HETA 92-0361-2343 NIOSH INVESTIGATOR:

AUGUST 1993 Thomas J. Van Gilder, M.D.

M-I DRILLING FLUIDS 

GREYBULL, WYOMING NCID INVESTIGATOR:

 Laura Robinson, D.V.M., M.S.

SUMMARY

In August 1992, the National Institute for Occupational Safety and Health (NIOSH) received a

request from the Wyoming Department of Health to evaluate two cases of acute, febrile

hepatitis among workers at a bentonite mine operated by M-I Drilling Fluids in Greybull,

Wyoming. Subsequent blood tests indicated that the hepatitis was caused by Coxiella burnetii,

the organism which causes Q fever. Q fever is a rickettsial disease, typically contracted by

humans through the inhalation of dust or other materials contaminated by infected animal

products. Q fever usually is manifested by fever, chills, muscle aches, and fatigue;

occasionally, hepatitis, pneumonia, or other more serious disease results from infection by C.

burnetii. For further information on Q fever, see appendix A.

From October 12-14, 1992, NIOSH representatives conducted a site visit to further

characterize the cases of Q fever. NIOSH investigators surveyed 

39 workers using a self-administered questionnaire and a blood test for antibodies to C.

burnetii. Seven workers had serologic evidence of infection with C. burnetii, three displaying

evidence of recent infection and four displaying evidence of past infection. Analysis of

questionnaire data showed that the major risk factor significant for recent infection was sheep

ownership. Risk factors suggestive of either recent or past infection included working

outdoors, operating heavy equipment, and hunting. 

As a comparison group, employees with similar demographic characteristics at a non-mining

worksite were also tested and found to have fewer cases of infection; one case of past infection

with C. burnetii was discovered. 

Recommendations included maintaining a high index of suspicion for Q fever in persons with

unexplained fever and influenza-like symptoms, hepatitis, or pneumonia; and reporting cases

of Q fever to the state epidemiologist by physicians. Other recommendations, based on

previous Q fever research, included avoiding contact with soil obviously contaminated with

animal urine, feces, or birth products, as well as animals, particularly sheep and cats, who are

giving birth. The last recommendation is directed in particular at pregnant women and persons

with valvular heart disease.

On the basis of data obtained in this investigation, NIOSH investigators determined that a

potential health hazard existed among employees working outdoors at the bentonite mining

facility. A non-occupational risk factor, sheep ownership, was found to be important. The

relative contribution of occupational and non-occupational risk factors could not be

assessed. Recommendations for reducing morbidity and mortality associated with Coxiella

burnetii infection include maintaining a high index of suspicion for Q fever in persons

presenting with pneumonia, hepatitis, or unexplained fever; and avoiding contact with soil

obviously contaminated with animal urine, feces, or birth products, as well as animals

giving birth.

KEYWORDS: SIC 1459 (bentonite mining); Wyoming bentonite; Q fever; Coxiella

burnetii; hepatitis, occupational, vector-borne

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports
Health Hazard Evaluation Report No. 92-0361 - Page 2

INTRODUCTION

In August 1992, the Wyoming Department of Health was notified of two cases of acute,

febrile, non-A, non-B, non-C hepatitis in two men in northwestern Wyoming. Despite the

hospitalization of one of the men and evaluation of the cases by an infectious disease

consultant, the workers did not receive a specific diagnosis. Both men worked at a bentonite

mine in Greybull, Wyoming, located about halfway between their respective homes. 

Suspecting a possible connection between the illness and the work site, the state

epidemiologist contacted the National Institute for Occupational Safety and Health (NIOSH),

requesting technical assistance in evaluating the potential occupational etiologies. After

telephone interviews with the ill workers, a review of the medical records, and a discussion of

the work site with the management, we requested that blood samples be sent for Q fever

antibodies. The initial Q fever antibody titers, run at an outside lab, were negative in one of

the workers and borderline in the other. Repeat samples were positive. NIOSH requested

assistance from the Centers for Disease Control and Prevention (CDC), National Center for

Infectious Disease (NCID), Division of Viral and Rickettsial Diseases (DVRD), Viral and

Rickettsial Zoonoses Branch (VRZB), and made a coordinated visit to Wyoming on

October 12, 1992.

