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T/F: Brucella is the most common zoonotic disease in the world


-500,000 new cases annually

-Increasing prevalence w/ rise in tourism


How is Brucella transmitted to humans?

-Direct contact with fluid from infected animals

-Consumption-can be passed by food products (i.e. unpasteurized milk and cheese)




Identify the 6 Brucella species and the most commonly associated reservoir

1. B.melitensis (small ruminant-goats and sheep)

2. B. abortus (cattle)

3. B. suis (swine)

4. B. canis (dogs)

5. B. neotomae (desert wood rats)- not pathogenic to humans

6. B. ovis (sheep) -not pathogenic to humans


T/F: All six Brucella species cause disease in humans.


Only four are pathogenic to humans (melitensis, abortus, suis, and canis)


What are the microbiology characteristics of Brucella (morphology, gram negative/positive, etc)?

-Gram negative coccobacilli (rods)

-No spores, capsules or flagella

-Facultative intracellular aerobe


How does pasteurization prevent brucellosis?

-eliminates the organism

-reduces number of human cases


T/F: David Bruce detected Brucella in goat’s milk after British Soldiers became sick while in Malta.



Majority of worldwide cases of Brucella are attributed to B. _____________



What two strains of Brucella are more virulent to humans?

-B. melitensis

-B. suis


What regions have a high prevalence of Brucella?

-Mediterranean Basin

-Arabian peninsula

-Indian subcontinent

-Parts of Mexico

-Central and South America.


What strain of Brucella has been discovered in breast implants?

B. inopinata

-not zoonotic, but interesting and rare


What occupations are at an increased risk for Brucellosis?



-dairy-industry professionals

-micro lab personnel


How might a Brucella infection cause spontaneous abortions in cattle?

-Brucella has an affinity for tissues rich in erythritol (i.e animal uterus, breast, and placenta)

-the organism will multiply in the uterus


What is the most common Brucella species in the United States? Where are most reported cases of Brucellosis in the US?

-B. abortus

-California, Florida, Texas, and Virginia


Brucella __________ is the most widespread cause of infection, but rarely causes human disease.



Brucella ___________ is the most common type seen with disease and is the most prevalent



List the four pathogenic Brucella species in order of severity (1= most severe, 4=least severe)

1. B. melitensis
2. B. suis
3. B. abortus
4. B. canis


Contaminated sheep and goat milk with Brucella _______ seems to be the leading source of human brucellosis worldwide.



What two countries are most affected by Brucella?

Mongolia and Syria


Up until 2002, the highest burden of Brucella was in what two states?

Texas and Hawaii


T/F: Person-to-person transmission of Brucella is common.


Extremely rare, a few cases from direct tissue transplantation


How is Brucella transmitted in the environment?

-Contaminated by birth products/abortions of infected animals

-Can be spread by inhalation of contaminated dust

-Can survive for long periods of time in dust, dug, slurry, water, soil, carcasses


___________ transmission is the most common cause of Brucella exposure to humans. _______ products are more common than meat products to cause infection.


Dairy (i.e soft cheeses, fresh milk and dairy products)


Brucella is an intracellular parasite of the ____________ system that does NOT produce an exotoxin.

-reticuloendothelial system (macrophages and phagocytic cells in the lymph nodes and bone marrow)


How does Brucella cause disease?

1. Macrophages phagocytose Brucella.

2. Phagocytosed Brucella reproduce and inhibit cells critical for life functions

3. Phagocytosed bacteria travel in the blood to organs (ex. Spleen, liver, bone marrow, kidneys, and lymph nodes)

4. Bacteria secretes proteins which elicits an immune response causing granuloma formation

5. Granuloma formations destroy tissue and cause destructive disease


Describe the acute presentation of Brucellosis

-Invariable, Undulant Fever (most common symptom)

-Rigors if bacteremic

-Malodorous perspiration (wet hay-like odor)

-Constitutional symptoms (fevers, chills, night sweats, weight loss)

-Chronic fatigue symptoms may develop

-Nonspecific physical exam may see swelling of particular organs (ex. lymphadenopathy, hepatomegaly/splenomegaly)


What are the most common symptoms of acute Brucellosis?





