Genetic diversity of Coxiella burnetii in domestic ruminants in central Italy

Background

As the epidemiology of human Q Fever generally reflects the spread of Coxiella burnetii in ruminant livestock, molecular characterization of strains is essential to prevent human outbreaks. In this study we report the genetic diversity of C. burnetii in central Italy accomplished by MST and MLVA-6 on biological samples from 20 goat, sheep and cow farms.

Results

Five MST and ten MLVA profiles emerged from the analysis establishing a part of C. burnetii strain world atlas. In particular, ST32 occurred on 12 farms (60%), prevalently in goat specimens, while ST12 (25%) was detected on 4 sheep and 1 goat samples. ST8 and a variant of this genotype were described on 2 different sheep farms, whereas ST55 was observed on a goat farm. Five complete MLVA profiles different from any other published genotypes were described in this study in addition to 15 MLVA incomplete panels. Despite this, polymorphic markers Ms23, Ms24 and Ms33 enabled the identification of samples sharing the same MST profile.

Conclusions

Integration of such data in international databases can be of further help in the attempt of building a global phylogeny and epidemiology of Q fever in animals, with a “One Health” perspective.

The length of BTV-8 viraemia in cattle according to infection doses and diagnostic techniques

Four groups of BTV free Frisian and cross bred calves were used to determine the length of viraemia following infection with different doses of BTV-8 Italian isolate. The first group of five animals was infected with 10 TCID(50) of BTV-8, the second group of four animals with 10(3) TCID(50) and the third group, which also included four animals, was infected with 10(6) TCID(50). A placebo containing uninfected tissue culture medium was given to the four animals of the fourth group. The viraemia was evaluated by real time RT-PCR and virus isolation. In all infected groups, virus isolation was able to detect infectious virus up to 39 days post infection (dpi) while RT-PCR was positive up to 151-157dpi. Infectious dose did influence neither the length nor the pattern of BTV-8 viraemia and confirmed that real time RT-PCR remains positive although no circulating virus is detectable in the peripheral circulation.

Risk factors associated with the occurrence of undesired effects in sheep and goats after field vaccination with modified-live vaccine against bluetongue virus serotypes 2, 4 and 16

In the 2004, the Sardinian bluetongue (BT) vaccination campaign used the combination of monovalent BTV-2, BTV-4 and BTV-16 modified-live vaccines manufactured by the Onderstepoort Biological Products in South Africa. Following vaccination, some herds showed temperature, oedema, lameness, hyperaemia and decrease in milk production, and some others remained perfectly healthy. This study aimed to evaluate whether important factors present in the herd at the time of vaccination could be associated to the occurrence of undesired effects observed after immunisation with BTV modified-live vaccines. A sample of 17 sheep and 4 goat flocks, for a total of 670 animals, were included in the study and risk factors such as presence of most important parasitic, bacterial and viral diseases as well as anomalies of biochemical and haematological parameters were associated to the presence or absence of side effects. For each factor the relative risk and 95% confidence interval were calculated. Following vaccination, bluetongue-like symptoms were observed in 13 flocks. In these flocks, a higher (P<0.05) proportion of animals had viraemia and showed higher titers to BTV-16 after immunisation. Positive association (RR=2.50, 1.17-5.04) was also found between flocks in which undesired effect were observed and positive serology against Maedi-Visna virus. On the contrary, presence of BTV genome fractions in the blood of animals at the time of vaccination was found to be protective (RR=0.7, 0.58-0.84) to the occurrence of undesired effect subsequent to BTV vaccination.

Serological evidence of USUTU virus occurrence in north-eastern Italy

In the recent years, USUTU virus (USUV), a flavivirus of the Japanese encephalitis virus complex, has been reported in Central Europe. As part of a systematic surveillance programme to monitor possible entrance and/or circulation of vector-borne viruses, since 2001, sentinel-chicken flocks were placed throughout the Italian territory nearby areas considered at risk of virus introduction. They have been periodically checked for the presence of antibodies against flaviviruses by indirect ELISA, plaque reduction neutralization test for USUTU, West Nile and tick-borne encephalitis viruses. In July 2007, a sentinel chicken in a flock of 20 animals located within the Ravenna province seroconverted to USUV reaching neutralizing titres up to 1:5120. A second chicken seroconverted to the same virus 2 months later. Although no virus was rescued from these animals and from wild or farm birds sampled in the area, these results still provided evidence of the circulation of USUV in north-eastern Italy.