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Parasitology > Mites > Flashcards

Mites Flashcards

1
Q

What ticks belong to the family sarcoptidae?

A

Sarcoptes scabiei and Knemidocoptes spp.

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2
Q

How is Sarcoptes scabiei identified?

A

Short legs, dorsal pegs and spines.

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3
Q

Describe its life cycle.

A

Female tunnels into upper epidermis and lays eggs in an egg laying pocket. These hatch and larvae crawl to the surface. They then burrow into the epidermis forming moulting pockets. Nymphs mould twice before being mature. Males then migrate to the surface to look for females. This is all completed within about 3 weeks.

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4
Q

How is sarcoptic mange transmitted?

A

Through direct contact, usually males/larvae.

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5
Q

What are the clinical signs of sarcoptic mange?

A

Erythema with papule formation
scale, crust & alopecia
Intense pruritus
Wrinkling and thickening of the skin

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6
Q

In which animals is this most common in?

A

The dog, pigs and cattle. It is notifiable in sheep and horses. Rare in cats. In humans it is most likely to occur on contact points from handling infected animals.

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7
Q

How is it diagnosed?

A

Skin scraping, 10% KOH and then warm over a bunsen to “clear” the specimen.

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8
Q

How are Knemidocoptes spp. normally identified?

A

Very short legs and a U shaped chitinous bar behind the head.

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9
Q

What are the spp. of Knemidocoptes and what are the common names given to the conditions they cause?

A

K. mutans - scaly leg
K. gallinae - depluming itch
K. pilae - scaly beak

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10
Q

What shape is demodex?

A

Cigar shaped

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11
Q

What animals do Demodex spp. infect?

A

All domestic animals and humans, each have their own species of Demodex.

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12
Q

What is the normal habitat of Demodex spp.?

A

As a commensal organism in the hair follicles and sebaceous glands.

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13
Q

What are the consequences of a pathogenic demodex infection?

A

a) squamous demodecosis - dry reaction with alopecia, desquamation and skin thickening. Less severe
b) Pustular (or follicular) demodecosis - skin becomes infected with Staphylococci. Pustulus ooze serum, blood and pus.

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14
Q

What factors predispose to demodecosis?

A

Immune deficiency

a) Familial susceptibility
b) Immunosuppresion (can be caused by Demodex)
c) Immunosuppresants (many drugs used to treat skin problems are immunosuppresants!)

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15
Q

How can commensal and infection be distinguished?

A 
Commensal = probably only see a few adult mites
Infection = many more mites and larval stages present.
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16
Q

How can Psoroptes spp. be distinguished from Chorioptes spp.?

A

Psoroptes spp. have segmented pedicels at the end of their legs.

17
Q

What do Psoroptes spp. feed on?

A

A serous exudate that comes from skin that they abrade.

18
Q

What is the common term for Psoroptic mange, when is it most prevalent and what is the reason for its seasonal variability?

A

Sheep scab. It is most prevalent in autumn/winter and can occur late in the summer. This is due to when the sheep are shorn which changes the microclimate of the sheep’s skin.

19
Q

What clinical signs are associated with this mite?

A

Hypersensitivity reactions to their faeces. A yellow crusty scale from the serous exudate. Also self inflicted trauma and reduced productivity.

20
Q

How should sheep be treated?

A

Prophylactically - plunge dipped for at least 1 minute and immerse the head at least once. Avermectins can be used as a treatment.

21
Q

Why are Chiroptes spp. less pathogenic than Psoroptes?

A

They do not abrade the skin, just feed on surface scales and debris.

22
Q

What is the disease that is commonly caused by Otodectes mites?

A

Otitis externa

23
Q

How is it usually identified?

A

By its location in the ear and on the skin surface. It also has chitinous bars (closed apodemes) on its ventral surface.

24
Q

What is important to note in the control of Otodectes in the home environment?

A

Cats can be asymptomatic carriers so it is important to treat these at home + other in contact animals if a dog is seen in the clinic.

25
Q

Which spp. does Cheyletiella mostly infect?

A

Dogs and cats but can also infect rabbits and humans.

26
Q

What is its appearance?

A

A waisted body with claw like palps. It also has combs on the ends of its legs.

27
Q

What may be seen when diagnosing with a coat brushing?

A

Walking dandruff

28
Q

What is the genus that includes the ‘red mite’ of poultry?

A

Dermanyssus

29
Q

What does it look like?

A

Spider like

30
Q

What is important about its life cycle?

A

Most of the time is spent off the host and they only visit poultry at night to feed. Adult mites can survive for months without feeding so reservoir populations can build up.

31
Q

What is the correct name for the harvest mite?

A

(Neo-)Trombicula autmnalis.

32
Q

How is it recognised?

A

Bright orange and hairy, (only the larval stage is parasitic so 6 LEGS!)

Parasitology (8 decks)

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