Brucellosis, also known as "undulant fever",
"Malta fever" or "Mediterranean
fever," is primarily a disease of those whose occupations
bring them into direct contact with domestic animals. (Brucella
suis infection has also been documented in feral swine
hunters.)
The severity of human disease varies, depending largely upon
the infecting strain:
- B. melitensis infection causes the most severe disease,
followed by B. suis > B. abortus > B.
canis.
- B. melitensis and B. suis are more resistant
to bacteriolytic factors in serum.
- Of regional concern, there were 6,500 cases of human brucellosis
in Mexico in 1998, many of which were attributable to B. melitensis.
- B. ovis is not known to be zoonotic.
Modes of transmission:
- Transmission via unpasteurized milk and contaminated cheese
was, historically, a serious problem. However, where pasteurization
is practiced, such transmission is rare today - the exception
being an on-going risk of infection from consumption of soft
cheese products.
- Infection today occurs most commonly by contact with placental
tissues or vaginal secretions from infected animals (and to a
lesser degree because of contact with blood or urine).
- Contact with secretions from both domestic and exotic animals
can pose risks, e.g. 5 zookeepers in Japan developed brucellosis
in 2001 after attending the delivery of a baby moose.
- There is limited evidence of person-to-person transmission
of Brucella spp.-- Venereal transmission has been reported
between a laboratory worker and his spouse, and B. melitensis
abscesses in a woman's breast may serve as a source of infection
for her infant.
- Brucellosis is also a disease of concern as a bioterrorist
weapon.
Clinical symptoms of brucellosis in humans:
The incubation period is generally 1-2 months, after which
the onset of illness may be acute or insidious. Thereafter, symptoms
may include:
- an intermittent, "undulating" fever
- headaches, chills, depression, profound weakness
- arthralgia, myalgia
- weight loss
- orchitis/epididymitis in men and spontaneous abortion in
pregnant woman
- Brucellosis lasts for days to months, and can be quite debilitating,
although the case fatality rate is very low (except in cases
of B. melitensis endocarditis).
- Chronic sequelae may include sacroiliitis, hepatic disease,
endocarditis, colitis and meningitis.
Diagnosis is based on isolation of the organism and/or serology.
A combination of doxycycline (100mg BID) (or in children, substitute
with trimethoprim-sulfamethoxazole to prevent dental staining)
and rifampcin (600-900mg/day) for 6 weeks is the treatment of
choice.
