Monitoring of wild birds for Newcastle disease virus in north Queensland, Australia

A novel array of real-time RT-PCR assays for the rapid pathotyping of type I avian paramyxovirus (APMV-1)

Newcastle disease (ND) caused by virulent avian paramyxovirus type I (APMV-1) is a WOAH and EU listed disease affecting poultry worldwide. ND exhibits different clinical manifestations that may either be neurological, respiratory and/or gastrointestinal, accompanied by high mortality. In contrast, mild or subclinical forms are generally caused by lentogenic APMV-1 and are not subject to notification. The rapid discrimination of virulent and avirulent viruses is paramount to limit the spread of virulent APMV-1. The appropriateness of molecular methods for APMV-1 pathotyping is often hampered by the high genetic variability of these viruses that affects sensitivity and inclusivity. This work presents a new array of real-time RT-PCR (RT-qPCR) assays that enable the identification of virulent and avirulent viruses in dual mode, i.e., through pathotype-specific probes and subsequent Sanger sequencing of the amplification product. Validation was performed according to the WOAH recommendations. Performance indicators on sensitivity, specificity, repeatability and reproducibility yielded favourable results. Reproducibility highlighted the need for assays optimization whenever major changes are made to the procedure. Overall, the new RT-qPCRs showed its ability to detect and pathotype all tested APMV-1 genotypes and its suitability for routine use in clinical samples.

Epidemiological surveillance of Newcastle disease virus in Egypt - a 6-year cohort study

Newcastle disease (ND) is one of the most important poultry diseases worldwide and can lead to annual losses of up to 80% of backyard chickens in Africa. A retrospective cohort of 6 years was planned to screen the NDV in intensive chicken and turkey flocks. The existence of velogenic NDV strain was screened in different poultry flocks showing suspected signs of NDV using real-time RT-PCR targeting the F gene of the velogenic strain. A total of 843 poultry flocks were screened during the cohort. Samples were classified based on the month and year as well as the poultry type. All flocks should be negative for avian influenza virus as an inclusion criterion of the study. The F gene of a randomly selected positive sample from each year as well as an archival sample from 2005 was sequenced. An overall of 52.4% (443/842) of the tested farms showed positive results for the velogenic NDV. The cumulative percentage of positive flocks to the total positive flocks per month ranged from 5.9 to 11.8%. The results revealed that NDV is circulating across all months annually without evidence of seasonal tendency of the disease. Most of the strains belong to genotype VII.1.1, with only two strains related to XXI.1.1 and XXI.2. All VII.1.1 strains possess arginine at 27 position while XXI.1.1 and XXI.2 strains showed cysteine at 27 and amino acid substitutions in the signal peptide, cleavage site, and neutralizing epitopes. In conclusion, the current molecular epidemiological surveillance confirms the enzootic nature of NDV. It circulates all year round with no evidence of seasonal incidence. Genotype VII is the most predominant NDV genotype in Egypt.

Plasmodium matutinum Causing Avian Malaria in Lovebirds (Agapornis roseicollis) Hosted in an Italian Zoo

Avian malaria is a worldwide distributed, vector-born disease of birds caused by parasites of the order Haemosporida. There is a lack of knowledge about the presence and pathogenetic role of Haemosporida in Psittacidae. Here we report a case of avian malaria infection in lovebirds (Agapornis roseicollis), with the genetic characterization of the Plasmodium species involved. The birds were hosted in a zoo located in Italy, where avian malaria cases in African penguins (Spheniscus demersus) were already reported. Animals (n = 11) were submitted for necropsy after sudden death and were subjected to further analyses including histopathology, bacteriology, and PCR for the research of haemosporidians. Clinical history, gross lesions and histopathological observation of schizonts, together with positive PCR results for Plasmodium spp., demonstrated that avian malaria was the cause of death for one animal and the possible cause of death for the other nine. The sequences obtained were compared using BLAST and analyzed for similarity to sequences available at the MalAvi database. Genetic analyses demonstrated a 100% nucleotide identity to Plasmodium matutinum LINN1 for all the obtained sequences. To our knowledge, this is the first report describing avian malaria in lovebirds.

