Pathogenic Avian Influenza H5N1 Outbreaks Research Articles

Qualitative Assessment of the Clinico-Pathological Features of Highly Pathogenic Avian Influenza H5N1 Outbreaks in Commercial Poultry and Peri-Domestic Birds in Northern Nigeria

The control of highly pathogenic avian influenza (HPAI) in Nigeria from inception is predicated on effective biosecurity by stamping out policy but outbreaks of the disease continued to re-occur with altered clinico-pathologic manifestations. This study undertook the qualitative assessment of the clinico-pathological features of HPAI H5N1 during the 2021/2022 outbreaks in commercial poultry and peri-domestic birds in northern Nigeria. A total of 22 commercial poultry farms with 53,932 laying chickens and 3 households with 120 backyard broiler chickens, 18 indigenous chickens, 10 peafowls and 9 geese were investigated for HPAI. The clinico-pathologic manifestations observed in commercial poultry were subtle compared to previous presentations of the disease except in the peafowls, geese, broilers and indigenous chickens. The interspecies mortality rates significantly varied from 1.6% to 19.6% for laying chickens and 33.3% to 100% for broilers, indigenous chickens, geese and peafowls. Based on the history of sudden and high mortality, clinical signs and post mortem lesions observed, three diseases; HPAI, very virulent Newcastle disease and fowl cholera were drawn out as differential diagnoses. However, a tentative diagnosis of HPAI was made and samples were sent to the National Veterinary Research Institute, Vom, Plateau State, Nigeria for confirmatory diagnosis. Results of the laboratory tests conducted on the samples using one step flu A screening and duplex real time RT-PCR, and virus isolation in embryonated chicken eggs confirmed HPAI H5N1 in twenty-five farms. It is concluded that the continuous though, irregular outbreaks of HPAI and emerging clinico-pathologic manifestations are pointers to failure of control and that the disease may become endemic. It is recommended that government should review its policy on the control of HPAI to include the adoption of zoned vaccination with close monitoring.

The Pattern of Highly Pathogenic Avian Influenza H5N1 Outbreaks in South Asia.

Highly pathogenic avian influenza (HPAI) H5N1 has caused severe illnesses in poultry and in humans. More than 15,000 outbreaks in domestic birds from 2005 to 2018 and 861 human cases from 2003 to 2019 were reported across the world to OIE (Office International des Epizooties) and WHO (World Health Organization), respectively. We reviewed and summarized the spatial and temporal distribution of HPAI outbreaks in South Asia. During January 2006 to June 2019, a total of 1063 H5N1 outbreaks in birds and 12 human cases for H5N1 infection were reported to OIE and WHO, respectively. H5N1 outbreaks were detected more in the winter season than the summer season (RR 5.11, 95% CI: 4.28–6.1). Commercial poultry were three times more likely to be infected with H5N1 than backyard poultry (RR 3.47, 95% CI: 2.99–4.01). The highest number of H5N1 outbreaks was reported in 2008, and the smallest numbers were reported in 2014 and 2015. Multiple subtypes of avian influenza viruses and multiple clades of H5N1 virus were detected. Early detection and reporting of HPAI viruses are needed to control and eliminate HPAI in South Asia.

Effects of Highly Pathogenic Avian Influenza H5N1 Outbreak in Nepal from Financial and Social Perspectives: A Case Study

