Exotic Newcastle disease

Exotic Newcastle disease (END) is a virulent strain of avian paramyxovirus-1. This virus has devastated the poultry industry in many countries. As a result, strict international regulations are in place to control the movement of exotic birds, poultry, and poultry products to prevent the introduction of this disease into countries where it has been eradicated. When END is introduced to a naı̈ve, unvaccinated population of poultry, mortality may reach 100%. Signs in chickens will depend on the strain of END involved. However, this disease should be suspected in any outbreak of disease in poultry where there is high mortality and respiratory, gastrointestinal and/or central nervous system signs are observed. In the most recent END outbreak in the United States, many birds had edematous heads, cyanosis, and diphtheritic lesions of the trachea, oral cavity, and esophagus. Signs in companion birds are variable and often nonspecific. Practitioners, however, should suspect this disease in parrots, particularly Amazon parrots, if the sick bird is of questionable origin and over the course of the disease develops signs related to the central nervous system. Efforts to keep END out of the United States have been largely successful; however, on repeated occasions in the last 30 years, END has entered the United States through the illegal transport of fighting chickens and psittacine birds. In two cases, END has made it into commercial poultry operations, resulting in the slaughter of millions of birds and a significant economic impact to poultry and exotic bird producers. Education about this disease, strict biosecurity measures, and continued vigilance will be necessary to prevent future outbreaks of END.     

Continuous disinfection as a means to control infectious diseases in poultry. Evaluation of a continuous disinfection programme for broilers

A full continuous disinfection programme, consisting of disinfection during cleanout of poultry houses prior to placement of chickens, disinfection of the drinking water and spray disinfection of the birds during production was evaluated in broilers under experimental condition as well as under field conditions. Under controlled conditions, the experimental design consisted of three groups, two of which were control groups. Each group comprised 300 chickens. In one of the control groups, no disinfection of the pens was undertaken prior to the placement of the chickens. In the other control group, disinfection of the pens prior to placement of the birds was carried out using a glutaraldehyde-based product. In the test group, disinfection prior to placement was done. The drinking water of these birds was treated continuously and the birds were sprayed with a non-toxic disinfectant during production. Production parameters, such as growth rate, feed conversion ratio and feed consumption, of the birds in the three groups were monitored. In addition, all mortalities in the different groups were recorded and classified into diseases of an infectious nature, non-infectious nature and unknown category. Bacterial counts were also done on a weekly basis from the different pens. In this experiment, it was shown that the full continuous disinfection programme resulted in a lower number of mortalities caused by infectious agents as well as a reduction in the bacterial counts in the pens treated with the full continual disinfection programme. The full continuous disinfection programme was also tested on a commercial poultry farm in the Northern Cape Province of South Africa. Two production houses of 3,500 birds were randomly selected as test houses for the full continuous disinfection programme. Another similar house, which received day-old chicks from the same batch as the other two houses, was selected as the control house; it received the routine disinfection procedure prior to placement of the chicks. During the course of this experiment, a severe outbreak of Newcastle disease was experienced on this farm. It was demonstrated that, in the face of this severe challenge, the full continuous disinfection programme controlled the spread of the disease in both the houses where it had been applied at a stage when in every other house (including the control house) on the farm birds were suffering very high mortalities.     

Pathogenicity of infectious bronchitis virus isolates from Ontario chickens

Infectious bronchitis (IB) is one of the important viral diseases of chickens, and in spite of regular vaccination, IB is a continuous problem in Canadian poultry operations. In an earlier study using sentinel chickens we determined the incidence of infectious bronchitis virus (IBV) in Ontario commercial layer flocks. The objective of this study was to determine the pathogenicity of 5 nonvaccine-related IBV isolates recovered from the sentinel birds. The clinical signs, gross, and histological lesions in specific pathogen-free chickens indicated that all 5 isolates caused mild lesions in the respiratory tract. An important finding of this study was the significantly lower average daily weight gain among virus-inoculated groups of chickens during the acute phase of infection. Based on sequences of part of the S1 gene IBV-ON2, IBV-ON3, and IBV-ON5 formed a cluster and they were closely related to strain CU-82792. IBV-ON4 had 98.7% identity with the strain PA/1220/9, a nephropathogenic variant.     

