Georgia epidemiology report, Vol. 23, no. 4 (Apr. 2007)

April 2007

volume 23 number 04

Diagnostic Testing for Rocky Mountain Spotted Fever:

Unraveling the Uncertainty

Introduction Georgia is endemic for Rocky Mountain spotted fever (RMSF), a tickborne disease of varying presentation and severity. Often, non-specific clinical presentation and lack of known tick bite make diagnosis difficult. Patients initially present with a nonspecific flu-like illness of 3 or 4 days duration, with no classical diagnostic signs and symptoms. Beyond the challenge of recognizing a case based on clinical manifestation and history of tick exposure, there is confusion about which diagnostic tests to order and how to interpret the results. Not all available tests are appropriate for confirmation of RMSF, and timing of tests should be considered in their interpretations.
Clinical Presentation Rocky Mountain spotted fever is characterized by fever (usually over 102F), headache (sometimes severe), and a maculopapular or petechial rash that begins at the extremities (characteristically involving the palms and soles) and spreads to the trunk. Malaise, myalgias, nausea, vomiting, abdominal pain, and conjunctivitis are also common. However, the classic diagnostic triad of fever, rash, and history of tick exposure is present in only a very small proportion of patients during the first three days of illness, when patients are likely to first seek medical care (1). Additionally, only 88% of patients eventually develop a rash, so absence of rash should not rule out the diagnosis of RMSF (1). Rash may be difficult to observe with darker skin tones. Severe complications include disseminated intravascular coagulation, adult respiratory distress syndrome, skin necrosis, renal impairment, hypotension, altered mental status, myocarditis, seizures, coma, and even death. Differential diagnoses include gastroenteritis, measles, scarlet fever, ehrlichiosis, Lyme disease, leptospirosis, meningococcemia, Epstein-Barr virus infection, cytomegalovirus infection, toxic shock syndrome, and bacterial sepsis. In the absence of proper and timely therapy, the RMSF mortality rate exceeds 20% and death can occur within 8 to 15 days of onset (2).
Treatment Doxycycline is the treatment of choice for all patients with RMSF, including young children. Chloramphenicol is appropriate for treatment of RMSF when tetracyclines are contraindicated (as in pregnancy), but studies have shown that patients treated with chloramphenicol are more likely to die from RMSF than those treated with a tetracycline (3). An infectious disease consult may be necessary, as chloramphenicol is unavailable in oral form in the United States and can cause severe adverse effects. Treatment

should continue for 7 to 10 days, or at least 3 days after fever subsides. Empiric therapy is indicated for any patient suspected of having RMSF, but prophylactic treatment after a tick bite before symptoms develop is not recommended (4). Treatment should never be delayed while awaiting development of a rash or laboratory results; delay in treatment has been associated with severe and fatal cases (4).
Laboratory Testing Testing for RMSF is not indicated in the absence of a compatible clinical syndrome. A presumptive diagnosis can be made and treatment given based on clinical and epidemiologic findings without waiting for laboratory results. A confirmed diagnosis cannot be made without supporting laboratory results. Cases diagnosed without laboratory findings do not meet the national surveillance case definition and are not included in public health statistics.
The most commonly used serologic method, and the gold standard for diagnosing RMSF, is the IgG indirect fluorescence antibody (IFA) test on paired sera taken 3 weeks apart. The first serum specimen should be collected upon first presentation to a healthcare provider (during the first week of illness). This may be tested immediately, but the first specimen is often negative and thus uninformative. Alternatively, this specimen should be appropriately stored (refrigerated at 4C or frozen in a non-frostfree freezer) until 3 weeks later when the second serum specimen is drawn. Both specimens can be sent together to the laboratory for IgG testing by IFA. It is sometimes necessary to send a third sample taken 6 weeks after disease onset to demonstrate seroconversion. A single negative acute specimen does not rule out RMSF, but is often misinterpreted as such, and in these cases a second specimen is never drawn. Sending both specimens together eliminates this propensity and the two sera can be assayed at the same time, eliminating interassay variation that can provide misleading results. Another note is that convalescent specimens drawn several weeks or months following recovery are not useful, thus every attempt must be made to collect them in a timely manner.
Other widely available tests include IgM antibody testing by IFA or enzyme-linked immunosorbent assay (ELISA) for IgM or IgG. We do not recommend IgM testing for rickettsial diseases, especially in the absence of IgG testing, as false positives and false negatives are common. Unlike viral testing, the IgM test

