Application of Polymerase Chain Reaction to the Direct Diagnosis of Abortive Chlamydiosis (Chlamydophila abortus and Chlamydophila pecorum) of Sheep and Goats in Morocco

Abstract

In order to improve the direct diagnosis of abortive chlamydiosis in small ruminants, 225 vaginal swabs collected from aborting sheep and goats were tested for Chlamydophila DNA by two types of polymerase chain reactions (PCR): chlamydial-infection specific PCR (CTU/CTL), and speciesspecific PCR (CPS/CPC) for Chlamydophila abortus and Cp. pecorum. The omp1 gene coding for the major outer membrane protein of Chlamydiales was found in 65 (29%) of the analyzed samples, of which 80% had been collected within four weeks postabortion. The majority of PCR (CTU/CTL) positive samples (69%) came from herds found positive by the complement fixation test. The species-specific PCR applied to PCR (CTU/CTL) positive samples did not allow detecting the expected fragments of Cp. abortus (1800 bp) and Cp. pecorum (580 bp), except in four samples out of 65 tested. The remaining samples were either negative (63%) or non conclusive (31%) with non-specific bands of intermediate molecular weights. The enzyme restriction analysis of the omp1 gene after DNA amplification revealed much genetic diversity among the 65 samples tested. Typical genetic patterns of Cp. abortus were found only in 15 samples, but the majority (77%) of the samples showed patterns attributed to Cp. pecorum or closely related to it. Culture on McCoy cells of 26 vaginal swabs and abortion products from animals found with chlamydial infection (serology and PCR) revealed the presence of Chlamydophila in eight samples: seven were characterized as Cp. abortus and one as Cp. pecorum. The remaining samples gave no cytopathogenic effect after five serial passages, or they were contaminated. A Cp. pecorum strain, designated M14, isolated for the first time in Morocco, was further investigated to test its virulence in mice. These data suggest there is genetic variation in abortive strains and a possible link between Chlamydophila pecorum and abortions in sheep and goats in Morocco. This genetic diversity needs to be further investigated in order to gear vaccination strategies for control of abortive chlamydiosis in Morocco.