NTCA medicine - small mammals (rodents) Flashcards
How are ‘rodentia subgrouped?
- The Caviomorpha
→ guinea pig, chinchilla,
and degu - The Myomorpha
→ “rat like” or “mouse
-
like” rodents. - The Sciuromorpha
→“squirrel
-like”
rodents.
Who is in the Muroidea ?
Muridae -> gerbils, old world rats and micr
Cricetidae -> true hamsters
What different Rats are there?
- Brown rat -> rattus norvegicus
- ## Giant Gambian Pouched Rat
Mice ?
Mus musculus from the wild mouse
- Nocturnal
- Omnivorous
- Male -> strong odour
Key features of Mice?
Common hamsters?
Golden or Syrian hamster (Mesocricetus auratus), the Russian hamsters
(Djungarian - Phodopus sungorus
Gerbil species?
Mongolian gerbils → Meriones unguiculatus.
Info about gerbils?
- Originate from dry sandy grasslands → adapted to a desert environment → produce most of their water
requirement from metabolic processes - Burrowing diurnal rodents and are active at dusk and dawn.
- Highly sociable
Key features of gerbils?
Guinea pigs main info ?
● Average longevity 4–8 years
● Respiratory rate 40–120 bpm
● Heart rate 226–300 bpm
● Body temperature 38–39.5°C
● Maintenance fluid therapy →100–150 ml/kg/day
● Sexual maturity → 4–6 weeks female, 9–10 weeks male
● Gestation 59–72 days
Assessing pain?
● Absence of normal behaviour
● Porphyrin staining (‘red tears’
– rats)
● Hunched?
● Hiding?
● Rubbing at affected area? Belly pressing?
● Contractions of abdominal muscles?
● Loss of appetite?
● Change to HR, RR and depth
SC injecitons?
→ between
the scapulae, back or abdomen.
- Hamsters→ care not to inject into the
cheek pouches - Large volumes → painful
IM injections?
- Challenging due to the small
muscle mass. - Painful
- Quadriceps
- Gluteal muscles
Vasculature / venipuncture?
● Circulating blood volumes in rodents is
approximately 5-8% of bodyweight.
○ Keep sample volumes to the minimum
○ Consider potential blood loss
○ Consider haematoma formation.
What blood sampling sites?
○ Lateral saphenous vein
○ Cephalic vein – My vein of choice in g pig!
○ Jugular vein
also lateral tail vein in rats, mice and gerbils (care degloving!)
Describe tail venipuncure
- The tail has lateral veins in the 3 o’clock and 9 o’clock positions
- Can be visualised at the base of the tail.
- In the rat, may be carried out conscious
- Apply EMLA (local anaesthetic cream)
- Warm the tail → may aid in vasodilation.
Gingival vein sampling?
- Gingival vein sampling → described as an easily accessible site for blood collection.
- Hamsters, guinea pigs, rats and mice → collect under a brief general anaesthetic
- In a recent paper, it described that even repeated sampling had no effect on food intake,
bruising or haematoma formation.
Cranial VC sampling?
- Caution with this site
- Cardiac tamponade
- Laceration of the cranial vena cava
- Puncturing the heart
- Performed under a general anaesthetic
- Insulin syringe
- Sample at the thoracic inlet
- Direct the needle caudally at a 30-degree angle off
midline and toward the opposite hind leg - Needle very close to the heart!
Anatomical features of rodent dentition?
- Large, continuously growing, paired, mandibular and
maxillary incisors. - Chisel-shaped occlusal surface.
- Labial surface is composed of hard wearing ename
Incisors have …?
open apical pulp cavities → are constantly
growing → elodont (elongating, continuously growing, teeth)
Incisors are..
aradicular (no roots)
T/F rodents have canines
False
Rodents are monophyodont & simplicidentata - what does this mean ?
Monophyodont -> develop nly one set of teeth through life
Simplicidentata -> 1 pair of maxillary incisors (no peg teeth)
What feature of rats mandibular symphysis ?
MOBILE & visible at the lower incisor teeth -> significant separation of the lower incisor teeth at tip
How rapidly do incisors grow?
2-4 mm a week
Rodent incisors?
longer than the maxillary incisor crowns
→ crown to length ratio for the upper to lower incisors is approximately 1:3 in rats and hamsters.
Fractures common
What teeth do myomorphs not have?
premolars
Dental formula of myomorphs?
2 * [ I1/1, C0/0, P0/0, M3/3] = 16 teeth
Features of myomorph teeth?
- Anelodont molar teeth →they are truly rooted, with a limited growth period.
- They are brachydont → short crowned.
- Cusps on the occlusal surface (hamster and rat, not the gerbil).
- The molar teeth are also referred to as cheek teeth.
How do the teeth interact when eating?
- Each mandibular cheek tooth is in occlusion with the corresponding maxillary cheek
tooth when chewing. - When gnawing with the incisors, the mandible is pulled forward and the maxillary and mandibular molars are not in occlusion.
Hystricomorphs dental formula?
2 * [ I1/1, C0/0, P1/1, M3/3] = 20 teeth
Hystricomorph dental features ?
- Hypsodont → long crowned teeth
- Elodont → continuously growing cheek teeth as well as
incisor teeth - Aradicular → no anatomical roots
- Anisognatism → wider mandible
- Cheek teeth normally at 30° occlusal plane
What client concerns may indicate dental dx?
● Reduced appetite, to anorexia ● Dysphagia ● Ptyalism/hypersalivation ● Droppings smaller and less
frequent
→ none produced
● Incisor malocclusion ● Facial swellings ● Overgrown or changes to
incisor teeth
Diagnostics of dental dx?
● Clinical exam →palpate the mandible &
ventral neck carefully. Look for
oculonasal discharge, check for facial
asymmetry, check for exophthalmos
● Conscious oral exam → otoscope →
challenging → we may miss up to 50%
of cases! Perform last.
● Oral examination under
sedation/anaesthesia
● Stomatoscopy
● Radiography
● Advanced imaging
○ CT
○ MRI
KEY POINT
Osteoarthritis of the temporomandibular joints will cause secondary dental
disease due to pain caused by chewing.
● Osteoarthritis of any joints may cause secondary dental disease due to a decrease in
appetite → dental disease seen in an older guinea pig is often SECONDARY to underlying
issues. MULTIMODAL ANALGESIA IS ESSENTIAL.
GI hypomotility happens when?
a primary condition or secondary
to virtually any other disease process causing pain.
Bloat ?
may occur secondary to GI hypomotility or as a primary
issue post-ingestion of fermented food or an excess of leaves
from the brassica family.
CLS of bloat?
abdominal distension, dehydration, reluctance to move.