VETM4480 - Comparative Medicine - Final Exam

Structure of fish skin

- Scales are under the epithelium (scales are NOT part of the epithelium!)

- Skin acts as an osmotic barrier (stops water from rushing in)

- Easily disrupted - when handling keep fish wet and have on something soft and smooth

- Bacteria spreads easily in secondary vascular membrane

Fish skin lesions are

A disruption of the osmotic barrier - water moves into the fish (imbibition) causing osmo-regulatory, disturbance and tissue necrosis. Skin lesions are common and easily recognized.

Structure of fish gills

- Delicate - one or two cells separating the water from blood. This allows for efficient O2 exchange but any epithelial damage can cause significant disease with few visible signs.

- Water O2 is 6-7% (air is 21%)

- They are NOT involved in hematopoiesis

Fish urogenital system

- 1 or 2 kidneys depending on species (always retroperitoneal)

- The swim bladder is present in most fish and lies ventral to the kidney

- Swim bladder is involved in buoyancy and abnormalities produce fish that cannot swim/float properly in water

Which two tissues do you culture in fish

***likely exam question***

Kidney and spleen (if you were to culture a third tissue: heart)

Fish spleen

A major filtration organ and secondary lymphoid organ (fish do not have lymph nodes and lymphatics)

Fish heart

- Three chambered

- More commonly involved in infectious disease than in mammals

Fish liver

The liver is not a true filtering organ and is a poor choice for culture

Common fish eye lesion

Exopthalmos (eye bulging) - the choroid rete behind the eye traps air bubbles and bacteria. If bilateral consider a bacterial cause

What is the lateral line

A canal embedded in modified scales lined by a sensory epithelium called neuromasts - these cells most important function is to sense water pressure changes.

What is a possible result of nutritional deficiency in fish

Kyphosis and scoliosis - if you see unusual lesions, when in doubt, change feed!

Two organs in fish responsible for hematopoiesis

1. Kidneys

2. Spleen

Golden rules of water quality

- Change is bad and quick change is worse

- Overfeeding, overstocking, lack of/improper maintenance and management problems kills more fish than any disease combined

- The bigger the volume of water, the less it changes

- Ammonia is oxidized to nitrite, which is oxidized to nitrate

- Oxidation is preformed by gram negative bacteria in the biofilter (antimicrobials will kill the biofilter)

Required water test kits for fresh water and salt water

Fresh water: ammonia or nitrite

Salt water: ammonia, nitritie, pH, salinity

Characteristics of water temp on fish health

- Each species has a preferred range

- Temp extremes are where toxicity/morbidity occurs

- Temp stress can be induced by continual variation

- The higher the temp, the lower the oxygen

Oxygen requirements for fish

- Movement at the water/air interface allows gas exchange

- Aeration provides gaseous exchange

- The bacteria that oxidize ammonia require oxygen

- Signs of hypoxia are 'pipping' or 'arrowhead'

- Gas bubble disease is analogous to divers' bends in people

What is the least toxic: ammonia, nitrite, nitrate

Nitrate

What produces ammonia

- Uneaten food

- Excretion from fish

- Dead plants and animals

Function of tank filtration systems

- Oxidize ammonia to nitrates

- Nitrates are then removed by water changes

- Sub optimal nitrogen cycle leads to debility, death and immunosuppression

What does excess nitrate cause

Methemoglobin in blood aka brown spot disease - may see brown blood on gills

- Fish recover well

- Solution is to clean out the tank or add salt

- Chloride competes with uptake of nitrate

What is salinity

Amount of dissolved salt in water, expressed as parts per thousand or specific gravity. Can be reduced for marine fish to save energy but invertebrates cannot tolerate this.

How to help fish that have lost ions due to epithelial damage

Aquarium salt (non iodized) or marine salt is added

Issue with chlorine in fish

Acutely toxic to fish (cause branchial necrosis), but many city water sources are treated for it. Pre treatment of water with products containing sodium thiosulfite or similar compounds removes chlorine.