Development of a Dissemination Platform for Spatiotemporal and Phylogenetic Analysis of Avian Infectious Bronchitis Virus

Infecting large portions of the global poultry populations, the avian infectious bronchitis virus (IBV) remains a major economic burden in North America. With more than 30 serotypes globally distributed, Arkansas, Connecticut, Delaware, Georgia, and Massachusetts are among the most predominant serotypes in the United States. Even though vaccination is widely used, the high mutation rate exhibited by IBV is continuously triggering the emergence of new viral strains and hindering control and prevention measures. For that reason, targeted strategies based on constantly updated information on the IBV circulation are necessary. Here, we sampled IBV-infected farms from one US state and collected and analyzed 65 genetic sequences coming from three different lineages along with the immunization information of each sampled farm. Phylodynamic analyses showed that IBV dispersal velocity was 12.3 km/year. The majority of IBV infections appeared to have derived from the introduction of the Arkansas DPI serotype, and the Arkansas DPI and Georgia 13 were the predominant serotypes. When analyzed against IBV sequences collected across the United States and deposited in the GenBank database, the most likely viral origin of our sequences was from the states of Alabama, Georgia, and Delaware. Information about vaccination showed that the MILDVAC-MASS+ARK vaccine was applied on 26% of the farms. Using a publicly accessible open-source tool for real-time interactive tracking of pathogen spread and evolution, we analyzed the spatiotemporal spread of IBV and developed an online reporting dashboard. Overall, our work demonstrates how the combination of genetic and spatial information could be used to track the spread and evolution of poultry diseases, providing timely information to the industry. Our results could allow producers and veterinarians to monitor in near-real time the current IBV strain circulating, making it more informative, for example, in vaccination-related decisions.

Comparison between class I NDV and class II NDV in aerosol transmission under experimental condition

Recent epidemiological surveys have shown that class I Newcastle disease virus (NDV) is widely distributed in China. However, little is currently known about its transmission. Therefore, in this study, we compared the transmission of class I and class II NDV. Specific-pathogen-free chickens were divided into a class I NDV inoculation group and an aerosol-exposed infection group and kept in 2 separate isolators (A and B, respectively) that were connected with an airtight plastic pipe. After inoculation, air samples were collected regularly with an All-Glass Impinger-30 (Liaoyang, China), and the airborne virus contents were analyzed using the plaque count method. In addition, oral and cloacal swabs were collected regularly to detect virus shedding using quantitative reverse transcription PCR. Similar trials were conducted simultaneously with class II NDV in isolators C and D. We consistently detected class I NDV aerosols in both isolators A and B up to 40 D post-inoculation (dpi). The aerosol concentration reached a maximum of 13.81 × 103 plague-forming units per cubic meter of air at 18 dpi and was significantly higher than that of class II NDV at 21 and 24 dpi. We also detected class I virus shedding from 2 to 40 dpi in the inoculated chickens and from 7 to 40 D post-aerosol-exposed infection in the aerosol-exposed chickens. This phenomenon may explain why class I NDV has been the primary epidemic strain of NDV in recent years.

Virome heterogeneity and connectivity in waterfowl and shorebird communities

Models of host-microbe dynamics typically assume a single-host population infected by a single pathogen. In reality, many hosts form multi-species aggregations and may be infected with an assemblage of pathogens. We used a meta-transcriptomic approach to characterize the viromes of nine avian species in the Anseriformes (ducks) and Charadriiformes (shorebirds). This revealed the presence of 27 viral species, of which 24 were novel, including double-stranded RNA viruses (Picobirnaviridae and Reoviridae), single-stranded RNA viruses (Astroviridae, Caliciviridae, Picornaviridae), a retro-transcribing DNA virus (Hepadnaviridae), and a single-stranded DNA virus (Parvoviridae). These viruses comprise multi-host generalist viruses and those that are host-specific, indicative of both virome connectivity (host sharing) and heterogeneity (host specificity). Virome connectivity was apparent in two well described multi-host virus species -avian coronavirus and influenza A virus- and a novel Rotavirus species that were shared among some Anseriform species, while virome heterogeneity was reflected in the absence of viruses shared between Anseriformes and Charadriiformes, as well as differences in viral abundance and alpha diversity among species. Overall, we demonstrate complex virome structures across host species that co-exist in multi-species aggregations.

