INF2 - F. ECTOPARASITES-COVERED Flashcards
what are ectoparasites
- ticks and lice
- they live externally ie - on skin
symptoms of ticks and lice
- itching
- scratching
- bites
- soreness (secondary infection?)
- infestation NOT infection but
- parasites are hosts for transmitted pathogens and disease
what phylum are ticks, mites, fleas and lice
phylum arthropoda
what class are fleas and lice
class insecta
what class are ticks and mites
class arachnida
what do ticks, mites, fleas and lice do
- blood sucking parasites to gain their energy
- live on skin
- host specific - human
where are ticks mostly distributed
- woodland
- deers are the most endemic natural host for ticks
ticks
- adults, larvae, nymphs climb tall grass and shrubs
- they quest and wait for something warm blooded to pass
- attach to host
signs of ticks
- move up body
- warm sweaty places
- exposed limbs (top of legs, top of arms, buttocks) and neck
- no itching
- visual examination is only way to see
treatment of ticks
- no pharmacological treatment
- physical removal
tweezers or tick card (grab neck and twist out)
don’t squeeze or crush body as it will vomit in bloodstream
don’t leave head behind
don’t burn off or use other noxious mean
keep tick for +ve identification
ok if removed within 24 hrs of attachment
consequences of tick bite
- UK and Europe: Lyme disease, Tick-borne encephalitis
Lyme disease
- bacterial disease carried by tick
- spirochetes borrelia burgdorfi
symptoms
- bulls eye rash (Erythema migrans: not hot, itchy or scaly - red ring with a red centre)
- flu-like symptoms
- incubation 2-100 days
- 14% of world population may have had Lyme disease
treatment
- oral antibiotic: doxycycline
prevention
- cover up
- topical insecticide
tick borne encephalitis
-viral disease carried by tick
- flavivirus
- infects brain
symptoms
- fever then mild flu-like then no symptoms ‘recovered’
- then neurological symptoms, high fever
- headache - encephalitis, meningitis - paralyses
- over 3 weeks
- death possible within 7 days of neurological symptoms
- vaccination: FSME-Immun and Encepur
Lice (nits)
- infestation: pediculosis
- cling to hair shafts
- crawl
- travel quickly
- highly contagious
- persistent >1 if untreated
what are the 3 types of lice
- head lice
- body lice
- pubic lice (crabs)
headlice
symptoms
- itching of scalp
- difficulty sleeping
- scratching - secondary bacterial infections on neck?
- raised bumps on neck
- girls at higher risk than boys: long hair, sharing brushes
diagnosis
- visual inspection
- wet comb and paper so lice stick
socioeconomic impact
- school days lost
- workdays lost
notifiable disease
treatment of lice
- P medicines
- 8-12 hours contact time
Dimeticone lotion 4%
- doesn’t kill live eggs just kills parental organism (adult) so need to reapply to wait for eggs to hatch
Benzyl alcohol emulsion 25%
- doesn’t kill live eggs
Malathion lotion 0.5%
- kills adult and partially kills eggs
Lindane shampoo 1%
- outdated
- can cause neurological damage/death
- no used in UK
how does dimeticone work
- silicone based (like oil)
- forms water impervious coat if silicone on lice
- suffocated lice
how does benzyl alcohol work
- suffocation
how does malathion work
- organophosphorous anticholinesterase
- neurological toxin as:
acts on nervous system of animal
irreversibly bind to and blocks cholinesterase so stops synaptic activity
promotes cholinergic neurotransmission (ACh used as NT)
post-ganglionic neuronal excitation
continues muscle excitation and contraction and dies
contraindications of malathion
- low toxicity to man
- only with repeated exposure and overdose will be toxic as will be absorbed through scalp and can be irritating
- ingestion and metabolism to toxic malaoxon therefore
- oxidation to malaoxon also occurs by chlorination of water
- therefore don’t eat or drink
- no more than 4 consecutive applications
- anti cholinesterase activates parasympathetic nervous system
- promotes muscarinic transmission
- neuromuscular, promotes nicotinic transmission at
skeletal muscle - CNS, promotes cholinergic neurotransmission
effects of malathion/malaoxon poisoning
muscarinic (parasympathetic) effects:
- miosis (pupillary constriction)
- salivation
- sweating
- bradycardia
- increased bowel movements
- urinary incontinence
nicotinic (SkM) effects:
- fasciculation (twitching) due to spontaneous release of ACh
- paralysis due too depolarising neuromuscular block
CNS effects:
- anxiety
- restlessness
- dizziness
ALL DUE TO HEIGHTENED ACH ACTION
how does lindane work
- gamma-hexachlorocyclohexane
- ion channel antagonist
- neurological toxin
- binds to and inhibits GABAa chloride channel complex
- acts at picrotoxin site
- delta subunit
brain releases GABA reduce excitability of brain
if blocked becomes more excited and may go into epileptic episodes
BUT
- GABAa is ubiquitous in Animalia
- so interferes with mammalian central neurotransmission
- GABAa antileptic, dampens neuronal activity
- so can cause seizures and convulsions
- definite no
prophylaxis for lice
- wet comb and shampoo/hair conditioner
- insecticide (pyrethroids)
- tee oil (alternative to conditioner)
symptoms of public lice
- pubic, armpit, chest, leg, facial hair
- itching
- inflammation from scratching - secondary infection?
- black powder in underwear (discarded bodies of dead lice)
- tiny blood spots on underwear (crushed dead lice)
diagnosis
- visual detection
how is crabs spread
- sexual contact
- condoms don’t protect
- non-sexual via fomites
- children: indicator of sexual abuse
symptoms of body lice
- pruritis
- skin discolouration/thickening
- secondary bacterial infection
- red rash
diagnosis
- visual detection
treatment of body and public lice
- insecticides applied initially once to whole body
- Permethrin - iron channel agonist
- Malathion
- applied for 12 hours
- ineffective ovicides so repeat after 7 days to kill newly hatched lice to prevent reinfestation
- to prevent re infestation: hot wash
what bacterial diseases can body lice transmit
- louse-borne relapsing fever (yellow fever)
- trench fever
- bubonic plague
