No evidence of infection with avian influenza viruses among US poultry workers in the Delmarva Peninsula, Maryland and Virginia, USA

The Multifaceted Zoonotic Risk of H9N2 Avian Influenza

Poultry-adapted H9N2 avian influenza viruses (AIVs) are commonly found in many countries in Asia, the Middle East, Africa, and Europe, and although classified as low pathogenic viruses, they are an economically important disease. Besides the importance of the disease in the poultry industry, some H9N2 AIVs are also known to be zoonotic. The disease in humans appears to cause primarily a mild upper respiratory disease, and doesn't cause or only rarely causes the severe pneumonia often seen with other zoonotic AIVs like H5N1 or H7N9. Serologic studies in humans, particularly in occupationally exposed workers, show a large number of people with antibodies to H9N2, suggesting infection is commonly occurring. Of the four defined H9N2 poultry lineages, only two lineages, the G1 and the Y280 lineages, are associated with human infections. Almost all of the viruses from humans have a leucine at position 226 (H3 numbering) of the hemagglutinin associated with a higher affinity of binding with α2,6 sialic acid, the host cell receptor most commonly found on glycoproteins in the human upper respiratory tract. For unknown reasons there has also been a shift in recent years of poultry viruses in the G1 and Y280 lineages to also having leucine instead of glutamine, the amino acid found in most avian viruses, at position 226. The G1 and Y280 poultry lineages because of their known ability to infect humans, the high prevalence of the virus in poultry in endemic countries, the lack of antibody in most humans, and the shift of poultry viruses to more human-like receptor binding makes these viruses a human pandemic threat. Increased efforts for control of the virus, including through effective vaccine use in poultry, is warranted for both poultry and public health goals.

Review of Nonfoodborne Zoonotic and Potentially Zoonotic Poultry Diseases

Emerging and re-emerging diseases are continuously diagnosed in poultry species. A few of these diseases are known to cross the species barrier, thus posing a public health risk and an economic burden. We identified and synthesized global evidence for poultry nonfoodborne zoonoses to better understand these diseases in people who were exposed to different poultry-related characteristics (e.g., occupational or nonoccupational, operational types, poultry species, outbreak conditions, health status of flocks). This review builds on current knowledge on poultry zoonoses/potentially zoonotic agents transmitted via the nonfoodborne route. It also identifies research gaps and potential intervention points within the poultry industry to reduce zoonotic transmission by using various knowledge synthesis tools such as systematic review (SR) and qualitative (descriptive) and quantitative synthesis methods (i.e., meta-analysis). Overall, 1663 abstracts were screened and 156 relevant articles were selected for further review. Full articles (in English) were retrieved and critically appraised using routine SR methods. In total, eight known zoonotic diseases were reviewed: avian influenza (AI) virus (n = 85 articles), Newcastle disease virus (n = 8), West Nile virus (WNV, n = 2), avian Chlamydia (n = 24), Erysipelothrix rhusiopathiae (n = 3), methicillin-resistant Staphylococcus aureus (MRSA, n = 15), Ornithonyssus sylvarium (n = 4), and Microsporum gallinae (n = 3). In addition, articles on other viral poultry pathogens (n = 5) and poultry respiratory allergens derived from mites and fungi (n = 7) were reviewed. The level of investigations (e.g., exposure history, risk factor, clinical disease in epidemiologically linked poultry, molecular studies) to establish zoonotic linkages varied across disease agents and across studies. Based on the multiple outcome measures captured in this review, AI virus seems to be the poultry zoonotic pathogen that may have considerable and significant public health consequences; however, epidemiologic reports have only documented severe human cases clustered in Asia and not in North America. In contrast, avian Chlamydia and MRSA reports clustered mainly in Europe and less so in North America and other regions. Knowledge gaps in other zoonoses or other agents were identified, including potential direct (i.e., nonmosquito-borne) transmission of WNV from flocks to poultry workers, the public health and clinical significance of poultry-derived (livestock-associated) MRSA, the zoonotic significance of other viruses, and the role of poultry allergens in the pathophysiology of respiratory diseases of poultry workers. Across all pathogens reviewed, the use of personal protective equipment was commonly cited as the most important preventive measure to reduce the zoonotic spread of these diseases and the use of biosecurity measures to reduce horizontal transmission in flock populations. The studies also emphasized the need for flock monitoring and an integrated approach to prevention (i.e., veterinary-public health coordination with regard to diagnosis, and knowledge translation and education in the general population) to reduce zoonotic transmission.

