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Newcastle disease (ND) is a frequently reported disease in poultry among both vaccinated and non-vaccinated flocks in Pakistan. During 2011-2012 poultry industry in Punjab, mainly in Lahore region, faced fatal outbreaks of ND caused by a variant strain. An analytical study was conducted during outbreak period in Lahore region. A total of 114 environmentally controlled farms were selected with the help of convenient sampling method. A questionnaire was designed about the potential risk factors associated with the spread of ND outbreak. The bivariate relationships between ND status and independent variables were investigated by applying the Chi-square and Fisher's exact test. Multivariable logistic model was used to estimate the effect of each studied variable on the outcome by adjusting the other variables in the model. The variables which showed an association with ND outbreaks at commercial poultry farms were improper method for dead birds disposal (OR=4.96; 95% CI 1.63-15.12), use of same feed transporting vehicle at multiple poultry farms (OR=4.92; 95% CI 1.58-15.33), farm to farm distance of less than 1 km (OR=9.32; 95% CI(1.19-73.12), number of sheds at one farm (OR=2.31; 95% CI 0.93-5.69), labor type (OR=2.72; 95% CI 0.83-8.88) and biosecurity (OR= 4.47; 95% CI 0.56-35.66)., (Copyright© by the Polish Academy of Sciences.)

Highly Pathogenic Avian Influenza (HPAI) subtype H5N8 outbreaks occurred in poultry farms in South Korea in 2014 resulting in significant damage to the poultry industry. Between 2014 and 2016, the pandemic disease caused significant economic loss and social disruption. To evaluate the risk factors for HPAI infection in broiler duck farms, we conducted a retrospective case-control study on broiler duck farms. Forty-three farms with confirmed laboratories on premises were selected as the case group, and 43 HPAI-negative farms were designated as the control group. Control farms were matched based on farm location and were within a 3-km radius from the case premises. Spatial and environmental factors were characterized by site visit and plotted through a geographic information system (GIS). Univariable and multivariable logistic regression models were developed to assess possible risk factors associated with HPAI broiler duck farm infection. Four final variables were identified as risk factors in a final multivariable logistic model: "Farms with ≥7 flocks" (odds ratio [OR] = 6.99, 95% confidence interval [CI] 1.34-37.04), "Farm owner with ≥15 years of raising poultry career" (OR = 7.91, 95% CI 1.69-37.14), "Presence of any poultry farms located within 500 m of the farm" (OR = 6.30, 95% CI 1.08-36.93) and "Not using a faecal removal service" (OR = 27.78, 95% CI 3.89-198.80). This highlights that the HPAI H5N8 outbreaks in South Korea were associated with farm owner education, number of flocks and facilities and farm biosecurity. Awareness of these factors may help to reduce the spread of HPAI H5N8 across broiler duck farms in Korea during epidemics. Greater understanding of the risk factors for H5N8 may improve farm vulnerability to HPAI and other subtypes and help to establish policies to prevent re-occurrence. These findings are relevant to global prevention recommendations and intervention protocols., (© 2018 Blackwell Verlag GmbH.)

