Introduction: West Nile virus (WNV) immunoglobulin M (IgM) antibodies have been shown to persist for up to 500 days in certain patients. To evaluate the usefulness of immunoglobulin G (IgG) avidity assessment in the diagnosis of WNV infection, we analyzed 54 WNV IgM-and/or IgG-positive serum samples from 39 patients with neuroinvasive disease and 15 asymptomatic cases tested during a seroprevalence investigation. Methods: Serological tests (WNV IgM/IgG antibody detection, IgG avidity) were performed using commercially available enzyme-linked immunosorbent assays. Results: WNV IgM antibodies were detected in 47 (87%) samples. Acute/recent WNV infection was confirmed based on low/borderline avidity index (AI) in 44 IgM-positive samples (93.6%). In three IgM-positive samples (6.4%), high IgG AIs were detected, thus indicating persisting IgM antibodies from previous infections. All IgM-negative samples showed high AIs. Patients with WNV neuroinvasive disease tested within 30 days showed low AIs. In six patients tested 34-50 days after disease onset, AI was borderline (42%-60%), suggesting earlier WNV IgG maturation. Samples with the highest IgM values were associated with the lowest AIs (Spearman's rho coefficient-0.767, p < 0.001). Conclusions: Our results indicate that IgG avidity differentiates current/recent WNV infection from persistent IgM seropositivity from the previous WNV transmission season both in patients with WNV neuroinvasive disease and in asymptomatic persons. A strong negative correlation between IgM antibody levels and AI indicates that in cases with very high IgM levels, determination of IgG avidity may not be necessary. As many patients showed rapid avidity maturation, low IgG avidity is indicative of WNV infection within the previous month.
Purpose: Canine leishmaniosis is caused by Leishmania infantum, or also called in the New World L. chagasi. It is considered to be a major potentially fatal zoonotic infection where the domestic dog is the main reservoir. This infection is worldwide and reported with a higher incidence in tropical and subtropical areas such as South America where the number of infected dogs is estimated in the millions. No molecular data has been available on this disease in French Guiana. The aim of this study was molecular investigation of occurrence of leishmania in the blood of dogs in this region.Methods & Materials: Since 2016, blood samples were collected on a total of 98 dogs from French Guiana and 26 other dogs coming from continental France, were sampled before and after a 4-month mission in the same region. The samples were tested by a qPCR to quantify L. infantum kinetoplast DNA. Some positive samples were confirmed and species were identified, after sequencing, by using two standard PCR systems: i) a pan-Leishmania system was designed, targeting 28S rRNA gene and ii) PCR generic primers to amplify a segment of the rRNA internal transcribed spacer 2 (ITS2) from multiple Leishmania species.Results: The results show at least 4.08% (3/98) were positive to this pathogen and two (2/26) dogs returned positive although they were negative to begin with; one of them had an ulcer on the pastern. This last had 9 × 10 7 Leish/mL of blood, 1.3 × 10 10 Leish/mL from ulcer swab and around 4.3 × 10 6 Leish/g of bone marrow. In general, the parasite load was from 2.5 Leish/mL to 8 × 10 13 Leish/mL of dog's blood. Sequencing analyses identified L. infantum specie. Conclusion:The detection of L. infantum in local dogs in French Guiana and in dogs from metropolitan France after coming back from French Guiana, provide evidence that this region is endemic for canine leishmaniosis. It highlights the need for active surveillance in canine population and implementation of control measures. Competent vectors in this region are yet to be identified.
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