Post on 13-Jan-2016
Q Fever:A Public Health Paradox
Emerging Zoonotic Diseases Summit, August 23, 2005Jennifer H. McQuiston,
Viral and Rickettsial Zoonoses Branch Division of Viral and Rickettsial Diseases
Centers for Disease Control and Prevention, Atlanta, GA
Background
• “Query fever”• Worldwide zoonosis• Caused by Coxiella burnetii
- Gram-negative coccobacillus - replicates in host macrophages and monocytes
• Shed in birthing fluids, excreta, milk• Humans infected via inhalation, ingestion
Electron micrograph showing an infected monkey cell with one large vacuole harboring about 20 Coxiella burnetii bacteria. [Credit: R Heinzen, NIAID]
Environmental Persistence
• Shed in the environment in a small cell form that is very hardy (“spore-like”)
• Resistant to pH changes, desiccation, UV light
• Resistant to some common disinfectants
• Remains viable in soil, dust for months to years- isolated from barns, soil – culture, PCR
• Raises questions regarding:- environmental contamination- appropriate cleaning/disinfection
Transmission
• Ruminants most common source of human infection - Cattle, sheep, goats
• Domestic animals - Cats
• Wild Animals (rodents)• Birds (pigeons)• Ticks• Wind-borne environmental spread
- Can be spread several miles down-wind from farms
• Contact with contaminated products - Straw - Fertilizer - Farm equipment
• Human-to-human rare (OB/GYN, sexual)
Acute Q fever
• 1-3 week incubation• Asymptomatic infections occur• Nonspecific signs and symptoms
• fever• severe headache• myalgias• cough• fatigue• night sweats• rigors• nausea/vomiting
• Nonspecific flu-like illness• Pulmonary Syndrome (~30%)• Hepatitis (30-60%)• Myocarditis, meningoencephalitis (rare)• Antibiotics may shorten course• Low mortality (< 1 %)• Treatment: Doxycycline• Chronic fatigue-like illness
- following acute infection in Australian slaughterhouse workers (10%)
Acute Q fever
Chronic Q fever
• Endocarditis- latent infection- < 1-2% of acute cases- immunocompromised, heart valve disorders at greater risk- life-threatening, heart valve replacement may be required- treament: 18 months doxycycline, hydroxychloroquine
• Granulomatous hepatitis, osteomyelitis
Diagnosis
• Serology• IFA, paired sera• Phase 2 antibody: acute infection• Phase I > Phase 2 antibody: chronic infection• Antibody can persist for a long time, or take a while to develop• Commercial labs may incorrectly report low titers as positive
• Culture• Requires BSL-3, Select Agent
• PCR, Immunohistochemistry
Q fever and Bioterrorism
• Category B bioterrorism agent- high morbidity- inhalation route of transmission- extreme persistence in environment
• Previous development as an agent of biowarfare
• Accessible – obtain from environment
History of Q fever Bioweapons Research
• First agent studied by Fort Detrick’s bioweapons program in 1954
• Successfully developed an aerosol dispersion model - demonstrated infectivity for animal subjects and human volunteers in the “8-ball”- successfully field-tested via aerosol dispersion to human volunteers located > 0.5 miles downwind- developed dosage curves (1-10 units infective dose)
The “8-Ball”Ft. Detrick, MD ca. 1968
Q fever Outbreaks in the United States
• Occupational exposures most frequently cited• research facilities using parturient ruminants • slaughterhouses• farms• factories
• Sheep implicated more frequently than other animals in outbreaks
Q fever Seroprevalence in the United States
Human Seroprevalence Studies :- persons with livestock contact 7.8%- general population 0.8%- Risk Ratio 10.3 [95% CI 9.0-11.8])
• Ruminant Seroprevalence Studies:- bovine bulk tank: 26.3%- cattle: 3.4%- sheep: 16.5%- goats: 41.6%
• Vet school dairy herds, antibodies in milk - 9/22 (38%) had titers ≥ 1:256
Q fever Surveillance in the United States: Human Cases Reported by State Health Departments, 1978-1999
2
17
18167
1 (CT)
1 (DC)
3
12
2
1
11
13
187
5
5
4
10
3 3
23
19
15
15
7
n=436 Mean: 20 per year
Current Surveillance for Q fever in the United States
• Q fever in animals is not reportable
• Human disease was made reportable in 1999 - states report cases to CDC via NETSS
- data available for 2000-2004
Cases of Q fever in Humans Reported by State Health Departments, 1978-2004
* Years in which Q fever was a Nationally Reportable Disease
0
10
20
30
40
50
60
70
801
97
81
97
91
98
01
98
11
98
21
98
31
98
41
98
51
98
61
98
71
98
81
98
91
99
01
99
11
99
21
99
31
99
41
99
51
99
61
99
71
99
81
99
92
00
0*
20
01
*2
00
2*
20
03
*2
00
4*
Year
Nu
mb
er
of
Ca
se
s
National Reporting, 2000-2004Demographics
• n = 255, Mean 64 cases per year• Gender: 195 (77%) Male• Age: mean, median 51 years• Race
• White: 92%• Black: 6%• Asian: 2%
• Hispanic: 13.4%• No significant difference in gender distribution among age groups
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0-9
10
-19
20
-29
30
-39
40
-49
50
-59
60
-69
70
+
Age Group in Years
Inc
ide
nc
e p
er
mill
ion
pe
rso
ns
Age Distribution of Q fever Casesin the United States, NETSS 2000-2004
p< 0.0001
Month of Illness Onset, Q fever Casesin the United States, NETSS 2000-2004
0
5
10
15
20
25
30
35
40Ja
nu
ary
Fe
bru
ary
Ma
rch
Ap
ril
Ma
y
Jun
e
July
Au
gu
st
Se
pte
mb
er
Oct
ob
er
No
vem
be
r
De
cem
be
r
Month of Illness Onset
Nu
mb
er
of
Ca
se
s
Not Reportable 2000-2004
≥ 0.28 per million
< 0.28 per million
0.45
0.31
2.40
0.63
0.93
0.51
0.35
0.64
0.94
0.32
0.52
0.28 1.52
Average Annual Incidence of Q fever in Humans Reported by State Health Departments, 2000-2004
0.44
* Incidence calculated for years when Q fever was reportable.
