Lecture 25

Question 1

what is the lifecycle of a female Sarcoptes Scabiei

Answer 1

• fertilized on skin surface
• burrows into epidermis
• completes life cycle in 5 weeks, dies in burrow

Question 2

what is the lifecycle of a male Sarcoptes Scabiei

Answer 2

• remains on skin surface or produces a shallow burrow
• shorter life span

Question 3

Sarcoptes Scabiei eggs are laid where? When does an adult mite develop

Answer 3

• eggs laid under skin
• larva emerges from egg after 4 days
• adult mite develops 2 weeks after hatching

Question 4

clinical issues caused be Sarcoptes Scabiei is due to

Answer 4

• burrowing
  
  • causes an intensely pruritic eruption, worse at night

Question 5

Sarcoptes Scabiei causes what 2 conditions

Answer 5

• crusted (norwegian scabies)
  
  • crusted scaling lesions readily observed in HIV patients
• pediatric scabies
  
  • lesions may be blood filled

Question 6

how is Sarcoptes Scabiei transmitted

Answer 6

• direct person contact
• can be zoonotic: does not last long

Question 7

how is Sarcoptes Scabiei identified

Answer 7

• apply mineral oil, scrape lesion and visualize microscopically
  
  • looking for whole mite or mite parts, eggs or fecal pellets in burrows

Question 8

What does Phthirus pubis cause

Answer 8

pubic lice - “crabs”

Question 9

how do Phthirus pubis feed

Answer 9

• nits egs cemented to hair
• adults bite and feed in pubic area

Question 10

how is Phthirus pubis transmitted

Answer 10

• sexual contact
• contaminated bedding

Question 11

Pediculosis is caused by what pathogen

Answer 11

Pediculus humanus

• P. humanus capitis: head louse
• P. h. humanus: body louse

Question 12

Pediculus humanus are blood sucking parasites that can cause what disease as a result of years of infestation

Answer 12

Vagabond’s disease

Question 13

Pulex irritans is a human flea that absolutely needs what to survive

Answer 13

blood

Question 14

main manifestation of Pulex irritans is

Answer 14

• a rash
  
  • during blood meal, it injects saliva

Question 15

do Pulex irritans live on humans

Answer 15

• no, they prefer hairer and warmer environment like pet hair

Question 16

are flea bite rashes contangious

Answer 16

no

Question 17

flea bite pattern

Answer 17

• groups of three or four, generally in a linear pattern
• characterized by raised bumps or halo surrounding the actual bite site
• concentrated in lower extremities

Question 18

scabies commonly infects what patient populations

Answer 18

children and elderly

Question 19

Lyme disease is caused by what pathogen

Answer 19

• bacterium Borrelia Burgdorferi
  
  • ​no gram reaction

Question 20

lyme disease can be classified into what two things based on location in US

Answer 20

• Ixodes scapularis: northeasten, mid-atlantic, north central US
• Ixodes pacificus: pacific coast

Question 21

ticks attach to what part of the body

Answer 21

can attach to any part of the body

Question 22

tick must be attacked to host for how long to transmit borrelia burgdorferi

Answer 22

36-48 hrs

Question 23

tick bite produces what rash

Answer 23

• Erythema migrans
  
  • bulls eye rash

Question 24

up to 20% of lyme disease patients have symtpoms that last months to years after proper abx tx: Post treatment lyme disease symptoms include

Answer 24

• muscle and joint pain
• cognitive defects
• sleep disturbance
• excessive fatigue

Question 25

how is B. burgdorferi infection diagnosed

Answer 25

* bullseye rash is key * 2 step approach 1. ELISA 1. detect B. burgdorferi 2. Western blot (confirmatory) 1. detects B. burgdorferi proteins

Question 26

Rocky mountain spotted fever is caused by

Answer 26

* tick * american dog tick * rocky mountain wood tick * brown dog tick * caused by **Rickettsia rickettsii**

Question 27

Rickettsia rickettsii * gram status * special feature * motile * shape

Answer 27

* **gram negative** * **obligate intracellular** * non motile * pleomorphic * cocci * rods * thread-like

Question 28

prognosis of rocky mountain spotted fever

Answer 28

fatal if not treated in the first few days of symptoms

Question 29

if arizona, rocky mountain spotted fever is caused by ? During what season?

Answer 29

* brown dog tick * summer months

Question 30

Rickettsia rickettsii invades what cells

Answer 30

* endothelial cells that line blood vessels

Question 31

first symptoms of rocky mountain spotted fever

Answer 31

* 2-14 days after tick bite * sudden onset of fever and HA

Question 32

rocky mountain spotted fever produces what 2 characteristic rashes

Answer 32

1. small, flat pink non itchy spots 1. wristst, forearms, ankles and spreads to trunk, palms, and soles 2. **red to purple** spotted petechial rash 1. pinpoint hemorrhages 2. sign of late infection and severe disease

Question 33

how is rocky mountain spotted fever diagnosed

Answer 33

* difficult * clinical signs and symptoms * gold standard: **indirect immunofluorescence with a R. rickettsii antigen** (2 samples 2-4 weeks apart) * do not delay tx waiting for confirmation