Weighing serological evidence of human exposure to animal influenza viruses - a literature review

Assessing influenza A virus strains circulating in animals and their potential to cross the species barrier and cause human infections is important to improve human influenza surveillance and preparedness. We reviewed studies describing serological evidence of human exposure to animal influenza viruses. Comparing serological data is difficult due to a lack of standardisation in study designs and in laboratory methods used in published reports. Therefore, we designed a scoring system to assess and weigh specificity of obtained serology results in the selected articles. Many studies report reliable evidence of antibodies to swine influenza viruses among persons occupationally exposed to pigs. Most avian influenza studies target H5, H7 and H9 subtypes and most serological evidence of human exposure to avian influenza viruses is reported for these subtypes. Avian influenza studies receiving a low grade in this review often reported higher seroprevalences in humans compared with studies with a high grade. Official surveillance systems mainly focus on avian H5 and H7 viruses. Swine influenza viruses and avian subtypes other than H5 and H7 (emphasising H9) should be additionally included in official surveillance systems. Surveillance efforts should also be directed towards understudied geographical areas, such as Africa and South America.

Human-livestock contacts and their relationship to transmission of zoonotic pathogens, a systematic review of literature

BACKGROUND

Micro-organisms transmitted from vertebrate animals - including livestock - to humans account for an estimated 60% of human pathogens. Micro-organisms can be transmitted through inhalation, ingestion, via conjunctiva or physical contact. Close contact with animals is crucial for transmission. The role of intensity and type of contact patterns between livestock and humans for disease transmission is poorly understood. In this systematic review we aimed to summarise current knowledge regarding patterns of human-livestock contacts and their role in micro-organism transmission.

METHODS

We included peer-reviewed publications published between 1996 and 2014 in our systematic review if they reported on human-livestock contacts, human cases of livestock-related zoonotic diseases or serological epidemiology of zoonotic diseases in human samples. We extracted any information pertaining the type and intensity of human-livestock contacts and associated zoonoses.

RESULTS

1522 papers were identified, 75 were included: 7 reported on incidental zoonoses after brief animal-human contacts (e.g. farm visits), 10 on environmental exposures and 15 on zoonoses in developing countries where backyard livestock keeping is still customary. 43 studies reported zoonotic risks in different occupations. Occupations at risk included veterinarians, culling personnel, slaughterhouse workers and farmers. For culling personnel, more hours exposed to livestock resulted in more frequent occurrence of transmission. Slaughterhouse workers in contact with live animals were more often positive for zoonotic micro-organisms compared to co-workers only exposed to carcasses. Overall, little information was available about the actual mode of micro-organism transmission.

CONCLUSIONS

Little is known about the intensity and type of contact patterns between livestock and humans that result in micro-organism transmission. Studies performed in occupational settings provide some, but limited evidence of exposure response-like relationships for livestock-human contact and micro-organism transmission. Better understanding of contact patterns driving micro-organism transmission from animals to humans is needed to provide options for prevention and thus deserves more attention.

A Systematic Review and Meta-Analysis of the Seroprevalence of Influenza A(H9N2) Infection Among Humans

INTRODUCTION

Given that influenza A(H9N2) is recognized as a pandemic threat, we evaluated the overall burden of influenza A(H9N2) infections among avian-exposed human populations.

METHODS

We performed a systematic search of PubMed, AGRICOLA, and CAB Abstracts databases for literature published during 1997-2013. Studies reporting serological evidence of human influenza A(H9N2) infection among avian-exposed populations were included. We used a World Health Organization (WHO)-recommended case definition for serological evidence of infection based on results of hemagglutination inhibition (HI) and microneutralization (MN) assays. We calculated overall seroprevalence through a random effects meta-analysis model.

