Rodent Medicine PDF

Rodent medicine Marie Kubiak BVSc CertAVP(ZM) CertAqV DZooMed MRCVS RCVS Recognised Specialist in Zoo and Wildlife Medicine Rodent Taxonomy Order: RODENTIA Suborders: Anomaluromorpha Castorimorpha Sciuromorpha Myomorpha Hystricomorpha Anomaluromorpha (springhares) Castorimorpha Sciuromorpha...

Rodent medicine Marie Kubiak BVSc CertAVP(ZM) CertAqV DZooMed MRCVS RCVS Recognised Specialist in Zoo and Wildlife Medicine Rodent Taxonomy Order: RODENTIA Suborders: Anomaluromorpha Castorimorpha Sciuromorpha Myomorpha Hystricomorpha Anomaluromorpha (springhares) Castorimorpha Sciuromorpha  Squirrels  Ground squirrels  Arboreal squirrels  Prairie dogs  Marmots  Chipmunks  Flying squirrels  Dormice Elodontomas  Seen in prairie dogs and Richardson’s ground squirrels  Uncommon in hystricomorphs and rare in other rodents  Progressive accumulation of odontogenic tissue at incisor apices  Associated with incisor dystrophy  Cause of respiratory compromise and death in some cases  Extraction difficult, consider sinus trephination to relieve respiratory symptoms Hepatic carcinomas  Overrepresented in ground squirrels and prairie dogs  Also identified in California ground squirrels, woodchucks, arctic ground squirrels  Associated with a species-specific hepadnavirus  Immunohistochemistry not commercially available  Link to other soft tissue tumours unknown  Other neoplasms reported  Hepatic adenoma  Giant cell sarcoma  Lipoma  Myelolipoma  Squamous cell carcinoma  Surgical excision where possible Hystricomorpha  Guinea pigs  Chinchillas  Degus  Porcupines  Capybara Hystricomorphs  Typically from arid climates  Herbivores  Hindgut fermenting  Constant eruption of molars and premolars  Large, continuously erupting incisors  Anatomy similar across the suborder  Size varies considerably! Fluid therapy  Intravenous catheterisation difficult  Cephalic vein primary site  Lateral saphenous in chinchillas  Intraosseous catherisation often more appropriate in critical patients  Femur (via trochanteric fossa)  Tibia (via tibial crest)  Sterile technique under anaesthesia  Use spinal needle/hypodermic needle  Ongoing analgesia necessary  ?Prophylactic antibiotic cover  Subcutaneous  Suitable for non-critical patient rehydration  Avoid interscapular fat pad in guinea pigs  Oral fluids  Route of choice for slow rehydration where GIT is functional  Nasogastric tubes tolerated poorly Blood sampling sites  Jugular  Short, thick neck with much s/c fat  Difficult to visualise and restrain for sampling  Cephalic  Small volumes in Guinea pigs and chinchillas  Femoral vein  Distal femoral vein  Small but identifiable visually  Typical sample size of 0.2ml  Blind technique proximally for larger volurmes  Palpate femoral artery pulse and insert parallel and superficical to this  Cranial vena cava  Anaesthesia necessary  Large volumes possible  Useful in small species, debilitated animals Guinea Pig  South American rodent  Herbivorous  Social species  Reach sexual maturity from 4 weeks of age Dental Disease  Similar pathologies to rabbit dental disease and some guinea pig specific!  Different dental anatomy  1 incisor, 1 premolar and 3 molars in each quadrant  Occlusal plane slanted at 30 degrees Guinea pig dental disease  Can be complicated by hypovitaminosis C  Impossible to evaluate dentition fully in the conscious animal  Signs of dental disease Reduced appetite/dysphagia Reduced grooming Weight loss Change in faeces Drooling Ocular discharge uncommon  GA and retraction of soft tissues necessary for complete oral exam  Short fast period useful Objective evaluation  Maxillary apices Rostral end of the nasal bone to dorsal notch of the tympanic bulla (about three quarters of its height)  Occlusal plane Rostral surface of the mandibular incisor (normal length) to the notch of the tympanic bulla Image from: E. Boehmer; D. Crossley: Objective interpretation of dental disease in small mammals, Tierärztliche Praxis Kleintiere 4/2009 Management  Radiographic and coronal assessment of changes  Reshaping and shortening of crowns  Avoid clipping