Beaudry - Infestations and Bites Flashcards
A 7 yo CF (pictured below) presents to your office with an intensely pruritic scalp for 2 weeks, and the recent onset of an eruption on the nape of the neck and post-auricular scalp. She is otherwise healthy, but mom is convinced she has psoriasis (just like her). What is the most likely diagnosis?
Head lice
What is the pathogenesis of pediculosis capitis (head lice)?
- Head louse is an obligate human parasite, and requires blood every 4-6 hours
- Transmitted via direct contact or fomites (i.e., a comb)
What are the clinical manifestations of pediculosis capitis (head lice)?
- Itchy scalp
- Excoriated dermatitis behind ears, nape of neck
- Nits in hair (rarely see actual louse) –> close to scalp (see attached image)
1. Cemented to hair shaft and immobile; head louse lays eggs near the scalp, and distance the nits are from the scalp is indicative of how long pt has been infested with the head louse - Incubation period: 2 - 6 weeks on first exposure (24 - 48 hours upon re-exposure)
What is the treatment for pediculosis capitis (head lice)?
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2 applications 1-2 weeks apart:
1. OTC Pyrethrin, Permetrhin
2. Malathion, Ivermectin (px) for resistant cases - Need to tx any symptomatic contacts and anyone who shares bed with patient (even if asymptomatic)
- 30-day life cycle, and can survive about 36 hours w/o a blood meal from a human (eggs can survive for 10 days off the host) –> this is why these pt’s need a treatment 1-2 weeks after the first treatment
What is going on here?
- Pediuclosis capitis is a very pruritic infestation
- Scratching can lead to secondary staph infections
What are the causative agent, pathogenesis, clinical manifestations, and treatment for crab lice?
- Causative agent: Pthirus pubis
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Pathogenesis: like head lice, adults lay eggs in nits attached to body hairs close to the skin
1. Serrated first claws: grab onto skin and move to any o/body site (people frequently infected at 2+ places)
2. Transmitted via sexual contact and fomites -
Clinical Manifestations: pruritus in the pubic region
1. Can also have infection of eyelashes, scalp, axilla, beard, perianal regions
2. Macula caerulea: blue/gray patches on trunk/proximal extremities; thought to be due to breakdown of bilirubin to biliverdin by saliva
3. Pt’s frequently have infestation of pubic area and another hair bearing site (eyelids common) -
Treatment: need 2 treatments, 1 week apart
1. Permethrin 1% cream
2. Ivermectin
3. Treat sexual partnersl treat all hairly areas
What are the causative agent, pathogenesis, clinical manifestations, and treatment for body lice?
- Causative agent: Pediculus humanus var. corporis
- Pathogenesis: nits, lice live in seams of clothing; feed on humans intermittently, but don’t live on ‘em
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Transmit infections: bacteria in feces of louse get scratched into skin
1. Epidemic typhus – Rickettsia prowasekii
2. Relapsing fever – Borrelia recurrentis
3. Trench fever, bacillary angiomatosis, endocarditis – Bartonella quintana -
Clinical Manifestations: severe pruritus and dermatitis + excoriations diffusely
1. See lice/nites in seams of clothing -
Treatment: burn clothing/bedding
1. Otherwise, wash in hot water and iron; hot iron seams of furtniture; avoid furniture 2 wks
2. Dusting powders for widespread infestation
A 19 yo college student travels to South America for spring break. When he returns, he notices a painful nodule on his posterior neck, which has been enlarging over the past 2 weeks, and swears he feels something moving in there. He is otherwise healthy. A surgeon removes this from his back. What is your diagnosis?
- Myiasis: larvae (maggots) from flies
- Causative agent(s): Dermatobia hominis (botfly) and Cordylobia anthropophaga (tumba fly)
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Pathogenesis:
1. Botfly lays eggs on mosquito – human – soil
2. Tumba fly lays eggs on wet clothes/sand –human –soil - Clinical: furuncle (boil) with central pore, and can also infest wounds
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Treatment: surgical debridement
1. Occlusion (petrolatum, bacon, etc)
2. Intralesional lidocaine
A 3mo male comes to your office with a diffusely pruritic eruption of 2 weeks duration. Mother states he is not getting any sleep because he is scratching “all night long”. His pediatrician has given him treatment for atopic dermatitis, but it is not helping. Mother states she recently has also become itchy recently, as has her 4 yo daughter. The little boy is scratching during the visit. What in-office procedure should you do next?
Mineral oil prep (see attached)
What are the causative agent, pathogenesis, and clinical manifestations of scabies?
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Causative Agent: Sarcoptes scabiei var hominis
1. Transmitted via close personal contact and fomites -
Pathogenesis: obligate human parasite; entire 30 day cycle completed in epidermis
1. 10-15 on skin (thousands in crusted scabies)
2. Incubation period: 2-6 wks on first exposure (24-48 hrs on re-exposure) -
Clinical Manifestations: intense pruritus
1. Burrows: tunnel where female lays her eggs
2. Excoriated dermatitis and vesicles/pustules
3. Classic areas: webs of fingers, groin, flexor wrists, axilla, areolae (spares face/scalp)
4. Infants and immunocompromised – diffuse (involves scalp/face)
5. Crusted scabies: in immunocompromised and elderly; thick scaling on hands, face/scalp
What is the treatment for scabies?