BACKGROUND

Facility Description

The M-I Drilling Fluids facility consisted of the bentonite mine area, which covers a broad

area of open land that is also used for grazing, the mill or processing area, and a storage area. 

At the time of our visit, 58 workers were employed--23 in the mine area, 22 in the mill area,

and the rest in the office or lab areas.

Process Description

Bentonite is a naturally-occurring clay formed from volcanic ash. It has the property of being

highly absorbent. It is used as a drying agent, as an animal feed additive, and in a variety of

ointments. It is considered biologically inert. There are few reports of adverse reactions to it,

limited mainly to skin and eye irritation. Bentonite is mined in open pits. It is piled up in the

mine area, allowed to dry, and then transported to the processing and packaging areas. After

additional moisture is removed, the bentonite is ground and then loaded or bagged. 

EVALUATION PROCEDURES

Environmental

A tour of the facility, including a walking tour of the enclosed structures and a driving tour of

the main mine roads, was conducted to look for potential sources of C. burnetii, such as areas

in which workers might have come into contact with animals. Six soil samples were taken

from different sites throughout the mine area for analysis for C. burnetii by polymerase chain

reaction (PCR).
Health Hazard Evaluation Report No. 92-0361 - Page 3

Medical

Although NIOSH and NCID conducted a joint investigation, each had separate goals. The

goals of the NIOSH investigation were to determine the number of workers currently infected

with Coxiella burnetii, either recently or remotely, as well as the number of workers who had

experienced symptoms consistent with Q fever over the six months prior to our visit. We also

wanted to look for possible sources of infection, identify possible workplace risk factors, and

educate management and employees about Q fever. 

The goal of the NCID investigation was primarily to conduct a community investigation,

consisting of case-finding, testing possible animal reservoirs in the area, and locating a

comparison group for the miners' study. The NCID investigator also wanted to educate local

health care workers about Q fever. 

NIOSH

A self-administered questionnaire was distributed to current employees; it sought information

concerning demographic variables, work practices, exposure to animals in and out of the

workplace, as well as medical history, with emphasis on symptoms of Q fever. A 10-milliliter

(ml) blood sample was requested from each person after informed consent was obtained. The

blood samples were analyzed antigens at NCID laboratories using an indirect fluorescent

antibody (IFA) assay. Each blood sample was screened for IgG antibodies to phase II antigen. 

A positive sample was defined as having a titer greater than or equal to 1:64. The positive

samples were then further tested for IgM antibodies to phase II antigen and IgG antibodies to

phase I antigen in an effort to determine whether the infection was recent or remote.

NCID

The NCID investigation began with case-finding. The study population included mineworkers' family members who had heard about the investigation and came forward for testing;

persons identified through medical record research as possibly having Q fever; and a number

of "volunteers" from the community who sought out the NCID investigator upon hearing of

the study. A total of 27 participants completed questionnaires and had blood samples drawn

for Q fever testing. 

Animal testing was accomplished by collecting blood samples from deer, elk, and antelope

carcasses brought to the two meat processing facilities in the Greybull area. Twenty-five of

the samples collected from deer were suitable for testing. In addition, serum from local cattle

herds, collected for routine brucellosis testing, was requested to be forwarded to NCID for C.

burnetii antibody testing. 

Employees of the Wyoming Transportation Department (WTD), located in Basin, eight miles

south of Greybull, were selected as a comparison group for the bentonite mine workers. They

were selected because they were an easily identifiable group, since the highway department

was one of the few large employers in the area, and the outdoor work activities of this group

were
Health Hazard Evaluation Report No. 92-0361 - Page 4

similar to those of the mine employees. Of the 43 employees present on the day of the survey,

27 (63%) completed questionnaires, and of these, 25 (58%) submitted a blood sample for Q

fever testing.

