaffeensis
• Described in 1987.
• Causes human monocytic ehrlichiosis (HME).
• States with the highest prevalence in the
  southern U.S. are AR, OK and TN.

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• Principal vector
• Amblyomma americanum
• Secondary vector
• Dermacentor variabilis

CDC
CDC
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• Bacterium
• Ehrlichia ewingii
• Causes nonspecific human disease.
• Thus far mostly reported in immuno-compromised
  individuals.
• Vectors
• Amblyomma americanum (also
  suspect Dermacentor variabilis
  and Rhipicephalus sanguineus (?))

CDC
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• Bacterium
• Anaplasma phagocytophilum
• Described in 1994.
• Causes human granulocytic ehrlichiosis (HGE).
• Vector
• Ixodes scapularis
• Potential vector
• Dermacentor variabilis

CDC
CDC
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• Q Fever
• Rickettsia
• Coxiella burnetii
• Cosmopolitan zoonotic disease, reported from
  various areas throughout the U.S.
• Primary reservoirs are cattle, sheep and goats.
• Typically acquired through inhalation of
  contaminated dust or debris.
• Ticks not major source of human infection in U.S.
• Recently reported in GA and TN however, unlikely
  that ticks were involved.
• Acute febrile disease. There is considerable
  variation in severity and duration. Some
  infections may present as fever of unknown
  origin (FUO).
• Declared a notifiable disease by Centers for
  Disease Control and Prevention in 1999 some
  states consider it not notifiable.

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• Rocky Mountain Spotted Fever (RMSF)
• Rickettsia
• Rickettsia rickettsii
• Most common fatal tick-borne disease in the U.S.
  
• Characterized by fever, myalgia, headache and
  rash.
• Despite name, RMSF is a disease of the South.
  Historically, NC and OK have accounted for about
  a third of all cases. Besides these two states,
  recent data indicate SC, TN and AR have the
  greatest numbers of cases.
• Seasonal outbreaks parallel activity of tick
  vectors.
• Delayed diagnosis and treatment are associated
  with increased risk of severe complications and
  death.
• Therapy should be initiated quickly if RMSF
  suspected, especially in patients presenting with
  fever, rash and history of tick exposure.

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• Vector
• Dermacentor variabilis
• Other ixodids possibly involved.
• Other Rickettsia spp. have been detected in
  Amblyomma americanum, A. cajennense, Ixodes
  scapularis, and Rhipicephalus sanguineus.

CDC
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Figure 3. RMSF in TX and OK from MMWR, CDC
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• Figure 3 shows fluctuations in the number of
  RMSF cases in TX and OK. In OK, the number of
  cases ranged from 29 to 62 per year. TX reported
  0-10 cases/year. In Oklahoma, recent studies
  (McQuiston et al. 2000) show the incidence of
  RMSF to be significantly higher in American
  Indians when compared to the overall population
  of that state.

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Figure 4. RMSF in Southeastern U.S.from MMWR,
CDC
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• Figure 4 shows a general increase in RMSF in
  the Southeast. In 2002, NC, SC and AR nearly
  doubled the number of reported cases from the
  previous year. Increasing suburban development
  in many parts of the Southeast may cause larger
  numbers of people to come into contact with
  vector ticks.

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• Tularemia
• Bacterium
• Francisella tularensis
• Acute plague-like zoonotic infection with a
  variety of clinical manifestations related to
  route of introduction and virulence of pathogen.
  
• Several ways of acquiring infection (food, water,
  aerosol).
• Natural transmission also occurs via tick bites.
  
• Can be fatal if it is not treated with
  appropriate antibiotics.
• Sporadic cases occur in all states in the U.S.
  In 2000, states with the highest prevalence in
  the southern U.S. were AR (23), OK (11), NC (2),
  TN (1)historically, TN has reported more cases,
  and GA (1).
• Within the last 2 years, lt25 cases were reported
  in any southern state.
• Incidence in the U.S. has declined substantially
  over the years. The Centers for Disease Control
  and Prevention removed tularemia as a notifiable
  disease in 1994, but reinstated it effective
  January 1, 2000, because of its potential as a
  bioterrorism agent.