What does light do to fish

Can cause retinal damage and blindness - especially for benthic species accustomed to low light

Aeromonas hydrophila in fish

- Bacteria

- Causes ulcerative lesions, reddening at the base of fins and scale pockets and internal petechial hemorrhage

- Macrophages are often full of bacterial rods on histo

- A problem in cyprinids (koi, goldfish) in the spring when the water temperature rises

- Treat with antimicrobials

Mycobateriosis in fish

M. marinum, M. fortuitum, M. chelonae (and others...)

- Any chronic ulcerative or proliferative lesion (ex. granulomatous) that does not heal despite treatment could be neoplasm or more likely, mycobacteriosis

- Usually multiple acid-fast rods within lesions on histo

- Super common, you should assume all tanks are infected (although not all tanks will have clinical disease)

- No good treatment

- Zoonotic risk in immunocompromised people (called fish finger) - limited to surface, does not invade systemically

Flavobacterium columnare in fish

- Bacteria

- Causes columnaris disease (bacteria causes 'columns')

- Very common disease

- Only occurs above 15˚C

- Causes a cotton-wool appearance or ulcerative/necrotic lesions

- Oral lesions can be slight, but can cause death

- Treat systemically and need to deal with surface lesions (no blood supply to necrotizing surface lesions, so systemic antibiotics will not reach it)

Diagnosing Flavobacterium columnare in fish

Wet mounts of the skin or gill

Icthyophthirius multifilis/cryptocaryon irritans (marine version) in fish

- Parasite

- Causes 'white spot'

- Each white spot is a protozoan maturing under the epithelium

- Rupture of the epithelium is the primary cause of morbidity and mortality - rupture causes osmo problems and secondary infections

Treating Icthyophthirius multifilis/cryptocaryon irritans in fish

- Topical treatment is not effective against the mature parasites under the epithelium - the immature encysted tomite in the aquarium is responsive to treatment with topical agents. This is the exception to the 'treat the fish not the tank' rule.

- Protozoa are limited to either fresh water or salt water, not both

- Fresh water dips for 3-5 mins can treat cryptocaryon irritan in marine fish and salt water dips can treat icthyophthirius multifilis in fresh water fish

Monogentic trematode infection in fish

- Parasite

- Common in fresh and salt water fish

- Problem in koi ponds

- In large numbers cause severe skin damage and death

- They have a fearsome haptor (tail end) to hang on with mouth parts at the opposite end to graze epithelium - live on outside of fish

- Must treat the environment to get rid of it

Metacercaria of digenes infection in fish

- Parasite

- Causes 'black spot'

- Harmless to fish

- Seen in pond fish or those from the wild

- The black pigment is melanin

- Spots may never go away, no need to treat

Fungal disease of note in fish

Saprolegnia spp. (very common) - invasive and can be difficult to treat

Cause of cataracts in fish

Zinc, riboflavin deficiency (cloudy eyes can also be due to corneal opacity)

Non infectious issues in fish

- Bird strike

- Bloat/dropsy

- Neoplasia

- Trauma

- Electrocution

Neoplasia in fish treatment

Resect if possible

Things that end up in fish from pollution

- Acetaminophen

- Ibuprofen

- Estradiol (estrogen)

Disease prevention principles for fish

- Quarantine all new fish

- Prophylactic rx regime

- Have a treatment tank

- Proper water quality

- Cleanliness/disinfection

- Resistant fish - species, strain, population mix

- Stocking density should be appropriate

- Good feeding practices

- Good record keeping

- Minimize fluctuations in any parameter, but especially temperature

Golden rules of treating fish

- Treat the fish not the tank (exception: white spot/ ich/cryptocaryon, amyloodinium, monogenes)

- Pay attention to species variation

- Recommend commercial medications for which an active ingredient is on the label

Treatment routes for fish

1. Topical (aka bath, dip, flush, painting) - most common treatment sold at stores

2. Oral

3. Parenteral - used less commonly, cannot inject muscle of a fish because they are designed to keep water out, so it will just come out. Have to inject into the peritoneum

Topical/bath options for treating fish

- Dylox and similar chemicals

- Hydrogen peroxide

- Copper sulphate (marine tanks) - toxic to invertebrates

- Formaldehyde/formaline

- Potassium permanganate

- Fresh water/salt water

- Malachite green/other dies

- Antibiotics (for a treatment tank)

Carbon/charcoal/zeolites will remove therapeutants

Formaldehyde/formalin treatment for fish

Formaldehyde is 10x the concentration of formalin:

- Used widely for cold water species

- In combination with malachite green this is the most broad spectrum, readily available topical treatment

- In water precautions are required, it drops the dissolved oxygen

- Volume of water accurately calculated to be able to do this

-Monitor fish throughout the treatment period and be prepared to remove the fish/decrease concentration

- Aerate the water

- Try a test fish - beware of species variation

Fish treatment best practices

- Treat in treatment tank (some exceptions)

- Proper diagnosis

- Single treatment

- Appropriate drug delivered by an appropriate route

Why are topical medications not the best for fish?

