Fungal Disease - Importance and Examples

Question 1

What is fungi?

Answer 1

Eukaryotic organism
Yeast, mould or both

Question 2

Yeast

Answer 2

Unicellular

Question 3

Mould

Answer 3

Multicellular-filamentous hyphae

Question 4

How do fungi digest food?

Answer 4

Externally
Absorb nutrients through cell wall

Question 5

What is fungi cell wall made of?

Answer 5

Chitin and other polysaccharides
Complex

Question 6

How do fungi reproduce?

Answer 6

Spore formation
* Asexual +/- sexual

Question 7

Saprophytic meaning

Answer 7

Obtain food by absorbing dissolved organic material

Question 8

Which fungi are pathogenic?

Answer 8

Dermatophytes (Cause ringworm)
NEVER a commensal

Question 9

How are fungi classified?

Answer 9

Based on normal habitat

Question 10

Geophilic

Answer 10

Found in soil/environment
Only occasionally infect animals/man

Question 11

Zoophilic

Answer 11

Found on animals
Occasionally transmitted to man

Question 12

Anthropophilic

Answer 12

Found on man
Occasionally transmitted to animals

Question 13

How do fungi cause disease?

Answer 13

Mycosis - Tissue invasion
Mycotoxicosis - Toxin production
Induction of hypersensitivity

Question 14

Types of Mycosis

Answer 14

Superficial mycoses
Subcutaneous (deep) mycoses
Systemic Mycoses

Question 15

Site of superficial mycoses

Answer 15

Epidermis
Keratinised structures
Mucous membranes

Question 16

Site of subcutaneous mycoses

Answer 16

Subcutaneous tissue

Question 17

Site of systemic mycoses

Answer 17

Respiratory system
Digestive system
Other organ systems

Question 18

What is mycosis predisposed by?

Answer 18

• Immunological deficits
• Immunosuppression
  ○ Including corticosteroid treatment
• Immaturity
• Ageing
• Malnutrition
• Prolonged antibiotic therapy
• Exposure to heavy challenge of fungal spores
• Traumatised tissues
• Persistent moisture on skin surface

Question 19

Types of superficial mycoses

Answer 19

Dermatophytosis - caused by dermatophytes
Dermatomycosis - caused by non-dermatophytes

Question 20

Dermatophytosis

Answer 20

Causes ringworm
* Microsporum spp.
* Trichophyton spp.

Pathogenic fungi
Highly contagious

Mainly infect cat, cattle and horses
Can also infect dogs, goats, pigs, sheep

Question 21

Dermatomycosis

Answer 21

Non-dermatophytic fungi
* Malassezia
* Candida

Normal skin commensals that cause opportunistic infections
Not contagious

Question 22

Malassezia dermatitis

Answer 22

Type of dermatomycosis
Common dysbiosis of dogs (sometimes cats)
Often occurring secondary to other skin disease

Question 23

Candidiasis

Answer 23

Type of dermatomycosis
Candida albicans

Opportunistic infection related to immunosuppression

E.g. Mycotic stomatitis - puppies, kittens, foals
E.g. Thrush of oesophagus/crop - young chickens

Question 24

Subcutaneous (deep) Mycosis

Answer 24

Localised invasion of dermis/subcutis
Often follows foreign body penetration
Chronic localised lesions

Question 25

Chronomycosis

Answer 25

Caused by pigmented fungus

Question 26

Hyalohyphomycosis

Answer 26

Caused by non-pigmented fungus

Question 27

Mycetoma

Answer 27

○ Organism in granules/grains within lesion
○ Associated with swelling and draining sinus

Question 28

Types of mycetoma

Answer 28

Eumycotic mycetoma
Actinomycotic mycetoma

Question 29

Eumycotic mycetoma

Answer 29

Organism is fungal

Question 30

Actinomycotic mycetoma

Answer 30

Organism is bacterial

Question 31

Pseudomycetomas

Answer 31

Different granule formation to mycetoma
Can be dermatophytic or bacterial

Question 32

Systemic Mycosis

Answer 32

Organism initially inhaled then spreads to internal organs
E.g Cryptococcosis

Question 33

Cryptococcosis Issues

Answer 33

Cats :
Respiratory, cutaneous, neural/ocular infections
Dogs:
Disseminated disease with neural/ocular signs
Cattle (rare):
Mastitis, nasal granulomas
Horses (rare):
Nasal granulomas/sinusitis, cutaneous lesions, pneumonia, meningo-encephalomyelitis, abortion
Can affect man
But not usually contracted from an animal

Question 34

Cryptococcosis Examples

Answer 34

C. neoformans
C. gait
Associated with pigeon droppings which contaminate soil
Associated with decaying vegetation

Question 35

Mycotoxicosis

Answer 35

Toxin production by fungi
Mostly from fungi on crops, pasture or stored feed
Example species:
○ Penicillium
○ Aspergillus (-> aflatoxicosis)
○ Fusarium
○ Claviceps (-> ergotism)

wide range of clinical signs dependent on toxin

Question 36

Mycotoxicosis effects