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Dermatology 2 > Microbial skin disease > Flashcards

Microbial skin disease Flashcards

Bacterial, fungal, viral and protozoal skin disease

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Dermatology Board Prep flashcards
1
Q

Outline the management of caseous lymphadenitis

A

Remove positive individuals

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2
Q

Outline the management of greasy pig disease

A
  • Treat with systemic antibiotics
  • Topical antibacterial wash
  • Fluids (to treat toxic liver/kidney damage)
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3
Q

Which antibiotics are effective against greasy pig disease?

A

Sensitive to most antibacterials, incl. penicillins

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4
Q

Outline the management of erysipelas

A
  • Penicillin treatment

- Vaccine available

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5
Q

Describe the management of feline skin TB

A
  • Excision
  • Consider zoonotic potential
  • Antimicrobials: combinations in an initial and a continuation phase
  • In cases where resistance develops, may use traditional combination of rifampicin-isoniazid-ethambutol combination
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6
Q

Describe the initial phase of antimicrobial treatment for feline skin TB

A
  • Usually requires at least 3 drugs for 2 months

- Initial phase commonly uses rifampicin-fluoroquinolone-clarithromycin/azithromycin

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7
Q

Describe the continuation phase of antimicrobial treatment for feline skin TB

A
  • Usually requires 2 drugs and lasts for 4 months

- Usually uses rifampicin + either fluoroquinolone or clarithromyxin/azithromycin

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8
Q

Discuss the zoonotic risk of MRSA/MRSP

A
  • 1 in 3 people colonised but unaffected
  • Spread by direct contact, can be limited by basic hygiene
  • MRSP more easily contracted by dogs than MRSA, and likely poses less zoonotic risk
  • MRSP less antibiotic suscpetibility vs MRSA
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9
Q

What are risk factors that may predispose to nosocomial infections?

A
  • Antibiotic overuse
  • Antibiotic misuse (esp. not completing course)
  • Hospitalisation (duration)
  • Patient’s disease status, age
  • Number of diagnostic or therapeutic procedures
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10
Q

What are the 3 different types of mycotic infections and describe these briefly?

A
  • Superficial: surface epidermis and outer layers of hair and claws
  • Intermediate: infections of dermis and subcutaneous tissue
  • Deep: involve body organs
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11
Q

Describe the pathogenesis of dermatophytes

A
  • Use keratin in skin, nails, claws and hair to grow
  • Are confined to superficial layers of the skin
  • Only invade keratin of growing (anagen) hairs hence circular spread from initial infection site
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12
Q

What are the most common species that cause dermatophytosis?

A
  • Cats and dogs: T. metagrophytes, Microsporum canis
  • Cattle: T. verrucosum, less commonly also T. mentagrophytes
  • Horses: T. equinum
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13
Q

Which individuals are most at risk of dermatophytosis?

A
  • Cats more affected than dogs
  • No breed or sex predisposition
  • Especially common in young animals
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14
Q

What are the consequences of dermatophytosis?

A
  • Not debilitating, but effect on animal and hide value
  • Horses cannot race if have active infection
  • In cats, M. canis may cause no clinical signs (natural host)
  • T. mentagrophytes can cause serious and severe infection in dogs and cats as are not the natural hosts (mice/voles natural hosts)
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15
Q

Describe the clinical signs of dermatophytosis

A
  • Lesions variable
  • Often circular, patchy alopecia
  • Variable erythema and variable pruritus
  • Scale, crusts
  • can be local, patchy or generalised (Trichophyton more generalised in dogs)
  • Nails tend to be affected (loss, regrow often deformed, onychomycosis)
  • In horses often tack contact areas
  • Mass lesions (kerions) seen as lumps and bumps (rare)
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16
Q

Outline dermatophytosis in rabbits

A
  • T. metagrophytes and M canis most common (zoonosis)
  • Young animals most susceptible
  • Lesions often confined to pinnae and feet
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17
Q

What skin conditions are guinea pigs prone to?

A
  • Dermatophytosis
  • Mange
  • Trichofolliculoma
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18
Q

What are the 3 most common yeast/yeast like cutaneous infectious agents?

