Ectoparasites Flashcards
Ectoparasites live where?
On the skin
Distinctive features of ectoparasites
Exoskeleton
Articulated/bent legs
Body’s general response to infection
Allergic dermatitis
Bite patterns
Allergic dermatitis in ectoparasitic infections
When organism bites, the creature gets into the subctuaneous tissue
Saliva is exposed to dendritic cells which survey inside the skin
Result: Red, raised, itchy papules at biting site
Bite patterns - ectoparasitic infections
Can identify some ectoparasites by where/how they bite:
Linear pattern/straight parallel lines - flea bites
Scabies burrows into finger webs
Ticks - two types
Hard ticks - Ixodes scapularis (causes Lyme disease)
Larvae - nymph - adult
Soft ticks - Ornithodoros turicata
Tick borne diseases
Lyme disease Rocky Mountain Spotted fever - Rickettsiae Ehrlichia Anaplasma Babesia
Hard tick - stages of growth and num of legs
Larvae - nymph - Adult
8 legs
Pathogenic host preference for Ticks
Humans/animals
Lice - three types
Head louse - Pediculus capitis
Body louse - Pediculus humanus
(looks the same but prefers body; lives in clothing)
Pubic “Crab” louse - Pthirius pubis (STD)
Lice borne diseases
(Body louse)
Epidemic typhus (Rickettsia prowazekii)
Trench fever (Bartonella quintana)
LBRF - Louse Borne Relapsing Fever caused by bacteria -> (Borrelia recurrentis)
Lice - number of legs and host preference
Six legs
Humans
Mites - one type
Sacroptes scabei
Mite host preference and num of legs
Anthropophilic
8 legs
Anthropophilic
Preferring animal host to humans
Mites typically dont spread disease to humans but if it bites a human then diseases can occur (T/F)
True
Diseases spread by mites
human = accidental host
- Rickettsialpox (Rickettsia akari)
- Scrub Typhus (Orienta tsutsugamushi)
Mites are easy to spot on a person (T/F)
False, mites are almost microscopic, difficult to see with naked eye
Fleas - 4 types
Human flea - Pulex irritans
Rat flea - Xenopsylla cheopis
Cat flea - Ctenocephalides felis
Dog flea - Ctenocephalidies canis
Fleas can jump thousand times their body size (T/F)
True
Fleas - number of legs
6 legs
Flea borne infections
Rat flea causes the foll:
- -Bubonic plague (caused by Yersinia pestis)
- Tularemia (caused by Francisella tularensis)
- Murine “endemic” typhus (R. typhi)
Mosquito - 3 types
-Culex (brown mosquito)
Aedes (aegypti and albopictus)
Anopheles
Distinguishable features of Anopheles compared to other mosquitoes
No humped back
Mosquito borne infections
Culex
Filariasis and West Nile
Aedes (aegypti and albopictus)
Yellow fever, Dengue fever, Chikungunya fever
Anopheles
Malaria
Possible diagnosis methods - ectoparasites
- Can identify nymph
- Gently scrape skin to find eggs/nymphs
- May see egg shell casing/nit left behind e.g. lice
- Bite patterns e.g. linear
Treatment - ectoparasites already left person
If parasites have already left person then we treat symptoms of scratching to prevent skin infection
- Antiinflammatories, antihistamines
- Assess for vector borne epidemics
Treatment - ectoparasites residing inside person
If infested:
-Remove tick gradually to get whole head out intact
-Lice/Mites -> topical/oral agents
Topical agents
Pyrehtroids
Organophosphates
Benzyl alcohol
Spinosad
Lindane
Ivermectin
Oral agent
Ivermectin (poison them via the food source i.e. blood)
-> then treat itchy skin symptoms
