Investigating giardiasis and long term complications

Bergen Giardia Research Group



Research projects

Involved researchers

BGRG & publications

News & Links

Bergen Giardia Research Group (BGRG) is a network of scientists and physicians who cooperate in planning and implementing research projects to evaluate the long term sequelae after the Giardia epidemic and to understanding the mechanisms behind these. Some treatment trials have also been conducted.

We hope this research will lead to treatment alternatives for these conditions.


Publication list (updated August 2023):


1. Nygard K, Schimmer B, Sobstad O, Walde A, Tveit I, Langeland N, Hausken T,

Aavitsland P. A large community outbreak of waterborne giardiasis-delayed detection in a

non-endemic urban area. BMC Public Health. 2006 May 25;6:141.


2. Robertson LJ, Hermansen L, Gjerde BK, Strand E, Alvsvåg JO, Langeland N.

Application of genotyping during an extensive outbreak of waterborne giardiasis in Bergen,

Norway, during autumn and winter 2004.  Appl.Environ.Microbiol. 2006; 72:2212-7.


3. Robertson LJ, Forberg T, Hermansen L, Gjerde BK, Alvsvåg JO, Langeland N. 

Cryptosporidium parvum infections in Bergen, Norway, during an extensive outbreak of

waterborne giardiasis in autumn and winter 2004.  App Environ Microbiol. 2006;72(3):2218-20


4. Robertson LJ, Forberg T, Hermansen L, Gjerde BK and Langeland N. Molecular

characterisation of Giardia isolates from clinical infection following a waterborne outbreak.

J Infect. 2007 Jul;55(1):79-88.


5. Robertson LJ, Forberg T, Hermansen L, Gjerde B, Langeland N. Demographics of

Giardia infections in Bergen, Norway, subsequent to a waterborne outbreak.  Scand J

Infect Dis. 2007 Jul 31;:1-4


6. Wensaas KA, Langeland N, Rørtveit G. Uncovering the giardiasis-outbreak in Bergen

2004. Tidsskr Nor Laegeforen. 2007 Sep 6;127(17):2222-5


7. Hanevik K, Hausken T, Morken MH, Strand EA, Mørch K, Coll P, Helgeland L,

Langeland N.  Persisting symptoms and duodenal inflammation related to Giardia

duodenalis infections. J Infect. 2007 Dec;55(6):524-30.


8. Dizdar V, Gilja OH, Hausken T. Increased visceral sensitivity in Giardia-induced

postinfectious irritable bowel syndrome and functional dyspepsia. Effect of the 5HT3-

antagonist ondansetron. Neurogastroenterol Motil. 2007 Dec;19(12):977-82


9. Hanevik K, Mørch K, Eide GE, Langeland N, Hausken T. Effects of albendazole/

metronidazole or tetracycline/folate treatments on persisting symptoms after Giardia

infection: a randomised open clinical trial.  Scand J Infect Dis. 2008;40(6-7):517-22


10. Mørch K, Hanevik K, Robertson LJ, Strand EA, Langeland N. Treatment-ladder and

genetic characterisation of parasites in refractory giardiasis after an outbreak in Norway.

J Infect. 2008 Apr;56(4):268-73.


11. Robertson LJ, Forberg T, Gjerde B (2008). Giardia cysts in sewage influent in Bergen,

Norway over one year after an extensive outbreak of giardiasis. J. Appl. Microbiol. 104:



12. Strand, E.A., Robertson, L.J., Alvsåg, J.O. et al.  (2008). Sensitivity of a Giardia

antigen test in persistent giardiasis following an extensive outbreak. Clin Microbiol Infect.

2008 Nov;14(11):1069-71.


13. Wensaas KA, Langeland N, Rortveit G. Prevalence of recurring symptoms after

infection with Giardia lamblia in a non-endemic area. Scand J Prim Health Care. 2008 Dec



14. Mørch K, Hanevik K, RortveitG, Wensaas KA, Langeland N. High rate of fatigue and

abdominal symptoms 2 years after an outbreak of giardiasis. Trans R Soc Trop Med Hyg.

2009 May;103(5):530-2.


15. Hanevik K, Dizdar V, Langeland N, Hausken T. Development of functional

gastrointestinal disorders after Giardia lamblia infection. BMC Gastroenterology 2009, 9:27.


16. Morch K, Hanevik K, Rortveit G, Wensaas KA, Eide GE, Hausken T, Langeland N.

Severity of Giardia infection associated with post-infectious fatigue and abdominal

symptoms two years after. BMC Infect Dis. 2009, 9:206. doi:10-1186/1471-2334-9-206


17. Robertson LJ, Hanevik K, Escobedo AA, Mørch K, Langeland N. Giardiasis—why do

the symptoms sometimes never stop. Trends Parasitol. 2010  Jan; 26(2):75-82


18. Dizdar V, Spiller R, Singh G, Hanevik K, Gilja OH, El-Salhy M, Hausken T. Relative

importance of abnormalities of CCK (cholecystokinin) and 5-HT(serotonin) in Giardia-

induced post-infectious irritable bowel syndrome and functional dyspepsia. Aliment

Pharmacol Ther. 2010 Feb 2.


