6. Fungal Pathogens (Tesse)

Question 1

Fungi are ___ pathogens

Answer 1

opportunistic

Question 2

Why are fungal infections relatively rare in mammals

Answer 2

most fungi grow best below the body temperature of endotherms

Question 3

What species are fungal infections common in

Answer 3

ectoderms (plants, insects, fish, reptiles, amphibians)

Question 4

In mammals, fungi are typically considered either:

Answer 4

commensals (disease happens in states of immunosuppression) or environmentally acquired (disease follows exposure to large inoculum)

Question 5

What are the three steps of fungal pathogenesis

Answer 5

1. tissue invasion (ie mycosis)
2. Toxin production (ie mycotoxicosis)
3. hypersensitivity

Question 6

what is an example of mycotoxicosis

Answer 6

aflatoxicosis, fusariotoxicosis, ergotism

Question 7

What are the three types of fungal disease forms

Answer 7

1. cutaneous mycoses
2. subcutaneous mycoses
3. systemic mycoses

Question 8

What are the two veterinary dermatophytes?

Answer 8

Microsporum and Trichophyton

Question 9

What do dermatophytes utilize for growth

Answer 9

keratin

Question 10

what is the infective agent of dermatophytes

Answer 10

arthrospores, which facilliate transmission between hosts and can remain viable on shed hair and skin for at least 6-12 months

Question 11

are arthrospores sexual or asexual

Answer 11

asexual

Question 12

Where are dermatophytes found?

Answer 12

geophilic, zoophilic, anthropohilic

Question 13

what does geophilic mean

Answer 13

free living saprophytes in the soil

Question 14

what does zoophilic mean

Answer 14

adapted to survival in animal host skin

Question 15

what does anthropophilic mean

Answer 15

adapted to survival in human host skin

Question 16

Dermatophyte transmission

Answer 16

close contact, direct contact with fomites, fleas (mechanical vector)

Question 17

what does infection by dermatophytes depend on

Answer 17

the hosts state - immunocompetence, skin conditions, nutritional state

Question 18

What are the two dermatophyte species that affect cats and dogs

Answer 18

Microsporum canis, Trichophyton mentagrophytes

Question 19

What are the two dermatophyte species that affect horses

Answer 19

Trichophyton equinum, Trichophyton mentagrophytes

Question 20

what dermatophyte affects cattle and sheep

Answer 20

Trichophyton verrucosum

Question 21

what dermatophyte affects pigs

Answer 21

Microsporum nanum

Question 22

What species causes >75% of dermatophyte infections in cats and dogs

Answer 22

Microsporum canis

Question 23

What is Microsporum canis infection more commonly known as

Answer 23

ringworm

Question 24

Ringworm is characterized by ____ in dogs and ____ in cats

Answer 24

nodular dermatophytosis in dogs, dermatophytic mycetoma in cats

Question 25

How should you collect dermatophyte samples

Answer 25

pluck hair from the edge of lesions ( fungi more likely to be in base of hair), scrape crusts, biopsy kerions and mycetomas. WEAR GLOVES

Question 26

How can you visualize Microsporum canis in house?

Answer 26

- Woods UV lamps as a significant proportion is fluorescent - trichograms/KOH wet mount to see arthrospores -fungal culture (Gold standard) -histo

Question 27

when is treatment of dermatophyte infections strongly recommended?

Answer 27

for multianimal households or with immunocompromised humans

Question 28

Where are Candida spp. commonly found

Answer 28

common in environment

Question 29

What are the three main yeast and yeast like fungi

Answer 29

Candida, Malassezia, Cryptococcus

Question 30

Where is Malassezia pachydermatis found

Answer 30

on the skin of mammals and birds, localized to areas with sebaceous glands

Question 31

where is cryptococcus neoformans found

Answer 31

droppings of pigeons

Question 32

where is cryptococcus gatti found

Answer 32

on trees

Question 33

T/f: there is no zoonotic risk of cryptococcus infection via contact with an infected animal

Answer 33

true

Question 34

Avian crop thrush is caused by

Answer 34

candida albicans

Question 35

what species is particularly susceptible to oral candidiasis

Answer 35

young birds

Question 36

t/f avian crop thrush typically only affects a small portion of a flock

Answer 36

false. its usually a large proportion

Question 37

the clinical signs of avian crop thrush are

Answer 37

nonspecific

Question 38

Candida albicans infection in birds causes gross lesions of>

Answer 38

raised, focal thickenings in mucosa of GIT (avian crop thrush)

Question 39

What is the yeast like fungi that causes superficial infections in warm, moist anatomic sites

Answer 39

Malassezia pachydermatis - a normal flora of the ear canal of dogs and cats

Question 40

Malassezia pachydermatis is a normal commensal to which body part of dogs and cats

