Fungal Jungle! Flashcards
What is fungus?
- It can be parasitic or free-living in the environment.
- Most are multi-cellular (except yeasts)
Mycology
The study of fungi
Identifying fungi (4)
- Description growth
- Description of color
- Description of sexual spores
- Description of asexual spores
Hyphae
Hint: Fairy tree
Filament or branch from which the fungus grows.
(Hyphae tips can grow either from mitosis or meiosis depending on the type of fungus)
Mycelium
Hint: Big fairy tree
The intertwined mass of hyphae that forms the mold colony
Arthrospores
- Asexual
- Thick walled spores formed by hyphal septation.
- Are able to survive harsh conditions.
Conidia
Hint: Outside the fairy tree
Asexual spores borne externally on hyphae (branches)
Yeast
Hint: “Hey buddie”
- No hyphae
- Multiply by budding
Pathogenic Fungi Groups: Fungi Imperfecta (4)
Important species include:
- Dermatopytes: Microsporum & Trichophyton.
- Histoplasma
- Candida
- Aspergillus
Aspergillus
Hint: Common throughout the world
- Usually causes disease in birds, but can for any species.
- Germ. Shep. are at high risk.
Symptoms:
- Severe nasal & sinus infections.
- Can cause pneumonia
- Very difficult to treat
Dermatophytes
Hint: “ringworm”
- Keratinophilic fungi that invade hair, nails, & superficial skin layers.
- Lesions are pruritic & cause crusty skin and hair loss.
- Different presentations in diff. species.
- Often contagious and spores are hard to kill!
What are the 4 pathogenic fungi groups?
- Mushrooms
- Cup fungi
- Molds
- Fungi imperfecti - no sexual stage
Dermatophytes - How the fungi disease invades (3)
- Fungi enter hair follicles by growing down hair shafts (gets into the shaft).
- Invades keratin (toughest layer of the skin).
- Arthospores form as hair grows upward.
How to diagnose dermatophytes? (3)
- Woods black lamp.
- Florescent hyphae in hair shafts.
- Only some strains of fungus will be (+)!!! - Direct Microscope Eval.
- KOH prep
- Consists of prep of specimen using Potassium “P” Hydroxide “OH” - Dermatophytes Test Medium.
- “DTM”
How do you preform a KOH prep?
- Arthrospores grow on the outside of the hair shaft but cannot normally be seen.
- Pluck a few hairs from the PERIHERY of the lesion (not on!).
- Place on slide w/1-2 drops of 10% KOH & add cover slip.
- Warm for 2-10min.
- Arthrospores visible along a hair shaft.
Dermatophyte Test Medium (DTM)
Medium: (4)
Type of test?
How does it work?
Reliability?
How to prep?
- Selective & differential
- Only grows fungi & has red color change in 7d.
- Most reliable test.
- Area/lesion should be cleaned with alc. then hairs plucked from the EDGE of the lesion.
Mushrooms:
What is their importance?
What are the causes if exposed? (4)
- Medically important due to toxicity of ingestion.
- If ingested, it can cause: vomiting/diarrhea, neurologic signs, liver/kidney failure, & death.
Who is at risk of dermatophytes as a zoonotic disease?
- Children
- Damaged skin
- Animals (esp cats!) can be asymptomatic carriers.
Yeasts: Malassezia
Species of yeast?
Where is it likely to occur on a patient?
Hint: this is a common cause of dermatitis
- Species of lipophilic yeast.
- Skin folds, ears of allergic dogs
Malassezia (yeast) diagnosis:
Tape prep (3)
- Using a small strip of transparent tape, lay it on the skin lesion and press lightly.
- Apply a drop of blue from Diff-Quik stain set.
- Lay sample side down on the slide.
Malassezia (yeast) diagnosis:
Direct smear (6)
- Moisten a sterile swab w/sterile saline.
- Swab area of interest (skin lesion, vagina, ear).
- Roll swab gently onto a microscope slide.
- After airdrying, heat fix using gram stain.
- Stain w/Gram Stain or Dif Quik.
- Observe!
Therapy for Malassezia (3)
- Anti-fungal agents
- Treat bacterial infections if present.
- Treat underlying cause (allergies, skin care, surgery)
What dog breeds are especially at risk for Malassezia (yeast)?
- Westies
- Cocker spaniels
- Bassets
Cryptococcus
How does it transport to the next host?
Hint: Construction workers are at risk!
It is found in soil and the feces of pigeons.
It can be spread by inhalation or open wounds.
Who is at risk for the nasal form of Cryptococcus?
Hint: fuzzy ears
Cats and koala bears
Cryptococcus diagnosis methods (4)
- Cytology (most common)
- Serology
- Antigen
- Culture
Cryptococcus diagnosis:
Cytology
- Prolific in tissues
- Characteristic thick capsule when stained
- India ink or cotton blue
What is the therapy for Cryptococcus?
How long?
A combo of:
1. Debulking Sx when possible
2. Long-term medication
- Azoles (anti fungal agent)
- 3-12 months or more
- Relapse is common
What are Dimorphic pathogens?
Fungi that can exist in the form of both
mold and yeast (yikes!)
Dimorphic pathogen:
Coccidiodes, what is it?
Hint: S S Z
It is a soil fungus of lower Sonoran life Zone
What happens to dog when they contract Coccidiodes?
Hint: This can sometimes present as pneumonia because its an airborne disease.
Dogs commonly get lung or bone forms of disease from inhaling arthroconidia
Howdo cats contract Coccidiodes? In what form do they get it?
Cats commonly get a skin form of the disease from puncture wound contaminations
What is the therapy for Coccidioidomycosis?
- Ketoconazole is effective & prevents disease from becoming systematic.
- Bone & systemic forms MUST be treated or death is possible.
T/F: Dogs w respiratory form of Coccidioidomycosis will recover w/o treatment
True! At least in most cases
T/F: Fungal infections are usually slow growing
True
T/F: Fungal infections do not have an intense inflammatory response from the body
False. They will cause an intense inflammatory response from the body!
T/F: Cellular immunity is needed to clear fungal infections
True! The body needs strong, well programmed, and smart T-Cells. Fungal diseases can be very hard on young animals with building immune systems and immune compromised.
T/F: Most fungal infections are not directly contagious, except dermatophytes
True! Dermatophytes is also a zoonotic disease
T/F: Spores are not very resistant to disinfection and decontamination
False. Spores are very resistant! 10% bleach is usually effective to disinfect formites
T/F: Most fungal infections can be treated fast and easily
False! Most require weeks to months of therapy to resolve them
