in february  october 2002 , as part of a broader study , we captured , banded , and marked 156 american crows ( c. brachyrhynchos ) in champaign and urbana , illinois ( yaremych sa .
many of the study crows died in the summer ; all recovered crows were tested for wnv .
dead crows were retrieved by tracking the radio signal to the carcasses , by chance encounter , or by notification from the public .
dead study crows with transmitters were typically recovered < 36 hours after death , as this period was the maximum amount of time elapsed between the last live observation of a crow during radio tracking and recovery of the carcass upon death .
we estimated that other marked study crows without transmitters were retrieved up to 72 hours after death . the abundance of dead crows allowed for a simple comparative study involving the use of vectest , rt - pcr , and ihc tests to detect wnv in crow fecal , saliva , and tissue samples .
for each dead crow , we diluted fecal scrapings from the cloaca and salivary scrapings from the mouth in vectest buffer solution in the vials provided in the kit .
a metal spatula was used to obtain samples , and instruments were sanitized with a wash of soap and water and 70% ethanol before and after use . in some cases ,
maggots were in such abundance in the mouth and cloaca that they could not be removed from the sample ; they were added to the vials with the feces and saliva . for carcasses with no moist fecal or saliva sample ,
small metal scissors were used to clip any available dried internal tissues around the mouth and cloaca .
samples were shaken by hand for approximately 60 seconds for homogenization . from this point , we followed manufacturer s directions , having replaced mosquitoes with fecal , saliva , and tissue samples .
indicator strips were inserted into the solution and interpreted in the field after 15 minutes .
samples were stored at 80c after we performed the test . to confirm the results , we used rt - pcr taqman to detect the presence or absence of wnv - rna in these samples by a method similar to that used by lanciotti et al .
alternatively , vectest results were confirmed by ihc testing of the brain , heart , kidney , and spleen of the crow carcass from which the samples were derived .
the ihc testing was conducted by the university of illinois veterinary diagnostic laboratory , according to the method outlined by heinz - taheny et al ( 7 ) .
we used vectest to test all 20 crow samples ; all indicator strips developed control lines , which indicated that the test had performed according to instructions .
nineteen samples were positive for wnv with a faint - to - bold wnv line ; one sample was negative for wnv .
ihc testing was performed on the crow carcasses from which five of these positive samples were derived , and ihc labeling for wnv antigen was present in all five of these samples , indicating 100% confirmation of the vectest results .
the remaining 15 vials containing the vectest crow sample , composed of 14 positives and 1 negative , were assayed by rt - pcr taqman .
results from taqman showed 11 positives and 4 negatives ( table ) . in total , 17 ( 85% ) of 20 of the vectest results were confirmed with either ihc or rt - pcr taqman , and 3 ( 15% ) of 20 involved conflicting results between the two testing methods for the samples .
no significant difference existed between the positive and negative rates of vectest and rt - pcr in a chi - square analysis of a 2x2 contingency table ( chi square = 2.16 , df=1 , p=0.14 ) . using rt - pcr as the standard criterion
, we found that vectest results included three false positives , yielding a false - positive rate of 75% .
vectest west nile virus / saint louis encephalitis virus antigen panel assay ( medical analysis systems inc .
reverse transcriptase polymerase chain reaction ; taqman ( applied biosystems , foster city , ca ) .
although the rates of positives and negatives did not differ between vectest and rt - pcr in this study , this result may be an artifact of small sample size .
the false - positive vectest results on american crow fecal , saliva , and tissue samples suggest a low specificity ; therefore , we recommend that vectest be considered experimental in its application to dead american crows until more extensive investigations are conducted .
vectest may be useful in early season screening , when rates of positives are typically low , or in nonpeak areas .
we conducted this study in mid- to late summer in east - central illinois , during a time when death rates of free - ranging american crows were high .
rt - pcr detects genomic sequences of wnv , whereas vectest detects the viral capsid .
because of the abundance of environmental rnaase and the possibility of the wnv capsid s persisting longer than the rna , the three false positives detected by vectest may indeed contain wnv capsid .
alternately , the conjugate in vectest may react with a nonspecific protein in the fecal , saliva , or tissue samples of the dead crows to create a false positive .
this preliminary investigation establishes the basis for more comprehensive research on the full capabilities of this test for wnv detection in birds , including the sensitivity of the test , the postmortem period for which the test is viable , and the effectiveness across a range of species .
we suggest that vectest may be a cost - effective , rapid field technique for wnv detection in dead american crows in the early transmission season or in areas with low transmission rates , although confirmation of positives is suggested at this time
. this assay may be a useful tool for epidemiologic studies of wnv transmission cycles involving american crows and will help to provide an epidemiologic basis for vector control efforts , although further study is warranted .
 a dipstick immunochromatographic assay used for west nile virus ( wnv ) detection in mosquitoes was investigated for application to testing of fecal , saliva , and tissue samples from dead american crows ( corvus brachyrhynchos ) . 
 results suggest that vectest may be an efficient method for wnv detection in field - collected , dead american crows , although confirmation of results and further investigation are warranted . 
The Study
Results
Conclusions