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International Society for Infectious Diseases
Date: Thu 11 Jun 2009
Source: MMWR 12 Jun 2009; 58: 618-621 [edited]
Historically, brucellosis from _Brucella suis_ infection occurred
among workers in swine slaughterhouses. In 1972, the USA Department
of Agriculture National Brucellosis Eradication Program was expanded
to cover swine herds. Subsequent elimination of brucellosis in
commercial swine resulted in a decrease in _B. suis_-associated
illness in humans. Currently, swine-associated brucellosis in humans
in the USA is predominantly associated with exposure to infected
feral swine (i.e., wild boar or wild hogs), that is, swine that have
lived any part of their lives as free-roaming animals.
In May and July 2008, the Centers for Disease Control and Prevention
(CDC) was contacted by the state health departments in South Carolina
and Pennsylvania regarding 2 cases of brucellosis possibly linked to
feral swine hunts. Both state health departments contacted the state
health department in Florida, where the hunts took place. The
subsequent investigation, conducted jointly by the 3 state health
departments and the CDC, determined that the 2 patients had confirmed
brucellosis from _B. suis_ infection and the brother of 1 patient had
probable brucellosis. All 3 exposures were associated with feral
swine hunting, and at least 2 patients did not have symptoms until
4-6 months after exposure (Table [for table, see original URL -
Mod.LL]). The findings from this investigation suggest that
clinicians treating patients with unexplained febrile illness should
consider brucellosis in the differential diagnosis and obtain a
thorough history of travel (e.g., to enzootic areas), food
consumption, occupation, and recreational activities, including feral
swine hunting. Cross-agency collaboration by state health departments
and agriculture agencies is needed on brucellosis investigations to
reduce the risk for illness through contact with infected animals.
Patient A. On 7 May 2008, a man aged 67 years from South Carolina
(patient A) was referred by his private physician to a local
emergency department after 1 week of fever (cyclic daily range: 99.2
degrees - 102.5 degrees F [37.3 degrees C - 39.2 degrees C]),
malaise, anorexia, painful swollen left knee, and headaches. Patient
A had a left total knee arthroplasty in 2004 and uneventful treatment
in 2005 for septic arthritis in the same knee. Before onset of
symptoms for his acute illness, patient A reported that he felt well
except for an unintended 13 pound weight loss over a 16 week period
and night sweats that began the day before he sought treatment. In
the emergency department, blood and synovial fluid were obtained for
culture, and the patient was empirically treated with intravenous
nafcillin for septic arthritis.
Then, 2 days later, on 9 May 2009, the man was referred to a hospital
with chills, persistent fever, continuing left knee arthralgia, and
edema. He was admitted with a diagnosis of left knee infection and
sepsis and treated initially with vancomyin. Knee aspirate cell count
results were 16 700 white blood cells/cubic mm (normal: greater than
150) and 1322 red blood cells/cubic mm (normal: greater than 1).
Specimens of blood and a knee aspirate were collected for culture.
Initial microbiologic examination indicated _Corynebacterium
urealyticum_. Upon infectious disease consultation, the patient was
started on doxycycline and naprosyn; on 11 May 2009, he developed
epididymo-orchitis and was changed to levofloxacin and daptomycin on
12 May 2009 for a 6 week course. _Brucella spp._ subsequently were
identified from isolates from the blood and synovial specimens
collected from patient A on 7 May 2009. Isolates were sent to the
South Carolina state public health laboratory and CDC for
confirmatory testing. On 29 May 2009, _B. suis_ biovar 1 was identified.
The epidemiologic investigation revealed that patient A had hunted
feral swine in southwestern and south central Florida with 2
companions during 23 - 29 Dec 2007. All participated in field
dressing and butchering 8 or 9 feral swine at 2 locations. While
field dressing one of the swine, patient A cut his hand with a knife.
No personal protective equipment was worn during the field dressing
and butchering. The meat was brought back to South Carolina, stored
in a freezer, and boiled before being consumed by patient A over
several months. No one else prepared or ate the meat, and no meat was
collected for testing. No other risk factors for brucellosis were identified.
Because patient A's hunting companions were well, serologic testing
for brucellosis was not performed. Patient A recovered with no
permanent knee joint damage after antimicrobial therapy with
levofloxacin and daptomycin for 6 weeks.
Patient B. On 14 Jul 2008, a previously healthy man aged 37 years
from Pennsylvania (patient B) went to a local emergency department
after 1 week of morning fevers, chills, myalgia, shortness of breath,
and night sweats. He also reported an unintended 30 pound weight loss
over a 1 month period, beginning 3 weeks before illness onset. A
blood chemistry profile was within normal limits with the exception
of glucose of 121 mg/dL (normal: 74 - 100). A blood specimen for
culture was obtained.
