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Studies of pathogen transmission typically overlook that wildlife hosts can include both migrant and resident populations when attempting to model circulation. Through the application of stable isotopes in flight feathers, we estimated the migration strategy of mallards ( Anas platyrhynchos) occurring on California wintering grounds. Our study demonstrates that mallards- a principal host of avian influenza virus ( AIV) in nature, contribute differently to virus gene flow depending on migration strategy. No difference in AIV prevalence was detected between resident (9.6%), intermediate-distance (9.6%) and long-distance migrants (7.4%). Viral diversity among the three groups was also comparable, possibly owing to viral pool mixing when birds converge at wetlands during winter. However, migrants and residents contributed differently to the virus gene pool at wintering wetlands. Migrants introduced virus from northern breeding grounds ( Alaska and the NW Pacific Rim) into the wintering population, facilitating gene flow at continental scales, but circulation of imported virus appeared to be limited. In contrast, resident mallards acted as AIV reservoirs facilitating year-round circulation of limited subtypes (i.e. H5 N2) at lower latitudes. This study supports a model of virus exchange in temperate regions driven by the convergence of wild birds with separate geographic origins and exposure histories. [ABSTRACT FROM AUTHOR]

The article focuses on a study which investigated the influence of avian influenza virus (AIV) on the behavior of Anatidae (ducks, geese, swans) at wintering sites in California. The study included 3,487 species at Sacramento National Wildlife Refuge and Conaway Ranch Duck Club during the hunting season of 2007-08. AIV was found to be most prevalent among northern shoveler, then followed by ring-necked duck, American wigeon, bufflehead and greater white-fronted goose. Study authors concluded that AIV occurrence and the ecological traits of Anatidae are related.

Abstract: Many theories about the modes of avian influenza virus (AIV) transmission have been proposed, but few have been quantified, and none within a flock or live bird market (LBM) setting where birds are often kept in stacked cages. We describe a novel experimental design and the results collected for the purpose of estimating transmission rates specific to the potential modes of AIV transmission within an LBM. Chickens of the strains and ages found in California LBMs were inoculated with low pathogenicity AIV H6N2. Aerosol exposure was found to be the most important route of transmission for this H6N2 AIV. The handling of infectious chickens resulted in the transmission of H6N2 AIV, though the virus was not detectible by rRT-PCR. Chickens with fecal exposure to infected birds (median=8.0 DPI) had detectable virus earlier than in those with aerosol exposure only (median=10.0 DPI). Changes in the hemagglutinin sequence were not found to be associated with oropharyngeal or cloacal shedding in this study. [Copyright &y& Elsevier]

The spread of avian influenza viruses (AIV) in nature is intrinsically linked with the movements of wild birds. Wild birds are the reservoirs for the virus and their migration may facilitate the circulation of AIV between breeding and wintering areas. This cycle of dispersal has become widely accepted; however, there are few AIV studies that present cross-seasonal information. A flyway perspective is critical for understanding how wild birds contribute to the persistence of AIV over large spatial and temporal scales, with implications for how to focus surveillance efforts and identify risks to public health. This study characterized spatio-temporal infection patterns in 10,389 waterfowl at two important locations within the Pacific Flyway--breeding sites in Interior Alaska and wintering sites in California's Central Valley during 2007-2009. Among the dabbling ducks sampled, the northern shoveler (Anas clypeata) had the highest prevalence of AIV at both breeding (32.2%) and wintering (5.2%) locations. This is in contrast to surveillance studies conducted in other flyways that have identified the mallard (Anas platyrhynchos) and northern pintail (Anas acuta) as hosts with the highest prevalence. A higher diversity of AIV subtypes was apparent at wintering (n=42) compared with breeding sites (n=17), with evidence of mixed infections at both locations. Our study suggests that wintering sites may act as an important mixing bowl for transmission among waterfowl in a flyway, creating opportunities for the reassortment of the virus. Our findings shed light on how the dynamics of AIV infection of wild bird populations can vary between the two ends of a migratory flyway.

