Circulating genotypes of Leptospira in French Polynesia : An 9-year molecular epidemiology surveillance follow-up study

International audienceBackgroundLeptospirosis is a widespread zoonosis with global impact, particularly among vulnerable populations in resource-poor settings in tropical countries. Rodents have been considered to be the main reservoir of the disease; however, a wide variety of mammals can act as hosts as well. Here we examine the genetic diversity of Leptospira strains from biological samples of patients and animals in French Polynesia (FP) from 2011 to 2019.Methodology/Principal findingsFrom 2011 to 2019, we have collected 444 blood samples from patients diagnosed as having leptospirosis. The limited volume of clinical material and low amount of leptospiral DNA in blood samples led us to develop a nested PCR targeting the secY locus that enabled us to amplify and sequence 244 samples (55%). In addition, 20 Leptospira strains recovered from the blood of patients from 2002 to 2011 were sequenced and fully characterized at the serogroup level and used as reference strains for the association of different phylogenetic branches with respective serogroups. The secY sequences were compared with publicly available sequences from patients and animal reservoirs in FP (n = 79). We identified rats as the main source of infection for L. borgpetersenii serogroup Ballum and L. interrogans serogroup Icterohaemorrhagiae, dogs as the main source of infection for L. interrogans serogroup Australis, and farm pigs as the main source of infection for L. interrogans serogroups Pomona or Canicola. L. interrogans was associated with the most severe infections with 10 and 5 fatal cases due to serogroups Icterohaemorrhagiae and Australis, respectively. Mortality was significantly associated with older age (p-value < 0.001).Conclusions/SignificanceWe described the population dynamics of leptospires circulating among patients in FP, including two patients who were reinfected with unrelated Leptospira genotypes, and clarified the local role of the animal reservoirs in the transmission route of leptospirosis to humans. Routine Leptospira genotyping directly on biological samples should allow the epidemiological follow-up of circulating strains and assess the impact of control interventions on disease transmission

Hepatitis E prevalence in French Polynesian blood donors.

The HEV seroprevalence in mainland France is elevated (22.4%). In contrast, anti-HEV seroprevalence appears to be lower in Oceania. However, none is available for French Polynesia. We assessed the anti-HEV IgG and IgM prevalence on samples from 300 consecutive blood donors living on Tahiti and Moorea islands. Epidemiological information was collected using a specific questionnaire. Overall IgM seroprevalence was 0.6% and overall IgG seroprevalence was 7.7%. The presence of anti-HEV IgG was associated with increasing age (p = 0.01), eating chicken offal (p = 0.01) and cooked rabbit (p = 0.02). Conversely, eating fafaru-traditional Polynesian condiment-was associated with a lower rate of anti-HEV IgG (p<0.01).). All donors who surfed or practiced va'a (traditional outrigger canoë) were HEV seronegative. The Polynesian lifestyle and the particular food consumption patterns-especially the very well cooked pork-may be the key to understand the low HEV seroprevalence in French Polynesia

Screening test for neutralizing antibodies against yellow fever virus, based on a flavivirus pseudotype

International audienceGiven the possibility of yellow fever virus reintroduction in epidemiologically receptive geographic areas, the risk of vaccine supply disruption is a serious issue. New strategies to reduce the doses of injected vaccines should be evaluated very carefully in terms of immunogenicity. The plaque reduction test for the determination of neutralizing antibodies (PRNT) is particularly time-consuming and requires the use of a confinement laboratory. We have developed a new test based on the use of a non-infectious pseudovirus (WN/YF17D). The presence of a reporter gene allows sensitive determination of neutralizing antibodies by flow cytometry. This WN/YF17D test was as sensitive as PRNT for the follow-up of yellow fever vaccinees. Both tests lacked specificity with sera from patients hospitalized for acute Dengue virus infection. Conversely, both assays were strictly negative in adults never exposed to flavivirus infection or vaccination, and in patients sampled some time after acute Dengue infection. This WN/YF17D test will be particularly useful for large epidemiological studies and for screening for neutralizing antibodies against yellow fever virus

NOVAA-test and PRNT in 33 sera collected during acute clinical Dengue from hospitalized Polynesian children and adults (2015–2016).

<p>NOVAA-test and PRNT in 33 sera collected during acute clinical Dengue from hospitalized Polynesian children and adults (2015–2016).</p

NOVAA-test results: Percentage of neutralization with 20 sera from patients with PRNT titres ranging from 10 to 80.

<p>Four complementary sera with a previous PRNT results of 40 were diluted 1:4 in order to surround the cut-off for neutralizing antibody detection by PRNT.</p

Inter and intra-assay variability of infection with WNVV/YFV17D VLP 2011, VLP 2013, VLP 2014, VLP 2015 in Vero cell lines in 5 different sera collected before 17D- vaccine.

<p>Inter and intra-assay variability of infection with WNVV/YFV17D VLP 2011, VLP 2013, VLP 2014, VLP 2015 in Vero cell lines in 5 different sera collected before 17D- vaccine.</p

Neutralizing activity in the NOVAA-test and PRNT titers at 1:100. 1:500 and 1:1000 dilutions.

<p>Neutralizing activity in the NOVAA-test and PRNT titers at 1:100. 1:500 and 1:1000 dilutions.</p