Author(s): Debra L. Hickman, DVM, MS, DACLAM ; Katherine Wasson, DVM, DACLAM ; E. J. Ehrhart, DVM, PhD, DACVP 
Hypovitaminosis C (scurvy) or antibiotic-associated enterotoxemia (caused by an overgrowth of Clostridium difficile ) are the major differential diagnoses for a guinea pig with severe lethargy, depression, and diarrhea [1, 2, 3]. Additional differential diagnoses include Tyzzer's Disease (Clostridium piliforme ), salmonellosis, colibacillosis, coccidia (Eimeria caviae ), Bordetella bronchiseptica , malocclusion, heat stress, dehydration, other nutritional deficiencies, and trauma1. We treated the remaining guinea pig (guinea pig #3) with vitamin C (30 mg/kg s.c. daily) and gave it supplemental fluids (Lactated Ringers Solution, 40 ml/kg s.c. daily). We treated the animal for three days with no significant change in condition and found it dead on the fourth day.
We submitted the blood sample collected from the euthanized guinea pig (guinea pig #2) for a complete blood count and a biochemistry panel. The results revealed an increase in the number of nucleated red blood cells and polychromasia, suggesting a regenerative anemia caused by subacute hemorrhage. The leukogram showed an increase in the percentage number of neutrophils without a corresponding left shift, suggesting a chronic inflammatory response. The results of the biochemistry panel were nonspecific. The levels of blood urea nitrogen (BUN) were increased, while creatinine levels were decreased. Because intestinal hemorrhage can cause an increased BUN concentration, we suspected that the hemorrhagic diarrhea seen clinically in this animal caused the elevation. Daily production of creatinine is usually stable and is dependent upon the diet and muscle mass of the animal; anorexia and poor body condition can cause a decrease in creatinine production .
The gross necropsies of guinea pigs #2 and 3 revealed severe diffuse typhlitis, multiorgan ecchymosis, and periarticular hemorrhage with associated soft tissue swelling in both animals. Enlargement of the costochondral junctions was also present. Histological examination of the organs revealed submucosal hemorrhage and congestion with hemosiderin-laden and erythrophagocytic macrophages in the intestinal mucosa of both guinea pigs. Microscopic examination of the proximal colon of the euthanized guinea pig (guinea pig #2) identified areas of mucosal ulceration and fibrinonecrotic plaques. Long, silver-positive rods were associated with the fibrinonecrotic plaques. Anaerobic culture of cecal and colon contents on blood agar isolated a light growth of a Clostridium species that did not exhibit hemolysis. The costochondral junctions had physeal fractures, periosteal and medullary fibrosis, irregular physeal column formation, and a generalized lack of physeal mineralization ( Fig. 1 ). These gross and histological lesions are characteristic of hypovitaminosis C.
We submitted an aliquot of laboratory...