Guinea Pigs, rats and mice

Question 1

Where do guinea pigs get their vitamin D from?

Answer 1

Guinea pigs cannot get any vitamin D through their diet. They rely on spending time outdoors to maintain their vitamin D. Summer at least 30 min. a week outside and winter at least 1 hour minimum.

Question 2

What are the diet requirements for guinea pigs?

Answer 2

Like rabbits they need a high fibre diet, grass and hay should be at least 80% of their diet. Only low calcium veggies as they are also unable to control the uptake of calcium through their diet. (avoid lucerne hay, parsley and kale.
A maximum of 1 tb of pellets per day.

Guinea pigs also need vitamin C in their diet as they are unable to synthesise their own. Vitamin C is found in leafy green veggies, capsicum, carrot and fortified pellets.
If supplying vitamin C through pellets have to ensure that the pellets are stabilised!

Question 3

What is dental disease linked to in guinea pigs?

Answer 3

Low dietary fibre or trauma/infection which is less common.

Question 4

What is tongue entrapment?

Answer 4

Tongue entrapment is the most common form of dental disease where the teeth grow over and entrap the tongue. It is the elongation of the mandibular cheek teeth that eventually trap the tongue.

• 95% of the time this is due to a chronically low fibre diet. Usually occurs between 2-4 years of age

Question 5

What is the treatment for tongue entrapment?

Answer 5

treatment depends on the severity

Mild cases: dietary change
Moderate cases: dental ‘float’ surgery (ongoing) and dietary change
Severe cases: grave prognosis - euthanasia (once the teeth start touching each other)

Question 6

Why do we recommend euthanasia in severe cases of tongue entrapment?

Answer 6

In severe cases of tongue entrapment (where the left and right cheek teeth are touching), guinea pigs can often not chew after surgery.
Because they can’t chew, they rely on their owners to force feed them every 4-6 hours for up to 2 weeks.

Assist feed like Critical Care are liquid and don’t wear down the teeth. The teeth then grow rapidly and guinea pigs usually require repeat dental float surgery 2-4 weeks later.

Question 7

What are the important parts of a physical exam in guinea pigs?

Answer 7

• Must look in the mouth (dental speculum)
• Face (discharge or asymmetry?)
• Jaw and neck (any masses? eg. tooth root abscess, thyroid carcinomas)
• Abdomen (full bladder? ovarian cyst?)
• Lymph nodes (site of fat accumulation which is normal)
• Feet (pododermatitis is very common)

Question 8

Which prophylaxis are important for guinea pigs?

Answer 8

They do not need any routine vaccines, worming, or mite prophylaxis.

However, mites are very common - treat them when present, not as routine prophylaxis.
Mites are usually secondary to immunosuppression, particularly low dietary vitamin C.

Question 9

Is sterilisation recommended in guinea pigs?

Answer 9

yes, recommended as a routine for all male guinea pigs, but not always for females.
- stop unwanted pregnancies and in-fighting
- intact males can develop faecal impaction
- females develop ovarian cysts (about 70% of females over 3 years will have cystic ovaries

Question 10

Is chemical sterilisation (suprelorin, leuprolide) recommended in guinea pigs?

Answer 10

Not recommended!
Can have dysplastic to neoplastic side effects.

Question 11

What can we use to premedicate a guinea pig before anaesthesia?

Answer 11

Premedicate with opioids + ketamine (SC/IM)
- Buprenorphine + ketamine

Also give Glycopyrrolate (potent suppression of saliva production)
- Guinea pigs produce a lot of saliva and this commonly leads to aspiration during anaesthesia

Question 12

What is risky about recovery in a guinea pig?

Answer 12

Recoveries are often risky as hypothermia and inappetence are common.
- ensure active warming during and after surgery
- start assist feeding if they are not eating within 2 hours of surgery (Critical Care food)

Question 13

Which two techniques can be used for castration in guinea pigs?

Answer 13

Scrotal: open castration technique (like a cat), requires post operative AB (TMS) as scrotal abscesses are common.
Preferred technique is abdominal: caudal midline incision, doesn’t require post operative AB.

Question 14

Which technique is recommended for a guinea pig spay?

Answer 14

Flank ovariectomies (only ovary and ovarian duct) - less invasive and rapid recoveries

Question 15

Where do we give subcutaneous injections?

Answer 15

over the thoracolumbar region
not into the neck fat! this can cause necrosis of fat if injected into it.

Question 16

Where do we give IM injections?

Answer 16

Lumbar musculature

Question 17

What is the preferred area for catherisation/venipuncture?

Answer 17

Cephalic vein (mostly used)
Lateral saphenous

Question 18

Where do we give intraosseous injections?

Answer 18

Tibia

Question 19

Why is ileus in guinea pigs severe?

