Exotics Top Topics - Infectious Aquatic Diseases Part 1 Flashcards
what is the classic case presentation of columnaris disease?
saddleback lesions -patches pale discoloration of skin +/- red edges located dorsally at the base & around the dorsal fin
gills have patchy white or tan discolored areas (necrosis)
may have increased mucus/slimy exudate
fin deterioration - anorexia oral mucosal erosion and/or ulceration
what is the etiology of columnaris disease?
flavobacterium columnare - gram negative rod shaped long & motile filamentous bacterium
how is columnaris disease diagnosed?
waving haystacks of bacteria on wet mount slides of lesions from skin/fins/gills
considered classic but not always evident
how is columnaris disease treated?
early infection/bath treatment - add potassium permanganate/hydrogen peroxide, or diquat to the water
chronic disease - bath treatment as above but may also need to treat with medicated feed containing oxytetracycline
how is columnaris disease prevented?
minimize traumatic injuries, reduce organic debris in the tank, including uneaten feed
what can predispose fish to columnaris disease?
environmental or handling factors often compromise skin/mucus & can spread the disease rapidly
what may serve as a reservoir for columnaris disease?
uneaten food
there is a vaccine for columnaris disease for what fish in the US?
large mouth bass & channel catfish
what is the classic case presentation of motile aeromonad septicemia?
variable morbidity/mortality rates (depend on water quality, dissolved oxygen level, stress level), external hemorrhages/petechiae in the viscera, body wall, or peritoneum
may see ascites
what is the etiology of motile aeromonad septicemia?
most often caused by aeromonas spp infection in fresh water fish
vibrio are a more common cause of a similar hemorrhagic septicemia in marine fish
occurs often secondarily to poor management or husbandry issues
how is motile aeromonad septicemia diagnosed?
bacterial culture of kidney, brain, or other affected organs
how is motile aeromonad septicemia treated?
correct underlying stressors including environmental or managerial stressors
abx based on c/s
what are some risk factors for mobile aeromonad septicemia?
poor water quality, low dissolved oxygen levels, elevated ammonia, trauma, and handling stress
what is red sore disease?
common manifestation of motile aeromonad septicemia in wild game fish - combo of motile aeromonas infection & protist parasite infection
what is the differentiation between ich & white spot disease?
ich disease - freshwater fish & white spot disease - fresh water & marine
what is the classic case presentation of ich/white spot disease?
small white spots all over fish (body, gills, fins)
extreme lethargy, inappetence, mortality
what is the freshwater etiology of ich?
ichthyophthirius multifilis - ciliated obligate parasitic protozoa that can reproduce exponentially
what is the marine etiology of ich?
cryptocaryon irritans has a similar explosive numbers type life cycle
how is ich/white spot disease diagnosed?
microscopic evaluation of skin, fins, gill scrape/biopsy - make a slide to see characteristic ciliated protozoa with gray/granular interior that rotates slowly or moves around like an amoeba (trophont)
what is seen on diagnosis of mature stages of ich?
horseshoe-shaped macronucleus is more apparent
what stage of the life cycle can be treated with ich/white spot disease?
only the free swimming infective stages (theronts) in the water for both ich & cryptocaryon
what treatment is used for pet fish with ich/white spot disease?
multiple treatments of formalin or malachite green (latter can’t be dispensed by the vet but may be available over the counter)
fresh water species - 4-5 g/L salt for an extended period of time
copper therapy
what does it mean if a fish is refractory to treatment of ich/white spot disease?
means the parasites are encysted in the environment & on the fish
what does life cycle of ich/white spot disease depend on?
temp of water - when warmer, ich treatment period may last a week or more
why may treatment be needed for 4-6 weeks for cryptocaryon?
much longer cycle than fresh water ich
what is the problem with fish that recovery from ich/white spot disease?
they can be silent shedders in the future & have some degree of immunity
why do we see the classic white spots on fish with ich/white spot disease?
encysted parasite we are seeing
what is the classic case of velvet disease in freshwater & marine fish?
swimming against objects or substrate (flashing), lethargy, gathering near the surface more than usual
affected fish have a dusty velvety appearance but it may not be apparent in lighter colored fish or in predominantly gill infections
what is the etiology of velvet disease?
amyloodinium ocellatum - parasitic dinoflagellate that attaches to & invades the skin of fish
piscinoodonium pillalare - freshwater counter parts
how is velvet disease diagnosed?
wet mount preparations of gill tissue shows many small brown/golden organisms
microscopic exam - round ovoid or pear shaped brown/golden trophonts (feeding stage) are evident & anchored to the gill epithelium, fins, & skin
what are the treatment options for pet fish & farm fish with velvet disease?
pet fish - chloroquine extended bath
extended treatment of copper sulfate one of the few legal options for food animals but can be used in marine pet fish & in freshwater
pH adjusted freshwater dip for 3-5 minutes will help remove significant portions of the brackish to marine amyloodinium feeding stage
salt water dip for at 30 ppt for 3-5 minutes will help remove freshwater parasite
what life stage of velvet disease that is resistant to treatment?
tomonts - reproductive stage
what is the classic case presentation of lymphocystis in fish?
papillomatous or pebble like masses or warts on fins, gills, or skin
what is the etiology of lymphocystis?
infection with iridovirus known as lymphocystivirus or lymphocystis disease virus - family iridoviridae
how is lymphocystis diagnosed?
microscopic evaluation of masses reveals enlarged fibroblasts which become virus making factories which look like balloons
how is lymphocystis treated?
no treatment - self limiting condition if infection is not too severe (up to 6 weeks)
isolation of grossly/visibly infected specimens may help reduce viral loading & spread
supportive care - increased or decreased salinity to aid in osmoregulation
abx if secondary infections
how may lymphocystis cause death?
if significant portions of skin/gills are affected in moderate to severe cases - impaired osmoregulation, secondary bacterial infections, & other opportunistic diseases
what fish are not affected by lymphocystis?
cyprinids - koi/goldfish, catfish, or salmon
what is the classic case presentation of head & lateral erosion in fish?
hole in head disease - seen in freshwater, especially in cichlids, & ornamental marine species (especially in surgeon fishes, tangs, & angel fish)
erosions around eyes/on head & along lateral line
what is the etiology of hold in head syndrome? how is it diagnosed?
considered to be a syndrome - use of activated carbon has been proven as one cause
predisposing factors - nutrition, water quality, high oxidation/reduction potential, & infectious potentials
clinical signs
how is hold in head syndrome treated?
improve water quality, remove activated carbon filters, address any stray voltage near tank, enhance diet/micronutrients including vitamins & antioxidants
metronidazole if flagellate infestation is suspected or diagnosed - administered in feed or added to water
what is the lateral line?
part of the nervous system & helps fish navigate - helps to detect movement, vibration, & pressure differences in water
