Extreme genetic diversity among Pirital virus (Arenaviridae) isolates from western Venezuela.

Pirital-like virus isolates from rodents collected in a variety of habitats within a six-state area of central Venezuela were analyzed genetically by amplifying a portion of the nucleocapsid protein gene using RT-PCR. Comparisons of the sequences from 30 selected Pirital-like virus isolates demonstrated up to 26% divergence in nucleotide sequences and up to 16% divergence in deduced amino acid sequences. Within the Pirital monophyletic group, 14 distinct lineages or genotypes, differing by at least 6% in nucleotide sequences, were identified. Although sample sizes were small for some lineages, many of the different genotypes were sampled in only one region or locality, suggesting allopatric divergence. Complement fixation tests with representatives of the most divergent Pirital virus lineages failed to delineate multiple species or subtypes within the Pirital clade. These results indicate that the previously proposed 12% nucleocapsid protein amino acid sequence divergence cutoff value for delineating arenavirus species is not appropriate for the entire family. When individual clones were examined from PCR amplicons, a mean of 0.17% sequence diversity vs the consensus sequences was detected, suggesting diverse quasispecies populations within infected rodent hosts. Possible explanations for the extreme genetic diversity within and among Pirital virus populations in infected rodents are discussed.

Guanarito virus (Arenaviridae) isolates from endemic and outlying localities in Venezuela: sequence comparisons among and within strains isolated from Venezuelan hemorrhagic fever patients and rodents.

Despite intensive surveillance, Venezuelan hemorrhagic fever (VHF), caused by Guanarito (GTO) virus, has been detected in only a small region of western Venezuela. To determine whether VHF is associated with a particular regional GTO virus strain(s), 29 isolates from rodents and humans throughout the surrounding regions were analyzed by partial sequencing of the nucleocapsid protein gene. Phylogenetic trees delineated nine distinct GTO genotypes that differ by 4-17% in nucleotides and up to 9% in amino acid sequences; most appeared to be restricted to discrete geographic regions, although a few genotypes were isolated in several locations. Each genotype included at least one strain recovered from a rodent, but only two genotypes were isolated from VHF cases. The presence outside of the endemic/epidemic region of two genotypes isolated also from VHF cases suggests that human pathogenic viruses occur outside of the endemic zone, but do not frequently infect people and/or cause apparent disease there. VHF does not appear to be associated with a GTO virus genotype that is restricted to a certain rodent species. When quasispecies diversity was examined, rodent isolates had higher sequence variation than human isolates. One rodent isolate included a mixture of two phylogenetically distinct genotypes, suggesting a dual infection.

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.

Incidencia de la infección por virus pirital en roedores de la especie sigmodón alstoni: efectos de la infección sobre la especie / Incidence of the pirital virus infection in rodents of the sigmodon alstony species: effects of the infection on the specie

El virus Pirital es un nuevo arenavirus descubierto en Venezuela, sin embargo no existen evidencias de que pueda ser un virus patógeno para el humano. Sus efectos en el roedor que le sirve de reservorio natural: sigmodón alstoni se analiza en el presente estudio. Un total de 478 roedores: S. alstoni fueron capturados entre junio de 1994 a diciembre de 1995 en el Municipio Papelón, estado Portuguesa. Se recolectaron muestras de sangre y bazo para el aislamineto e identificación de virus en cultivo de células Vero E6. La densidad de la población de roedores S. alstoni mostró un patrón estacional con un máximo éxito de trampeo al final de la estación de sequía (Marzo-Abril). Esta variación temporal no estuvo correlacionada con variaciones en la prevalencia de infección por virus Pirital. El promedio de infección en la especie fue de 33,8 por ciento con un incremento no significativo en la prevalencia de infección entre animales juveniles y adultos. El efecto de la infección por el virus Pirital en el peso y tamaño del cuerpo de los roedores así como en la fertilidad, número de animales por camada, etc. no fue significativamente diferente cuando se compararon los animales infectados con los no infectados

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.

Isolation, characterization and geographic distribution of Caño Delgadito virus, a newly discovered South American hantavirus (family Bunyaviridae).

Rodents collected from the Venezuelan llanos (plains) during field studies of viral hemorrhagic fever were tested for evidence of hantavirus infection. Hantavirus antibody was found in one (7.7%) of 13 Oryzomys bicolor, one (3.4%) of 29 Rattus rattus, 10 (6.0%) of 166 Sigmodon alstoni and one (2.2%) of 45 Zygodontomys brevicauda. Hantavirus-specific RNA was detected in lung tissues from four antibody-positive rodents: two S. alstoni from Portuguesa State and one S. alstoni each from Cojedes and Barinas States. A hantavirus isolate (herein identified as VHV-574) was recovered from lung tissue from a hantavirus RNA-positive S. alstoni collected from Portuguesa State. The results of serological tests and analyses of small and medium RNA segment nucleotide sequence data indicated that VHV-574 represents a novel hantavirus (proposed name 'Caño Delgadito') that is distinct from all previously characterized hantaviruses. The results of analyses of nucleotide sequence data from the four hantavirus RNA-positive S. alstoni suggested that Caño Delgadito virus is widely distributed in the Venezuelan llanos.