Difference between revisions of "Parasitic skin infections - Pathology"

Harvest mite infestation (chiggers) - Trombicula sp.
Form tunnels in epidermis by injecting saliva - eat digested tissue fluid
Intense pruritus
Grossly:
- Small, red papules or crusts
- Orange to red larvae
- On skin close to plants or the ground
Microscopically:
- Hyperplastic, superficial perivascular dermatitis
- Eosinophils, mast cells
- Intraepidermal mites

Protozoa

Cutaneous infection may become a part of systemic infection
Mostly caused by Leishmania
Transmitted by sandflies
Occurs in dogs, cats and rodents (also humans)
Grossly in dog:
- Generalised alopecia
- Silvery white scales
- Nodules and ulcers if more severe
- Mainly on muzzle, ears and eyes where flies feed
Microscopically:
- Hyperkeratosis, parakeratosis, crusts
- Granulomatous nodules in dermis
- Macrophages, some lymphocytes and plasma cells - periadnexal pattern, may affect sebaceous glands
- Organisms may be found extra or intracellularly

Local reaction depends on host hypersensitivity and 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

@@ Line 52: / Line 52: @@
-===Scabies===
+===[[Scabies]]===
-*Caused by [[Sarcoptes|''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===