Vectors of Dermatologic Disease Tory Davis, PA-C

SCABIES  Mite = Sarcoptes scabiei  Pregnant female mite arrives on skin surface and within one hour excavates a burrow in the stratum corneum and lays 2-3 eggs every 24 hours.  Eggs and fecal pellets deposited in burrows leads to hypersensitivity reaction, which ITCHES!

SCABIES  Transmitted by direct contact  Often sexually transmitted  Mite can live up to 3 days on bedclothes- but less likely than direct skin-to-skin transmission  Lesions typically found in finger webs, wrists, hands, axilla, buttocks, ankles, and belt line. Palms and soles of infants.

SCABIES  Symptoms minor and localized at first  Nocturnal pruritis is characteristic  Pruritis may take weeks to develop  Scratching spreads mites  Discrete small papules and vesicles with linear or curved burrows

SCABIES: DX  Take the history –What’s the classic hx?  Apply tip of felt pen to enhance burrow  Apply drop of mineral oil to lesion and shave or scrape it w/#15 scalpel – transfer to slide.

SCABIES: Treatment  Permethrin (Elimite) applied head to soles and leave on 8-14 hours.  Lindane (Kwell) second line, can cause seizures  Ivermectin – single oral dose (200 mcg/kg) if topicals ineffective or not feasible  Wash all bedding, clothes, and towels  Household and intimate contacts need tx

Pt Ed  Stress prevention  Pruritis may persist because the itching is hypersensitivity reaction –May need to rx something for the itch, like an antihistamine (diphenhydramine/ Benadryl) or even a steroid

PEDICULOSIS (lice)  Transmitted by close contact and fomites (hats, pillows)  Adults survive off host 10 days and fertile eggs up to 3 weeks  Lice feed 5 times daily by piercing skin, injecting irritating saliva and sucking blood  3 distinct organisms for head, pubic and body lice

PEDICULOSIS CAPITIS  HEAD LICE –Pediculus humanus capitis  Most common in children  Girls more likely than boys  Rare in African Americans  Most commonly seen on back of head, on the neck, and behind the ears  Grey-white, the size of sesame seeds

PEDICULOSIS CAPITIS  Eyelashes may be involved  Posterior cervical adenopathy is common  Exam shows few adults  Many nits cemented to hair shaft –Nits fluoresce with woods lamp –Nits are difficult to remove (unlike dandruff)

PEDICULOSIS PUBIS  CRABS OR PUBIC LICE –Phthirus pubis  Pubic hair is most common site but can spread to anus  Most common c/o is pruritis  30% of pts have at least 1 other STD

Pediculosis Pubis  Risk factors include: –Being a sexually-active adolescent –Having multiple sexual partners –Having sexual contact with an infected person –Sharing bedding or clothing with an infected person

PEDICULOSIS PUBIS: TX  Lindane (Kwell) or permethrin (Nix) –Shampoo – apply, lather, wash off in 10 minutes. –Repeat tx in 7-10 days –Comb out nits –Treat secondary bacterial skin infection if present (usually from pruritis and excoriation)

Fleas  Laterally flattened, wingless insects  Adults eat blood, larvae eat organic compost (like your dead skin)  Adults can live over a year without feeding, so difficult to eradicate by starvation –Must kill adults, eggs, larvae in the whole environment…including outside

Fleas  Bites occur in clusters of 3 tiny red dots –breakfast, lunch and dinner  Most commonly found around the ankles or lower legs –Usually caused by cat or rat fleas –Complications: secondary infection, hypersensitivity rxn

Flea-Tx  TX: Methoprene in spray or fogger –Used early in the year protect against infestation for up to 4 months –Reside on pets, animal bedding, anywhere in the house  Tx secondary infections, too

Swimmers Itch aka “Duck itch”  Schistosome cercarial dermatitis  Larval parasite hosted by snails and birds  S/S appear hours to days after exposure.  Intense itching with patchy red pin-point rash, may develop inflammatory reaction  TX = symptomatic only  Pt Ed- Remove swimsuit and rinse with fresh water immediately after swimming in a pond near things that quack.

Ticks  Lyme Disease  Rocky Mountain Spotted Fever  And a bunch of others… –Babesiosis –Ehrlichiosis

Lyme Disease  Initial rash, HA, fever  Followed by arthralgias, heart and nervous complications if untreated  Caused by bacteria Borrelia burgdorferi transmitted by Ixodes genus (hard ticks)

ERYTHEMA MIGRANS  Classic skin lesion associated with Lyme Disease  Appears at site of inoculation approx. 9 days after tick bite  Begins as small papule – slowly enlarging ring (up to 50 cm) with central clearing  No scaling at edges like tinea  Minimal pruritis, some tenderness  Fades in 3-4 weeks even w/o tx –That means the RASH is gone, not the disease!)

Rocky Mountain Spotted Fever  Palpable purpuric rash involving palms and soles –Secondary to vasculitis  Associated with fever and headache  Bacterial organism Rickettsia rickettsii transmitted by dog tick

Spider Bites  Most important thing to know:  If they say it’s a spider bite, but never saw the spider, think about MRSA! –Put it on the top of your Ddx –Methicillin Resistant Staph Aureus

Bed Bugs  Reddish brown, flat. 0.5 cm long.  Hide during the day in bedclothes or seams of mattress  Suck blood at night leaving small pink pruritic papules  Will feed on any mammal  Infestations common in shelters, apartments, and increasing in single-family homes

Bed Bug Dx/Tx  Hx may reveal blood stains on sheets and behind wallpaper  Also sweet smell at sites of infestation due to oily secretions  Tx symptomatic, extermination needed –Professional gig, big undertaking