Whole genome PCR scanning (WGPS) of Coxiella burnetii strains from ruminants

Prevalence, Risk Factors, and Relationship between Reproductive Performance and the Presence of Antibodies against Coxiellosis in Dairy Farm Milk Tanks in the Northwest of Spain

Q fever is a zoonotic disease that has been associated with reproductive problems in animals. As there is little epidemiological data regarding the distribution and risk factors of this disorder in cattle, the objective of this study was to evaluate the prevalence of Coxiella burnetii among dairy herds in the northwest of Spain, and to determine the on-farm risk factors associated with the disease and its effects on reproductive performance. Bulk tank milk (BTM) samples were collected from 262 commercial dairy herds from A Coruña, Lugo, and Pontevedra provinces. Data about location, mean age, and herd management features were obtained. A commercial indirect ELISA kit was used to determine the presence of antibodies against C. burnetii in BTM samples. The relationship between seropositivity to C. burnetii and the risk factors was checked using a Pearson's χ2 test and a classification tree analysis. In addition, a one-way ANOVA test and the Mann-Whitney U test were used to check the impact of seropositivity to C. burnetii on reproductive performance. A total of 60.1% of the farms tested positive for coxiellosis, the herd size, the external purchase of livestock, and the geographical area were identified as the main risk factors. Conception rate and first-service conception rate were significantly lower (p < 0.05) in positive farms (37.1 and 32.9%) compared to negative farms (39.8 and 36.1%). Similarly, positive farms had significant higher incidence of endometritis (13.7% vs. 11.2%, p < 0.05). Consequently, a high seropositivity and slightly negative effects of coxiellosis on reproductive performance were observed, which intensifies the need for further research, including the identification an active infection in positive herds and the characterization of the genotype.

Role of Goats in the Epidemiology of Coxiella burnetii

Since its first description in the late 1930s, Q fever has raised many questions. Coxiella burnetii, the causative agent, is a zoonotic pathogen affecting a wide range of hosts. This airborne organism leads to an obligate, intracellular lifecycle, during which it multiplies in the mononuclear cells of the immune system and in the trophoblasts of the placenta in pregnant females. Although some issues about C. burnetii and its pathogenesis in animals remain unclear, over the years, some experimental studies on Q fever have been conducted in goats given their excretion pattern. Goats play an important role in the epidemiology and economics of C. burnetii infections, also being the focus of several epidemiological studies. Additionally, variants of the agent implicated in human long-term disease have been found circulating in goats. The purpose of this review is to summarize the latest research on C. burnetii infection and the role played by goats in the transmission of the infection to humans.

Q Fever—A Neglected Zoonosis

Q fever remains a neglected zoonosis in many developing countries including Pakistan. The causing agent Coxiella (C.) burnetii is resistant to environmental factors (such as drying, heat and many disinfectants), resulting in a long-lasting infection risk for both human and animals. As the infection is usually asymptomatic, it mostly remains undiagnosed in animals until and unless adverse pregnancy outcomes occur in a herd. In humans, the infection leads to severe endocarditis and vascular infection in chronic cases. Limited data are available on molecular epidemiology and evolution of this pathogen, especially in ruminants. Genomic studies will help speculating outbreak relationships in this scenario. Likewise, pathogenesis of C. burnetii needs to be explored by molecular studies. Awareness programs and ensuring pasteurization of the dairy milk before human consumption would help preventing Q fever zoonosis.

Current approaches for the detection of Coxiella burnetii infection in humans and animals

Q fever (coxiellosis), caused by Coxiella burnetii, is an emerging or re-emerging zoonotic disease of public health significance and with worldwide distribution. As a causal agent of the one among the 13 global priority zoonoses, having the infectious dose as low as one bacterium, C. burnetii has been regarded as an obligate intracellular bacterial pathogen. The agent has been classified as a Group B bioterrorism agent by the Centre for Disease Control and Prevention (CDC), and the disease is included in the World Organisation for Animal Health (OIE) list of notifiable diseases. It is mainly transmitted through airborne route in humans and animals. Isolation of C. burnetii, using standard routine laboratory culture techniques was impossible until formulation of axenic-based medium. However, it is still to be included among routinely isolated laboratory pathogen, accounting prolonged incubation period (~7 days) and requirement of specific oxygen concentration (2.5% O₂). Therefore, indirect diagnostic tools have been mainly used for its diagnosis. So far serology has been mostly used for testing for C. burnetii infection. The detection of C. burnetii DNA by PCR in various clinical samples have also been widely used. The disease has remained largely under-reported, underdiagnosed and as a masked zoonosis; and therefore, needs to be explored through well-planned scientific studies for knowing its true status and likely it impact in humans and animals by employing state-of-the-art diagnostics, identifying its diverse and new host range, as well as risk factors involved in different geo-climatic, behavioural and social settings as well as risk groups. Here, we reviewed the current approaches used for the detection of C. burnetii infection in humans and animals at the population and individual level.

Validation study for using lab-on-chip technology for Coxiella burnetii multi-locus-VNTR-analysis (MLVA) typing: application for studying genotypic diversity of strains from domestic ruminants in France

Coxiella burnetii, the etiologic bacterium of Q fever zoonosis, is still difficult to control. Ruminants are often carriers and involved in human epidemics. MLVA is a promising genotyping method for molecular epidemiology. Different techniques are used to resolve the MLVA band profiles such as electrophoresis on agarose gels, capillary electrophoresis or using the microfluidic Lab-on-Chip system. In this study, system based on microfluidics electrophoresis with Lab-on-Chip technology was assessed and applied on DNA field samples to investigate the genotypic diversity of C. burnetii strains circulating in France. The Lab-on-Chip technology was first compared to agarose gel electrophoresis. Subsequently, the set-up Lab-on-Chip technology was applied on 97 samples collected from ruminants in France using the 17 markers previously described. A discordance rate of 27% was observed between Lab-on-Chip and agarose gel electrophoresis. These discrepancies were checked and resolved by sequencing. The cluster analysis revealed classification based on host species and/or geographic origin criteria. Moreover, the circulation of different genotypic strains within the same farm was also observed. In this study, MLVA with Lab-on-Chip technology was shown to be more accurate, reproducible, user friendly and safer than gel electrophoresis. It also provides an extended data set from French ruminant C. burnetii circulating strains useful for epidemiological investigations. Finally, it raises some questions regarding the standardization and harmonization of C. burnetii MLVA genotyping.