Genotype Diversity of Newcastle Disease Virus in Nigeria: Disease Control Challenges and Future Outlook

Newcastle disease (ND) is one of the most important avian diseases with considerable threat to the productivity of poultry all over the world. The disease is associated with severe respiratory, gastrointestinal, and neurological lesions in chicken leading to high mortality and several other production related losses. The aetiology of the disease is an avian paramyxovirus type-1 or Newcastle disease virus (NDV), whose isolates are serologically grouped into a single serotype but genetically classified into a total of 19 genotypes, owing to the continuous emergence and evolution of the virus. In Nigeria, molecular characterization of NDV is generally very scanty and majorly focuses on the amplification of the partial F gene for genotype assignment. However, with the introduction of the most objective NDV genotyping criteria which utilize complete fusion protein coding sequences in phylogenetic taxonomy, the enormous genetic diversity of the virus in Nigeria became very conspicuous. In this review, we examine the current ecological distribution of various NDV genotypes in Nigeria based on the available complete fusion protein nucleotide sequences (1662 bp) in the NCBI database. We then discuss the challenges of ND control as a result of the wide genetic distance between the currently circulating NDV isolates and the commonest vaccines used to combat the disease in the country. Finally, we suggest future directions in the war against the economically devastating ND in Nigeria.

Virus-virus interactions and host ecology are associated with RNA virome structure in wild birds

Little is known about the factors that shape the ecology of RNA viruses in nature. Wild birds are an important case in point, as other than influenza A virus, avian samples are rarely tested for viruses, especially in the absence of overt disease. Using bulk RNA-sequencing ("meta-transcriptomics"), we revealed the viral diversity present in Australian wild birds through the lens of the ecological factors that may determine virome structure and abundance. A meta-transcriptomic analysis of four Anseriformes (waterfowl) and Charadriiformes (shorebird) species sampled in temperate and arid Australia revealed the presence of 27 RNA virus genomes, 18 of which represent newly described species. The viruses identified included a previously described gammacoronavirus and influenza A viruses. Additionally, we identified novel virus species from the families Astroviridae, Caliciviridae, Reoviridae, Rhabdoviridae, Picobirnaviridae and Picornaviridae. We noted differences in virome structure that reflected underlying differences in location and influenza A infection status. Red-necked Avocets (Recurvirostra novaehollandiae) from Australia's arid interior possessed the greatest viral diversity and abundance, markedly higher than individuals sampled in temperate Australia. In Ruddy Turnstones (Arenaria interpres) and dabbling ducks (Anas spp.), viral abundance and diversity were higher and more similar in hosts that were positive for influenza A infection compared to those that were negative for this virus, despite samples being collected on the same day and from the same location. This study highlights the extent and diversity of RNA viruses in wild birds and lays the foundation for understanding the factors that determine virome structure in wild populations.

Pathobiology of Avian avulavirus 1: special focus on waterfowl

Avian avulaviruses serotype 1 (abbreviated as APMV-1 for the historical name avian paramyxovirus 1) are capable of infecting a wide spectrum of avian species with variable clinical symptoms and outcomes. Ease of transmission has allowed the virus to spread worldwide with varying degrees of virulence depending upon the virus strain and host species. The emergence of new virulent genotypes from global epizootics, and the year-to-year genomic changes in low and high virulence APMV-1 imply that distinct genotypes of APMV-1 are simultaneously evolving at different geographic locations across the globe. This vast genomic diversity may be favoured by large variety of avian species susceptibility to APMV-1 infection, and by the availability of highly mobile wild birds. It has long been considered that waterfowls are not sensitive to APMV-1 and are unable to show any clinical signs, however, outbreaks from the 90's contradict these concepts. The APMV-1 isolates are increasingly reported from the waterfowl. Waterfowl have strong innate immune responses, which minimize the impact of virus infection, however, are unable to prevent the viral shedding. Numerous APMV-1 are carried by domestic waterfowl intermingling with terrestrial poultry. Therefore, commercial ducks and geese should be vaccinated against APMV-1 to minimize the virus shedding and for the prevention the transmission. Genetic diversity within APMV-1 demonstrates the need for continual monitoring of viral evolution and periodic updates of vaccine seed-strains to achieve efficient control and eradication of APMV-1 in waterfowls.