Avian influenza and infectious laryngeotracheitis viruses are common causes of respiratory diseases in chickens with economical importance worldwide. In this study, we investigated the effect of experimental co-infection of avian influenza virus-H9N2 (AIV-H9N2) with infectious laryngeotracheitis virus (ILTV) live-attenuated vaccine (LAR-VAC ® ) on chickens. Four experimental groups were included in this study: negative control group, AIV-H9N2 group, AIV-H9N2+LAR-VAC ® group, and LAR-VAC ® group. AIV-H9N2 was inoculated intranasally to challenged groups at 35 days of age. On the same day, LAR-VAC ® was ocularly administered to vaccinated groups. Chickens were observed for clinical signs, changes in body weight and mortality rates. Tissue samples, sera, tracheal and cloacal swabs, and blood were also collected at 3, 6, 9 and 12 days post-infection (PI). A significant increase in clinical signs and mortality rates were observed in the AIV-H9N2 + LAR-VAC ® group. Moreover, chickens coinfected with AIV-H9N2 and LAR-VAC ® showed a significant decrease in body weight and lymphoid organs indices. The tracheal gross and histopathological lesions and the shedding titer and period of AIV-H9N2 were significantly higher in AIV-H9N2 + LAR-VAC ® group when compared to other groups. Furthermore, AIV-H9N2 infection leads to humoral and cellular immunosuppression as shown by a significant decrease in the CD4 + /CD8 + ratio and antibody responses to ILTV and a significant increase in H/L ratio. In conclusion, this is the first report of co-infection of AIV-H9N2 and ILTV vaccine in chickens, which leads to increased pathogenicity, pathological lesions, and AIV-H9N2 shedding titer and period, which can lead to severe economic losses due to poor weight gain and mortality., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Soon after the emergence of 2009 pandemic H1N1, the first outbreaks in breeder turkey operations were reported that implicated human-to-turkey transmission. In the spring of 2016, the reoccurrence of 2009 pandemic H1N1 lineage viruses infecting breeder turkey flocks in Ontario and Manitoba, Canada, also implicated human-to-turkey transmission. In addition to raising concerns over biosecurity and vaccine failures, these cases once again raise the issue of whether turkeys have the potential to act as a bridge species to generate novel influenza A virus reassortants with public health implications., (© 2016 Her Majesty the Queen in Right of Canada.)

We introduce a model of avian influenza in domestic birds with imperfect vaccination and age-since-vaccination structure. The model has four components: susceptible birds, vaccinated birds (stratified by vaccination age), asymptomatically infected birds, and infected birds. The model includes reduction in the probability of infection, decreasing severity of disease of vaccinated birds and vaccine waning. The basic reproduction number, [Formula: see text], is calculated. The disease-free equilibrium is found to be globally stable under certain conditions when [Formula: see text]. When [Formula: see text], existence of an endemic equilibrium is proved (with uniqueness for the ODE case and local stability under stricter conditions) and uniform persistence of the disease is established. The inclusion of reduction in susceptibility of vaccinated birds, reduction in infectiousness of asymptomatically infected birds and vaccine waning can have important implications for disease control. We analytically and numerically demonstrate that vaccination can paradoxically increase the total number of infected, resulting in the "silent spread" of the disease. We also study the effects of vaccine efficacy on disease prevalence and the minimum critical vaccination coverage, a threshold value for vaccination coverage to avoid an increase in total disease prevalence due to asymptomatic infection.

