The Silent Killer: Atherosclerosis in Pet Birds

Risk factors Suggested risk factors for atherosclerosis in birds include age, gender, species, increased plasma concentrations of lipids and lipoproteins, high energy diets, physical inactivity, genetics, and coinfection with Chlamydia psittaci. Age Increased age has been shown to be a significant risk factor for the development of atherosclerosis in parrots in retrospective studies. Gender Female gender was shown to be a statistically significant risk factor in a recent multi-center case review. Estrogens are associated with increased plasma concentrations of cholesterol, triglycerides, lipoproteins, and calcium for the production of eggs. Reproductive diseases were found to be significantly linked to an increased rate of atherosclerosis in female parrots. Species African grey parrots (Psittacus erithacus), Amazon parrots (Amazona spp.), Quaker (monk) parakeets (Myiopsitta monachus), and cockatiels (Nymphicus hollandicus) appear especially susceptible to the disease. Cockatoos (Cacatua spp.) and macaws (Ara spp.) seem to be somewhat resistant to disease. Explanations for the variability in species susceptibility are speculative at best, but the disease may be associated with differences between captive and wild lifestyles, stress factors, dietary requirements, or genetics. Plasma lipids and lipoproteins African grey parrots and Amazon parrots tend to have higher plasma concentrations of cholesterol compared with other psittacine species. In one study, parrots with atherosclerotic lesions had a significantly higher median plasma cholesterol concentration than control birds. Experimentally induced atherosclerosis caused by adding cholesterol to the diet was associated with increases in plasma cholesterol concentrations in Quaker parakeets and budgerigars (Melopsittacus undulatus) and increased low-density lipoproteins (LDL) in Quaker parakeets. In Quaker parrots, plasma cholesterol concentrations were correlated with the severity of the atherosclerotic lesions. Coinfection with Chlamydia psittaci The association between infection with Chlamydia pneumoniae infection and atherosclerosis has been investigated in humans but remains a controversial topic. Research in birds has yielded conflicting results and evidence for a correlation is lacking. Research in birds using PCR for C. psittaci did not find a positive association between the two diseases but a case-control study using immunohistochemistry and specific anti-C. psittaci monoclonal antibodies did. However, anti-chlamydial antibodies are known to cross-react with ceroids and other atherosclerotic plaque lesions in humans, and this may have affected the results in this study.