Answer 19

Indicated severe underlying disease or pain.
Affected guinea pigs have excessive GIT gas and are very painful.
- Often need fentanyl and extensive support. (feeding, heating, fluids)
- Must investigate the underlying cause

Question 20

What are the clinical signs of a urinary tract infection in guinea pigs and how do we treat it?

Answer 20

• Haematuria
• Dysuria
• Inappetence
• Abdominal pain

Treatment:
- AB and pain relief
- Urinalysis/sediment exam for Dx
- If it reoccurs, look for the underlying cause such as hindlimb osteoarthritis, poor environmental hygiene, uroliths and crystals

Question 21

Why does urolithiasis occur in guinea pigs (just like it can in rabbits for the same reason)?

Answer 21

Guinea pigs (like rabbits) excrete excess calcium in their urine from:
- High dietary calcium
- Reduced water intake
- Obesity

Question 22

How do we treat urolithiasis in guinea pigs?

Answer 22

No medical treatment, only surgical removal (cystotomy)
- 30-50% of stones reoccur within 6 months of stone removal

Post-operatively
- Long term potassium citrate, diuretics
- Dietary change, exercise

Question 23

Why do guinea pigs get scurvy, what affects does it have on guinea pigs and how do we treat it?

Answer 23

Guinea pigs are unable to produce their own vitamin C - they need daily vitamin C in their diet.
- Vegetables (red/orange veggies and dark leafy greens), stabilised pellets

The lack of vitamin C causes:
- Dental, joint, and skin disease
- Ill-thrift
Their teeth will grow abnormally, break downs of cartilage in their joints, unkempt coats, secondary mite infections

Treatment = give vitamin C (however if they have been without vitamin C for too long and have severe disease - not reversible)

Question 24

How does pododermatitis occur and how do we treat it?

Answer 24

Pododermatitis may be caused by the environment or patient factors
- Hard and abrasive flooring
- Arthritis and obesity
- Can become severe: large infected ulcers leading to osteomyelitis

Treatment:
- Mild cases: change the flooring (fleece)
- Moderate cases: pain relief, bandaging
- Severe cases: surgical debridement, AB, bandaging, pain relief or euthanasia

Question 25

What impacts can mites have on guinea pigs if they are not treated? And how would we treat them?

Answer 25

Causes severe pruritus in immunosuppressed guinea pigs

If not treated, the mites cause:
- Seizure and death
- Chronic weight loss
- Secondary bacterial infections through excoriations

Treatment:
- Revolution (if mild), ivermectin
- Pain relief
- Antibiotics (if open wounds)

Question 26

When do wo usually see ringworm in guinea pigs and how do we treat it?

Answer 26

Seen in immunosuppressed guinea pigs or very young.
Treat with topical antifungals - malaseb shampoo

Question 27

How do we treat bacterial pneumonia in guinea pigs?

Answer 27

Progresses rapidly, treat aggressively!
- TMS/Doxycycline
- NSAID’s, consider mucolytics
- May need probiotics after antibiotic course (GIT dysbiosis)

Bordetella bronchiseptica
- Normal commensal in dogs, cats and rabbits, but serious respiratory pathogen in guinea pigs - don’t house them together!

Question 28

How can we prevent faecal impactions in male guinea pigs?

Answer 28

Castration at a young age is preventative!

• Seen in older, entire male guinea pigs, likely multifactorial. Secondary infections may occur - local yeast, fungal, bacterial overgrowth

Treatment once present: Daily ‘boar cleans’

Question 29

What two types of ovarian cysts are there and how do we treat it?

Answer 29

Very common in mature entire females

Can be functional or benign:
- Functional cysts produce oestrogen (bilateral symmetrical dorsal hair loss, enlarged nipples, uterine neoplasia)
- Benign cysts often don’t cause problems unless they become large

Used to be treated with suprelorin, leuprolide - No longer considered a safe option (risk of uterine neoplasia)

Spey or ovariectomy
- Spey if secondary uterine pathology is present

Question 30

At what age is dystocia likely to occur and why?

Answer 30

Pubic symphysis of sows can ossify at 6-8 months.
- Does not occur if the guinea pig gives birth before this
- Dystocia is common in mature guinea pigs that don’t breed before this

Treatment is caesarean.
- Dystocia is also seen in overweight sows
- Rapid birth is common in normal parturition (2-4 pups born over 30 minutes, born fully furred with open eyes)

Question 31

What does a good diet for rats and mice consist of?

Answer 31

Most: Fresh veggies everyday
Less: Daily oxbow pellets
Least: Fruit, seeds, nuts

Obesity is extremely common - high caloric diets are linked to mammary and pituitary cancers in rodents

Question 32

What should the housing for rats and mice consist of?

Answer 32

• Open wire design - ventilation is important!
• Need hides and shelters and quiet
• No scents, perfumes, candles
• Substrate should be fleece, shredded paper, cardboard

Take care when housing mice together - male mice - no!

Question 33

Should you surgically desex rats?