Epidemiological investigation, cleanup, and eradication of pullorum disease in adult chickens and ducks in two small-farm flocks

Pullorum disease causing acute septicemia and mortality in adult brown chickens was diagnosed in a small-farm chicken flock in Iowa. Also, Salmonella Pullorum was isolated from the intestine of one of four rats trapped on this index farm. Tracing movements of spent hens from the index farm resulted in identification of a second infected flock on a contact farm. Poultry on the contact farm were tested with the stained-antigen, rapid whole-blood test, and two ducks and one chicken gave positive reactions. Reactors were necropsied and cultures of appropriate tissues resulted in isolation of Salmonella Pullorum from one duck and the chicken. Pulsed-field gel electrophoresis banding patterns of Salmonella Pullorum isolates from chickens on the index and contact farms, the duck, and the rat demonstrated that all isolates were genetically very similar. Both flocks were quarantined and depopulated and a detailed flock cleanup plan was created for both farms. After extensive cleaning and disinfection procedures were completed on the index farm, environmental monitoring and bioassays of trapped mice were conducted. Negative cultures of environmental swabs and trapped mice and negative blood tests of all birds conducted 4 mo after placement of a new flock on the index farm demonstrated that cleaning and disinfection methods used in this outbreak had successfully eliminated Salmonella Pullorum organisms from this farm.     

Antibody response and virus shedding of chickens inoculated with left end deleted fowl adenovirus 9-based recombinant viruses

The nonpathogenic fowl adenoviruses (FAdVs) are suitable recombinant virus vectors. Two different replication-competent FAdV-9-based recombinant viruses carrying the enhanced green fluorescent protein (EGFP) gene within a nonessential DNA sequence at the left end genomic region were tested in chickens to study the antibody response by enzyme-linked immunosorbent assay to both the foreign proteins, EGFP and FAdV-9, and virus shedding through the feces. All inoculations were done intramuscularly: groups 1 and 2 with the recombinant viruses and group 3 with the wild-type FAdV-9 virus. Group 4 was mock inoculated. Sentinel birds also were included in groups 1-3 to study virus transmission. Boosting inoculations were done in all groups at 2, 3, and 4 wk after the first inoculation. Antibodies to EGFP were detected at 3-7 wk postinoculation in groups 1 and 2 only. Antibody response to FAdV-9 in groups 1-3 did not differ significantly (P > 0.06). Virus was not detected in the feces of chickens in groups 1 and 2, including the sentinel birds, but virus was present in the feces of chickens in group 3, including the sentinel birds. These results further supported our previous findings regarding the suitability of the nonessential region at the left end of the viral genome as an insertion site for foreign genes and its importance in in vivo replication. In this work, we demonstrated the potential of FAdV-9-based recombinant viruses as vaccines for poultry.     

Survival of exotic Newcastle disease virus in commercial poultry environment following removal of infected chickens

During the first weeks of 2003, after exotic Newcastle disease (END) was confirmed in commercial layer flocks in Southern California, it became apparent that the virus survival information in the literature varied widely and was difficult to extrapolate to current local conditions. The END Task Force used the information available in the literature and the recommendations of research scientists to establish protocols for safely handling manure from infected and depopulated premises. In an attempt to gain more applicable knowledge in the management of contaminated poultry manure in the course of the END outbreak, this virus survival study was designed and implemented. Environmental drag swabs were tested for END virus from two of the early-infected commercial ranches that consisted of several houses following immediate removal of the infected flocks. A total of 293 samples, composed of 168 manure drag swab pools, 72 dropping board swab pools, and 38 compost swab pools from 3 houses (ranch 1), and 180 manure belt scraper swab pools from ranch 2 were analyzed for ND virus isolation and characterization for 21 consecutive days postdepopulation. Thirteen manure drag swab pools (from houses 1 and 3) and two manure dropping board swab pools (from house 3) collected from ranch 1 were positive for END virus at 0, 1, 2, 3, 4, 7, 10, 12, and 16 days postdepopulation. No END virus was isolated after the 16th day following depopulation from any of the samples. All samples from ranch 2 were negative during the entire observation period.     

Survey of small-enterprise chicken operations in the United States

The National Animal Health Monitoring System (NAHMS) Small-Enterprise Chicken study was conducted to better understand bird movement and biosecurity practices of commercial poultry operations having fewer than 20,000 chickens. A stratified random sample of 2511 operations having 1000–19,999 chickens was selected from a list maintained by the National Agricultural Statistics Service (NASS), based primarily upon data from the 2002 Census of Agriculture; 1789 (72.1%) operations participated in the study. Over one-half of operations were contract operations with breeding birds, and one-fourth were contract operations without breeding birds. Only 17% of operations were independent (noncontract) operations. Independent operations were primarily table-egg producers and to a lesser extent, growers. Independent operations were more likely to have birds other than chickens, to allow outdoor access to birds, and had less stringent biosecurity requirements compared to contract operations.     

