Wildlife Diseases

Question 1

What causes myxomatosis? What 3 species are most affected?

Answer 1

dsDNA virus, Leporipoxvirus = bighead, mosquito disease, mixi

1. American rabbits - enzootic, mild disease
2. European rabbits (domestic pets in USA and Australia) - epizootic, severe disease
3. hares (Lepus spp.)

Question 2

How is myxomatosis transmitted? What is its pathogenesis?

Answer 2

ARTHROPODS - mosquitoes (America), fleas (Europe)

• virus infects epithelial (mucosal) cells and fibroblasts and locally proliferates into myxomas (pseudo-tumors)
• virus then infects lymphocytes and spreads to the LNs resulting in viremia from leukocyte trafficking

Question 3

How does myxomatosis result in myxomas?

Answer 3

virus infects epithelium and secretes myxoma growth factor, EGF

Question 4

What are the 2 main results from myxomatosis?

Answer 4

1. severe lesions may result in death due to emaciation, blindness, predation, and other trauma due to tumor growth or secondary bacterial infection (conjunctivitis)
2. less severe (American) form allows for myxoma regression

Question 5

How do the clinical signs of myxomatosis compare in American and European rabbits?

Answer 5

AMERICAN = mild disease with localized myxomas forming 4-8 days post-exposure and eventual regression

EUROPEAN = large myxomas form 3-4 dpe mostly around the eyes and nose with suppurative blepharoconjunctivitis, dermatitis, peianal edema, and a high mortality rate

Question 6

What results from atypical myxomatosis?

Answer 6

viral interstitial pneumonia

Question 7

Myxomatosis, European rabbit:

Answer 7

• more severe
• swelling and redness around the eyelids due to secondary conjunctivitis

Question 8

Myxomatosis, European rabbit disease progression:

Answer 8

• more severe
• suppurative exudate

Question 9

What are the 2 major gross findings with myxomatosis?

Answer 9

1. subcutaneous mucinous (gelatinous) masses particularly on the face and perineum = myomas
2. mucopurulent blepharoconjunctivitis with nasal discharge

Question 10

What are some additional gross findings with myxomatosis?

Answer 10

• interstitial pneumonia with edema and hemorrhage (atypical)
• edema of perineum
• hemorrhages in skin, heart, GIT, kidney, LN, and testes
• splenomegaly
• LN edema

Question 11

Myxomatosis, myxoma:

Answer 11

mucinous (gelatinous) masses around eyes and nose

Question 12

Atypical myxomatosis:

Answer 12

• interstitial pneumonia
• frothy discharge in trachea = edema
• hemorrhage
• rib impressions

Question 13

What are the 2 major histopathological findings in myxomatosis? What are 2 other findings?

Answer 13

1. epithelial hyperplasia with ballooning degeneration and eosinophilic IC viral inclusions
2. myxoma cells (mesenchymal spindloid to stellate) separated by abundant myxomatous matrix in dermis

• lymphoid depletion within spleen and LN
• focal areas of necrosis in LN, pneumocytes, spleen, and centrilobular hepatocytes

Question 14

Myxomatosis, epithelial hyperplasia:

Answer 14

• thickened epidermis with collagen fibers separated by mucin
• can be stained with Alcian blue to picture

Question 15

Myxomatosis, ballooning degeneration:

Answer 15

• epithelial hyperplasia and hyperkeratosis
• presence of heterophils
• ballooning degeneration with nucleus pushed to the top

Question 16

Myxomatosis, inclusion bodies:

Answer 16

eosinophilic IC IB

Question 17

Myxomatosis, IC inclusion body:

Answer 17

eosinophilic!

Question 18

Myxomatosis, myxoma cells:

Answer 18

• found within myxomatous matrix in the dermis
• spindle/stellate
• green = IC inclusion

Question 19

How is myxomatosis diagnosed? Prevented/controlled?

Answer 19

characteristic clinical signs, gross lesions, and histopath + PCR, EM (dumbbell-shaped)

• some vaccinations available
• keep mosquitoes and fleas away from rabbits

Question 20

What causes snake fungal disease? What species is mostly affected?

Answer 20

Ophidiomyces ophiodiicola - hibernation blisters/sores

rattlesnakes especially in Midwestern and Eastern USA —> Eastern massasauga rattlesnakes

Question 21

What are the 5 steps to snake fungal disease pathogenesis?

Answer 21

1. Ophidiomyces ophidiodiicola breaches the stratus corneum through abrasions and invades the epidermis by breaking down keratin and ECM with enzymes of ammonia release by urease
2. snake mounts an immune response, recruiting heterophils, macrophages, and multinucleated giant cells (+ edema)
3. epidermis becomes necrotic (yellow/brown crusts) and detaches causing ulcerations/erosion
4. fungus proliferates in the epidermis +/- dermis, subcutis, muscle, and bone
5. granulomas develop in skin and deeper tissue

Question 22

What are the main 2 results of snake fungal disease?