Case definition

The case definition for Q fever was based entirely on the results of serological testing, using

the same case definition used by CDC in the laboratory-based surveillance of 1985.1 A case of

recent or current acute Q fever was defined as a single IgM titer of $1:64, or a single IgG titer

of $1:256. Persons with an IgG titer of at least 1:64 but below 1:256 were considered to have

had past infection with C. burnetii. This was also called "remote" infection. 

Analysis

Univariate analysis of the workers' questionnaires was performed using EpiInfo version 5.01a2

to define risk factors for infection with C. burnetii in our populations. A variety of exposures

were examined to determine risk factors for infection with C. burnetii, separately analyzed for

recent or remote infection. These exposures included where the workers spent the majority of

their work day, type of equipment used, contact with animals in the workplace or away from

work, and hobbies. 

RESULTS AND DISCUSSION

Participation

Forty-seven (81%) of the 58 current mine employees completed the questionnaire. Thirty-nine

(67%) submitted serum samples for testing.

Thirty-six of the 39 participants (78%) were white men; the mean age was 

46 years (range of 24-64 years). Most lived in Greybull; others lived within a 50 mile radius

of the town. The mean length of employment was 

15 years (range of 1-40 years). Most worked 9-12 hour days, 4-5 days per week. (See Table

1.)

Serological results

Three mine employees met the case definition for recent or current acute Q fever. Included in

this number were the two "index" cases. All three affected workers had experienced

symptoms consistent with Q fever in the 

six months prior to our investigation. Two of these workers had both elevated IgG and IgM

titers; the third had only an elevated IgG titer. Three other mine employees had IgG titers of

1:64, and another had an IgG titer of 1:128, indicating past infection. These persons had not

experienced symptoms of Q fever in the six months prior to the investigation.

Two ill community members had IgG titers of 1:256 or above. One of these was an adult

member of a mine employee's family, and the other had been identified through the medical

record search. One employee of the Wyoming Transportation Department had a titer of 1:64. 

He had not been ill in the previous six months.
Health Hazard Evaluation Report No. 92-0361 - Page 5

Cattle from two ranches, one in Big Horn County, where Greybull is located, and one in an

adjacent county, were tested for antibodies to C. burnetii. Three (21%) of the 14 cattle sera

from the ranch in Big Horn County were positive for IgG antibodies at $1:64. None of the 12

cattle sera from the ranch in the adjacent county was positive. None of the 25 deer sera was

positive for antibodies to Coxiella burnetii. 

Risk factors

Sheep ownership was the only statistically significant factor which correlated with recent

infection (odds ratio (OR)=70.0; confidence interval (CI)=2.0-13500). (See Table 2.)

Spending the majority of the workday outdoors was a suggestive but not statistically

significant risk factor for being infected with C. burnetii either recently or remotely (OR 8.8;

CI=0.9-425.1). (See Table 3.) Two of the three recently ill employees worked outdoors in the

mine area; the third worked in the packaging area. The four employees who had evidence of

past infection worked in the mine area. Among those who worked outdoors, heavy equipment

operation was not a statistically significant risk factor, although five of the six outdoor workers

infected with C. burnetii operated heavy, earth-moving equipment. This work was associated

with an odds ratio of 2.2, but a confidence interval which included one. (See Table 3.) Given

the plausibility of such dust-generating activity being a risk factor for infection, it is possible

that, with a larger sample size, this would be a true association. 

The hobby of hunting was associated with recent or remote infection (OR 7.8; lower 95%

confidence limit 1.04; p=0.045). Fishing was associated with an odds ratio of 6.9 (lower 95%

confidence limit 0.91; p=0.0625). (See 

Table 2.) It should be noted that these are not independent variables, as persons who hunt

were much more likely to fish, and vice versa, in this population. 