Infectivity and transmissibility of H9N2 avian influenza virus in chickens and wild terrestrial birds

Genetic changes in avian influenza viruses influence their infectivity, virulence and transmission. Recently we identified a novel genotype of H9N2 viruses in widespread circulation in poultry in Pakistan that contained polymerases (PB2, PB1 and PA) and non-structural (NS) gene segments identical to highly pathogenic H7N3 viruses. Here, we investigated the potential of these viruses to cause disease and assessed the transmission capability of the virus within and between poultry and wild terrestrial avian species. Groups of broilers, layers, jungle fowl, quail, sparrows or crows were infected with a representative strain (A/chicken/UDL-01/08) of this H9N2 virus and then mixed with naïve birds of the same breed or species, or different species to examine transmission. With the exception of crows, all directly inoculated and contact birds showed clinical signs, varying in severity with quail showing the most pronounced clinical signs. Virus shedding was detected in all infected birds, with quail showing the greatest levels of virus secretion, but only very low levels of virus were found in directly infected crow samples. Efficient virus intra-species transmission was observed within each group with the exception of crows in which no evidence of transmission was seen. Interspecies transmission was examined between chickens and sparrows and vice versa and efficient transmission was seen in either direction. These results highlight the ease of spread of this group of H9N2 viruses between domesticated poultry and sparrows and show that sparrows need to be considered as a high risk species for transmitting H9N2 viruses between premises.     

Evaluation of risk factors for the spread of low pathogenicity H7N2 avian influenza virus among commercial poultry farms

OBJECTIVE: To identify risk factors associated with the spread of low pathogenicity H7N2 avian influenza (AI) virus among commercial poultry farms in western Virginia during an outbreak in 2002. DESIGN: Case-control study. PROCEDURE: Questionnaires were used to collect information about farm characteristics, biosecurity measures, and husbandry practices on 151 infected premises (128 turkey and 23 chicken farms) and 199 noninfected premises (167 turkey and 32 chicken farms). RESULTS: The most significant risk factor for AI infection was disposal of dead birds by rendering (odds ratio [OR], 73). In addition, age > or = 10 weeks (OR for birds aged 10 to 19 weeks, 4.9; OR for birds aged > or = 20 weeks, 4.3) was a significant risk factor regardless of poultry species involved. Other significant risk factors included use of nonfamily caretakers and the presence of mammalian wildlife on the farm. Factors that were not significantly associated with infection included use of various routine biosecurity measures, food and litter sources, types of domestic animals on the premises, and presence of wild birds on the premises. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that an important factor contributing to rapid early spread of AI virus infection among commercial poultry farms during this outbreak was disposal of dead birds via rendering off-farm. Because of the highly infectious nature of AI virus and the devastating economic impact of outbreaks, poultry farmers should consider carcass disposal techniques that do not require off-farm movement, such as burial, composting, or incineration.     

Serological survey of the infectious disease status of Old English Game fowl in the lower North Island, New Zealand

AIM: To investigate the serological status of Old English Game (OEG) cockerels for a range of infectious diseases of poultry. METHODS: Standard methods were used to screen serum collected from approximately 200 birds during routine dubbing operations, in 2004 and 2005. RESULTS: There was no serological evidence of infection with Newcastle disease, infectious bursal disease, or Salmonella Pullorum. Antibodies to infectious bronchitis virus, avian encephalomyelitis (AE) virus, Mycoplasma gallisepticum and Mycoplasma synoviae were detected. CONCLUSIONS AND CLINICAL RELEVANCE: The disease status of OEG birds is similar to that of commercial poultry.     

