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Flashcards in Parasitology - Mites Deck (55)
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1

How big are mites?

They're microscopic. Less than 0.3 mm.

2

Can you kill them with insecticides?

No, like ticks, they're not insects. They in the class Arachnida.

3

What is the condition caused by mites?

Mange 

4

How do their life cycles differ from ticks in terms of where they spend their time?

Ticks spend most of their time on the ground, even if they're 1,2 & 3-host ticks. 

Mites spend most of their time on the host.

5

How are mites classified? 

By where they're located on the host.

Burrowing mites & Surface mites.

Most species of veterinary importance are parasidic.

6

What are the three main genera of BURROWING MITES?

Sarcoptes

Knemidocoptes

Demodex

7

What conditions does Sarcoptes cause & in what species?

Sarcoptic mange in

PIGS: important condition (~35% harbour inapparent infections); ears commonest site of infection; transmission from sows to piglets during suckling & boars to gilts @ surface; adversely affects productivity

CATTLE: mostly in housed cattle, potentially most severe of cattle manges; notifiable in Canada & parts of US; lesions on neck & tail; adversely affects productivity

SHEEP: notifiable in UK (last case 30 yrs ago)

HORSES: notifiable in UK (2 cases since 1948); lesions spread from head, neck, shoulders to rest of body

DOGS: highly contagious, intense itching, edges of ears first affected, later muzzle, face & elbows (rest of body)

CATS: rare

 

8

How do you recognise an adult Sarcoptes mite? 

- small, round - dorsal PEGS arranged in rows
& spines
- terminal anus

9

How many legs do burrowing mites like Sarcoptes & Demodex have as adults and nymphs?

They have four pairs of legs as adults & nymphs and only three pairs as larvae.

10

What is the life cycle of the Sarcoptes scabiei?

~3 weeks:


Fertilised female creates tunnel in upper epidermis → lays eggs “in pocket” → feeds on liquid oozing from damaged tissues → eggs hatch in <1 week larvae crawl to surface then burrow back into epidermis to form “moulting pockets” → moult to become nymphs → moult 2x to become adults

11

How is Sarcoptes diagnosed? 

- Skin scraping to expose
capillary blood
- add KOH & warm over
Bunsen burner
- place coverslip on top
- ID X-section of mites on
epidermis

12

What are the clinical signs of sarcoptic mange?

- erythema w/ papulae
- scale, crust formation, alopecia
- intense pruritus (1 week), self-inflicted
trauma & scabs
- wrinkling & thickening of skin
NB pigs & humans can have hypersensitivity reax w/i hours

13

Another burrowing-mite genus is Knemidocoptes. What species does this mite attack? 

Poultry/wild birds

14

How is Knemidocoptes mite identified? 

Usually you can figure out its a Knemitodcoptes mite if there's mange on a bird. 

You can also look under a microscope for a U-shaped chitinous bar behind its head, and a terminal anus.

15

What are the different species of knemidocoptes? What are the common names of the conditions they cause?

K. mutans
("scaly leg" - poultry)

K. gallinae
("depluming itch" - poultry)

K. pilae - ("scaly beak/face"- cage birds)

NB: Knemidocoptes is the only burrowing mite that affects birds.

16

What is the pathogenesis of Knemidocoptes mutans?

K. mutans causes scaly leg in poultry.

- mites burrow beneath leg scales causing them to loosen & rise giving a ragged appearance to legs & feet.
- Affected birds may have distorted feet &
claws & show signs of lameness.

17

What is the pathogenesis of Knemidocoptes gallinae, the cause of "depluming itch" in poultry?

- mites burrow into feather shafts which results in intense pain & irritation causing birds to pull out body feathers

- very painful

18

What is the pathogenesis of Knemidocoptes pilae, which causes scaly beak or scaly face in caged birds?

- mites attack bare or lightly feathered parts of beak, cere, face & body
- first see scaliness @ base of beak → spreads across face & sometimes body
- little priuritus

19

Demodex is another important burrowing mite. What is special about the way it looks under the microscope that helps you to ID it?

Demodex is cigar-shaped with four stumpy legs at anterior end.

20

What is the name of the condition caused by Demodex burrowing mites?

Demodecosis

21

There are two types of demodecosis caused by the burrowing mite, Demodex. What are they and how do they differ?

a) Squamous demodecosis - less serious, dry reax with alopecia, desquamation & skin thickening; absent/mod. pruritus


b) Pustular (or follicular) demodecosis - more serious, resulting from invasion by Staphylococci. Skin becomes wrinkled & thickened & contains numerous pustules that ooze serum, blood or pus; animals might be severely disfigured; severe pruritus associated with secondary infection.

22

Which species do Demodex burrowing mites attack?

Found on all domestic animals & humans, each having its own species.

We are concerned with dog infestation.

May cause severe skin disease.

23

How do dogs "catch" Demodex infestation aka demodecosis? 

- transmitted by bitch → puppies during suckling; lesions seen first on muzzle, face & forelimbs

24

What are predisposing factors in dogs becoming infected by Demodex burrowing mites?

- family susceptibility - weak puppies
- immunosuppression - Demodex thought to cause cell-mediated immunodeficiency by suppressing normal T-cell response;
- immunosuppressants - corticosteroids

25

What is the Demodex life cycle?

3 weeks:

adult → egg → larvae → nymph → adult

Normally live as commensals in skin of most animals, spending their entire life cycle in hair follicles & sebaceous glands.

26

Mites can act as intermediate hosts for other types of parasites. Give two examples of parasites that use the Oribatid mites, which themselves are NOT parasitic. 

Oribatid mites, though not parasitic themselves and are more like ticks that spend their time OFF hosts, are intermediate hosts for several nematode species that can become tapeworms in final mammalian hosts.

Anoplocephala - equid tapeworm

Moniezia - ruminant tapeworm

27

How do non-burrowing mites differ from burrowing mites in terms of behaviour and location on the host?

Non-burrowing, aka "surface" mites, live on the surface of the skin, some feeding on skin scales or tissue (a bit like chewing lice vs. blood-sucking lice), although some such blood too.

28

How do surface/non-burrowing mites differ in appearance to burrowing mites? 

They are more oval in shape with long legs (pedicels) that are either segmented (Psoroptes) or non-segmented (Chorioptes). The pedicels have funnel-shaped or cup-shaped SUCKERS mounted on the ends.

See photo of Psoroptes.

29

What are the main species or genera of non-burrowing mites? 

Psoroptes

Chorioptes

Otodectes

Cheyletiella

30

What is psoroptic mange and what is the pathogenesis? Which animals are affected?

Psoroptic mange is also known as “sheep scab”, but it also affects cattle, horses and rabbits.

Psoroptes ovis - sheep & cows

Ps. equi - horses

Ps. cuniculi - rabbits & horses

Pathogenesis:

- though NOT BURROWING, it is very active in keratin layer of skin & has mouthparts that abrade skin

- antigenic material in faeces → hypersensitivity reax → inflammation, serous exudation, dry yellow crust & scale formation → self-inflicted trauma (intense pruritus, rubbing off fleece)

- impaired productivity (poor live-weight gain)

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