Newcastle disease (ND) and avian influenza (AI) are issues of interest to avian producers in Madagascar. Newcastle disease virus (NDV) is the major constraint for village aviculture, and avian influenza viruses type A (AIAV) are known to circulate in bird flocks. This study aims at classifying smallholder poultry farms, according to the combination of risk factors potentially associated with NDV and AIAV transmission and to assess the level of infection for each farm class. Two study sites, Lake Alaotra and Grand Antananarivo, were chosen with respect to their differences in terms of agro-ecological features and poultry productions. A typology survey involving 526 farms was performed to identify possible risk factors for (i) within-village, and (ii) between-village virus transmission. A cross-sectional serological study was also carried out in 270 farms to assess sero-prevalences of NDV and AIAV for each farm class and the link between them and risk factor patterns. For within-village transmission, four classes of farms were identified in Grand Antananarivo and five in Lake Alaotra. For between-village virus transmission, four classes of farms were identified for each site. In both sites, NDV sero-prevalence was higher than for AIAV. There was no evidence of the presence of H5 or H7 subtypes of AIAV. Sero-prevalences were significantly higher in Lake Alaotra than in Grand Antananarivo for both viruses (OR=2.4, p=0.02 for NDV, and OR=9.6, p<0.0001 for AIAV). For within-village NDV transmission in Grand Antananarivo, backyard chicken farms (OR=3.6, p<0.001), and chicken farms with biosecurity awareness (OR=3.4, p<0.01) had greater odds of having antibodies against NDV than the others. For between-village virus transmission, farms with multiple external contacts, and farms using many small markets had greater odds of having antibodies against NDV than the others (OR=5.4, p<0.01). For AIAV, there were no differences in sero-prevalences among farm classes. In Lake Alaotra, the observed high density of palmipeds and widespread rice paddies were associated with high sero-prevalences for both viruses, and a homogeneous risk of virus transmission between the different farm classes. In Grand Antananarivo, farm visits by collectors or animal health workers, and farm contacts with several markets were identified as potential risk factors for NDV transmission. Further studies are needed to identify the circulating virus genotypes, model their transmission risk, and provide adapted control measures., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Since 1994, the domestic poultry in Pakistan has experienced several outbreaks due to avian influenza viruses of subtypes H7N3, H5N1, and H9N2. This paper reveals horizontal contacts and potential risk factors for the spread of avian influenza infection between open-sided chicken farms in Kamalia, a sub-district of Punjab province. Between April and June 2009, an interview-based questionnaire was administered to a sample of 78 growers. The survey identified the following potential biosecurity risks for outbreak propagation: i) short buffer distances between farms, ii) disposal of carcasses and other organic wastes into the environment, iii) entry of feral birds into poultry sheds, iv) visits of poultry farmers to possible cross-contamination sites, v) absence of boundary walls, vi) incomplete biosecurity on high-risk visitors (i. e. those going inside the poultry houses), essential vehicles and equipment used by vaccination crews vii) visits of intermediaries and service providers and, viii) sharing of egg trays between farms at production. For most of the variables, there was no significant difference between the broiler and layer type of farms (p < or = 0.05). The risk of an extensive outbreak in Kamalia was concluded to be due to its high poultry density, ubiquitous small-scale, market-oriented poultry production with medium to low biosecurity, and the affiliation of the farmers to multiple service providers. To reduce the risk of having an outbreak, farm-specific biosecurity gaps should be identified and appropriate action taken to close these gaps. Improvement in biosecurity and targeted surveillance are therefore considered critical to limit the spread of infection should an outbreak occur.

Introduction: Backyard poultry raising is common in rural communities and a valued resource that provides food and income for subsistence farmers. Close contact with infected backyard poultry has been associated with H5N1 human cases in different countries. The emergence of this virus within Bangladesh means that backyard poultry raisers are at risk of avian influenza infections. The aim of this study was to understand why people raise backyard poultry and to characterize people's regular interaction with their poultry., Methods: In 2008, a qualitative study was conducted in two villages from two districts of Bangladesh. In a social mapping exercise the villagers drew all the households in their village: 115 households in the village in Netrokona and 85 households in the village in Rajshahi District. Selected were 40 households (20 households from each of the two villages) for data collection through in-depth interviews (n=40) and household mapping (n=40), and observation sessions (n=16)., Results: In both villages, 92% of households raised backyard poultry. The majority of the owners was female and used the money earned from poultry raising to purchase cooking ingredients, clothing, and agricultural seeds, and pay for children's education expenses. The households consumed poultry meat and eggs. In the village in Netrokona, 80% (85/106) of households kept poultry inside the bedroom. In the village in Rajshahi, 87% (68/78) of households had separate cage/night sheds. During feeding the poultry and cleaning the poultry raising areas, villagers came into contact with poultry and poultry feces. Poultry scavenged for food on the floor, bed, in the food pot and around the place where food was cooked. Poultry drank from and bathed in the same body of water that villagers used for bathing and washing utensils and clothes., Conclusion: Although raising poultry provides essential support to the families' livelihoods, it exposes them to the risk of avian influenza through close contact with their poultry. Simple warnings to avoid poultry contact are unlikely to change practices that are essential to household survival. Interventions that help to protect poultry flocks and improve household profitability are more likely to be practiced.