The following difference between the "outdoor" workers and the "indoor" workers was noted: 

95% of "outdoor" workers owned animals compared with 75% of the "indoor" workers. This

may be a confounder. A confounder is something which is related to exposure and affects the

outcome being studied, but which is not included in the original hypothesis. In this case,

owning animals provides an additional potential exposure to C. burnetii, which may place

animal owners at higher risk for infection; the fact that more "outdoor" workers than "indoor"

workers own animals may explain their higher rate of infection, rather than the fact that they

are "outdoor" workers. This difference in animal ownership failed to achieve statistical

significance. The numbers were too small to permit further analysis to answer this question. 

An equal proportion of "outdoor" and "indoor" workers hunted or fished. (See Table 4.)

Comparison

The bentonite mine workers were compared to the Transportation Department workers to test

the hypothesis that the mine area was a risk factor for infection with C. burnetii.If the infection

rates are compared, the prevalence odds ratio for recent infection was 2.6 (lower 95%

CI=0.27). Three of 39 mine workers and none of 25 Transportation Department workers

tested positive for recent Q fever. The risk of ever being infected with C. burnetii, however,

appeared to be higher among the miners, although this prevalence odds ratio of 4.6 had a 95%

confidence interval which included one. (See Table 5.) Seven of 

39 mine workers and one of 25 Transportation Department workers tested positive for

infection with C. burnetii.

The workers at the Wyoming Department of Transportation were demographically similar to

the bentonite miners studied. Twenty-one of the 25 workers were white men; the mean age
Health Hazard Evaluation Report No. 92-0361 - Page 6

was 45 years (range of 25-64). Most lived in Basin. Mean length of employment was 10 years

(range 1-31 years). (See Table 1.) 

A similar proportion of mine workers and Transportation Department workers worked

outdoors--49% versus 40%. This difference was not statistically significant. However, a

significantly higher proportion of the mine workers reported having contact with animals in

the workplace--59% versus 32%. Also, a significantly greater percentage of mine workers

operated earth-moving, heavy equipment--36% versus 12%. (See Table 6.) 

A smaller percentage of the mine workers owned animals, 87% compared to 92%, but a higher

percentage--72% versus 52%--reported having contact with animals away from the workplace. 

(See Table 7.) Neither of these differences was statistically significant. Equal proportions of

the mine workers and the Transportation Department workers hunted or fished. (See Table 7.)

Environmental

Due to technical problems with the PCR equipment, the soil samples were not analyzed.

Limitations

The study was limited by a number of factors. The number of workers studied was small,

which limited the statistical power and ability to perform more sophisticated analysis. The

small numbers may also have influenced the confidence intervals, because they affect the

standard error measurement (make it larger) upon which the confidence interval calculation is

based. The major risk factor for Q fever, contact with animals, is common among the

members of the study population, both at and away from the workplace, making the relative

contributions of occupational and non-occupational contact difficult to assess. Quantifying

exposure to animals is difficult to do, and so the reliability of our exposure information is

uncertain. In addition, difficulties in making the diagnosis of Q fever, even with serologic

testing, makes it possible that there were a number of false negatives. Several of the persons

may not yet have mounted an antibody response despite being infected.

CONCLUSIONS

1. Coxiella burnetii is present in Big Horn County, and persons there are at risk for

contracting Q fever.2.Outdoor work was a risk factor for acquiring Q fever among the

workers at the bentonite facility, as was hunting. Operation of heavy equipment may also

be a risk factor. 

3. Ownership of sheep correlated with recent acute Q fever in this investigation. Ownership

of animals, especially small pets, may also be a risk factor for infection with C. burnetii.

4. Working at the bentonite mine may have been a risk factor for infection with C. burnetii.

RECOMMENDATIONS

1. Physicians and other health-care providers should maintain a high index of suspicion for

Q fever in persons presenting with hepatitis, pneumonia, or unexplained febrile or

influenza-like illness, especially if there is a history of contact with or work near animals

or areas in which animals live.

