A pathological study in cynomolgus monkeys infected with Edesonfilaria malayensis

The host response to natural infection with Edesonfilaria malayensis in six female adult cynomolgus monkeys (Macaca fascicularis) imported from Indonesia was examined retrospectively by histopathology and clinical investigations. Reduced values of hemoglobin and hematocrit, an increased number of eosinophils, an elevated level of total protein and a decrease in A/G ratio were noted in hematological and blood chemical examinations of the infected animals. The filarial worms inhabited subserosal connective tissues of the abdominal and the thoracic cavities but not the lumina of the body cavities. There was thickening of the connective tissues, hemorrhage and adhesion of the serosa in the site occupied by the worms and the cysts. Histopathologically, proliferation of the connective tissues and/or granulation tissues, infiltration of eosinophils, lymphocytes and other cells associated with inflammation and hemorrhage were observed. The worms occasionally caused mechanical damage in nearby tissues such as the pancreas and the iliopsoas muscle. In addition, splenic nodules were found in five of the six infected monkeys as a secondary lesion specifically related to the infection with Edesonfilaria malayensis.