Genotypic characterisation of Avian paramyxovirus type-1 viruses isolated from aquatic birds in Uganda

Avian paramyxovirus type-1 (APMV-1) viruses of the lentogenic pathotypes are often isolated from wild aquatic birds and may mutate to high pathogenicity when they cross into poultry and cause debilitating Newcastle disease. This study characterised AMPV-1 isolated from fresh faecal droppings from wild aquatic birds roosting sites in Uganda. Fresh faecal samples from wild aquatic birds at several waterbodies in Uganda were collected and inoculated into 9–10-day-old embryonated chicken eggs. After isolation, the viruses were confirmed as APMV-1 by APMV-1-specific polymerase chain reaction (PCR). The cleavage site of the fusion protein gene for 24 representative isolates was sequenced and phylogenetically analysed and compared with representative isolates of the different APMV-1 genotypes in the GenBank database. In total, 711 samples were collected from different regions in the country from which 72 isolates were recovered, giving a prevalence of 10.1%. Sequence analysis of 24 isolates revealed that the isolates were all lentogenic, with the typical ¹¹¹GGRQGR’L¹¹⁷ avirulent motif. Twenty-two isolates had similar amino acid sequences at the cleavage site, which were different from the LaSota vaccine strain by a silent nucleotide substitution T357C. Two isolates, NDV/waterfowl/Uganda/MU150/2011 and NDV/waterfowl/Uganda/MU186/2011, were different from the rest of the isolates in a single amino acid, with aspartate and alanine at positions 124 and 129, respectively. The results of this study revealed that Ugandan aquatic birds indeed harbour APMV-1 that clustered with class II genotype II strains and had limited genetic diversity.

Avian viral surveillance in Victoria, Australia, and detection of two novel avian herpesviruses

Viruses in avian hosts can pose threats to avian health and some have zoonotic potential. Hospitals that provide veterinary care for avian patients may serve as a site of exposure of other birds and human staff in the facility to these viruses. They can also provide a useful location to collect samples from avian patients in order to examine the viruses present in wild birds. This study aimed to investigate viruses of biosecurity and/or zoonotic significance in Australian birds by screening samples collected from 409 birds presented to the Australian Wildlife Health Centre at Zoos Victoria’s Healesville Sanctuary for veterinary care between December 2014 and December 2015. Samples were tested for avian influenza viruses, herpesviruses, paramyxoviruses and coronaviruses, using genus- or family-wide polymerase chain reaction methods coupled with sequencing and phylogenetic analyses for detection and identification of both known and novel viruses. A very low prevalence of viruses was detected. Columbid alphaherpesvirus 1 was detected from a powerful owl (Ninox strenua) with inclusion body hepatitis, and an avian paramyxovirus most similar to Avian avulavirus 5 was detected from a musk lorikeet (Glossopsitta concinna). Two distinct novel avian alphaherpesviruses were detected in samples from a sulphur-crested cockatoo (Cacatua galerita) and a tawny frogmouth (Podargus strigoides). Avian influenza viruses and avian coronaviruses were not detected. The clinical significance of the newly detected viruses remains undetermined. Further studies are needed to assess the host specificity, epidemiology, pathogenicity and host-pathogen relationships of these novel viruses. Further genome characterization is also indicated, and would be required before these viruses can be formally classified taxonomically. The detection of these viruses contributes to our knowledge on avian virodiversity. The low level of avian virus detection, and the absence of any viruses with zoonotic potential, suggests low risk to biosecurity and human health.

