Kerri Pedersen

Surveillance for highly pathogenic avian influenza in wild birds in the USA

As part of the USAs National Strategy for Pandemic Influenza, an Interagency Strategic Plan for the Early Detection of Highly Pathogenic H5N1 Avian Influenza in Wild Migratory Birds was developed and implemented. From 1 April 2006 through 31 March 2009, 261,946 samples from wild birds and 101,457 wild bird fecal samples were collected in the USA; no highly pathogenic avian influenza was detected. The United States Department of Agriculture, and state and tribal cooperators accounted for 213,115 (81%) of the wild bird samples collected; 31, 27, 21 and 21% of the samples were collected from the Atlantic, Pacific, Central and Mississippi flyways, respectively. More than 250 species of wild birds in all 50 states were sampled. The majority of wild birds (86%) were dabbling ducks, geese, swans and shorebirds. The apparent prevalence of low pathogenic avian influenza viruses during biological years 2007 and 2008 was 9.7 and 11.0%, respectively. The apparent prevalence of H5 and H7 subtypes across all species sampled were 0.5 and 0.06%, respectively. The pooled fecal samples (n= 101,539) positive for low pathogenic avian influenza were 4.0, 6.7 and 4.7% for biological years 2006, 2007 and 2008, respectively. The highly pathogenic early detection system for wild birds developed and implemented in the USA represents the largest coordinated wildlife disease surveillance system ever conducted. This effort provided evidence that wild birds in the USA were free of highly pathogenic avian influenza virus (given the expected minimum prevalence of 0.001%) at the 99.9% confidence level during the surveillance period.

Characterization of Newcastle Disease Viruses Isolated from Cormorant and Gull Species in the United States in 2010

SUMMARY. Newcastle disease virus (NDV), a member of the genus Avulavirus of the family Paramyxoviridae, is the causative agent of Newcastle disease (ND), a highly contagious disease that affects many species of birds and which frequently causes significant economic losses to the poultry industry worldwide. Virulent NDV (vNDV) is exotic in poultry in the United States; however, the virus has been frequently associated with outbreaks of ND in cormorants, which poses a significant threat to poultry species. Here, we present the characterization of 13 NDV isolates obtained from outbreaks of ND affecting cormorants and gulls in the states of Minnesota, Massachusetts, Maine, New Hampshire, and Maryland in 2010. All 2010 isolates are closely related to the viruses that caused the ND outbreaks in Minnesota in 2008, following the new evolutionary trend observed in cormorant NDV isolates since 2005. Similar to the results obtained with the 2008 isolates, the standard United States Department of Agriculture F-gene real-time reverse-transcription PCR (RRT-PCR) assay failed to detect the 2010 cormorant viruses, whereas all viruses were detected by a cormorant-specific F-gene RRT-PCR assay. Notably, NDV-positive gulls were captured on the eastern shore of Maryland, which represents a significant geographic expansion of the virus since its emergence in North America. This is the first report of vNDV originating from cormorants isolated from wild birds in Maryland and, notably, the first time that genotype V vNDV has been isolated from multiple wild bird species in the United States. These findings highlight the need for constant epidemiologic surveillance for NDV in wild bird populations and for consistent biosecurity measures to prevent the introduction of the agent into domestic poultry flocks.

Environmental and Demographic Determinants of Avian Influenza Viruses in Waterfowl across the Contiguous United States

Outbreaks of avian influenza in North American poultry have been linked to wild waterfowl. A first step towards understanding where and when avian influenza viruses might emerge from North American waterfowl is to identify environmental and demographic determinants of infection in their populations. Laboratory studies indicate water temperature as one determinant of environmental viral persistence and we explored this hypothesis at the landscape scale. We also hypothesized that the interval apparent prevalence in ducks within a local watershed during the overwintering season would influence infection probabilities during the following breeding season within the same local watershed. Using avian influenza virus surveillance data collected from 19,965 wild waterfowl across the contiguous United States between October 2006 and September 2009 We fit Logistic regression models relating the infection status of individual birds sampled on their breeding grounds to demographic characteristics, temperature, and interval apparent prevalence during the preceding overwintering season at the local watershed scale. We found strong support for sex, age, and species differences in the probability an individual duck tested positive for avian influenza virus. In addition, we found that for every seven days the local minimum temperature fell below zero, the chance an individual would test positive for avian influenza virus increased by 5.9 percent. We also found a twelve percent increase in the chance an individual would test positive during the breeding season for every ten percent increase in the interval apparent prevalence during the prior overwintering season. These results suggest that viral deposition in water and sub-freezing temperatures during the overwintering season may act as determinants of individual level infection risk during the subsequent breeding season. Our findings have implications for future surveillance activities in waterfowl and domestic poultry populations. Further study is needed to identify how these drivers might interact with other host-specific infection determinants, such as species phylogeny, immunological status, and behavioral characteristics.

