Isolation of influenza A viruses from wild ducks and feathers in Minnesota (2010-2011).

We investigated the feasibility of testing feathers as a complementary approach to detect low pathogenic influenza A viruses (IAVs) in wild duck populations. Feathers on the ground were collected at four duck capture sites during 2010 and 2011, in Minnesota, U. S. A. IAVs were isolated from both feathers and cloacal swabs sampled from ducks at the time of capture. Although virus isolation rates from feather and cloacal swabs were inconsistent between collections, the overall rate of isolation was greatest from the feather samples. Viruses isolated from feathers also reflected the subtype diversity observed in cloacal swab isolates but resulted in many more isolates that contained more than one virus. Our study suggests that testing feathers may represent an alternative noninvasive approach to recover viruses and estimate subtype abundance and diversity.

Influenza-A viruses in ducks in northwestern Minnesota: fine scale spatial and temporal variation in prevalence and subtype diversity.

Waterfowl from northwestern Minnesota were sampled by cloacal swabbing for Avian Influenza Virus (AIV) from July-October in 2007 and 2008. AIV was detected in 222 (9.1%) of 2,441 ducks in 2007 and in 438 (17.9%) of 2,452 ducks in 2008. Prevalence of AIV peaked in late summer. We detected 27 AIV subtypes during 2007 and 31 during 2008. Ten hemagglutinin (HA) subtypes were detected each year (i.e., H1, 3-8, and 10-12 during 2007; H1-8, 10 and 11 during 2008). All neuraminidase (NA) subtypes were detected during each year of the study. Subtype diversity varied between years and increased with prevalence into September. Predominant subtypes during 2007 (comprising ≥5% of subtype diversity) included H1N1, H3N6, H3N8, H4N6, H7N3, H10N7, and H11N9. Predominant subtypes during 2008 included H3N6, H3N8, H4N6, H4N8, H6N1, and H10N7. Additionally, within each HA subtype, the same predominant HA/NA subtype combinations were detected each year and included H1N1, H3N8, H4N6, H5N2, H6N1, H7N3, H8N4, H10N7, and H11N9. The H2N3 and H12N5 viruses also predominated within the H2 and H12 subtypes, respectively, but only were detected during a single year (H2 and H12 viruses were not detected during 2007 and 2008, respectively). Mallards were the predominant species sampled (63.7% of the total), and 531 AIV were isolated from this species (80.5% of the total isolates). Mallard data collected during both years adequately described the observed temporal and spatial prevalence from the total sample and also adequately represented subtype diversity. Juvenile mallards also were adequate in describing the temporal and spatial prevalence of AIV as well as subtype diversity.

Attractiveness of brown rice baits to non-target birds in harvested corn and soybean fields.

Brown rice is used as a bait-carrier for the avicide DRC-1339 (3-chloro-4-methylaniline) when baiting blackbirds (Icteridae). In March and April 1996 and 1997, we assessed non-target granivorous bird use of rice-baited plots placed in harvested corn and soybean fields in eastern South Dakota for 168 observation hours. In both years combined, we identified 10 and 14 granivorous species in corn and soybean fields, respectively. In 1996 (X = 0.2, SE = 0.04) and 1997 (X = 1.2, SE = 0.38), total numbers of granivores min(-1) were similar between crops (P > or = 0.322). In 1996, bird numbers were higher (P = 0.069) in rice-baited fields (X = 0.3, SE = 0.07) than in unbaited reference fields (X = 0.1, SE = 0.04). In 1997, bird numbers (X = 1.2, SE = 0.38) did not differ between treatments (P = 0.456). Our data show that small numbers of non-target birds visited the rice-baited plots. However, total number of different individual birds using the plots was unknown.