Microbial skin disease Flashcards
Bacterial, fungal, viral and protozoal skin disease
1
Q
Outline the management of caseous lymphadenitis
A
Remove positive individuals
2
Q
Outline the management of greasy pig disease
A
- Treat with systemic antibiotics
- Topical antibacterial wash
- Fluids (to treat toxic liver/kidney damage)
3
Q
Which antibiotics are effective against greasy pig disease?
A
Sensitive to most antibacterials, incl. penicillins
4
Q
Outline the management of erysipelas
A
- Penicillin treatment
- Vaccine available
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
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
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
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
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
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
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
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
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
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)
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)
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
17
Q
What skin conditions are guinea pigs prone to?
A
- Dermatophytosis
- Mange
- Trichofolliculoma
18
Q
What are the 3 most common yeast/yeast like cutaneous infectious agents?
A
- Candida
- Malassezia
- Trichosporon
19
Q
What group of individuals are most susceptible to Candida infections?
A
Immunocompromised hosts
20
Q
What species of Malassezia is most commonly isolated from the skin of mammals and birds?
A
M. pachydermatitis
21
Q
List the breeds that have higher skin levels of M. pachydermatitis
A
- Bassett hounds
- Daschunds
- Cocker spaniels
- WHWT
22
Q
What conditions favour infection with M. pachydermatitis?
A
- Concurrent infection with Staphylococcus pseudintermedius
- Hot humid weather
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
24
Q
Describe the 2 types of Malassezia dermatitis
A
- Scaly: dry seborrhoea, dandruff, seborrhoea sicca
- Greasy: more common, seborrhoea oleosa
25
How are deep mycoses acquired?
- Direct inoculation traumatic implantation)
- Ingestion
- Inhalation or spores
26
What are the 2 subgroups of deep mycoses?
- Subcutaneous
| - Systemic
27
Outline deep mycoses in cats
- Most common is Cryptococcus neoformans
| - Cats with FIVE increased risk, more severe dsiease
28
Identify reservoirs for dermatophytosis
- Infected animals/contaminated environment
- Can survive in environment for many months
- Fomite spread
- Catteries/stables.yards carry high outbreak risk
29
Describe the 2 groups of carriers of dermatophytosis
1: Culture positive (dogs or) cats with subtle active infections
2: Culture positive (dogs or) cats with no active infection = carriers
30
Outline the control of dermatophytosis
- Self limiting if healthy, effective immune response
| - Vaccine available
31
Describe the equine epidemiology of dermatophytosis
- Common, esp. in young horses
- Subsequent exposure leads to less severe signs
- Common sits of infection around tack
32
Explain the pathogenesis of Malassezia dermatitis
- 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
33
Describe ringworm pathology
- 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
34
Describe the common clinical signs of Malassezia dermatitis
- 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
35
Describe the appearance of Cryptococcus neoformans infections
Ulcerated skin lesions
36
Outline the methods used for the diagnosis of dermatophytosis
- 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)
37
Describe the method for fungla culture
- 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
38
What is contained in Sabouraud's media?
Contains phenol red pH indicator, cyclohexamide to inhibit growth of other fungi and gentamycin and chlorotetracycline to inhibit bacterial growth
39
What media can be used for sporulation of dermatophytes to facilitate speciation?
- RSB
| - Contains bromothymol blue indicator and chloramphenicol instead of gentamycin
40
What is the function of dermatophyte arthrospores?
Required for transmission
41
What are conidia?
Asexual, non-motile spores of a fungus and normally stained with lactophenol cotton blue
42
Explain how dermatophytes can be differentiated from one another
- 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
How is Malassezia dermatitis diagnosed?
- dermatological signs
- Acetate tape test (ancilliary diagnostic aids)
- Impression smear
- Fungal culture may be needed
44
Describe the diagnoses of deep mycoses
- 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
Outline the management of dermatophytosis
- Vaccination
- Licensed antifungal agents
- Malaseb shampoo
- Spontaneous resoution in cattle and horses, rarely treated
46
What drugs are commonly used in the treatment of dermatophytosis in rabbits?
- Topical miconazole or clotrimazole
| - Oral itraconazole or griseofulvin usually effective
47
Which antifungal drugs are licensed for the treatment of dermatophytosis?
- Systemic: azoles (itraconazole)
- Topical: azoles, enilconazole for cattle, horse, dog. Miconazole for cats
- Lime sulphur dip
- NB: griseofulvin no longer licensed for horses
48
Explain the use of malaseb shampoo in the treatment of dermatophytosis
Contains miconazole and chlorhexidine
49
Describe the treatment of malassezia dermatitis
- 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
Discuss the issues of dermatophytosis treatments
- 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
Discuss the advantages and disadvantages of coat clipping for the management of dermatophytosis?
- Physical removal of spores
- May also spread spores
- May damage skin allowing disease to establish itself more
52
Identify the important zoonotic fungal skin infections
- Ringworm
| - Cryptococcus neoformans
53
List the vesicular diseases of large animals and identify those that are notifiable
- Notifiable: FMDV, vesicular stomatitis, swine vesicular disease, Bluetongue, Rinderpest
- Not notifiable: Malignant catarrhal fever, mucosal disease, infectious bovine rhinotracheitis, bovine herpes mammilitis
54
Describe the general clinical signs of vesicular disease
- 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
What samples can be used for virus isolation of a vesicular disease?
- Vesicular fluid
- Vesicular tissue
- Pharyngeal fluid
- Whole blood
56
Which samples can be used for RT-PCR of a vesicular disease?
