Ectoparasites 2 (Dr Smith) IFL Flashcards
What is the latin name for human flea?
Pulex irritans
What is the general profile of a flea?
Blood sucking, can fly, often host specific re infestation (a cat flea may bite you but cannot infect you).
Actively seek host (CO2 or hormone taxis)
Can survive prolonged starvation.
Are there nymph forms of fleas?
No
What is the life cycle of a flea like?
Eggs shed by females into environment
Eggs hatch into larvae
Larvae form pupae
Adults hatch from pupae and then can infect host i.e. cat, human etc
What are the signs and symptoms of a flea infestation?
Bites grouped in clusters and are itchy
How can flea bites be treated (symptomatically)?
Cold compress, deter scratching, antihistamine to reduce swelling and itching
What does ‘Fleas as vectors of disease’ mean?
Fleas can carry and transmit diseases such as the Plague and Murine Typhus
What is the name and profile of a sand flea?
Tunga Penetrans
‘Chigoe flea, jigger flea, sand flea’
Does not transmit disease, small size compressed, females burrow into skin
Wear shoes in infected areas.
What is the life cycle of Tungiasis?
Eggs shed by female into the environment
Eggs hatch into larvae that develop into pupae
Adults hatch from pupae
Adult females burrow into the stratum granulosum
Gravid females reside in subcutaneous lesion
No treatment; self limiting or suffocation
What is the latin name for lice?
Pediculus humanus
Infestation is known as pediculosis
What is the general profile of lice?
Cling to hair shafts, do not fly or jump but crawl
Can travel up to 25cm per minute
Highly contagious
Persistent for over a year if untreated
What are the three types of lice?
Head lice (pediculus humanus capitis) Body lice (pediculus humanus humanus) Public lice / Crabs (phthirus pubis)
What is the life cycle of lice?
Eggs -> 3 nymphs -> Adults
Hop on, lay eggs, life cycle on host, repeat.
What are the signs and symptoms of head lice?
Itching, difficulty sleeping, scratching, (secondary infection), often raised bumps on neck.
Diagnosis upon visual inspection (scalp and comb).
What are the pharmaceutical treatments for head lice?
8-12 hours contact time
Dimeticone lotion 4% (Conotrane) - does not kill live eggs
Benzyl alcohol emulsion 25% - does not kill live eggs
Malathion Lotion 0.5% (Derbac-M) - kills live lice and partially ovicidal
Lindane Shampoo 1% - antiquated, can cause neurological damage / death (banned in UK and from the EU in 2008).
How does Dimeticone work?
Silicone based, forms water impervious coat of silicone on the lice and suffocates them
How does Malathion work?
Organophosphorous anticholinesterase; promotes cholinergic neurotransmission and is a neurotoxic insecticide.
No more than 4 consecutive applications
Can be irritating to skin/scalp
How does Lindane work?
Gamma-hexachlorocyclohexane
An ion channel agonist
Neurological toxin that binds to an inhibits GABAa chloride channel complex
But GABAa found in animals so cab interfere with mammalian central neurotransmission
GABAa is antiepileptic, dampens /inhibits neuronal activity
Lindane can cause seizures and convulsions
How can you prevent/remove head lice?
Wet comb
Pyrethoids used in children better than shampoo and comb
Malathion and lindane - neurotoxin
What is the difference in the lice infesting head vs pubic hair?
Body louse claws are adapted for round hair common on head
Pubic louse claws are adapted for oval shaped hair common with pubic hair and eye lashes
What are the signs and symptoms of pubic lice?
Itching in affected area, inflammation caused by scratching
Black powder in underwear
Blue-coloured spots on skin
Tiny blood spots on skin or underwear
Pubic hair but also body hair (armpits, chest, leg, facial hair, beards/eyebrows)
Diagnosis via visual detection of lice
How are crabs spread?
Mainly through sexual contact; most contagious STD
Condoms do not protect
Non sexual spread by contact with clothing, linen and towels less common but possible
How are pubic lice treated?
Insecticides applies initially once to whole body:
Permethrin (Lyclear)
Malathion (Derbac-M)
Applied for 12 hours
Repeat after 7 days to kill newly hatched lice
Treat household members and sexual partners
(Not dimeticone)
What are the signs and symptoms of body lice?
Pruritus Skin discolouration/thickening Secondary bacterial infection Red rash Diagnosis - visual detection of lice
What is the treatment for body lice?
Laundering to prevent reinfestation
Insecticides applied initially once;
Permethrin
Malathion
Applied for 12 hours
Reapply after 7 days to kill newly hatched lice
Treat household members or sexual partners
Body lice can transmit bacterial diseases; where is this particularly likely?
Refugee camps, overcrowded prisons and in cramped living conditions
What is Borrelia recurrentis?
Louse-Borne Relapsing Fever
Recurring episodes of fever 5-15 days after louse infestation; headache, muscle and joint aches and nausea
Sweating sickness
What is Bartonella quintana?
Trench Fever
Less serious LBF with bone pain
Characteristic 5 day relapsing fever that is rarely fatal and can be treated with antibiotics.
What are the three bacterial diseases that can be transmitted by body lice?
Louse-borne relapsing fever
Trench fever
Epidemic typhus
What is Rickettsia prowazekii?
Epidemic typhus Jail fever / Camp fever / Famine fever Severe symptoms; headache, cough, fever, muscle pains, chills, hypotension, stupor, photosensitivity, delirium. Fumigation needed Vaccine?