teeth to limit iatrogenic trauma  Gingival resection where necessary  Consider pulpectomy  Only applicable for mandibular pathology  Limited applications  Analgesia  Supportive feeding  Prophylactic Vitamin C Primary incisor pathology rare due to rostrocaudal movements of skull Secondary malocclusion results from cheek tooth elongation Respiratory Disease Often secondary to immunosuppression Concurrent disease Poor husbandry Nutritional deficiency Susceptible to bacterial infections when kept with other species Bordetella and Pasteurella from rabbits Adenovirus related pneumonia in stressed GPs Cystic ovaries  Most common endocrine disease in GPs  Identified in >75% adult females at necropsy  Aetiology unknown  Single/multiple cysts affecting both ovaries  Abdominal distension  Non-specific signs of discomfort  Functional cysts cause non pruritic flank alopecia  Manage surgically Dermatophytosis Typically Trichophyton mentagrophytes Does not fluoresce with Woods lamp 6-14% guinea pigs are asymptomatic carriers Clinical disease presents as Alopecia Non-pruritic scaling Usually face and legs affected  Microscopy/dermatophyte culture  Treat all in-contact animals  Topical enilconazole or miconazole  Oral itraconazole/terbinafine  Oral griseofulvin (25 mg/kg sid for 3-5wks)  Sand bath treatment in chinchillas  Difficult to eliminate in large groups Trixacarus caviae  Sarcoptic mite often present in low numbers  Clinical disease may be precipitated by stress/immunosuppression/hypovitaminosis C  Intense pruritus can lead to self trauma and “seizures”  Abortion/foetal resorption seen in pregnant sows  Diagnosed by deep skin scrapes  0.4mg/kg Ivermectin s/c weekly for 3 weeks  Treat all affected animals in the group and clean housing well Pododermatitis  Secondary to poor conditions  Abrasive flooring  Obesity  Irritants (urine, faeces, chemicals)  Hypovitaminosis C  Inactivity  Erythema, swelling and ulceration of plantar and palmar surfaces  If left osteomyelitis and tenosynovitis can develop  Avascular regions complicate recovery  Address husbandry  Topical and systemic antibiosis  Flamazine speeds recovery  Preparation H  Analgesia  Avoid debridement where possible as contaminated  Prone to relapse Ocular Disease  In a recent study 45% guinea pigs had ocular lesions - Subclinical lens abnormalities - Commonly congenital, often in pigment diluted strains - Cataracts - Fatty/pea eye - Aetiology poorly defined - Tend to affect overweight GPs on inappropriate diets - Heterotopic bone formation - Keratitis - Often related to trichiasis, especially in Rex - Microphthalmos Cystitis  Rule out urolithiasis (often consequence of cystitis)  Consider causative factors  Stress  Dehydration  Reduced mobility (physical/psychological causes)  High calcium/oxalate diet?  Bacterial involvement?  Manage causes as well as consequences  Analgesia  Meloxicam 0.6-0.8mg/kg bid  Nutraceutiacals  PSGAGs  Increased fluid intake Cheilitis  Multifactorial disease  Acidic/abrasive diet  Hypovitaminosis C  Secondary bacterial/fungal infection  ?Pox viral involvement  Manage with antimicrobials based on cytology  Dietary improvement  Topical emollients  F10 barrier cream anecdotally speeds recovery Chinchilla  South American rodent  Crepuscular  Nervous, rarely accept handling well  Handling from early age can improve docility  Vocal  Messy  Require large amount of space Dental Disease  Similar dental anatomy to guinea pig  Occlusal surfaces closer to horizontal  Poor prognosis once roots distort mandibular or maxillary cortices  Caries and coronal fragmentation  Gingival overgrowth  Very sensitive mucosa  Stoic animals – disease often advanced by presentation  Radiographs essential for staging and ensuring adequate correction Dystocia  Under-reported  Only a few anecdotal reports in the literature  Relatively common presentation due to fetal size  Similar approach to larger mammals  Ultrasonography  Manual assistance  Medical treatment  Oxytocin, Calcium  Caesarian/ovariohysterectomy Degu  Under-rated pet  Docile, social animals  Husbandry