Exotics Top Topics - Infectious Aquatic Diseases Part 2

Question 1

what is the classic case of koi herpes virus?

Answer 1

affects koi or common carp - mottled red/white gills +/- hemorrhaging, sunken eyes, notched nose

surface swimming, lethargy, respiratory distress

high morbidity & mortality

Question 2

what is the etiology of koi herpes virus?

Answer 2

caused by cyprinid herpes virus 3

Question 3

how is koi herpes virus diagnosed?

Answer 3

PCR is ideal for clinically diseased fish or virus isolation on either fresh dead fish or various tissues (including gills) from very sick fish

Question 4

why are negative blood samples for antibodies not great for diagnosing koi herpes virus?

Answer 4

it won’t rule out survivor/carrier status & the animal may also be negative for early stage disease

Question 5

what is the recommended treatment for koi herpes virus?

Answer 5

depopulation recommended but not mandatory - survivors become carriers & perpetuate disease spread

Question 6

what should be avoided at koi show events?

Answer 6

showing koi in common/shared containers that are used to display fish

Question 7

what detection option may be used for koi herpes virus?

Answer 7

30 day quarantine period at 75°F for new arrivals but carriers may not show clinical signs within this window

Question 8

is koi herpes virus reportable? who to? where is it seen?

Answer 8

highly contagious - reportable in US & canada to respective federal authorities & to the world organization for animal health (OIE)

considered endemic & common in US & many other parts of the world

Question 9

what other animals can be asymptomatic carriers for koi herpes virus?

Answer 9

goldfish

Question 10

what is important to know about the terms fish louse, fish lice, & sea lice?

Answer 10

they are just terms used to describe a number of different species of freshwater & marine crustacean parasites of fish

Question 11

what is the classic case presentation of fish louse?

Answer 11

in many cases, adults can be seen grossly & attached causing skin/gill damage - large numbers can cause death

Question 12

what are the 2 most common groups of sea lice?

Answer 12

lepeophtheirus salmonis & caligus spp - both are copepod crustacean parasites

Question 13

what sea lice are seen on freshwater fish?

Answer 13

argulus (branchiuran crustaceans) - wild game fish, bait fish, goldfish, & koi in ponds or aquariums

Question 14

how are sea lice diagnosed?

Answer 14

use direct visualization but can verify with microscopic examination of the organism

Question 15

how are sea lice treated?

Answer 15

treatment options are limited & will vary depending upon species & situation - consider legalities, human health, & environmental issues in each situation

drugs - chitin/growth inhibitors affecting juvenile stages, organophosphates, & emamectin

secondary bacterial infections may require abx

Question 16

what sea louse is a significant problem in ocean-farmed salmonids? what sea louse can infect numerous marine species? what sea louse can infect many different freshwater species, lay eggs in the environment, & has been shown to be a vector of bacterias/viruses?

Answer 16

ocean farmed - lepeophtheirus salmonis

numerous species - caligus

females of both hold egg sacs on their bodies

many species/eggs in environment/bacteria/viruses - argulus species

Question 17

what is the classic case presentation of carp/koi pox virus? what about severe cases?

Answer 17

classic - benign, non-necrotizing epidermal hyperplasia, lesions are white to cream, smooth or raised, often look like candle wax drippings on the fish

severe - papillomatous growths +/- secondary bacterial infections

Question 18

what is the etiology of carp/koi pox virus?

Answer 18

caused by cyprinid herpesvirus-1 (related to the virus that causes koi herpes virus)

Question 19

how is carp/koi pox virus diagnosed?

Answer 19

history, visual assessment, biopsy, & histopathology

Question 20

how can water temperature be used to treat carp/koi pox virus?

Answer 20

most lesions regress at water temps above 68°F

Question 21

T/F: carp/koi pox virus is one of the oldest known diseases of fish

Answer 21

true

Question 22

how is carp/koi pox virus prevented?

Answer 22

good husbandry, biosecurity, & increasing temperatures in a hospital tank/system will help lesions regress

Question 23

why is carp/koi pox virus bad for koi?

Answer 23

can cause aesthetic issues & decrease the value of the fish - may need to cull

Question 24

how is carp/koi pox treated?

Answer 24

usually self-limiting - minimal clinical importance in adults but may be fatal in fry < 2 months of age

Question 25

what is another name for ulcer disease in fish?

Answer 25

furunculosis

Question 26

what is the classic acute presentation of ulcer disease in fish?

Answer 26

appears like bacterial hemorrhagic septicemia - may have hemorrhages in gills, tail, fins, muscles, & internal organs

Question 27

what is the classic chronic presentation of ulcer disease in fish?

Answer 27

focal swelling, hemorrhage, & tissue necrosis in muscle

Question 28

what systemic illness can be seen in ulcer disease of fish?