An Australian Newcastle Disease Virus With a Virulent Fusion Protein Cleavage Site Produces Minimal Pathogenicity in Chickens

Newcastle disease is an important disease of poultry caused by virulent strains of Newcastle disease virus (NDV). During the 1998 to 2002 outbreaks of Newcastle disease in Australia, it was observed that the mild clinical signs seen in some chickens infected with NDV did not correlate with the viruses' virulent fusion protein cleavage site motifs or standard pathogenicity indices. The pathogenicity of 2 Australian NDV isolates was evaluated in experimentally challenged chickens based on clinical evaluation, histopathology, immunohistochemistry, and molecular techniques. One of these virus isolates, Meredith/02, was shown to induce only very mild clinical signs with no mortalities in an experimental setting, in contrast to the velogenic Herts 33/56 and Texas GB isolates. This minimal pathogenicity was associated with decreased virus replication and antigen distribution in tissues. This demonstrates that the Australian Meredith/02 NDV, despite possessing a virulent fusion protein cleavage site, did not display a velogenic phenotype.

Of Ducks and Men: Ecology and Evolution of a Zoonotic Pathogen in a Wild Reservoir Host

A hallmark of disease is that most pathogens are able to infect more than one host species. However, for most pathogens, we still have a limited understanding of how this affects epidemiology, persistence and virulence of infections—including several zoonotic pathogens that reside in wild animal reservoirs and spillover into humans. In this chapter, we review the current knowledge of mallard (Anas platyrhynchos) as host for pathogens. This species is widely distributed, often occupying habitats close to humans and livestock, and is an important game bird species and the ancestor to domestic ducks—thereby being an excellent model species to highlight aspects of the wildlife, domestic animal interface and the relevance for human health. We discuss mallard as host for a range of pathogens but focus more in depth of it as a reservoir host for influenza A virus (IAV). Over the last decades, IAV research has surged, prompted in part to the genesis and spread of highly pathogenic virus variants that have been devastating to domestic poultry and caused a number of human spillover infections. The aim of this chapter is to synthesise and review the intricate interactions of virus, host and environmental factors governing IAV epidemiology and evolution.

Experimental infection with Brazilian Newcastle disease virus strain in pigeons and chickens

This study was designed with the goal of adding as much information as possible about the role of pigeons (Columba livia) and chickens (Gallus gallus) in Newcastle disease virus epidemiology. These species were submitted to direct experimental infection with Newcastle disease virus to evaluate interspecies transmission and virus-host relationships. The results obtained in four experimental models were analyzed by hemagglutination inhibition and reverse transcriptase polymerase chain reaction for detection of virus shedding. These techniques revealed that both avian species, when previously immunized with a low pathogenic Newcastle disease virus strain (LaSota), developed high antibody titers that significantly reduced virus shedding after infection with a highly pathogenic Newcastle disease virus strain (São Joao do Meriti) and that, in chickens, prevent clinical signs. Infected pigeons shed the pathogenic strain, which was not detected in sentinel chickens or control birds. When the presence of Newcastle disease virus was analyzed in tissue samples by RT-PCR, in both species, the virus was most frequently found in the spleen. The vaccination regimen can prevent clinical disease in chickens and reduce viral shedding by chickens or pigeons. Biosecurity measures associated with vaccination programs are crucial to maintain a virulent Newcastle disease virus-free status in industrial poultry in Brazil.

Interacting Effects of Newcastle Disease Transmission and Illegal Trade on a Wild Population of White-Winged Parakeets in Peru: A Modeling Approach