relatively simple  Care with diet as with any herbivore  Can be kept in single sex/neutered groups Dental Disease  Only situation where clipping cheek teeth may be necessary due to size  Similar pathology to other cavimorph rodents  Diet major factor  Can tolerate mild-moderate changes better than other herbivorous rodents Diabetes mellitus  Transient hyperglycaemia common in older degus on inappropriate diet  Sugary foods (fruit, raisins, carrots)  High concentrate levels  Select high sugar foods above all others  PU/PD and cataract formation seen  Normoglycaemic by time of presentation  Fructosamine often within normal range Persistent hyperglycaemia less common Spontaneous amyloidosis of islets ?secondary to cytomegalovirus Elevation of fructosamine Controlled with dietary modification No reports of insulin dependent cases Myomorphs  Mice  Rats  Hamsters  Gerbils  Lemmings  Voles  Jerboas  Mole rats Fluid therapy  Intravenous catheterisation difficult  Lateral tail veins and femoral vein can be used in rats  Jugular catheters poorly tolerated  Intraosseous catherisation often more practical  Femur  Tibia  Subcutaneous  Suitable for non-critical patient rehydration  Restraint can be difficult  Up to 2.5% patient weight given  Oral fluids  Route of choice for slow rehydration where GIT is functional  Most tolerate syringe feeding well  Baby food/veterinary products suitable Blood sampling sites  Lateral tail vein in rats/mice  Femoral vein  Visible in rats distally  Blind technique under sedation/anaesthesia  Cranial vena cava  Site of choice in small rodents Dental disease  Rarely a problem in myomorphs  Molars are permanent  Occasionally caries seen on poor diet  Incisors may malocclude following trauma  Regular burring under anaesthesia  Surgical removal N.B. some mobility is normal in lower incisors – this is most marked in hamsters Rat  Docile  Adapt well to captive conditions  Simple husbandry requirements  Descended from lab strains  Prone to neoplasia  Carry viral/bacterial infections  Short lived Rat respiratory disease Most common presentation Wide spectrum of disease Aetiology Mycoplasma pulmonis Strep pneumoniae CAR bacillus, Corynebacterium kutscheri, Sendai virus, coronavirus, pneumonia virus Predisposing factors: • High ammonia levels, aerosols, stress, concurrent disease Diagnostic approach  History and clinical exam • Sneezing, nasal discharge, tachypnoea, “rattling”, head tilt, reduced “thoracic spring” • Porphyrin staining, anorexia, weight loss, hunched posture, ruffled coat, lethargy • Screen for underlying disease  Culture (nasal/tracheal swab or BAL)  Mycoplasma pulmonis PCR, corynebacterium serology  X-rays? • Prognosis Treatment Early treatment essential! Antibiotics • Fluoroquinolones • Macrolides • Tetracyclines • e.g. enrofloxacin 10 mg/kg PO SID • e.g. azithromycin 20 mg/kg PO SID • e.g. doxycycline 2.5-5 mg/kg PO BID Treatment Anti-inflammatories • Meloxicam 1 mg/kg PO BID Mucolytics • Bisolvon pinch on food SID Bronchodilators • Salbutamol 100 µg / rat q4-6 h or as needed Nebulisation • Dilute F10 (2 ml in 500 ml saline) Treatment *** Husbandry *** • • • • • Reduce ammonia: ventilation and cleaning Reduce stress Correct diet Increase activity and weight loss? Isolation?? Neoplasia  Pituitary adenomas common  Typically in elderly, obese female rats  More common in cases with chronic respiratory disease  Neurological signs  Ataxia  Poor forelimb co-ordination  Head tilt  Proprioceptive deficits  Sudden death  Differentiate from otitis media due to chronic mycoplasmosis  Prognosis grave  Consider cabergoline therapy Ectoparasites  Rarely a primary problem  Accumulate in debilitated rodents  Treat underlying cause  Injectable ivermectin  0.4mg/kg s.c  Life cycle of rat mites usually ~21days  Multiple treatments needed Hamster  Crepuscular burrowing rodents  Omnivores  Grain, fruit, vegetables, occasional insects  Can be very defensive!  Aim to meet physical and psychological requirements  Climbing  Burrowing  Exercise  Hibernate at low temperatures Syrian hamster 100-180g Campbell's hamster 20-35g Roborowski hamster 20-25g Siberian/ Djungarian hamster 25-45g 2-2.5years 1.5-2 years 3-3.5 years1 1.5-2 years 2-2.5years 37-38C 275-450 NR NR NR NR NR NR 37-38C 275-425 60-250 NR NR NR 70-180 4 days 18-20days 4-6 days 20-22 days 4 days 18-25 days 4-5 days 18-21 days Litter size 4 days 15-18 days 3-12 (typically 46) 3-9 (6) 1-9 (4-6) (4-6) Sexual maturity 40-70 (female) 70100 (male) 1-9 (7-8) from 30 days, typically 60 days for females from 30 days from 30 days from 30 days Adult weight Longevity Body temperature Heart rate Respiratory rate Oestrus cycle Gestation Chinese hamster 30-45g Kubiak, M., 2020. Hamsters pp.83-98 in Kubiak, M. ed., 2020. Handbook of Exotic Pet Medicine. John Wiley & Sons. Wet Tail  Bacterial enteritis  Lawsonia intracellularis  Clostridum spp.  Parasitic  Hymenolepis tapeworm *ZOONOTIC*  Giardia  Oxyurids  Most commonly seen at times of stress  Weaning  Change of home  Presents as  Profuse watery diarrhoea  Ventral staining  Weakness  Inappetance  Can lead to rectal prolapse  Differentiate from vulval discharge in female hamster post-ovulation  White discharge  Clinically well hamster  Aggressive antibiotic and fluid therapy Hyperadrenocorticism  Adrenal gland normally 2-3 times larger in males  14.5% incidence of hyperplasia and neoplasia at necropsy  Usually incidental finding  Males more commonly affected by pathology  Clinical signs include  PU/PD  Polyphagia  Hyperpigmentation  Alopecia  Pendulous abdomen  Diagnosis  Ultrasound  Post-mortem  Urine cortisol:creatinine  Radiography may demonstrate mineralisation  Blood volumes required for tests are limiting factor  ALP >40 U/l (normal range 8-18U/l) Treatment  Poor response to mitotane  Variable response to metyrapone  5-10mg sid for 30 days  Lack of sufficient data  Ketoconazole is believed to prolong survival  5mg/kg bid po  Supportive treatment for secondary skin infections  Surgical treatment has very low survival rates Neoplasia  Skin neoplasia most common  Soft tissues sarcomas seen in older animals  Adenocarcinomata  Oral/pouch glands  Flank scent glands  Gastric mucosa Epitheliotrophic lymphoma (mycosis fungoides)  Seen in older hamsters  Anorexia and weight loss  Exfoliative dermatitis  Scabbing and alopecia  Concurrent demodecosis  Variable pruritus  Biopsy/impression smears  Chemotherapy generally unsuccessful  Palliative corticosteroid therapy  Euthanasia Hamster polyoma/papova virus  Oncogenic virus of Syrian hamsters  Common in lab situations  Up to 50% affected  Young hamsters develop multicentric lymphoma  Older hamsters develop epithelial lymphoma or trichoepitheliomas  Euthanase affected hamsters  Beware subclincal carriers  Incubation period can be up to 18months Gerbil  Non-aggressive  Sociable – tolerate human handling well  Conserve fluid, little waste/odour  Active throughout the day  Destructive  Can live in groups if sufficient space provided Harderian gland secretions  Appears as nasal dermatitis  Increased secretion with stress  Humidity >50%  Secondary infection with commensal or opportunistic microbes (usually Staphylococci)  Treat bacterial colonisation  Address husbandry factors Mice  Short-lived  Social animals that can adapt to handling Murine dermatitis complex  An often frustrating condition  Presents with severe pruritus and self-trauma  Typically affecting the dorsal neck  Multifactorial  Parasitic  Contact irritation  Hypersensitivity  Stereotypical self-trauma  Frequently exacerbated by secondary infections  Diagnostics  Skin scrapes and hair plucks  Cytology  Microbiological culture  Therapy  Antimicrobials and antiparasitics as necessary  Systemic anti-inflammatory therapy  Trial exclusion diets  Increase stimulation  Slow feeding e.g. foraging enrichment, stones in bowls  Increased handling  Companions  Difficult to restrict self trauma with physical barriers Mammary neoplasia  >80% malignant  Benign neoplasms secondary to retrovirus  Murine mammary tumour virus  Transmitted vertically in milk or in genome  Oestrogen sensitive  Expressed in females of reproductive age  ?Zoonotic potential