Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) colonisation and infection among livestock workers and veterinarians: a systematic review and meta-analysis

ObjectivesMethicillin-resistant Staphylococcus aureus (MRSA) is an increasing public health concern worldwide. The objective of this study was to calculate a summary odds ratio (OR) of livestock-associated MRSA colonisation and infection in humans, and to determine specific risk factors in livestock production contributing to MRSA colonisation.MethodsWe screened PubMed and Embase for studies published from 2005 to 2019 inclusive, reporting livestock-associated (LA)-MRSA colonisation and infection among livestock workers/veterinarians, their families, and community members not regularly exposed to livestock. The primary outcome of interest was the OR of LA-MRSA colonisation comparing exposed and control groups. Quality was assessed according to the Newcastle-Ottawa quality assessment scale. A meta-analysis using a random-effects model was conducted to calculate a pooled OR. The heterogeneity in the meta-analysis was assessed using the I² method, and publication bias was evaluated using funnel plots.ResultsA total of 3490 studies were identified by the search, with 37 studies including 53 matched exposed-control groups and 14 038 participants eligible for the meta-analysis. The pooled OR for LA-MRSA among livestock workers and veterinarians is 9.80 (95% CI 6.89 to 13.95; p=0.000; I2=73.4), with no significant publication bias (Egger’s p=0.66). The OR for swine workers was highest at 15.41 (95% CI 9.24 to 25.69), followed by cattle workers (11.62, 95% CI 4.60 to 29.36), veterinarians (7.63, 95% CI 3.10 to 18.74), horse workers (7.45, 95% CI 2.39 to 23.25), livestock workers (5.86, 95% CI 1.14 to 30.16), poultry workers (5.70, 95% CI 1.70 19.11), and industrial slaughterhouse workers (4.69, 95% CI 1.10 to 20.0).ConclusionsLivestock workers, particularly swine farmers, are at significantly higher risk for LA-MRSA colonisation and subsequent infection. These results support the need for preventive practices to reduce LA-MRSA risk among those who handle and treat livestock.Trial registration numberCRD42019120403.

High Risk of Influenza Virus Infection Among Swine Workers: Examining a Dynamic Cohort in China

Background China is thought to be a hotspot for zoonotic influenza virus emergence, yet there have been few prospective studies examining the occupational risks of such infections. Methods We present the first 2 years of data collected from a 5-year, prospective, cohort study of swine-exposed and -unexposed participants at 6 swine farms in China. We conducted serological and virological surveillance to examine evidence for swine influenza A virus infection in humans. Results Of the 658 participants (521 swine-exposed and 137 swine-unexposed), 207 (31.5%) seroconverted against at least 1 swine influenza virus subtype (swine H1N1 or H3N2). Swine-exposed participants’ microneutralization titers, especially those enrolled at confined animal feeding operations (CAFOs), were higher against the swine H1N1 virus than were other participants at 12 and 24 months. Despite elevated titers, among the 187 study subjects for whom we had complete follow-up, participants working at swine CAFOs had significantly greater odds of seroconverting against both the swine H1N1 (odds ratio [OR] 19.16, 95% confidence interval [CI] 3.55–358.65) and swine H3N2 (OR 2.97, 95% CI 1.16–8.01) viruses, compared to unexposed and non-CAFO swine workers with less intense swine exposure. Conclusions While some of the observed increased risk against swine viruses may have been explained by exposure to human influenza strains, study data suggest that even with elevated preexisting antibodies, swine-exposed workers were at high risk of infection with enzootic swine influenza A viruses.

Bioaerosols Play a Major Role in the Nasopharyngeal Microbiota Content in Agricultural Environment

Background: Bioaerosols are a major concern for public health and sampling for exposure assessment purposes is challenging. The nasopharyngeal region could be a potent carrier of long-term bioaerosol exposure agents. This study aimed to evaluate the correlation between nasopharyngeal bacterial flora of swine workers and the swine barns bioaerosol biodiversity. Methods: Air samples from eight swine barns as well as nasopharyngeal swabs from pig workers (n = 25) and from a non-exposed control group (n = 29) were sequenced using 16S rRNA gene high-throughput sequencing. Wastewater treatment plants were used as the industrial, low-dust, non-agricultural environment control to validate the microbial link between the bioaerosol content (air) and the nasopharynxes of workers. Results: A multivariate analysis showed air samples and nasopharyngeal flora of pig workers cluster together, compared to the non-exposed control group. The significance was confirmed with the PERMANOVA statistical test (p-value of 0.0001). Unlike the farm environment, nasopharynx samples from wastewater workers did not cluster with air samples from wastewater treatment plants. The difference in the microbial community of nasopharynx of swine workers and a control group suggest that swine workers are carriers of germs found in bioaerosols. Conclusion: Nasopharynx sampling and microbiota could be used as a proxy of air sampling for exposure assessment studies or for the determination of exposure markers in highly contaminated agricultural environments.

