Bacteria with Animal reservoirs/ Insect Vectors

Question 1

Brucellosis (Brucella)

Answer 1

• Facultative intracellular parasites causing chronic disease, which usually persists for life.
• four types: goats/sheep, cattle, swine, dogs
• enter through lungs, through skin, oropharynx
• produces UNDULANT FEVER (waxes and wanes)
• multiply in macrophages (lymph nodes, spleen, liver): multi-organ non-necrotizing granulomas
• common complications: spondylitis, arthralgia, meningitis, endocarditis–treat with tetracycline -usually self-limited. mortality <1% due to endocarditis.

Question 2

Yersinia pestis

Answer 2

• Gram-negative rod-shaped coccobacillus. It is a facultative anaerobe
• survive/proliferate inside macrophages (granulomatous + necrotizing)
• Produces plasminogen activator: hemorrhaging
• Bubonic plague: spread by fleas on rats-septic shock and bulbous enlargements of lymph nodes
• Septicemic plague: direct blood contamination (death quick-48 hours)
• Pneumonic plague: inhalation of airborne particles, necrotizing pneumonia-hemoptysis-endotoxic shock in 1-2 days after infection period which follows 2-5 day incubation -tetracyclin with streptomycin

Question 3

Tularemia (Francisella tularensis)

Answer 3

• reservoir in rabbits and rodents infection from contact; vector is ticks, deerflies, and mosquitoes.
• metastatic infection–survives within macrophages (granulomatous reaction)
• Acute febrile disease, lymphatic distribution.
• Distribute to major organs via lymph => enlarge, hard nodes => granulomas (necrotizing, described as ‘palisading’)
• Ulceroglandular: pustular lesions (necrosis) with lymphadenopathy and acute febrile illness–significant mortality if untreated
• Occuloglandular = Spread from eye to parotid gland

Question 4

Anthrax (Bacillus anthracis)

Answer 4

• Gram-positive, endospore-forming, rod-shaped bacterium
• spore form in dead animals/soil and reservoir in goats/sheep/cattle/dogs/pigs/horses
• spread through inhalation, breaks in skin, ingestion with germination in body
• Malignant pustule: Cutaneous form (most common) papule/ulcer–lymphadenitis can lead to septicemia. (without dissemination–self-limited no complications)
• Pulmonary: “woolsorter’s disease” respiratory failure and shock within 24-48 hours.
• Septicemic: DIC, exotoxin depresses respiratory center–antibiotics ineffective against exotoxin
• Gastrointestinal: rare, eating contaminated meat: stomach + bowel ulceration–death caused by fulminant diarrhea and massive ascites

Question 5

Listeriosis (Listeria monocytogenes)

Answer 5

• reservoir: many species of mammals and birds–rare spread from animal to human
• spread: unpasteurized milk and dairy products
• evades intracellular + extracellular host responses: acidic phagosome activate listeriolysin O exotoxin–escape into cytoplasm and usurps cytoskeleton to form portrusions to dock with other cells (spread without staying in extracellular environmentz)
• Pregancy listeriosis: lead to abortion or premature delivery
• Septicemic listeriorsis: severe febrile illness in immunocompromised–shock and DIC: death without treatment (heavy duty antibiotic course needed)
• Self-limited in healthy host

Question 6

Cat-Scratch Disease (Bartonella henselae)

Answer 6

• proteobacteria
• spread from cat scratches inoculated skin or contact with eye.
• papule at site of infection
• invades macrophages–granulomatous–lymphadenopathy
• swollen lymph nodes persist for months
• Parinaud oculoglandular (granulomatous conjunctivitis with swollen facial lymph nodes) syndrome secondary to conjunctival infection

Question 7

Glanders

Answer 7

• Rare, granulomatous disease.
• Zoonotic; associated with horses.
• Burkholderia mallei aka pseudomonas mallei
• Transmission via cuts in the skin, via musoca, or inspiration.
• invade macrophages-acute granulomatous infection
• Nodular lesions in the lungs and ulceration of the mucous membranes in the upper respiratory tract
• Acute bacteremia => Almost always fatal. Generally a 50% mortality rate and very small minimum infectious dose.

Question 8

Bartonellosis (Bartonella bacilliformis)

Answer 8

• aka Carrion’s disease
• gram(-) pleomorphic bacteria
• vector: sandflies of Peru, Ecuador, Colombia
• proliferates in endothelial cells then invades erythrocytes–hemolysis
• Oroya fever: acute hemolytic anemia–untreated leads to 40% mortality rate
• verruga peruana: dermal eruptive phase–eruptive lesions-purulent and blood and ulcers that limit joint movement (osteoarticular pain)