A
  • Candida
  • Malassezia
  • Trichosporon
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19
Q

What group of individuals are most susceptible to Candida infections?

A

Immunocompromised hosts

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20
Q

What species of Malassezia is most commonly isolated from the skin of mammals and birds?

A

M. pachydermatitis

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21
Q

List the breeds that have higher skin levels of M. pachydermatitis

A
  • Bassett hounds
  • Daschunds
  • Cocker spaniels
  • WHWT
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22
Q

What conditions favour infection with M. pachydermatitis?

A
  • Concurrent infection with Staphylococcus pseudintermedius

- Hot humid weather

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23
Q

Describe Malassezia dermatitis in dogs

A
  • Seborrhoeic dermatitis: inflamed skin wih yeasty smell, increase production and change in nature of sebum
  • Usually generalised
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24
Q

Describe the 2 types of Malassezia dermatitis

A
  • Scaly: dry seborrhoea, dandruff, seborrhoea sicca

- Greasy: more common, seborrhoea oleosa

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25
Q

How are deep mycoses acquired?

A
  • Direct inoculation traumatic implantation)
  • Ingestion
  • Inhalation or spores
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26
Q

What are the 2 subgroups of deep mycoses?

A
  • Subcutaneous

- Systemic

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27
Q

Outline deep mycoses in cats

A
  • Most common is Cryptococcus neoformans

- Cats with FIVE increased risk, more severe dsiease

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28
Q

Identify reservoirs for dermatophytosis

A
  • Infected animals/contaminated environment
  • Can survive in environment for many months
  • Fomite spread
  • Catteries/stables.yards carry high outbreak risk
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29
Q

Describe the 2 groups of carriers of dermatophytosis

A

1: Culture positive (dogs or) cats with subtle active infections
2: Culture positive (dogs or) cats with no active infection = carriers

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30
Q

Outline the control of dermatophytosis

A
  • Self limiting if healthy, effective immune response

- Vaccine available

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31
Q

Describe the equine epidemiology of dermatophytosis

A
  • Common, esp. in young horses
  • Subsequent exposure leads to less severe signs
  • Common sits of infection around tack
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32
Q

Explain the pathogenesis of Malassezia dermatitis

A
  • Primary condition allows yeast overgrowth
  • Yeast lipases alter surface lipid, causing smell
  • Epidermal turnover rises causing scale
  • Type I hypersensitivity to yeast develops
  • Vicious cycle, need to kill yeast to stop
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33
Q

Describe ringworm pathology

A
  • Incubation period ~1 week
  • Spores of fungus invade anagen hairs
  • Germinate and produce hyphae, invasion by digestion of keratin
  • New arthrospores produced from hyphae
  • Hair breaks off due to weakening leading to partial alopecia
  • Inflammatory reaction lead to folliculitis or furunculosis
  • Often red +/- pruritus,
  • Can develop into deeper tissues
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34
Q

Describe the common clinical signs of Malassezia dermatitis

A
  • Variable, usually generalised
  • Mostly affects hot/moist areas e.g. ears, pinnae, under tail, skin folds
  • Erythema, scale, greasy coat, otitis externa (may be only sign), variable pruritus, variable alopecia
  • Yeasty smell, especially with otitis
  • Eith chronic conditions will have lichenification and hyperpigmentation
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35
Q

Describe the appearance of Cryptococcus neoformans infections

A

Ulcerated skin lesions

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36
Q

Outline the methods used for the diagnosis of dermatophytosis

A
  • Trichogram: suspend in 10% KOH, look for hyphae and arthrospores
  • Wood’s lamp examination: some M canis strains fluoresce apple green, may get false positives and false negatives
  • Fungal culture, McKenzie toothbrush culture: pluck fluorescing hairs from edge of lesion of skin scrape edge of lesion. Comb coat with sterile toothbrush esp. if o obvious lesions (good for screening in contacts/sources)
  • Skin biopsies (histo +/- culture)
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37
Q

Describe the method for fungla culture

A
  • Sabouraud’s method
  • Takes 1-3 weeks
  • Used to identify type of dermatophyte
  • Grow in Sabouraud’s dextrose based media
  • Useful for rapid growth of dermatophytes, inhibitis saprophytic fungi
  • pH red with increased pH of alkaline products from pathogenic fungi
  • Does not enhance sporulation of dermatophytes needed for speciation
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38
Q

What is contained in Sabouraud’s media?