Answer 22

1. systemic dissemination in captive snakes - not common in wild, rarely live long enough
2. death due to emaciation, predation, and secondary bacterial infection

Question 23

What are the 6 clinical signs associated with snake fungal disease?

Answer 23

1. yellow/brown plaques*
2. increased moulting frequency (may clear infection)
3. retained spectacles or scales (dysecdysis)
4. altered behavior —> behavior fever where snake moves to warm areas to increase body temperature (gives itself a fever)
5. deformed head
6. emaciation

Question 24

Snake fungal disease:

Answer 24

• yellow/brown plaques
• deformed head

Question 25

Snake fungal disease:

Answer 25

- yellow/brown plaques - deformed head - retained and opaque spectacles that are usually lost with molting

Question 26

Snake fungal disease, head:

Answer 26

deformed with yellow/brown plaque - retained spectacle = trouble seeing and eating = emaciation

Question 27

What 2 histopathology lesions are characteristic of snake fungal disease?

Answer 27

1. epidermal erosion/ulceration with granulomatous inflammation (MGC, MQ) surrounded by lymphocytes, plasma cells, heterophils, and fibroblasts 2. granulomas with fungal hyphae

Question 28

Snake fungal disease, granuloma:

Answer 28

MGC + MQ with fungal hyphae (branches stain with silver and PAS)

Question 29

Snake fungal disease, fungal hyphae:

Answer 29

Question 30

How is snake fungal disease diagnosed? What must be ruled out? How can this be done?

Answer 30

charcteristic clincal signs, gross lesions, and histopathology + PCR, fungal culture mycobacteriosis (fungi may be secondary invaders) ---> stain positive on Acid Fast, unlike fungi

Question 31

How can snake fungal disease be prevented/controlled?

Answer 31

- field hygiene (disinfect equipment, change gloves between snakes) - population health - CAPTIVE: quarantine, antifungal vapors

Question 32

What are 2 causes of chytridiomycosis? What species are most affected by each?

Answer 32

1. Batrachochytrium dendrobatidis - frogs 2. Batrachochytrium salamandrivorans - salamanders

Question 33

What is the lifecycle of Batrachochytrium dendrobatidis like?

Answer 33

- spores are able to swim/move within the skin or soil - spores aggregate and eventually burst from their cyst - zoospores are able to then infect the host

Question 34

What are the 5 steps to chytridiomycosis pathogenesis? What is able to happen at the end of the cycle?

Answer 34

1. motile zoospores invade keratin of the stratum corneum 2. zoosporangia develop in epidermal cells (keratinocytes), where they are able to mature and release zoospores 3. epidermis thickens (hyperplasia/hyperkeratosis) with minimal to absent inflammation 4. respiration and electrolyte balance are altered, leading to hyperkalemia impacting myocardial contractility (amphibian skin is important for electrolyte balance) 5. death zoospores are able to live in the environment or skin of other amphibians (facultative pathogen)

Question 35

What are 4 clinical signs associated with chytridiomycosis caused by Bd? What animals are most susceptible?

Answer 35

1. skin hyperermia (red leg is NOT a disease) likely due to a secondary bacterial infection and skin thickening requiring more blood supply 2. depression, anorexia 3. increased skin shedding without it being consumed 4. seizures due to electrolyte imbalance froglets (just went through metamorphosis)

Question 36

What are the 3 clinical signs associated with chytridiomycosis caused by Bsal?

Answer 36

1. skin erosion to ulceration 2. depression, anorexia 3. increased skin shedding

Question 37

What clinical signs are associated with frogs infected by Bsal? Which are more susceptible?

Answer 37

skin hyperemia or nothing at all froglets - have a much higher concentration of keratin compared to tadpoles to acclimate to land

Question 38

Chytridiomycosis, Bsal

Answer 38

skin erosion to ulceration

Question 39

What histopathological lesions are associated with chytridiomycosis?

Answer 39

Bd = epidermal hyperplasia and hyperkeratosis with occasional inflammation Bsal = epidermal hyperplasia and erosion to ulceration

Question 40

Chytridiomycosis, Bd, histo:

Answer 40

epidermal hyperplasia/hyperkeratosis + zoosporangia

Question 41

Chytridiomycosis, Bd, epidermis:

Answer 41

- hyperplasia, hyperkeratosis - zoosporangia

Question 42

Chytridiomycosis, Bsal:

Answer 42

epidermal hyperplasia with ulceration

Question 43

How is chytridiomycosis diagnosed?

Answer 43

PCR on skin swabs + histopathology for new areas and Bsal in North America

Question 44

How is Chytridiomycosis prevented/controlled?

Answer 44

- field hygiene - clean trade - population health* (ESPECIALLY FOR BSAL ---> high mortality rate to North American salamanders with a large species diversity and richness)