Aquatic Medicine Flashcards
aquatic systems and water quality aquatic diseases
What are the 4 major groups of fish populations that are important in the United States?
- food (ex. atlantic salmon)
- tropical (ex. the cute little fish you see at petco)
- Ornamental/Pond (ex. koi)
- Bait fish (ex. goldfish, minnows)
An OPEN water system has a reliable, suitable water source with excellent water quality.
Why does this system allow for high stocking densities?
Because there is a continuous flow of water coming in and flushing out of the system, therefore metabolic waste does not have the opportunity to build up and cause toxicities to the aquatic population within.
In a __________ water system, there are generally limited stocking densities. There is less total water required for these systems and the water quality is better able to be controlled (most of the time).
closed
For the following system examples, provide the type of system they are – open or closed.
Raceway:
Pond:
Aquarium:
Pens:
Recirculation system
Cage:
Raceway: open
Pond: closed
Aquarium: closed
Pens: open
Recirculation system: closed
Cages: open
What do fish excrete (as waste)?
(4 things)
ammonia
CO2
solid waste
liquid waste
What is the nitrification process?
the aerobic conversion of ammonia (waste produced by fish) into nitrite, followed by the conversion of nitrite into nitrate by bacterial organisms.
Which of the following is MOST toxic to an aquatic species (assume each is within similar ranges)?
a. ammonia
b. nitrite
c. nitrate
b. nitrite
T/F: open systems do not require filtration because dilution is what is creating an appropriate environment without waste.
true
closed systems require some type of filtration in order to convert ammonia to nitrite to nitrate.
What are the top 5 parameters of water quality?
- temp
- dissolved oxygen
- pH
- ammonia
- nitrites and nitrates
Temperature changes affect the metabolism and ______________ of aquatic species. Rapid changes in temperature or temperatures outside of optimal ranges for a specific species will cause stress.
immune response
All of the following are circumstances that would promote what?
- animal and plant respiration
- organic decomposition
- diel cycle (day vs night)
- warm water temperatures
depletion of oxygen
what are the 3 sources of oxygen for aquatic species?
- diffusion
- photosynthesis
- chemical production
Species-specific requirements for dissolved oxygen are approximately 5 ppm minimum.
What signs would be apparent in fish within an environment that has LOW dissolved oxygen?
gulping at the surface
lethargy
increased ventilatory rate
State the acceptable pH range for:
- saltwater fish:
- freshwater fish:
- saltwater fish: 7.8-8.6
- freshwater fish: 6.8-7.8
if ammonia is toxic to fish, then why is the acceptable level of ammonia listed as <0.02 ppm rather than 0 ppm?
these are living animals… something will always be produced by them.
pH and temperature have what influence on ammonia?
increase NH3
salinity, hardness, and CO2 have what influence on ammonia?
decrease NH3
What is ‘new tank syndrome’?
New aquatic systems take at least 6 weeks to overcome excessive ammonia or nitrite levels due to the lack of bacteria available to convert ammonia to nitrite to nitrate.
At first, you are constantly checking the water quality, but after 6 weeks you can better rely on the nitrification process.
How can you measure water salinity in your clinic?
refractometer
measure the specific gravity
T/F: chorine and chloramines are not as toxic to fish because they are present in the waterways on a regular basis.
false – they are toxic to all species of fish and need to be removed by chemicals, aeration, or activated carbon.
Fish and other animals actually have lots of commonalities. What are the 2 biggest differences / adaptations of fish?
- skin – their epithelium is a LIVING layer and they have scales (bony plates) anchored into their dermis to protect themselves.
- gills – respiration, excretion, and osmoregulation (O2 in from water, CO2 and ammonia out, ion exchange and minerals)
T/F: Ejection of scales from the dermis is a normal postmortem change in most aquatic species
false – this indicates damage to the skin/dermis because in order for the scales to come out, they must be pulled from the dermis.
what is the primary site of ammonia secretion for aquatic animals?
gills
T/F: lamellae are so thin that there is almost no energy required for oxygen to go across into the gill filament and for CO2 and ammonia to be excreted out.
true
3 major functions of the gill:
respiration
excretion
osmoregulation
____________ is the process by which a fish adjusts and maintains homeostasis in a changing aquatic environment
osmoregulation
Describe osmoregulation in fresh water fish
fresh water fish have a passive inflow of water into the gills (osmosis) and passive loss of salt from gills (diffusion)
they actively take in salt by the gills, reabsorb salt by kidney (urination), and eliminate large amounts of urine to rid excess water
Describe osmoregulation of salt water fish
they have passive intake of salt through gills (diffusion) and passive loss of water from gills (osmosis)
they actively intake large amounts of water by drinking sea water. the water gets absorbed in the gut, but not the salt. The salt is eliminated actively through the gills. Salt water fish only urinate small amounts in order to conserve their body fluids.
When fish present to your clinic, they are typically presenting with which stress response?
tertiary.
what does the degree of stress and its effect on fish health depend on?