We assessed the prediction that access of the viral NS1 protein to cellular PDZ domain protein networks enhances the virulence of highly pathogenic avian influenza A viruses. The NS1 proteins of most avian influenza viruses bear the C-terminal ligand sequence Glu-Ser-Glu-Val (ESEV) for PDZ domains present in multiple host proteins, whereas no such motif is found in the NS1 homologues of seasonal human virus strains. Previous analysis showed that a C-terminal ESEV motif increases viral virulence when introduced into the NS1 protein of mouse-adapted H1N1 influenza virus. To examine the role of the PDZ domain ligand motif in avian influenza virus virulence, we generated three recombinants, derived from the prototypic H5N1 influenza A/Vietnam/1203/04 virus, expressing NS1 proteins that either have the C-terminal ESEV motif or the human influenza virus RSKV consensus or bear a natural truncation of this motif, respectively. Cell biological analyses showed strong control of NS1 nuclear migration in infected mammalian and avian cells, with only minor differences between the three variants. The ESEV sequence attenuated viral replication on cultured human, murine, and duck cells but not on chicken fibroblasts. However, all three viruses caused highly lethal infections in mice and chickens, with little difference in viral titers in organs, mean lethal dose, or intravenous pathogenicity index. These findings demonstrate that a PDZ domain ligand sequence in NS1 contributes little to the virulence of H5N1 viruses in these hosts, and they indicate that this motif modulates viral replication in a strain- and host-dependent manner.

The 2009 H1N1 and H5N1 influenza viruses are newly (re-) emerged influenza A viruses (2009 A(H1N1) and A(H5N1), respectively) that have recently posed tremendous health threats in many regions worldwide. With the 2009 outbreak of H1N1 influenza A, the world witnessed the first influenza pandemic of the 21st century. The disease has rapidly spread across the entire globe, and has resulted in hundreds of thousands of cases with confirmed infection. Although characterized by high transmissibility, the virulence and fatality of the 2009 A(H1N1) influenza virus have thus far remained relatively low. The reverse holds true for A(H5N1) influenza; at a fatality rate that exceeds 60%, it is known to cause severe damage to the human respiratory system, but is not presently capable of efficient transmission from human to human. Apart from the clear differences between the two types of influenza, there are some significant similarities that warrant attention. In particular, the more severe and fatal 2009 A(H1N1) influenza cases have shown symptoms similar to those reported in cases of A(H5N1) influenza. Histopathological findings for these cases, to the extent available, also appear to have similarities for both diseases in terms of damage and severity. Here we review important recent publications in this area, and we discuss some of the key commonalities and contrasts between the two influenza A types in terms of their biology, origins, clinical features, pathology and pathogenesis, and receptors and transmissibility.

Avian influenza commonly called as 'Bird flu' is a matter of great concern which has caused three major pandemics in twentieth century killing millions of people. Recent epidemic with H5N1 type strain started in 1997 and is still continuing. Disease has assumed new proportions since its confirmed association with migratory birds. In India also, three separate outbreaks have been announced till now by Government of India. This virus has tremendous capacity for gene reassortment and humans by enlarge do not have any immunity against them. This fact has raised global fears of an imminent influenza pandemic. The neuraminidase inhibitors currently are the only drugs which can be used, in case pandemic occurs. Therefore, timely development of an effective influenza vaccine is must and should be made a public health priority.

Among emerging and re-emerging infectious diseases, influenza constitutes one of the major threats to mankind. In this review series epidemiologic, virologic and pathologic concerns raised by infections of humans with avian influenza virus A/H5N1 are discussed. The second part focuses on experimental and clinical results, which give insights in the pathogenic mechanisms of H5N1 infection in humans. H5N1 is poorly transmitted to humans. However, H5N1-induced disease is very severe. More information on the role entry barriers, H5N1 target cells and on H5N1-induced modulation of the host immune response is needed to learn more about the determinants of H5N1 pathogenicity.

The identification of H5N1 in domestic poultry in Europe has increased the risk of infection reaching most industrialized poultry populations. Here, using detailed data on the poultry population in Great Britain (GB), we show that currently planned interventions based on movement restrictions can be expected to control the majority of outbreaks. The probability that controls fail to keep an outbreak small only rises to significant levels if most transmission occurs via mechanisms which are both untraceable and largely independent of the local density of premises. We show that a predictor of the need to intensify control efforts in GB is whether an outbreak exceeds 20 infected premises. In such a scenario neither localized reactive vaccination nor localized culling are likely to have a substantial impact. The most effective of these contingent interventions are large radius (10 km) localized culling and national vaccination. However, the modest impact of these approaches must be balanced against their substantial inconvenience and cost.