A

Contains phenol red pH indicator, cyclohexamide to inhibit growth of other fungi and gentamycin and chlorotetracycline to inhibit bacterial growth

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39
Q

What media can be used for sporulation of dermatophytes to facilitate speciation?

A
  • RSB

- Contains bromothymol blue indicator and chloramphenicol instead of gentamycin

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40
Q

What is the function of dermatophyte arthrospores?

A

Required for transmission

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41
Q

What are conidia?

A

Asexual, non-motile spores of a fungus and normally stained with lactophenol cotton blue

42
Q

Explain how dermatophytes can be differentiated from one another

A
  • Trichophyton: macroconidia up to 50um long, thin smooth walls, microconidia approx 4um
  • Epidermophyton: macroconidia up to 15um, thin smooth walls, microconidia absent
  • Microsporum: macroconidia up to 125um long with thick rough walls, microconidia approx 4-7um long
43
Q

How is Malassezia dermatitis diagnosed?

A
  • dermatological signs
  • Acetate tape test (ancilliary diagnostic aids)
  • Impression smear
  • Fungal culture may be needed
44
Q

Describe the diagnoses of deep mycoses

A
  • In a chronic non-healing lump, consider Cryptococcus as a potential diagnosis
  • Care - may be mycobacteria or fungal, esp. if ulcerated and chronic
  • Biopsy required for diagnosis
45
Q

Outline the management of dermatophytosis

A
  • Vaccination
  • Licensed antifungal agents
  • Malaseb shampoo
  • Spontaneous resoution in cattle and horses, rarely treated
46
Q

What drugs are commonly used in the treatment of dermatophytosis in rabbits?

A
  • Topical miconazole or clotrimazole

- Oral itraconazole or griseofulvin usually effective

47
Q

Which antifungal drugs are licensed for the treatment of dermatophytosis?

A
  • Systemic: azoles (itraconazole)
  • Topical: azoles, enilconazole for cattle, horse, dog. Miconazole for cats
  • Lime sulphur dip
  • NB: griseofulvin no longer licensed for horses
48
Q

Explain the use of malaseb shampoo in the treatment of dermatophytosis

A

Contains miconazole and chlorhexidine

49
Q

Describe the treatment of malassezia dermatitis

A
  • Treat primary cause
  • Reduce organism numbers, topical treatment very effective
  • Itraconazole if topical fails
  • May need regular treatment, commonly with malaseb, chlorhexidine, mirobex, mycozole, seleen
50
Q

Discuss the issues of dermatophytosis treatments

A
  • Topical therapy does not work as sole treatment
  • Little use for local therapy as spores elsewhere
  • Clipping coat may benefit long haired breeds
  • Environmental decontamination required: difficult, includes carpets, may need to repaint rooms
51
Q

Discuss the advantages and disadvantages of coat clipping for the management of dermatophytosis?

A
  • Physical removal of spores
  • May also spread spores
  • May damage skin allowing disease to establish itself more
52
Q

Identify the important zoonotic fungal skin infections

A
  • Ringworm

- Cryptococcus neoformans

53
Q

List the vesicular diseases of large animals and identify those that are notifiable

A
  • Notifiable: FMDV, vesicular stomatitis, swine vesicular disease, Bluetongue, Rinderpest
  • Not notifiable: Malignant catarrhal fever, mucosal disease, infectious bovine rhinotracheitis, bovine herpes mammilitis
54
Q

Describe the general clinical signs of vesicular disease

A
  • Vesicles and erosions/ulcers on muzzle, oral mucosa, tongue, udder, teats, coronary band (can affect horn and hoof growth)
  • May shed horns and hooves
  • Non-haired areas more affected
  • Often indistinguishable from one another
55
Q

What samples can be used for virus isolation of a vesicular disease?