Occupational Exposure Risk for Swine Workers in Confined Housing Facilities

Extended exposure of swine barn workers to noise and airborne contaminants has been reported to be associated with various health problems. In this study, the actual exposure of workers to respirable dust, gases (ammonia and hydrogen sulfide), and noise in swine production operations was monitored in order to determine the contribution of specific activities in the barn to potential adverse health impacts to swine workers. Selected workers in a swine barn facility were outfitted with a personal monitoring system that included a respirable dust sampler, ammonia (NH3) and hydrogen sulfide (H2S) gas monitors, and a noise dosimeter as they performed their regular duties during their workday. From a total of 50 monitoring days spanning winter and summer months, results showed that the occupational exposure of swine workers to respirable dust, NH3, H2S, and noise while performing their daily assigned tasks was generally below the respective time-weighted average exposure limits for each hazard. However, a number of tasks showed high likelihood for elevated occupational exposure risk. Respirable dust concentrations exceeded the time-weighted average limit of 3 mg m-3 while feeding and weighing pigs. These activities also exceeded the short-term exposure limit (35 ppm) for NH3. Dangerous levels of H2S were generated when draining manure from manure collection pits in the production rooms. Noise levels exceeded the recommended 15 min exposure limit (100 dBA) when weighing and loading pigs for market. The occupational exposure risks for workers to barn contaminants can be reduced through measures that control the generation of contaminants at their source, by removing generated contaminants from the work environment, as well as by outfitting the workers with protective devices that prevent personal exposure to contaminants. Keywords: Ammonia, Barn worker, Dust, Hydrogen sulfide, Noise, Occupational exposure, Risk, Swine.

Hepatitis E virus infection in North Italy: high seroprevalence in swine herds and increased risk for swine workers

SUMMARYWe determined the hepatitis E virus (HEV) seroprevalence and detection rate in commercial swine herds in Italy's utmost pig-rich area, and assessed HEV seropositivity risk in humans as a function of occupational exposure to pigs, diet, foreign travel, medical history and hunting activities. During 2011–2014, 2700 sera from 300 swine herds were tested for anti-HEV IgG. HEV RNA was searched in 959 faecal pools from HEV-seropositive herds and in liver/bile/muscle samples from 179 pigs from HEV-positive herds. A cohort study of HEV seropositivity in swine workers (n = 149) was also performed using two comparison groups of people unexposed to swine: omnivores (n = 121) and vegetarians/vegans (n = 115). Herd-level seroprevalence was 75·6% and was highest in farrow-to-feeder herds (81·6%). Twenty-six out of 105 (24·8%) herds had HEV-positive faecal samples (25 HEV-3, one HEV-4). Only one bile sample tested positive. HEV seropositivity was 12·3% in swine workers, 0·9% in omnivores and 3·0% in vegetarians/vegans. Factors significantly associated with HEV seropositivity were occupational exposure to pigs, travel to Africa and increased swine workers’ age. We concluded that HEV is widespread in Italian swine herds and HEV-4 circulation is alarming given its pathogenicity, with those occupationally exposed to pigs being at increased risk of HEV seropositivity.

Evidence for Cross-species Influenza A Virus Transmission within Swine Farms, China

Background Our understanding of the risk factors for swine influenza A virus transmission between humans and pigs is sparse. Methods Beginning in 2015, we used a One Health approach and serial sampling to prospectively study 299 swine workers and 100 controls, their 9000 pigs, and six pig farm environments in China for influenza A viruses (IAVs) using molecular, culture, and immunological techniques. Study subjects were closely monitored for influenza-like illness (ILI) events. Results Upon enrollment, swine workers had higher serum neutralizing antibody titers against swine H1N1 and higher nasal wash total IgA and specific IgA titers against swine H1N1 and H3N2 viruses. Over a period of 12 months, IAVs were detected by qRT-PCR in 52 (12%) of 432 environmental swabs, 275 (7.6%) of 3600 pig oral secretion, 25 (5.8%) of 432 water, 24 (5.5%) of 432 aerosol, and 20 (4.6%) of 432 fecal-slurry specimens. Five (15.6%) of 32 subjects with ILI events had nasopharyngeal swab specimens that were positive for IAV and 17 (53%) demonstrated 4-fold rises in neutralization titers against a swine virus. Reassorted Eurasian avian-like swine H1N1, pdm09(H1N1)-like virus, and swine-like H3N2 viruses were identified in pig farms. The H1N1 viruses were nearly genetically identical with the human H1N1 viruses isolated from the subjects with ILI. Conclusion There was considerable evidence of A(H1N1)pdm09-like, swine H1N1 and swine H3N2 viruses reassorting and circulating within the pig farms and crossing species. These data suggest that stronger surveillance for novel influenza virus emergence within swine farms is imperative. Disclosures All authors: No reported disclosures.