In January 2006, an outbreak of a highly pathogenic avian influenza (HPAI) was recorded in Nigeria for the first time. This present work describes an estimation of possible costs associated with a vaccination-based control policy added to other measures to restrict HPAI H5N1 virus infections. The evaluations used epidemiological and production data, including budgets necessary for the vaccine acquisition, distribution and administration in arriving at the final costs. Using decision tree and cost benefit analysis the economical benefits for Nigeria and countries with similar veterinary infrastructures, biosecurity and farming systems are calculated. The result indicated that a halting in the continued spread of the virus through effective control measure will be 52 times better than taking no action. This should help policy makers in deciding in favour of vaccination combined with other tools as an effective means of controlling avian influenza H5N1. * Control of HPAI H5N1 will best be understood by policy makers in financial terms. * Effective control through vaccination of poultry is much cheaper and reduces the chances of human zoonoses. * Poultry vaccination combined with other control measures will be the most effective means of control in most developing economies.

Since 2002, H5N1 highly pathogenic avian influenza (HPA1) viruses have been associated with deaths in numerous wild avian species throughout Eurasia. We assessed the clinical response and extent and duration of viral shedding in 5 species of North American ducks and laughing gulls (Larus atricilla) after intranasal challenge with 2 Asian H5N1 HPAI viruses. Birds were challenged at approximately equal to 10 to 16 weeks of age, consistent with temporal peaks in virus prevalence and fall migration. All species were infected, but only wood ducks (Aix sponsa) and laughing gulls exhibited illness or died. Viral titers were higher in oropharyngeal swabs than in cloacal swabs. Duration of viral shedding (1-10 days) increased with severity of clinical disease. Both the hemagglutination-inhibition (HI) and agar gel precipitin (AGP) tests were able to detect postinoculation antibodies in surviving wood ducks and laughing gulls; the HI test was more sensitive than the AGP in the remaining 4 species.

During an outbreak of avian influenza in the Netherlands in spring 2003, the disease was controlled by destroying all the poultry on the infected farms and on all the farms within a radius of 3 km. In total, 30 million birds were killed on 1242 farms and in more than 8000 hobby flocks, by using mobile containers filled with carbon dioxide, mobile electrocution lines and by gassing whole poultry houses with carbon monoxide or carbon dioxide. Observations of these methods were used to compare their effectiveness and capacity, and their effects on the welfare of the birds. Gassing whole poultry houses had a much greater capacity than mobile equipment, and catching live birds to bring them to a mobile killing device caused extra stress and could cause pain due to injuries inflicted when catching and handling them. Gassing whole poultry houses with carbon monoxide requires strict safety regulations and, therefore, gassing with carbon dioxide was considered preferable. However, this method is not suited to all types of housing, and in these circumstances mobile killing devices were a useful alternative.

We evaluated the effects of risk factors and control policies following the highly pathogenic avian influenza (HPAI) epidemic that struck northern Italy's poultry industry in the winter of 1999-2000. The epidemic was caused by a type-A influenza virus of the H7N1 subtype, that originated from a low-pathogenic AI virus which spread among poultry farms in northeastern Italy in 1999 and eventually became virulent by mutation. Most infected premises (IP) were located in the regions of Lombardy and Veneto (382 out of 413, 92.5%), and the eradication measures provided for in the European legislation were enforced. In Veneto, where flock density was highest, infection-control was also accomplished by means of depopulation of susceptible flocks through a ban on restocking and pre-emptive slaughter of flocks that were in the vicinities of or that had dangerous contacts with IPs. In Lombardy, such control measures were applied to a lesser extent. Infection incidence rate (IR) was 2.6 cases per 1000 flocks per day in Lombardy and 1.1 in Veneto. After the implementation of infection-control measures, the at-risk population, the percentage of flocks < or =1.5 km from IPs, and the HPAI-IR underwent a greater reduction in Veneto than in Lombardy. Although the proximity (< or =1.5 km) to IPs in the temporal risk window (TRW) was a major risk factor for HPAI at the individual flock level, its effect at the population level (population-attributable fraction) did not exceed 31.3%. Viral transmission therefore also occurred among relatively distant flocks. Turkey flocks were characterised by greater IR of HPAI compared with other bird species such as layer hens, broilers, gamebirds, and waterfowl, even when located at distances >1.5 km from IPs. In Lombardy, IR for species other than turkeys was also relatively high.

