Rapid detection of West Nile virus in fox squirrels ( Sciurus niger) using RAMP® test

Steve SchutzEric GhilarducciDamien ClausonMike McCoy

Uses of RAMP ®

� Rapid screening (same day/next day) of dead corvids (supplemental to PCR testing by CVEC)� Definitive test for crows; other species

testing negative were sent for PCR� Rapid screening of mosquito pools from

unregistered sites (supplemental to PCR testing by CVEC)

Why test squirrels?

� Appear to be susceptible to WNV� Fox squirrels abundant in

residential areas� Definitive indicator of local

transmission� Rapid screening could

provide a new surveillance tool

Methods

� Squirrels submitted by Lindsay Wildlife Museum as part of a collaborative project with Kerry Padgett, DHS� Transported to District lab� RAMP tested oral swabs

following standard corvidprocedures� All squirrels shipped to CAHFS

for necropsy, PCR tests conducted at CVEC

RAMP results: Squirrels

False–False+RAMP–RAMP+Tested

13 R<50(87%)0 R>0(0%)

0 R>50(0%)

1 R>0(7%)

13 R<50(87%) 8 R>0(53%)

2 R>50(13%)7 R>0(47%)

15

Squirrels, R>0

POSITIVE24.7NegativeConcordfox squirrelQ5-23310/21/2005

Negative19.9NegativeConcordfox squirrelQ5-23210/18/2005

POSITIVE>640POSITIVEMartinezfox squirrelQ5-22510/11/2005

POSITIVE19.0NegativeMartinezfox squirrelQ5-21310/4/2005

POSITIVE81.3POSITIVEPleasant Hillfox squirrelQ5-2019/28/2005

POSITIVE33.4NegativeWalnut Creekfox squirrelQ5-1959/26/2005

POSITIVE8.6NegativeConcordfox squirrelQ5-1969/26/2005

PCRRValRAMPCitySpeciesID NumDate

RAMP results: Corvids

False–False+RAMP–RAMP+Tested

16 R>50(24%)5 R>0(7.5%)

>=136 (54%)

31(46%)

67

1/13 (7.6%)

>=122 (71%)

9 (29%)

31

Summary of surveillance results

0.2%(1/419)

63%(27/43)

40% (18/45)

18% (3/17)

PCR

2%(3/149)

47%*(7/15)

46% (31/67)

29% (9/31)

RAMP

Mosquito pools

Squirrels*R>0

JaysCrows

*R>0

How useful was RAMP?

0

2

4

6

8

10

12

31-Ja

n11

-Feb

25-F

eb11

-Mar

25-M

ar8-

Apr22

-Apr

6-May

20-M

ay3-

Jun

17-Ju

n1-

Jul

15-Ju

l29

-Jul

12-A

ug26

-Aug

9-Sep

23-S

ep7-

Oct21

-Oct

1-Nov

# ca

ses

0

10

20

30

40

50

60

70

% p

os

human equine chicken mosquito % pos birds

Conclusions

� RAMP test shows promise for dead squirrel testing� May require modification of cutoff value or test

procedure� Adopting lower cutoff value may also improve

accuracy with jays and other non-crows� Ability to test/respond rapidly made up for

shortcomings� RAMP testing of birds and mosquito pools provided

effective early warning of high risk areas

Acknowledgment

� Kerry Padgett, DHS� Lindsay Wildlife Museum� Gary Bogue, Contra Costa

Times� Lab crew: Damien, Eric, Mike� Field technicians and

supervisors� CAHFS/CVEC