Exotics Top Topics - Infectious Aquatic Diseases Part 2 Flashcards
what is the classic case of koi herpes virus?
affects koi or common carp - mottled red/white gills +/- hemorrhaging, sunken eyes, notched nose
surface swimming, lethargy, respiratory distress
high morbidity & mortality
what is the etiology of koi herpes virus?
caused by cyprinid herpes virus 3
how is koi herpes virus diagnosed?
PCR is ideal for clinically diseased fish or virus isolation on either fresh dead fish or various tissues (including gills) from very sick fish
why are negative blood samples for antibodies not great for diagnosing koi herpes virus?
it won’t rule out survivor/carrier status & the animal may also be negative for early stage disease
what is the recommended treatment for koi herpes virus?
depopulation recommended but not mandatory - survivors become carriers & perpetuate disease spread
what should be avoided at koi show events?
showing koi in common/shared containers that are used to display fish
what detection option may be used for koi herpes virus?
30 day quarantine period at 75°F for new arrivals but carriers may not show clinical signs within this window
is koi herpes virus reportable? who to? where is it seen?
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
what other animals can be asymptomatic carriers for koi herpes virus?
goldfish
what is important to know about the terms fish louse, fish lice, & sea lice?
they are just terms used to describe a number of different species of freshwater & marine crustacean parasites of fish
what is the classic case presentation of fish louse?
in many cases, adults can be seen grossly & attached causing skin/gill damage - large numbers can cause death
what are the 2 most common groups of sea lice?
lepeophtheirus salmonis & caligus spp - both are copepod crustacean parasites
what sea lice are seen on freshwater fish?
argulus (branchiuran crustaceans) - wild game fish, bait fish, goldfish, & koi in ponds or aquariums
how are sea lice diagnosed?
use direct visualization but can verify with microscopic examination of the organism
how are sea lice treated?
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
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?
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
what is the classic case presentation of carp/koi pox virus? what about severe cases?
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
what is the etiology of carp/koi pox virus?
caused by cyprinid herpesvirus-1 (related to the virus that causes koi herpes virus)
how is carp/koi pox virus diagnosed?
history, visual assessment, biopsy, & histopathology
how can water temperature be used to treat carp/koi pox virus?
most lesions regress at water temps above 68°F
T/F: carp/koi pox virus is one of the oldest known diseases of fish
true
how is carp/koi pox virus prevented?
good husbandry, biosecurity, & increasing temperatures in a hospital tank/system will help lesions regress
why is carp/koi pox virus bad for koi?
can cause aesthetic issues & decrease the value of the fish - may need to cull
how is carp/koi pox treated?
usually self-limiting - minimal clinical importance in adults but may be fatal in fry < 2 months of age
what is another name for ulcer disease in fish?
furunculosis
what is the classic acute presentation of ulcer disease in fish?
appears like bacterial hemorrhagic septicemia - may have hemorrhages in gills, tail, fins, muscles, & internal organs
what is the classic chronic presentation of ulcer disease in fish?
focal swelling, hemorrhage, & tissue necrosis in muscle
what systemic illness can be seen in ulcer disease of fish?
disease can progress to furuncles which are deep abscesses that ooze out of the skin & liquefactive necrosis in spleen, liver, & kidney
what fish get the atypical strain of ulcer disease?
non-salmonids - may also infect salmonids
what is the etiology of ulcer disease in fish?
aeromonas salmonicida - gram negative non-motile rod
sub-species/strain variants will vary & determine species susceptibility and/or clinical signs (typical or atypical)
how is ulcer disease in fish diagnosed?
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)
how is ulcer disease treated in fish?
abx based on culture/sensitivity & legal access
ulcer disease presentation & diagnosis by PCR may preclude clinical signs, so use best judgement for treatment
ulcer disease is an important condition that affects what fish?
salmonids, goldfish, & koi - also some other freshwater & marine species
what have been the results of vaccination in fish for a. salmonicida (ulcer disease)?
available for use in salmonids - mixed results with use of ulcer disease atypical strain vaccines in koi
what is the mortality rate of mycobacterium in fish?
low level mortalities - over weeks or months within a population
what fish populations are affected by mycobacterium?
aquaculture or aquarium - may be associated with older or more immunosuppressed (stressed) fish, poor quality, high organic load, poor husbandry, & cannibalism
what are poor doer signs seen in fish with mycobacterium infections?
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
what is the etiology of mycobacterial diseases in fish?
m. marinum, m. fortuitum, & m. chelonae
how is mycobacterium in fish diagnosed at necropsy?
see internal/external nodules, granulomas, gray-white necrotic foci in multiple organs usually first seen in spleen & kidney
how is mycobacterium diagnosed?
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)
what management options are used for valuable fish species with mycobacterium?
hobbyist or public aquarium - may benefit from supportive care but treatment is still difficult
what management options are used for fish for broodstock production with mycobacterium?
depopulate or culling is strategic - targeted populations or specimens & reduce infectious load in the system (cleaning, water changes)
why is cleaning & disinfection more complicated for mycobacterium in fish?
bacteria has a thick & waxy coat & other survival features
T/F: antibiotics are ineffective in treating mycobacterium in fish
true
what are the risk factors that predispose fish to mycobacterial infections?
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)
T/F: mycobacterium in fish poses a zoonotic risk to people & can hide in biofilms or on surfaces
true
why is confirmatory testing of mycobacterium in fish critical?
many other causes of granulomas in fish - need to confirm!!!
what is hole in the head disease of seahorses?
seahorse mycobacterial disease
what is the classic case presentation of hole in the head disease?
skin ulcerations & emaciation
what are the factors make hole in the head disease worse? what is the etiology?
stress, crowding, poor water quality will all make it worse
mycobacterium species
how is hole in the head disease diagnosed in seahorses?
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
how is hole in the head disease treated?
no treatment - bleach is ineffective at typical doses
UV light may help reduce loading but mycobacteria thrive within biofilms & can be released
what are the risk factors of hole in the head disease?
stress, excess organic debris, low pH, & low oxygen in the water
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
true