Answer 33

Sure I mean why not?!
Rats desexed before 6 months have 95% reduced risk of developing mammary cancer.
Both castration and spay can be done from 2 months of age but spays are not considered routine.

Question 34

What is the preferred option for sterilisation in rats?
And what about mice?

Answer 34

Suprelorin (deslorin)
Is becoming more common in rats - lasts 12 months in females and 8 months in males.

Mice: rapid hypothermia prevents any surgery being considered routine

Question 35

Why is pre medication recommended in rats undergoing surgery, and what would be the route of administration?

Answer 35

Isoflurane is distasteful to rats and mice
route of administration: IM (sometimes if no other option, subcut injection)

Question 36

Which drug(s) would we chose for pre med in rats?

Answer 36

Opioid pre meds are common (+/- ketamine)
- Methadone: great analgesia but quite new to rat practice in Australia
- Buprenorphine: not well absorbed subcut (most opioids absorbed better IM). Buprenorphine causes pruritus/increase in rats chewing their sutures and wounds.

Also: really important to keep them warm, hypothermia is extremely common. NSAID’s for recovery (Meloxicam 1.5mg/kg PO SID)

Question 37

Which prophylaxis do we use for rats or mice?

Answer 37

No prophylactic vaccines, worming or ectoparasite treatment - we treat when a problem is present, not beforehand.

Mites are common and lice are occasionally seen - treat with avermectins +/- NSAID’s

Question 38

Where do we do blood draws in rats or mice?

Answer 38

Jugular, cephalic, lateral saphenous, lateral coccygeal veins.

Question 39

How can we give fluids to rats or mice?

Answer 39

Subcutaneous fluids are not tolerated well, rats and mice will bite with SC injections.

Intravenous fluids are preferred (lateral coccygeal vein - place under sedation or anaesthesia.

Question 40

What are 2 common skin conditions in rats or mice?

Answer 40

1. Pruritic alopecia is common (rats & mice)
   - mites are by far the most common cause (treat with avermectins and pain relief)
2. Ulcerative dermatitis (mice)
   - Idiopathic, not infectious
   - early stages can be treated with pain relief, nail trims, omega 3 oils, topical antiseptics
   - Consider euthanasia in moderate-severe cases

Question 41

Why do rats or mice get red-pigmented tears?

Answer 41

They are produced by the Harderian gland (not blood) - is part of the normal immune system’s response to stress or disease
(review environment, diet, disease)

Question 42

What is chronic respiratory disease in rats and mice?

(Know this one well she made a comment during the lecture possibly in exam)

Answer 42

Very common in rats, common in mice

Most caused by Mycoplasma pulmonis
- Commensal organism (get it from mum, all are born with this)
- Immunosuppression causes mycoplasma to overgrow - affected rats/mice start to sneeze

Sneezing -> porphyria -> upper respiratory congestion
- if secondary bacteria/virus become involved in this can progress to lethargy/inappetence -> pneumonia

Question 43

Why is it difficult to identify if the chronic respiratory disease in rats and mice is “just” from mycoplasma or if there is a secondary bacteria/virus involved?

Answer 43

Mycoplasma is always present so culture will always be positive which is normal

Question 44

How do we treat chronic respiratory disease in rats and mice?

Answer 44

Address the cause of immunosuppression
- poor ventilation, hygiene, diet

Avoid antibiotics in early disease
- mycoplasma is a commensal and antibiotic resistance will develop

Can use adjunctive treatments
- NSAID’s mucolytics, bronchodilators and nebulisation

-> Management only (no cure) commonly reoccurs and is progressive

Question 45

What are the causes for mammary neoplasia in rats and mice?

Answer 45

1. High calorie diet
2. Not desexed
3. Pituitary adenomas

Generally very common (mammary chain is very extensive - rapidly growing tumours)

Question 46

What is the rule of thumb for mammary neoplasia in rats and mice?

Answer 46

Rats = Benign
Mice = Malignant

Question 47

How do we treat mammary neoplasia in rats and mice?

Answer 47

Can surgically remove:
- Rats usually recommended as benign
- Mice usually not recommended as malignant
- Recurrence rate is high in both species

Question 48

Which two types of pituitary adenomas can rats get and what are the clinical signs of both? Can we treat them?

Answer 48

1. Functional adenoma - Prolactinoma (the most common form of adenoma)
   - excess prolactin causes mammary enlargement +/- mammary neoplasia
2. Non-functional adenoma
   - cause vestibular signs
   - head tilts
   - trouble holding food with their forelimbs

Can treat if functional: Cabergoline (prolactin blocker)

Question 49

What often causes otitis media/interna in rats or mice and how do we treat it?

Answer 49

Often secondary to chronic respiratory disease (rats)
- bacterial spread through the eustachian tube into middle ear
- most common cause of head tilts

Treatment: Antibiotics and pain relief, head tilts may persist even with successful treatment