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B33VPI > Ectoparasites 1 (Dr Smith) ATM and Intro > Flashcards

Ectoparasites 1 (Dr Smith) ATM and Intro Flashcards

1
Q

What are the generic signs and symptoms of an ectoparasite infestation?

A 
Itching, scratching, bites, soreness
Generally not life threatening
Infestation not infection 
Mild to servere discomfort, secondary itching from scratching
Social stigma
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2
Q

What ectoparasites come under the Anthropoda phylum?

A

Ticks, mites, fleas and lice

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3
Q

What Class are ticks and mites?

A

Arachnida

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4
Q

What Class are fleas and lice?

A

Insecta

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5
Q

What are fleas and lice?

A

Insecta

6 legs, wingless

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6
Q

What are ticks and mites

A

Arachnida

8 legs, spiders/scorpions

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7
Q

What do Insecta and Arachnida have in common?

A

All blood-sucking parasites
Ectoparasites (live on skin)
Tend to be host specific

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8
Q

What is the lifecycle of a tick?

A

Three hosts

  1. Adults females drop off host to lay eggs
  2. Eggs hatch into 6 legged larvae
  3. Larvae attach to and feed on the first host (squirrel)
  4. Larvae detach from the host and molt into nymphs
  5. Nymphs attach to secondary host (rabbit)
  6. Nymphs molt into adults after leaving second host
  7. Adults attach to the third host in the spring for feeding and mating
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9
Q

What is the latin name for Ticks?

A

Ixodes ricinus

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10
Q

What is questing in ticks?

A

‘Questing’ is when ticks climb tall grass / shrubs and attach to a passing host, playing in long grass or hiking
Inspect skin at the end of the day (check especially in warm sweaty places)

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11
Q

What are the signs associated with tick infestation?

A 
Move up body
Exposed limbs (tops of legs and arms)
Neck
Do not itch
Visual examination only way to detect
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12
Q

How are ticks treated?

A

No pharmacological treatment
Physical removal; use tweezers, do not squeeze or crush body, do not leave head behind
Do not try to burn off or other noxious means
Keep tick for positive identification

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13
Q

What are the two possible consequences of ticks (if undetected or incorrectly removed?)

A

Tick-borne encephalitis

Lymes disease

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14
Q

What is Tick-Borne Encephalitis?

A

A viral disease caused by ticks
-Flavivirus
-Infect the brain
Symptoms –> seek immediate medical help

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15
Q

What is Lymes Disease?

A

Bacterial disease carried by tick

-Spirochetes can be released if the head or body is crushed/left undetected

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16
Q

What are the symptoms of Lymes Disease?

A

Bulls eye rash
Flu like symptoms
Tired and general malaise

Incubation 2-100 days

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17
Q

What two types of mites are there?

A

Bed mites and scabies

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18
Q

What are the signs and symptoms of bed mites?

A

Itchy bites

  • allergic reaction
  • bites in straight lines; not random like in mosquitoes or flies
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19
Q

What is the treatment for bed mites?

A

Minimal; symptomatic treatment
-empirical treatment for bite reactions such as antibiotics, antihistamine, topical or oral corticosteroids
Prevention; general hygiene, hot washes 60 and airing bed clothes

20
Q

What is the latin name for bed bugs?

A

Cimex lectularis

21
Q

What is the latin name for scabies?

A

Sarcoptes scabiei

22
Q

What are the signs and symptoms of scabies?

A

Epidermal skin infestation
Feed in tissue and fluids
Characterised by superficial burrows and pruritis (intense itching)
Like skin folds; fingers, buttock and breast creases
Visual signs: Ensure not impetigo or eczema; burrow marks and ink tests
Skin biopsy - scabies mites

23
Q

What causes pruritus in scabies infestation?

A

IV-sensitivity reaction to mite, saliva, eggs or excrement

24
Q

What is SMIPP? What is the consequence of it?

A

Scabies Mite Inactivated Protease Paralogue
Protein with no enzyme activity
Antagonist to PAR-2 on keratinocyte
Inhibit inflammatory response: aid infection by the mite

25
Q

How are scabies contagious / transmitted?

A

Scratching, picking up the mites under fingernails or touching infected persons skin
Fomites; keyboards, toilets, clothing, towels, bedding, furniture
Survive for up to 14 days away from host
Symptoms develop after 3-4 weeks

26
Q

Who are most at risk from scabies infection?

A

Elderly people, children, young mothers from infested children, sexually active people (STI)

27
Q

How long are people infected with scabies?

A

Indefinite life cycles within host

28
Q

Who else needs Tx once a person is found to have scabies?