- Vesicular fluid
- Vesicular tissue
- Pharyngeal fluid
- Whole blood
57
Which samples can be used for ELISA of a vesicular disease?
- Serum
| - Milk
58
Which samples can be used for EM +/- histopathology if suspicious of a vesicular disease?
- Vesicular tissue
| - PM tissue
59
How is FMDV spread?
- Vesicular fluid, saliva, milk, faces
- Contaminated fomites
- Airborne
60
Briefly describe vesicular stomatitis
- 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
Briefly describe swine vesicular disease
- 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
Compare the disease caused by Bluetongue between species
- Affects sheep, cattle, deer, goats, camelids
| - Sheep most severely affected, cattle are main mammalian reservoir and often clinically unaffected
63
Describe the transmission and control of Bluetongue
- Spread by Culicoides midges in late summer/autumn
- UK free after vaccination programme
- Still see in imported animals
64
Describe the clinical signs of Bluetongue in sheep
- 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
Which species are affected by Rinderpest?
Cattle, sheep, goats, camels, wild ruminants, pigs
66
Describe the general control of notifiable viral diseases
- 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
What virus causes malignant catarrhal fever (MCF)?
Herpesvirus
68
What species are affected by MCF?
Cattle, deer, sheep are an asymptomatic reservoir
69
What are the cutaneous signs of MCF?
- Crusting of muzzle
| - +/- exudative dermatitis of udder/teats, inner thighs
70
What are the systemic signs of MCF?
- Fever
- Corneal opacity
- Mucopurulent oculonasal discharge
71
What virus causes Mucosal Disease (MD)?
Bovine viral diarrhoea virus (BVDV) - Pestivirus
72
What species are affected by Mucosal Disease?
Cattle
73
Describe the cutaneous signs of Mucosal Disease
- Salivation
| - Ulcers on mouth/muzzle
74
Describe the systemic signs of Mucosal Disease
- Fever, anorexia
- Purulent discharge from eyes/nostrils
- Diarrhoea
- Thrombocytopaenia, haemorrhagic disease
75
What agent causes Infectious Bovine Rhinotracheitis (IBR)?
Bovine Herpesvirus-1
76
What species are affected by IBR?
Cattle
77
What are the cutaneous signs of IBR?
Ulcers on muzzle
78
Describe the systemic signs of IBR
- Fever
- Rhinitis, conjunctivitis, fever
- +/- dyspnoea, cough
- Venereal transmission
- Abortion
79
What agent causes bovine herpes mamillitis?
Bovine herpesvirus-1
80
What are the clinical signs of bovine herpes mammillitis?
- Ulcerative lesions of teats and udder
- Decreased milk production
- Mastitis
81
Describe the spread of bovine herpes mammillitis
- Spread by insects and carrier cattle
- Rapid spread, high morbidity
- Mainly autumn and winter
82
What are the consequences of bovine herpes mammillitis?
- Severe economic losses
- Difficult to control
- Zoonotic
- Often persistently infected herds
83
How many types of bovine papillomavirus are there and which are important in the skin?
- 6 types
| - I, II, III, V and VI important in skin
84
Describe the significance of cutaneous papilloma virus infection in cattle
- 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
Describe the appearance of cutaneous bovine papilloma virus lesions
- Can appear very variably
- Large cauliflower like masses on head, neck and shoulders
- Flat wide-based warts
- Pedunculated masses
- Aka Angleberries, cutaneous warts
86
How is cutaneous bovine papilloma virus spread?
- Warts contain large amounts of infectious material
| - Trauma on fence posts, halters, contaminated tagging equipment leads to transmission
87
Describe the treatment for cutaneous bovine papilloma virus
- 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
What is the significance of bovine papilloma virus for other large mammals?
- 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
Describe the clinical signs of classical swine fever (identical to African Swine fever)
- Fever, constipation/bloating
- Conjunctivitis
- Blotchy discolouration of skin
- Abortion,still birth, weak litters
- Hindlimb weakness
- Nervous signs
90
Describe the spread of classical swine fever
- Recovered pigs excrete virus for long periods, can be active for months
- Spread by eating infected pork or pork products
- Movement and fomites
91
What are the differential diagnoses for classical swine fever?
- Post-weaning multisystemic wasting disease
- Porcine dermatitis nephropathy syndrome (blotchy skin)
- Circovirus
- Ubiquitous
92
Describe the clinical signs of congenital infection, and in ewes with border disease
- 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
How is Border disease spread?
- If infected in first half of gestation = persistently infected sheep
- These act as source of infection for pregnant ewes
94
Outline the control of Border disease
- Prevention of exposure of pregnant ewes to persistently infected sheep
- No vaccine
95
Describe the dermatological signs of Pox viruses
- Macules
- Papules
- Vesicles
- Pustules
- Crusts
96
Give examples of pox viruses and briefly describe each
- 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
Briefly describe sheep and goat pox (significance and clinical signs)
- Notifiable, not present in UK
| - Papules and crusts on eyes, nose, mouth, udder and teats, non-woolled skin
98
What agent causes lumpy skin disease?
Capropoxvirus
99
Describe the distribution of lumpy skin disease globally
Moved from Africa/Asia to Middle East to Eastern Europe, risk of introduction to UK, isolated case in Ireland. Notifiable
100
Describe the transmission of lumpy skin disease
- Transmission by biting insects/ticks
| - More common in summer
