Bovine campylobacteriosis in heifer: pathogenesis study and insights in the conventional and molecular diagnosis in an experimental bovine model and field cases.

Campylobacter fetus spp. is a bacterium associated to reproductive losses in cattle worldwide. It is a venereal infectious disease known as bovine campilobacteriosis, with high impact mainly in countries with extensive production systems. Here, we show pathogenesis and diagnostic methods for Campylobacter fetus detection in cervico-vaginal mucus (CVM) samples from heifers experimentally infected and field cases from herds with low reproductive performance by campylobacteriosis infection. Bacterial culture, direct immunofluorescence test and qPCR were used as diagnostic methods to evaluate detection of C. fetus. In the experimental model 30 Aberdeen Angus and crossbred heifers and 4 Aberdeen Angus bulls for natural mating were assigned to 3 groups experimentally challenged with C. fetus subsp. fetus (Cff), C. fetus subsps venerealis (Cfv) and C. fetus subsp venerealis biovar intermedius (Cfvi), respectively, and a negative control group, all followed for 9 months. Also, field samples of CVM and aborted fetuses were recollected from seven beef cattle farms. Bacteriological culture had the higher C. fetus detection rate in CVM being the most appropriate, followed by qPCR (with commercial extraction DNA kit), direct immunofluorescence test and qPCR (with in-house extraction DNA method), in both, experimental model and field cases. From experimental model after natural mating, 62.5% and 25% heifers got pregnant from Cff and Cfvi groups, respectively, while from Cfv no pregnancy was detected. The strain more frequently detected was Cfvi, followed by Cff and Cfv. Colonization of Cff in female genital tract with high number of carriers and presence in aborted fetuses was evidenced, suggesting a high risk to bovine reproductive health. Bacteriemia was not detected after genital infection. Given the low detection rate of either test, we suggest the use of both, PCR based methods and bacterial culture could result in higher detection rate in farms with endemic campylobacteriosis.

L-cysteine transporter-PCR to detect hydrogen sulfide-producing Campylobacter fetus.

Phenotypic differences between Campylobacter fetus fetus and C. fetus venerealis subspecies allow the differential diagnosis of bovine genital campylobacteriosis. The hydrogen sulfide production, for example, is a trait exclusive to C. fetus fetus and C. fetus venerealis biovar intermedius. This gas that can be biochemically tested can be produced from L-cysteine (L-Cys). Herein, we report a novel multiplex-PCR to differentiate C. fetus based on the evaluation of a deletion of an ATP-binding cassette-type L-Cys transporter that could be involved in hydrogen sulfide production, as previously described. A wet lab approach combined with an in silico whole genome data analysis showed complete agreement between this L-Cys transporter-PCR and the hydrogen sulfide production biochemical test. This multiplex-PCR may complement the tests currently employed for the differential diagnosis of C. fetus.