Epidemiologic characterization of Colorado backyard bird flocks

Backyard gallinaceous bird flocks may play an important role in the spread of infectious diseases within poultry populations as well as the transmission of zoonotic diseases to humans. An epidemiologic characterization was conducted of Colorado backyard flocks to gather information on general flock characteristics, human movement of birds, human-bird interaction, biosecurity practices, and flock health. Our results suggest that backyard poultry flocks in Colorado are small-sized flocks (68.6% of flocks had < 50 birds); consist primarily of layer chickens (85.49% of flocks), show chickens (32.18% of flocks), and waterfowl (34.07% of flocks); and are primarily owned for food (meat or egg) production for the family (86.44%) or as pet or hobby birds (42.27%). The backyard flock environment may promote bird-to-bird transmission as well as bird-to-human transmission of infectious disease. Birds are primarily housed with free access to the outside (96.85%), and many are moved from the home premises (46.06% within 1 yr). Human contact with backyard flocks is high, biosecurity practices are minimal, and bird health is negatively impacted by increased movement events. Increased knowledge of backyard bird characteristics and associated management practices can provide guidelines for the development of measures to decrease disease transmission between bird populations, decrease disease transmission from birds to humans, and increase the overall health of backyard birds.     

Laryngotracheitis in chickens: the length of the preinfectious and infectious periods

Transmission studies to measure the length of the infectious period and the interval between virus inoculation and infectiousness were conducted using the standard National Veterinary Services Laboratory laryngotracheitis (LT) challenge virus (Log 10(6.7) EID50 per ml). Previously unexposed sentinel chickens were placed in contact with chickens inoculated intratracheally with LT virus. Transmission of virus to the sentinel birds was assessed by studying clinical signs and results of virus isolation and challenge. Chickens began to shed infective quantities of virus 2-4 days postinoculation and continued until day 6.     

Experimental pathogenesis for chickens, turkeys, and pigeons of exotic Newcastle disease virus from an outbreak in California during 2002-2003

Exotic Newcastle disease virus (NDV) isolated from chickens during the 2002-2003 California outbreak (CA exotic Newcastle disease [END] virus) was inoculated into 4-week-old specific-pathogen-free (SPF) White Leghorn chickens, 3-week-old SPF Beltsville White turkeys, 6-week-old commercial Broad Breasted White turkeys, and 10- to 20-week-old racing pigeons, and the clinicopathologic features of disease were compared. Birds were monitored clinically and euthanized sequentially with collection of tissues. Tissues were examined by histopathology, by immunohistochemistry to detect viral nucleoprotein, and by in situ hybridization to detect viral mRNA. Clinically, infected chickens and SPF turkeys showed severe depression, and all died or were euthanized because of severe clinical signs by day 5 postinoculation. In these birds, histologic lesions were widespread and virus was detected in multiple organs. All infected commercial turkeys showed mild depression, and incoordination was observed in some birds. Histologic lesions were mild, and viral distribution was limited. In pigeons, only 1 bird showed overt clinical disease, and histologic lesions and viral distribution were present in limited organs. Consequently, susceptibility to highly virulent NDV was shown to vary among chickens, SPF turkeys, commercial turkeys, and pigeons. Additionally, we have evidence of CA END virus subclinical infections that suggest pigeons could be subclinical carriers of other virulent NDV.     

A standardized enzyme-linked immunosorbent assay for infectious bronchitis virus: comparison with hemagglutination-inhibition and virus-neutralization assays for measuring protective antibody levels in chickens

An enzyme-linked immunosorbent assay (ELISA) was developed to measure antibodies to infectious bronchitis virus (IBV) in chickens. The results are reported in IBV standard ELISA values calculated by comparing antibody levels in test sera with antibody levels in a series of standard reference sera. The IBV standard ELISA values were good indicators of responses to vaccination and the immune status of experimentally challenged birds. Although the assay was not serotype-specific, the sensitivity makes it ideally suited for determining the immune status of poultry flocks. The assay results compared favorably with other laboratory results, including virus-neutralization titers, hemagglutination-inhibition levels in sera, virus isolation from vaccinated/challenged birds, and the tracheal ring test results.     

Non-commercial poultry industries: surveys of backyard and gamefowl breeder flocks in the United States

The National Animal Health Monitoring System (NAHMS) Poultry '04 study was conducted to better describe non-commercial United States poultry populations, in particular, backyard and gamefowl breeder flocks. To estimate the density of backyard flocks in close proximity to commercial operations, a sample of 350 commercial poultry operations in 18 top poultry producing states was selected from the National Agricultural Statistics Service (NASS) list of poultry operations. A 1 mile radius circle was drawn around each operation, and door-to-door canvassing was conducted within these circles to enumerate premises with all species of birds. Premises with backyard poultry flocks completed a questionnaire focusing on bird health, bird movement, and biosecurity practices. A similar questionnaire, provided in both English and Spanish, was mailed to all members of State affiliates of the United Gamefowl Breeders Association (UGBA) as well as to members of State associations not affiliated with UGBA. An average of 29.4 residences was found within a 1 mile radius of commercial operations, of which 1.9 residences per circle had backyard poultry flocks. Gamefowl breeder flocks were larger, used more health care and biosecurity practices, and moved birds more frequently compared to backyard flocks.     