We examined the pathogenicity for chickens of two H5N1 avian influenza viruses isolated in Japan, A/chicken/ Yamaguchi/7/2004 (Ck/Yamaguchi/7/04) isolated from outbreaks in commercial layer chickens, and A/duck/Yokohama/aq10/ 2003 (Dk/Yokohama/aq10/03) isolated from duck meat imported from China. All chickens inoculated intranasally with either strain died, and the viruses were reisolated from all organs examined. However, both the mean time of onset of clinical signs and the mean death time of Ck/Yamaguchi/7/04 were shorter than those of Dk/Yokohama/aq10/03.

An epidemic of high pathogenicity Avian Influenza (HPAI) occurred in the Netherlands in 2003. A census survey of 173 infected and 401 uninfected commercial poultry farms was carried out to identify factors associated with the introduction of the HPAI virus into poultry farms. Data on farm size, production characteristics, type of housing, presence of cattle and pigs were gathered by the National Inspection Service for Livestock and Meat from all farms included in this study. For each risk factor (RF) available for analysis, the Mantel-Haenszel odds ratio was calculated (stratified on farm size and housing type). We found an increased risk of HPAI virus introduction in layer finisher type poultry: OR = 2.05 (95% confidence interval, CI = 1.29-3.27). An explanation for this increased risk is the high number of contacts between these farms, especially via cardboard egg trays used for removal of eggs during the epidemic. Our analysis did not indicate significant differences between the infected and uninfected farms with regard to housing type, presence of cattle or pigs. Since layer finisher type farms are assumed to be at higher risk for HPAI virus introduction, more specific control measures might be applied in future outbreaks.

Although it is established that the cleavage site and glycosylation patterns in the hemagglutinin (HA) play important roles in determining the pathogenicity of H5 avian influenza viruses, some viruses exist that are not highly pathogenic despite possessing the known characteristics of high pathogenicity (i.e., their HA contains multiple basic amino acids at the cleavage site and has glycosylation patterns similar to that of the highly pathogenic H5 viruses). Currently little is known about the H5N1 viruses that fall into this intermediate category of pathogenicity. We have identified strains of H5N1 avian influenza viruses that have markers typical of high pathogenicity but distinctly differ in their ability to cause disease and death in chickens. By analyzing viruses constructed by reverse-genetic methods and containing recombinant HAs, we established that amino acids 97, 108, 126, 138, 212, and 217 of HA, in addition to those within the cleavage site, affect pathogenicity. Further investigation revealed that an additional glycosylation site within the neuraminidase (NA) protein globular head contributed to the high virulence of the H5N1 virus. Our findings are in agreement with previous observations that suggest that the activities of the HA and NA proteins are functionally linked., (Copyright 2004 American Society for Microbiology)

During the spring of 2002, a low pathogenic avian influenza (LPAI) A (H7N2) virus caused a major outbreak among commercial poultry in Virginia and adjacent states. The virus primarily affected turkey flocks, causing respiratory distress and decreased egg production. Experimentally, turkeys were more susceptible than chickens to H7N2 virus infection, with 50% bird infectious dose titers equal to 10(0.8) and 10(2.8-3.2), respectively. Comparison of virus shedding from the cloaca and oropharynx demonstrated that recent H7N2 virus isolates were readily isolated from the upper respiratory tract but rarely from the gastrointestinal tract. The outbreak of H7N2 virus raised concerns regarding the availability of vaccines that could be used for the prevention and control of this virus in poultry. We sought to determine if an existing commercial avian influenza (AI) vaccine prepared from a 1997 seed stock virus could provide protection against a 2002 LPAI H7N2 virus isolated from a turkey (A/turkey/Virginia/158512/02 [TV/02]) in Virginia that was from the same lineage as the vaccine virus. The inactivated AI vaccine, prepared from A/chicken/ Pennsylvania/21342/97 (CP/97) virus, significantly reduced viral shedding from vaccinated turkeys in comparison with sham controls but did not prevent infection. The protective effect of vaccination correlated with the level of virus-specific antibody because a second dose of vaccine increased antiviral serum immunoglobulin G and hemagglutination inhibition (HI) reactivity titers in two different turkey age groups. Serum from CP/97-vaccinated turkeys reacted equally well to CP/97 and TV/02 antigens by HI and enzyme-linked immunosorbent assay. These results demonstrate the potential benefit of using an antigenically related 1997 H7N2 virus as a vaccine candidate for protection in poultry against a H7N2 virus isolate from 2002.