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does not provide earlier detection of antibodies to rickettsiae as IgM and IgG antibodies develop around the same time and can both be negative in the first week of illness. In addition, IgM antibodies can remain elevated for many weeks or months, so detection of IgM antibodies cannot be used to signify etiology of an acute illness. In recent years, use of an ELISA test for IgG or IgM has become more commonly employed by large commercial laboratories. The ELISA tests currently available are qualitative tests, and although results are reported as a number, they can only be interpreted as "positive", "equivocal", or "negative". Therefore, convalescent testing is unable to show a 4-fold change as required for confirmation of RMSF. Furthermore, the ELISA tests have not been adequately validated on a sufficient number of samples. Once they have been validated, they may still only be appropriate for use as a screening tool as the results are qualitative, not quantitative. Then those screened positive by ELISA should be tested by IFA to determine a relative level of anti-rickettsial antibodies.
For patients with rash who have not begun antibiotic therapy, acute diagnosis is achievable by use of polymerase chain reaction (PCR) assay of a skin punch biopsy from the rash site. Immunohistochemistry (IHC) may also be used to demonstrate the organisms within the endothelium of affected tissues. If the patient does not have a rash, these tests are not useful. PCR and IHC are also confirmatory on autopsied tissues of the lung,
Important Things You Did Not Know About RMSF Very few RMSF cases (3%) have fever, rash, AND history of tick bite upon first presentation to a healthcare provider. Many RMSF cases never develop a rash, so absence of rash does NOT rule out RMSF. Empiric antibiotic therapy is the rule for anyone suspected of having RMSF. Never wait for lab results! Prophylactic antibiotic therapy is NOT recommended after a tick bite in the absence of tickborne disease symptoms. Doxycycline is the antibiotic treatment of choice, even in young children. Pharyngitis is a sign of possible RMSF; the patient has the rash in his/her throat. Doctors have misdiagnosed this as strep throat and people have died as a result.

Key Points about Laboratory Testing Order IgG IFA testing. IgM tests provide presumptive, never confirmatory, evidence of infection and should be interpreted as such. Serologic testing MUST occur among paired sera, 3 weeks apart. This has been the gold standard for many years and works well. The best test to diagnose an acutely ill RMSF patient at the time of presentation is PCR of a rash biopsy. Paired serologic tests should accompany any adjunct testing.
liver, spleen, kidney, brain, whole blood, or skin from patients who have died of presumptive RMSF. PCR and IHC are not widely available, but can be arranged by contacting GDPH at 404-657-2588.
How to Report a Case of RMSF The national surveillance case definition has undergone revision in recent years, and will likely be modified to address laboratory diagnostic issues again in the near future. The surveillance case definition is a tool used by Public Health to capture actual cases of disease while excluding as many non-cases as possible. This case definition should not be used to diagnose individual patients. RMSF is reportable to Public Health within 7 days of diagnosis. To report a case electronically, log on to Georgia's State Electronic Notifiable Disease Surveillance System (SENDSS) at http://sendss.state.ga.us. Alternatively, complete a Notifiable Disease Report Form (form 3095) and mail to your County Health Department, District Health Office, or State Health Office. When reporting cases of RMSF, be sure to include clinical signs and symptoms in addition to laboratory results, as clinical compatibility is a requirement of the surveillance case definition.
References 1. Helmick CG, Bernard KW, D'Angelo LJ. Rocky Mountain
spotted fever: clinical, laboratory, and epidemiological features of 262 cases. The Journal of Infectious Diseases 1984;150:480-488. 2. Stallings SP. Rocky Mountain spotted fever and pregnancy: a case report and review of the literature. Obstetrical and Gynecological Survey 2001;56:37-42. 3. Holman RC, Paddock CD, Curns AT, et al. Analysis of risk factors for fatal Rocky Mountain spotted fever: evidence for superiority of tetracyclines for therapy. The Journal of Infectious Diseases 2001;184:1437-44.