Influenza A viruses in birds and humans: Prevalence,molecular characterization,zoonotic significance and risk factors' assessment in poultry farms

This study aimed to investigate the prevalence of influenza A viruses in birds and humans residing in the same localities of Sharkia Province, Egypt and the risk factors' assessment in poultry farms. A total of 100 birds comprised of 50 chickens, 25 ducks and 25 wild egrets were sampled. Swab samples were collected from 65 people (50 poultry farm workers and 15 hospitalized patients). All samples were screened for the presence of influenza A viruses using isolation and molecular assays. Avian influenza viruses were only detected in chicken samples (18%) and molecularly confirmed as subtype H5. The infection rate was higher in broilers (40%) than layers (8.6%). Influenza A (H1) pdm09 virus was detected in a single human case (1.54%). All the isolated AI H5 viruses were clustered into clade (2.2.1.2) and shared a high similarity rate at nucleotides and amino acid levels. In addition, they had a multi-basic amino acid motif (ـــPQGEKRRKKR/GLFـــ) at the H5 gene cleavage site that exhibited point mutations. Chicken breed, movement of workers from one flock to another, lack of utensils' disinfection and the introduction of new birds to the farm were significant risk factors associated with highly pathogenic AI H5 virus infection in poultry farms (p ≤ 0.05). Other factors showed no significant association. The HPAI H5 viruses are still endemic in Egypt with continuous mutation. Co-circulation of these viruses in birds and pdm09 viruses in humans raises alarm for the emergence of reassortant viruses that are capable of potentiating pandemics.     

Investigation of H7N2 avian influenza outbreaks in two broiler breeder flocks in Pennsylvania, 2001-02

An avian influenza (AI) outbreak occurred in meat-type chickens in central Pennsylvania from December 2001 to January 2002. Two broiler breeder flocks were initially infected almost simultaneously in early December. Avian influenza virus (AIV), H7N2 subtype, was isolated from the two premises in our laboratory. The H7N2 isolates were characterized as a low pathogenic strain at the National Veterinary Services Laboratories based on molecular sequencing of the virus hemagglutinin cleavage site and virus challenge studies in specific-pathogen-free leghorn chickens. However, clinical observations and pathologic findings indicated that this H7N2 virus appeared to be significantly pathogenic in meat-type chickens under field conditions. Follow-up investigation indicated that this H7N2 virus spread rapidly within each flock. Within 7 days of the recognized start of the outbreak, over 90% seroconversion was observed in the birds by the hemagglutination inhibition test. A diagnosis of AI was made within 24 hr of bird submission during this outbreak using a combination of virus detection by a same-day dot-enzyme-linked immunosorbent assay and virus isolation in embryonating chicken eggs. Follow-up investigation revealed that heavy virus shedding (90%-100% of birds shedding AIV) occurred between 4 and 7 days after disease onset, and a few birds (15%) continued to shed virus at 13 days post-disease onset, as detected by virus isolation on tracheal and cloacal swabs. AIV was not detected in or on eggs laid by the breeders during the testing phase of the outbreak. The two flocks were depopulated at 14 days after disease onset, and AIV was not detected on the two premises 23 days after depopulation.     

Methods of spread of velogenic viscerotropic Newcastle disease virus in the southern Californian epidemic of 1971-1973.

Data collected during the velogenic viscerotropic Newcastle disease (VVND) epidemic that occurred in southern California from 1971 to 1973 were analyzed to determine the methods of spread of the disease. Spread between chicken flocks was extensive and due mainly to the movement of live birds and mechanical transport of virus by man, especially by vaccination and poultry service crews. Spread to exotic birds was from contact with infected imported stock. Spread to other species was most probably through contact with infected chickens. Infection persisted in commercial chicken flocks because of intensive vaccination programs, heavy traffic and contact between layer operations, and the maintenance of multi-age flocks. These foci of infection probably led to spread of the disease to areas from which VVND had been eradicated several months before. There was no evidence of significant wind-borne spread of virus between flocks.