Answer 28

disease can progress to furuncles which are deep abscesses that ooze out of the skin & liquefactive necrosis in spleen, liver, & kidney

Question 29

what fish get the atypical strain of ulcer disease?

Answer 29

non-salmonids - may also infect salmonids

Question 30

what is the etiology of ulcer disease in fish?

Answer 30

aeromonas salmonicida - gram negative non-motile rod sub-species/strain variants will vary & determine species susceptibility and/or clinical signs (typical or atypical)

Question 31

how is ulcer disease in fish diagnosed?

Answer 31

isolate a pure culture from tissue or blood samples using PCR especially for atypical strains that are primarily epidermal (rapid overgrowth of secondary bacterial species impairs culture results)

Question 32

how is ulcer disease treated in fish?

Answer 32

abx based on culture/sensitivity & legal access ulcer disease presentation & diagnosis by PCR may preclude clinical signs, so use best judgement for treatment

Question 33

ulcer disease is an important condition that affects what fish?

Answer 33

salmonids, goldfish, & koi - also some other freshwater & marine species

Question 34

what have been the results of vaccination in fish for a. salmonicida (ulcer disease)?

Answer 34

available for use in salmonids - mixed results with use of ulcer disease atypical strain vaccines in koi

Question 35

what is the mortality rate of mycobacterium in fish?

Answer 35

low level mortalities - over weeks or months within a population

Question 36

what fish populations are affected by mycobacterium?

Answer 36

aquaculture or aquarium - may be associated with older or more immunosuppressed (stressed) fish, poor quality, high organic load, poor husbandry, & cannibalism

Question 37

what are poor doer signs seen in fish with mycobacterium infections?

Answer 37

typically over a prolonged period (weeks to months) may share similarities with systemic bacterial/viral infections coelemic swelling, pine coning, exophthalmia, skin ulcerations, hemorrhages, weight loss, & death

Question 38

what is the etiology of mycobacterial diseases in fish?

Answer 38

m. marinum, m. fortuitum, & m. chelonae

Question 39

how is mycobacterium in fish diagnosed at necropsy?

Answer 39

see internal/external nodules, granulomas, gray-white necrotic foci in multiple organs usually first seen in spleen & kidney

Question 40

how is mycobacterium diagnosed?

Answer 40

acid fast rods seen on cytology/histopath - PCR followed by culture & ID in some cases, may see caseous or abscess like lesions, hyperpigmentation, & no evidence of granulomas or nodules internally (histiocytic vs granulomatous inflammation)

Question 41

what management options are used for valuable fish species with mycobacterium?

Answer 41

hobbyist or public aquarium - may benefit from supportive care but treatment is still difficult

Question 42

what management options are used for fish for broodstock production with mycobacterium?

Answer 42

depopulate or culling is strategic - targeted populations or specimens & reduce infectious load in the system (cleaning, water changes)

Question 43

why is cleaning & disinfection more complicated for mycobacterium in fish?

Answer 43

bacteria has a thick & waxy coat & other survival features

Question 44

T/F: antibiotics are ineffective in treating mycobacterium in fish

Answer 44

true

Question 45

what are the risk factors that predispose fish to mycobacterial infections?

Answer 45

stress, excess organic debris, & presence of biofilms (including those difficult to access, ie pipeline), low pH, low O2 in water, age, immunosuppression, & dose (environmental load)

Question 46

T/F: mycobacterium in fish poses a zoonotic risk to people & can hide in biofilms or on surfaces

Answer 46

true

Question 47

why is confirmatory testing of mycobacterium in fish critical?

Answer 47

many other causes of granulomas in fish - need to confirm!!!

Question 48

what is hole in the head disease of seahorses?

Answer 48

seahorse mycobacterial disease

Question 49

what is the classic case presentation of hole in the head disease?

Answer 49

skin ulcerations & emaciation

Question 50

what are the factors make hole in the head disease worse? what is the etiology?

Answer 50

stress, crowding, poor water quality will all make it worse mycobacterium species

Question 51

how is hole in the head disease diagnosed in seahorses?

Answer 51

necropsy shows internal granulomas, gray-white necrotic foci especially in the liver, kidney, & spleen see acid fast rods on cytology/histopath, confirm with PCR & culture

Question 52

how is hole in the head disease treated?

Answer 52

no treatment - bleach is ineffective at typical doses UV light may help reduce loading but mycobacteria thrive within biofilms & can be released

Question 53

what are the risk factors of hole in the head disease?

Answer 53

stress, excess organic debris, low pH, & low oxygen in the water

Question 54

T/F: hole in the head disease is a very common zoonotic disease with seahorses being very prone to infection but other mycobacteria can infect all fish species

Answer 54

true