The outbreaks of highly pathogenic avian influenza (HPAI) H5N1 have serious public health, economic and social implications. After the first two report of HPAI H5N1 outbreak in Nepal in Jhapa in 2009, a third outbreak was reported in Pokhara the following year where more than 11,000 birds were culled to control the disease. However, the financial and social effects of the Pokhara bird flu outbreak were never assessed. The objectives of this study were to evaluate the local financial and social effects of HPAI H5N1 outbreak in Pokhara and to understand farmers and consumers perceptions on bird flu and the control measures implemented by the government. A total of 200 people including poultry farmers, butchers, veterinary drug dealers, feed suppliers, and consumers were interviewed using the semi-structured questionnaire. The result showed that the direct loss of Pokhara bird flu outbreak from the culling of birds was more than 4.5 million Nepali rupees. The small scale commercial and backyard farmers and the butchers were the most affected from this outbreak. A large proportion of the consumers temporarily stopped to consume chicken meat and shifted to other meat sources. Most of the participants in this study had at least heard about the bird flu. The farmers were unhappy by the compensation provided by the government and perceived that the government control efforts were not satisfactory and were provided little assistance for their rehabilitation. In conclusion, there was a momentary local financial and social effect of the Pokhara bird flu outbreak which may not very important from the macroeconomic point of view but is important for the affected small-scale farmers and the butchers. It is recommended that the government review their policy and provide small scale commercial and backyard farmer a compensation that is closer to the market price and promote largescale poultry farmers to go for insurance.

Circulating H5N1 virus among native chicken living around commercial layer farms

Soon after the application of vaccination programme against high pathogenic avian influenza H5N1 outbreak of the disease in breeder and commercial layer farms has diminished remarkably in West Java. This study aimed to investigate whether the H5N1 decline is related to the disappearance of source of infection around the farms. Serum samples were collected from 421 native chicken living around commercial layer farms in the Districs of Cianajur and Sukabumi, West Java in March-April 2014. Antibodies to avian influenza virus (AIV) H5N1 were measured using haemaglutination inhibition (HI), ELISAs and immunoblotting that measured presence of antibodies to the haemagglutin of H5N1 strain, as well as the M2e and nucleoprotein (NP) of all avian influenza viruses. Based on the combined results, 8.6% of the native chickens were seropositive to AI virus based on one or more of serological tests. This study provided serological evidence that H5N1 virus was still circulating among native chicken living around commercial layer farms. Many positive sera were however positive for antibodies in one test only: 2.4%, 3.3% and 3.8% by HI test, M2e and NP ELISA, respectively. It could be speculated that the incongruity of the results is due to the fact that HI, MM2e ELISA and NP ELISA all measure different type of antibodies and the duration of these antibodies in serum following infection with H5N1 differ. The fact that H5N1 virus is still circulating around commercial layer farms infers that the commercial farms are still under threat and therefore vaccination and strict biosecurity are still needed.

Mortality and Pathology Associated with Highly Pathogenic Avian Influenza H5N1 Outbreaks in Commercial Poultry Production Systems in Nigeria.

Commercial layer-type, pullet, cockerel, and broiler chicken flocks infected with highly pathogenic avian influenza (HPAI) H5N1 in Nigeria between 2006 and 2008 were investigated for morbidity, mortality, and pathology. Of the one hundred and fifty-three (153) farms confirmed with HPAI infection, one hundred and twenty-seven (127) were layer-type farms, nine (9) were pullet and broiler farms each, and eight (8) were cockerel rearing farms. This study revealed the morbidity and mortality of a total of 939,620 commercial layer chickens, 16,421 pullets, 3,109 cockerels, and 6,433 broilers. Mortality rates were 11.11% in commercial layers, 26.84% in pullets, 45.51% in cockerels, and 73.92% in broilers in a total of eighteen (18) states and the Federal Capital Territory, Abuja. A total of 316 carcasses were examined of which 248 were commercial layer, 25 were pullet, 14 were cockerel, and 29 were broiler. Main clinical and pathologic findings were observed in the nervous, circulatory, respiratory, integumentary, musculoskeletal, hemopoietic, gastrointestinal, and reproductive systems and, occasionally, lesions were generally nonspecific and multisystemic. Lesions occurred more frequently, severely, and in most of the carcasses examined, irrespective of chicken type.

