Vectorial status of the Asian tiger mosquito Aedes albopictus of La Réunion Island for Zika virus.

La Réunion Island has been the scene of unusually large epidemics of dengue and chikungunya viruses with Aedes albopictus as the sole vector. After experimental oral infection, Ae. albopictus from La Réunion Island can disseminate both dengue and chikungunya viruses but not the Asian genotype of Zika virus, suggesting a strong midgut barrier to dissemination. Autochthonous transmission of the Asian genotype of Zika virus is improbable on La Réunion Island.

Are Aedes albopictus or other mosquito species from northern Italy competent to sustain new arboviral outbreaks?

The Asian tiger mosquito Aedes albopictus (Skuse) (Diptera: Culicidae), native to Southeast Asia, has extended its geographical distribution to invade new temperate and tropical regions. This species was introduced in 1990 to Italy and has since become the main pest in urban settings. It was incriminated as a principal vector in the first European outbreak of chikungunya virus (CHIKV) in the province of Ravenna (Italy) in 2007. This outbreak was associated with CHIKV E1-226V, efficiently transmitted by Ae. albopictus. The occurrence of this outbreak in a temperate country led us to estimate the potential of Ae. albopictus to transmit CHIKV and dengue virus (DENV), and to determine the susceptibility to CHIKV of other mosquito species collected in northern Italy. Experimental infections showed that Ae. albopictus exhibited high disseminated infection rates for CHIKV (75.0% in Alessandria; 90.3% in San Lazzaro) and low disseminated infection rates for DENV-2 (14.3% in San Lazzaro; 38.5% in Alessandria). Moreover, Ae. albopictus was able to attain a high level of viral replication, with CHIKV detectable in the salivary glands at day 2 after infection. In addition, the other three mosquito species, Anopheles maculipennis Meigen, Aedes vexans vexans (Meigen) and Culex pipiens L., showed variable susceptibilities to infection with CHIKV, of 0%, 7.7% and 0-33%, respectively. This information on vector competence is crucial in assessing the risk for an outbreak of CHIKV or DENV in Italy.

Aedes aegypti in Brazil: genetically differentiated populations with high susceptibility to dengue and yellow fever viruses.

Aedes aegypti was eliminated from Brazil in 1955, but re-infested the country in the 1970s. Dengue outbreaks have occurred since 1981 and became endemic in several cities in Brazil after 1986. Urban yellow fever has not occurred since 1942, and only jungle yellow fever cases have been reported. A population genetic analysis using isoenzyme variation combined with an evaluation of susceptibility to both yellow fever and dengue 2 viruses was conducted among 23 A. aegypti samples from 13 Brazilian states. We demonstrated that experimental infection rates of A. aegypti for both dengue and yellow fever viruses (YFV) are high and heterogeneous, and samples collected in the endemic and transition areas of sylvatic yellow fever were highly susceptible to yellow fever virus. Boa Vista, a border city between Brazil and Venezuela, and Rio de Janeiro in the Southeast region are considered as the most important entry points for dengue dissemination. Considering the high densities of A. aegypti, and its high susceptibility to dengue and yellow fever viruses, the risk of dengue epidemics and yellow fever urbanization in Brazil is more real than ever.

Isoenzyme differentiation of Aedes aegypti populations in French Guiana.

Population genetics of peri-domestic Aedes aegypti (Diptera: Culicidae), vector of dengue and yellow fever, were investigated by gel electrophoresis of 10 enzyme loci in 14 samples of mosquito larvae collected in 1997-1998 from localities separated by distances of 3-275 km in French Guiana. Genetic differentiation between geographical populations was generally high (mean FST = +0.111, P < 10(-5)) even among seven sites <30 km apart (FST = +0.137, P < 0.05), but not positively correlated with distance. Thus, Ae. aegypti comprises a mosaic of genetically differentiated populations in French Guiana. This may be attributed to reinvasion from diverse origins through repeated founder events after this vector species was eliminated during the 1940s to 1960s.

Population genetic structure and competence as a vector for dengue type 2 virus of Aedes aegypti and Aedes albopictus from Madagascar.

Starch gel electrophoresis was used to assess the polymorphism of 7 isoenzymes in single mosquitoes (field-collected F0 or F1 generation) for Aedes albopictus (8 strains) from northern Madagascar. Mosquitoes of the F2 generation (3 strains of Aedes aegypti and 10 strains of Ae. albopictus) were tested for oral susceptibility to dengue type 2 virus. Aedes aegypti was less susceptible to viral infection than Ae. albopictus. The genetic differentiation was less high between Ae. albopictus populations collected in agglomerations connected by highly frequented roads, indicating that human ground transportation favors mosquito dispersal. These results have implications for the ecology, pattern of migration, and relative importance in epidemic transmission of dengue viruses between the 2 Aedes species.

Aedes aegypti in French Guiana: susceptibility to a dengue virus.

Twenty-seven samples of Aedes aegypti (F1 generation) from French Guiana were tested for their susceptibility to dengue serotype 2 virus. Very high infection rates were observed by indirect fluorescent antibody (IFA) test. Ae. aegypti samples were pooled according to two groups: the first group (N=10) represented mosquitoes from the urbanized area of Cayenne and surroundings, and the second group (N=17) corresponded to mosquitoes collected in the countryside. Infection rates were found to be similar in these two cases. These findings are discussed in relation with the history of Ae. aegypti in this part of the world.

An orbivirus of mosquitoes which induces CO2 sensitivity in mosquitoes and is lethal for rabbits.

An orbivirus, JKT-7400, isolated from Culex mosquitoes in Indonesia, replicated to a high titer and induced cytopathic effects in Aedes albopictus cell cultures. The virus produced lethal sensitivity to carbon dioxide in Culex and Aedes mosquitoes as well as in Drosophila melanogaster fruit flies but was not the agent of the hereditary sensitivity to carbon dioxide previously described for Culex quinquefasciatus. When injected intravenously in high doses, JKT-7400 virus was lethal for rabbits, apparently without replicating to a significant extent. It was not pathogenic for adult mice inoculated intravenously or for adult or suckling mice inoculated intracerebrally and intraperitoneally. Unlike an orbivirus isolated from Culex mosquitoes in China, JKT-7400 did not interfere with the replication of Japanese encephalitis virus in mosquitoes.

Preparation of high-titred antisera for sigma virus strains from Hawaii and France and their use in neutralization tests in vitro and in vivo.

Antisera were prepared in rabbits against two strains of sigma virus, from France and Hawaii respectively, using purified virus from cell cultures. All antisera had the same titre by immunofluorescence, 1/400 or 1/800, whether tested against the homologous or the heterologous virus. An antiserum prepared with the French strain neutralized the Hawaiian virus at a dilution of 1/800 both in vitro and in vivo. The Hawaiian virus was not neutralized to a significant extent by reference mouse ascitic fluids for 26 different vertebrate rhabdoviruses.

[Sertoli cells of the impubescent pig: a method for obtaining isolated cells]. / Cellules de Sertoli du porc impubère: technique d'obtention de cellules isolées.

Minced whole testes from immature pigs were treated with collagenase (0.4 mg/ml) then with trypsin (2.5 mg/ml). The resulting suspension of cells was divided into sterile bottles containing medium 199 supplemented with 5 p. 100 calf serum. Bottles were maintained at 32 degrees C. After about 24 hours medium was changed 3 times to eliminate free cells. Within 3 days preparations consisting of 81.5% Sertoli cells, 0.5% Leydig cells and 18% peritubular cells were obtained.