Week 2 - Fungal disease and other pathology Flashcards
What are the different types of fungal spore?
Arthrospores - lots of cells make up a septate hypha which breaks up into the seperate cells. (produced by dermatophytes) Conidiospores - often produced at the ends of hyphae, they can be unicellular or multicellular. Spores detach from the structure when they are mature.
What is the difference between mycoses and mycotoxicoses?
Mycoses is disease caused by a fungus invading and growing in tissue whereas mycotoxicoses is disease caused by production of a fungal toxin.
What are the types of yeast infection that can affect animals?
Cryptococcosis Candidiosis Malassexia pachydermatitis
What is a common presentation of crytococcosis that may be seen in SA practice and how is this disease contracted?
Frequently associated with the tip of the nose in cats. It is associated with old pidgeon droppings.
What type of budding is seen with candida?
Budding on a broad base
What are the filamentous fungi causing disease in animals?
Saprolegniosis - fish
Mucor - causing mycotic rumenitis
Aspergillus
Dermatophytes
Which genera of fungus cause ringworm?
Microsporum, Trichophyton and Epidermophyton*
*(rarely seen in animals)
What are the most common species found in ringworm infections of the dog in the UK? How does this presentation vary?
*Microsporum canis *and *Trichophyton **mentagrophytes *are the most common in the UK. This does vary depending on first opinion vs. refferral as *T. mentag. *is seen more at referral.
Describe the pathogenesis of dermatophytosis, when is disease most likely to be long standing?
Infection is acquired by contact. Arthrospores adhere to the stratum conreum cells and hyphae invade the SC by aid of keratinases. Anagen hairs are invaded but mitotically active cells are not usually affected. The host produces an inflammatory response and this normally resolves disease in 1-3 months unless the animal is immunocompromised in some way.
What breed dispositions are there for dermatophytosis?
- M. canis *often infects Yorkshire Terriers
- Trichophyton *spp. often infect Jack Russel Terriers
Why is it important to investigate dermatophytosis and how is this achieved?
It is zoonotic!
Microscopy - spores not always seen, does not rule out
Fluoresence microscopy - calcafluor dye, however UV microscopes wont be accessible in practice
Wood’s Lamp - apple green fluorescence (does not rule out)
Culture in a GOOD lab is best.
Biopsy can be used.
What are some of the clinical signs of *Malassezia pachydermatitis *infection?
Erythema, alopecia and scaling
Greasy exudate
Ventral neck, interdigital skin, axillae and groin comonnly affected.
What might be a good tx protocol for *M. canis *in a CAT?
Oral itraconazole in 3 cycles of 1 week on and 1 week off.
In conjunction use Malaseb (chlorhexidine + myconazole) shampoo.
Treat the environment!
How do imidazole antifungals achieve their effect?
They inhibit ergesterol synthesis which is a normal component of the fungal cell wall.
How can the contrast be adjusted on the microscope? In what circumstances is this done?
Increase contrast by moving condenser stage down. Use at lower magnification. At higher magnification a higher condenser stage with more light is needed.
What causes nuclear streaking on a cytology sample?
Nuclear streaking is an indication of damage to neutrophils. It is formed of damaged chromatin.
How might cell populations vary between superficial and deep pyodermas?
Superficial pyodermas are more likely to have neutrophils and deep pyodermas are likely to have increased mononucleur cells.
What are the 4 main reasons for hair loss?
- Trauma/self trauma
- Inflammatory disease
- Primary
- Bystander
- Endocrine problems
- Genetic disorder/follicular dysplasia
