The waters used in agricultural irrigation systems could act as an environmental reservoir for the bacteria responsible for legionellosis, as highlighted by a research developed by a team from the Carlos III Health Institute (ISCIII).
The study, conducted by specialists from the National Reference Laboratory for Legionellosis of the National Center for Microbiology (CNM) and published in the scientific journal 'Journal of Environmental Management', has verified that water spraying devices function as emission points for aerosols capable of dispersing the bacteria Legionella pneumophila.
For this reason, the risk of infection associated with the inhalation of such aerosols has been evaluated, given that this bacteria causes most cases of legionellosis, an infectious pathology that presents with pneumonia and that, in the most severe cases, can cause the patient's death. The work concludes that irrigation systems generate contaminated aerosols that, under certain meteorological conditions, can travel to nearby urban areas, increasing the probability of contagion.
A little-considered exposure focus
"The integration of microbiological, genomic, epidemiological, and meteorological data points to sprinkler irrigation systems as a possible source of exposure that had not been previously considered," stated the authors and members of the CNM, Fernando González Camacho and Juana González Rubio, who added that "the research shows the high microbial diversity present in these agricultural infrastructures and the presence of different potentially pathogenic microorganisms."
In their view, this situation "raises the need to pay greater attention to these systems from the perspective of environmental surveillance and public health." To deepen this hypothesis, the detection of Legionella pneumophila has been accompanied by a retrospective review of an outbreak of legionellosis recorded in 2015 in the same area where the bacteria has now been identified, a rural region in the northeast of Spain whose environmental origin had not been clarified at that time.
With the collaboration of the National Center for Epidemiology (CNE) of ISCIII and the participation of the Institute of Integrative Biology of Systems —a center jointly promoted by the Higher Council for Scientific Research (CSIC) and the Universitat de València—, the analysis concludes that the genetic study of the variants of the bacteria detected in ponds and irrigation ditches shows that they share a common origin with the variant isolated in patients affected by that outbreak.
Overall, and according to the researchers, the findings "allow for new avenues of research to be opened, by identifying a possible environmental focus that has been little considered so far in the context of legionellosis in rural environments and the prevention plans for this disease." "In addition, they confirm the importance of integrating microbiology, epidemiology, and environmental conditions to facilitate the prevention and identification of possible outbreaks in these environments, and to better understand the relationship between the environment, pathogenic organisms, and health," they concluded.