Tonate virus infection in French Guiana: clinical aspects and seroepidemiologic study.

Two recent cases of human infection with Tonate virus, one of which was a fatal case of encephalitis, have renewed interest in these viruses in French Guiana. The clinical aspects of confirmed and probable cases of infection with this virus indicate that it has pathogenic properties in humans similar to those of other viruses of the Venezuelan equine encephalitis complex. To determine the prevalence of antibodies to Tonate virus in the various ethnic groups and areas of French Guiana, 3,516 human sera were tested with a hemagglutination inhibition test. Of these, 11.9% were positive for the virus, but significant differences in seroprevalence were found by age, with an increase with age. After adjustment for age, significant differences were found between places of residence. The prevalence of antibody to Tonate virus was higher in savannah areas, especially in the Bas Maroni (odds ratio [OR] = 22.2, 95% confidence interval [CI] = 15.2-32.4) and Bas Oyapock areas (OR = 13.4; 95% CI = 9.8-18.4). The ethnic differences observed in this study were due mainly to differences in place of residence, except that whites were significantly less frequently infected than other ethnic groups. This study indicates that Tonate virus infection is highly prevalent in French Guiana, especially in savannah areas.

Association of severe malaria with a specific Plasmodium falciparum genotype in French Guiana.

Why severe Plasmodium falciparum malaria occurs in only a small percentage of patients is unclear. The possibility that specific parasite characteristics contribute to severity has been investigated in French Guiana, a hypoendemic area, where parasite diversity is low and all patients with severe cases are referred to a single intensive care unit. Parasite genotyping in geographically and temporally matched patients with mild and severe disease showed that the association of a specific msp-1 allele (B-K1) with a specific var gene (var-D) was overrepresented among patients with severe versus mild disease (47% vs. 3%, respectively; P<.001). Moreover, this genotype combination was consistently observed in the most severe clinical cases. Reverse-transcription polymerase chain reaction demonstrated programmed expression of var-D in vivo, which is consistent with its potential implication in severe disease. These results provide field evidence of an association of severe malaria with specific genetic characteristics of parasites and open the way for intervention strategies targeting key virulence factors of parasites.

Surveillance of dengue fever in French Guiana by monitoring the results of negative malaria diagnoses.

Surveillance of dengue fever is mainly based on specific laboratory tests. However non-specific systems, such as clinical surveillance, are also required. In French Guiana, we have tested a non-specific laboratory surveillance system where different biological examinations performed for other reasons than the diagnosis of dengue fever were analysed as methods for dengue fever surveillance. The number of negative malaria diagnoses in Cayenne and Kourou was found to be the best indicator of dengue fever infections in these towns. This surveillance system appears to be very simple and reliable, and a test which could serve as an indicator that is likely to be found everywhere.

First case of yellow fever in French Guiana since 1902.

The first case of yellow fever in French Guiana since 1902 was reported in March 1998. The yellow fever virus genome was detected in postmortem liver biopsies by seminested polymerase chain reaction. Sequence analysis showed that this strain was most closely related to strains from Brazil and Ecuador.

Plasmodium falciparum parasites in French Guiana: limited genetic diversity and high selfing rate.

The genetic characteristics of Plasmodium falciparum isolates collected in French Guiana, where malaria transmission is low and occurs in isolated foci, were studied. Blood samples were collected from 142 patients with symptomatic malaria and typed using a polymerase chain reaction-based strategy for merozoite surface protein-(MSP-1) block 2, the MSP-2 central domain, and glutamate-rich protein (GLURP) repeat domain polymorphism. This showed that the parasite population circulating in French Guiana presented a limited number of allelic forms (4, 2, and 3 for MSP-1 block 2, MSP-1, and GLURP, respectively) and a small number of mixed infections, contrasting with the large genetic diversity of parasite populations and infection complexity reported for Africa, Asia, and other parts of South America. Two groups of isolates displaying identical 3 loci allele combinations were further studied for the Pf332 antigen, histidine-rich protein-1, thrombospondin-related anonymous protein, and Pf60 multigene family polymorphism. Within each group, most isolates were identical for all markers tested. This suggests a high rate of self-fertilization of P. falciparum parasites in French Guiana, resulting in homogenization of the population. The implications of these findings for malaria control in areas of low endemicity are discussed.

