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Comparative Evaluation of Isolation, PCR Detection, and Clinico-pathological Diagnostic Approaches in Field Cases of Mycoplasma hyopneumoniae Infection in selected Farms of Luzon, Philippines
Thesis Abstract:
A study on Mycoplasma hyopneumoniae infection from 15 selected pig farms in Luzon was conducted. Forty-six lung tissues and 12 nasal swabs suspected to be mycoplasmal pneumonia of swine (MPS) were collected. These suspected MPS field cases were diagnosed and confirmed using clinico-pathological methods; namely, clinical signs, gross pathology, histopathology, bacterial isolation, and polymerase chain reaction (PCR). Sensitivity, specificity, accuracy, and positive and negative predictive values of each diagnostic method were also determined.
Clinical signs observed were coughing, labored breathing, pyrexia, unthrifty appearance, anorexia, and prolonged course. Gross lesions were confined to the lung and were clearly demarcated from the normal lung. Two types of gross lesions were observed: (1) acute, which is characterized by bilateral fawn, edematous, and pink; and (2) chronic, which is characterized by plum-colored, atelectatic areas of the anteroventral, apical, cardiac, and diaphragmatic lobes. The enlargement of bronchial and mediastinal lymph nodes was also seen in the infected pigs. In histopathology, peribronchiolar and perivascular lymphoid hyperplasia, as well as lymphoid module formation were found to be the most common characteristic lesions associated with M. hyopneumoniae infection.
M. hyopneumoniae isolation from 46 lung samples gave 4.34 percent (2/46) positive results while the 12 nasal swabs were all negative. In PCR identification, 17 pigs out of 34 (50%) showed positive reaction in the PCR using DNA extracted from the lung tissue, while the 12 nasal swab samples subjected to PCR identification had negative results.
Among the clinico-pathological methods used in this study for MPS diagnosis, histopathology had the highest specificity, accuracy, and positive predictive value, whereas clinical signs had the lowest. Isolation was still considered the diagnostic gold standard.