Comparative histological and immunocytochemical studies were conducted on formalin-fixed tissues from chickens infected with avian influenza viruses of varying virulence. Results showed a distinct pattern of disease that depended on the virulence of the virus and the susceptibility of the birds. At 3 days post-intranasal inoculation with a highly virulent H7N7 virus, all 6-to-8-week-old specific-pathogen-free (SPF) birds were affected, and all developed pancreatic necrosis and encephalitis associated with specific immunoperoxidase staining. Other same-aged SPF birds were only occasionally affected 6 to 8 days after intravenous inoculation with almost avirulent H4N4, H6N2, or H3N8 virus. Specific lesions and immunoperoxidase staining were noted in the kidneys only. The H7N7 virus in older commercial birds and an H7N3 virus in young SPF and older commercial birds caused intermediate mortality rates at 4 to 11 days postinoculation, and there was a broad range of lesions and specific immunoperoxidase staining in the pancreas, brain, kidney, heart, and skeletal muscle. Two exceptional birds had immunostaining of small blood vessels throughout their bodies with or without lesions or staining in the tissues, which may have represented a transitory pre-localizing phase occurring in many birds. There was necrosis without virus antigen detection in the bursae, thymuses, and cecal tonsils, possibly secondary to stress or only transitory infection of virus. These data indicate that rapid, retrospective diagnosis of avian influenza in fixed tissues is possible by using an immunoperoxidase test on pancreas, brain, and kidney.

Avian influenza virus (AIV) of waterfowl origin, A/Mallard/Ohio/184/86 (H5N1), was used to evaluate the effect of AIV infection on the functional capabilities of the immune system in mallard ducks. The three main arms of the immune system--humoral, cell-mediated, and cellular--were evaluated. The integrity of the humoral immune system after AIV infection was evaluated by measuring total immunoglobulin and IgG antibody production to sheep erythrocytes and Brucella abortus antigen using hemagglutination and microagglutination assays, respectively. Cell-mediated immunity was evaluated using mitogen/antigen stimulation assays, and by measuring the cutaneous basophilic hypersensitivity response to intradermal phytohemagglutinin-P inoculation. The cellular component of the immune response was evaluated using whole-blood chemiluminescence and bacterial clearance assays. Results showed that infection with this AIV isolate suppressed T-cell function and enhanced macrophage phagocytic activity.

The pathogenicity potential of two H13N2 influenza viruses, one isolated from turkeys and the other isolated from surface water, was evaluated in turkeys, chickens, and mallard ducks (Anas platyrhynchos) after intracranial and oculonasal inoculation. Both isolates replicated in turkey poults, causing depressed weight gain, morbidity and mortality; both also caused histopathological lesions, such as mild to severe pancreatitis, hepatitis, and nephritis in turkeys. These isolates replicated in mallard ducklings but not in chickens. There was depressed weight gain in ducklings given the H13N2 isolate from water. Neither isolate caused morbidity or mortality in ducklings or chicks after inoculation.