Clinical impression was acute viral syndrome; patient B was
discharged with instructions to use an albuterol metered-dose inhaler
3 times daily for 1 - 2 days for his shortness of breath and to
follow up with his private physician in 2-3 days. On 23 Jul 2009, the
Pennsylvania state public health laboratory received patient B's
blood specimen from the local hospital and isolated and identified
_B. suis_ using Laboratory Response Network standardized biochemical
tests and polymerase chain reaction.
Epidemiologic investigation revealed that, on 29 Dec 2007, patient B
had hunted feral swine in Florida with his brother (patient C), a
Florida resident. Both men participated in field dressing and
butchering 4 feral swine. No personal protective equipment was worn
during these procedures, and no other risk factors for brucellosis
were identified. Patient B brought the meat back to Pennsylvania and
stored it in a freezer. The meat was prepared and consumed by patient
B and his family members over a 7 month period. According to patient
B, the meat was cooked adequately (i.e., to an internal temperature
of 160 degrees F [71.1 degrees C]).
The CDC received 3 _B. suis_ isolates for confirmation and further
molecular characterization. One isolate was from the blood of patient
B, and the other 2 were recovered from frozen sausage and tenderloin
of a feral swine from the 29 Dec 2009 hunt. All 3 _B. suis_ isolates
were analyzed at the CDC by molecular genotyping assay, using
multiple-locus variable-number tandem repeat analysis. The assay
indicated that the 2 meat isolates had identical signatures at all of
the 15 genomic markers, and the patient B isolate matched the meat
isolates at all but 1 of 15 markers, suggesting that the 3 isolates
Patient B reported that his wife and children were not ill; however,
his brother (patient C) had experienced similar symptoms in April
2008. Although asymptomatic, initial serologic testing for
brucellosis was performed on all household family members, and no
antibody elevation was noted. Patient B recovered after 6 weeks of
treatment with rifampin and doxycycline.
Patient C. In August 2008, the Pennsylvania state health department
reported the association between patient B's infection and feral
swine hunting to the Florida state health department, which, on 21
Aug 2008, contacted patient C (patient B's brother who had
accompanied him on feral swine hunts). At the time, neither patient C
nor his family members reported experiencing symptoms of brucellosis.
However, patient C recalled feeling ill in April 2008 with night
sweats and shortness of breath. He did not seek treatment because he
attributed his symptoms to a recent scorpion sting.
Other than feral swine hunting, no other brucellosis risk factors
were identified for patient C. He reported that all the meat he
received from the December 2007 feral swine hunts was either smoked,
roasted, or barbequed and was consumed at one family cookout. On 12
Sep 2008, a serum specimen from patient C was tested at CDC for
anti-Brucella antibodies using the Brucella microagglutination test.
The resulting immunoglobulin G titer of 1:640 met the case definition
for probable brucellosis.
Because patient C's family was well, serologic testing for
brucellosis was not performed. Treatment was recommended for patient
C, but he was lost to follow-up.
Brucellosis is a bacterial zoonotic infection usually caused by
_Brucella abortus_, _B. melitensis_, _B. suis_, or rarely _B. canis_.
Humans are infected through occupational or recreational exposure to
infected animals, inhalation of infectious aerosols, laboratory
exposure (1), consumption of contaminated unpasteurized dairy
products, or consumption of inadequately cooked contaminated meat.
The average incubation period for brucellosis is 2-10 weeks but, as
seen in this report, can range to 6 months. Symptoms can be
nonspecific and influenza-like: intermittent fever, chills, malaise,
diaphoresis, arthralgia, myalgia, headache, anorexia, and fatigue
(2,3). Because of its nonspecific clinical syndrome, _B. suis_
infection likely is underreported. Clinicians should inquire about
travel, food consumption, occupation, and recreational activities
(including feral swine hunting) of patients with nonspecific
influenza-like symptoms with intermittent fever.
Patient A likely was infected through the hand wound he acquired
while field dressing feral swine. The investigations suggest that
patient B and patient C also were infected during the field dressing
or butchering process because family members consumed the meat and
were not affected clinically. Clinicians should order brucellosis
testing for persons who are symptomatic and have a history of feral
swine hunting. Duration and type of therapy is dependent upon
multiple factors such as health status or age of patient and the
manifestation of disease. Untreated brucellosis can last from several
weeks to several years. Chronic untreated brucellosis can lead to
abscesses in the liver, spleen, heart valves, brain, or bone;
osteoarticular complications; and, in rare cases, death (2,3).
Human brucellosis is a nationally notifiable disease in all 50
states, New York City, the District of Columbia, and all USA
territories except Puerto Rico. In 2007, 131 brucellosis cases were
reported in the United States (Figure [for figure, see original URL -
Mod.LL]). States with the highest numbers of reported cases were
California (33), Texas (25), and Florida (10) (4).
