Streptococcus equi subsp. zooepidemicus, which rarely causes disease in humans, was at the center of an outbreak that affected 37 patients between 2021 and 2022. Advanced analytical methods and multidisciplinarity were key in identifying the source of the infection and implementing preventive measures



Between November 2021 and May 2022, Italy experienced an outbreak of an infection caused by Streptococcus equi subsp. zooepidemicus (SEZ), which involved a total of 37 clinical cases in a central region of the country, resulting in the death of five patients due to meningitis. This is a very rare event caused by a bacterium that primarily affects horses and other animals such as cattle, pigs, goats, sheep, and dogs, but in some cases can also infect humans, causing various diseases including meningitis, sepsis, and arthritis.


In response to this emergency, which began with 18 cases, competent authorities established an interdisciplinary task force that involved physicians, veterinarians, epidemiologists, and microbiologists, with the Istituto Zooprofilattico Sperimentale of Teramo at the forefront. As reported in a scientific paper published in the journal Emerging Infectious Diseases, the coordinated research efforts led to the identification of 19 more individuals affected by the microorganism and to a rapid identification of the source of infection.


"SEZ," explains Alexandra Chiaverini, from the Department of Food Hygiene and Technology at the Istituto Zooprofilattico Sperimentale of Teramo, corresponding author of the study, "is a bacterium that can infect domestic animals and pets. Human infection, although rare, generally occurs through direct contact with infected animals or by consuming raw milk or unpasteurized dairy products derived from the same animals."


The identification of the microorganism in patients and in some unpasteurized dairy products, combined with genomic analysis, allowed for the close correlation between the pathogenic strains to be highlighted and, consequently, the precise tracing of the source of infection. At that point, the involved healthcare facilities were able to intervene rapidly by halting the potentially contaminated products and preventing further cases.


"It was," adds Chiaverini, "a very positive case of close collaboration between different structures and disciplines. Our Institute promptly intervened to support human medicine in what I would call a concrete example of 'One Health,' a global and interdisciplinary approach to a pathology."


The scientific paper also emphasizes the need to further investigate the situation of Streptococcus equi subsp. zooepidemicus at the national level. "The next objective," concludes the researcher, "will be to understand the possible risks associated with SEZ through a targeted surveillance program, in order to safeguard public health."


Alexandra Chiaverini
Alexandra Chiaverini


Bosica S, Chiaverini A, De Angelis ME, Petrini A, Averaimo D, Martino M, Rulli M, Saletti MA, Cantelmi MC, Ruggeri F, Lodi F, Calistri P, Cito F, Cammà C, Di Domenico M, Rinaldi A, Fazii P, Cedrone F, Di Martino G, Accorsi P, Morelli D, De Luca N, Pomilio F, Parruti G, Savini G. Severe Streptococcus equi Subspecies zooepidemicus Outbreak from Unpasteurized Dairy Product Consumption, Italy. Emerg Infect Dis. 2023 May;29(5):1020-1024.

doi: https://doi.org/10.3201/eid2905.221338


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