- duration of the stress
- onset of the stress
- absolute degree of the stress
What is the biggest environmental stressor that increases the risk of disease in fish?
poor water quality
What are common clinical signs of disease in fish?
- changed behavior
- decreased appetite
- change in coloration
- dev external lesions
- increased morbidity and mortality
Name this fish disease:
- found in trout and salmon worldwide
- fry and fingerling have dz; adults = subclin carriers
- effects pancreas, cecum, and intestines
- hyperpigmentation, abdominal distention, ascites
- horizontal and vertical transmission
infectious pancreatic necrosis virus (IPN)
Name this fish disease:
- found in trout and salmon in western US
- younger salmonids (<2) have dz; adult = subclin carriers
- effects liver, pancreas, kidneys, and spleen
- anemia, petechial hemorrhage, ascites, abd. distention
- horizontal and vertical transmission
infectious hematopoietic necrosis virus (IHN)
What are the 2 major differences between IPN and IHN?
- Location (IPN=wordwide, IHN=west US)
- Age (IPN= fry and fingerlings, IHN= <2y, both have adult subclin carriers)
Name this fish disease:
- found in salmonids and non-salmonids along pacific coast
- affects liver, kidney, spleen, and intestines
- anemia, petechial hemorrhages, ascites, hyperpigmentation
- horizontal and vertical transmission
- Foreign Animal Disease
Viral hemorrhagic septicemia (VHS)
What is the biggest difference between IHN and VHS?
VHS is a reportable foreign animal disease, IHN is not.
A recent epizootic new strain of VHS (VHS IVb) has been found in ___________. Some fish that become infected will swim in circles, are motionless on the surface,& develop petechial hemorrhages – other times there are no clinical signs or mass mortalities. Survivors of this virus become chronic carriers.
the Great Lakes
Infectious salmonid anemia (ISA) infects trout and salmon. It is responsible for a significant amount of mortalities in “net pens.” Fish experience anemia, scale loss, and severe hemorrhage of the kidney and spleen.
Is this disease a foreign animal disease?
yes
it is found in Scotland, Norway, Chile, Canada, and Maine (USA).
T/F: Any survivors of IPN, IHN, VHS, VHS IVb, and ISA all become subclinical carriers.
true
What is the difference in transmission between IPN and IHN and why would this even be significant?
IPN has vertical transmission INSIDE of the egg – the significance is that you cannot disinfect these types of eggs.
IHN has vertical transmission OUTSIDE of the egg, so this is disinfectable
A fish guys calls you because 80% of his koi fish died within the past 2 days. When you arrive, you see that the dead fish have pale gills with severe lesions. What is your top differential?
koi herpes virus
Do survivors of koi herpes virus become carriers?
yes – they are shedding the virus permanently.
It’s March and a fish guy calls you because a few of his fish are acting weird and a few have died. When you come to check things out, you see that they are swimming in circles, have abdominal distention, and the dead ones have hemorrhage of skin and gills. These fish are cyprinids (carp). Your top differential tells you this may be a foreign animal disease, so you call the state vet.
What is the top differential?
Spring Viremia of Carp
This herpesvirus causes chronic superficial disease in cultured cyprinids. It causes focal benign hyperplasia of the epithelium in winter and early spring, appearing as raised white nodules on skin and fins.
Fish pox / carp pox
what is the treatment for fish/carp pox?
raise the water temperatures and the lesions will go away
they will still be carriers and shedders for life.
T/F: you probably should not issue a CVI for an owner that tells you his fish have had a history of fishpox in the past, but are cured now and are normal at the time of the appointment.
true – this disease is likely not readily apparent because of higher temperatures. however these fish are lifelong carriers and will transmit it to other fish.
This iridovirus occurs worldwide. It is a chronic disease characterized by raised, white nodules on the skin and fins that are infected fibroblastic cells. The disease is self-limiting and rarely fatal.
lymphocystis
T/F: most bacterial diseases in fish are caused by gram negative bacteria that are ubiquitous in the environment and are opportunistic, affecting fish that are experiencing stress.
true
This gram negative bacterial agent occurs in freshwater habitats worldwide. It causes skin and systemic infection. It is RARELY zoonotic.
aeromonas hydrophilia
A coldwater fish producer calls you because his fish have giant nodules on their bodies. The dead ones have necrotic areas that you classify as furuncles. You determine that this is most likely the obligate fish bacterial pathogen called ________________.
aeromonas salmonicida
A marine producer is having issues with fish having skin ulcers and hemorrhages on the tail, fins, and gills. This disease is similar to aeromonas hydrophilia but has zoonotic potential.
What is the agent?
Vibrio
What gram negative agent is responsible for “columnaris disease” causing warm, freshwater fish to have a pale “haystack” colonial appearance.
flavobacterium columnaris
This gram positive agent causes severe bacterial septicemia leading to hemorrhages, skin ulceration, and abnormal behavior (swimming in tight circles).