Feral swine have been reported in 35 states (J. Corn, PhD, personal
communication, Southeastern Cooperative Wildlife Disease Study,
2009). The national feral swine population is estimated at
approximately 4-5 million, with the largest populations in Texas (1.5
million), California, Florida, and Hawaii. Serologic surveys have
detected endemic feral swine infection with _B. suis_ in 10 states
(Arkansas, California, Florida, Georgia, Hawaii, Louisiana,
Mississippi, Missouri, South Carolina, and Texas) (5-9). Feral swine
hunting is allowed in most states with feral swine presence, and most
states require some form of license to hunt feral swine. Out-of-state
hunters, as in this report, often bring swine meat back to their home states.
Efforts to prevent _B. suis_ infection should focus on education of
hunters and partnerships between state and local public health,
wildlife, and agricultural agencies, and sportsmen's associations.
Educational materials for feral swine hunters should include
recommendations for safe field dressing, butchering, and cooking (9).
All human brucellosis cases should be investigated jointly by state
health departments and agriculture agencies to determine the sources
of infection and prevent further illness in humans.
1. CDC: Laboratory-acquired brucellosis--Indiana and Minnesota,
2006. MMWR 2008;57: 39-42.
2. Glynn MK, Lynn TV. Brucellosis: J Am Vet Med Assoc 2008;233: 900-908.
3. Mikolich DJ, Boyce JM: Brucella species [Chapter 223]. In:
Mandell, Douglas, and Bennett's principles and practice of infectious
diseases. 6th ed. Philadelphia, PA: Elsevier Inc.; 2005:2669-2674.
4. CDC: Summary of notifiable diseases--United States, 2007. MMWR
2009;56(53). In press.
5. Gresham CS, Gresham CA, Duffy MJ, et al: Increased prevalence of
Brucella suis and pseudorabies virus antibodies in adults of an
isolated feral swine population in coastal South Carolina. J Wildl
Dis 2002;38: 653-656.
6. Stoffregen WC, Olsen SC, Wheeler CJ, et al: Diagnostic
characterization of a feral swine herd enzootically infected with
Brucella. J Vet Diagn Invest 2007;19: 227-237.
7. van der Leek ML, Becker HN, Humphrey P, et al: Prevalence of
Brucella sp. antibodies in feral swine in Florida. J Wildl Dis
8. Zygmont SM, Nettles VF, Shotts EB, et al: Brucellosis in wild
swine: a serologic and bacteriologic survey in the southeastern
United States and Hawaii. J Am Vet Med Assoc 1982;181: 1285-1287.
9. Animal and Plant Health Inspection Service, US Department of
Agriculture. Feral/wild pigs: potential problems for farmers and
hunters. Agriculture information bulletin no. 799. Washington, DC: US
Department of Agriculture; 2005. Available at
[Byline: Giurgiutiu D, Banis C, Hunt E, et al.]
[As an occupation-related disease, infection can result from the
organism from diseased animals through skin lesions or mucous
membranes or from the inhalation of contamination dust or aerosols.
Inhalation is involved with many cases associated with abbatoir
workers (1). Contamination of skin lesions is also common in meat
packing wokers or veterinarians. As in this cluster, hunters may be
infected through skin lesions or by accidental ingestion of bacilli
during or after cleaning moose, elk or (as here) feral pigs.
Historically (2), Capasso found bone lesions typical of brucellosis
in adult skeletal remians of people killed during the 1st volcanic
surge of Mount Vesuvius. He also demonstrated by scanning electron
microscopy analysis of buried carbonized cheese, the presence of
bacterial forms consistent with _Brucella_ spp. Sir David Bruce 1st
isolated the organism associated with Maltese (or Malta) fever from a
British soldier who died in 1887 and the organism was eventually
named in his honor. The organism, also in Malta, was isolated from
goat's milk in 1905.
Microbiologically, classical biovar typing methodology is
time-consuming, poorly standardized, and required high-level
biosafety containment. Typing the 4 biovars of _B. suis_ involves
hydrogen sulfide production, growth in dyes, bacteriophage
susceptibility and agglutination with biovar-specific antisera. To
simplify this process, real-time polymerase chain reaction technology
looking at single nucleotide polymorphism can be used (3).
1. Robson JM, Harrison MW, Wood RN, et al: Brucellosis: re-emergence
and changing epidemiology in Queeenland. Med J Aust 1993;159: 153-159.
2. Godfroid J, Cloeckaert A, Liautard J-P, et al: From the discovery
of the Malta fever's agent to the discovery of a marine mammal
reservoid, brucellosis has continuously been a re-emerging zoonosis.
Vet Res 2005;36: 313-326.
3. Fretin D, Whatmore AM, Al Dahouk S, et al: Brucella suis
identification and biovar typing by real-time PCR. Vet Microbiol.
2008;131: 376-385. - Mod.LL]
Brucellosis, lab workers, 2006 - USA: (IN, MN) 20080117.0214
Brucellosis, Q fever, lab workers - USA (TX) 20070706.2146
Brucellosis, ovine, contaminated agar - USA: alert 20040820.2315
Brucellosis - USA (Arkansas) ex Mexico: alert 20010805.1539]
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