- Fresh water fish do not drink and do not take up sufficient amounts of water across their gills to be effective in most cases

- You won't know the tissue concentrations achieved

- Salt water fish drink but not enough for drug delivery

- Many drugs also precipitate in hard/salt water and require higher dosages if used in a bath

- Oral or sometimes parenteral routes are usually preferred

Considerations for oral fish treatment

- Incorporated into feed (fish slurry) best way to go

- Top dress or mixed at manufacture

- Issue: many sick fish don't want to eat

- Palatability

- GI absorption variable with temperature

- Excretion often poorly understood - therefore tough to dose accurately

Still the best choice for systemic bacterial infections

Considerations for parenteral fish treatment

- IP or IM infection

- Useful if treating a single or a few fish

- Many sick fish don't eat - so this is a good route

- Tissue damage can occur

- Dose difficult but nephrotoxicity not a concern like in mammals

- Impractical/expensive on a large scale

Best for single time treatment options

Small mammals belong in what super class

Tetrapoda

What characterizes rodents

A single pair of continuously growing incisors in each of the upper and lower jaws - about 40% of small species are rodents

What characterizes lagomorphs

Two pairs of incisions in the upper jaw, a single pair in the lower jaw and all their teeth are continuously growing - they are strictly herbivores. Also have no paw pads.

What is the only domesticated rabbit species

Oryctolagus cuniculus or the European rabbit/old world rabbit - includes many breeds (holland lop, lion head, mini lop, mini rex, dutch, etc.)

Guinea pigs in the wild

Do not exist!

Skinny pig vs baldwin guinea pig

Skinny pigs are born hairless, baldwins shed out with age

Two species of chinchillas

1. Short tailed chinchilla (chinchilla chinchilla)

2. Long tailed chinchilla (chinchilla lanigera)

Characteristics of hamsters

- Large cheek pouches

- Thick bodies

- Short tails

- Excess of loose skin

Common pet species of hamsters

- Cambell's darwf hamster

- The winter white dwarf hamseter

- The roborovski dwarf hamser

- Chinese hamster

Characteristics of rabbits

- Prey (flight)

- Obligate herbivore

- Crepuscular (active at twilight)

- Terrestrial and fossorial (live in burrows under the ground)

Characteristics of rabbit skin

- Delicate skin

- Fine hair

- Tactile vibrissae

- Dewlap in intact females

- No foot pads

- Coarse fur

- Scent glands - chin, anal and inguinal

Characteristics of rabbit musculoskeletal system

- Delicate skeleton and light weight

- Strong epaxial muscles for kicking off, fracture at L7 common

- Large tympanic bullae

Rabbit eyes

Large, lateral -> panoramic field of vision, rarely blink (2-4 times an hour)

What is the tragus in rabbits

A vertical ear canal

Proper rabbit diet

- Consume lots of high fibre (14-20%, abrasive and low energy foods (can eat straight hay) such as grass or timothy hay

- Minimal high fibre pellets

- Moderate amount of fresh dark leafy greens

- Avoid high Ca++/oxalates

- No or only occasional treats

Rabbit dental formula

2 x (I2/1 C0/0 PM3/2 M3/3)

(4 upper incisors - only 2 in rodents)

Aradicular teeth in rabbits

- No roots

- Divided into clinical crowns and reserve crowns

Hypsodont teeth in rabbits

High clinical crown

Lophodont teeth in rabbits

Transverse enamel ridges to grind down food

Elodont teeth in rabbits

Continuously growing:

Incisors: 8-10 mm/month

Molars: 4 mm/month

Intestine in rabbits

- Hind gut fermenters

- Marked Ca++ absorption

Structure:

- Stomach (15%) - 9 days to empty

- Small intestine - short

- Sacculus rotundus - junction between the ileum, cecum and proximal colon

- Cecum (60%) - ampulla coli, long spiral fold, vermiform appendix

- Colon - proximal - fusus coli, distal

Function of fusu coli

Pacemaker, controls peristalsis:

- Large fibres: hard, dry feces (1-4 hours)

- Small fibers: retropulsed into cecum, fermentation -> softer, light cecotrophs/cecotropes (4-8 hours later)

Respiratory system of rabbits

Obligate nasal breathers

Lymphatic system of rabbits

- Large persistent thymus

- Small spleen

Urogenital system of rabbits

- Calcium excretion is very high

- Urine is cloudy due to calcium carbonate monohydrate and ammonium magnesium phosphate precipitates. Can be orange-red from porphyrin diet

- Males have open inguinal canals

- Females have two uteruses with two cervices, and are induced ovulators

Characteristics of guinea pigs, chinchillas and defus

- Prey animals

- Mainly herbivores

- Nocturnal/dinural

- Terrestrial and fossorial

Skin of guinea pigs and chinchillas

GP: androgen dependent sebaceous gland, esp on dorsum. Coccygeal gland; perineal sac, oily fluid, skin debris and hair