Different Environmental Drivers of Highly Pathogenic Avian Influenza H5N1 Outbreaks in Poultry and Wild Birds

A large number of highly pathogenic avian influenza (HPAI) H5N1 outbreaks in poultry and wild birds have been reported in Europe since 2005. Distinct spatial patterns in poultry and wild birds suggest that different environmental drivers and potentially different spread mechanisms are operating. However, previous studies found no difference between these two outbreak types when only the effect of physical environmental factors was analysed. The influence of physical and anthropogenic environmental variables and interactions between the two has only been investigated for wild bird outbreaks. We therefore tested the effect of these environmental factors on HPAI H5N1 outbreaks in poultry, and the potential spread mechanism, and discussed how these differ from those observed in wild birds. Logistic regression analyses were used to quantify the relationship between HPAI H5N1 outbreaks in poultry and environmental factors. Poultry outbreaks increased with an increasing human population density combined with close proximity to lakes or wetlands, increased temperatures and reduced precipitation during the cold season. A risk map was generated based on the identified key factors. In wild birds, outbreaks were strongly associated with an increased Normalized Difference Vegetation Index (NDVI) and lower elevation, though they were similarly affected by climatic conditions as poultry outbreaks. This is the first study that analyses the differences in environmental drivers and spread mechanisms between poultry and wild bird outbreaks. Outbreaks in poultry mostly occurred in areas where the location of farms or trade areas overlapped with habitats for wild birds, whereas outbreaks in wild birds were mainly found in areas where food and shelters are available. The different environmental drivers suggest that different spread mechanisms might be involved: HPAI H5N1 spread to poultry via both poultry and wild birds, whereas contact with wild birds alone seems to drive the outbreaks in wild birds.

Limiting worker exposure to highly pathogenic avian influenza a (H5N1): a repeat survey at a rendering plant processing infected poultry carcasses in the UK

BackgroundCurrent occupational and public health guidance does not distinguish between rendering plant workers and cullers/poultry workers in terms of infection risk in their respective roles during highly pathogenic avian influenza poultry outbreaks. We describe an operational approach to human health risk assessment decision making at a large rendering plant processing poultry carcasses stemming from two separate highly pathogenic avian influenza A (H5N1) outbreaks in England during 2007.MethodsDuring the first incident a uniform approach assigned equal exposure risk to all rendering workers in or near the production line. A task based exposure assessment approach was adopted during the second incident based on a hierarchy of occupational activities and potential for infection exposure. Workers assessed as being at risk of infection were offered personal protective equipment; pre-exposure antiviral prophylaxis; seasonal influenza immunisation; hygiene advice; and health monitoring. A repeat survey design was employed to compare the two risk assessment approaches, with allocation of antiviral prophylaxis as the main outcome variable.ResultsTask based exposure assessment during the second incident reduced the number of workers assessed at risk of infection from 72 to 55 (24% reduction) when compared to the first incident. No cases of influenza like illness were reported in workers during both incidents.ConclusionsTask based exposure assessment informs a proportionate public health response in rendering plant workers during highly pathogenic avian influenza H5N1 outbreaks, and reduces reliance on extensive antiviral prophylaxis.

Spatio–temporal analyses of highly pathogenic avian influenza H5N1 outbreaks in the Mekong River Delta, Vietnam, 2009

This paper presents the results of spatio–temporal analyses and epidemic modelling of HPAI H5N1 outbreaks that occurred in four provinces of the Mekong River Delta, Vietnam between January and March 2009. Significant spatio–temporal interaction of disease risk was observed within a distance of 10 km and 12 days following the detected onset of clinical signs. We estimate that the household-to-household infection rate within a commune was approximately 50 times greater than the household-to-household infection rate between communes. Our findings show that the predominant mechanism of infection transfer was local spread. A comparison of disease control procedures and veterinary capacity in communes with relatively high and low infection rates should help to identify procedures essential for effective outbreak management in this area of Vietnam.