0.28
0.42(MA)
1.33(DC)
Summary: Human Surveillance
• Incidence of Q fever in humans is highest in the midwestern and western states, and lower in the eastern U.S.
- differences in livestock densities do not offer complete understanding - complex interplay of agricultural practices, human population
density, and climactic factors
• Demographics similar to previously published studies- middle-aged male patients- exception: no evidence of gender difference between adolescent
cases vs. adult cases
Why is Surveillance so difficult?
• Nonspecific clinical signs-resembles a variety of other common illnesses- self-limiting in most cases- poor physician recognition
• Requires laboratory confirmation for reporting• Serology requires paired serum specimens
- early specimens frequently negative- patients rarely return to provide convalescent samples
• Physicians must request appropriate tests
Why is Surveillance so important?
• Category B bioterrorism agent- vital to establish endemic baseline levels- need to understand background seroprevalence before a BT event takes place
• Current numbers of cases are under-reported - true level of disease unknown- level of serious disease (endocarditis) unknown- economic burden of Q fever in humans and animals is poorly assessed
- in Australia, considered the most economically important zoonosis
Credit: Ralph A. Clevenger, 1999
Q fever: Investigation Challenges
• All human cases should be investigated and reported- Document geographic trends- Recognize persons at high risk for endocarditis- Assess source to determine outbreak potential
• Investigating animal infection may be problematic- Endemic in ruminants- Serologic assessment difficult
- Phase 1 antibody may be more prominent- Historically, only Phase 2 antibody was examined
- Cannot easily prevent or control infection in herds
Q fever: A Public Health Paradox
• Difficulties in clinical and laboratory diagnosis make adequate surveillance problematic.
• However, because of bioterrorism potential and possible serious outcomes in high-risk persons, surveillance and reporting are critical.
• Investigating sporadic human cases may not help reduce risk
- there is often little that can be done to minimize transmission in farm settings.
Prevention• Laboratory environments
- vaccination when possible (IND in U.S.) - appropriate respiratory protection
• Research environments with parturient ruminants- Q fever-free animals- employee biomonitoring program- strict biocontainment
• Farm/slaughterhouse situations: - vaccine (Australia, not available in U.S.)- attention to hygiene- need for employee serologic monitoring?
• General Public- pasteurize milk products- limit contact with parturient animals, especially in public settings (petting zoos, etc)
Discussion
• Q fever in humans is likely substantially underreported- nonspecific clinical signs
- poor physician recognition - difficult laboratory diagnosis
• Surveillance for Q fever in the U.S. is improving- made nationally reportable in 1999- reporting increased by ~ 300% from 2000-2004- reportable in 46 states in 2004
• Future studies will improve our understanding of geographic patterns of infection and risk
AcknowledgmentsBob Holman, Division of Viral and Rickettsial Diseases, CDCViral and Rickettsial Zoonoses Branch, CDC
Especially: Herb ThompsonVrinda NargundMargaret BowmanTracey McCrackenCandace McCallJamie ChildsNETSS StaffState Health DepartmentsU.S. Veterinary Schools
Not Reportable 2000-2004
≥ 0.28 per million
< 0.28 per million
0.45
0.31
2.40
0.63
0.93
0.51
0.35
0.64
0.94
0.32
0.52
0.28 1.52
Average Annual Incidence of Q fever in Humans Reported by State Health Departments, 2000-2004
0.44
* Incidence calculated for years when Q fever was reportable.
0.28
0.42(MA)
1.33(DC)
Dairy Cows per Square Mile In the United States, 1998
5.8
13.3
10.6
5.1
5.0
8.9
37.67.8
9.3
5.0
5.4
21.4
11.8
20.1
0.0-2.0 per square mile
> 2.0 per square mile
6.5
24.1
60.187.6
30.1
53.6
51.0.
78.6
33.2
57.4
30.9
Beef Cattle per Square Mile In the United States, 1998
46.3
> 0.0- 15.0 per square mile
> 15 per square mile
59.5
76.7
38.2
5.5
4.77.3
5.15.1
3.4
5.8
3.3
Sheep per Square Mile In the United States, 1998
5.4
0.0-1.5 per square mile
> 1.5 per square mile
No reports