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Parasitic skin infections - Pathology (view source)
Revision as of 10:44, 11 October 2008
, 10:44, 11 October 2008no edit summary
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==Fleas==
*Occurs in cats and dogs mainly
*Occurs in cats and dogs mainly
*Irritation caused by enzymes, anticoagulants and histamine-like substances
*Irritation caused by enzymes, anticoagulants and histamine-like substances
*Grossly:
*Grossly:
**Red papules and secondary excoriations
**Red papules and secondary excoriations
==[[Insecta|Flies]]==
==[[Insecta|Flies]]==
*Bites may cause irritation, anaemia, toxicity or hypersensitivity
*Bites may cause irritation, anaemia, toxicity or hypersensitivity
**Larvaae are deposited in wounds
**Larvaae are deposited in wounds
**Penetrate and liquify tissue
**Penetrate and liquify tissue
==Helminths==
==Helminths==
===Cutaneous habronemiasis===
===Cutaneous habronemiasis===
**Larvae and necrotic tissue
**Larvae and necrotic tissue
**Granulation tissue with neutrophils along ulcerated surface
**Granulation tissue with neutrophils along ulcerated surface
===Hookworms===
*Caused by [[Ancylostomatoidea|''Ancylostoma'' or ''Uncinaria'']]
*Grossly:
**Red papules -> lichenified alopecic areas
**Mainly of dog feet
**Foot pads may soften with keratinised area separation
**Possible secondary bacterial dermatitis and [[Skin Glossary - Pathology|paronychia]]
*Microscopically:
**Hyperplastic spongiotic perivascular dermatitis
**Eosinophils
**Crusts
**Migration tracts
===Onchocerciasis===
===Onchocerciasis===
**Eosinophils, adult and microfilarial parasites
**Eosinophils, adult and microfilarial parasites
**[[Skin Glossary - Pathology|Epidermal hyperkeratosis, parakeratosis, acanthosis]], eosinophilic microabscesses and crusts
**[[Skin Glossary - Pathology|Epidermal hyperkeratosis, parakeratosis, acanthosis]], eosinophilic microabscesses and crusts
==Lice==
*Infestation is called '''pediculosis'''
*May cause anaemia (sucking lice), weakness, discomfort and damage to hair or wool
*More common in low temperatures when hair is longer
*Host-specific
*Spread by direct contact
*Most lesions are due to self-inflicted trauma
*Grossly:
**Papules, crusts, secondary excoriations
**Eggs and lice visible in lesions
==Mites==
===Cheyletiellosis===
*Caused by ''Cheyletiella'' sp.]]
*Occurs in dogs, cats, rabbits, humans and wild animals
*In dogs and cats: hyperkeratosis - dry, white, scaly dandruff along back
*May be asymptomatic
*Grossly:
**Focal, multifocal or generalised red papules or crusts
*Microscopically:
**Superficial perivascular dermatitis
**Eosinophils
===Chorioptic mites===
*Host-specific
*In cattle, horses, goats
*Caused by [[Suborder: Astigmata, astigmatid mites|''Chorioptes'' spp.]]
