Tickborne diseases in the Southeastern U'S'

1
Tick-borne diseases in the Southeastern U.S.
Charles S. Apperson Dept. of Entomology North
Carolina State University
2
Tick-Borne Diseases Reported TO cdc

• Rocky Mountain Spotted Fever
• Human Monocytic Ehrlichiosis
• Human Granulocytic Anaplasmosis
• Lyme Disease
• Tularemia

TICK-BORNE DISEASES NOT REPORTED TO CDC

• Southern Tick Associated Rash Illness (STARI)

3
Tick-borne illness appears to be increasing
Tick-borne Infections USA 1999-2006
Year
2006
19,931
2288
646
578
1455
169
Includes HGA, HME, and other or unspecified
ehrlichiosis HGAhuman granulocytic anaplasmosis
(formerly human granulocytic ehrlichiosis)
4
RMSF Cases and Incidence Reported by NETSS,
20002005
2500
8
7
2000
6
5
1500
of Cases
Incidence per 1,000,000
4
1000
3
2
500
1
0
0
2000
2001
2002
2003
2004
2005
Year
Total Cases
Incidence per Year
5
RMSF Incidence ? Top Reporting States, 20012005
80
70
60
50
Incidence per 1,000,000
40
30
20
10
0
2001
2002
2003
2004
2005
Year
MO
TN
OK
NC
6
The highest incidence of RMSF was in North
Carolina, which reported 72 cases per million
population in 2005 -- a level ten times the
national incidence that year.
Cases per 1,000,000 population 2000-05
0.01-2.6
2.7-7.4
14.7-32.9
7.5-14.6
33
7
Rocky Mountain spotted fever in NC
Reported Cases of RMSF NC, 1998-2006
In 2005, NC reported one third of all RMSF cases
in US (625 of 1843).
8
RMSF reported in NC

• gt95 of cases are not laboratory confirmed
• Based on exposure, clinical symptoms and positive
  single acute serologic specimen.
• Difficult to obtain convalescent serology.
• Questions
• What is the true disease burden?
• What is the relative abundance of tick species in
  peri-domestic environments?
• What is the prevalence of R. rickettsii in ticks?
• Are new spotted fever group rickettsiae emerging
  as human pathogens?

9
Table 1. Numbers and life stages of tick species
collected by flagging vegetation on the home
grounds of residences (n 32) in Chatham County,
NC from April 9 to July 24, 2005.
From Apperson et al. 2008
10
Table 2. Results of PCR analyses of ticks
collected in Chatham County for selected
pathogens.
From Apperson et al. 2008
11
52 (12) 439 of tick pools were tested for
pathogens. Ticks testing positive were collected
at 16 different home sites.

• Ehrlichia chaffeensis
• 1 pool of 10 A. americanum males
• 1 pool of 1 D. variabilis female
• Anaplasma phagocytophilum
• 1 pool of 3 A. americanum males
• Rickettsia spp.
• R. amblyommii (5 different home sites)
• 11 pools containing 104 A. americanum ticks
• 2 pools containing 2 D. variabilis ticks
• R. rickettsii or montana
• 2 pools containing 4 D. variabilis ticks
• R. rickettsii or felis
• 1 pool containing 1 D. variabilis female tick
• Rickettsia spp.
• 4 pools containing 6 A. americanum ticks

From Apperson et al. 2008
12
Serologic test results

• Prospective surveillance for tick-borne illness
• 50 patients screened at NC State Lab
• Paired sera available for 28 patients
• 17 negative
• 5 confirmed HME
• 6 patients classified as probable RMSF

From Apperson et al. 2008
13
Table 3. Results of diagnostic tests of probable
RMSF patients. Values represent the reciprocals
of end-point dilutions giving strong fluorescence
in IFA tests.
T1 date of onset to acute serum sample. T2
date of acute to convalescent serum sample.
From Apperson et al. 2008
14
Is R. amblyommii a cause of rickettsiosis
reported as RMSF?

• Strong circumstantial evidence says maybe.
• Need to further investigations of clinically ill
  patients to specifically implicate agent
• Culture and molecular evaluation of skin biopsy
  samples of rashes
• Consider other SFG rickettsiae, such as R.
  parkeri .

Other conclusions HME is likely to be grossly
under-reported.
15
Source http//www.cdc.gov/mmwr/PDF/ss/ss5710.pdf
16
Lyme disease cases reported to CDC
17
Lyme Disease Cases in Maryland 1990 - 2007
Graph by S.B. Wee, Maryland Department of Health
Mental Hygiene
18
Lyme disease in Virginia during a 19 year period
since the inception of case surveillance in 1989
Source Dr. David Gaines, VA Dept. of Health
19
Source VA Dept. of Health, Div. Environ. Epi.
Zoon. Dis. Newsletter, Vol. 2 (1), 2009
20
Are population dynamics and host seeking behavior
of Ixodes ticks changing in the south?
21
Tick vector(s) collected at VA cases sites

• Amblyomma americanum all stages (very abundant)
• Dermacentor variabilis adults (uncommon to
  rare)
• Ixodes scapularis nymphs (exceedingly rare to
  usually not collected)

22
Table 6. Results of qPCR analyses of Ixodes
scapularis and Dermacentor variabilis for
bacterial pathogens in ticks collected in Chatham
County, NC in 2006.
Smith et al., unpublished
23
Enzootic Lyme disease does occur in the southern
US

• US Navy and NC state entomologist have recently
  collected Ixodes affinis adults at geographically
  separated sites.
• Oliver and coworkers at Georgia Southern
  University have documented enzootic transmission
  of B. burgdorferi in Georgia (Oliver et al. 2003.
  PNAS 10011642-11645).
• A southern isolate of Borrelia burgdorferi s. l.
  has not been cultured from humans

24
Field-based eco-epidemiology studies provide a
foundation for disease prevention

• Physician-based cohort studies of patients
  presumptively diagnosed with a tick-borne
  illness.
• Clinical specimens for pathogen evaluation by
  culture and molecular methods.
• Ecological studies of the interaction of ticks
  and wildlife.