Reduced Avian Virulence and Viremia of West Nile Virus Isolates from Mexico and Texas

Abstract

Abstract. A West Nile virus (WNV) isolate from Mexico (TM171-03) and BIRD1153, a unique genotype from Texas, have exhibited reduced murine neuroinvasive phenotypes. To determine if murine neuroinvasive capacity equates to avian virulence potential, American crow ( Corvus brachyrhynchos ) and house sparrows ( Passer domesticus ) were experimentally inoculated with representative murine neuroinvasive/non-neuroinvasive strains. In both avian species, a plaque variant from Mexico that was E-glycosylation competent produced higher viremias than an E-glycosylation-incompetent variant, indicating the potential importance of E-glycosylation for avian replication. The murine non-neuroinvasive BIRD1153 strain was significantly attenuated in American crows but not house sparrows when compared with the murine neuroinvasive Texas strain. Despite the loss of murine neuroinvasive properties of nonglycosylated variants from Mexico, our data indicate avian replication potential of these strains and that unique WNV virulence characteristics exist between murine and avian models. The implications of reduced avian replication of variants from Mexico for restricted WNV transmission in Latin America is discussed.

Dynamics of West Nile virus evolution in mosquito vectors

“…Taken together, a WNV strain that can cause higher viremia in birds (e.g. [51,52]) may be more likely to maintain its diversity during initial mosquito infection. Second, we recently described how the species of mosquito involved in transmission can also strongly influence virus divergence, which may be associated with host susceptibility (virus replication and purifying selection) and the strengths of anatomical barriers (vector competence and bottleneck severity) [26].…”

West Nile viral infection of equids

“…Interestingly, several cases of equine encephalitis were reported in a more temperate region of Argentina in 2006 (Morales et al, 2006), indicating the potential that climactic factors could restrict disease presentation in humans and equids via differences in the force of transmission or the potential modulating effects of host diversity (Ezenwa et al, 2006; Swaddle and Calos, 2008) in different biomes or the presence of immune responses against heterologous flaviviruses that could afford protection against disease presentation. Sequence analyses of the few isolates of WNV that have been made in Mexico (Beasley et al, 2004) not adjacent to the U.S.–Mexican border as well as the Argentinean isolates from encephalitic horses indicate that the effects of genetic drift and the introduction of lesser virulent genotypes (Morales et al, 2006; Brault et al, 2011; Langevin et al, 2011) could play a role in reduced virulence potential.…”

Detection of Persistent West Nile Virus RNA in Experimentally and Naturally Infected Avian Hosts

“…A subset of House Sparrows were infected with either the mouse neuroinvasive (BIRD 1461, TM171-03-pp5 and NY99) or non-neuroinvasive (TM171-03-pp1 and BIRD1153) isolates of WNV; detailed descriptions of these genotypes and associated avian infection response phenotypes were reported by Brault and others. 24 The remaining House Sparrows were infected with a NY99 WNV infectious clone 25 containing one of five point mutations. Because sample sizes of birds available for analysis were limited, these viruses were evaluated as a group.…”