2. Avoid contact with soil obviously contaminated with animal urine, feces, milk, or birth

products. This is directed especially at persons with valvular heart disease or pregnant

women. 
Health Hazard Evaluation Report No. 92-0361 - Page 7

3. Because Q fever is a notifiable disease in Wyoming, physicians, laboratory workers, and

other health-care providers should report cases to the state epidemiologist. 

4. Further study may help answer some of the questions raised by this investigation. For

example, a limited active surveillance study in an endemic area such as this would yield

useful information about incidence and prevalence as well as more specific data on risk

factors.

AUTHORSHIP AND ACKNOWLEDGMENTS

Evaluation Conducted and Thomas J. Van Gilder, M.D.

 Report Prepared By: Medical Officer

Laura Robinson, D.V.M., M.S.

EIS Officer

Originating Office: NIOSH

Hazard Evaluations and Technical

 Assistance Branch

Division of Surveillance, Hazard

 Evaluations, and Field Studies

Cincinnati, Ohio

Laboratory Support CDC/NCID/DVRD/VRZB
Health Hazard Evaluation Report No. 92-0361 - Page 8

REPORT DISTRIBUTION AND AVAILABILITY OF REPORT

Copies of this report may be freely reproduced and are not copyrighted. Single copies of this

report will be available for a period of 90 days from the date of this report from the NIOSH

Publications Office, 4676 Columbia Parkway, Cincinnati, Ohio 45226. To expedite your

request, include a self-addressed mailing label along with your written request. After this

time, copies may be purchased from the National Technical Information Service (NTIS), 5285

Port Royal, Springfield, Virginia 22161. Information regarding the NTIS stock number may

be obtained from the NIOSH Publications Office at the Cincinnati address. Copies of this

report have been sent to:

1. M-I Drilling Fluids

2. Wyoming Department of Health

3. Employee representatives

4. OSHA Regional Office

For the purpose of informing affected employees, copies of this report shall be posted by the

employer in a prominent place accessible to the employees for a period of 30 calendar days.
TABLE 1

HETA 92-361

M-I DRILLING FLUIDS

GREYBULL, WYOMING

October 13, 1992

DEMOGRAPHICS

39 Mine Workers

Mean age (range) 46 years (24-64)

Sex 36 men 3 women

Race 38 white 1 Hispanic

Mean employment length (range) 15 years (1-40)

25 Wyoming Transportation Department Workers

Mean age (range) 45 years (25-64)

Sex 21 men 4 women

Race 25 white 0 other

Mean employment length (range) 11 years (1-31)
TABLE 2

HETA 92-361

M-I DRILLING FLUIDS

GREYBULL, WYOMING

October 13, 1992

NON-WORKPLACE RISK FACTORS

Recent Infection

Exposure Odds Ratio 95% CI*

Sheep ownership 70.0 2.0-13,500

Recent or Remote Infection

Exposure Odds Ratio Lower 95% CL**

Hunting 7.8 1.04

Fishing 6.9 0.91

*Confidence interval

**Lower 95% confidence limit (CL) used because an empty cell was present. These values

were obtained using log exact methods (LogXact).3
TABLE 3

HETA 92-361

M-I DRILLING FLUIDS

GREYBULL, WYOMING

October 13, 1992

WORKPLACE RISK FACTORS

Recent or Remote Infection

Exposure Odds Ratio 95% CI*

Outdoor work

--heavy equipment use

8.8

2.2

0.9-425.1

0.2-131.0

*Confidence interval
TABLE 4

HETA 92-361

M-I DRILLING FLUIDS

GREYBULL, WYOMING

October 13, 1992

POSSIBLE CONFOUNDERS: OUTDOOR VS. INDOOR WORKERS

39 Mine Workers

Exposure Outdoor

19 participants

Indoor

20 participants

Own animals 18 (95%) 15 (75%)

--livestock 9 (47%) 13 (65%)

