6.3 Arthropods 3 Flashcards

1
Q

mites are in what class

A

Arachnida

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2
Q

Mites; General types of mites

A
  • itch and mange mites
  • bloodsucking mites
  • mites in the respiratory system
  • mites in the subcutaneous tissues
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3
Q

Mites; Morphology

A
  • Smaller than ticks with membranous cuticle
  • Capitulum or “false head”
  • anterior and terminal
  • mouthparts - hypostome is unarmed
  • 4 pairs of legs as adults
  • Larvae look like adults but have 3 pairs of legs
  • Nymphs look like adults with 4 pairs of legs but are not sexually mature
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4
Q

Mites; General Life Cycle

A
  • all have simple metamorphosis
  • life cycle completed on one host, host specific
  • all follow the general plan of egg to larva to nymph to adult
  • feed on hair, fur, skin, secretions, etc.
  • diverse morphological variations depending on host and location on host
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5
Q

Life Cycle - Mites

A

Egg > Larva (3 pairs) > Nymph (4 pairs) > Adults (4 pairs)

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6
Q

Sarcoptes scabiei diseases

A

scabies/sarcoptic mange mite, itch mite

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7
Q

Sarcoptes scabiei; general hosts, site of infection

A
  • wide variety of hosts - specific strains for each
  • Sarcoptes sp. burrow into stratum corneum
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8
Q

Sarcoptes scabiei; Adult morphology

A
  • oval, short-legged mite with posterior two pairs not extending beyond edge of body
  • body has many spines, particularly on dorsum
  • pedicels of pretarsi are long and unsegmented
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9
Q

Sarcoptes scabiei; Life Cycle, transmission

A
  • all stages on one host, short survival off host
  • females tunnel into epidermis and lay eggs
  • larvae, nymphs and newly emerged adults found in skin pockets
  • transmission by direct contact
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10
Q

Sarcoptes scabiei; Pathogenesis

A
  • burrowing mites - secretions and excretions may lead to hypersensitivity
  • self inflicted damage may cause alopecia and bleeding leading to scabbing
  • secondary infections common and may progress to pyoderma
  • emaciation and death may result
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11
Q

Sarcoptes scabiei; Lesions/Clinical Signs, predilection sites

A
  • initial papule ruptures and exudes serum, pruritus evident
  • progresses to thickened, dry, flaky, skin (hyperkeratosis
    and exfoliation) with scabbing and alopecia - chronic disease may continue for months with continuing pruritus
  • initial lesions usually in less haired areas
  • predilection sites:
    -dogs - head, ears, elbows, hocks, ventral body
    -ruminants - head and neck
    -pigs - head around ears, nose and eyes, inner thighs
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12
Q

Sarcoptes scabiei; Diagnosis

A
  • skin scrapings with a glycerine covered scapel performed at the edge of a lesion - examine microscopically
  • detritus from a scraping may be digested using 5% potassium hydroxide (near boil)
  • mites may be mounted in Berlese solution
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13
Q

Sarcoptes scabiei; Treatment

A
  • hair should be clipped and all crusty material removed from affected areas prior to treatment
  • selamectin has label claim for dogs - up to 2 doses required
  • moxidectin in Advantage-Multi highly effective
  • large animals – various endectocides have activity
    and label claim against sarcoptic mange mites
  • older treatment - amitraz provides good control after a single dermal application – note toxicity to humans
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14
Q

Demodex spp.

A

(follicle mite or demodectic mange mite)

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15
Q

Demodex spp.; general; where do they infect, what do they cause, hosts

A
  • infect hair follicles, sebaceous and apocrine glands
  • cause demodectic mange or demodicosis
  • many species infected with their own particular species of follicle mite
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16
Q

Demodex spp.; Morphology

A
  • adults elongate, wormlike with stubby legs
17
Q

Demodex spp.; Life Cycle

A
  • mites are found on normal skin
  • all stages on host within or at the mouth of hair follicles
  • transmission by direct contact
18
Q

Demodex spp.; Pathogenesis – Cattle/Goats

A
  • Uncommon to rare
  • Pinhead to egg-sized nodules
  • Nodules filled with pus and mites – no need to deep scrape for diagnosis
19
Q

Demodex canis

A

(canine follicle mite or demodectic mange mite)

