Diagnostic Accuracy of Blood Cytology and Conventional PCR Using Universal Primers for Detecting Haemoplasma Infection in Cats and Pigs of Thailand

Abstract

Background: Haemoplasma (haemotropic Mycoplasma sp.) is an aetiological agent of infectious anaemia in several mammals, including cats and pigs. Blood cytology lacks sensitivity for detecting this infection, and information regarding its accuracy in Thailand is lacking. Thus, PCR has emerged as the test of choice. Recently, a new conventional PCR (cPCR) assay targeting the 16S rRNA gene (approximately 1000 bp) was established and used in various studies, but its diagnostic accuracy has not been verified. Objectives: This study compared the accuracy of blood cytology and 16S rRNA-based cPCR with the previously described cPCR assay targeting a partial fragment of the 16S rRNA gene (approximately 600 bp). Methods: In total, 216 cat and 569 pig samples were tested for haemoplasma infection using blood cytology, 1000-bp cPCR, and 600-bp cPCR. The diagnostic properties and predictive utility of blood cytology and 1000-bp cPCR were assessed using 600-bp cPCR as the reference. Results: In cats, blood cytology exhibited 23.68% sensitivity, 74.72% specificity and a poor level of agreement with 600-bp cPCR, whereas 1000-bp cPCR displayed 100.00% sensitivity and specificity and an almost perfect level of agreement with 600-bp cPCR. In pigs, blood cytology displayed 34.23% sensitivity, 92.22% specificity and a fair level of agreement with 600-bp cPCR, whereas the 1000-bp cPCR assay displayed 94.14% sensitivity, 100% specificity and an almost perfect level of agreement with 600-bp PCR. Conclusions: Blood cytology exhibited little utility in diagnosing haemoplasma infection in cats and pigs, indicating that molecular assays, such as 1000-bp cPCR with almost perfect agreement and high diagnostic performances, should be used for diagnosing haemoplasma infection. Two cPCR assays used in this study have their own advantages. Therefore, the selection of a preferred assay depends on each researcher.