- 2 applications, 1 week apart, and all household members/close contacts MUST be treated
1. Permethrin 5% cream: apply from neck down, sleep, wash off in morning
2. Lindaine: resistance increasing; CNS toxicity (use with caution in children)
3. Sulfur ointment: safe for young children and pregnant women
4. Ivermectin -
Counseling: wash all bedding, clothing in hot H2O
1. Apply cream and sleep; in the AM, wash off cream, wash all bedding and PJ’s in hot water; repeat process in 1 week
2. Tie off any pillows in a black plastic bag - do not use for 10 days
3. Post-scabetic pruritus: can last 2-4 wks after successful tx (body’s response to dead mites)
What is this?
- Crusted scabies: in immunocompromised and elderly; thick scaling on hands, face/scalp
A 49 yo female presents to your office with “itchy red bumps”, predominantly on her legs and arms. She moved into a new apartment about 4 weeks ago and is wondering if her new place has “bugs”. On physical exam you see the below picture. What is your diagnosis?
- BED BUGS
- Causative agent: Cimex lectularius or hemipterus
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Pathogenesis: blood sucking ectoparasite
1. Hide in walls during the day, feed at night
2. Bites are due to our immune response to salivary antigens
3. Vector for Hep B, Chagas disease - Clinical Manifestations: “Breakfast, Lunch, Dinner”
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Treatment: exterminator
1. Topical steroids, anti-histamines
What is this?
- BED BUG
- Flat, oval body
- Segmental abdomen
- 6 legs
- Vestigial wings
This child is taken to the doctor for eyelid swelling. The doctor tells the mother his appearance is due to an infestation with a protozoa. He prescibes the child a medication and states, “I am so glad you brought him so early so we can try to avoid heart failure and GI dysmotility in the future!”. What is your diagnosis?
Trypanosomiasis
Romana sign: unilateral eyelid edema (due to bite of conjunctiva/periocular skin)
What is this?
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Reduvid (kissing) bug: vector for American trypanosomiasis (Chagas disease)
1. Tend to bite face (hence name kissing bug)
2. Tiger-striped abdomen - Trypanosomes infect ANS (megacolon, cardiomegaly, etc)
- Romana sign: unilateral eyelid edema (due to bite of conjunctiva/periocular skin)
What are the causative agents, and clinical manifestations of this?
- Causative agent(s): Genocephalides felis, Pulex irritans
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Clinical Manifestations: intensely pruritic papules and vesicles on lower extremities (fleas do not have wings – jump! – look how long their back legs are)
1. Vectors for:
a. Endemic typhus
b. Flea-borne spotted fever
c. Plaque
d. Cat scratch fever (in cats)
A very sick 9 yo female presents to the ED with a 2 day history of fevers and headaches. Mom brought her to the emergency room when she developed a rash on her hands and feet. What tickborne disease should be on your differential?
Rocky mountain spotted fever
What is this? What does it transmit?
- Amblyoma: lone star
- Transmits:
1. Ehrlichiosis (Ehrlichia chaffeensis): bacterial flu-like illness (mild body aches to severe fever)
2. Southern Tick-Associated Rash Illness (STARI) -> looks like lyme disease, but is in southern states (unknown vector)
3. RMSF (not the main vector)
4. Tularemia: severe infectious zoonotic bac disease -> ulcers at site of infection, fever, and loss of weight
What is this? What does it transmit?
- Dermacentor: American dog tick
- Transmits:
1. RMSF – D. variabilis; NC/SE USA
2. Tick paralysis – tick attached to skin, leads to ascending paralysis; removal of tick leads to immediate improvement
3. Tularemia: severe infectious zoonotic bac disease -> ulcers at site of infection, fever, and loss of weight
4. Q fever (Coxiella burnetii): zoonotic bac infection w/flu-like symptoms that can progress to pneumonia
What is this? What does it transmit?
- Ixodes: deer tick
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Transmits:
1. Lyme disease: erythema migrans (see attached image)
a. I. scapularis (Eastern US)
b. I. pacificus (Western US)
c. I. ricinus/I. persulcatus (Europe)
2. Babesiosis: malaria-like parasitic disease
3. Human anaplasmosis: fever, headache, chills, and muscle aches
What is this? Causative agents, clinical manifestations, and treatment?
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Causative agents: red hourglass on back
1. Lactrodectus mactans – black widow
2. Lactrodectus geometricus – brown widow -
Pathophysiology: contain neurotoxins – latrotoxins
1. PainFUL bite
2. Systemic symptoms – muscle spasms, abdominal pain, sweating, nausea - Treatment: Benzo’s, IV Calcium gluconate
What is this? Causative agents, clinical manifestations, and treatment?
- Causative agent: Loxoscles reclusa -> brown fiddle on its back
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Pathogenesis: non-aggressive
1. Venom has sphingomylin D, hyaluronidase
2. Bite is NOT painful -
Clinical: ulceronecrotic skin lesions at site of bite
1. Can get DIC, hemolytic anemia
What is this?
- Funnel web spider
- Causative agent: Hobo spider (Tegenaria agrestis), several
- Aggressive spiders
- Found in basements, wet dark spaces
- Toxin affects CNS; causes local necrosis at bite site
What is this?
- Tarantula
- Non-aggressive spiders
- Have urticating hairs
1. Ophthalmia nodosa: cutaneous condition characterized by inflammation of the eye