C: dense fur, long layered colours, slip

Both: hairless foot pads, tactile vibrissae

Guinea pig musculoskeletal system

- Pelvic symphysis may ossify by 6 months (breed before this to lower risk of dystocia)

- Have delicate skeleton, separate fibula and tibia and an os penis

Diet for guinea pigs

- Herbivores

- High fibre diet, no L-gulonolactone oxidase and require vitamin C (L-ascorbyl-2-polyphosphate is the stabilized form of vitamin C)

- Unlimited grass hay

- Commercial pellets

Chinchilla diet

- Herbivores

- High fibre diet

- Also eats insects

- Unlimited grass hay

- Commercial pellets

- Important to have high fibre and low sugar

Palatal ostium in guinea pigs and chinchillas

Fusion of the soft palate to the base of the tongue - highly vascularized and easily traumatized

GI system of guinea pigs and chinchillas

- Hind gut fermenters

- Simple large intestine

- Fecal pellets (GP all day and night, C only at night)

Guinea pig lymphatic system characteristic

Corticosteroid resistant

Urogenital system of guinea pigs and chinchillas

Chinchillas:

- Elongated renal palpilla (desert animals)

- 100 fold range in concentration - can survive water deprivation for 2 weeks

Guinea pigs:

- Urine is thick and cloudy, white/yellow, crystals

Respiratory system of chinchillas and guinea pigs

Both obligate nasal breathers

Female genital system in guinea pigs and chinchillas

Guinea pigs:

- Bicornuate uterus with 1 cervix

- Relaxin-induced softening of pelvic synthesis during pregnancy

- Vaginal closure membrane

- Spontaneous ovulators

Chinchilla:

- Bicornuate uterus with 2 cervices

- Cone shaped urogenital papilla (looks like a penis)

- Vaginal closure membrane

- Spontaneous ovulators

Male chinchilla genitals

Open inguinal canal, no true scrotum

General characteristics of rats, hamsters, gerbils, and mice

- Prey animals

- Often nocturnal

What is the chromadacryorrhea

Harderian glands and porphyrin produce red tears in rats, mice, gerbils and hamsters

Diet of rats, mice, gerbils, and hamsters

- Often omnivorous

- Fed commercial pellets, very limited fresh foods and seeds/fruit/cheese as treats

Teeth of rats, hamsters, gerbils and hamsters

Only incisors are aradiculor elodont (lower are longer than upper)

Rat hepatobiliary system

They have no gallbladder

Respiratory system of rats, mice, gerbils and hamsters

Obligate nasal breathers

General characteristics of ferrets

- Predators

- Carnivores

- Nocturnal

- Terrestrial and fossorial

Skin of ferrets

- Heavily seasonal shed (spring and fall) - clipped hair won't grow back quickly

- Active sebaceous glands - musky, yellow/orange oil

- Anal gland - often removed when 5-6 weeks old

Eyesight of ferrets

Poor eyesight (but great sense of smell)

GI system of ferrets

- Simple - no cecum or appendix

- GI transit time is 3-4 hours

- Pancreas is V shaped

- Can vomit (unlike rabbits and rodents)

Spleen of ferrets

- Marked enlargement is common - benign extramedullary hematopoiesis (usually not worrisome)

- Sequestration of blood with anesthetics

Endocrine system of ferrets

Adrenal glands:

- Right near caudal vena cava

- Female: both are 5-10 mm

- Male: left one is smaller than right

Female urogenital system of ferrets

- Bicornuate uterus

- Single cervix

- Vulva can become swollen

- Persistent oestrus March-August

- Induced ovulators

- Hyperestrogenism is extremely common in female ferrets - leads to bone marrow suppression

General characteristics of sugar gliders

- Marsupial

- Omnivorous

- Nocturnal

- Arboreal

- Metabolism: 2/3 placental mammals, cloacal temp < body temp

- Patagium (piece of skin stretches across limbs that allows them to glide)

- Pouch: female, little to no epipubic bones

Scent glands in sugar gliders

Frontal (M)

Glular (M)

Paracloacal (M > F)

General characteristics of hedgehogs

- Herbivorous (mainly insectivorous)

- Nocturnal

- Terrestrial

- Metabolism - torpor if excessively hot or cold

- Have spines that are keratinous, hollow, follicles within skin (not quills)

- Mantel and curling (can go into a ball)

Diet related medical issues we see in rabbits/rodents

- GI stasis from lack of fibre

- Obesity (high fat)

- Renal insufficiency

- Urolithiasis (too high Ca++)

- Osteoprorosis (hamsters)