L9 MHD: Zoonoses Flashcards
Brucella
- What 4 animals serve as a reservoir of Brucella?
- How do humans become infected with the disease?
- Goats, cattle, pigs, dogs
- Humans infected by contact with animals (slaughterhouse, veterinarians, farmers, lab techs) or by ingesting contaminated milk or dairy
* Especially unpasteurized goat cheese*
Category A bioterrorism agents are high-priority agents that pose a risk to national security (easily disseminated, result in high mortality rates, cause panic). Name 3 Category A bioagents.
- Bacillus Anthracis (anthrax)
- Yersinia Pestis (bubonic plague)
- Francisella Tularensis (Tularemia)
Category B bioterrorism agents are the 2nd highest priority agents that are moderately easy to disseminate, result in moderate morbidity rates/low mortality rates, and require specific enhancements of CDC’s diagnostic capacity. Name 3 category B agents.
- Brucella Species (Brucellosis)
- Food safety threats (Salmonella species/E.Coli O157:H7, Shigella)
- Burkholderia Pseudomallei (Melioidosis)
Emerging infectious diseases such as Nipah virus and hantavirus are examples of what category bioterrorism agent?
Category C
-3rd highest priority that includes pathogens that could be engineered for mass dissemination in the future because of availability, ease of production, and potential for high morbidity/mortality rates.
What animal do the following Brucella species originate from?
- Brucella Melitensis
- Brucella Suis
- Brucella Abortus
- Brucella Canis
-B. melitensis: Goats, Sheep, Camels (most virulent!)
-B. suis: Pigs
B. abortus: Cattle
B. canis: Dogs (least common)
Describe the pathogenesis of Brucella
- Organisms penetrate skin/mucosal membranes
- Phagocytosized by macrophages/monocytes
* *facultative intracellular organisms** - Carried to spleen, liver, bone marrow, lymph nodes, and kidneys
- Organisms multiply in macrophages in RE system
- Host reaction is the formation of small granulomas
How does a humoral antibody affect the outcome of a Brucella infection? Cell-mediated immunity?
Brucella= intracellular organism of the reticuloendothelial system
- Humoral Ab does NOT affect outcome, T-Cell immunity determines recovery
- Organisms are able to survive intracellularly because they inhibit polymorphonuclear leukocyte degranulation
- Predilection for erythritol rich tissues in animals
- *placenta in animals- results in spontaneous abortions**
Brucella Clinical Manifestations
- How long until symptoms appear?
- What are the initial symptoms?
- What is the key clinical feature of the disease?
- What organs are enlarged?
- Symptoms appear 2-8 wks after exposure
- Initial: non-specific symptoms (people feel like they have the flu): malaise, chills, sweats, fatigue, weakness, myalgias
- Key clinical feature: UNDULANT FEVER- a fever that is intermittent/cyclical. Organisms sequestered in granulomas in tissue/BM. Release of organisms into circulation causes reappearance of fever! TEST
- Splenomegaly, lymphandenopathy, hepatomegaly
What are the signs of advanced disease with a brucella infection?
- GI symptoms (70%)
- Osteolytic lesions/joint effusions (20-60%)
- Respiratory symptoms (25%)
* *Less common: CNS (meningitis/meningoencephalaitis), CV manifestations (endocarditis with septic embolization), GU tract (orchitis, renal granulomas), ocular - Chronic infections (patients can be chronically ill for over 12 months)
- What is the preferred way to diagnose Brucella?
2. Serological tests look for what?
- Preferred method of Dx: Blood cultures with extended incubation time
* *Brucella is slow growing**
- Bone marrow is the preferred site (best yield but most invasive), culture can also be taken from blood, liver, or lymph nodes - Serology tests: presumptive diagnosis
- Looking for titers of Ab against Brucella or elevated febrile agglutinin titer
- Four fold rise in titer indicative of disease
- Single titer of >1:80
- Antibody titer >1:160 (seen in 5-10% of the population living in endemic areas)
Describe Brucella’s morphology
- What does a gram stain show?
- Fast or slow growing?
- Preferred growth media?
- Poorly staining, small coccobaciliary gram negative rod (looks like grains of sand)- VERY TINY
- Slow growing
- Requires enriched media (chocolate agar with cysteine crystals) to grow and prolonged incubation
- What is the best way to treat Brucellosis?
2. How long must the disease be treated?
- Oral tetracyclines along with ahminoglycosides (gentamicin/streptomycin)
* *treatment involves agents that penetrate and have activity within phagocytic cells!** - Because of the chronic nature of some infections (brucella getting into the bone marrow- periodically gets released), disease must be treated for a prolonged time
Relapses occur in 10% of Brucella patients.
What are 2 ways of controlling the disease? Is a vaccine available?
- Controlled by immunizing livestock
- Tell patients to avoid unpasteurized milk and dairy products
No human vaccine available.
Meat factory workers, veterinarians, farmers, and travelers who consumed dairy in Mexico are at risk of what disease?
Brucella
The following: “ Glandular Fever” “Rabbit Fever” “Tick Fever” “Deer Fly Fever” “Ohara Disease” are all names for what zoonotic agent?
Tularemia
- How does a pt get a Tularemia infection?
- What is the causative agent?
- In what 3 states is tularemia most prevalent?
- Disease is caused by handling infected rabbits (animal contact) or by deer fly/tick bites, contact with cat who caught an infected rabbit, consumption of contaminated meat/water, inhalation of infectious aerosol in lab or while dealing with the infected animal
- Causative agent = Francisella Tularensis
- Most patients are men (hunters) who live in Arkansas, Oklahoma, and Missouri
Describe the pathogenesis of Tularemia
-How many pathogens needed to cause infection?
- Organisms enter through breaks in skin or mucous membranes
* *Ulcer may develop at entry site** - Disseminate via bloodstream to regional lymph nodes
- Host response is granuloma formation (like Brucella)
Tularemia is very virulent! Only a limited number of pathogens needed to cause an infection!