Tracking the Source of Human Q Fever from a Southern French Village: Sentinel Animals and Environmental Reservoir.

Coxiella burnetii, also known as the causal agent of Q fever, is a zoonotic pathogen infecting humans and several animal species. Here, we investigated the epidemiological context of C. burnetii from an area in the Hérault department in southern France, using the One Health paradigm. In total, 13 human cases of Q fever were diagnosed over the last three years in an area comprising four villages. Serological and molecular investigations conducted on the representative animal population, as well as wind data, indicated that some of the recent cases are likely to have originated from a sheepfold, which revealed bacterial contamination and a seroprevalence of 47.6%. However, the clear-cut origin of human cases cannot be ruled out in the absence of molecular data from the patients. Multi-spacer typing based on dual barcoding nanopore sequencing highlighted the occurrence of a new genotype of C. burnetii. In addition, the environmental contamination appeared to be widespread across a perimeter of 6 km due to local wind activity, according to the seroprevalence detected in dogs (12.6%) and horses (8.49%) in the surrounding populations. These findings were helpful in describing the extent of the exposed area and thus supporting the use of dogs and horses as valuable sentinel indicators for monitoring Q fever. The present data clearly highlighted that the epidemiological surveillance of Q fever should be reinforced and improved.

Comparison of two widely used PCR primer systems for detection of toxoplasma in amniotic fluid, blood, and tissues.

The PCR diagnosis of toxoplasmosis suffers from lack of standardization. Interlaboratory comparative studies of PCR methods have been performed, but intralaboratory comparisons are scarce. Here, we optimized and compared the technical performances of two PCR primer systems widely used for Toxoplasma detection. The differences between the two methods were visible only at low parasite concentrations (< or = 1 Toxoplasma genome per reaction tube). Nevertheless, when clinical samples were tested, both methods significantly differed in their technical sensitivities and specificities. Only one method appeared adequate for samples containing blood or tissue.

Comparison of six PCR methods using peripheral blood for detection of canine visceral leishmaniasis.

The objectives of this study were to compare the sensitivities and reliabilities of different PCR methods for the diagnosis and epidemiological study of canine visceral leishmaniasis (CVL) using dog blood. We chose to work with peripheral blood, as this type of sampling is noninvasive, straightforward, and easy to repeat. Six PCR methods were compared: three primer pairs target genomic DNA, and the other three target kinetoplast (mitochondrial) DNA. Sensitivity, specificity, reproducibility, and ease of interpretation without hybridization were evaluated for each method. The assessment was first performed using artificial samples. All methods could detect less than one parasite per reaction tube. However, the sensitivities varied among the different methods by a factor of 500 on purified cultivated parasites and by a factor of 10,000 on seeded dog blood samples (i.e., from 10 to 10(-3) parasite per ml of blood for the latter). Only four methods were found sufficiently reliable for the diagnosis of CVL. They were tested on 37 dogs living in an area of endemicity and grouped according to clinical status and specific serology. Only the two methods targeting kinetoplast DNA (K13A-K13B and RV1-RV2) could detect the parasite in 100% of symptomatic infected dogs. Similarly, all seropositive dogs were found PCR positive by these methods versus 62% by the genomic-DNA-based methods. Finally, these kinetoplast-based methods proved clearly superior to the others in the detection of Leishmania in asymptomatic dogs. Our data allow the discussion of the advantages and drawbacks of highly sensitive versus moderately sensitive PCR methods in diagnosis and prevalence studies of CVL.