Ability of transstadially infected Ixodes pacificus (Acari: Ixodidae) to transmit West Nile virus to song sparrows or western fence lizards

William Reisen, Aaron Brault, V. M. Martinez, Y. Fang, K. Simmons, S. Garcia, E. Omi-Olsen, R. S. Lane

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

The hypothesis that Ixodes pacificus Cooley & Kohls (Acari: Ixodidae) may serve as a reservoir and vector of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) in California was tested by determining the ability of this tick species to become infected with the NY99 strain of WNV while feeding on viremic song sparrows, to maintain the infection transstadially, and then to transmit WNV to recipient naive song sparrows and western fence lizards during the nymphal stage. The percentage of ticks testing positive by reverse transcription-polymerase chain reaction (RT-PCR) decreased from 77% of 35 larvae at day 6 after ticks were transferred to donor song sparrows (day of detachment) to 23% of 35 nymphs at 59 d postinfestation (≈19 d after molting to the nymphal stage). However, the percentage of ticks positive by RT-PCR from which infectious virus was recovered by Vero cell assay decreased from 59% on day 6 to 12% on day 59, even though there was no statistically significant decrease in the quantity of RNA within positive ticks. Attempts to improve the sensitivity of plaque assays by blind passage through C6/36 cell cultures were unsuccessful. These data indicated that ticks maintained viral RNA but not necessarily infectious virus over time. Nymphs from larvae that fed on song sparrows with peak viremias ranging from 7.2 to 8.5 log10 plaque-forming units (PFU) per ml were used in transmission attempts. From one to seven RNA-positive nymphal ticks engorged and detached from each of four recipient song sparrows or western fence lizards. Blood samples from sparrows and lizards remained negative, indicating that transmission did not occur. An additional four lizards inoculated with 1,500 PFU of WNV developed moderate viremias, ranging from 4.2 to 5.6 log10 PFU/ml. Our data and data from previous studies collectively indicated that ixodid ticks were not able to experimentally transmit WNV and therefore most likely would not be important vectors in WNV transmission cycles.

Original languageEnglish (US)
Pages (from-to)320-327
Number of pages8
JournalJournal of Medical Entomology
Volume44
Issue number2
StatePublished - Mar 1 2007

Fingerprint

Sceloporus occidentalis
Ixodes pacificus
Sparrows
Ixodidae
West Nile virus
Ixodes
Passeriformes
Lizards
Ticks
Music
animal communication
ticks
Acari
Nymph
Viremia
viremia
RNA
Reverse Transcription
nymphs
Larva

Keywords

  • Ixodes pacificus
  • Song sparrow
  • Transmission
  • West fence lizard
  • West Nile virus

ASJC Scopus subject areas

  • Parasitology
  • veterinary(all)
  • Insect Science
  • Infectious Diseases

Cite this

Ability of transstadially infected Ixodes pacificus (Acari : Ixodidae) to transmit West Nile virus to song sparrows or western fence lizards. / Reisen, William; Brault, Aaron; Martinez, V. M.; Fang, Y.; Simmons, K.; Garcia, S.; Omi-Olsen, E.; Lane, R. S.

In: Journal of Medical Entomology, Vol. 44, No. 2, 01.03.2007, p. 320-327.

Research output: Contribution to journalArticle

@article{41e14b32b2174da89b45c5700fc97342,
title = "Ability of transstadially infected Ixodes pacificus (Acari: Ixodidae) to transmit West Nile virus to song sparrows or western fence lizards",
abstract = "The hypothesis that Ixodes pacificus Cooley & Kohls (Acari: Ixodidae) may serve as a reservoir and vector of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) in California was tested by determining the ability of this tick species to become infected with the NY99 strain of WNV while feeding on viremic song sparrows, to maintain the infection transstadially, and then to transmit WNV to recipient naive song sparrows and western fence lizards during the nymphal stage. The percentage of ticks testing positive by reverse transcription-polymerase chain reaction (RT-PCR) decreased from 77{\%} of 35 larvae at day 6 after ticks were transferred to donor song sparrows (day of detachment) to 23{\%} of 35 nymphs at 59 d postinfestation (≈19 d after molting to the nymphal stage). However, the percentage of ticks positive by RT-PCR from which infectious virus was recovered by Vero cell assay decreased from 59{\%} on day 6 to 12{\%} on day 59, even though there was no statistically significant decrease in the quantity of RNA within positive ticks. Attempts to improve the sensitivity of plaque assays by blind passage through C6/36 cell cultures were unsuccessful. These data indicated that ticks maintained viral RNA but not necessarily infectious virus over time. Nymphs from larvae that fed on song sparrows with peak viremias ranging from 7.2 to 8.5 log10 plaque-forming units (PFU) per ml were used in transmission attempts. From one to seven RNA-positive nymphal ticks engorged and detached from each of four recipient song sparrows or western fence lizards. Blood samples from sparrows and lizards remained negative, indicating that transmission did not occur. An additional four lizards inoculated with 1,500 PFU of WNV developed moderate viremias, ranging from 4.2 to 5.6 log10 PFU/ml. Our data and data from previous studies collectively indicated that ixodid ticks were not able to experimentally transmit WNV and therefore most likely would not be important vectors in WNV transmission cycles.",
keywords = "Ixodes pacificus, Song sparrow, Transmission, West fence lizard, West Nile virus",
author = "William Reisen and Aaron Brault and Martinez, {V. M.} and Y. Fang and K. Simmons and S. Garcia and E. Omi-Olsen and Lane, {R. S.}",
year = "2007",
month = "3",
day = "1",
language = "English (US)",
volume = "44",
pages = "320--327",
journal = "Journal of Medical Entomology",
issn = "0022-2585",
publisher = "Entomological Society of America",
number = "2",

