Infectious Lecture 4th Year 6-12-2016 (2) Dr.Osamah Muwafk
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Brucellosis:
It is caused by the species of Brucella and their principal farm
animal hosts are Brucella abortus (cattle), Brucella melitensis
(goats), Brucella suis (pigs), and Brucella ovis (sheep) . In general,
the principal manifestations of brucellosis are reproductive failure,
such as abortion or birth of unthrifty newborn in the female, and
orchitis and epididymitis with frequent sterility in the male.
Persistent (lifelong) infection is a characteristic of this facultative
intracellular organism, with shedding in reproductive and
mammary secretions. Brucellosis is also an important zoonosis
causing debilitating disease in humans.
BRUCELLA ABORTUS (BANG'S DISEASE)
Etiology and Epidemiology:
1. Brucella abortus
2. Major cause of abortion in cattle in countries without a
national control program.
3. Undulant fever in humans an important zoonosis.
4. Sexually mature animals susceptible
5. outbreaks occur in first-calf heifers
6. older cows infected but do not abort
7. Transmitted directly from infected animal to susceptible
animal by uterine discharges
8. Congenital infection occurs
9. Infection in wildlife species but significance to domestic
animals unknown
10.
Infection introduced into herd by unknown infected
carrier animal .
Infectious Lecture 4th Year 6-12-2016 (2) Dr.Osamah Muwafk
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11.
Natural infection and vaccination result in immunity to
abortion but not infection
12.
infected animals remain serologically positive for a
long time
PATHOGENESIS
1. B. abortus has a predilection for the pregnant uterus, udder,
testicle and accessory male sex glands, lymph nodes, joint
capsules, and bursae.
2. After the initial invasion of the body
3. localization occurs initially in the lymph nodes draining the
area
4. spreads to other lymphoid tissues, including the spleen and
the mammary and iliac lymph nodes.
5. B. abortus is phagocytized by macrophages and neutrophils
in an effort by the host to eliminate the organism
6. However, once inside the phagocyte, B. abortus is able to
survive and replicate
7. The phagocyte migrates via the lymphatic system to the
draining lymph node, where Brucella infection causes cell
lysis and eventual lymph node hemorrhage 2-3 weeks
following exposure.
8. Because of vascular injury, some of the bacteria enter the
bloodstream and subsequent bacteremia occurs, which
disseminates the pathogen throughout the body.
9. If the infected animal is pregnant, B. abortus will colonize
and replicate to high numbers in the chorionic trophoblasts of
the developing fetus.
10.
The resulting tissue necrosis of the fetal membranes
allows transmission of the bacteria to the fetus.
Infectious Lecture 4th Year 6-12-2016 (2) Dr.Osamah Muwafk
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11.
In the adult, nonpregnant cow, localization occurs in the
udder
12.
Infected udders are clinically normal but they are
important as a source of reinfection of the uterus, as a source
of infection
13.
Erythritol, a substance produced by the fetus and
capable of stimulating the growth of B. abortus, occurs
naturally in greatest concentration in the placental and fetal
fluids and is responsible for localization of the infection in
these tissues
CLINICAL FINDINGS
1. Abortion after the 5th month of pregnancy
2. In the bull, orchitis and epididymitis
3. Synovitis
4. In horses, the common association of B. abortus is with
chronic bursal enlargements of the neck and withers, or with
the navicular bursa, causing intermittent lameness (Fistulous
withers)
CLINICAL PATHOLOGY:
1. Rose Bengal test (buffered plate antigen or card test)
2. Complement fixation test
3. Enzyme-linked immunosorbent assays
4. Fluorescence polarization assay
5. Antibodies in milk (the milk ring test)
NECROPSY FINDINGS
Necrotizing placentitis and disseminated inflammatory reactions in
aborted fetal tissues are the characteristic changes
Infectious Lecture 4th Year 6-12-2016 (2) Dr.Osamah Muwafk
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DIFFERENTIAL DIAGNOSIS
1. Trichomonosis (Tritriehomomas foetus)
2. Neosporosis (Neospora caninum)
3. Vibriosis ( Campylobaeter fetus subsp.venerealis)
4. Leptospirosis
5. Mycoses (Aspergillus, Absidia)
6. Listeriosis
7. Epizootic bovine abortion
8. Bovine virus diarrhea
TREATMENT
Treatment is unsuccessful because of the intracellular
sequestration of the organisms in lymph nodes, the mammary
gland, and reproductive organs
CONTROL:
1. Test and reduction of reservoir of infection : All breeding
cattle in the herd are tested and those that are positive are
culled and sent for slaughter.
2. Quarantine : This is a period of time during which cattle
movement is restricted and the cattle are tested
3. Depopulation is slaughter of all cattle in a herd when all
animals have been exposed and are capable of becoming
infected and acting as a source of new infection
4. Vaccination : The strain 19 vaccine of B. abortus provides