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Evidence for co-evolution of West Nile Virus and house sparrows in North America.

Duggal NK, Bosco-Lauth A, Bowen RA, Wheeler SS, Reisen WK, Felix TA, Mann BR, Romo H, Swetnam DM, Barrett AD, Brault AC - PLoS Negl Trop Dis (2014)

Bottom Line: West Nile virus (WNV) has been maintained in North America in enzootic cycles between mosquitoes and birds since it was first described in North America in 1999.Moreover, recently isolated WNV strains generate higher peak viremias and mortality in contemporary HOSPs compared to NY99.These data indicate that opposing selective pressures in both the virus and avian host have resulted in a net increase in the level of host competence of North American HOSPs for currently circulating WNV strains.

View Article: PubMed Central - PubMed

Affiliation: Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, United States of America.

ABSTRACT
West Nile virus (WNV) has been maintained in North America in enzootic cycles between mosquitoes and birds since it was first described in North America in 1999. House sparrows (HOSPs; Passer domesticus) are a highly competent host for WNV that have contributed to the rapid spread of WNV across the U.S.; however, their competence has been evaluated primarily using an early WNV strain (NY99) that is no longer circulating. Herein, we report that the competence of wild HOSPs for the NY99 strain has decreased significantly over time, suggesting that HOSPs may have developed resistance to this early WNV strain. Moreover, recently isolated WNV strains generate higher peak viremias and mortality in contemporary HOSPs compared to NY99. These data indicate that opposing selective pressures in both the virus and avian host have resulted in a net increase in the level of host competence of North American HOSPs for currently circulating WNV strains.

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Peak viremias and mortality in HOSPs by viral isolate and over time.Points represent individual birds. HOSPs inoculated with East Coast viruses are designated in blue; HOSPs inoculated with WN02 viruses are designated in green; and HOSPs inoculated with SW03 viruses are designated in purple. (A) Peak serum titers for individual HOSPs inoculated with one of the 12 WNV isolates. Bars represent the mean peak titer for each WNV genotype. Error bars reflect the standard deviation of the mean. (B) Linear regression analysis of peak serum titer for individual birds inoculated with WNV, stratified by year of virus collection. 95% confidence intervals are shown by the dotted lines. (C) Percent HOSP survival for 7 days post-inoculation. Viral isolates are represented by dashed lines, and genotype means are represented by solid lines. *p<0.05.
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pntd-0003262-g002: Peak viremias and mortality in HOSPs by viral isolate and over time.Points represent individual birds. HOSPs inoculated with East Coast viruses are designated in blue; HOSPs inoculated with WN02 viruses are designated in green; and HOSPs inoculated with SW03 viruses are designated in purple. (A) Peak serum titers for individual HOSPs inoculated with one of the 12 WNV isolates. Bars represent the mean peak titer for each WNV genotype. Error bars reflect the standard deviation of the mean. (B) Linear regression analysis of peak serum titer for individual birds inoculated with WNV, stratified by year of virus collection. 95% confidence intervals are shown by the dotted lines. (C) Percent HOSP survival for 7 days post-inoculation. Viral isolates are represented by dashed lines, and genotype means are represented by solid lines. *p<0.05.

Mentions: To determine whether the WN02 displacement of the East Coast genotype was the result of viral adaptation to North American avian hosts, groups of HOSPs collected in 2012 and 2013 were inoculated with 12 WNV isolates representing the three North American genotypes: East Coast, WN02, and SW03 (Table 1). In total, seventy-two birds were collected and inoculated with WNV in 2012–2013, and viremias were measured daily for 7 days. As expected for wild-caught birds, there was considerable variability in viral titers among replicates within groups (Fig. 2a). While the peak viral titer was generally observed on day 3 for HOSPs inoculated with any WNV genotype, peak viremias of individual birds occurred on different days. To determine the overall peak titer for each virus, the peak viral titer for individual HOSPs was determined irrespective of the day post-inoculation and then averaged. The peak titers also were averaged by viral genotype, and peak viral titer varied significantly by genotype. WN02 viruses induced a mean peak titer in HOSPs that was 10-fold greater than East Coast viruses (Fig. 2a, p<0.05). SW03 viruses produced a similar 10-fold increase in mean peak viral titer over East Coast viruses, though this difference was not significant (p = 0.09). This is likely due to the large amount of variation in viral titers observed from inoculated HOSPs (Fig. 2a).


