Bacteria, fungi and yeast of the skin (part 2)

Question 1

What are 2 examples of bacterial diseases of production animals?

Answer 1

• erysipelothrix in pigs
• foot rot in sheep, goats, cattle, horses

Question 2

What bacteria causes erysipelothrix in pigs?

Answer 2

• erysipelothrix rhusiopathiae
  
  • gram positive, catalase negative, rod shaped, non-spore forming
  • produces H2S
  • non-haemolytic

Question 3

What condition does this pig have and what is it presenting?

Answer 3

• erysipelothrix
  
  • present in tonsillar tissues, shed in faeces
  • symptoms: febrile episodes, painful joints, lethargy, distress
  • diamond skin

Question 4

How do you treat erysipelothrix?

Answer 4

• penicillin
• tetracycline

Question 5

What are the 2 steps of foot rot infection?

Answer 5

• 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

Question 6

What does development of footrot lesions depend on?

Answer 6

• 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

Question 7

What are the fungi affecting the skin?

Answer 7

• yeasts e.g. malassezia
• dermatophytes
• microsporum spp
• trichophyton spp
• envrionmental fungi

Question 8

What are the signs/ gross pathology seen in fungal diseases?

Answer 8

• pruritus
• alopecia
• scaling/crusts
• pustules/ crusts
• nodules, tumours

Question 9

What are the types of fungal disease?

Answer 9

• 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

Question 10

Ringworm: what are the 3 important anamorphic genera?

Answer 10

• microsporum
• trichophton
• epidermophyton

Question 11

General signs of dermatophytes?

Answer 11

• scaling
• alopecia

Question 12

What is Trychopython spp?

Answer 12

• common soil dermatophilic fungus
• rarely causes infection in man/ animals
• readily isolated from soil by hair baiting

Question 13

What are some features of Microsporum canis?

Answer 13

• macrocondria are abundant
  
  • thick-walled with many septa, up to 15
• macrocondria are often hooked or curved at ends
• microcondria are small and clavate

Question 15

What is the most common dermatophytes of cattle?

Answer 15

• Trichophyton verrucosum

Question 16

What age of cattle, and what season is dermatophytosis most common in?

Answer 16

• 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

Question 17

WHat is the treatment for Dermatophytes of cattle?

Answer 17

• topical treatment
• vaccination

Question 18

What causes Dermatophytes in dogs and cats?

Answer 18

• dogs:
  
  • microsporum canis (70%)
  • M.gypseum (20%)
  • trichophyton mentagrophytes (10%)
• cats:
  
  • microsporum canis

Question 19

What are the clinical signs of dermatophytes of dogs/cats?

Answer 19

• 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

Question 20

What is the primary cause of dermatophytes in horses?

Answer 20

• trichophyton equinum, T.mentagrophytes

Question 21

What are the clinical signs in horses with dermatophytes and how is it transmitted?

Answer 21

• 1 or more patches of alopecia and erythema
• scaling
• crusting
• especially in saddle and girth areas
• transmitted by direct contact and grooming equipment

Question 22

How do you treat horses with dermatophytes?

Answer 22

• topical treatment
  
  • whole body rinses
  • treatment of individual lesions
• isolation of affected horses

Question 23

What is Dermatophytes in pigs, sheep and goats caused by? Which is it common in?

Answer 23

• 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

Question 24

What does the severity of ringworm disease depend on? (2)

Answer 24

• strains or species of fungus involved
• sensitivity of the host to a particular fungus

Question 25

Why would more severe reactions occur with ringworm?

Answer 25

* when a dermatophyte crosses host lines

Question 26

How do you diagnose dermatophytes?

Answer 26

* hair plucks/ coat brishings, UV light (woods lamp) * look for fungal hyphae * growth \> very slow, start treatment straight away

Question 27

What are the treatments for dermatophytes?

Answer 27

* antifungals (griseofulvin, ketoconazole) * dip or shampoo * clipping of hairs may reduce spreading * keep animals in isolation * can be zoonotic

Question 28

What causes Malassezia? Where is it found and what can it cause?

Answer 28

* cause: Malassezia pachydermatis * found on skin and in ears of healthy dogs/cats * can cause dermatitis

Question 29

What are the clinical signs of malassezia?

Answer 29

* erythema and pruritus * alopecia * usually secondary to underlying disease * diagnosis : acetate strip cytology

Question 30

What is Sporotrichosis? What causes it?

Answer 30

* 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

Question 32

What do environmental fungi cause?

Answer 32

* rare cause of skin disease * opportunistic subcutaneous infection * eumycetoma * phaehyphomycosis * zygomycosis * hyalohyphomycosis * cutaneous and systemic mycoses * histoplasmosis * coccidioidomycosis * blastomycosis * cryptococcosis

Question 33

What are the portal of entries for fungi?

Answer 33

* primary mycoses - inhale spores * subcutaneous - inoculation of skin, trauma * cutaneous, superficial - contamination of skin

Question 34

What are the virulence factors?

Answer 34

* toxins * capsule * thermal dimorphism * hydrolytic enzymes * inflam stimulants

Question 35

What are mycetomas?

Answer 35

* subcutaneous * granulomatous nodules - tissue * tissue granules * pigmented fungi - curvularia spp and Madurella spp (black/ dark grain) * Acremonium spp - white - grained