19. Wensaas KA, Langeland N, Rortveit G. Post-infectious gastrointestinal symptoms after

acute giardiasis. A 1-year follow-up in general practice. Fam Pract. 2010 Jun;27(3):255-9.

2010 Mar 22.


20. Mellingen KM, Midtun A, Hanevik K, Eide GE, Søbstad Ø, Langeland N. Post epidemic

giardiasis and gastrointestinal symptoms among preschool children in Bergen, Norway. A

cross-sectional study. BMC Public Health. 2010 Mar 26;10:163.


21. Escobedo AA, Almirall P, Robertson LJ, Franco RM, Hanevik K, Mørch K, Cimerman

S. Giardiasis: the ever-present threat of a neglected disease. Infect Disord Drug Targets.

2010 Oct 1;10(5):329-48.


22. Hanevik K, Dizdar V, Langeland N, Eide GE, Hausken T. Tolerability and effect of

mesalazine in postinfectious irritable bowel syndromeAliment Pharmacol Ther.2011



23. Wensaas KA, Langeland N, Hanevik K, Mørch K, Eide GE, Rørtveit, G. Irritable bowel

syndrome and chronic fatigue three years after acute giardiasis: historic cohort study. Gut



24. Hanevik K, Kristoffersen E, Svard S, Bruserud O, Ringqvist E, Sørnes S, Langeland N.

Human Cellular Immune Response Against Giardia lamblia 5 Years After, Acute

Giardiasis. J Infect Dis. 2011 Dec;204(11):1779-86.


25.Hunskar GS, Langeland N, Wensaas KA, Hanevik K, Eide GE, Mørch K, Rortveit G.

The impact of atopic disease on the risk of post-infectious fatigue and irritable bowel

syndrome 3 years after Giardia infection. A historic cohort study. Scand J Gastroenterol.

2012 Jul 2.


26. Hanevik K, Kristoffersen EK, Sørnes S, Mørch K, Næss H, Rivenes AC, Bødtker JE,

Hausken T, Langeland N. Immunophenotyping in post-giardiasis functional gastrointestinal

disease and chronic fatigue syndrome. BMC Infect Dis. 2012 Oct 14;12(1):258


27. Mørch K, Hanevik K, Rivenes AC, Bødtker JE, Næss H, Stubhaug B, Wensaas KA,

Rortveit G, Eide GE, Hausken T, Langeland N. Chronic fatigue syndrome 5 years after

giardiasis: differential diagnoses, characteristics and natural course. BMC Gastroenterol.

2013 Feb 12;13(1):28


28. Hanevik K, Wensaas KA, Rortveit G, Eide GE, Mørch K, Langeland N. Irritable bowel

syndrome and chronic fatigue six years after Giardia infection: a controlled prospective

cohort study. Clin Infect Dis. Advance access online August 12, 2014.


29. Hanevik K, Bakken R, Brattbakk HR, Saghaug CS, Langeland N. Whole genome

sequencing of clinical isolates of Giardia lamblia. Clin Microbiol Infect. 2015 Feb;21



30. Persson R, Wensaas KA, Hanevik K, Eide GE, Langeland N, Rortveit G. The

relationship between irritable bowel syndrome, functional dyspepsia, chronic fatigue and

overactive bladder syndrome: a controlled study 6 years after acute gastrointestinal

infection. BMC Gastroenterol. 2015 Jun 10;15:66.


31. Saghaug CS, Sørnes S, Peirasmaki D, Svärd S, Langeland N, Hanevik K. Human

Memory CD4+ T Cell Immune Responses against Giardia lamblia. Clin Vaccine Immunol.

2015 Sep 16;23(1):11-8.


32. Robertson LJ, Tysnes KR, Hanevik K, Langeland N, Mørch K, Hausken T, Nygård K.

Dogs as the source of Giardia in Bergen in 2004 – barking up the wrong tree? Tidsskr Nor

Laegeforen. 2015 Oct 20;135(19):1718-20.


33. Litleskare S, Wensaas KA, Eide GE, Hanevik K, Kahrs GE, Langeland N, Rortveit G.

Perceived food intolerance and irritable bowel syndrome in a population 3 years after a

giardiasis-outbreak: a historical cohort study. BMC Gastroenterol. 2015 Nov 19;15:164.


34. Wensaas KA, Hanevik K, Hausken T, Eide GE, Langeland N, Mørch K, Rortveit G.

Postinfectious and sporadic functional gastrointestinal disorders have different

prevalences and rates of overlap: results from a controlled cohort study 3 years after acute

giardiasis. Neurogastroenterol Motil. 2016 May 18.


35. Hunskar GS, Bjorvatn B, Wensaas KA, Hanevik K, Eide GE, Langeland N, Rortveit G.

Excessive daytime sleepiness, sleep need and insomnia 3 years after Giardia infection: a

cohort study. Sleep Health. 2016 June. Volume 2, Issue 2, Pages 154–158.


