single cloacal swabs were collected from apparently healthy ducks at 56 sites within 6 geographic regions : british columbia , alberta , manitoba , ontario , qubec , and the atlantic provinces ( new brunswick , nova scotia , prince edward island , and newfoundland and labrador ) ( figure ) . the target number of samples for each region was 800 : 500 from mallard ducks ( anas platyrhynchos ) and 300 from other duck species . ducks were trapped and handled as part of annual duck banding carried out by the canadian wildlife service and its associates . they were either caught in baited traps or netted from air boats . in all regions , duck banders were asked to preferentially sample birds hatched in 2005 to maximize virus detection within the sample ( 24 ) . swabs were immediately placed in virus transport medium , refrigerated for up to 3 days , and then frozen at < 20c until tested . the transport medium comprised hanks balanced salt solution supplemented with 10% glycerol , 200 u / ml penicillin , 200 g / ml streptomycin , 100 u / ml polymyxin b sulfate , 250 g / ml gentamicin , and 50 u / ml nystatin . all samples were tested at regional veterinary diagnostic laboratories within canada 's influenza virus laboratory network by rrt - pcr , which targets a conserved region of the m1 gene within influenza a segment 7 . if the m1 gene sequence was detected , rrt - pcr for h5 and h7 hemagglutinin gene segments was performed . all laboratories followed uniform procedures ( 5 ) with positive and negative controls , and quality assurance was provided by the national centre for foreign animal disease ( canadian food inspection agency ) . all field and laboratory data were entered directly into a national database developed and maintained by the canadian cooperative wildlife health centre . duplicate records and any sample records missing rrt - pcr results or field collection data ( species , age , sex , location ) were removed from this analysis . statistical analysis was performed with epi - info version 3.3.2 ( centers for disease control and prevention , atlanta , ga , usa ) and sas version 9.1 ( sas institute inc . , maps were generated in arcgis 9.0arcmap version 9.1 ( esri , redlands , ca , usa ) . to assess differences in m1 and h5 virus detection by age class and species , age class , species , sampling area , and sex were included in the model . age class was categorized into 2005 hatch - year birds and birds from another hatch year . species was categorized into mallard ( mallard and mallard  american black duck [ a. rubripes ] hybrids ) , other dabbling duck species , diving ducks , and other tribes ( table 1 ) . all variables were assessed for potential confounding ; variables that changed estimates by > 20% were left in the main effects models as confounders ( 6 ) . * rrt - pcr , a total of 4,268 valid sample records were available for this analysis ; 37% ( 1,572 ) of ducks were m1-positive and 5% ( 208 ) were h5-positive by rrt - pcr . sampled areas varied considerably in the proportion of m1-positive samples , ranging from 63% ( 348/556 ) in southern quebec to 9% ( 22/254 ) in southern alberta ( table 2 ) . three percent ( 138 ) of samples were collected in july , 83% in august ( 3,539 ) , 11% ( 454 ) in september , 1% ( 59 ) in october , none in november , and 2% ( 73 ) in december . of all samples , 80% ( 3,401/4,268 ) were collected from ducks hatched in 2005 . hatch - year ducks accounted for 88% ( 1,388/1,572 ) of m1-positive and 99% ( 205/208 ) of h5-positive samples . of all ducks sampled , 90% ( 3,824/4,268 ) were dabbling ducks ( tribe anatini ) ( table 1 ) . mallards ( including mallard  american black duck hybrids ) accounted for 61% ( 2,600/4,268 ) of all ducks sampled , 73% ( 1,148/1,572 ) of all m1-positive samples , and 90% ( 187/208 ) of all h5-positive samples . the duck species with the highest proportion of m1-positive samples was the wood duck ( aix sponsa ) ( 68% , 71/104 ) . * rrt - pcr , real - time reverse transcriptase  pcr . new brunswick , nova scotia , prince edward island , and newfoundland and labrador . the sampling area of 8 ducks was not recorded ( 3 from alberta , 1 from ontario , 4 from qubec ) . age , area sampled , and species were included in the final logistic regression model for m1 rrt - pcr test results . age , sex , and species were included in the final model for h5 rrt - pcr results . mallards were more likely to be m1-positive than other dabbling ducks or diving ducks but not more likely to be m1-positive than other duck tribes ( cairinini and oxyurini ) . mallards were more likely to be h5-positive than other dabbling ducks , diving ducks , or other duck tribes . hatch - year ducks were 1.7 times more likely to be m1-positive and 13 times more likely to be h5-positive than older ducks . male ducks were 1.4 times more likely to test positive by h5 rrt - pcr than female ducks . these data provided a snapshot of the frequency and distribution of influenza a viruses in wild ducks across southern canada in 2005 . this unique nationwide snapshot showed wide variation in detection of m1 and h5 gene sequences among 6 regions that were broadly representative of the northern terminus of duck migration corridors in north america ( 7 ) . previous studies have focused on smaller subregions of canada sampled once or across multiple years ( 4,810 ) . considerable variation exists across studies in the age and species of birds sampled and seasonality of sampling . also , most previously published results relied on the cultivation of viable virus as the detection method rather than on rrt - pcr applied directly to cloacal swabs . because samples for this survey were secured from preestablished duck - banding operations , and young healthy ducks , particularly mallards , were targeted to maximize virus recovery ( 1,11,12 ) , these data may not represent true infection prevalence in the sampled duck populations . despite these biases , avian influenza viruses were common in wild ducks across canada in the summer and fall of 2005 . infection rates detected by rrt - pcr among the 6 regions of canada were similar in scale and degree of variation to rates reported from the alberta region , which were measured over 8 consecutive years from 1976 through 1983 ( 4 ) .
of 4,268 wild ducks sampled in canada in 2005 , real - time reverse transcriptase  pcr detected influenza a matrix protein ( m1 ) gene sequence in 37% and h5 gene sequence in 5% . 
 mallards accounted for 61% of samples , 73% of m1-positive ducks , and 90% of h5-positive ducks . 
 ducks hatched in 2005 accounted for 80% of the sample .