In a recent study posted to the medRxiv* preprint server, researchers measured severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) seroprevalence in industrial livestock operation (ILO) staff of North Carolina, United States (US), between February 2021 and July 2022.

Study: SARS-CoV-2 antibody prevalence amongst industrial livestock operation staff and nearby community residents, North Carolina, USA, 2021-2022. Image Credit: CROCOTHERY/Shutterstock

Background

North Carolina’s ILOs, especially processing facilities, emerged as centers of coronavirus disease 2019 (COVID-19) outbreaks within the spring of 2020. Nevertheless, confirmed COVID-19 cases underestimated true severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) seroprevalence. Yet, few studies pursued evidence of COVID-19-related health disparities by socioeconomic status and ethnicity in North Carolina, especially amongst rural, Black, and Hispanic communities.

Many individuals from these communities work in animal production, slaughtering, and processing facilities and suffer over 50% more injury and illness than all US staff. Taylor et al. estimated that ~8% of US COVID-19 cases through the summer of 2020 occurred amongst processing plant and agricultural staff.

North Carolina is the second-largest hog and fourth-largest poultry-producing US state; thus, people working in these facilities, their household members, and nearby communities are more susceptible to respiratory health problems and infectious diseases. Given the limited access to and availability of reverse transcription-polymerase chain response (RT-PCR) testing, SARS-CoV-2 antibody testing could prove a pretty alternative. It could help estimate COVID-19 infection rates, prevalence, and population immunity resulting from prior infection or vaccination, even amongst asymptomatic and mild cases. Moreover, SARS-CoV-2 antibodies are present in saliva, which is simpler to gather. Saliva might be readily self-collected at home and mailed to a testing lab.

In regards to the study

In the current study, researchers enrolled 279 individuals from 240 households in collaboration with Rural Empowerment Association for Community Help (REACH), a community group based in Duplin County, North Carolina. They used a multiplex immunoassay to measure their salivary immunoglobulins G (IgG) responses targeting SARS-CoV-2. The team individually measured IgG responses to SARS-CoV-2 nucleocapsid (N), receptor-binding domain (RBD), and spike (S) protein to know whether these responses were antibody- or infection-triggered. Not less than one adult from ILO group households worked as an industrial hog/poultry operation employee or at an animal rendering or meat packing facility. For comparisons, additionally they enrolled participants living nearby these facilities but having no occupational exposure to livestock (ILO neighbors or ILON) and participants from metropolitan areas of North Carolina (Metro).

Study findings

The study evaluation covered 80 participants in each cohort – ILO,  ILON, and Metro. Most participants in all groups were Black Americans. ILON participants were older; ~50% of ILO and ILON and 72.8% of Metro participants were female. In comparison with ILO and Metro participants, ILON participants reported not having health insurance (13.3% and eight.7% vs. 15.5%). Likewise, in comparison with ILO and ILON, more Metro participants had received primary COVID-19 vaccination and not less than one booster dose. (13.2% and 10.3% vs. 20.7%).

SARS-CoV-2-induced antibody prevalence amongst ILO staff and their household members was as high as 63% in comparison with participants with no household members working at ILO (45.6%). These findings highlight the next SARS-CoV-2 transmission amongst meatpacking facility staff and their nearby communities. Nevertheless, the authors didn’t observe elevated SARS-CoV-2 infection-induced IgG response of their study population.

The study population comprised barely 23 meatpacking staff but a comparatively large variety of Black participants in other high-COVID-19-risk jobs. Thus, COVID-19 seroprevalence was comparable between high ILO intensity regions and Metro region residents (42.9% and 48.7%). Also, over time case rates may need converged between these two areas. Intriguingly, although 51% of all study participants had SARS-CoV-2 infection-induced IgG, only 15.4% reported having tested COVID-19-positive. Although testing positive for infection-induced IgG, 68% of participants didn’t think that they had COVID-19, also underlining the importance of accessible RT-PCR testing for COVID-19.

The more-infectious SARS-CoV-2 Delta and Omicron variants spread in the summertime and winter of 2021, respectively. Thus, additionally it is significant that the median date of vaccination completion, including booster doses, was later for ILO in comparison with ILON and Metro participants. Moreover, by July 2022, the ILO, ILON, and Metro combined had lower primary COVID-19 vaccination rates (52%) vs. North Carolina (62.9%) and US residents (67.2%). The study results, thus, also highlight the urgent need for dismantling vaccination barriers, especially for ILO staff, their household members, and rural communities.

Living and dealing in closed, crowded conditions could increase exposure to SARS-CoV-2 from household members and coworkers. Thus, participants with multiple person per household bedroom had the next prevalence of SARS-CoV-2 infection-induced IgG. Also, it was higher amongst Hispanic/Latino and Black individuals than White Americans due to their occupational status disadvantages inside specific jobs.

Conclusions

The present study results add to reports of high COVID-19 case rates amongst meatpacking facility staff early within the pandemic by reporting that ILO staff and their families exhibited high rates of SARS-CoV-2 infection-induced IgG. The study results also evidenced health disparities in exposure to SARS-CoV-2 by socioeconomic position.

Indeed, there may be an urgent have to vaccinate ILO staff and their families as a priority because they’re at the next risk of contracting COVID-19 in comparison with the overall population and are similarly susceptible as staff in other high-COVID-19-risk occupations (e.g., healthcare staff).

*Necessary notice

medRxiv publishes preliminary scientific reports that aren’t peer-reviewed and, subsequently, shouldn’t be considered conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:

• Carolyn Marie Gigot, Nora Pisanic, Kate Kruczynski, Magdielis Gregory Rivera, Kristoffer Spicer, Kathleen M Kurowski, Pranay Randad, Kirsten Koehler, William Clarke, Phyla Holmes, Devon J Hall Jr., Devon Hall, Christopher D Heaney. (2022). SARS-CoV-2 antibody prevalence amongst industrial livestock operation staff and nearby community residents, North Carolina, USA, 2021-2022. medRxiv. doi: https://doi.org/10.1101/2022.10.31.22281764 https://www.medrxiv.org/content/10.1101/2022.10.31.22281764v1