Download Diagnosis in Animals

BRUCELLOSIS
Brucellosis is also known as Bang’s Disease.
Brucellosis is known as a contagious abortion disease in animals.
In humans, the disease is known as Malta fever, Mediterranean fever, and
undulant fever.
The disease is named after Sir David Bruce, an English army surgeon who
identified the cause of the disease in 1887.
Sir David Bruce found the causative agent to be Bacillus melitensis. He
found the bacteria in the spleens of British soldiers who died of undulant
fever on the Mediterranean island of Malta.
Several years later the infection in these British soldiers was traced to
the soldier’s drinking contaminated goat’s milk.
In 1897, Brucella abortus was isolated and identified from an aborted bovine
fetus by Danish veterinarian, Dr. Fredrick Bang.
The infection in cattle became known as Bang’s disease and was eventually
proven to be ubiquitous in many animals.
Brucellosis is one of the most serious diseases of livestock because of the
damage it causes:
decreased milk production
weight loss
loss of young
infertility
lameness
Note: Brucella spp. Was the first microbe that the
United States chose to develop as a biological weapon
The reasons it was chosen, include its ease of
manufacture, susceptibility to sunlight and its ability to
be spread by aerosol dispersion or by contaminated food
or milk.
It has the advantage of being debilitating to people
without being fatal.
Its development as a biological weapon was stopped in
1967, and later President Nixon banned development of
all biological weapons on November 25, 1969.
Causative Agent (Pathogen)
A contagious bacterial disease:
Br. abortus
cattle and bison
Br. suis
swine
Br. canis
dogs
Br. melitensis
sheep and goats
Brucellosis only occasionally affects horses and cats are relatively resistant to the
infections.
Depending upon how an animal contracts brucellosis, a different species of Brucella
may be causing the infection.
For example: pigs, sheep and goats that are in contact with infected cattle can be
infected with Br. abortus.
Dogs that ingest placentas from farm animals may be infected with
Br. abortus, Br. susis, and Br. melitensis.
Brucella spp. Are a gram negative coccobacilli
( rods that are so short that they resemble cocci )
The bacteria infect the placenta, uterus and fetus, causing abortion in females.
It also infects the testes and accessory sex glands causing orchitis and accessory
sex gland infection in males.
It can cause infertility in both sexes.
Br. Abortus and Br. Canis cause mild disease in
humans, whereas Br. Suis and Br. Melitensis can be
fatal.
Brucellosis has a worldwide distribution and can affect a variety of animals.
In the United States and Europe brucellosis is uncommon as a result of its
elimination from cattle herds.
Br. melitensis
* in sheep and goats represents the most important source of
brucellosis in humans
* it is not enzootic in the United States, Canada, northern
Europe, Australia, or Souteast Asia
* prevalent in Latin American, Mediterranean area, Central
Asia and the countries around the Arabian Gulf.
* Humans are infected by the handling of animals during
the birthing process and the consumption of raw milk
products (especially fresh soft cheeses)
Br. suis
* affects both sexes of swine
* causes infertility, abortion, orchitis, bone/joint lesions
* prevalence is generally low
* occurs in areas in which pigs are kept, including southeastern
United States and Australia where populations of feral swine
are heavily infected.
* Human infections occur in people handling pigs on farms and during
slaughtering and processing feral and domestic swine.
Br. abortus
* has been eradicated from Canada, Japan, northern Europe
and Australia
* Cases in humans are sporadic and are acquired by:
drinking unpasteurized milk
working with infected cattle at a slaughter facility
by attending infected parturient cattle
accidental inoculation with live vaccine
Br. Canis
* infection in humans tends to occur in dog handlers
In the United States, the frequency of brucellosis is related to the
number of infected animals.
Infected animals are rare in the United States and pasteurization of milk
has eliminated that mode of transmission
Occupational exposure (cattle-workers, veterinarians, slaughterhouse
workers) is the main transmission route in the United states.
The incidence is approximately 200 cases per year.
People with Brucellosis in the United States are primarily found in Texas,
California, Virginia and Florida
Pathogenesis
Once in the body, Brucella spp. are engulfed by neutrophils and are carried
In the lymphatic fluid to the lymph nodes draining the infected area.
The infected neutrophils release bacteria into the blood and bacteria
localize in certain organs.
liver
spleen
bone marrow
kidney
The gross lesions seen in an animal are subtle and rarely diagnostic.
In cows, placental lesions include:
edema
necrosis
brownish odorless discharge
In aborted bovine fetuses:
edema
bronchopneumonia
In bulls:
scrotum becomes enlarged and thickened
In swine:
formation of white nodules on the uterus of females
formation of white nodules on the testes of males
lesions in both sexes of the spleen, liver, kidney, lymph nodes
and bone
In sheep:
edema and inflammation of the epididymis in rams
necrosis of the placenta in ewes
inflammatory changes in the lung, liver, lymph nodes
spleen and kidneys of lambs
In dogs:
uterine and placental lesions in females
orchitis in males
bronchopneumonia in pups
The incubation period of brucellosis is variable ranging from 2 weeks to 1 year or
longer.
Note: the typical length is 30 to 60 days.
Diagnosis in Animals
Tissues infected with Brucella spp. do not provide distinctive findings.
Diagnosis in animals consists of bacteriologic or serologic identification.
Treatment in Animals
Treatment of infected animals is not attempted because animals may recover
from the disease signs but do not clear the infection.
Management and Control in Animals
Measures for prevention and control of brucellosis include vaccination of
calves, periodic testing of bulk milk from farms, blood testing of adults and
slaughtering of infected animals.
In the United States a federal program for brucellosis eradication called the
Cooperative State Federal Brucellosis Eradication Program has existed since 1934.
States are deemed brucellosis free when none of their cattle or bison is found to be
infected for 12 consecutive month under an active surveillance program.
Clinical Signs in Humans
Brucella spp. are able to establish an infection by surviving phagocytosis
and are passed from the lymph to blood and then to organs throughout the
body.
The organs mainly affected are the liver, spleen, and bone marrow.
In humans the incubation period is typically 5 to 60 days (or longer)
The most prominent symptoms are;
weakness
loss of appetite
chills
headache
back pain
intermittent (undulating) fever
It persists for weeks to months if left untreated.
Chronic infection can damage joints and the spinal cord.
Diagnosis in Humans
Diagnosis is primarily dependent on:
clinical suspicion
adequate history of possible exposure (including
travel)
isolation of the organism
Brucellosis in humans is very hard to diagnose. An undeniable diagnosis
requires isolation of the organism using blood culture as the method of
choice.
Culture from bone marrow, blood and affected organs may be successful.
Treatment in Humans
Humans are treated with antibiotic combinations for 4 to 6 weeks.
No widely accepted vaccines for humans have been developed.
All material taken directly from Understanding Zoonotic Diseases by Janet Amundson Romich published by Thomson/Delmar Learning.