A
  • Vesicular fluid
  • Vesicular tissue
  • Pharyngeal fluid
  • Whole blood
56
Q

Which samples can be used for RT-PCR of a vesicular disease?

A
  • Vesicular fluid
  • Vesicular tissue
  • Pharyngeal fluid
  • Whole blood
57
Q

Which samples can be used for ELISA of a vesicular disease?

A
  • Serum

- Milk

58
Q

Which samples can be used for EM +/- histopathology if suspicious of a vesicular disease?

A
  • Vesicular tissue

- PM tissue

59
Q

How is FMDV spread?

A
  • Vesicular fluid, saliva, milk, faces
  • Contaminated fomites
  • Airborne
60
Q

Briefly describe vesicular stomatitis

A
  • Never in UK
  • Cattle, pigs, horses
  • Motality moderate to low
  • Spread by biting insects
  • In people causes flu like symptoms, occasionally mucocutaneous vesicles and erosions
61
Q

Briefly describe swine vesicular disease

A
  • Pigs
  • Eradicated from UK in 1982, endemic in Italy
  • Mortality low, some loss of production
  • Spread by direct contact, fomites, infected meat products
  • Slower spread thn FMDV
62
Q

Compare the disease caused by Bluetongue between species

A
  • Affects sheep, cattle, deer, goats, camelids

- Sheep most severely affected, cattle are main mammalian reservoir and often clinically unaffected

63
Q

Describe the transmission and control of Bluetongue

A
  • Spread by Culicoides midges in late summer/autumn
  • UK free after vaccination programme
  • Still see in imported animals
64
Q

Describe the clinical signs of Bluetongue in sheep

A
  • Oral ulcers
  • Discharge of mucus and drooling from mouth and nose
  • Swelling of mouth, head and neck, and coronary band
  • Occasionally purpura, fever, lameness, breathing problems
65
Q

Which species are affected by Rinderpest?

A

Cattle, sheep, goats, camels, wild ruminants, pigs

66
Q

Describe the general control of notifiable viral diseases

A
  • Usually no treatment
  • slaughter and disposal of infected and in contacts
  • Quarantine/protection zone, movement restrictions, disinfection
  • +/- vaccination
  • Eradication programmes, surveillance programmes
  • Reporting of confirmed/suspected cases
67
Q

What virus causes malignant catarrhal fever (MCF)?

A

Herpesvirus

68
Q

What species are affected by MCF?

A

Cattle, deer, sheep are an asymptomatic reservoir

69
Q

What are the cutaneous signs of MCF?

A
  • Crusting of muzzle

- +/- exudative dermatitis of udder/teats, inner thighs

70
Q

What are the systemic signs of MCF?

A
  • Fever
  • Corneal opacity
  • Mucopurulent oculonasal discharge
71
Q

What virus causes Mucosal Disease (MD)?

A

Bovine viral diarrhoea virus (BVDV) - Pestivirus

72
Q

What species are affected by Mucosal Disease?

A

Cattle

73
Q

Describe the cutaneous signs of Mucosal Disease

A
  • Salivation

- Ulcers on mouth/muzzle

74
Q

Describe the systemic signs of Mucosal Disease

A
  • Fever, anorexia
  • Purulent discharge from eyes/nostrils
  • Diarrhoea
  • Thrombocytopaenia, haemorrhagic disease
75
Q

What agent causes Infectious Bovine Rhinotracheitis (IBR)?

A

Bovine Herpesvirus-1

76
Q

What species are affected by IBR?

A

Cattle

77
Q

What are the cutaneous signs of IBR?

A

Ulcers on muzzle

78
Q

Describe the systemic signs of IBR

A
  • Fever
  • Rhinitis, conjunctivitis, fever
  • +/- dyspnoea, cough
  • Venereal transmission
  • Abortion
79
Q

What agent causes bovine herpes mamillitis?

A

Bovine herpesvirus-1

80
Q

What are the clinical signs of bovine herpes mammillitis?

A
  • Ulcerative lesions of teats and udder
  • Decreased milk production
  • Mastitis
81
Q

Describe the spread of bovine herpes mammillitis

A
  • Spread by insects and carrier cattle
  • Rapid spread, high morbidity
  • Mainly autumn and winter
82
Q

What are the consequences of bovine herpes mammillitis?

