11. Demodectic mites, soft and hard ticks and other mites Flashcards
Demodex spp. General info. Morphology
- Prostigmatid mites
- hair follicle mites
- permanent, host-specific ectoparasites
- live on the hair follicles, sebaceous glands
- normal inhabitants of the skin of healthy individuals
- elongated, up to 0,2 mm, legs are very short
- eggs are lemon-shaped, later resembles pear seeds
Demodex spp by hosts (large animals), clinical signs
Horse: (rarely any serious problems)
- D. equi - body, patchy alopecia, scaling, nodules
- D. caballi - eyelids, muzzles
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Cattle:
- D. bovis - pea-sized nodules with caseous contents (pus, mites) on the neck, forequarters (dead colony of parasites in closed hair follicle)
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Goats (sheep):
- D. caprae (D. ovis) - nonpruritic papules and nodules over the face, neck, shoulders, which contain thick, waxy, greyish material
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Pigs:
- D. phylloides - lesions are rare
Demodex spp by hosts (small animals), clinical signs
DOG: - can be very serious and even life-threatening
- D. canis - certain breeds are at higher risk (Doberman, collie, German shepherd, etc)
- several types of demodicosis: localised/squamous demodicosis, generalised pustular demodicosis
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localised/squamous demodicosis:
3-6 moths puppies, muzzle area, around the eye, over bony projections - erythema, alopecia, seborrhoea, desquamation, hyperpigmentation. Usually no pruritis
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generalised or pustular demodicosis
Lesions spread to most parts of the body (mostly dorsally). Hair coat becomes sparse, skin is dry and erythematous (so-called red mange). Frequently with secondary Staphylococcus pyoderma
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CAT
- much rarer than in dogs
- D. cati, D. gatoi
Localised/squamous demodicosis in dogs
- under 2 years (usually 3-6 months)
- on the muzzle, around the eye, over the bony projection of extremities
- erythema, alopecia, seborrhoea, desquamation, hyperpigmentation
- usually no pruritis
Generalised/pustular demodicosis in dogs
- most parts of the body surface (mostly dorsally)
- sparse haircoat
- dry and erythematous skin (so-called red mange)
- frequently with secondary staphylococcal pyoderma
Cheyletiella mites. Species. Basic info. Morphology
- Cheyletiella yasguri (dog), C. blakei (cat), C. parasitivorax (rabbit)- much more common in animals with long hair
- permanent ectoparasites living in the hair coat, visiting the skin to feed on the keratin
— - up to 0,4-0,6 mm, huge palps with claw (hook)
Cheyletiella mites. Development and clinical signs
- eggs are attached to the hair, 2-3 mm above the skin
— - clinical signs are usually absent
- mild dermatitis, scaling skin (”walking dandruff”), dressy and sparse hair, pruritis
Harvest (chugger) mites. Morphology. Clinical signs
- Trombicula autumnalis (syn. Neotrombicula autumnalis)
- only the larvae are parasitic
- “harvest” because most active during August and September
— - hexapod larvae 0,2 mm, oval, orange, “hairy”, with scutum
— - clinical signs: papule, vesicle formation, hypersensitivity reaction, pruritis, excoriation, hair loss
Red mites
- Dermanyssus gallinae - poultry (occasionally mammals)
- nocturnal
- haematophagous 🩸ectoparasites, 8 months survival without blood meal
— - 1-1,5 mm, oval, spider-like, red when fully engorged
- long legs and chelicerae
— - larvae are non-feeding, two nymph stages
- entire cycle takes 1 week
— - clinical signs: restlessness, headshake, ruffled feathers, occasionally anaemia
- when in ear canal: ataxia (mammals: erythema, intense pruritis, skin lesions)
Soft ticks. Species, general info
- Argas persicus on poultry
- Argas reflexus* on pigeons (occasionally on mammals)
- nocturnal (except larvae), non-permanent
- haematophagous 🩸ectoparasites
Soft ticks. Morphology
- 5-10 mm, oval flattened, yellowish-brown
- reduced head is not visible from above
- cuticle is leathery, mamillated (no scutum)
- the body margin remains flattened even when fully engorged
Soft ticks. Development and clinical signs
- egg laying in cracks and crevices
- hexapod larvae attach to the host and feed for one week
- 2 or more nymph stages suck blood for hours, adults for minutes: several times
— - restlessness, decreased production, traces of blood-sucking on the skin, anaemia
Hard ticks. Species
- Idoxes ricinus
- Dermacentor marginatus
- Dermacentor reticulatus
- Haemaphysalis puncata
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Rhipicephalus spp
— - non-permanent, non-host specific, haematophagous 🩸ectoparasites
- pool feeders -> create haemorrhage and suck from there, not from blood vessels directly
MAKE A MAP HERE WITH MORHPHOLOGICAL DIFFERENCES
Hard ticks. Morphology
- larvae: 1 mm, nymph and male: 2-3 mm, engorged female: up to 10 mm or larger
- scutum: whole dorsal surface of males, only anteriorly in larvae, nymphs and females
- eyes (if present) are at the lateral margin of the scutum
- genital opening in the ventral midline, anteriorly (used to differentiate nymph from adult)
- anal opening (not connected to the blind, sack-like intestinal branches)
Hard ticks. Development
- mating on the host (during blood-sucking)
- egg-laying on the ground
- one host ticks: all three stages suck blood on the same host
- two-host ticks: larvae feedsmoults and nymph feeds on the same host, adults on another
- three host ticks: all three stages feed on different hosts, both moults in the surroundings
