In-silico characterization of the relationship between the Porcine reproductive and respiratory syndrome virus prevalence at the piglet and litter levels in a farrowing room

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Osemeke, Onyekachukwu H.
de Freitas Costa, Eduardo
Weide, Vinicius
Jayaraman, Swaminathan
Silva, Gustavo S.
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Springer Nature
Linhares, Daniel
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Veterinary Diagnostic and Production Animal Medicine
The mission of VDPAM is to educate current and future food animal veterinarians, population medicine scientists and stakeholders by increasing our understanding of issues that impact the health, productivity and well-being of food and fiber producing animals; developing innovative solutions for animal health and food safety; and providing the highest quality, most comprehensive clinical practice and diagnostic services. Our department is made up of highly trained specialists who span a wide range of veterinary disciplines and species interests. We have faculty of all ranks with expertise in diagnostics, medicine, surgery, pathology, microbiology, epidemiology, public health, and production medicine. Most have earned certification from specialty boards. Dozens of additional scientists and laboratory technicians support the research and service components of our department.
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Background: Family oral fluids (FOF) sampling has been described as a sampling technique where a rope is exposed to sows and respective suckling litters and thereafter wrung to obtain fluids. PCR-based testing of FOF reveals presence of PRRS virus RNA only at the litter level, as opposed to conventional individual-animal-based sampling methods that demonstrate PRRSV RNA at the piglet level. The relationship between the PRRSV prevalence at the individual piglet level and at the litter level in a farrowing room has not been previously characterized. Using Monte Carlo simulations and data from a previous study, the relationship between the proportion of PRRSV-positive (viremic) pigs in the farrowing room, the proportion of litters in the farrowing room with at least one viremic pig, and the likely proportion of litters to be positive by a FOF RT-rtPCR test in a farrowing room was characterized, taking into account the spatial distribution (homogeneity) of viremic pigs within farrowing rooms. Results: There was a linear relationship between piglet-level- and litter-level prevalence, where the latter was always larger than the former. When the piglet-level prevalence was 1%, 5%, 10%, 20%, and 50%, the true-litter level prevalence was 5.36%, 8.93%, 14.29%, 23.21%, and 53.57%, respectively. The corresponding apparent-litter prevalence by FOF was 2.06%, 6.48%, 11.25%, 21.60%, and 51.56%, respectively. Conclusion: This study provides matching prevalence estimates to help guide sample size calculations. It also provides a framework to estimate the likely proportion of viremic pigs, given the PRRSV RT-rtPCR positivity rate of FOF samples submitted from a farrowing room.
This article is published as Osemeke, Onyekachukwu H., Eduardo de Freitas Costa, Vinicius Weide, Swaminathan Jayaraman, Gustavo S. Silva, and Daniel CL Linhares. "In-silico characterization of the relationship between the Porcine reproductive and respiratory syndrome virus prevalence at the piglet and litter levels in a farrowing room." Porcine Health Management 9, no. 1 (2023): 1-9. DOI: 10.1186/s40813-023-00309-x. Copyright 2023 The Author(s). Attribution 4.0 International (CC BY 4.0). Posted with permission.