Giardiasis

Acute gastroenteritis associated with giardia in humans is in most cases self-limiting within a few weeks (Wolfe, 2000). Vijgen et al. (Vijgen, 2007) assumed for their disease burden estimates a mean duration of 10 days for gastroenteritis cases not requiring medical help or requiring a visit to the doctor. Severe hospitalised gastroenteritis cases were assumed to last for 30 days.

We assumed that the proportion of more severe cases requiring hospitalisation would be 0.265% (360 cases requiring hospitalisation out of an estimated 136 000 incident cases) (Vijgen, 2007). Moreover, the study presents an age-specific risk of hospitalisation which we applied to the ‘severe’ health state of the symptomatic infection outcome (see Table 3).

The Dutch Association of Parasitology is not aware of fatal cases of giardia (Vijgen, 2007). Additionally, studies by Adak et al. (Adak, 2002) and Levy et al. (Levy, 1998) have not reported fatal cases.

However, a small number of deaths associated with giardiasis were reported to TESSy: nine cases between 2009 and 2013, resulting in 0.014% of notified cases. The CFP is applied to all symptomatic cases and re-distributed according to the age-group observed deaths for giardiasis and cryptosporidiosis notified between 2009 and 2013 from all Member States, with the exception of Denmark, France, Greece, Italy, Liechtenstein, the Netherlands and Portugal, because they do not report (see Table 4). Data from Bulgaria and Poland were also excluded because they only report aggregate data. It is important to note that the CFP will increase in case multipliers adjusting for under-estimation are applied to the incidence inputted in the toolkit and this should be taken into account.

Risk of complications

Apart from Irritable Bowel Syndrome (IBS) as a possible sequela of giardia, no other sequelae could be identified. However, given the fact that few studies expressed a statistical link between IBS and giardia (1–2%) (Nygard, 2006; Hanevik, 2009; Haagsma, 2010), IBS was not included as a possible complication.

Model input summary

Table 1. Transition probabilities used in the outcome tree

 Health outcome
 (Health state)

Distribution of health states in health outcome

Transition probability

Source/assumption

Symptomatic infection
(Uncomplicated)

(Complicated)



99.735%

0.265%

Age dep. (Table 3)

 

 

Fatal cases following symptomatic infection

 

0.014%
Age dependent (Table 4)

TESSy 2009-2013

Table 2. Disability weights and duration

Health outcome
(Health state)

Disability Weight (DW) (Haagsma, 2015)

Duration

DW

Label

In years

Source/assumption

Symptomatic infection
(Moderate)
(Severe)



0.149 (0.12–0.182)
0.239 (0.202-0.285)



Diarrhoea, moderate Diarrhoea, severe



0.027
0.082

Vijgen, 2007

Table 3. Age distribution of severe cases

Age class

%

0–4

27

5–9

27

10–14

3

15–64

34

≥65

8

Table 4. Age-group redistribution of CFR (applied only to complicated cases)

Age groups

%

0

12.50

1–4

6.25

5–9

6.25

10–14

0.00

15–19

0.00

20–24

0.00

25–29

0.00

30–34

6.25

35–39

0.00

40–44

0.00

45–49

6.25

50–54

12.50

55–59

6.25

60–64

6.25

65–69

6.25

70–74

6.25

75–79

18.75

80–84

6.25

>85

0.00

All ages

100.00

References

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Haagsma JA, Maertens de Noordhout C, Polinder S, Vos T, Havelaar AH, Cassini A, Devleesschauwer B, Kretzschmar ME, Speybroeck N, Salomon JA. Assessing disability weights based on the responses of 30,660 people from four European countries. Population Health Metrics 2015; 13: 10

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Lengerich EJ, Addiss DG, Juranek DD. Severe giardiasis in the United States. Clin Infect Dis, 1994.18(5):760-763.

Levy DA, Bens MS, Craun GF, Calderon RL, Herwaldt BL. Surveillance for waterborne-disease outbreaks – United States, 1995–96. MMWR CDC Surveill Summ, 1998. 47(5):1-34.

Nygard K, Schimmer B, Sobstad O, Walde A, Tveit I, Langeland N. A large community outbreak of waterborne giardiasis-delayed detection in a non-endemic urban area. BMC Public Health, 2006. 6:141.

Vijgen SMC, Mangen MJM, Kortbeek LM, Van Duynhoven YTHP, Havelaar AH. Disease burden and related costs of cryptosporidiosis and giardiasis in the Netherlands. 58 pp. Bilthoven. 2007. National Institute of Public Health and the Environment.

Wolfe MS. Giardiasis. Clin Microbiol Rev, 1992. 5(1):93-100.