Illegal wildlife-pet trade can threaten wildlife populations directly from overharvest, but also indirectly as a pathway for introduction of infectious diseases. This study evaluated consequences of a hypothetical introduction of Newcastle disease (ND) into a wild population of Peru's most trafficked psittacine, the white-winged parakeet (Brotogeris versicolurus), through release of infected confiscated individuals. We developed two mathematical models that describe ND transmission and the influence of illegal harvest in a homogeneous (model 1) and age-structured population of parakeets (model 2). Infection transmission dynamics and harvest were consistent for all individuals in model 1, which rendered it mathematically more tractable compared to the more complex, age-structured model 2 that separated the host population into juveniles and adults. We evaluated the interaction of ND transmission and harvest through changes in the basic reproduction number (R0) and short-term host population dynamics. Our findings demonstrated that ND introduction would likely provoke considerable disease-related mortality, up to 24% population decline in two years, but high harvest rates would dampen the magnitude of the outbreak. Model 2 produced moderate differences in disease dynamics compared to model 1 (R0 = 3.63 and 2.66, respectively), but highlighted the importance of adult disease dynamics in diminishing the epidemic potential. Therefore, we suggest that future studies should use a more realistic, age-structured model. Finally, for the presumptive risk that illegal trade of white-winged parakeets could introduce ND into wild populations, our results suggest that while high harvest rates may have a protective effect on the population by reducing virus transmission, the combined effects of high harvest and disease-induced mortality may threaten population survival. These results capture the complexity and consequences of the interaction between ND transmission and harvest in a wild parrot population and highlight the importance of preventing illegal trade.

Pathotypic and Sequence Characterization of Newcastle Disease Viruses from Vaccinated Chickens Reveals Circulation of Genotype II, IV and XIII and in India

Newcastle disease virus (NDV) causes a highly contagious disease which continuously haunts the global poultry industry. The nature and molecular epidemiology of NDVs prevalent in recent outbreaks in India is poorly understood. This study aimed to characterize NDVs prevalent in vaccinated flocks in India using whole-genome sequencing and biological pathotyping. Twelve field isolates were collected from outbreaks which occurred in different parts of India and characterized as velogenic based on their intracerebral pathogenicity index (ICPI) and amino acid sequence at the F protein cleavage site. All 12 of the field isolates and five commonly used vaccine strains were selected for whole-genome sequencing using Ion Torrent PGM technology, yielding complete genome sequences for ten field isolates and all vaccine strains. The genome of all isolates was found to be 15 192 nt long with a high level of conservation across multiple genomic features with APMV-I viruses. Phylogenetic analysis and evolutionary distance calculations placed the isolates in genotypes II, IV and XIII. Revisiting other recently reported strains provided preliminary evidence of genotypes VI, VII and XVIII circulating in India. Comparison between the field and vaccine virus sequences revealed unique genomic and amino acid differences in important antigenic regions of the F and hemagglutinin-neuraminidase (HN) genes which can be targeted for site directed mutagenesis to evaluate the impact of these substitutions on virus pathogenicity. This study highlights the requirement to evaluate current vaccines through systematic protection assays to determine protection efficacy against field isolates.

Empirical analysis suggests continuous and homogeneous circulation of Newcastle disease virus in a wide range of wild bird species in Africa

Newcastle disease (ND) is one of the most important poultry diseases worldwide and can lead to annual losses of up to 80% of backyard chickens in Africa. All bird species are considered susceptible to ND virus (NDV) infection but little is known about the role that wild birds play in the epidemiology of the virus. We present a long-term monitoring of 9000 wild birds in four African countries. Overall, 3·06% of the birds were PCR-positive for NDV infection, with prevalence ranging from 0% to 10% depending on the season, the site and the species considered. Our study shows that ND is circulating continuously and homogeneously in a large range of wild bird species. Several genotypes of NDV circulate concurrently in different species and are phylogenetically closely related to strains circulating in local domestic poultry, suggesting that wild birds may play several roles in the epidemiology of different NDV strains in Africa. We recommend that any strategic plan aiming at controlling ND in Africa should take into account the potential role of the local wild bird community in the transmission of the disease.

Prevalence of avian paramyxovirus type 1 in Mallards during autumn migration in the western Baltic Sea region

Background

Newcastle disease virus (NDV) is the causative agent of the Newcastle disease, a severe disease in birds associated with substantial economic losses to the poultry industry worldwide. Sweden is situated along the Western European waterfowl flyway and applies a non-vaccination policy combined with directives of immediate euthanisation of NDV infected flocks. During the last decades there have been several outbreaks with NDV in poultry in Sweden. However, less is known about the virus prevalence in the wild bird population including waterfowl, a well-established reservoir of avian paramyxovirus type 1 (APMV-1), the paramyxovirus serotype that include pathogenic NDV.

