Recognizing Common Signs of Illness in Pet Rodents
<<Vet Med 93:981-987 Nov'98 Review Article 7 Refs
Shawn P. Messonnier, DVM
Paws and Claws Animal Hospital 2145 W. Park Blvd. Plane, TX 75075
- Diagnosing diseases in pet rodents (rats, mice, guinea pigs, hamsters, and gerbils) is essentially the same as in dogs and cats. The differential diagnoses are based on the patient's history and clinical signs as well as conditions common to each species. In this article, I describe common clinical signs in pet rodents and how to diagnose and treat the conditions that usually cause them.
How to administer fluid therapy: Fluid therapy can be vital in treating sick rodents. Fluids can be given subcutaneously, intraperitoneally, or intraosseously. Vascular access in small pet rodents makes intravenous therapy impractical. Intraosseous access is easily accomplished in anesthetized patients (use general anesthesia or local anesthesia in depressed pets) by inserting a spinal needle or a 20- to 22-ga needle into the femur through the trochanteric fossa. Fluids can be given subcutaneously or intraperitoneally at a loading dose before discharging a patient for home care. Any balanced electrolyte solution is practical; lactated Ringer's solution can be administered at 10 ml/100 g of body weight/day for maintenance.
Collecting blood samples: Blood collection is not routinely performed in pet rodents because it is difficult to access peripheral veins in these species and because only a small quantity of blood can be safely removed from a sick rodent. Blood samples can be taken from the nail, tip of the tail, ventral tail artery, ear vein (in guinea pigs), orbital sinus (in anesthetized patients), dorsal vein of the penis (in anesthetized guinea pigs), jugular vein (in guinea pigs), cranial vena cave (in guinea pigs), or saphenous vein (in anesthetized guinea pigs; a cut-down may be needed). Orbital sinus collection has potential complications, and clipping the tail is usually unnecessary. The ventral tail artery is the vessel of choice. In pet rodents, total blood volume is about 6% to 7% of body weight (e.g. 3 to 4 ml in a 60-g gerbil). Up to 25% of this amount can be safely collected every two weeks (ea. 0.9 ml in a 60-g gerbil). Replace blood volume subcutaneously or intraperitoneally with an equal amount of a balanced electrolyte solution.
When a pet rodent dies: Most pet rodent owners are amazed that an animal that seemed healthy the night before can be semicomatose and near death the next day. When a pet rodent dies (or an owner chooses euthanasia), offer a necropsy to ascertain the cause of death and to determine whether a zoonotic disease (e.g. salmonellosis, hymenolepiasis, lymphocytic choriomeningitis), although rare, was involved. Necropsy findings can not only comfort many owners but provide useful information for practitioners.
Differential diagnoses are based on history, clinical signs, and knowledge of conditions common to species.
Handling and physical examination
Pet rodents need special handling and restraint. Lift guinea pigs with one hand under the trunk, and one under the hindquarters. Pick up hamsters by cupping the hamster, holding loose skin at nape, or by gripping over the back. (Hamsters can turn and bite even when held by nape.) To restrain/pick up rats, mice, and gerbils, hold them either at the base of the tail or the nape. Large rats can be held by putting one hand over the back and ribcage and supporting the trunk with the other hand. Immediately release any rodent that struggles. Get an accurate weight, check teeth, and auscult with a pediatric stethoscope.
Common clinical signs
Obtain a history, perform a complete physical examination, and obtain a skin scraping/fungal culture (especially if pruritus present). Skin biopsies (use isoflurane anesthesia) may be more cost effective and diagnostic than skin scraping/fungal culture.
Common causes are mange, ringworm, bacterial dermatitis, cervical lymphadenitis, pododermatitis, lice infestation, nasal dermatitis, and skin cancer
Demodectic mange in older pet rodents