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• Vectors
• Dermacentor variabilis
• Amblyomma americanum
• Potential vectors
• Almost any ixodid tick

CDC
CDC
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• Miscellaneous
• In TX in 2001, Houck et al. reported the first
  evidence of hantavirus-specific RNA (Bayou) from
  an unidentified adult ixodid tick collected from
  a hantavirus-positive cotton rat, Sigmodon
  hispidus.
• This does not necessarily mean that ticks can
  transmit hantavirus.
• The third author (J.G.) has found
  
  an unidentified trypanosome-like
  organism in
  hemolymph of
  Ixodes scapularis.

Suspected trypanosome 1,000X (Photo by JG)
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• Affliction - Tick Paralysis
• Acute, ascending, flaccid motor paralysis caused
  by a toxin in tick saliva.
• In 2000, tick paralysis was reported in a young
  girl in GA. The tick Dermacentor variabilis was
  found and removed. Within 24 hours, all signs
  and symptoms had fully resolved.
• The third author (J.G.) has investigated two bona
  fide cases in MS over the past decade.
• Affects both humans and other animals throughout
  the South.
• Principal tick species causing paralysis
• Dermacentor spp.
• Other ticks known to cause paralysis
• Ixodes spp.
• Amblyomma spp.
• Rhipicephalus spp.

CDC
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• Ticks Reported Biting Humans in the Southern U.S.
• Hard Ticks
• Amblyomma americanum - lone star tick
• A. cajennense - Cayenne tick
• A. imitator - imitator tick
• A. inornatum
• A. maculatum - Gulf Coast tick
• A. tuberculatum - gopher tortoise tick
• Boophilis annulatus - cattle tick
• Dermacentor variabilis - American dog tick
• Haemaphysalis leporispalustris - rabbit tick
• Ixodes brunneus
• I. cookei (vector of Powassan virus in NE U.S.)
• I. dentatus
• I. scapularis - blacklegged tick
• Rhipicephalus sanguineus - brown dog tick

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• Soft Ticks
• Argas miniatus - fowl tick
• Ornithodoros stageri
• O. turicata - relapsing fever tick
• Otobius megnini - spinose ear tick

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Selected References

• Barbour, AG. 1996. Does Lyme disease occur in the
  South? A survey of emerging tick-borne
  infections in the region. Am J Med Sci 311(1)
  34-40
• Dworkin MS, PC Shoemaker, CL Fritz, ME Dowell and
  DE Anderson, Jr. 2002. The epidemiology of
  tick-borne relapsing fever in the United States.
  Am J Trop Med Hyg 66(6)753-758
• Goddard, J. 2002. A ten-year study of tick biting
  in Mississippi Implications for human disease
  transmission. J Agromed 825-32
• Harrison, BA, BR Engber and CS Apperson. 1996.
  Ticks (AcariIxodida) uncommonly found biting
  humans in North Carolina. J Vector Ecol 22(1)
  6-12
• Houck, MA, H Qin and HR Roberts. 2001. Hantavirus
  transmission Potential role of ectoparasites.
  Vector Borne Zoonotic Dis 1(1) 75-79
• McQuiston, JH, RC Holman, AV Groom, SF Kaufman,
  JE Cheek and JE Childs. 2000. Incidence of Rocky
  Mountain spotted fever among American Indians in
  Oklahoma. Public Health Reports 115(5) 469-475
• McQuiston, JH, CD Paddock, RC Holman and JE
  Childs. 1999. The human ehrlichioses in the
  United States. http//www.cdc.gov/ncidod/eid/vol5n
  o5/ mcquiston.htm
• Merten HA and LA Durden. 2000. A state-by-state
  survey of ticks recorded from humans in the
  United States. J Vector Ecol 25(1) 102-113

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• Morbidity reports and summaries.
  http//www.cdc.gov/mmwr
• Tick and tick-borne diseases information.
  http//www.cdc.gov