36. Hanevik K, Kristoffersen E, Mørch K, Rye KP, Sørnes S, Svärd S, Bruserud Ø,

Langeland N. Giardia-specific cellular immune responses in post-giardiasis chronic fatigue

syndrome. BMC Immunol. 2017 Jan 28;18(1):5.


37. Radunovic M, Klotz C, Saghaug CS, Brattbakk HR, Aebischer T, Langeland N,

Hanevik K. Genetic variation in potential Giardia vaccine candidates cyst wall protein 2

and α1-giardin. Parasitol Res. 2017 Jun 3.


38. Litleskare S, Rortveit G, Eide GE, Hanevik K, Langeland N, Wensaas KA.

Prevalence of Irritable Bowel Syndrome and Chronic Fatigue 10 Years after Giardia

Infection. Clin Gastroenterol Hepatol. 2018 Jan 25.


39. Hanevik K, Wik E, Langeland N, Hausken T. Transient elevation of

anti-transglutaminase and anti-endomysium antibodies in Giardia infection. Scand

J Gastroenterol. 2018 Jun 16:1-4. doi: 10.1080/00365521.2018.1481522


40. Hjøllo T, Bratland E, Steinsland H, Radunovic M, Langeland N, Hanevik K.

Longitudinal cohort study of serum antibody responses towards Giardia lamblia

variant-specific surface proteins in a non-endemic area. Exp Parasitol. 2018 Jun

14. doi: 10.1016/j.exppara.2018.06.005


41. Lalle M & Hanevik K. Treatment-refractory giardiasis: challenges and

solutions. Infection and Drug Resistance 2018:11 1921–1933.


42. Dizdar V, Hausken T, Larum OD, Gilja OH, Langeland N, Hanevik K. Prolonged duodenal

mucosal lymphocyte alterations in patients with and without post infectious functional

gastrointestinal disorders after Giardia infection. J Infect Dis. 2018 epub Nov 30.


43. Litleskare S, Rortveit G, Eide GE, Emberland KE, Hanevik K, Langeland N, Wensaas

 KA. Quality of life and its association with irritable bowel syndrome and fatigue ten years

after giardiasis. Neurogastroenterol Motil. 2019 May;31(5):e13559


44. Davids BJ, Liu CM, Hanson EM, Le C, Ang J, Hanevik K, Fischer M, Radunovic M, 
Langeland N, Ferella M, Svärd SG, Ghassemian M, Miyamoto Y, Eckmann L. Identification 
of conserved candidate vaccine antigens in the surface proteome of Giardia lamblia. Infect 
Immun. 2019 Apr 8. pii: IAI.00219-19

45.Christina S Saghaug CS, Klotz C, Kallio JP, Brattbakk HR, Stokowy T, Aebischer T,

Kursula I, Langeland N, Hanevik K. Genetic variation in metronidazole metabolism and

oxidative stress pathways in clinical Giardia lamblia assemblage A and B isolates. Infection

and Drug Resistance 2019:12 12211235


46. Martínez C, Lasitschka F, Thöni C, Wohlfarth C, Braun A, Granzow M, Röth R, Dizdar V, Rappold GA, Hausken T, Langeland N, Hanevik K, Niesler B. Comparative expression profiling in the intestine of patients with Giardia-induced postinfectious functional gastrointestinal disorders. Neurogastroenterol Motil. 2020 Sep;32(9):e13868.


47. Mørch K, Hanevik K. Giardiasis treatment: an update with a focus on refractory disease. Curr Opin Infect Dis. 2020;33(5):355-364


48. Saghaug CS, Klotz C, Kallio JP, Aebischer T, Langeland N, Hanevik K. Genetic Diversity of the Flavohemoprotein Gene of Giardia lamblia: Evidence for High Allelic Heterozygosity and Copy Number Variation. Infect Drug Resist. 2020 Dec 18;13:4531-4545


49. Hunskar GS, Rortveit G, Litleskare S, Eide GE, Hanevik K, Langeland N, Wensaas KA. Prevalence of fibromyalgia 10 years after infection with Giardia lamblia: a controlled prospective cohort study. Scand J Pain. 2021 Oct 22.


50. Hanevik K, Saghaug C, Aaland M, Morch K, Langeland N. No difference in serum levels of B-cell activating receptor and antibodies against cytolethal distending toxin B and flagellin in post-infectious irritable bowel syndrome and chronic fatigue syndrome after Giardia infection. JGH Open. 2022 Mar 14;6(3):185-188.


51. Saghaug CS, Gamlem AL, Hauge KB, Vahokoski J, Klotz C, Aebischer T, Langeland N, Hanevik K. Genetic diversity in the metronidazole metabolism genes nitroreductases and pyruvate ferredoxin oxidoreductases in susceptible and refractory clinical samples of Giardia lamblia. Int J Parasitol Drugs Drug Resist. 2023 Apr;21:51-60.


BGRG & Publications

Webansvarlig: Kurt Hanevik

BGRG, Haukeland Universitetssykehus

Institutt for indremedisin

2.etg, sentralblokken

5021 Bergen, Norway

Contact us: