Chapter 3 Guinea pigs, chinchillas and degus
Hystricomorph rodents are prey animals so some may respond poorly to handling. All of these rodents are likely to struggle vigorously and care should be taken to gently restrain them. Always weigh the rodent at every consultation. The earliest sign of dental disease may be weight loss. Guinea pigs and chinchillas rarely bite, although there are always individual exceptions to this; degus are inclined to bite. ‘Fur slip’ in chinchillas is an anti-predator response whereby stressed individuals will shed clumps of hair while being handled.
Small rodents by virtue of their size and the high risk of predation are forced to obtain most of their water from preformed (food) and metabolic sources. Dehydration can be critical for hystricomorphs rodents, especially at higher environmental temperatures. For an adult chinchilla, 55.5% of its daily water loss is as urine; 16.7% evaporates form its skin; 22.2% evaporates from its lungs and 5.6% is lost in the faeces. Therefore, 38.9% of its water loss is insensible.
Fluids can be given s.c., i.p. or i.o. – indeed if there is marked dehydration, then i.p. or i.o. is preferable to s.c. Fluids can be given i.v. either by bolus or by infusion and all fluids should be warmed to 38 °C. For sites for fluid administration see Table 3.
|Intravenous (guinea pig)||Lateral or medial saphenous and cephalic vein|
|Intravenous (chinchilla)||Femoral, lateral saphenous and cephalic vein. Ear veins can be used for i.v. in some cases, and the use of EMLA cream greatly aids this, but is inappropriate if the chinchilla is considered hypothermic|
|Intra-peritoneal (all three species)||Hold the patient vertically downward and inject into the lower left quadrant|
|Intra-osseous (all three species)||Under GA to insert either an intraosseous catheter or a hypodermic needle into the marrow of either the femur (via the greater trochanter) or tibia (through the tibial crest). Fluids, colloids and even blood can be i.o. if necessary|
Jugular catheterization can be attempted in all species, but it is difficult and may result in respiratory embarrassment. Many of these sites may also require anaesthesia and surgical cut down. In hypovolaemic patients, vascular access may be impossible. It is better to consider either i.p. or i.o. administration.
Use a heat source, e.g. electric heat mat plus insulation such as silver foil (reduces heat lost by conduction) and bubble wrap (reduces heat lost by convection). Pay particular attention to the pinnae of chinchillas as these are significant organs of heat loss. Alternatively, maintain in warm air, e.g. incubator, or use commercial medical warm air generator. If body temperature falls too low, consider the risk of enterotoxaemia following massive gut bacterial die-off.
Many small mammals are presented as emergencies after a prolonged period of ill-health that will have affected their food intake, e.g. chinchillas and guinea pigs suffering from undiagnosed chronic dental disease. These rodents are often hypoglycaemic – testing with a commercial glucometer on a small sample of blood – and i.v. or i.p. glucose can be given to these cases once identified.
Keep the animal warm; as they have a large surface area compared with volume this results in significant heat loss during surgery and hypothermia acts as a general depressant and is also immunosuppressive. Merely applying insulation such as bubble wrap is often insufficient – inactive, anaesthetized rodents are not generating heat and you may be insulating it from a higher ambient temperature. Place these animals onto a heat mat, onto which is placed an absorptive towel or other material to both protect the mat from becoming wet, and reduce the slight risk of localized burns.
Fig. 3.4 Lateral radiograph of a chinchilla with dental disease. Note the divergence of the maxillary tooth roots and the (palpable) bony remodelling of the mandibles associated with cheek tooth root overgrowth.