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Microbiology Unit 3 > 6 Ectoparasitic Infections > Flashcards

6 Ectoparasitic Infections Flashcards

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Biology 101 flashcards
1
Q

Burrowing mite that is the most serious of the mites

A

Sarcoptes scabiei

Close relatives of ticks

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2
Q

Ectoparasite that leads to scabies, crusted scabies, mange, seven-year-itch, etc

A

Sarcoptes scabiei

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3
Q

Morphology of Sarcoptes scabiei

A

Small mite with SHORT legs

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4
Q

What does the female sarcoptes scabiei life cycle look like?

A

Fertilized on the skin surface

Burrows into the epidermis

Female completes the life cycle in 5 weeks, dies in the burrow

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5
Q

What does the male sarcoptes scabiei life cycle look like?

A

Shorter life span

Remains on the skin surface or produces a shallow burrow

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6
Q

Where does the sarcoptes scabiei mite lay its eggs?

A

Under the skin

Larva emerges from the egg after 4 days incubation

Adult mite develops 2 weeks after hatching

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7
Q

Main clinical manifestation of scabies is …

A

PRURITIS

The first time someone is infested with S. scabiei, sensitization (allergic response) takes weeks to develop

In reinfections, pruritis can develop within 24 hours

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8
Q

_______ causes the majority of clinical issues with scabies

A

Burrowing

Causes an intensely pruritic eruption that is worse at night

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9
Q

What is Crusted (Norwegian) Scabies?

A

Incubation period of ~1 month

Crusted scaling lesions that are intensely pruritic

Observed readily in HIV patients

Lesions are teeming with hundreds of thousands of mites

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10
Q

What is pediatric scabies?

A

Similar to norwegian scabies but lesions may be blood filled

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11
Q

Scabies is usually transmitted by…

A

Direct person to person contact

In adults, it is likely an STI

Can be zoonotic (rarely)

Found in crowded living conditions

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12
Q

How to identify scabies

A

Apply mineral oil, scrape lesion and visualize microscopically

Looking for whole mite or mite parts, eggs, or fecal pellets in burrows

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13
Q

What is the treatment for scabies?

A

5% permethrin cream (single application) applied over all body below neck, washed off only after 8-14 hours

Can also use Ivermectin but it does not kill eggs

Clinical findings should subside within 2 weeks (if not, retreat)

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14
Q

Besides the medical treatments, what else should you tell scabies patients to do?

A

Warn of issues with absorption of topicals

Thoroughly wash all bedding and clothes in hot water

Examine all sexual partners for signs of infestation

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15
Q

What is the organism responsible for “crabs”

A

Phthirus pubis - pubic lice

Dwells on pubic hair

Nit (eggs) cemented to hair, adults bite and feed in pubic area

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16
Q

Transmission of phthirus pubis is via…

A

Sexual contact or contaminated bedding

ID by visualizing louse or nit

17
Q

How do you treat phthirus pubis?

A

Permethrin

18
Q

How is Pediculus humanus different from Phthirus pubis?

A

Longer, shorter legs

Two different species
• P. humanus capitis = head louse
•P. humanus humanus = body louse

19
Q

Vector for epidemic typhus

A

Pediculus humanus

20
Q

What does the life cycle for Pediculus humanus look like?

A

Nit is cemented to a fiber in clothing or in human hair

Egg-to-egg cycle takes about 3 weeks

21
Q

What is the pathogenicity of pediculosis?

A

Bite irritation (blood sucking parasites)

“vagabond’s disease” as a result of years of infestation

Darkened, thickened skin

22
Q

How is P. humanus spread?

A

Easily

Especially in crowded conditions, conditions where clothing cannot be changed often

23
Q

Treatment for P. humanus

A

Permethrin

Many OTC treatments available

24
Q

What is the scientific name for the human flea?

A

Pulex irritans

25
Q

What does Pulex irritans look like?

A

1-4 mm in length

Laterally compressed

Short spikes on legs that allow attachment to host

Parasites that absolutely need blood to survive

26
Q

Main manifestation of flea infestation is…

A

Rash

During a blood meal, flea injects saliva, known to posses at least 15 substances which initiate allergic responses

27
Q

Treatment for pulex irritans

A

Cessation of scratching

1% hydrocortisone

Antihistamines

28
Q

Rocky Mountain Spotted Fever is caused by what organism

A

Rickettsia rickettsii

Gram negative obligate intracellular non-motile pleomorphic bacterium spread by ticks

29
Q

Rocky Mount Spotted Fever is a ______ borne disease

A

Tick-borne

American dog tick
Rocky Mountain wood tick
BROWN DOG TICK** - common species for spread in AZ

30
Q

When does RMSF most frequently occur?

A

April to October, with peak in June and July

Varies based on vector species and climate

31
Q

First symptoms of RMSF begin _____ days after tick bite

A

2-14 days

Bite is usually painless, organism invades endothelial cells that line blood vessels

32
Q

Early symptoms of RMSF are…

A

Non-specific:

Fever
HA
N/V
Abdominal/muscle pain
Lack of appetite
Conjunctival infection
33
Q

What does the RMSF rash look like?

A

Two types:

1) small, flat pink non itchy spots on wrists, forearms, and ankles —> spreads to trunk, palms, and soles
If present, 2-5 days post infection

2) RED to purple spotted petechial rash with pinpoint hemorrhages in up to 60%, usually after 6 days post infection

34
Q

The 2nd type of RMSF rash is a sign of

A

Late infection and severe disease

Every attempt should be made to begin treatment before petechiae develop

35
Q

Diagnosis of RMSF is based on…

A

Clinical signs and symptoms and patient history

Do NOT delay treatment while waiting for lab confirmation, as most successful if treatment is initiated within 5 days

Gold standard is indirect immunofluorescence with a R. rickettsii antigen but organism is difficult to detect until the disease is in late stages

36
Q

Treatment for RMSF

A

Doxycycline

If pregnant, chloramphenicol (but watch out for aplastic anemia)

Microbiology Unit 3 (10 decks)

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