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A large outbreak of giardiasis in a municipality of the Bologna province, north-eastern Italy, November 2018 to April 2019

  • Resi, Davide1
  • Varani, Stefania2, 3
  • Sannella, Anna Rosa4
  • De Pascali, Alessandra M2
  • Ortalli, Margherita3
  • Liguori, Giovanna2, 3
  • Benvenuti, Marco3
  • Re, Maria C2, 3
  • Pirani, Roberta1
  • Prete, Luciana5
  • Mazzetti, Claudia5
  • Musti, Muriel6
  • Pizzi, Lorenzo6
  • Sanna, Tiziana1
  • Cacciò, Simone M4
  • 1 Unit of Hygiene and Public Health, Department of Public Health, Bologna, Italy
  • 2 Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Italy
  • 3 Unit of Microbiology, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy
  • 4 Unit of Foodborne and Neglected Parasites, Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy
  • 5 Unit of Nutrition, Diet and Lifestyle, Department of Public Health, Bologna, Italy
  • 6 Unit of Epidemiology, Health Promotion and Risk Communication, Department of Public Health, Bologna, Italy
Published Article
European Centre for Disease Control and Prevention (ECDC)
Publication Date
Sep 02, 2021
DOI: 10.2807/1560-7917.ES.2021.26.35.2001331
PMID: 34477055
PMCID: PMC8414958
PubMed Central
  • Outbreaks


Giardiasis, the disease caused by the flagellate Giardia duodenalis (syn. G.lamblia, G. intestinalis ), is the most commonly reported among the five food- and waterborne parasitic diseases under mandatory surveillance in 24 EU countries. From November 2018 to April 2019, an outbreak of giardiasis occurred in a municipality of the Bologna province, in north-eastern Italy. Microscopy and immunochromatography identified cysts and antigens, respectively, of the parasite in stool samples of 228 individuals. Molecular typing of 136 stool samples revealed a vast predominance (95%) of G. duodenalis assemblage B. Investigations into potential sources indicated tap water as the most likely vehicle of infection, although cysts were not detected in water samples. Control measures mostly aimed at preventing secondary transmission by informing citizens about the outbreak, and by treatment of patients with anti-parasitic drugs. This is the first documented human outbreak of giardiasis in Italy; its investigation has highlighted the difficulties in the timely detection and management of this parasite, which is often overlooked as a cause of human gastroenteritis. The long and variable incubation time, absence of specific symptoms and a general lack of awareness about this pathogen contributed to delay in diagnosis.

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