Hyperthyroidism in cats was virtually unknown three decades ago. But it has become common, particularly in older pets. As in people, cats' overactive thyroids can lead to weight loss, rapid heartbeat and other problems.

The increase in feline hyperthyroidism coincides with the advent of flame-retardant chemicals known as PBDEs, or polybrominated diphenyl ethers, in materials like carpet and upholstery padding, plastics and electronic equipment. Researchers Janice A. Dye and colleagues of the Experimental Toxicology group, Environmental Protection Agency, explored possible links between the chemicals and the condition. They analyzed PBDE levels in serum from three groups of cats: young and healthy, hyperthyroid older cats and older cats with other diseases. Because of variability in each group, it was not possible to associate hyperthyroid cats and total PBDE levels. But over all, as just reported in Environ Sci and Tech, 2007, PBDE levels were high in all cats, 20 to 100 times greater than in humans.

This may be because of cats' diets (the researchers analyzed PBDEs in cat food, and found canned seafood flavor food in particular had relatively high levels) and because they spend so much time on or near furnishings. Being meticulous groomers, cats may ingest PBDE-laden dust picked up from couches and carpets.

While more work is needed to explore the link between PBDEs and thyroid activity, it's clear that cats are highly exposed to PBDEs, and thus may serve as a sentinel for understanding the effects of human exposure to the chemicals.

Labrador Retrievers are predisposed to develop chronic hepatitis (CH) that progresses to hepatic failure. The hepatopathy affects middle-aged to older dogs and appears to affect both sexes equally, although an earlier study suggested a female predisposition. Most dogs presented with vague clinical signs such as decreased appetence, vomiting, lethargy, and weight loss, but some (17%) were asymptomatic except for increases in serum liver enzymes.

Twenty-four client-owned Labrador Retrievers were involved in a retrospective study. The median age was 9.3 yrs (range, 3.9–14.0 yrs). Clinicopathologic findings were consistent with hepatic disease. Increases in one or more serum enzyme indicative of active hepatobiliary disease (ALT, AST, or ALP) occurred in all dogs. Biochemical tests of functional hepatic reserve, such as serum hyperbilirubinemia or hypoalbuminemia were abnormal in only 45% and 21% of dogs, respectively. Total serum bile acids, performed in only 4 dogs, were abnormal in 2. Although 87% of the dogs had some ultrasonographic abnormality in the liver, the changes were largely nonspecific and compatible with multiple pathologic processes. Positive copper staining was present in 15 of 17 biopsy specimens. Median survival was 374 d (range, 1-2645 d). Presence of anorexia, hypoglobulinemia, or prolonged partial thromboplastin time were associated with shorter overall survival times. Based on the results of this study, increased serum enzymes represent the best initial screening test for the presence of CH in Labrador Retrievers.

Conclusions and Clinical Importance: A progressive hepatopathy in Labrador Retrievers was marked by chronic inflammation, fibrosis, and copper accumulation. A clinical scoring system that correlates with survival time may be useful as a noninvasive method to predict prognosis.

Reference: Shih et al, J Vet Intern Med 21:33–39, 2007.

The prevalence of bacterial infection in hepatic cultures from cats (14%) was significantly higher than in hepatic cultures from dogs (5%). In addition, cultures from cats were more likely to yield a single bacterial isolate (83%) compared with cultures from dogs, which were equally likely to yield either multiple bacterial species or a single isolate. The higher overall positive culture rate in cats, along with a higher prevalence of single isolates, suggests that hepatobiliary infections may be more common in cats compared with dogs. In a recent study of healthy dogs, positive liver cultures were obtained in 12 of 20 dogs who underwent elective abdominal surgery. Isolates were polymicrobial in about half of these positive cultures. Therefore, it is possible that the positive hepatic cultures obtained in some dogs represented resident flora and were not directly related to hepatic pathology.

Samples of bile, gallbladder, or liver were submitted for culture from 1998 to 2003, including 190 dogs (192 culture episodes) and 58 cats (61 culture episodes).

Biliary cultures for both dogs and cats produced a significantly higher percentage of positive results (30%) than did hepatic cultures (7%). This difference suggests that the biliary system may be more susceptible to bacterial infection or may be a more sensitive site to document hepatobiliary infection. In patients with cholecystitis, 62% (8 of 13) had positive biliary cultures. In patients with hepatic inflammation, 23% (7 of 30) had positive bile cultures, whereas only 6% (6 of 103) had positive hepatic cultures. Escherichia coli, Enterococcus spp., Bacteroides spp., Streptococcus spp., and Clostridium spp. were the most common true-positive isolates. More than 80% of Enterobacteriaceae were susceptible to ciprofloxacin or aminoglycosides, with only 30-67% susceptible to first-generation aminopenicillins and cephalosporins. Liver samples obtained by surgery or laparoscopy were more likely to yield positive cultures than those obtained by percutaneous needle biopsy. Interestingly, in the 22 patients in whom both liver and biliary samples were submitted concurrently, none had a positive liver culture without a positive biliary culture. However, biliary cultures were submitted more commonly in dogs and cats taken to surgery than in those who underwent ultrasound-guided procedures. This procedural difference could have introduced sampling bias in which grossly abnormal biliary tissue was more likely to be submitted for culture.

Reference: Wagner, Hartmann, Trepanier J Vet Intern Med; 21:417–424, 2007.