Dengue encephalitis in French Guiana.

Thousands of cases of dengue fever (DF) and several cases of dengue haemorrhagic fever were recorded in French Guiana during the recent outbreak of dengue-2 virus (1991-1992) and in subsequent years. One case with clinical signs typical of classical DF with neurological complications is reported in this study. The neurological features (encephalitis) appeared during the acute phase, 2 days after the onset of fever. Dengue-2 virus was detected in both the cerebrospinal fluid and blood sample. This case was fatal. This first reported case of classical DF with encephalitis in French Guiana is a new demonstration of the potential neurovirulence of dengue viruses.

Mayaro virus fever in French Guiana: isolation, identification, and seroprevalence.

This paper reports the first isolation of Mayaro (MAY) virus from a patient infected in French Guiana. The identification was initially performed using immunofluorescent antibody testing with specific mouse antibody, and confirmed by plaque-reduction neutralization testing and reverse transcription-polymerase chain reaction. To determine if MAY virus infection is widespread in French Guiana, a serosurvey was performed to determine the prevalence of antibody to this virus in various ethnic groups and areas of French Guiana. Human sera (n = 1,962) were screened using the hemagglutination inhibition (HI) test. To determine whether MAY virus circulates in the rain forest, a serosurvey in monkey populations was performed. Monkey sera (n = 150) were also screened for antibody to MAY virus using HI testing. Of the human sera tested, 6.3% were positive for anti-MAY virus antibodies. Significant differences in MAY virus seroprevalence between different age groups were observed. Seroprevalence rates increased with age, with a large increase in people 10-19 years of age in comparison with those less than 10 years of age. After adjustment for age, significant differences were also found between places of residence. The prevalence of anti-MAY virus antibody was higher in people living in contact with the forest, especially in the Haut Oyapock area (odds ratio [OR] = 97.7, 95% confidence interval [CI] = 48.2-197.9) and along the Maroni River (OR = 39.7, 95% CI = 20.6-76.6). The ethnic differences observed in this study were probably due to differences in residence. Among monkeys, higher seroprevalence rates were found in Alouatta seniculus (66.0%) than in Saguinus midas (18.2%). Among Alouatta, the seroprevalence increased significantly with weight (and therefore with age). This study indicates that MAY virus is present in French Guiana, and human infections occur in areas where people live near the tropical rain forest.

Prevalence of antibodies to hepatitis A, C, and E viruses in different ethnic groups in French Guiana.

In order to determine the prevalence of antibodies to hepatitis A, C, and E viruses (HAV, HCV, and HEV) in the various ethnic groups and areas of French Guiana, sera (996 for HCV and HEV, 941 for HAV) were tested for antibodies to these viruses using ELISAs. Differences in HAV seroprevalence were found for different age groups, with a large increase in people aged 20-30 years in comparison with those under 20. After logistic analysis, significant differences were found between places of residence; the prevalence of anti-HAV was higher along the Maroni and Oyapock rivers than in the littoral area. The ethnic differences that were observed were generally due to differences in residence. Of all sera, 5.3% were positive for anti-HCV in preliminary tests, but only 1.5% remained positive after confirmation. Brazilians were significantly more frequently infected by HCV than other ethnic groups (4.7%). Sixty-four sera (6.4%) had antibodies to HEV, and differences were found between ethnic groups. Persons of ethnic groups who had emigrated recently to French Guiana had significantly higher seroprevalence rates: 14.6% for Chinese and Hmongs [odds ratio (OR), 4.4; 95% confidence interval (CI), 1.8-10.7], 13.5% for Brazilians (OR, 4.1; CI, 1.8-9.4), and 10.6% for Haitians (OR, 3.1; CI, 1.1-8.7).