Ectoparasites 1 (Dr Smith) ATM and Intro

Question 1

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

Answer 1

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

Question 2

What ectoparasites come under the Anthropoda phylum?

Answer 2

Ticks, mites, fleas and lice

Question 3

What Class are ticks and mites?

Answer 3

Arachnida

Question 4

What Class are fleas and lice?

Answer 4

Insecta

Question 5

What are fleas and lice?

Answer 5

Insecta

6 legs, wingless

Question 6

What are ticks and mites

Answer 6

Arachnida

8 legs, spiders/scorpions

Question 7

What do Insecta and Arachnida have in common?

Answer 7

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

Question 8

What is the lifecycle of a tick?

Answer 8

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

Question 9

What is the latin name for Ticks?

Answer 9

Ixodes ricinus

Question 10

What is questing in ticks?

Answer 10

‘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)

Question 11

What are the signs associated with tick infestation?

Answer 11

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

Question 12

How are ticks treated?

Answer 12

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

Question 13

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

Answer 13

Tick-borne encephalitis

Lymes disease

Question 14

What is Tick-Borne Encephalitis?

Answer 14

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

Question 15

What is Lymes Disease?

Answer 15

Bacterial disease carried by tick

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

Question 16

What are the symptoms of Lymes Disease?

Answer 16

Bulls eye rash
Flu like symptoms
Tired and general malaise

Incubation 2-100 days

Question 17

What two types of mites are there?

Answer 17

Bed mites and scabies

Question 18

What are the signs and symptoms of bed mites?

Answer 18

Itchy bites

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

Question 19

What is the treatment for bed mites?

Answer 19

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

Question 20

What is the latin name for bed bugs?

Answer 20

Cimex lectularis

Question 21

What is the latin name for scabies?

Answer 21

Sarcoptes scabiei

Question 22

What are the signs and symptoms of scabies?

Answer 22

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

Question 23

What causes pruritus in scabies infestation?

Answer 23

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

Question 24

What is SMIPP? What is the consequence of it?

Answer 24

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

Question 25

How are scabies contagious / transmitted?

Answer 25

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

Question 26

Who are most at risk from scabies infection?

Answer 26

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

Question 27

How long are people infected with scabies?

Answer 27

Indefinite life cycles within host

Question 28

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

Answer 28

Family and partner(s)

Question 29

How can scabies be treated?

Answer 29

``` Insecticides; acaricides Permethrin cream Malathion lotion Ivermectin Benzyl benzoate ```

Question 30

What is the 1st line treatment of scabies?

Answer 30

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

Question 31

What class of drug is Permethrin?

Answer 31

``` 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 ```

Question 32

How does Permethrin act as a neurological toxin?

Answer 32

Binds to Na+ channels in animals and prolongs Na+ activation | This paralyses animal function and leads to death

Question 33

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

Answer 33

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)

Question 34

How are mutations notated in resistance diagrams for pyrethoids?

Answer 34

M918V | Methionine has mutated to V-something at the position 918

Question 35

When is Permethrin 5% cream (Lyclear) contraindicated?

Answer 35

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

Question 36

What are the counselling points for Permethrin 5% cream?

Answer 36

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

Question 37

What class of drug is Malathion?

Answer 37

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)

Question 38

Is Malathion toxic to humans?

Answer 38

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

Question 39

Where does ACh act on muscarinic receptors? | What associated side effects can be expected in Malaoxon poisoning?

Answer 39

Sweat glands, salivary glands and adrenal medulla ``` Side Effects: Miosis Salivation Sweating Bradychardia ```

Question 40

Where does ACh act on nicotinic receptors? | What associated side effects can be expected in Malaoxon poisoning?

Answer 40

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

Question 41

Ach also works on central nervous system by releasing NA. | What associated side effects can be expected in Malaoxon poisoning?

Answer 41

Anxiety, restlessness and dizziness

Question 42

What class of drug is Ivermectin?

Answer 42

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

Question 43

How does Ivermectin work?

Answer 43

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.

Question 44

What are the counseling points of Ivermectin?

Answer 44

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.

Question 45

What are the potential complications of scabies?

Answer 45

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.

Question 46

How can scabies be prevented?

Answer 46

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