Molecular characterization by MLVA of Coxiella burnetii strains infecting dairy cows and goats of north-eastern Italy.

Q fever is a worldwide zoonotic disease caused by Coxiella burnetii (C. burnetii), an obligate intracellular bacterium. In ruminants, shedding into the environment mainly occurs during parturition or abortion, but the bacterium is shed also in milk, vaginal mucus, stools and urine. In Italy few surveys have been conducted and reported seroprevalence values ranged between 10% and 60%, even if few human cases have been described. Genotyping of bacteria is crucial for enhancing diagnostic methods and for epidemiological surveillance. The objective of this study was to investigate genotypic differences of C. burnetii genotypes directly in 34 samples, collected during a 3-years survey among 11 dairy cattle and 11 goat farms in the north-eastern part of Italy using a 6-locus multiple loci variable number of tandem repeat analysis (MLVA) method. The samples analysed included 13 bulk tank milk (BTM), 6 individual milk, 11 vaginal swabs and 4 foetal spleens. MLVA-type 2 was determined as the most prevalent in cattle in this study. C. burnetii strains circulating in the studied cattle population are very similar to genotypes previously described, while genotypes from goats showed an important variability. Further investigation are needed to understand the reason of this pattern.

IFAT and ELISA phase I/phase II as tools for the identification of Q fever chronic milk shedders in cattle.

Q fever is a widespread zoonotic disease caused by Coxiella burnetii. In cattle the bacterial shedding can persist without symptoms for several months and the shedders identification is a critical issue in the control of the infection at herd level. Following the example of the human protocols for the assessment of Q fever infection status, the aim of this study was the evaluation of the antibody response dynamics to phase I and phase II antigens in C. burnetii shedder dairy cows by means of a phase-specific serology, to verify the suitability of the investigated tools in recognising milk shedders. A total of 99 cows were monitored during time and classified on the basis of serological and PCR results in five groups identifying different shedding patterns. The 297 sera collected in three sampling times were tested by means of ELISA IgG for differential phase I and phase II antibodies detection, while a selection of 107 sera were tested by means of phase specific IgM and IgG IFAT. Both ELISA IgG and IFAT IgG highlighted a low reactivity in non-shedder seropositive animals compared to chronic milk shedder animals. ELISA IgG seemed to perform better than IFAT IgG-IgM, showing significant serological differences among groups that allowed recognising specific serological group patterns, in particular for chronic and occasional milk shedders. These results supported the hypothesis that an animal classification based on phase patterns is reasonable, although it needs to be further investigated.