Brucella Species, a bacteria.
Brucella are gram-negative coccobacilli as you see on the
They’re aerobic, facultative and intracellular bacteria.
Also, they’re non-encapsulated.
This means that they have somewhat difficult or fastidious
The Brucella are interesting because they are one of several
that cause zoonotic diseases
or as we like to say in the world of infectious diseases,
they’re fascinomas, the zebras.
Zonoses typically come from known animal sources
such as in the case of Brucella, cattle, goats, sheep, and
One can acquire Brucella by ingesting unpasteurized dairy
for example, goats or cattle, as well as contact with an
infected animal host.
As you see on the top image, the young lady is playing with
the very cute goat.
You know for a fact that she will soon be swapping saliva by
kissing or licking
with the same goat and potentially being exposed to
The image on the lower is cheese which maybe if it’s coming
from goats or chèvres,
may be unpasteurized and in certain parts of the world,
unpasteurized dairy coming from goats is a known source of
But also, farmers, veterinarians, slaughterhouse workers,
anybody who works with the zoonotic animals you see listed
above are all at risk for acquiring Brucella
either through direct contact or through inhalation of
How does Brucella cause its disease?
This is yet another example of the organism entering into a
white blood cell to escape detection.
And in this case as you see on the image, Brucella is
ingested by or phagocytosed by a macrophage.
However, it again is resistant to intracellular killing.
It prevents the fusion of a lysosome or an enzyme-containing
vacuole with the phagosome
and thus, it’s able to replicate itself while also evading
This replication or growth continues and then, allows it to
spread within its carrier to other parts of the body,
typically, in immune tissues such as the spleen, liver,
lymph nodes, and bone marrow.
Ultimately, it exits its host macrophage and then, so,
doing, causes cell death.
This finally is the trigger for other immune cells including
the TH1 or T Helper 1 response
to be activated and to respond to the Brucella with antibody
with cytokine production and ultimately, creating a
granuloma around the site of the infection.
What does Brucella disease look like? Well, Brucellosis is
the typical description,
although, there are many different words for Brucella
associated disease around the world.
Some call Brucellosis undulant fever which is a reference to
the undulating pattern of the fever.
It’s a cyclical process.
Typical patients with Brucellosis have malaise, fever, and
rigors or chills, night sweats, and fatigue.
Along with that, they may have weight loss and many of them
have reactive arthritis or arthralgias.
The arthritis as you see on the image many times is of the
and it may resemble rheumatoid arthritis such as older
individuals experience later in life.
The undulating fever pattern along with the reactive
arthritis is a suggestion that Brucella is the likely
although, not specific to that diagnosis, the combination of
those two is quite striking.
A way for me to remember undulating fever is to think of the
udder of a cow as the cow walks back and forth
and underneath the udder, you can see the swinging pattern
back and forth, a cyclical pattern of the fever.
Brucellosis exists primarily in an acute form although,
there can be a subacute onset, a slow onset
but it is especially problematic when it occurs in a chronic
and in fact, chronic Brucellosis is one of the many, many
known causes of fever of unknown origin.
Prevention and treatment, most importantly, is to prevent
disease in the animals
and if that’s not possible, to at least pasteurize the dairy
Again, it is unpasteurized goat and cow associated dairy
products which are the primary risk for Brucellosis.
Treatment for non-pregnant adults consists
of an oral regimen of doxycycline and
However, for women in early pregnancy, they
should be treated with rifampin plus
trimethoprim sulfamethoxazole, while those
in late stage pregnancy receive
only rifampin until delivery.
The trimethoprim Sulfamethoxazole is avoided
in late pregnancy to prevent any
risk of neonatal or chronic stress.
Remember, however, to also give a folic acid
supplement when treating those pregnant women
with late stage pregnancy.
Relapses can occur and if you think about where Brucella
it’s hiding within immunologic tissue, within macrophages,
within the spleen, within lymph nodes
and, so, it makes sense that one would have to treat a long
to gain entry into those protected immunologic sources.
Thus, prolonged therapy is the way to go.
So, Brucella is definitely a zoonotic process.
It is something to consider for that patient with prolonged
and it is one of the reasons that in infectious diseases, we
ask the interesting questions,
not what did you have for breakfast, but how much goat
cheese did you have?