}

TY - JOUR

T1 - Ability of transstadially infected Ixodes pacificus (Acari

T2 - Ixodidae) to transmit West Nile virus to song sparrows or western fence lizards

AU - Reisen, William

AU - Brault, Aaron

AU - Martinez, V. M.

AU - Fang, Y.

AU - Simmons, K.

AU - Garcia, S.

AU - Omi-Olsen, E.

AU - Lane, R. S.

PY - 2007/3/1

Y1 - 2007/3/1

N2 - The hypothesis that Ixodes pacificus Cooley & Kohls (Acari: Ixodidae) may serve as a reservoir and vector of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) in California was tested by determining the ability of this tick species to become infected with the NY99 strain of WNV while feeding on viremic song sparrows, to maintain the infection transstadially, and then to transmit WNV to recipient naive song sparrows and western fence lizards during the nymphal stage. The percentage of ticks testing positive by reverse transcription-polymerase chain reaction (RT-PCR) decreased from 77% of 35 larvae at day 6 after ticks were transferred to donor song sparrows (day of detachment) to 23% of 35 nymphs at 59 d postinfestation (≈19 d after molting to the nymphal stage). However, the percentage of ticks positive by RT-PCR from which infectious virus was recovered by Vero cell assay decreased from 59% on day 6 to 12% on day 59, even though there was no statistically significant decrease in the quantity of RNA within positive ticks. Attempts to improve the sensitivity of plaque assays by blind passage through C6/36 cell cultures were unsuccessful. These data indicated that ticks maintained viral RNA but not necessarily infectious virus over time. Nymphs from larvae that fed on song sparrows with peak viremias ranging from 7.2 to 8.5 log10 plaque-forming units (PFU) per ml were used in transmission attempts. From one to seven RNA-positive nymphal ticks engorged and detached from each of four recipient song sparrows or western fence lizards. Blood samples from sparrows and lizards remained negative, indicating that transmission did not occur. An additional four lizards inoculated with 1,500 PFU of WNV developed moderate viremias, ranging from 4.2 to 5.6 log10 PFU/ml. Our data and data from previous studies collectively indicated that ixodid ticks were not able to experimentally transmit WNV and therefore most likely would not be important vectors in WNV transmission cycles.

AB - The hypothesis that Ixodes pacificus Cooley & Kohls (Acari: Ixodidae) may serve as a reservoir and vector of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) in California was tested by determining the ability of this tick species to become infected with the NY99 strain of WNV while feeding on viremic song sparrows, to maintain the infection transstadially, and then to transmit WNV to recipient naive song sparrows and western fence lizards during the nymphal stage. The percentage of ticks testing positive by reverse transcription-polymerase chain reaction (RT-PCR) decreased from 77% of 35 larvae at day 6 after ticks were transferred to donor song sparrows (day of detachment) to 23% of 35 nymphs at 59 d postinfestation (≈19 d after molting to the nymphal stage). However, the percentage of ticks positive by RT-PCR from which infectious virus was recovered by Vero cell assay decreased from 59% on day 6 to 12% on day 59, even though there was no statistically significant decrease in the quantity of RNA within positive ticks. Attempts to improve the sensitivity of plaque assays by blind passage through C6/36 cell cultures were unsuccessful. These data indicated that ticks maintained viral RNA but not necessarily infectious virus over time. Nymphs from larvae that fed on song sparrows with peak viremias ranging from 7.2 to 8.5 log10 plaque-forming units (PFU) per ml were used in transmission attempts. From one to seven RNA-positive nymphal ticks engorged and detached from each of four recipient song sparrows or western fence lizards. Blood samples from sparrows and lizards remained negative, indicating that transmission did not occur. An additional four lizards inoculated with 1,500 PFU of WNV developed moderate viremias, ranging from 4.2 to 5.6 log10 PFU/ml. Our data and data from previous studies collectively indicated that ixodid ticks were not able to experimentally transmit WNV and therefore most likely would not be important vectors in WNV transmission cycles.

KW - Ixodes pacificus

KW - Song sparrow

KW - Transmission

KW - West fence lizard

KW - West Nile virus

UR - http://www.scopus.com/inward/record.url?scp=34247466579&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34247466579&partnerID=8YFLogxK

M3 - Article

C2 - 17427704

AN - SCOPUS:34247466579

VL - 44

SP - 320

EP - 327

JO - Journal of Medical Entomology

JF - Journal of Medical Entomology

SN - 0022-2585

IS - 2

ER -