Zoonotic Bacterial Diseases Flashcards
1
Q
Societal factors leading to emergence of zoonotic infections
A
- Agricultural and pastoral
- Migration to city - have largely become occupational (farmers, vets, slaughterhouse workers, lab workers, etc.) and avocational (pet owners, hikers/hunters/trappers/fishermen)
- Destruction of animals habitats –> animals come into city
2
Q
Major pathways of transmission of zoonotic infections
A
- Cutaneous transmission, including bites
- Arthropod vector
- Inhalation
- Ingestion
3
Q
Individuals at highest risk for zoonotic infections
A
- People with occupational or avocational exposure to animals
- Occupational:
- Farmers
- Vets
- Slaughterhouse workers
- Lab workers
- Avocational:
- Pet owners
- Hikers
- Hunters/trappers/fishermen
4
Q
Plague: epidemiology
A
- Caused by Yersinia pestis (facultatively intracellular Gram-negative rod)
- Generally accepted as etiological agent for Black Death in Europe
- Small pandemics up until about 1920, when rats on ships were “outlawed”
- Spread by fleas (in CO, watch out for dead prairie dogs)
- Discovered by a guy named Yersin (–> Yersinia)
5
Q
Types of plague
A
- Bubonic plague
- Septicemic plague
- Pneumonic plague
6
Q
Bubonic plague
A
- Most common form of plague in US
- Lymph gland swelling resulting from flea bite 2-5 days earlier
- 60-90% mortality if untreated
- Lymph nodes extremely painful and swollen (buboes)
- Usually inguinal or axillary
7
Q
Septicemic plague
A
- Invasion of almost all organs
- No evidence of prior disease
- Seems to come after direct bloodstream inoculation or consumption of plague-stricken animal
- Death occurs in 12-24 hours
- Presents with ecchymoses, petechiae, and DIC
8
Q
Pneumonic plague
A
- Less common but nasty
- Transmitted human to human through aerosolized droplets
- Primary or secondary lung infection
- Highly infectious and 100% fatal if untreated
- Untreated bubonic plague can get into lungs –> pneumonic plague
9
Q
Epidemiologic terms for plague
A
- Enzootic plague
- Stable rodent-flea infection
- Not too much rodent mortality
- Long-term reservoir
- Epizootic plague
- Occurs when plague bacilli introduced into rodent/small mammal populations that are more susceptible
- Zootic plague
- Transmission from animals to human
- Demic plague
- Transmission from human to human (pneumonic plague only)
10
Q
Plague: appearance and prevention
A
- Microscopically:
- Bipolar, safety-pin type staining of Gram-negative rods (ends stain more than middle)
- Animal reservoirs:
- Cats, rabbits, camels
- Virulence:
- Has to do with how well Yersinia gets into non-endocytosing cells
- Can kill or shut down macrophages
- **VW **and **F1 **surface antigens cause extra virulence (encoded by plasmids)
- Starves flea to make it keep biting people, then causes flea to regurgitate Yersinia-containing blood back into host
- Can be weaponized (pneumonic form most lethal)
- Prevention: avoidance
11
Q
Tularemia
A
- Caused by *Francisella tularemia *(Gram-negative coccobacillus)
- Carried by rabbits
- Generally found in and around AR and MO
- Requires cysteine for growth
- Most cases are ulceroglandular
- Direct contact with infected animals –> skin ulcers
- Ulcers: black and well-demarcated + local swollen lymphadenopathy
- Some are pulmonic
- Inhalation of aerosolized rabbit - for real
- Can also get it from tick bites or ingestion of contaminated material
- Extremely virulent (10 organisms cause disease)
- Unlike plague, cannot be spread person-to-person
- Can be weaponized (pulmonary form most lethal)
- Prevention: avoidance
12
Q
Brucellosis
A
- Mostly acquired in US from consumption of unpasteurized goat cheese from Mexico
- Doesn’t cause primary skin ulcers or buboes
- Presents with systemic relapsing-remitting flu-like symptoms (undulant fever)
- Rarely fatal
13
Q
Lyme disease: cause and presentation
A
- Caused by Borrelia burgdorferi, a spirochete
- Very hard to culture
- Spread through Ixodes tick bites
- Causes **arthritis **(knee), fever, and skin rash (erythema migrans - spreading erythema with a pattern of central clearing)
- Skin rash is pathognomonic
- Symptoms caused by immune response (very high levels of IL-1)
- Can present a lot of different ways, but most common:
- Erythema migrans
- Heart palpitations
- Arthritis
14
Q
Lyme disease: stages of infection
A
- Stage I
- Localized infection
- Erythema migrans
- Stage II
- Disseminated infection
- Meningitis
- Carditis
- Myositis
- Stage III
- Latent infection
- Chronic arthritis
- Neuropathy
- Can go on for decades if untreated
15
Q
Lyme disease: diagnosis and epidemiology
A
- Very difficult to diagnose
- Nymph stage of tick most frequently causes disease - bug is about the size of a letter on a penny
- Once bug has fed on you for awhile, they’re no longer necessary to cause disease (not a toxin)
- Probability of getting Lyme disease increases dramatically with length of tick’s feeding (72+ hours)
- Geographically, cases clustered in:
- Northeast
- Around Minnesota (site of other hosts, white-footed mice and deer)
- Climate change –> growth of geographic range
- Cases most common in children and middle-aged