Wild birds have been implicated in the spread of highly pathogenic avian influenza (HPAI) of the H5N1 subtype, prompting surveillance along migratory flyways. Sampling of wild birds for avian influenza virus (AIV) is often conducted in remote regions, but results are often delayed because of the need to transport samples to a laboratory equipped for molecular testing. Real-time reverse transcriptase polymerase chain reaction (rRT-PCR) is a molecular technique that offers one of the most accurate and sensitive methods for diagnosis of AIV. The previously strict lab protocols needed for rRT-PCR are now being adapted for the field. Development of freeze-dried (lyophilized) reagents that do not require cold chain, with sensitivity at the level of wet reagents has brought on-site remote testing to a practical goal. Here we present a method for the rapid diagnosis of AIV in wild birds using an rRT-PCR unit (Ruggedized Advanced Pathogen Identification Device or RAPID, Idaho Technologies, Salt Lake City, UT) that employs lyophilized reagents (Influenza A Target 1 Taqman; ASAY-ASY-0109, Idaho Technologies). The reagents contain all of the necessary components for testing at appropriate concentrations in a single tube: primers, probes, enzymes, buffers and internal positive controls, eliminating errors associated with improper storage or handling of wet reagents. The portable unit performs a screen for Influenza A by targeting the matrix gene and yields results in 2-3 hours. Genetic subtyping is also possible with H5 and H7 primer sets that target the hemagglutinin gene. The system is suitable for use on cloacal and oropharyngeal samples collected from wild birds, as demonstrated here on the migratory shorebird species, the western sandpiper (Calidrus mauri) captured in Northern California. Animal handling followed protocols approved by the Animal Care and Use Committee of the U.S. Geological Survey Western Ecological Research Center and permits of the U.S. Geological Survey Bird Banding Laboratory. The primary advantage of this technique is to expedite diagnosis of wild birds, increasing the chances of containing an outbreak in a remote location. On-site diagnosis would also prove useful for identifying and studying infected individuals in wild populations. The opportunity to collect information on host biology (immunological and physiological response to infection) and spatial ecology (migratory performance of infected birds) will provide insights into the extent to which wild birds can act as vectors for AIV over long distances.

Oropharyngeal and cloacal swabs were collected from poultry sold in two live bird market (LBM) systems to estimate the prevalence of low pathogenicity avian influenza virus (LPAIV) shedding during the summer and fall of 2005. Random sampling was conducted in three LBMs in Minnesota where 50 birds were sampled twice weekly for 4 wk, and in three LBMs in a California marketing system. A stratified systematic sampling method was used to collect samples from Southern California LBMs, where LPAIV was detected during routine surveillance. No LPAIV was detected in the LBM system in Minnesota where realtime reverse transcription-PCR (RT-PCR) was conducted on oropharyngeal samples. RT-PCR was performed on swabs taken from 290 of 14,000, 65 of 252, and 60 of 211 birds at the three Southern California LBMs. The number of samples collected was based on the number of birds, age of the birds, and number of species present in the LBM. Virus isolation, subtyping, and sequencing of the hemagglutinin, neuraminidase, and other internal protein genes was performed on AIV-positive samples. The estimated prevalence of LPAIV in California was 0.345% in an LBM/supply farm with multiple ages of Japanese quail, 3% in an LBM with multiple ages and strains of chickens present, and 49.8% in an LBM with multiple species, multiple strains, and multiple ages. The positive virus samples were all LPAIV H6N2 and closely related to viruses isolated from Southern California in 2001 and 2004. Little or no comingling of poultry may contribute to little or no LPAIV detection in the LBMs.

Wild birds have been implicated in the spread of highly pathogenic avian influenza (HPAIV) of the H5N1 subtype, prompting surveillance along migratory flyways. Sampling of wild birds is often conducted in remote regions, but results are often delayed because of limited local analytical capabilities, difficulties with sample transportation and permitting, or problems keeping samples cold in the field. In response to these challenges, the performance of a portable real-time, reverse transcriptase-polymerase chain reaction (rRT-PCR) unit (RAPID((R)), Idaho Technologies, Salt Lake City, UT) that employed lyophilized reagents (Influenza A Target 1 Taqman; ASAY-ASY-0109, Idaho Technologies) was compared to virus isolation combined with real-time RT-PCR conducted in a laboratory. This study included both field- and experimental-based sampling. Field samples were collected from migratory shorebirds captured in northern California, while experimental samples were prepared by spiking fecal material with an H6N2 AIV isolate. Results indicated that the portable rRT-PCR unit had equivalent specificity to virus isolation with no false positives, but sensitivity was compromised at low viral titers. Use of portable rRT-PCR with lyophilized reagents may expedite surveillance results, paving the way to a better understanding of wild bird involvement in HPAIV H5N1 transmission., (Published by Elsevier B.V.)

House flies (Musca domestica) and little house flies (Fannia canicularis) were examined for their ability to take up and harbor a velogenic strain of exotic Newcastle disease virus (ENDV) (family Paramyxoviridae, genus Avulavirus). Laboratory-reared flies were allowed to feed on evaporated milk containing ENDV at a virus concentration of 10(8.3) egg infectious dose (EID)50/0.1 ml or on poultry feces containing an ENDV titer of 10(5.8) EID50/0.1 g. Flies exposed to either infectious food source for 24 hr became transiently infected with virus. Virus persisted predominantly in the mid- and hindgut, with relatively little virus isolated from the remainder of the fly body. Virus persisted similarly in both fly species that were fed evaporated milk containing ENDV, with a maximum ENDV titer of 10(5.98) EID50/fly for the house fly and 10(4.78) EID50/fly for the little house fly at 1 day postexposure; titers decreased on subsequent days to 10(2.38) EID50/fly for house fly and > or = 1 EID50/fly for little house fly at 5 days postexposure. Both fly species acquired viral titers greater than the infective dose for a susceptible chicken (10(3.0) EID50-10(4.0) EID50). In addition, flies fed evaporated milk containing a high titer of ENDV maintained viral titers above the infective dose for up to 4 days postexposure to the infectious food source. Flies fed on infective feces retained a chicken infective dose for only one day. The decrease in viral titer over time was significantly explained by logistic regression for both fly species (P < 0.05). The slope of the regression line was not different for the two fly species (P < 0.05), indicating a similar rate of virus loss.