T/F: About 50% of Brucellosis cases are acute



What is the incubation period for Brucellosis?

Usually 5-60 days

1-2 months common


In subacute cases, why might a person not seek treatment?

-The onset is insidious and subacute infection presents with nonspecific symptoms (malaise, fevers, chills, fatigue, night sweats, weight loss, headache,etc.).

-Individuals may confuse the infection with a cold that the immune system clears without intervention.


______________ disease is the most common presentation of focal brucellosis usually seen in acute infection. Peripheral arthritis and _________ are the most common subclassifications seen. Complications are linked to the __________ serotype, which may express presentations around the bones of the spine.





T/F: Osteoarticular disease can present as peripheral arthritis, sacroliitis, and spondylitis.


Peripheral arthritis: most common, non-erosive, involves knees, ankles, wrists, and hips, seen in acute infection

Sacroiliitis: inflammation of bones around the sacrum (lower back) seen in acute infection

Spondylitis: inflammation of space between vertebral discs propensity for lumbar spine, difficult to treat


____________ system is the most common site of focal brucellosis, which carries a potential risk for _________.

-Reproductive system

-Spontaneous abortion


What are the clinical presentations of Brucellosis in various body systems?

1. Bones: osteoarticulitis (peripheral arthritis, sacroiliitis, spondylitis)

2. Reproductive system: epididymoorchitis in men, spontaneous abortion

3. Liver: hepatitis (tranaminasemia, abscesses and jaundice-rare)

4. CNS: Meningitis, encephalitis, meningoencephalitis, meningovascular disease, brain abscess, demyelinating syndromes

5. Cardiovascular: endocarditis


Endocarditis is the principal cause of mortality associated with Brucella. How does the disease progress and lead to fatality?

-overtime the heart forms infective vegetation’s on the valve (usually aortic) that leads to physical changes and decreased functionality

1. Bacteria stick onto a valve of the heart

2. Accumulate more bacteria and thrombotic material (plateletes, fibrin, etc.) that creates a vegetation on a valve

3.Bactetria produce materials (chemicals like chemokines and proteins) with resistance factors against treatment (i.e. antibiotics)

4. Valvular dysfunction (pressure changes, valves stop working, inefficient blood flow)

5. Physical changes in heart that can lead to heart failure


Brucella endocarditis is _____ and effects 1-5% of infected individuals. Patients with endocarditis likely have/had underlying cardiac conditions. Most frequently the ______ valve is affected. _______ ventricular failure is most common.





How does Brucella affect animals?

-usually infects animals in endemic areas

-asymptomatic with initial infection

-localized reproductive tract (epididymus and orchitis in M and placentitis in F)

-may cause spontaneous abortions and still births


Sheep and goat Brucella infections are highly contagious because of _________ of B. Melitensis and the proximity of herd members.

Pathogenicity (how severe)


With brucellosis Ig_ against the LPS appears during the first week of infection. Ig_ appears during the second week of infection. Both peek at 4 weeks. IgM persists at _______ levels than IgG after 6 months. If Ig_ and Ig_ persist for longer than 6 months then a person has chronic brucellosis.

-IgM (acute factor)

-IgG (chronic factor)


-IgA and IgG


What is the gold standard of for Brucellosis diagnosis and why

-Blood culture (isolation of bacterium from blood or tissue sample) or Bone marrow culture (harder to obtain)

-Propensity for reticuloendothelium

-takes long period of time


Titers> _________ plus history of clinical presentation with Brucella are necessary for diagnosis.



What are some drawbacks to agglutination test (aka milk ring test)?

-can’t detect B. canis***

-crops reactions possible

-Lack of seroconversion: false negative if patient doesn’t make antibodies


What prevents seroconversion when performing diagnostic testing for Brucellosis?

1. May too early in the course of infection for the body to produce IgM and IgG

2. Presence of blocking antibodies => “Prozone” phenomenon: prevents agglutination due to excess antigen, excess of non-specific serum factors => false negative


Describe the prozone effect. (Brucella)

-The body of the infected host produces high amounts of (blocking) antibody that prevents natural Brucella antibodies from binding.