A
  • Severe economic losses
  • Difficult to control
  • Zoonotic
  • Often persistently infected herds
83
Q

How many types of bovine papillomavirus are there and which are important in the skin?

A
  • 6 types

- I, II, III, V and VI important in skin

84
Q

Describe the significance of cutaneous papilloma virus infection in cattle

A
  • Highly prevalent in UK
  • 50% of cattle have lesions
  • Rarely cause problems, unless on teats or genitals
  • May become secondarily infected
  • Unsightly, may be problem on show animals
85
Q

Describe the appearance of cutaneous bovine papilloma virus lesions

A
  • Can appear very variably
  • Large cauliflower like masses on head, neck and shoulders
  • Flat wide-based warts
  • Pedunculated masses
  • Aka Angleberries, cutaneous warts
86
Q

How is cutaneous bovine papilloma virus spread?

A
  • Warts contain large amounts of infectious material

- Trauma on fence posts, halters, contaminated tagging equipment leads to transmission

87
Q

Describe the treatment for cutaneous bovine papilloma virus

A
  • Treatment not usually required, spontaneous regression
  • Surgical removal if pedunculated
  • Disinfect stalls, fence posts and other environmental reservoirs
  • Autogenous vaccine can be used, but ineffective against existing warts
88
Q

What is the significance of bovine papilloma virus for other large mammals?

A
  • BPV I and II can induce sarcomas and fibrosarcomas in other mammals
  • Equine sarcoids for example
  • Transmission unclear, may be flies or contaminated tack
  • Causes warts, or aural plaques
  • IN young horses is self limiting, if over 1yo will persist
  • Is only known example of natural cross-species infection by a papillomavirus, others are very species specific
89
Q

Describe the clinical signs of classical swine fever (identical to African Swine fever)

A
  • Fever, constipation/bloating
  • Conjunctivitis
  • Blotchy discolouration of skin
  • Abortion,still birth, weak litters
  • Hindlimb weakness
  • Nervous signs
90
Q

Describe the spread of classical swine fever

A
  • Recovered pigs excrete virus for long periods, can be active for months
  • Spread by eating infected pork or pork products
  • Movement and fomites
91
Q

What are the differential diagnoses for classical swine fever?

A
  • Post-weaning multisystemic wasting disease
  • Porcine dermatitis nephropathy syndrome (blotchy skin)
  • Circovirus
  • Ubiquitous
92
Q

Describe the clinical signs of congenital infection, and in ewes with border disease

A
  • Hairy shakers/fuzzy lamb disease
  • Small, weak lambs
  • Abnormally hairy birth coat
  • Tremor of skeletal muscles
  • Leads to death
  • In ewes causes abortion/still birth
93
Q

How is Border disease spread?

A
  • If infected in first half of gestation = persistently infected sheep
  • These act as source of infection for pregnant ewes
94
Q

Outline the control of Border disease

A
  • Prevention of exposure of pregnant ewes to persistently infected sheep
  • No vaccine
95
Q

Describe the dermatological signs of Pox viruses

A
  • Macules
  • Papules
  • Vesicles
  • Pustules
  • Crusts
96
Q

Give examples of pox viruses and briefly describe each

A
  • Cowpox: rarely in cattle, reservoir in rodents, more frequently seen in cats
  • Horsepox: rare in Europe
  • Swinepox: transmitted by sucking lice, mild self-limiting disease
97
Q

Briefly describe sheep and goat pox (significance and clinical signs)

A
  • Notifiable, not present in UK

- Papules and crusts on eyes, nose, mouth, udder and teats, non-woolled skin

98
Q

What agent causes lumpy skin disease?

A

Capropoxvirus

99
Q

Describe the distribution of lumpy skin disease globally

A

Moved from Africa/Asia to Middle East to Eastern Europe, risk of introduction to UK, isolated case in Ireland. Notifiable

100
Q

Describe the transmission of lumpy skin disease

A
  • Transmission by biting insects/ticks

- More common in summer

Dermatology 2 (23 decks)

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