Lec: Fungal Diseases

Three Basic Forms of Fungal Disease

1. Mycosis is the direct invasion of cells by fungus

2. Mycotoxicosis results from ingestion of fungal toxins

3. Allergic diseases: esp. occur when fungal colonies develop in the lungs

Aspergillus spp.

saprophytic filamentous fungi that occur worldwide

grow in damp soils, decaying vegetation, organic debris, feed grains

species most commonly infected include waterfowl, gulls, and corvids - but all birds and most mammals should be considered potential hosts

Aspergillosis

aerosolized spores are inhaled, but dissemination through the gut, blood, or lymph is possible

disease is most commonly associated with young animals or w/ stress and immunosuppression

colonization results in erosion of tissues leading to the possibility of dissemination and host response

signs: pneumonia, may open and close their bills when breathing, wings may drop, may seem mildly to severely depressed

Chytrid fungus (Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal))

Hosts: amphibians, but not all equally susceptible

found in water or soil, asexual reproduction occurs in the zoosporangium and zoospores are the infective stage

attacks keratin (tough, fibrous protein) that forms a resistant later in animal skin, and this later is damaged by chytridiomycosis

1. toxic, proteolytic enzymes are released by the fungus

2. Loss of electrolytes negatively affects osmoregulation and/or oxygen uptake

what are the two hypotheses that explain how Batrachochytrium dendrobatidis (chytrid fungus) directly kills its host

Reduce anthropogenic stress, promote foodwebs to increase micropredators on zoospores, and consider in-situ treatment using itraconazole

what are some management techniques for dealing with chytrid fungus

tadpoles have less keratin in their skin, tooth rows, etc. than adults and this fungus primarily attacks keratin

Why aren’t tadpoles as susceptible to chytridiomycosis as are metamorphosed frogs?

White-Nose Syndrome (caused by Pseudogymnoascus destructans)

DH: Vespertillionid bats in the NE US and SE Canada

No IH

Causes irritation that unnecessarily awakes the bats from torpor, causing them to starve due to inadequate fat reserves necessary to support extra activity

damaged wings = increase heat loss during hibernation, arousal of bats, and impaired flight

regulation of human access to caves, mines, and tunnels that serve as hibernacula

decontamination of tourists, researchers, and spelunkers at cave entrances

temp control to increase cave heat beyond the optimal range of the cold-loving fungus (how would this affect other wildlife)

fungicide spray in caves

treatment/rehabilitation

soil bacteria that inhibits mold growth

a vaccine

what are some of the management tactics for battling white nose syndrome

arousal of bats during hibernation, increased heat loss during hibernation, impaired flight due to wing damage, and skin-mediated fluid loss and dehydration

Although the most common cause of death is still debated, Pseudogymnoascus destructans is thought to kill bats by which of the following mechanisms?

bats provide important ecosystem services, Pseudogymnoascus destructans kills a high % of bats in hibernaculae, several bat species of conservation concern overlap the range of the epizootic, and current management strategies haven’t been enough to stop the spread

The greatest risks of white-nosed syndrome in bats are related to which concept(s)?

Ophidiomyces ophiodiicola

what fungus causes Snake Fungal Disease (SFD)

Snake Fungal Disease (SFD)

opportunistic soil fungus in a variety of snakes in the Eastern US that causes widespread morbidity and mortality

No IH or DH (opportunistic)

fungus attacks keratin

causes lesions, pneumonia, and even liver disease

Management of SFD (caused by Ophidiomyces ophiodiicola)

concern that the pet trade may spread SFD

public education and customs inspectors are essential

fungus is inhibited at a temp below 7 C, snakes that hibernate above this temp may be more susceptible

snakes can be treated with antifungal and treated with thermal and nutritional supportive therapy