A

Family and partner(s)

29
Q

How can scabies be treated?

A 
Insecticides; acaricides
Permethrin cream
Malathion lotion
Ivermectin 
Benzyl benzoate
30
Q

What is the 1st line treatment of scabies?

A

1st line is Permethrin cream 5% (Lyclear)
More effective than topical crotamiton 10% or oral ivermectin

2nd line is Malathion Lotion 0.5%

Itching treated with crotamiton (Eurax) and sedating antihistamine

31
Q

What class of drug is Permethrin?

A 
A synthetic pyrethoid 
Similar to the natural pyrethrins from Chrysanthenum 
An ion channel agonist
Acts on nervous system of animals 
It is a neurological toxin
32
Q

How does Permethrin act as a neurological toxin?

A

Binds to Na+ channels in animals and prolongs Na+ activation

This paralyses animal function and leads to death

33
Q

How does Permethrin not cause neurological toxicity to human cell Na+ channels?

A

Arachnida have a different activation gate to human channels
Insects are more susceptible because of the sequence of domain II S4-S5 linker at the kdr sire (M918)

34
Q

How are mutations notated in resistance diagrams for pyrethoids?

A

M918V

Methionine has mutated to V-something at the position 918

35
Q

When is Permethrin 5% cream (Lyclear) contraindicated?

A

Absorption of topical cream is minimal; so there is no risk for breastfeeding but cream shouldn’t be applied to the nipple.

36
Q

What are the counselling points for Permethrin 5% cream?

A

Itching may persist up to 3 weeks post treatment as animal material and faeces remain under skin
Suspect treatment failure if;
after 6 weeks if itching persists
new burrows appear
Treatment non-compliance - Tx over night; complete coverage and then repeat one week later
Treat personal, close contacts to avoid reinfestation

Drug resistance; if suspected, biopsy needed to genotype animal for drug resistance and then Malathion 0.05% lotion may be needed

37
Q

What class of drug is Malathion?

A

Acetylcholinesterase (an organophosphorous compound)
It is a neurological toxin and binds irreversibly to cholinesterase (so that it cannot metabolise/remove the Ach) and promotes all cholinergic neurotransmission. This leads to post-ganglion excitation that leads to continuous muscle excitation and contraction. (Paralysis)

38
Q

Is Malathion toxic to humans?

A

Low toxicity - only with long exposure/overdose can it cause problems.
Ingestion and metabolism of the lotion to malaoxon is far more toxic; chlorination of water promotes oxidation to malaoxon.
The malaoxon acts as an anti-cholinesterase in man; over excitation of Ach receptors

39
Q

Where does ACh act on muscarinic receptors?

What associated side effects can be expected in Malaoxon poisoning?

A

Sweat glands, salivary glands and adrenal medulla

Side Effects:
Miosis 
Salivation 
Sweating 
Bradychardia
40
Q

Where does ACh act on nicotinic receptors?

What associated side effects can be expected in Malaoxon poisoning?

A

Skeletal muscle (somatic efferent system)
Fasciculation (twitching of SkM)
Paralysis - depolarising neuromuscular block

41
Q

Ach also works on central nervous system by releasing NA.

What associated side effects can be expected in Malaoxon poisoning?

A

Anxiety, restlessness and dizziness

42
Q

What class of drug is Ivermectin?

A

Macrolytic lactone

Derived from Streptomyces bacterium; an example of an ion channel agonist that acts on nervous system of animals

43
Q

How does Ivermectin work?

A

It is a neurological toxin that binds and activates GluCl (glutamate gated chloride channels) by mimicking glutamate.
GluCl channels are a member of the Cys-loop ligan gated ion channel variety and are invertebrate specific. Ivermectin causes persistent opening and parylses animal function.

44
Q

What are the counseling points of Ivermectin?

A

Oral administration
Does not cross the BBB (and no glutamate receptors in the brain anyway so safe for humans), P-glycoprotein efflux
Not given to children <5 y/o, in breastfeeding women or in renal/hepatic diseases.

45
Q

What are the potential complications of scabies?

A

Secondary infection: Stapylococcus or impetigo due to scratching. Treat with antibiotics

Social stigma

Crusted scabies: in extreme infestations (thousands to millions) - does not itch, thick, warty crusts form, immuni deficient patients are more vulnerable. Treat with Ivermectin 200mcg/kg by mouth.

46
Q

How can scabies be prevented?

A

Avoid sharing clothes, bed linen or towels
Dirty hotels and accomodation avoided
General hygiene

B33VPI (16 decks)

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