Methods

The survey constituted of 2332 samples from Mallards (Anas platyrhynchos), trapped in the southern part of Sweden during autumn migration in 2010. These samples were screened for APMV-1 by real-time reverse transcription PCR, and viral strains from positive samples were isolated and characterized by sequence analysis of the fusion gene and by phylogenetic analysis.

Conclusions

Twenty of these samples were positive for APMV-1, hence a virus prevalence of 0.9% (95% Confidence Interval [95% CI]=0.54%, 1.35%). The highest APMV-1 prevalence was detected in juvenile Mallards sampled in November (n=887, prevalence 1.24% ([95% CI])=0.67%, 2.24%). Sequence analysis and evaluation of phylogenetic relatedness indicated that isolated APMV-1 strains were lentogenic, and phylogenetically most closely related to genotype Ib strains within the clade of class II viruses. The sampling system employed enabled us to follow APMV-1 infections and the shedding of one particular viral strain in one individual bird over several days. Furthermore, combining previous screening results with the APMV-1 detections in this study showed that more than 50% of Mallards that tested positive for APMV-1 RNA were co-infected with influenza A virus.

Use of reverse transcriptase polymerase chain reaction (RT-PCR) in molecular screening of Newcastle disease virus in poultry and free-living bird populations

The aim of this study was to evaluate a simple molecular method of reverse transcriptase polymerase chain reaction (RT-PCR) to differentiate Newcastle disease virus strains according to their pathogenicity, in order to use it in molecular screening of Newcastle disease virus in poultry and free-living bird populations. Specific primers were developed to differentiate LaSota--LS--(vaccine strain) and Sao Joao do Meriti--SJM--strain (highly pathogenic strain). Chickens and pigeons were experimentally vaccinated/infected for an in vivo study to determine virus shedding in feces. Validation of sensitivity and specificity of the primers (SJM and LS) by experimental models used in the present study and results obtained in the molecular analysis of the primers by BLAST made it possible to generalize results. The development of primers that differentiate the level of pathogenicity of NDV stains is very important, mainly in countries where real-time RT-PCR is still not used as a routine test. These primers were able to determine the presence of the agent and to differentiate it according to its pathogenicity.

Causes of morbidity and mortality of wild aquatic birds at Billabong Sanctuary, Townsville, North Queensland, Australia

Infectious diseases are common causes of significant morbidity and mortality events of wild aquatic birds (WABs) worldwide. Reports of Australian events are infrequent. A 3-yr passive surveillance program investigating the common causes of morbidity and mortality of WABs was conducted at Billabong Sanctuary near Townsville, North Queensland, from April 2007 to March 2010. Forty-two carcasses were obtained and evaluated by clinico-pathologic, histologic, bacteriologic, and virologic (molecular) examinations. Morbidity and mortality were sporadic and more commonly observed in chicks and juvenile birds in April than other months of the year. Morbid birds were frequently unable to walk. Hemorrhagic lesions and infiltration of lymphocytes in various organs were the most common findings in dead birds. Identified bacterial diseases that could cause bird mortality were colibacillosis, pasteurellosis, and salmonellosis. Salmonella serotypes Virchow and Hvittingfoss were isolated from an Australian white ibis (Threskiornis molucca) chick and two juvenile plumed whistling ducks (Dendrocygna eytoni) in April 2007. These strains have been previously isolated from humans in North Queensland. A multiplex real time reverse transcriptase-PCR (rRT-PCR) detected Newcastle disease viral RNA (class 2 type) in one adult Australian pelican (Pelecanus conspicillatus) and a juvenile plumed whistling duck. No avian influenza viral RNA was detected from any sampled birds by the rRT-PCR for avian influenza. This study identified the public health importance of Salmonella in WABs but did not detect the introduction of the high pathogenicity avian influenza H5N1 virus in the population. A successful network was established between the property owner and the James Cook University research team through which dead birds, with accompanying information, were readily obtained for analysis. There is an opportunity for establishing a long-term passive disease surveillance program for WABs in North Queensland, an important region in Australian biosecurity, thus potentially significantly benefitting public health in the region and the country.