This disease is zoonotic.
streptococcus
This gram positive agent causes chronic, progressive, multisystemic disease, but usually has low mortality rates. It has significant potential to be zoonotic causing “fish handlers disease” characterized by cutaneous papulopustular to nodular disease on extremities.
mycobacterium
T/F: parasites are often more pathogenic in wild fish than cultured fish because cultured fish have more strict and appropriate husbandry.
false – more common in cultured fish because they are living in a closed environment where fish are in closer contact with one another, are likely the same species, and are likely stressed. The direct life cycle of the parasites allows for quick transmission.
This parasite infects all freshwater fish by penetrating the skin and gill of the host. This parasite has a c-shaped nucleus.
It causes small white dots all over the fish.
ichthyophthirius multifilis
This parasite is similar to “ich” but does NOT have a c-shaped nucleus and is a parasite in marine fish. It invades the skin and gill epithelium.
cryptocaryon irritans
What is the difference between ichthyophthirius multifilis and cryptocaryon irritans?
cryptocaryon irritans is found in marine fish and does NOT have a c-shaped nucleus.
ichthyophthirius multifilis is found in freshwater fish and has a c-shaped nucleus
This parasite causes “whirling disease”, “black tail”, or skeletal deformities in salmonids.
It gets into cartilaginous tissue and the gills and it collapses. It causes mortality in young salmonids and sig pathology in older fish.
myxobolus cerebralis
Henneguya ictaluri is a parasite that causes proliferative gill disease (PGD) otherwise known as hamburger gill disease because the inflammatory reaction within the gill epithelium has the appearance of a hamburger.
Cysts develop along the lamellae of the gills that cause the fish to not be able to … (3 things)
breathe
excrete ammonia waste
osmoregulate
This parasite causes “boil disease” or “tapioca disease” and produces white cysts within the muscle/filet, and thus is economically important because filet will be discarded if this is found.
henneguya salminicola
this parasite has a one-host life cycle and is host-specific. They become external parasites of the gills and skin and cause damage to the epithelium.
monogeneans
Digenetic trematodes (yellow grub, black spot, and eye fluke) cause minimal pathology.
Fish are (intermediate, aberrant, or definitive) hosts. Choose one.
intermediate
arthropod parasites such as argulus, lepeophtheirus salmonis, and ergasilis are crustacean parasites that attach to the skin or gill filaments.
What pathology do they cause?
focal inflammation as the site of the attachment
fungal disease in fish such as saprolegnia and aphanomyces are secondary, opportunistic invaders associated with _______________ or trauma. they cause white to gray cotton like mycelial masses.
poor water quality
T/F: fungal diseases of fish are usually superficial and do not invade the tissue
true
T/F: neoplasia has minimal economic impact of wild fisheries, sport fishing, or aquaculture.
true
fish get most of the same neoplasias that other species get, but its most commonly reported in older fish and a lot of the times, fish arent living long enough in certain settings for this to be a significant issue.
Can you eat a fish that has a neoplastic tumor?
its best NOT to just to be safe.
Differentiate the effect that low versus high concentrations of nitrogenous wastes would have on fish
low – chronic stress and gill pathology
high – acutely lethal
T/F: In order to differentiate between ammonia, nitrite, and nitrate toxicity, you would need to do histology to examine the effect on the tissues.
false – there is nothing histologically that can distinguish. you would need water quality parameters to determine the cause of etiology.
Describe the type of virus associated with ‘San Miguel Sea Lion Virus’ –
RNA or DNA?
enveloped or non-enveloped?
family?
genus?
non-enveloped RNA virus in the family Caliciviridae and genus Vesivirus
T/F: San Miguel Sea Lion Virus is identical to vesicular exanthema of Swine and is reportable
true
T/F: San Miguel Sea Lion Virus is very host specific
false – it has been isolated from a lot of different animals
What are the 2 most common gram negative bacterial aquatic diseases with zoonotic potential?
- aeromonas spp.
- vibrio spp.
what are the 2 most common gram positive bacterial aquatic diseases with zoonotic potential
- streptococcus spp.
- mycobacterium spp.
Which gram negative bacteria causes disease in catfish primarily and can be transmitted to humans via puncture wounds. It causes necrotic skin lesions, gastroenteritis, and meningitis.
edwardsiella tarda
This gram positive bacteria is found in tilapia and striped bass. It is transmitted to humans via wounds or contamination of abrasions. It causes cellulitis, arthritis, and possibly death.
streptococcus spp.
why are mycobacterium lesions on humans usually found on extremities?
mycobacterium prefers cooler temperatures.
This gram positive bacteria is found mostly in tropical fish, but when transmitted to humans causes cutaneous lesions that are very similar to that of mycobacteriosis (cutaneous and limited to extremities).
nocardia spp.
These fungi are opportunistic pathogens and causes cutaneous or systemic mycosis in humans.
exophiala and veronaea spp.
This nematode can be transmitted to humans by eating raw or undercooked freshwater or marine fish. It causes abdominal pain, nausea, and vomiting.
Anisakiasis
