Prevalence of Bovine Leukemia Virus (BLV) and Bovine Adenovirus (BAdV) genomes among air and surface samples in dairy production

Abstract

We aimed to assess the occurrence of bovine viruses (bovine leukemia virus–BLV and bovine adenovirus–BAdV) at workplaces in traditional dairies and to evaluate the potential role of airborne and surface contamination in spreading of these viruses derived from raw milk. The total amount of 122 samples—including 37 air (bioaerosol), 40 surface, and 45 milk samples—were checked for the presence of BLV and BAdV genomes using RT-qPCR/qPCR method. The study showed that the viruses were present in 7 air (among them 71.4% were BLV-positive and 28.6% were BAdV-positive), 14 surface (among them 85.7% were BLV-positive and 14.3% were BAdV-positive), and 34 milk (all were BLV-positive only) samples. Statistical analysis revealed that both the air and surfaces in studied occupational environment were more frequently contaminated with BLV than with BAdV (Chi-square test: p = 0.002, Fisher’s Exact test: p = 0.002). Kruskal-Wallis tests showed significant differences in BLV genome concentrations in the air (p = 0.045) as well as in BLV and BAdV genome concentrations on surfaces (p = 0.005 and p = 0.040, respectively) between studied processing areas. In units of genome copies (gc) per area, the highest concentrations of BLV and BAdV genomes in the air (9.8 × 10¹ ± 1.14 × 10² gc/m³ and 5.4 × 10¹ ± 9.1 × 10¹ gc/m³, respectively) and on surfaces (9.83 × 10² ± 7.41 × 10² gc/100cm² and 2.30 × 10² ± 3.8 × 10² gc/100cm², respectively) were observed in milk reception area. The air and surfaces of pre-production zones were also significantly more contaminated with BAdV genomes compared to production areas (Mann-Whitney test: p = 0.039 and p = 0.029, respectively). This study showed that dairy workers may be exposed to bovine viruses through the inhalation of bioaerosols and contact with contaminated surfaces. To reduce the probability of virus transmission from the raw milk to humans, efficient surface cleaning procedures degrading viral particles should be introduced and the use of personal protection equipment, especially within pre-production zones, should be required. As the raw milk may be a source of bovine viruses, the development of strategies for both the control and eradication of BLV and BAdV among cattle seems to be also urgently needed.

Keywords:

• Bioaerosol
• bovine adenovirus
• bovine leukemia virus
• dairy
• PCR
• surface

Funding

This paper has been based on the results of a research task carried out within the scope of the fourth stage of the National Program “Improvement of safety and working conditions” partly supported in 2017–2019—within the scope of research and development—by the Ministry of Science and Higher Education/National Center for Research and Development. The Central Institute for Labour Protection–National Research Institute is the Program’s main coordinator (Project no.: II.N.16).