Produces a false negative result upon diagnostic testing due (not detecting antibody of interest)


What is the treatment for Brucellosis?

Doxycycline (bacteriostatic) and rifampin for 6 weeks

-Combination is ideal


What are general control measures that could be implemented for Brucella?

-Safe farming and good personal hygiene

-PPE (gloves, protective clothing, sanitary tools)

-safe disposal of aborted fetus

-food safety (store soft cheese for 6 months, food acidification to pH<3.5, pasteurize milk (80-85 C) especially if in an area where brucellosis is high, cook meats)


What are animal control measures that could be implemented for Brucella?

-choose animals from Brucella free herds, isolate new animals for 30d

-diagnose abortion causation, premature births, and other clinical signs w/ lab assistance

-routine surveillance of herds and flocks (milk ring test)

-vaccination (most successful method for prevention and control)


What is the best Brucella surveillance for the four main reservoirs?

Cattle: milk ring test (dairy), blood sample (beef)

Pigs, Sheep, Goats: blood sample


What is the milk ring test (MRT)?

-simple and effective, but only works for cows

-drop of hematoxylin-stained antigen into a sample of cow’s milk

If Brucella antibody is present, a blue ring of cream will appear at the top of the tube/glass


How did the US Department of Agriculture Cooperative State-Federal Brucellosis Eradication Program try to eliminate Brucella? What is the prevalence of Brucella in domestic herds now?

-Tested animals for Brucella

-Slaughtered any positive animals or animals exposed to positive animals, traced back exposure, vaccinated animals

-Surveillance: MRT, market cattle identification (blood test)

-No longer found in domestic herds in the US


What organism causes Q Fever

Coxiella burnetii


How is Q fever distributed across the globe?

Worldwide except Antarctica and New Zealand


How does Q fever infect a host?

-Using a passive mechanism, the bacteria survives within the phagolysosome of a macrophage

-Produces spores to withstand harsh environments

-Antigenic variation/phase variation (phase I highlight infectious)


What are Q-fever reservoir species?

-Goats, sheep and cattle (main reservoirs)




- Ticks


How is Q Fever transmitted to humans?

-organism excreted in urine, feces, milk, and birth fluids

-inhalation of the organism from contaminated environments (most common, only need 1-10 organism to be infected)

-raw milk (occasionally)


T/F: Coxiella (Q Fever) is one of the most infective species in the world


-Only takes 1-10 organisms

-70% morbidity

-potential bioterrorism (especially w, ability to form spores)


Q. Fever has an incubation period of ________

Most commonly: 20 days (range of 14-39 days)


What are the symptoms of Q. Fever?

-Nonspecific symptoms (headache, fatigue, malaise, chills, fevers, night sweats)

-retro-orbital pain

-self-limited febrile illness (2-14d)

-most are asymptomatic


What are the severe complications of chronic Q-fever?



-Neuro complications


What is the general course of disease for Q fever?

1. Exposure

2. Acute Q Fever (primary infection)

3. Chronic infection (if pregnancy: abortion or chronic carriage, endocarditis, cancer)


T/F: Most individuals with Q fever are asymptomatic.


The infection may self resolve


T/F: Chronic Q fever will more commonly lead to endocarditis.

True; it’s the main consequence of chronic infection


Over the years, the number of Q Fever cases have ______ due to _______ diagnosis and reporting. People of ________ age are more likely to present symptoms. While it may seem like _____ are more at risk, their immune systems are stronger and able to fight off infection..






T/F: There is high incidence of Q Fever in urban areas.


High incidence in rural areas (farming, sheep and goats)


How is Q fever detected?

Serology to determine antigenic phase


What are the antigenic phases of Q fever and how do they relate to the course of disease?

Phase I: acute infectious phase

Phase II: less virulent, susceptible

Chronic infection: High Phase I and Phase II Ab

Acute: high phase II Ab


T/F: Phase II antibodies present before phase I in Q Fever.


-Phase II is detectable during acute Q fever, whereas high levels of phase I antibodies are detectable during chronic Q fever

-acute is antiphase II IgG >/= 200 and IgM >/= 50


What is the treatment for Q Fever?

Doxycycline for 2 weeks