Methods: In a prospective birth cohort study, nasal mucous samples were collected from farm and non-farm children at scheduled intervals (2, 9, 12, and 18 months of age), and during respiratory illnesses (at least mild symptoms≥2 days). Farm children were born to women who reside or work on cattle or dairy farms. Infection rates were determined by viral detection (multiplex PCR) at scheduled visits.
Results: 210 nasal specimens from 28 farm children and 24 non-farm children were analyzed. Mean length of time for follow-up was 10.1 months for farm children and 10.3 months for non-farm children. Viral detection rates were similar in farm and non-farm children at scheduled visits (2 months: 8/28 vs. 9/24, p=0.49; 9 months: 7/15 vs. 8/15, p=0.72; 12 months: 3/11 vs. 4/6, p=0.11; 18 months: 1/3 vs. 1/3, p=1.00). Non-farm children had increased numbers of viral respiratory illnesses/child/year (mean 2.69, 95% CI, 1.79-4.04) compared to farm children (mean 1.45, 95% CI 0.94-2.25), a 1.85-fold increase (95% CI 1.02-3.35, p=0.04).
Conclusions: Despite similar rates of viral infection, farm versus non-farm children have significantly decreased rates of respiratory viral illnesses. Early-life farming exposures may impact anti-viral immune maturation.