Natural rodent host associations of Guanarito and pirital viruses (Family Arenaviridae) in central Venezuela.

The objective of this study was to elucidate the natural rodent host relationships of Guanarito and Pirital viruses (family Arenaviridae) in the plains of central Venezuela. Ninety-two arenavirus isolates from 607 animals, representing 10 different rodent species, were characterized to the level of serotype. The 92 isolates comprised 19 Guanarito virus strains and 73 Pirital virus strains. The 19 Guanarito virus isolates were from Zygodontomys brevicauda; 72 (98.6%) of the 73 Pirital virus isolates were from Sigmodon alstoni. These results indicate that the natural rodent associations of these 2 sympatric arenaviruses are highly specific and that Z brevicauda and S. alstoni are the principal rodent hosts of Guanarito and Pirital viruses, respectively.

[Serotypes and genotypes of dengue virus circulating in Venezuela, 1990-1997]. / Serotipos y genotipos de virus dengue circulantes en Venezuela, 1990-1997.

Due to the increasing severity of hemorrhagic dengue epidemics during the last years in Venezuela, a retrospective analysis was conducted to identify the behaviour of the dengue virus serotypes circulating in the country and the molecular evolution of dengue virus serotype 2. The data presented here indicates that dengue virus serotypes 1, 2 and 4 are endemic in Venezuela, they circulate simultaneously around the year in the biggest urban cities, however, one particular serotype is predominant during an epidemic period and replaces the virus serotype dominant during the previous epidemic period. The increased severity of dengue fever since 1989 in Venezuela might be associated to the introduction of the Asiatic genotype of virus which replaced the autochthonous Caribbean genotype. The Asiatic genotype is recognised as a more virulent virus.

Isolation and characterization of pirital virus, a newly discovered South American arenavirus.

Specific rodent species are principal hosts for each of the well-characterized members of the virus family Arenaviridae. Guanarito virus (Arenaviridae) is the etiologic agent of Venezuelan hemorrhagic fever. A previous study on the epidemiology of Venezuelan hemorrhagic fever revealed extensive arenavirus infection (presumed to be caused by Guanarito virus) in two rodent species. Sigmodon alstoni and Zygodontomys brevicauda, collected from the region of Venezuela in which the disease is endemic. In the present study, four arenavirus isolates recovered from the Municipality of Guanarito (two isolates each from S. alstoni and Z. brevicauda) were characterized to learn more about the natural rodent host relationships of Guanarito virus. Serologic tests and analyses of nucleocapsid protein gene sequence data indicated that the two isolates from Z. brevicauda are strains of Guanarito virus and that the two isolates from S. alstoni are representatives of a novel New World arenavirus (proposed name Pirital) that is antigenically and phylogenetically distinct from all known New World arenaviruses. The results of the present study provide further evidence that the cane mouse Z. brevicauda is a natural host of Guanarito virus and suggest that the cotton rat S. alstoni is the natural reservoir host of Pirital but not Guanarito virus.