Concept of an Active Surveillance System for Q Fever in German Small Ruminants-Conflicts Between Best Practices and Feasibility.

Q fever is a zoonotic disease caused by the bacterium Coxiella burnetii. Inhalation of contaminated dust particles or aerosols originating from animals (esp. small ruminants) is the main source of human infection. Hence, an active early warning system for Q fever in German small ruminant livestock was conceptualized to prevent human infections. First, we describe the best practice for establishing this system before evaluating its feasibility, as the combination of both evokes conflicts. Vaginal swabs from all husbandry systems with a focus on reproductive females should pooled and investigated by PCR to detect C. burnetii-shedding animals. Multistage risk-based sampling shall be carried out at the flock level and within-flock level. At the flock level, all flocks that are at risk to transmit the pathogen to the public must be sampled. At the within-flock level, all primi- and multiparous females after lambing must be tested in order to increase the probability of identifying a positive herd. Sampling should be performed during the main lambing period and before migration in residential areas. Furthermore, individual animals should be tested before migration or exhibition to ensure a negative status. If a flock tests positive in at least one individual sample, then flock-specific preventive measures should be implemented. This approach implies huge financial costs (sample testing, action/control measures). Hence, taking the step to develop more feasible and affordable preventive measures, e.g., vaccinating small ruminant flocks, should replace testing wherever justifiable.

Humoral immune response to Q fever vaccination of three sheep flocks naturally pre-infected with Coxiella burnetii.

Qfever is a zoonotic disease caused by the bacterium Coxiella burnetii; Coxiella-infected ruminants are the main reservoir shedding the pathogen during abortion or parturition through birth products. Germany has a long history of small-scale Q fever epidemics in the human population mostly associated with lambing sheep. Therefore, fast and efficient control measures are essentially required to prevent transmission from infected sheep flocks to humans. In our present study, three sheep flocks were vaccinated with an inactivated C.burnetii phase I vaccine after a field infection with C.burnetii was diagnosed. Serum samples and vaginal swabs were collected at different time points to evaluate the extent of the outbreak and the consequences of the vaccination. The serum samples were examined by phase-specific IgG phase I and phase II ELISAs and a commercial ELISA, simultaneously detecting both phase variations. Moreover, vaginal swabs were analysed by qPCR. The fourth flock with no Q fever history and non-vaccinated animals were used as a control group to evaluate the phase-specific ELISAs. The inactivated C.burnetii phase I vaccine induced an IgG phase II response and boosted the humoral immune reaction against natural pre-infections. Furthermore, the longevity of vaccine-induced antibodies seems to depend on previous infections. Around 16 months after primary vaccination, mainly IgG phase I antibodies were detectable. Vaccination did not prevent shedding at the next lambing season. Most interestingly, the phase-specific ELISAs revealed more C.burnetii positive animals than the blended ELISA-Assay. Taken together, phase-specific ELISAs are suitable tools to provide insights into natural- or vaccine-induced humoral immune responses to C.burnetii in sheep.

Molecular typing of Streptococcus suis strains isolated from diseased and healthy pigs between 1996-2016.

Streptococcus suis is an economically important pathogen of pigs as well as a zoonotic cause of human disease. Serotyping is used for further characterization of isolates; some serotypes seem to be more virulent and more widely spread than others. This study characterizes a collection of German field isolates of Streptococcus suis from pigs dating from 1996 to 2016 with respect to capsular genes (cps) specific for individual serotypes and pathotype by multiplex PCR and relates results to the clinical background of these isolates. The most prominent finding was the reduction in prevalence of serotype-2/serotype-1/2 among invasive isolates during this sampling period, which might be attributed to widely implemented autogenous vaccination programs in swine against serotype 2 in Germany. In diseased pigs (systemically ill; respiratory disease) isolates of serotype-1/serotype-14, serotype-2/serotype-1/2, serotype 3 to 5 and 7 to 9 were most frequent while in carrier isolates a greater variety of cps types was found. Serotype-1/serotype-14 seemed to be preferentially located in joints, serotype 4 and serotype 3 in the central nervous system, respectively. The virulence associated extracellular protein factor was almost exclusively associated with invasive serotype-1/serotype-14 and serotype-2/serotype-1/2 isolates. In contrast, lung isolates of serotype-2/serotype-1/2 mainly harbored the gene for muramidase-released protein. Serotype 4 and serotype 9 isolates from clinically diseased pigs most frequently carried the muramidase-released protein gene and the suilysin gene. When examined by transmission electron microscopy all but one of the isolates which were non-typable by molecular and serological methods showed various amounts of capsular material indicating potentially new serotypes among these isolates. Given the variety of cps types/serotypes detected in pigs, not only veterinarians but also medical doctors should consider other serotypes than just serotype 2 when investigating potential human cases of Streptococcus suis infection.