20
Q

Demodex canis; Pathogenesis - Dogs

A

mites are found on normal skin, therefore the pathogenesis is not fully understood

two general forms of the disease:
1) localized demodicosis, related to stress and possibly hereditary predisposition
2) generalized demodicosis
a) juvenile onset
b) adult onset

21
Q

Demodex canis; Lesions and Clinical Signs - Dogs

A
  • localized demodicosis - few small lesions with some hair loss and scaling (heal spontaneously)
  • generalized demodicosis - generalized scaling, alopecia and erythema (“red mange”)
  • follicle rupture leads to major secondary disease that may give rise to systemic clinical signs
  • pododermatitis - severe lesions restricted to feet
22
Q

Demodex canis; Diagnosis

A
  • In dogs - deep skin scrapings with scapel performed at the edge of a lesion - examine microscopically – the root of plucked hairs from the edge of a lesion can also be examined for mites
  • detritus from a scraping may be digested using 5% potassium hydroxide (near boil)
  • In cattle/goats – express and examine contents of nodules
  • mites may be mounted in Berlese solution
23
Q

Demodex canis; Treatments - Dogs

A
  • localized demodicosis - generally heal spontaneously, may use rotenone topically
  • generalized demodicosis
  • amitraz (Mitaban) is effective BUT treatments can be long and frustrating
  • moxidectin in Advantage-Multi highly effective - ivermectin (off-label)
24
Q

Otodectes cynotis

A

(ear mite)

25
Q

Otodectes cynotis; general; where are they found, movement, host

A
  • found in ear canal and adjacent skin
  • actively move
  • entire life history on single host
26
Q

Otodectes cynotis; Morphology

A
  • white oval mite with long legs extending past the body
  • short, unsegmented pretarsi with a large sucker
27
Q

Otodectes cynotis; Life Cycle, transmission

A
  • egg to adult - 2 or 3 weeks
  • transmission by direct contact
28
Q

Otodectes cynotis; Pathogenesis/Lesions/Clinical Signs

A
  • dermatitis and pruritis result from reactions to mechanical damage and secretions
  • scratching and shaking of head
  • dark exudate from ear
  • mites can move out of ear and be found elsewhere
29
Q

Otodectes cynotis; Treatment

A
  • clean out debris from ears, particularly dried exudate, thoroughly
  • instill topical acaracide into ear canal (rotenone, methyl phthalate, thiabendazole, milbemycin)
  • selamectin has label claim for treatment and control of ear mites of cats and dogs
  • moxidectin in Advantage-Multi has label claim and is highly effective
30
Q

Cheyletiella spp.

A

(fur mite)

31
Q

Cheyletiella spp.; Morphology

A
  • larger, more robust mite (“walking dandruff”)
  • legs long and extend beyond body margin
  • large palps (“fifth pair of legs” – see arrows)
  • comb-like structures on the ends of each leg
32
Q

Cheyletiella spp.; Life Cycle

A
  • mites tunnel into keratin layer of skin and feed on epidermal debris
  • transmission by direct contact
33
Q

Cheyletiella spp.; Pathogenesis/Lesions/Clinical Signs

A
  • dorsal seborrhea, generally non-pruritic
  • usually seen in younger dogs; these animals will usually have many mites
34
Q

Chorioptes spp.

A

(mange mite of ruminants and horses)

35
Q

Chorioptes spp.; Morphology

A
  • Oval and up to 0.5 mm
  • Long legs
  • Short unsegmented pedicels with large suckers
36
Q

Chorioptes spp.; Pathogenesis/Lesions/Clinical Signs

A
  • mites feed at surface
  • small early lesions that may coalesce
  • cattle - most frequent with animals that are housed
  • more common in the winter and often spontaneously disappears in the summer
    – may be pruritic – animal may damage hide
  • sheep, legs or scrotal area - lesions not common
  • horses, lesions more extensive with pruritus - animals may stomp and rub.
37
Q

Psoroptes spp.

A

(scab mites)

38
Q

Psoroptes spp.; Morphology

A

*Oval and up to 0.6 mm
* Long legs
* Long segmented pedicels with small suckers

39
Q

Psoroptes spp.; Pathogenesis/Lesions/Clinical Signs

A
  • mites by piercing the skin
  • Inflammation and hypersensitivity
  • red papules at sites of bites followed by skin thickening
  • intense puritis produces self-inflicted alopecia
  • serious but easily treated (no longer reportable)