Division of Public Health http://health.state.ga.us
Stuart T. Brown, M.D. Director
State Health Officer

Epidemiology Branch http://health.state.ga.us/epi
Susan Lance, D.V.M., Ph.D. Director
State Epidemiologist

Georgia Epidemiology Report Editorial Board
Carol A. Hoban, M.S., M.P.H. Editor Kathryn E. Arnold, M.D.
Cherie Drenzek, D.V.M., M.S. Susan Lance, D.V.M., Ph.D.
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Two Peachtree St., N.W. Atlanta, GA 30303-3186 Phone: (404) 657-2588
Fax: (404) 657-7517

Georgia Department of Human Resources
Division of Public Health

Please send comments to: gaepinfo@dhr.state.ga.us

4. O'Reilly M, Paddock C, Elchos B, et al. Physician knowledge of the diagnosis and management of Rocky Mountain spotted fever. Annals New York Academy of Sciences 2003;990:295-301.
Recommended Reading 1. CDC. Diagnosis and management of tick-borne rickettsial
diseases: Rocky Mountain spotted fever, ehrlichioses, and anaplasmosis--United States: a practical guide for physicians and other health-care and public health professionals. MMWR 2006;55(No.RR-4): 1-29. http://www.cdc.gov/ mmwr/preview/mmwrhtml/rr5504a1.htm 2. Crump JA, Corder JR, Henshaw NG, and Reller LB. Development, implementation, and impact of acceptability criteria for serologic tests for infectious diseases. J. Clin. Microbiol. 2004;42: 881-883. 3. Lennette, EH, Lennette DA, and Lennette ET, eds. Diagnostic procedures for viral, rickettsial, and chlamydial infections, 7th ed. American Public Health Association: Washington, D.C. 1995. [Earlier editions give authoritative and often more detailed explanations of the rickettsial testing methods.]
Written by: Laurel E. Garrison, M.P.H. and William L. Nicholson, Ph.D.*
*The findings and conclusions are those of the authors and do not necessarily
represent the views of the Centers for Disease Control and Prevention.
Tick Surveillance Notes: Rickettsia rickettsii in Rhipicephalus sanguineus Ticks from Gordon County
Rickettsia rickettsii, the agent of Rocky Mountain spotted fever (RMSF), is most commonly found in Dermacentor spp. ticks, specifically Dermacentor variabilis (the American dog tick) in Georgia. Although recognized as an efficient experimental vector, Rhipicephalus sanguineus (the brown dog tick) was not implicated as a vector of human disease in the United States until 2004 (1). This short communication is the first report of a R. rickettsii-infected Rh. sanguineus tick in Georgia.
In May 2005, tick dragging was conducted by the Georgia Division of Public Health in cooperation with the Northwest Georgia Health District and the Gordon County Health Department in response to a complaint of large numbers of ticks in a Gordon County homeowner's yard. The ticks were identified as Rh. sanguineus (the brown dog tick) and submitted to the Rickettsial Zoonoses Branch, Division of Viral and Rickettsial Diseases, Centers for Disease Control and Prevention for testing. Of eight adult ticks collected and preserved in isopropanol, one female and two male Rh. sanguineus tested positive for spotted fever group rickettsial DNA using a quantitative SYBR-Green PCR assay (2). One of the males was found to be infected with R. rickettsii by amplification and

restriction analysis of a 602-bp fragment of the rOmpA species specific rickettsial gene. The identity of the spotted fever group rickettsiae in the female and the other male tick was not determined due to a low copy number of rickettsial DNA in those ticks.
The importance of Rh. sanguineus ticks in the maintenance and transmission cycles of R. rickettsii in Georgia is unknown. In general, R. rickettsii prevalence in the expected vector, D. variabilis, is <1%. However, in Gordon County, prevalence in Rh. sanguineus was 12.5%, which is quite high. Gordon County experienced an unusually high number of RMSF cases in 2005 (n=7), which can be at least partially attributed to a fatal RMSF case in a Gordon County child that year resulting in increased awareness and testing. Whether Rh. sanguineus ticks played a part in this increase is unknown. Rhipicephalus sanguineus ticks are characterized by their tendency to create large infestations in areas frequented by dogs. If you suspect RMSF in a dog owner who describes a large tick infestation in their yard, please call the Georgia Division of Public Health at 404-657-2588.
Acknowledgements Special thanks to Debra Abercrombie and Tim Allee of the Northwest Georgia Health District and Christy Blair of the Gordon County Health Department for their assistance with the investigation.
References 1. Demma LJ, Traeger MS, Nicholson WL, et al. Rocky
Mountain spotted fever from an unexpected tick vector in Arizona. N. Engl. J. Med. 2005;353:587-94. 2. Eremeeva ME, Dasch GA, and Silverman DJ. Evaluation of SQ-PCR, an assay for quantitation of Rickettsia rickettsii and closely-related spotted fever group rickettsiae. J. Clin. Microbiol. 2003;41: 5466-5472.
Written by: Laurel E. Garrison, M.P.H.; Rosmarie Kelly, Ph.D.; William L. Nicholson, Ph.D.* and Marina E. Eremeeva M.D., Ph.D., Sc.D.*
*The findings and conclusions are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.
Notice: End of Tick Attach Study
The Tick Attach Study was conducted by the Georgia Division of Public Health (GDPH), the University of Georgia, and the Georgia Poison Center between April 2005 and December 2006. Moving forward, GDPH cannot accept ticks for testing except in rare cases (call 404-657-2588 for more information). However, we can identify ticks. Instructions for submitting a tick for identification can be found on our website at http://www.health.state.ga.us/epi/vbd/tick.asp. There is a short form (PDF) that should be completed and sent with the tick. Thanks to all who contributed ticks to the Tick Attach Study. Look for study results in an upcoming Georgia Epidemiology Report.

