Bacteria, fungi and yeast of the skin (part 2) Flashcards
What are 2 examples of bacterial diseases of production animals?
- erysipelothrix in pigs
- foot rot in sheep, goats, cattle, horses
What bacteria causes erysipelothrix in pigs?
- erysipelothrix rhusiopathiae
- gram positive, catalase negative, rod shaped, non-spore forming
- produces H2S
- non-haemolytic
What condition does this pig have and what is it presenting?
- erysipelothrix
- present in tonsillar tissues, shed in faeces
- symptoms: febrile episodes, painful joints, lethargy, distress
- diamond skin
How do you treat erysipelothrix?
- penicillin
- tetracycline
What are the 2 steps of foot rot infection?
- starts with Fusobacterium necrophorum
- gram negative rod, strict anaerobe
- found in environment
- can enter foot through breakage or weakness of the skin surrounding hoof
- second stage: dichelobacter nodosus
- gram negative anaerobe
- fimbrial adhesion structures
- treated with antibiotics
- only bacterium initiating invasion of the hoof matrix
What does development of footrot lesions depend on?
- the presence of D.nodosus and the particular strain involved
- host susceptibility
- environmental factors (temps of >10 degrees, adequate moisture, pasture length/ density)
- predisposing infection with other bacteria between the claws e.g. F.necrophorum
What are the fungi affecting the skin?
- yeasts e.g. malassezia
- dermatophytes
- microsporum spp
- trichophyton spp
- envrionmental fungi
What are the signs/ gross pathology seen in fungal diseases?
- pruritus
- alopecia
- scaling/crusts
- pustules/ crusts
- nodules, tumours
What are the types of fungal disease?
- superficial
- located in the epidermis
- often endogenous, already present on the skin, contact-spread or spores
- dermatophytes and yeasts
- candida albicans
- malassezia yeast
- ringworm
- subcutaneous infections
- mostly exogenous
- located in dermis and subcutaneous tissues
- inserted by trauma
Ringworm: what are the 3 important anamorphic genera?
- microsporum
- trichophton
- epidermophyton
General signs of dermatophytes?
- scaling
- alopecia
What is Trychopython spp?
- common soil dermatophilic fungus
- rarely causes infection in man/ animals
- readily isolated from soil by hair baiting
What are some features of Microsporum canis?
- macrocondria are abundant
- thick-walled with many septa, up to 15
- macrocondria are often hooked or curved at ends
- microcondria are small and clavate
What is the most common dermatophytes of cattle?
- Trichophyton verrucosum
What age of cattle, and what season is dermatophytosis most common in?
- most common in calves
- nonprutitic lesions
- generalised skin disease may develop
- lesions are characteristically discrete, scaling patches of hair loss with grey-white crust formation
- most common in winter
- more common in English species
- spontaneous recovery common
WHat is the treatment for Dermatophytes of cattle?
- topical treatment
- vaccination
What causes Dermatophytes in dogs and cats?
- dogs:
- microsporum canis (70%)
- M.gypseum (20%)
- trichophyton mentagrophytes (10%)
- cats:
- microsporum canis
What are the clinical signs of dermatophytes of dogs/cats?
- dogs: alopecia, scaly patches, broken hairs, regional or generalised folliculitis and furunculosis with papules and pustules
- cats: focal alopecia, scaling, and crusting around ears, face or extremities
What is the primary cause of dermatophytes in horses?
- trichophyton equinum, T.mentagrophytes
What are the clinical signs in horses with dermatophytes and how is it transmitted?
- 1 or more patches of alopecia and erythema
- scaling
- crusting
- especially in saddle and girth areas
- transmitted by direct contact and grooming equipment
How do you treat horses with dermatophytes?
- topical treatment
- whole body rinses
- treatment of individual lesions
- isolation of affected horses
What is Dermatophytes in pigs, sheep and goats caused by? Which is it common in?
- pigs: microsporum nanum, often asymptomatic
- sheep/ goats: M.canis, M.gypseum, T. verrucosum
- in show lambs problematic, but not commonly in production flocks of sheep and goats
What does the severity of ringworm disease depend on? (2)
- strains or species of fungus involved
- sensitivity of the host to a particular fungus
Why would more severe reactions occur with ringworm?
- when a dermatophyte crosses host lines
How do you diagnose dermatophytes?
- hair plucks/ coat brishings, UV light (woods lamp)
- look for fungal hyphae
- growth > very slow, start treatment straight away
What are the treatments for dermatophytes?
- antifungals (griseofulvin, ketoconazole)
- dip or shampoo
- clipping of hairs may reduce spreading
- keep animals in isolation
- can be zoonotic
What causes Malassezia? Where is it found and what can it cause?
- cause: Malassezia pachydermatis
- found on skin and in ears of healthy dogs/cats
- can cause dermatitis
What are the clinical signs of malassezia?
- erythema and pruritus
- alopecia
- usually secondary to underlying disease
- diagnosis : acetate strip cytology
What is Sporotrichosis? What causes it?
- reported in dogs, cats, horses, cows, camels, dolphins, goats
- zoonotic (esp cats)
- caused by Sporothrix schenckii
- dimorphic and forms mycelia on vegetation
- yeast-like in tissue and media at 37 degrees
- difficult to treat
- very contagious
What do environmental fungi cause?
- rare cause of skin disease
- opportunistic subcutaneous infection
- eumycetoma
- phaehyphomycosis
- zygomycosis
- hyalohyphomycosis
- cutaneous and systemic mycoses
- histoplasmosis
- coccidioidomycosis
- blastomycosis
- cryptococcosis
What are the portal of entries for fungi?
- primary mycoses - inhale spores
- subcutaneous - inoculation of skin, trauma
- cutaneous, superficial - contamination of skin
What are the virulence factors?
- toxins
- capsule
- thermal dimorphism
- hydrolytic enzymes
- inflam stimulants
What are mycetomas?
- subcutaneous
- granulomatous nodules - tissue
- tissue granules
- pigmented fungi - curvularia spp and Madurella spp (black/ dark grain)
- Acremonium spp - white - grained