Risk factors and clusters of Highly Pathogenic Avian Influenza H5N1 outbreaks in Bangladesh

Between March 2007 and July 2009, 325 Highly Pathogenic Avian Influenza (HPAI, subtype H5N1) outbreaks in poultry were reported in 154 out of a total of 486 sub-districts in Bangladesh. This study analyzed the temporal and spatial patterns of HPAI H5N1 outbreaks and quantified the relationship between several spatial risk factors and HPAI outbreaks in sub-districts in Bangladesh. We assessed spatial autocorrelation and spatial dependence, and identified clustering sub-districts with disease statistically similar to or dissimilar from their neighbors. Three significant risk factors associated to HPAI H5N1 virus outbreaks were identified; the quadratic log-transformation of human population density [humans per square kilometer, P = 0.01, OR 1.15 (95% CI: 1.03–1.28)], the log-transformation of the total commercial poultry population [number of commercial poultry per sub-district, P < 0.002, OR 1.40 (95% CI: 1.12–1.74)], and the number of roads per sub-district [ P = 0.02, OR 1.07 (95% CI: 1.01–1.14)]. The distinct clusters of HPAI outbreaks and risk factors identified could assist the Government of Bangladesh to target surveillance and to concentrate response efforts in areas where disease is likely to occur. Concentrating response efforts may help to combat HPAI more effectively, reducing the environmental viral load and so reducing the number of disease incidents.

First Year of the Highly Pathogenic Avian Influenza H5N1 Outbreak in Egypt: Rapid Antigenic/Molecular Diagnosis and Virus Isolation

First Year of the Highly Pathogenic Avian Influenza H5N1 Outbreak in Egypt: Rapid Antigenic/Molecular Diagnosis and Virus Isolation

Economic Effect of the Highly Pathogenic Avian Influenza H5N1 Outbreaks Among Turkey Producers, 2005–06, Turkey

This research assessed the direct economic effects of the 2005-06 HPAI outbreaks on contracted turkey producers in Turkey in 2007. The data were obtained from 71 randomly selected, contracted turkey farms (producing 23% of the national turkey meat in Turkey in 2005) from five provinces for four integrated firms, which account for 67% of the national turkey production. Each farm was visited once for an oral interview conducted by the authors in 2007, using a questionnaire survey. The financial data before and after highly pathogenic avian influenza (HPAI) H5N1 outbreak periods were obtained from available financial records. Changes in production and economics parameters before and after the HPAI H5N1 outbreak periods were compared. In the analyses, the "before the HPAI H5N1 outbreak" period was stated as October 1, 2004, to May 31, 2005, whereas the "after the HPAI H5N1 outbreak" period was stated as the 8-mo between October 1, 2005, and May 31, 2006. The research revealed that changes in the technical parameters (number of hired labor, feed conversion rate, mortality rate, and the length of fattening period) were not found to be statistically significant at P > 0.05. However, there were severe effects of the HPAI H5N1 outbreaks on the economic parameters of the turkey production. The contracted turkey producers lost on average 0.9 cycles (38%) of production, and their management fees were reduced by 9.3% in the 8 mo after the outbreaks. As a result, the production level and enterprise income declined by 36% and 39%, respectively. About 93% of the producers did not do any other supplementary work during the idle production period; 59% of the producers had to use on average 4970TL (US$3200) from their personnel saving during the HPAI H5N1 outbreaks. About 62% of the producers stated that they had been considering expanding their businesses, but suspended the idea because of the outbreak, and 80% of the producers increased the biosecurity measures after the outbreaks. The futures of the contracted turkey producers are fully dependent on those of the integrated firms. Any negative effects on the latter appear to be directly transferred to the former. However, the government neglected contracted producers in the HPAI compensation programs.

Changes in Poultry Handling Behavior and Poultry Mortality Reporting among Rural Cambodians in Areas Affected by HPAI/H5N1