The virulent avian influenza virus A/Ty/Ont/7732/66 (H5N9) (Ty/Ont) causes a rapid destruction of lymphoid cells in infected birds. Avian macrophage cell lines, HD11 and MQ-NCSU, support productive replication of Ty/Ont and other influenza viruses. Therefore, the ability of these cell lines to produce nitric oxide (NO), a potentially cytotoxic mediator, in response to infection with Ty/Ont was examined. Although treatment with bacterial lipopolysaccharides (LPS) resulted in high NO levels, infection of macrophages with Ty/Ont resulted in NO levels lower than NO levels in untreated cells. Furthermore, Ty/Ont was able to inhibit the positive response to LPS in cultures simultaneously treated with LPS and virus. However, inactivated influenza virus did not exhibit this inhibitory effect. Different strains of influenza virus varied in their ability to inhibit NO production by the macrophages; this may be related to the level of virus replication in these cells. These data suggest that the ability of the avian macrophage to activate the NO synthesis pathway is seriously impaired by infection with virulent influenza viruses such as Ty/Ont.

Groups of 10 two-week-old chicks, turkey poults and ducklings were each infected by the intranasal route with one of four avian influenza viruses: a/fowl/Germany/34 (Hav 1N))--Rostock, A/FPV/Dutch/27 (Hav 1 Neq 1)--Dutch, A/fowl/Victoria/75 (Hav 1 Neq 1)--Australian, and A/parrot/Ulster/73 (Hav 1 N1)--Ulster. Eight hours after infection 10 birds of the same age and species were placed in contact with each group and allowed to mix. The clinical signs of disease and onset of sickness and death were recorded. Ulster virus was completely avirulent for all birds. Rostock, Dutch and Australian viruses were virulent for fowls and turkeys causing death in all birds with the exception of 3/10 in contact fowls from the Rostock virus group and 2/10 in contact fowls from the Australian virus group. Only Rostock virus caused sicked sickness or death in ducks, 9/10 intranasally infected and 6/7 in contact birds showed clinical signs and 2/10 intranasally infected and 3/7 in contact ducks died. Intranasal and in contact pathogenicity indices were calculated for each virus in each bird species and indicated quantitatively the differences in virulence of the four virus strains. Virus isolation and immune response studies indicated that surviving in contact fowls in the Rostock virus group had never been infected but that surviving Australian virus in contact fowls had recovered from infection. Infection was not established in Ulster virus in contact fowls and Australian virus intranasally infected and in contact ducks. The birds in all other groups showed positive virus isolations and a high incidence of positive immune response. The last virus isolation was made at 22 days after intranasal infection of ducks with Ulster virus.

Seven influenza viruses isolated from turkeys in Great Britain since 1963 were typed by haemagglutination inhibition and neuraminidase inhibition tests as: A/turkey/England/63 (Hav 1 Nav 3), A/turkey/England/66 (Hav 6 N2), A/turkey/England/69 (Hav 7 N2), A/turkey/Scotland/70 (Hav ? Neq 1), A/turkey/England/N28/73 (Hav 5 N2), A/turkey/England/110/77 (Hav 6 N2), A/turkey/England/647/77 /Hav 1 Neq 1). A/turkey/Scotland/70 failed to show a haemagglutinin relationship with any of the representative strains and may possess a hitherto unreported haemagglutinin subtype. Intravenous pathogenicity tests in six-week-old birds showed only A/turkey/England/63 to have high virulence for turkeys and chickens. A/turkey/England/69 produced some signs of disease in chickens and, to a lesser extent, turkeys but all other isolates were avirulent.

The intravenous and intracerebral pathogenicity index tests normally used for Newcastle disease virus isolates were used to measure the virulence of 13 avian influenza viruses. The tests allowed quantitative measurements of the virulence of the avian influenza viruses, and the results confirmed the range in virulence, between the two extremes, of the avian influenza viruses and demonstrated the lack of correlation between virulence and antigenic type.

Avian influenza outbreaks in Minnesota involving the H10N7 subtype occurred on two turkey farms in 1979 and on a third in 1980. The H10N7 (Hav2 Neq1) subtype had not previously been detected in turkeys in Minnesota or reported in the United States. The clinical signs ranged from severe, with a mortality rate as high as 31%, to subclinical. Antigenically indistinguishable viruses were isolated from healthy mallards on a pond adjacent to the turkey farms, suggesting that the virus responsible for the outbreak may have been introduced by feral ducks.