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Evaluation of novel dipstick assays for the detection of Rift Valley fever virus (RVFV) in mosquitoes. Michael Turell, Kirti Dave, Maria Mayda , Zahra Parker, Russell Coleman, and Daniel Strickman - PowerPoint PPT Presentation
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USAMRIIDUSAMRIID
Michael Turell, Kirti Dave, Maria Mayda, Zahra Parker, Russell Coleman, and Daniel Strickman US Army Medical Research Institute of Infectious Diseases, Fort
Detrick, MD; VecTOR Test Systems, Inc., Thousand Oaks, CA; Walter Reed Army Institute of Research, Silver Spring, MD; US Army Medical
Materiel Development Activity, Fort Detrick, MD; US Department of Agriculture, Agriculture Research Service, Beltsville, MD
Evaluation of novel dipstick assays for the detection of Rift Valley fever virus (RVFV) in mosquitoes
Opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the U.S. Army.
Research was conducted in compliance with the Animal Welfare Act and other federal statutes and regulations relating to animals and experiments involving animals and adheres to principles stated in the Guide for the Care and Use of Laboratory Animals, National Research Council, 1996. The facility where this research was conducted is fully accredited by the Association for the Assessment and Accreditation of Laboratory Animal Care International.
Overview of RVFV
POTENTIAL FOR BECOMING ESTABLISHED IN NORTH AMERICA
Many North American mosquito species are potential vectors of RVF virus
Ample supply of susceptible domestic vertebrate hosts (cattle, goat, sheep)
Role of deer, horses, rodents, etc. is not known
AVAILABLE DIAGNOSTIC ASSAYS
Research Laboratory based• RT-PCR• ELISA• Infectious virus assays (cell culture)
Commercially available• None
Negative control
Positive “Control” line
“Test” line
RVFV-infected mosquito
Schematic side view of test strip
<3<33.5
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GenomeEquivalents
Sample number Dipstick CT Value Virus titer247 0 29.4 0250 0 29.2 0261 0 29.3 0262 0 29.1 0265 0 28.9 0270 0 28.9 0267 0 28.2 1253 0 28.6 1.7251 +/- 27.8 1.8260 0 30.2 2269 0 28.6 2.5255 0 27.8 2.8266 0 26.9 3248 +/- 29.3 3.3268 0 27.9 3.3264 0 25.5 3.7256 0 25.4 3.8257 0 25.5 4233 0 24.8 4.2240 +/- 23.4 4.2243 + 23.0 4.3254 +/- 23.7 4.3235 ?? 24.0 4.5236 + 27.1 4.6252 ?? 25.2 4.7258 0 25.4 4.7244 0 25.3 5246 + 25.2 5.1239 +++ 22.8 5.2271 +/- 24.6 5.2234 +++ 22.3 5.3241 ++ 21.9 5.3242 ++ 25.3 5.5238 +++ 21.7 5.6237 +++ 21.1 5.7249 ++ 21.2 5.8263 ++ 20.2 6259 ++ 21.3 6.2
Sensitivity of the dipstick based on the amount of infectious virus present
TiterNumber tested Negative Positive ?
>5.0 10 0 9 (90%) 1
4.5-5.0 5 2 1 (20%) 2
<4.5 22 18 0 (0%) 4
Sensitivity of the dipstick based on the CT (RT-PCR) value
CT value
Number tested Negative Positive ?
<23 25 2 23 (92%) 0
23-25.3 12 4 3 (25%) 5
>25.3 35 31 2 (6%) 2
RVF D-1 RVFWNSLE VEE JE D-2 D-3 D-4
SpecificityDengue 1-4Japanese encephalitis La Crosse St. Louis encephalitisVenezuelan equine encephalitis West Nile Yellow fever
Strains of RVFV tested
OS-1 MauritaniaRhod 2269/74 ZimbabweAr-B 1976 Central African Republic21445 KenyaZH501 Egypt
Strain Where isolated
Summary
• The newly developed dipsticks for RVFV are about as sensitive as the VecTest ® West Nile virus dipstick
Summary
• The newly developed dipsticks for RVFV are about as sensitive as the VecTest ® West Nile virus dipstick
• The RVFV dipstick detected virus in nearly all samples containing 105 plaque-forming units of virus.
Summary• The newly developed dipsticks for RVFV are
about as sensitive as the VecTest ® West Nile virus dipstick
• The RVFV dipstick detected virus in nearly all samples containing 105 plaque-forming units of virus.
• There was a strong correlation between the infectious virus assay titer and the CT value