Exotics Top Topics - Infectious Aquatic Diseases Part 1

Question 1

what is the classic case presentation of columnaris disease?

Answer 1

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

Question 2

what is the etiology of columnaris disease?

Answer 2

flavobacterium columnare - gram negative rod shaped long & motile filamentous bacterium

Question 3

how is columnaris disease diagnosed?

Answer 3

waving haystacks of bacteria on wet mount slides of lesions from skin/fins/gills

considered classic but not always evident

Question 4

how is columnaris disease treated?

Answer 4

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

Question 5

how is columnaris disease prevented?

Answer 5

minimize traumatic injuries, reduce organic debris in the tank, including uneaten feed

Question 6

what can predispose fish to columnaris disease?

Answer 6

environmental or handling factors often compromise skin/mucus & can spread the disease rapidly

Question 7

what may serve as a reservoir for columnaris disease?

Answer 7

uneaten food

Question 8

there is a vaccine for columnaris disease for what fish in the US?

Answer 8

large mouth bass & channel catfish

Question 9

what is the classic case presentation of motile aeromonad septicemia?

Answer 9

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

Question 10

what is the etiology of motile aeromonad septicemia?

Answer 10

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

Question 11

how is motile aeromonad septicemia diagnosed?

Answer 11

bacterial culture of kidney, brain, or other affected organs

Question 12

how is motile aeromonad septicemia treated?

Answer 12

correct underlying stressors including environmental or managerial stressors

abx based on c/s

Question 13

what are some risk factors for mobile aeromonad septicemia?

Answer 13

poor water quality, low dissolved oxygen levels, elevated ammonia, trauma, and handling stress

Question 14

what is red sore disease?

Answer 14

common manifestation of motile aeromonad septicemia in wild game fish - combo of motile aeromonas infection & protist parasite infection

Question 15

what is the differentiation between ich & white spot disease?

Answer 15

ich disease - freshwater fish & white spot disease - fresh water & marine

Question 16

what is the classic case presentation of ich/white spot disease?

Answer 16

small white spots all over fish (body, gills, fins)

extreme lethargy, inappetence, mortality

Question 17

what is the freshwater etiology of ich?

Answer 17

ichthyophthirius multifilis - ciliated obligate parasitic protozoa that can reproduce exponentially

Question 18

what is the marine etiology of ich?

Answer 18

cryptocaryon irritans has a similar explosive numbers type life cycle

Question 19

how is ich/white spot disease diagnosed?

Answer 19

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)

Question 20

what is seen on diagnosis of mature stages of ich?

Answer 20

horseshoe-shaped macronucleus is more apparent

Question 21

what stage of the life cycle can be treated with ich/white spot disease?

Answer 21

only the free swimming infective stages (theronts) in the water for both ich & cryptocaryon

Question 22

what treatment is used for pet fish with ich/white spot disease?

Answer 22

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

Question 23

what does it mean if a fish is refractory to treatment of ich/white spot disease?

Answer 23

means the parasites are encysted in the environment & on the fish

Question 24

what does life cycle of ich/white spot disease depend on?

Answer 24

temp of water - when warmer, ich treatment period may last a week or more

Question 25

why may treatment be needed for 4-6 weeks for cryptocaryon?

Answer 25

much longer cycle than fresh water ich

Question 26

what is the problem with fish that recovery from ich/white spot disease?

Answer 26

they can be silent shedders in the future & have some degree of immunity

Question 27

why do we see the classic white spots on fish with ich/white spot disease?

Answer 27

encysted parasite we are seeing

Question 28

what is the classic case of velvet disease in freshwater & marine fish?

Answer 28

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

Question 29

what is the etiology of velvet disease?

Answer 29

amyloodinium ocellatum - parasitic dinoflagellate that attaches to & invades the skin of fish

piscinoodonium pillalare - freshwater counter parts

Question 30

how is velvet disease diagnosed?

Answer 30

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

Question 31

what are the treatment options for pet fish & farm fish with velvet disease?

Answer 31

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

Question 31

what life stage of velvet disease that is resistant to treatment?

Answer 31

tomonts - reproductive stage

Question 32

what is the classic case presentation of lymphocystis in fish?

Answer 32

papillomatous or pebble like masses or warts on fins, gills, or skin

Question 33

what is the etiology of lymphocystis?

Answer 33

infection with iridovirus known as lymphocystivirus or lymphocystis disease virus - family iridoviridae

Question 34

how is lymphocystis diagnosed?

Answer 34

microscopic evaluation of masses reveals enlarged fibroblasts which become virus making factories which look like balloons

Question 35

how is lymphocystis treated?

Answer 35

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

Question 36

how may lymphocystis cause death?

Answer 36

if significant portions of skin/gills are affected in moderate to severe cases - impaired osmoregulation, secondary bacterial infections, & other opportunistic diseases

Question 37

what fish are not affected by lymphocystis?

Answer 37

cyprinids - koi/goldfish, catfish, or salmon

Question 38

what is the classic case presentation of head & lateral erosion in fish?

Answer 38

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

Question 39

what is the etiology of hold in head syndrome? how is it diagnosed?

Answer 39

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

Question 40

how is hold in head syndrome treated?

Answer 40

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

Question 41

what is the lateral line?

Answer 41

part of the nervous system & helps fish navigate - helps to detect movement, vibration, & pressure differences in water