Outbreaks Open Access
Like 0


Giardiasis, the disease caused by the flagellate (syn. ), 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 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.


Article metrics loading...

Loading full text...

Full text loading...



  1. Cacciò SM, Lalle M, Svärd SG. Host specificity in the Giardia duodenalis species complex. Infect Genet Evol. 2018;66:335-45.  https://doi.org/10.1016/j.meegid.2017.12.001  PMID: 29225147 
  2. Ryan U, Cacciò SM. Zoonotic potential of Giardia. Int J Parasitol. 2013;43(12-13):943-56.  https://doi.org/10.1016/j.ijpara.2013.06.001  PMID: 23856595 
  3. Efstratiou A, Ongerth JE, Karanis P. Waterborne transmission of protozoan parasites: review of worldwide outbreaks - An update 2011-2016. Water Res. 2017;114:14-22.  https://doi.org/10.1016/j.watres.2017.01.036  PMID: 28214721 
  4. Guzman-Herrador B, Carlander A, Ethelberg S, Freiesleben de Blasio B, Kuusi M, Lund V, et al. Waterborne outbreaks in the Nordic countries, 1998 to 2012. Euro Surveill. 2015;20(24):21160.  https://doi.org/10.2807/1560-7917.ES2015.20.24.21160  PMID: 26111239 
  5. European Centre for Disease Prevention and Control (ECDC). Giardiasis (lambliasis) - ECDC Annual epidemiological report for 2017. Stockholm: ECDC; 2019. Available from: https://www.ecdc.europa.eu/en/publications-data/giardiasis-lambliasis-annual-epidemiological-report-2017
  6. European Food Safety Authority (EFSA). Manual for reporting of food-borne outbreaks in accordance with Directive 2003/99/EC from the year 2012. Supporting publication 2013:EN-410. Parma: EFSA; 2013. Available from: https://efsa.onlinelibrary.wiley.com/doi/abs/10.2903/sp.efsa.2013.EN-410
  7. European Commission (EC). Commission implementing decision (EU) 2018/945 of 22 June 2018 on the communicable diseases and related special health issues to be covered by epidemiological surveillance as well as relevant case definitions. Brussels: Official Journal of the European Union; 6.72018:L 170. Available from: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32018D0945&from=EN
  8. Heymann DL, editor. Control of communicable diseases manual. American Public Health Association. Washington D.C.: American Public Health Association, 2015: 235.
  9. Istituto Nazionale di Statistica (ISTAT). ISTAT water statistics, years 2018-2020. Rome: ISTAT; 2021. Available from: https://www.istat.it/it/files//2021/03/GMA2021_ENG.pdf
  10. Sadaka HA, Gaafar MR, Mady RF, Hezema NN. Evaluation of ImmunoCard STAT test and ELISA versus light microscopy in diagnosis of giardiasis and cryptosporidiosis. Parasitol Res. 2015;114(8):2853-63.  https://doi.org/10.1007/s00436-015-4486-z  PMID: 25924795 
  11. Lalle M, Pozio E, Capelli G, Bruschi F, Crotti D, Cacciò SM. Genetic heterogeneity at the beta-giardin locus among human and animal isolates of Giardiaduodenalis and identification of potentially zoonotic subgenotypes. Int J Parasitol. 2005;35(2):207-13.  https://doi.org/10.1016/j.ijpara.2004.10.022  PMID: 15710441 
  12. Verweij JJ, Blangé RA, Templeton K, Schinkel J, Brienen EA, van Rooyen MA, et al. Simultaneous detection of Entamoeba histolytica, Giardia lamblia, and Cryptosporidium parvum in fecal samples by using multiplex real-time PCR. J Clin Microbiol. 2004;42(3):1220-3.  https://doi.org/10.1128/JCM.42.3.1220-1223.2004  PMID: 15004079 
  13. International Organization for Standardization (ISO). Water quality – isolation and identification of Cryptosporidium oocysts and Giardia cysts from water. ISO 15553:2006. Geneva: ISO Central Secretariat; 2006. Available from: https://www.iso.org/standard/39804.html
  14. European Union (EU). Drinking Water Directive - Council directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption. Official Journal of the European Communities. Luxembourg: Publications office of the EU. 1998;L330:32-54. Available from: https://eur-lex.europa.eu/eli/dir/1998/83/2015-10-27
  15. Moreira NA, Bondelind M. Safe drinking water and waterborne outbreaks. J Water Health. 2017;15(1):83-96.  https://doi.org/10.2166/wh.2016.103  PMID: 28151442 