Evidence for co-evolution of West Nile Virus and house sparrows in North America.

Duggal NK, Bosco-Lauth A, Bowen RA, Wheeler SS, Reisen WK, Felix TA, Mann BR, Romo H, Swetnam DM, Barrett AD, Brault AC - PLoS Negl Trop Dis (2014)

Peak viremias and mortality in HOSPs by viral isolate and over time.Points represent individual birds. HOSPs inoculated with East Coast viruses are designated in blue; HOSPs inoculated with WN02 viruses are designated in green; and HOSPs inoculated with SW03 viruses are designated in purple. (A) Peak serum titers for individual HOSPs inoculated with one of the 12 WNV isolates. Bars represent the mean peak titer for each WNV genotype. Error bars reflect the standard deviation of the mean. (B) Linear regression analysis of peak serum titer for individual birds inoculated with WNV, stratified by year of virus collection. 95% confidence intervals are shown by the dotted lines. (C) Percent HOSP survival for 7 days post-inoculation. Viral isolates are represented by dashed lines, and genotype means are represented by solid lines. *p<0.05.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4214623&req=5

pntd-0003262-g002: Peak viremias and mortality in HOSPs by viral isolate and over time.Points represent individual birds. HOSPs inoculated with East Coast viruses are designated in blue; HOSPs inoculated with WN02 viruses are designated in green; and HOSPs inoculated with SW03 viruses are designated in purple. (A) Peak serum titers for individual HOSPs inoculated with one of the 12 WNV isolates. Bars represent the mean peak titer for each WNV genotype. Error bars reflect the standard deviation of the mean. (B) Linear regression analysis of peak serum titer for individual birds inoculated with WNV, stratified by year of virus collection. 95% confidence intervals are shown by the dotted lines. (C) Percent HOSP survival for 7 days post-inoculation. Viral isolates are represented by dashed lines, and genotype means are represented by solid lines. *p<0.05.
Mentions: To determine whether the WN02 displacement of the East Coast genotype was the result of viral adaptation to North American avian hosts, groups of HOSPs collected in 2012 and 2013 were inoculated with 12 WNV isolates representing the three North American genotypes: East Coast, WN02, and SW03 (Table 1). In total, seventy-two birds were collected and inoculated with WNV in 2012–2013, and viremias were measured daily for 7 days. As expected for wild-caught birds, there was considerable variability in viral titers among replicates within groups (Fig. 2a). While the peak viral titer was generally observed on day 3 for HOSPs inoculated with any WNV genotype, peak viremias of individual birds occurred on different days. To determine the overall peak titer for each virus, the peak viral titer for individual HOSPs was determined irrespective of the day post-inoculation and then averaged. The peak titers also were averaged by viral genotype, and peak viral titer varied significantly by genotype. WN02 viruses induced a mean peak titer in HOSPs that was 10-fold greater than East Coast viruses (Fig. 2a, p<0.05). SW03 viruses produced a similar 10-fold increase in mean peak viral titer over East Coast viruses, though this difference was not significant (p = 0.09). This is likely due to the large amount of variation in viral titers observed from inoculated HOSPs (Fig. 2a).

Bottom Line: West Nile virus (WNV) has been maintained in North America in enzootic cycles between mosquitoes and birds since it was first described in North America in 1999.Moreover, recently isolated WNV strains generate higher peak viremias and mortality in contemporary HOSPs compared to NY99.These data indicate that opposing selective pressures in both the virus and avian host have resulted in a net increase in the level of host competence of North American HOSPs for currently circulating WNV strains.

View Article: PubMed Central - PubMed

Affiliation: Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, United States of America.

ABSTRACT
West Nile virus (WNV) has been maintained in North America in enzootic cycles between mosquitoes and birds since it was first described in North America in 1999. House sparrows (HOSPs; Passer domesticus) are a highly competent host for WNV that have contributed to the rapid spread of WNV across the U.S.; however, their competence has been evaluated primarily using an early WNV strain (NY99) that is no longer circulating. Herein, we report that the competence of wild HOSPs for the NY99 strain has decreased significantly over time, suggesting that HOSPs may have developed resistance to this early WNV strain. Moreover, recently isolated WNV strains generate higher peak viremias and mortality in contemporary HOSPs compared to NY99. These data indicate that opposing selective pressures in both the virus and avian host have resulted in a net increase in the level of host competence of North American HOSPs for currently circulating WNV strains.

Show MeSH
Related in: MedlinePlus