Surveillance of feral swine for Trichinella spp. and Toxoplasma gondii in the USA and host-related factors associated with infection

Trichinella spp. and Toxoplasma gondii are important zoonotic parasites that infect warm blooded animals and humans worldwide. Among domesticated food animals, pigs are the main host for Trichinella spiralis. Pigs, chickens, sheep, and goats are known to be infected with T. gondii at varying rates, depending on husbandry. Infections in wildlife with these parasites are generally higher than in domesticated species. Feral swine act as reservoirs of infection in the sylvatic ecosystem for Trichinella spp. and T. gondii, acting as sources of infection for peridomestic carnivores whose home ranges overlap with domestic pigs. Feral swine can have direct contact with non-biosecure domestic pigs, presenting opportunity for direct disease transmission through cannibalistic behavior. Determination of the prevalence of Trichinella spp. and T. gondii infection in feral swine is needed to understand the risk of transmission of these parasites to domestic pigs. A cross-sectional serological survey was conducted between 2006 and 2010 to estimate the antibody prevalence of Trichinella spp. and T. gondii and risk factors associated with infection in feral swine in the USA. Serum samples were tested from 3247 feral pigs from 32 states; results are reported from 26 states. Maximum entropy ecological niche modeling and spatial scan statistic were utilized to predict the geographic range and to examine clusters of infection of Trichinella spp. and T. gondii in feral pigs. The seroprevalence of antibodies to Trichinella spp. and T. gondii was 3.0% and 17.7%, respectively. Species distribution modeling indicated that the most probable distribution areas for both parasites was similar, concentrated primarily in the South and the Midwest regions of the USA. A follow up survey conducted during 2012-2013 revealed that 2.9% of 984 sampled feral swine were seropositive for Trichinella spp., and 28.4% were seropositive for T. gondii. Three hundred and thirty (330) tongues were collected from the 984 sampled animals during 2012-2013; 1.81% were tissue positive for T. spiralis muscle larvae; no other genotypes were found. The potential exists for introduction of these pathogens into domestic herds of non-biosecure domestic pigs as a result of increasing overlap of the range of feral pigs with non-biosecure domestic pigs production facilities in the USA.

Dissecting a wildlife disease hotspot: the impact of multiple host species, environmental transmission and seasonality in migration, breeding and mortality

Avian influenza viruses (AIVs) have been implicated in all human influenza pandemics in recent history. Despite this, surprisingly little is known about the mechanisms underlying the maintenance and spread of these viruses in their natural bird reservoirs. Surveillance has identified an AIV ‘hotspot’ in shorebirds at Delaware Bay, in which prevalence is estimated to exceed other monitored sites by an order of magnitude. To better understand the factors that create an AIV hotspot, we developed and parametrized a mechanistic transmission model to study the simultaneous epizootiological impacts of multi-species transmission, seasonal breeding, host migration and mixed transmission routes. We scrutinized our model to examine the potential for an AIV hotspot to serve as a ‘gateway’ for the spread of novel viruses into North America. Our findings identify the conditions under which a novel influenza virus, if introduced into the system, could successfully invade and proliferate.

Influenza A subtype H3 viruses in feral swine, United States, 2011-2012.

To determine whether, and to what extent, influenza A subtype H3 viruses were present in feral swine in the United States, we conducted serologic and virologic surveillance during October 2011–September 2012. These animals were periodically exposed to and infected with A(H3N2) viruses, suggesting they may threaten human and animal health.

Antibodies to Avian Influenza Viruses in Canada Geese (Branta canadensis): A Potential Surveillance Tool?

Traditionally, the epidemiology of avian influenza viruses (AIVs) in wild birds has been defined by detection of virus or viral RNA through virus isolation or reverse-transcription polymerase chain reaction. Our goals were to estimate AIV antibody prevalence in Canada geese (Branta canadensis) and measure effects of age and location on these estimates. We collected 3,205 samples from nine states during June and July 2008 and 2009: Georgia, Massachusetts, Minnesota, Mississippi, New Jersey, North Carolina, Pennsylvania, Washington, and West Virginia. Serum samples were tested for AIV antibodies with the use of a commercial blocking enzyme-linked immunosorbent assay. Overall, 483 (15%) Canada geese had detectable antibodies to AIV. Significantly higher prevalences were detected in geese collected from northeastern and upper midwestern states compared with southeastern states. This trend is consistent with results from virus isolation studies reporting AIV prevalence in North American dabbling ducks. Within Pennsylvania, significantly higher antibody prevalences were detected in goose flocks sampled in urban locations compared to flocks sampled in rural areas. Antibody prevalence was significantly higher in after-hatch-year geese compared to hatch-year geese. No significant differences in prevalence were detected from 10 locations sampled during both years. Results indicate that Canada geese are frequently exposed to AIVs and, with resident populations, may potentially be useful as sentinels to confirm regional AIV transmission within wild bird populations.