Answer 40

ear canal

Question 41

What is the most common systemic mycosis of cats

Answer 41

cryptococcosis

Question 42

what is the incubation period of cryptococcosis in cats

Answer 42

2-13 months

Question 43

How does cryptococcosis present in cats

Answer 43

upper resp signs - sneezing, ,polyp like masses on nose hematogenous spread with possible CNS involvement

Question 44

What is the best method for diagnosing yeast and yeast-like fungi

Answer 44

cytology (exudates, impression smears, tape preps, skin scrapings, biopsies)

Question 45

What causes brooder pneumonia in young chickens

Answer 45

Aspergillosis

Question 46

how are mature birds infected by aspergillus spp

Answer 46

inhalation of spore laden dust

Question 47

Guttural pouch mycosis in horses is caused by ______

Answer 47

Aspergillus fumigatus

Question 48

Mycotic abortion in cattle is caused by

Answer 48

Aspergillosis

Question 49

Aspergillosis can present as either a ____ form or a _____ form in cats and dogs

Answer 49

nasal, disseminated

Question 50

What species of aspergillus produces osteolytic toxins that can destroy nasal turbinates in cats and dogs

Answer 50

A.fumigatus

Question 51

Dimorphic fungi undergo their yeast phase at ____ C and their mold phase at ____ c

Answer 51

Yeast phase at 35-37⁰C Mold phase at ≤ 25⁰C

Question 52

Where are dimorphic fungi found

Answer 52

in the environment

Question 53

Blastomyces dermatitidis associated with

Answer 53

recent excavation

Question 54

Coccidoides immitis associated with

Answer 54

dust storms

Question 55

Histoplasma capsulatum associated with

Answer 55

bat/bird feces

Question 56

Sporothrix schenckii associated with

Answer 56

traumatic inoculation

Question 57

Why are animals important to human health relating to dimorphic fungi

Answer 57

they act as sentinels to disease

Question 58

Where is Coccidioides immitis located

Answer 58

southwestern USA

Question 59

blastomyces dermatitidis geographic location

Answer 59

eastern US and canada

Question 60

Histoplasma capsulatum geographic location

Answer 60

US and Canada (mideastern)

Question 61

Blastomyces dermatitidis pathogenesis

Answer 61

inhalation -> incubation period for 5-12 weeks -> seed in lungs -> hematogenous spread -> systemic signs

Question 62

What are the clinical signs of Blastomyces dermatitidis

Answer 62

variable: low grade for days to weeks to months. Respiratory (cough, dyspnea), lymphadenopathy, occular lesions, cutaneous lesions, lameness and neurologic signs. Also non-specific signs

Question 63

Pathogenesis: Coccidioides immitis

Answer 63

dust storm leads to Arthroconidia disarticulation -> inhalation, spores land in bronchioles -> enlarge into spherules -> spherules mature-> mature spherules rupture ->inflammation and tissue damage

Question 64

What is Coccidioides immitis infection known as

Answer 64

valley fever

Question 65

What are the clinical signs of coccidioides immitis

Answer 65

nonspecific - fever, lethargy, inappetance, weightloss

Question 66

What is the most important question to ask to determine if a dog may have valley fever

Answer 66

Travel history!

Question 67

Histoplasma capsulatum disease pattern

Answer 67

disseminated

Question 68

H. capsulatum in cats

Answer 68

vague and non-specific

Question 69

H. capsulatum in dogs

Answer 69

nonspecific and diarrhea most common, due to predilection for intestines

Question 70

in dogs, pulmonary histoplasmosis may be _____

Answer 70

self-limiting

Question 71

what is recommended to prevent H.capsulatum dissemination in dogs?

Answer 71

Early therapy with antifungals

Question 72

Sporothrix schenckii most commonly presents as ______ disease

Answer 72

lymphocutaneous disease

Question 73

How does S. schenckii develop

Answer 73

damage to skin from contaminated plants

Question 74

is Sporothrix zoonotic?

Answer 74

yes: contact from infected animal lesions or discharge

Question 75

What should you NEVER do with pathogenic yeast or yeast-like fungi (think of DR Zachar's resp path notes!!)

Answer 75

SEND FOR CULTURE! These are zoonotic pathogens of high risk to the humans doing the culturing.

Question 76

Opportunistic fungal pathogens are inherently of ____ virulence and disease

Answer 76

low

Question 77

what does infection by an opportunistic fungal pathogen depend on

Answer 77

diminished host defenses or traumatic inoculation

Question 78

Pythium insidiosum geographic location

Answer 78

tropical and subtropical regions

Question 79

is Pythium insidiosum a fungi

Answer 79

no -> its an aquatic oomycete that has fungal-like hyphae in tissues

Question 80

what is pythiosis

Answer 80

lesions similar to mycetoma, disease similar to mucormycosis

Question 81

what is a mycetoma

Answer 81

granulomatous nodules of subcutaneous tissue

Question 82

what is mucormycosis

Answer 82

inhalation of spores or inoculation via trauma leading to mycetoma - like granulomas

Question 83

what is phaeohyphomycosis

Answer 83

mycetoma-like masses