Although live bird markets (LBMs) have been associated with outbreaks of avian influenza (AI), there are some LBM systems where AI outbreaks are extremely rare events. The California LBMs have not had any detected avian influenza viruses (AIVs) since December 2005. Responses to a detailed questionnaire on the practices and characteristics of the participants in the California low-pathogenic (LP) AI control program have been described to characterize possible reasons for the lack of AI outbreaks in LBMs. Compliance with an LPAI control program that contains active surveillance, prevention, and rapid response measures by those involved in the LBM system, rendering services to dispose of carcasses, no wholesalers, and few third-party bird deliveries was associated with the lack of LPAIV circulating in the Southern California LBM system.

Since the reemergence of highly pathogenic avian influenza (H5N1 HPAI) in 2003, a panzootic that is historically unprecedented in the number of infected flocks, geographic spread, and economic consequences for agriculture has developed. The epidemic has affected a wide range of birds and mammals, including humans. The ineffective management of outbreaks, mainly due to a lack of knowledge among those involved in detection, prevention, and response, points to the need for training on H5N1 HPAI. The main challenges are the multidisciplinary approach required, the lack of experts, the need to train at all levels, and the diversity of outbreak scenarios. Avian Flu School addresses these challenges through a three-level train-the-trainer program intended to minimize the health and economic impacts of H5N1 HPAI by improving a community's ability to prevent and respond, while protecting themselves and others. The course teaches need-to-know facts using highly flexible, interactive, and relevant materials.

Flies were collected by sweep net from the vicinity of two small groups of "backyard" poultry (10-20 chickens per group) that had been identified as infected with exotic Newcastle disease virus (family Paramyxoviridae, genus avulavirus, ENDV) in Los Angeles County, CA, during the 2002-2003 END outbreak. Collected flies were subdivided into pools and homogenized in brain-heart infusion broth with antibiotics. The separated supernatant was tested for the presence of ENDV by inoculation into embryonated chicken eggs. Exotic Newcastle disease virus was isolated from pools of Phaenicia cuprina (Wiedemann), Fannia canicularis (L.), and Musca domestica L., and it was identified by hemagglutination inhibition with Newcastle disease virus antiserum. Viral concentration in positive pools was low (<1 egg infectious dose50 per fly). Isolated virus demonstrated identical monoclonal antibody binding profiles as well as 99% sequence homology in the 635-bp fusion gene sequence compared with ENDV recovered from infected commercial egg layer poultry during the 2002 outbreak.

The California 99 (Cal99) variant of infectious bronchitis virus (IBV) was first recovered in 1999 from vaccinated broiler chicken flocks in Central California. The S1 hypervariable region of Cal99 genome was most closely related to Arkansas (Ark) serotype viruses. In this study, the complete genome of Cal99 was sequenced, and the structural protein genes were compared with those of commonly used IBV vaccines as well as those of isolates from naturally occurring outbreaks in different parts of the world, to elucidate potential sources of genetic material. Based on sequence comparison, the prototype Cal99 virus is similar to the apathogenic ArkDPI virus, except in the S1 gene and stretches of sequence in the S2 and M structural protein genes, which are more related to Connecticut (Conn) and Massachusetts (Mass) strain viruses, respectively. We speculate that these two fragments came from a Conn and a Mass virus, respectively, and were incorporated into a virus largely derived from ArkDPI. Since Ark, Conn and Mass strains have been simultaneously used as live vaccines in California, both point mutations and recombination among vaccine strains may have contributed to the emergence of the Cal99 variant virus. Analysis of the structural protein genes of six Cal99 isolates demonstrated that viruses of this serotype may differ substantially in the non-S1 structural genes. Finally, we performed a challenge study with Cal99 and demonstrated that the virus causes late-onset respiratory disease, with a severity comparable to that of the M41 IBV challenge strain.

This report chronicles recurring outbreaks of Haemoproteus lophortyx infection in captive bobwhite quail. Clinically, the signs of infection included reluctance to move, ruffled appearance, prostration, and death. These signs were associated with parasitemia, anemia, and the presence of large megaloschizonts in skeletal muscles, particularly those of the thighs and back. The average cumulative mortality for flocks experiencing outbreaks was over 20%. In a typical outbreak, mortality rose when the birds were 5-6 wk of age, peaked in 8-to-10-wk-old quail, and declined rapidly when the quail were 9-11 wk old. Outbreaks occurred exclusively between the months of May and October, and warm weather was determined to be a risk factor for H. lophortyx mortality. This protozoan most likely overwinters in native California quail in the area and is transmitted to quail on the ranch by an insect vector that emerges in warm weather. Infection of the large population of naïve bobwhite quail on the ranch leads to amplification of H. lophortyx, resulting in epidemics in successive flocks.