RESULTS

Seroprevalence data reported by the studies ranged from 1% to 43% (median, 9%) by HI, which was not significantly different from the seroprevalence estimated through the WHO-recommended case definition (median, 1.3%; range, 0.5%-42.6%). Reported seroprevalence by MN ranged from 0.6% to 9% (median, 2.7%), which was greater than the seroprevalence estimated through the WHO-recommended case definition (median, 0.3%; range, 0.1%-1.4%).

CONCLUSIONS

A small proportion of avian-exposed humans had evidence of influenza A(H9N2) infection. As the virus has a near global distribution in poultry, it seems likely that present surveillance efforts are missing mild or asymptomatic infections among avian-exposed persons. It seems prudent to closely monitor avian-exposed populations for influenza A(H9N2) infection to provide prepandemic warnings.

Evidence for H5 avian influenza infection in Zhejiang province, China, 2010-2012: a cross-sectional study

BACKGROUND

The first outbreak of H5N1 highly-pathogenic avian influenza (HPAI) virus associated with several human deaths occurred in 1997 in Hong-Kong, China. While H5N1 virus infection in poultry workers has been studied in some detail, little is known about the environmental risk factors of the H5 avian influenza virus infection in China.

METHODS

A cross-sectional study was performed to evaluate the environmental load of H5 viruses in poultry-contaminated environments and to explore potential risk factors associated with infection in poultry workers between October 2010 and March 2012. Serum and environmental samples were collected in Zhejiang province, China. The hemagglutination inhibition (HI) assay was used to analyze human sera for antibodies against H5N1 virus [A/Hubei/1/2010 (H5N1) and A/Anhui/1/2005 (H5N1)]. All participants were interviewed with a standardized questionnaire to collect information on exposure to poultry. H5 Avian influenza virus in the environmental samples was detected by real time RT-PCR.

RESULTS

One hundred and five of 3,453 environmental samples (3.0%) tested positive for H5 avian influenza virus. Fifty-five of 1,169 subjects (4.7%) tested seropositive for anti-H5N1 antibodies. A statistically significant difference in H5 virus detection rate was found among the different environments sampled (<0.001), with the highest showed in live bird markets (68.6%). Detection rate varied according to the source of samples, sewage (9.5%), drinking water (19.0%), feces (19.0%), cage surface (25.7%), and slaughtering chopping boards (15.2%), respectively. Direct or close contact with poultry (OR =5.20, 95% CI, 1.53-17.74) and breeding numerous poultry (OR =3.77, 95% CI, 1.72-8.73) were significantly associated with seroprevalence of antibodies to avian influenza virus A (H5N1).

CONCLUSIONS

The number of birds bred more than 1,000 and direct or close contact with poultry in the workplace or the environment would be a potential risk of H5N1 infection.

A national study of US bird banders for evidence of avian influenza virus infections

BACKGROUND

Previously we have found that Midwestern US wildlife biologists, poultry farmers, veterinarians, and duck hunters have had evidence of avian influenza virus infections (AIVs).

OBJECTIVES

We sought to evaluate a national sample of US bird banders for previous evidence of AIV infection.

STUDY DESIGN

Controlled, cross-sectional serological survey.

RESULTS

In 2009 and 2010 we enrolled 157 registered bird banders from 40 US states and compared their enrollment data and serological results with 78 adult age-group matched controls from Iowa. On average, the bird banders had 15 years of wild bird exposure, banded 20 days per year, worked chiefly in 1 of the 4 North American flyways, and banded 300 individual birds of 5 different species per season. While handling birds, only 15% of banders reported wearing gloves. Three bird banders and 1 control had evidence of previous infection (1 AIV each) with A/BWTE/Ohio/07/495762-6(H7N3), A/Ty/MN/38391-6/95(H9N2) or A/CK/NJ/7290-2/95(H11N3) by microneutralization assay. There was no evidence of previous infection with a representative sample of H4, H5, H6, H8, or H10 AIVs. Participants were followed for influenza-like-illness for a median of 7 months and 4 (3 bird banders) submitted self-collected eye, nasal, and throat influenza-like-illness swab specimens, 1 of which collected in November of 2009, yielded a pandemic H1N1 influenza A virus.

CONCLUSION

Despite reports of conjunctivitis and upper respiratory symptoms while bird banding, we found sparse evidence that US bird banders had infections with AIVs.