--sheep 1 (5%) 0 

--pets 18 (95%) 14 (70%)

Hunt 12 (63%) 12 (60%)

Fish 12 (63%) 13 (65%)
TABLE 5

HETA 92-361

M-I DRILLING FLUIDS

GREYBULL, WYOMING

October 13, 1992

OCCURRENCE OF INFECTION: MINE WORKERS VS. WTD WORKERS

Mine Workers vs. WTD Workers

Infection Prevalence

Odds Ratio

95% CI*

Recent 2.6 0.27**

Remote 4.6 0.5-212.8

*Confidence interval

**Lower 95% confidence limit used because an empty cell was present. These values were

obtained using log exact methods (LogXact).3
TABLE 6

HETA 92-361

M-I DRILLING FLUIDS

GREYBULL, WYOMING

October 13, 1992

EXPOSURE COMPARISON: WORKPLACE EXPOSURES

Mine Workers vs. WTD* Workers

Exposure Mine Workers

39 participants

WTD Workers

25 participants

Outdoor work 19 (49%) 10 (40%)

Work contact with animals 23 (59%) 8 (32%)

Heavy equipment 14 (36%) 3 (12%)

*Wyoming Transportation Department
TABLE 7

HETA 92-361

M-I DRILLING FLUIDS

GREYBULL, WYOMING

October 13, 1992

EXPOSURE COMPARISON: NON-WORKPLACE EXPOSURES

Mine Workers vs. WTD* Workers

Exposure Mine Workers

39 participants

WTD Workers

25 participants

Own animals 34 (87%) 23 (92%)

Non-work contact with animals 28 (72%) 13 (52%)

Hunt 24 (61%) 15 (60%)

Fish 25 (64%) 16 (64%)

*Wyoming Transportation Department
APPENDIX A

Q Fever

Q fever is a disease caused by the rickettsia Coxiella burnetii. C. burnetii is extremely

infectious; a single inhaled organism may be all that is necessary to initiate disease.4 The

organism is hardier than most rickettsiae, resistant to desiccation as well as most physical and

chemical agents. It has been reported to survive for months in the soil.4 

Natural reservoirs for C. burnetii include ticks5--Dermacentor, Amblyomma, Ixodes, and

Haemaphysalis--and a variety of animals, including cattle, sheep, goats, and cats. Animals

typically have a subclinical course, even while shedding the organism in high numbers in

urine, feces, milk, and, especially, amniotic fluid.4

Q fever is usually contracted through direct or indirect contact with infected animals or animal

products. Most often, this occurs through inhalation of dust contaminated by the urine, feces,

milk, or amniotic fluid of an infected animal.4 There are reports of disease occurring after

handling infected animal skins or drinking contaminated unpasteurized milk.6 There is no

documented transmission of C. burnetii from ticks to humans, although it is possible that ticks

are responsible for spreading the organism among animals.4 There have been no reports of

human to human transmission of Q fever, with the exception of one report of spread by blood

transfusion.5

The incubation period for Q fever averages 19-20 days, with a range of 14-39 days.6 The

clinical manifestations vary from mild (it can go almost unnoticed) to debilitating. Typically,

the symptoms are similar to influenza. The first symptom is often chills, perhaps rigors,

accompanying a fever of up to 105°F.4 Headache, muscle aches, fatigue, anorexia, and

malaise predominate. Chest pain, cough, and abdominal pain may also occur. These

symptoms may last days to weeks, but rarely last longer than two weeks. Elderly persons are

more likely to have a more protracted course,4 with symptoms lasting up to four weeks. Even

after resolution of the acute symptoms, many persons continue to feel generally weak. 