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The Georgia Epidemiology Report Epidemiology Branch Two Peachtree St., NW Atlanta, GA 30303-3186

PRESORTED STANDARD U.S. POSTAGE
PAID ATLANTA, GA PERMIT NO. 4528

April 2007

Volume 23 Number 04

Reported Cases of Selected Notifiable Diseases in Georgia, Profile* for January 2007

Selected Notifiable Diseases
Campylobacteriosis Chlamydia trachomatis Cryptosporidiosis E. coli O157:H7 Giardiasis Gonorrhea Haemophilus influenzae (invasive) Hepatitis A (acute) Hepatitis B (acute) Legionellosis Lyme Disease Meningococcal Disease (invasive) Mumps Pertussis Rubella Salmonellosis Shigellosis Syphilis - Primary Syphilis - Secondary Syphilis - Early Latent Syphilis - Other** Syphilis - Congenital Tuberculosis

Total Reported for January 2007
2007 37 3930 16 1 37 1540 13 10 10 2 0 3 0 3 0 113 90 2 7 6 17 0 27

Previous 3 Months Total

Ending in January

2005

2006 2007

122

98

107

7946

9087

9877

21

47

51

7

1

3

212

162

124

3936

4351

4433

42

32

39

41

12

16

113

35

34

7

9

12

0

1

1

7

5

8

0

1

0

15

8

7

0

0

0

334

341

376

129

193

437

34

30

15

137

117

52

66

97

37

219

227

108

1

2

1

133

113

108

Previous 12 Months Total

Ending in January

2005 2006

2007

586

592

578

34356

34181

39096

172

166

284

25

28

45

911

723

676

16026

16259

19281

125

107

121

287

116

58

444

177

186

45

38

39

10

7

7

16

14

21

2

2

4

34

47

29

1

0

0

1933

1953

1906

630

701

1422

122

131

105

498

526

399

373

415

300

887

983

833

6

4

7

531

494

510

* The cumulative numbers in the above table reflect the date the disease was first diagnosed rather than the date the report was received at the state office, and therefore are subject to change over time due to late reporting. The 3 month delay in the disease profile for a given month is designed to minimize any changes that may occur. This method of summarizing data is expected to provide a better overall measure of disease trends and patterns in Georgia.
** Other syphilis includes latent (unknown duration), late latent, late with symptomatic manifestations, and neurosyphilis.

Report Period Disease Classifi- Total Cases Reported*

cation

<13yrs

>=13yrs

AIDS Profile Update

HIV/AIDS UPDATE (by Date of Report)

Total

Percent Female

Risk Group Distribution

MSM

IDU

MSM&IDU HS

Unknown

Perinatal

Race Distribution White Black

Hispanic Other

Latest 12

HIV, non-AIDS 17

2,924

2,941

45

31

8

2

16

42

0

21

74

4

1

Months**:

3/06-2/07

AIDS

10

2,090

2,100

28

33

8

2

13

44

0

22

72

6

<1

Five Years Ago: HIV, non-AIDS -

-

-

-

-

-

-

-

-

-

-

-

-

-

3/02-2/03

AIDS

2

1,583

1,585

26

39

9

3

16

32

-

20

74

5

1

Cumulative: HIV, non-AIDS 243

10,079

10,322

34

30

8

3

12

47

2

22

74

3

1

07/81-2/07

AIDS

274

36,366

36,640

20

44

15

5

14

21

0

31

66

3

<1

Yrs - Age at diagnosis in years

MSM - Men having sex with men

IDU - Injection drug users

HS - Heterosexual

* Case totals are accumulated by date of report to the Epidemiology Section ** Due to a change in the surveillance system, case counts may be artificially low during this time period

***HIV, non-AIDS was not collected until 12/31/2003
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