Widespread detection of antibodies to Leptospira in feral swine in the United States.

As feral swine continue to expand their geographical range and distribution across the United States, their involvement in crop damage, livestock predation, and pathogen transmission is likely to increase. Despite the relatively recent discovery of feral swine involvement in the aetiology of a variety of pathogens, their propensity to transmit and carry a wide variety of pathogens is disconcerting. We examined sera from 2055 feral swine for antibody presence to six serovars of Leptospira that can also infect humans, livestock or domestic animals. About 13% of all samples tested positive for at least one serovar, suggesting that Leptospira infection is common in feral swine. Further studies to identify the proportion of actively infected animals are needed to more fully understand the risk they pose.

First reports of pseudorabies and winter ticks (Dermacentor albipictus) associated with an emerging feral swine (Sus scrofa) population in New Hampshire.

Abstract The expansion of feral swine (Sus scrofa) populations into new geographic regions is of concern not only due to increased range but also because they carry diseases and parasites that pose a threat to humans, livestock, and wildlife into new areas. Recently, emerging feral swine populations have been reported in the northeastern US and due to their adaptive nature will likely continue to spread. During 2009–2012, 49 feral swine were removed from three counties in New Hampshire. Of these, serum samples were submitted from 34 for disease surveillance testing. One of the feral swine was antibody-positive for pseudorabies virus (PRV) making it the first documented infection in feral swine in New Hampshire. Infestations of winter tick (Dermacentor albipictus) were also documented on two of the feral swine which had only been reported previously on feral swine in Texas. Feral swine may not only serve as an important host for an economically important commercial swine pathogen like PRV, but they could also increase host diversity for parasites such as the winter tick, a species that can regionally impact moose (Alces alces) survival. These findings warrant further investigation of expanding and established feral swine populations in New Hampshire as pathogen hosts and support continued effort to reduce numbers or regionally eradicate feral swine.

Avian Paramyxovirus Serotype 1 (Newcastle Disease Virus), Avian Influenza Virus, and Salmonella spp. in Mute Swans (Cygnus olor) in the Great Lakes Region and Atlantic Coast of the United States

SUMMARY Since their introduction to the United States in the late 19th century, mute swans (Cygnus olor) have become a nuisance species by causing damage to aquatic habitats, acting aggressively toward humans, competing with native waterfowl, and potentially transmitting or serving as a reservoir of infectious diseases to humans and poultry. In an effort to investigate their potential role as a disease reservoir and to establish avian health baselines for pathogens that threaten agricultural species or human health, we collected samples from 858 mute swans and tested them for avian paramyxovirus serotype 1 (APMV-1), avian influenza virus (AIV), and Salmonella spp. when possible. Our results indicate that exposure to APMV-1 and AIV is common (60%, n  =  771, and 45%, n  =  344, antibody prevalence, respectively) in mute swans, but detection of active viral shedding is less common (8.7%, n  =  414, and 0.8%, n  =  390, respectively). Salmonella was isolated from three mute swans (0.6%, n  =  459), and although the serovars identified have been implicated in previous human outbreaks, it does not appear that Salmonella is commonly carried by mute swans. RESUMEN Paramixovirus aviar serotipo 1 (virus de la enfermedad de Newcastle), virus de influenza aviar y Salmonella spp. en cisnes comunes (Cygnus olor) de la Región de los Grandes Lagos y en la costa atlántica de los Estados Unidos. Desde su introducción a los Estados Unidos a finales del siglo 19, los cisnes comunes (Cygnus olor) se han convertido en una especie problemática, porque causa daños a los hábitats acuáticos, actuando agresivamente hacia los seres humanos, compite con las aves acuáticas nativas, y potencialmente puede transmitir o servir como reservorio de enfermedades infecciosas para los seres humanos y para las aves comerciales. En un esfuerzo por investigar su posible papel como reservorios de la enfermedad y para establecer líneas base de salud aviar para los patógenos que amenazan a las especies agrícolas o a la salud humana, se recolectaron muestras de 858 cisnes comunes y se analizaron para detectar paramixovirus aviar serotipo 1 (APMV- 1), virus de la influenza aviar (AIV) y Salmonella spp. cuando fue posible. Los resultados indican que la exposición a APMV -1 y al virus de influenza aviar es común en cisnes comunes (60%, n  =  771, y 45%, n  =  344, para la prevalencia de anticuerpos, respectivamente), pero la detección de la replicación viral activa es menos común (8.7%, n  =  414, y 0.8%, n  =  390, respectivamente). Se aisló Salmonella de tres cisnes comunes (0.6%, n  =  459), y aunque los serovares identificados han sido implicados en brotes humanos anteriores, no parece que la Salmonella sea acarreada comúnmente por los cisnes comunes.