However, these symptoms, too, typically resolve within 4-6 weeks. Another manifestation of

Q fever is pneumonia. Also, up to 1/3 of persons infected with C. burnetii develop hepatitis.5 

Acute Q fever, including pneumonia and hepatitis, usually resolves over a period of weeks

without intervention.6 In a small proportion of persons, however, Q fever becomes a chronic

disease typically manifested by endocarditis. This usually evolves slowly, occurring up to 20

years after acute infection. Persons at higher risk include those with heart valve

abnormalities.4 Q fever endocarditis is a much more serious disease than acute Q fever. It is

difficult to treat, responding poorly to antibiotics, often requires surgical valve replacement,

and is frequently fatal.4

Some unusual manifestations of infection with C. burnetii include neurologic manifestations,

such as encephalitis in children, hemolytic anemia, and infertility and miscarriage.6
Epidemiology

The incidence and prevalence of infection with C. burnetii among humans and other animals is

not entirely clear. It has been described throughout the world.4 Several attempts have been

made at estimating the incidence of Q fever or prevalence of infection with C. burnetii among

humans, cattle, and sheep. Among humans, reports have ranged from less than 1% to 30%,

with rural areas having a higher seroprevalence. Animal seroprevalence varies by region and

species.7

In the United States, where reporting of Q fever cases to CDC is voluntary, several efforts

have been made to determine the occurrence and distribution of cases. Conclusions from these

investigations included that it is difficult to determine the incidence and distribution of Q fever

in the U.S.; that it may occur more often than it is reported or diagnosed; but, that it occurs

infrequently.8 Wyoming, where Q fever is a reportable disease, has only two recorded cases in

the past 11 years. Prior to that, in the years 1948-1977, 10 cases had been reported.8

Diagnosis

The diagnosis of Q fever rests primarily on serologic testing. Although complement fixation

(CF) and enzyme-linked immunosorbent assay (ELISA) methods are used, the indirect

fluorescent antibody assay (IFA) is the most widely used test and allows detection of various

immunoglobulin isotypes, as well as the antigenic phase variation.6 This can be helpful in

establishing the acuteness of the infection. Specific IgM antibodies can be detected as early as

7 days after exposure.5 Most people appear to have an IgM antibody response within the first

two weeks, but others may have a delayed response. IgG antibodies may persist for a longer

period of time. 

Therapy

In acute Q fever, tetracycline or doxycycline, if administered within the first three days of

illness, may reduce the duration of fever.6 

In Q fever endocarditis, optimal antimicrobial therapy has not been fully defined. Various

combinations have been suggested, with treatment duration ranging from 12 months to an

indefinite period.6 
REFERENCES

1. Sawyer LA, Fishbein DB, McDade JE. Q Fever in Patients with Hepatitis and

Pneumonia: Results of Laboratory-Based Surveillance in the United States. Journal of

Infectious Diseases 1988;158(2):497-8.

2. Dean AG, Dean JA, Burton AH, Dicker RC. Epi Info, Version 5.01a: a word 

processing, database, and statistics program for epidemiology on 

microcomputers. Centers for Disease Control and Prevention, Atlanta, 

Georgia, USA, 1990.

3. LogXact (1992). Cytel Software Corporation, Cambridge, MA.

4. CDC. Q Fever among Slaughterhouse Workers--California. MMWR 1986;35:223-6.

5. Woodward TE. Rickettsial Diseases. In Wilson JD, Braunwald E, Isselbacher KJ, et. al.,

eds. Harrison's Principles of Internal Medicine. 12th ed. New York: McGraw-Hill,

1991:761-2.

6. Sawyer LA, Fishbein DB, McDade JE. Q Fever: Current Concepts. Reviews of Infectious

Diseases 1987;9(5):935-46.

7. Regnery R, McDade JE. Coxiella burnetii (Q Fever), a Potential Microbial Contaminant

of the Environment. In: Morey PR, Feeley JC, Otten JA, eds. Biological Contaminants In

Indoor Environments, Philadelphia, 1990;ASTM STP 107:115-34. 

8. D'Angelo LJ, Baker EF, Schlosser W. From the Center for Disease Control: Q Fever in

the United States, 1948-1977. Journal of Infectious Diseases 1979;139(5):613-615.