The effect of different body positions on the cardiothoracic ratios obtained by chest radiography in Japanese macaques (Macaca fuscata) and rhesus macaques (Macaca mulatta).

BACKGROUND: Although some studies have reported cardiac diseases in macaques, an adequate screening method for cardiac enlargement has not yet been established. This study aimed to evaluate the positioning of macaques for radiographs and establish reference intervals for the cardiothoracic ratio (CTR). MATERIALS AND METHODS: We developed a device for chest radiography in the sitting position and performed chest radiography in 50 Japanese and 48 rhesus macaques to evaluate the CTR and chest cavity size. RESULTS: In Japanese and rhesus macaques, the thorax height was significantly larger, the heart width was significantly smaller, and the mean CTR was significantly smaller in the sitting position than in the prone position. The reference intervals for CTR in the sitting position were 51.6 ± 4.6% and 52.2 ± 5.1% in Japanese and rhesus macaques, respectively. CONCLUSION: Thoracic radiographic images obtained in a sitting position resulted in a smaller CTR and a larger thorax height, which could be useful for detecting pulmonary and cardiac abnormalities.

Prevalence and risk factors for feather-damaging behavior in psittacine birds: Analysis of a Japanese nationwide survey.

A case control study was conducted to estimate the prevalence of feather-damaging behavior and evaluate the correlation with risk factors among pet psittacine birds in Japan. Although feather-damaging behavior among pet parrots is frequently observed in Japan, its prevalence and potential risk factors have not been investigated. Therefore, we conducted an online questionnaire survey on parrot owners throughout Japan to examine regional differences in feather-damaging behavior and associated risk factors. In total, 2,331 valid responses were obtained. The prevalence of feather-damaging behavior was 11.7%, in general agreement with prior studies. The highest prevalence was among Cockatoos (Cacatua spp., etc.; 30.6%), followed by Lovebirds (Agapornis spp.; 24.5%) and African grey parrots (Psittacus erithacus; 23.7%). Multivariate logistic regression was carried out to calculate the adjusted odds ratio (ORadj) for potential risk factors and adjust the confounding of the variables. The odds of feather-damaging behavior were significantly higher for Conures (Aratinga spp., Pyrrhura spp., Thectocercus acuticaudatus, Cyanoliseus patagonus) (ORadj = 2.55, P = 0.005), Pacific parrotlets (Forpus coelestis) (ORadj = 3.96, P < 0.001), African grey parrots (ORadj = 6.74, P < 0.001), Lovebirds (ORadj = 6.79, P < 0.001) and Cockatoos (ORadj = 9.46, P < 0.001) than Budgerigars (Melopsittacus undulatus), and for young adults (ORadj = 1.81, P = 0.038) and adults (ORadj = 3.17, P < 0.001) than young birds, and for signs of separation anxiety (ORadj = 1.81, P < 0.001). Species, bird age and signs of separation anxiety were significantly higher risk factors for feather-damaging behavior than any other potential risk factors. Our findings, which include broad species diversity, are a good source of data for predicting risk factors for feather-damaging behavior and could be useful in preventing declines in welfare.

Usefulness of cardiac hormones for evaluating valvular disease in cynomolgus monkeys (Macaca fascicularis).

Nonhuman primates are commonly used as experimental animals due to their biological resemblance to humans. In patients with cardiac disease, the levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) tend to increase in response to cardiac damage, and they are thus used as indicators for the diagnosis of human heart failure. However, no reference values for ANP and BNP have been reported for heart disease in nonhuman primates. In this study, we recorded the age, sex, and body weight of 202 cynomolgus monkeys, and performed evaluations to assess the ANP and BNP levels, electrocardiography and echocardiography, and accordingly divided the monkeys into two groups: healthy monkeys and those with spontaneous cardiac disease. Statistical analysis was performed to determine the relationship of ANP and BNP with the factors of age, sex, and body weight. No significant relationship was found between the levels of ANP and BNP and the factors of age, sex, and body weight. However, both the ANP and BNP levels were significantly different between the healthy monkeys and monkeys with valvular disease. Similar to humans, the ANP and BNP levels tended to increase with the progression of cardiac disease in monkeys. Based on these results, we concluded that ANP and BNP are indicators of cardiac disease in nonhuman primates, and that this nonhuman primate cardiac disease model is applicable for cardiology research in humans.

Echocardiographic evaluation of cardiac function in cynomolgus monkeys over a wide age range.

Various cardiovascular diseases can be detected and diagnosed using echocardiography. The demand for cardiovascular system research using nonhuman primates is increasing, but echocardiographic references for nonhuman primates are limited. This report describes the first comparison of echocardiographic reference values in 247 normal cynomolgus monkeys (135 females, 112 males) over a wide age range. Echocardiography, electrocardiography, blood pressure and chest X-ray images were acquired under immobilization with intramuscular ketamine hydrochloride, then cardiac structure, function, and flow velocity were assessed. Cardiac hormone levels were also tested. We found that cardiac structures positively correlated with weight, that the size of these structures stabilized after reaching maturity and that cardiac output increased according to heart size. In contrast, fractional shortening of the left ventricle, ejection fraction and flow velocity showed no significant correlations with weight or age, and age and E wave correlated negatively. These findings appear sufficiently similar to those in humans to suggest that cynomolgus monkeys can serve as a suitable model of human cardiac disease. Our data should also prove useful for surveying cardiac dysfunction in monkeys.

Establishment of a new formula for QT interval correction using a large colony of cynomolgus monkeys.

The demand for monkeys for medical research is increasing, because their ionic mechanism of repolarization is similar to that of humans. The QT interval is the distance between the Q wave and T wave, but this interval is affected by heart rate. Therefore, QT correction methods are commonly used in clinical settings. However, an accurate correction formula for the QT interval in cynomolgus monkeys has not been reported. We assessed snapshot electrocardiograms (ECGs) of 353 ketamine-immobilized monkeys, including aged animals, and contrived a new formula for the corrected QT interval (QTc) as a marker of QT interval prolongation in cynomolgus monkeys. Values for QTc were calculated using the formula [QTc] = [QT] / [RR]n, along with several other formulas commonly used to calculate QTc. We found that the optimal exponent of the QT interval corrected for heart rate, n, was 0.576. The mean value of QTc in healthy monkeys determined using the new formula was 373 ± 31 mm, and there were no significant differences between the sexes. Other ECG parameters were not significantly different between the sexes and there were no age-related effects on QTc. Prolongation of QTc to over 405 ms, as calculated by the new formula, was observed in 50 monkeys with underlying diseases. Additionally, all monkeys with QTc above 440 ms by the new formula had some underlying disease. The results resemble those in humans, suggesting that the new QTc formula could be useful for diagnosis of QT interval prolongation in cynomolgus monkeys.