*Grossly:
**Erythematous, papular, crusty lesions
**Hairless, thickened skin
**Areas usually affected:
***Horses: lower hind legs
***Cattle: lower hind legs, scrotum, perineum, tail, udder, thigh
***Sheep: lower hind legs and scrotum
***Goats: lower hind legs, hindquarters, abdomen
===Demodicosis===
*[[Suborder: Astigmata, astigmatid mites|''Demodex'']] are normal inhabitants of hair follicles and sebaceous glands
*Have to have increased number of immature mites to classify as infestation
*Host-specific
*Occurs in dogs, cattle, sheep, goats, pigs, horses and cats
*Transmits during nursing from dam to offspring
*''Demodex canis'' in dogs:
**Generalised or localised
**Mainly young dogs affected or adults with other disease ([[Adrenal Glands - Pathology#Adrenal Hyperfunction|hyperadrenocorticism]], [[Thyroid Gland - Pathology#Hypothyroidism|hypothyroidism]])
**Often inherited in pure bred
**Grossly:
***Localised: scaly, erythematous, macular, alopecic areas; usually face or front legs
***Generalised: large, coalescing lesions, patches, erythema, alopecia, scales, crusts
**Microscopically:
***Localised: lymphoplasmacytic perifolliculitis with hyperkeratinisation, sebaceous adenitis, low pigment, intraluminal mites
***Generalised: perifolliculitis and follicular hyperkeratosis, follicular pluggingf, bacterial proliferation, bacterial neutrophilic folliculitis
****May cause folliculat rupture -> furunculosis, cellulitis, lymphadenitis and septicaemia
===Notoedric mites===
*Rare but very contagious
*Caused by [[Suborder: Astigmata, astigmatid mites|''Notoedres cati'']]
*Grossly:
**Erythematous papular rash -> scales, crusts, alopecia -> lichenification when chronic
**Start on neck and ears -> head, face, paws -> generalised
*Microscopically:
**Epidermal hyperplasia, spongiosis, crusts
**Superficial perivascular dermatitis
**Eosinophils
===Otodectic mites===
*Caused by [[Suborder: Astigmata, astigmatid mites|''Otodectes cynotis'']]
*In external ear canals of carnivores, occasionally elsewhere
===Psoroptic mites===
*Occurs in cattle, sheep, horses, goats, rabbits and other animals
*Host-specific
*[[Suborder: Astigmata, astigmatid mites#Psoroptes cuniculi|''Psoroptes cuniculi'']] in ear canals of rabbits, horses, goats and sheep
*[[Suborder: Astigmata, astigmatid mites|''P.equi'']] at base of mane, ttail and forelock in horses
*[[Suborder: Astigmata, astigmatid mites|''P.ovis'']] in sheep ('''sheep scab''')and cattle
**Thickened skin and dry scales and crusts
**Starts at withers and spreads due to self trauma
**Microscopically:
***Spongiotic, hyperplastic or exudative superficial perivascular dermatitis
***Eosinophils
===Scabies===
*Caused by [[Suborder: Astigmata, astigmatid mites|''Sarcoptes scabiei'']]
*Highly contagious
*Mainly in pigs, dogs, also horses, cattle, sheep, goats and cats
*Intense pruritus due hypersensitivity to mites borrowing through stratum corneum
*Usually starts with external pinnae -> head -> neck -> generalised
*Grossly:
**Erythematous [[Skin Glossary - Pathology|macules, papules, crusts]]
**If chronic -> [[Skin Glossary - Pathology|lichenified]], hairless
*Microscopically:
**Hyperplastic, spongiotic, superficial perivascular dermatitis
**Crusting, eosinophil infiltration
**Mites are not commonly seen, but eggs and feces may be found in stratumn corneum
===Trombiculidiasis===
*Harvest mite infestation (chiggers) - [[Suborder: Astigmata, astigmatid mites|''Trombicula'' sp.]]
*Form tunnels in epidermis by injecting saliva - eat digested tissue fluid
*Intense pruritus
*Grossly:
**Small, red [[Skin Glossary - Pathology|papules or crusts]]
**Orange to red larvae
**On skin close to plants or the ground
*Microscopically:
**Hyperplastic, superficial perivascular dermatitis
**[[Eosinophils - WikiBlood|Eosinophils]], [[Mast Cells - WikiBlood|mast cells]]
**Intraepidermal mites
==Protozoa==
==Protozoa==
**Macrophages, some lymphocytes and plasma cells - periadnexal pattern, may affect sebaceous glands
**Macrophages, some lymphocytes and plasma cells - periadnexal pattern, may affect sebaceous glands
**Organisms may be found extra or intracellularly
**Organisms may be found extra or intracellularly
==Ticks==
*Local reaction depends on host hypersensitivity and [[Suborder: Metastigmata, ticks|tick's]] secretions
*Grossly:
**Focal erosions, erythema, crusted ulcers, sometimes alopecia and nodules
*Microscopically:
**Epidermal and dermal necrosis
**Perivascular of diffuse inflammation and necrotic margins
**Eosinophils, macrophages and lymphocytes in exudate
**May form granulomas containing collagenous fibres and lymphoid follicles within dermis