  16. Boarato-David E, Guimarães S, Cacciò SM. Giardia duodenalis. In: Rose JB and Jiménez-Cisneros B, (eds), Water and Sanitation for the 21st Century: Health and Microbiological Aspects of Excreta and Wastewater Management (Global Water Pathogen Project). (R. Fayer and W. Jakubowski (eds), Part 3: Specific Excreted Pathogens: Environmental and Epidemiology Aspects - Section 3: Protists), Michigan State University, E. Lansing, MI, UNESCO; 2017.  https://doi.org/10.14321/waterpathogens.35 
  17. Hamilton KA, Waso M, Reyneke B, Saeidi N, Levine A, Lalancette C, et al. Cryptosporidium and Giardia in wastewater and surface water environments. J Environ Qual. 2018;47(5):1006-23.  https://doi.org/10.2134/jeq2018.04.0132  PMID: 30272766 
  18. Robertson LJ, Hanevik K, Escobedo AA, Mørch K, Langeland N. Giardiasis--why do the symptoms sometimes never stop? Trends Parasitol. 2010;26(2):75-82.  https://doi.org/10.1016/j.pt.2009.11.010  PMID: 20056486 
  19. Lalle M, Hanevik K. Treatment-refractory giardiasis: challenges and solutions. Infect Drug Resist. 2018;11:1921-33.  https://doi.org/10.2147/IDR.S141468  PMID: 30498364 
  20. Tillett HE, de Louvois J, Wall PG. Surveillance of outbreaks of waterborne infectious disease: categorizing levels of evidence. Epidemiol Infect. 1998;120(1):37-42.  https://doi.org/10.1017/S0950268897008431  PMID: 9528816 
  21. Zajaczkowski P, Mazumdar S, Conaty S, Ellis JT, Fletcher-Lartey SM. Epidemiology and associated risk factors of giardiasis in a peri-urban setting in New South Wales Australia. Epidemiol Infect. 2018;28:1-9.  https://doi.org/10.1017/S0950268818002637  PMID: 30264685 
  22. Reses HE, Gargano JW, Liang JL, Cronquist A, Smith K, Collier SA, et al. Risk factors for sporadic Giardia infection in the USA: a case-control study in Colorado and Minnesota. Epidemiol Infect. 2018;146(9):1071-8.  https://doi.org/10.1017/S0950268818001073  PMID: 29739483 
  23. Stuart JM, Orr HJ, Warburton FG, Jeyakanth S, Pugh C, Morris I, et al. Risk factors for sporadic giardiasis: a case-control study in southwestern England. Emerg Infect Dis. 2003;9(2):229-33.  https://doi.org/10.3201/eid0902.010488  PMID: 12603995 
  24. Strand EA, Robertson LJ, Hanevik K, Alvsvåg JO, Mørch K, Langeland N. Sensitivity of a Giardia antigen test in persistent giardiasis following an extensive outbreak. Clin Microbiol Infect. 2008;14(11):1069-71.  https://doi.org/10.1111/j.1469-0691.2008.02078.x  PMID: 18808422 
  25. Prystajecky N, Tsui CK, Hsiao WW, Uyaguari-Diaz MI, Ho J, Tang P, et al. Giardia spp. are commonly found in mixed assemblages in surface water, as revealed by molecular and whole-genome characterization. Appl Environ Microbiol. 2015;81(14):4827-34.  https://doi.org/10.1128/AEM.00524-15  PMID: 25956776 
  26. Robertson LJ, Forberg T, Hermansen L, Gjerde BK, Langeland N. Molecular characterisation of Giardia isolates from clinical infections following a waterborne outbreak. J Infect. 2007;55(1):79-88.  https://doi.org/10.1016/j.jinf.2007.02.001  PMID: 17368548 
  27. Cacciò SM, De Giacomo M, Aulicino FA, Pozio E. Giardia cysts in wastewater treatment plants in Italy. Appl Environ Microbiol. 2003;69(6):3393-8.  https://doi.org/10.1128/AEM.69.6.3393-3398.2003  PMID: 12788741 
  28. Briancesco R, Bonadonna L. An Italian study on Cryptosporidium and Giardia in wastewater, fresh water and treated water. Environ Monit Assess. 2005;104(1-3):445-57.  https://doi.org/10.1007/s10661-005-2282-4  PMID: 15932003 
  29. Di Cave D, Berrilli F, Orecchia P, Mecozzi B, Donia D, Bonadonna L, et al. Detection and genotypic characterization of Giardia cysts in water samples. Ig Sanita Pubbl. 2005;61(1):9-16. PMID: 17211950 
  30. Plutzer J, Lassen B, Jokelainen P, Djurković-Djaković O, Kucsera I, Dorbek-Kolin E, et al. Review of Cryptosporidium and Giardia in the eastern part of Europe, 2016. Euro Surveill. 2018;23(4).  https://doi.org/10.2807/1560-7917.ES.2018.23.4.16-00825  PMID: 29382412 

Data & Media loading...

Submit comment
Comment moderation successfully completed
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error