BackgroundSince 2004, 21 highly pathogenic avian influenza H5N1 outbreaks in domestic poultry and eight human cases have been confirmed in Cambodia. As a result, a large number of avian influenza education campaigns have been ongoing in provinces in which H5N1outbreaks have occurred in humans and/or domestic poultry.Methodology/Principal FindingsData were collected from 1,252 adults >15 years old living in two southern provinces in Cambodia where H5N1 has been confirmed in domestic poultry and human populations using two cross-sectional surveys conducted in January 2006 and in November/December 2007. Poultry handling behaviors, poultry mortality occurrence and self-reported notification of suspect H5N1 poultry cases to animal health officials in these two surveys were evaluated. Our results demonstrate that although some at risk practices have declined since the first study, risky contact with poultry is still frequent. Improved rates of reporting poultry mortality were observed overall, but reporting to trained village animal health workers decreased by approximately 50%.Conclusions/SignificanceAlthough some improvements in human behavior have occurred, there are still areas—particularly with respect to the handling of poultry among children and the proper treatment of poultry and the surrounding household environment—that need to be addressed in public health campaigns. Though there were some differences in the sampling methods of the 2006 and 2007 surveys, our results illustrate the potential to induce considerable, potentially very relevant, behavioral changes over a short period of time.

Identifying spatio-temporal patterns of transboundary disease spread: examples using avian influenza H5N1 outbreaks

Characterizing spatio-temporal patterns among epidemics in which the mechanism of spread is uncertain is important for generating disease spread hypotheses, which may in turn inform disease control and prevention strategies. Using a dataset representing three phases of highly pathogenic avian influenza H5N1 outbreaks in village poultry in Romania, 2005–2006, spatio-temporal patterns were characterized. We first fit a set of hierarchical Bayesian models that quantified changes in the spatio-temporal relative risk for each of the 23 affected counties. We then modeled spatial synchrony in each of the three epidemic phases using non-parametric covariance functions and Thin Plate Spline regression models. We found clear differences in the spatio-temporal patterns among the epidemic phases (local versus regional correlated processes), which may indicate differing spread mechanisms (for example wild bird versus human-mediated). Elucidating these patterns allowed us to postulate that a shift in the primary mechanism of disease spread may have taken place between the second and third phases of this epidemic. Information generated by such analyses could assist affected countries in determining the most appropriate control programs to implement, and to allocate appropriate resources to preventing contact between domestic poultry and wild birds versus enforcing bans on poultry movements and quarantine. The methods used in this study could be applied in many different situations to analyze transboundary disease data in which only location and time of occurrence data are reported.

Sero-Epidemiological Results in the Human Population Exposed to Highly Pathogenic Avian Influenza H5N1 Outbreak in a Large Poultry Farm in the East of England

In February 2007, the presence of highly pathogenic avian influenza H5N1 of Eurasian lineage (Clade 2.2) was confirmed in turkeys at one of 22 sheds of a large poultry farm located in the east of England. A multi-agency Incident Management Team assessed the risk to human health and instituted appropriate control measures. This is a summary of results of investigation into associations between risk-factors and outcomes as described below. A total of 482 individuals received chemoprophylaxis with Oseltamivir, of which 187 (39%) consented to blood testing for evidence of infection with H5N1 at 8—10 weeks following exposure. A supervised questionnaire was administered at the same time to investigate associations between exposure, occupational and demographic variables, and outcome. After excluding people with no exposure, 162 were available for analysis. 29 (18%) reported one or more symptoms of influenza like illness (ILI) experienced only after exposure, of whom 21 had received Oseltamivir before possible exposure to H5N1. 157/162 (97%) reported 90—100% compliance with taking prescribed Oseltamivir, while 73% reported total compliance with personal protective equipment (PPE). 141 (87%) individuals received seasonal influenza vaccination, of whom 16 (10%) had received the vaccination prior to the incident. There was no evidence of sero-conversion to H5. Multivariable logistic regression modeling failed to find any statistically significant associations between abovementioned variables and ILI symptoms at 5% significance level. However, there was a suggestion that ‘workers with no specific occupational activity’ may be at elevated risk (OR = 3.93; 95%CI: 1.00—15.54; p = 0.059). Interestingly, amongst others, there was no statistically significant association between ‘always wear complete PPE’ nor ‘always wear FFP2 or FFP3 respirator’ (both binary variables), and symptom development (p = 0.95, 0.9 respectively). The public health response included the largest ever mass provision of Oseltamivir for ‘at-risk’ individuals in the UK, the assessment framework for which needs review.