Trip Answers

Question answered:18/06/08

We found little clear guidance on the topic.

 

The Patient UK website has an article on giardiasis in which it notes:

 

“Transmission
The life cycle of Giardia is very simple: the parasites (trophozoites) multiply in the duodenum, form cysts that are passed out in the faeces, and infect new individuals when they are swallowed in food or water.
The incubation period is 1-2 weeks.”

 

Concerning treatment, it states:
“Drug treatment:
• If there is dehydration this needs to be corrected.
• Metronidazole is the drug of choice for treating giardiasis. In pregnancy and breastfeeding there are some concerns and cautions about using metronidazole; details are available.
• Tinidazole and mepacrine are alternatives (mepacrine is unlicensed for this).
• Mebendazole, quinacrine and chloroquine have also been used successfully in trials in developing countries. Nitazoxanide is a new drug which may be effective.”

 

It adds in the section on complications and prognosis:

 

“The prognosis is usually good, although both failure of treatment and re-infection can occur.” [1]

 

An e-Medicine article on giardiasis states:

 

“Most infections are asymptomatic, and the attack rate for symptomatic infection in the natural setting varies from 5-70%. Giardia is found in healthy people in endemic areas and in asymptomatic carrier states with high numbers of cysts excreted in stools common.

 

Failed treatment

o Documenting the continued presence of Giardia in patients who appear unresponsive to treatment is important.
o A significant number of patients develop post-Giardia lactose intolerance and present with symptoms consistent with persistent infection. These patients usually improve with time and with the institution of a lactose-free diet.
o If Giardia is present in the patient, a careful history should indicate whether this is a reinfection or a treatment failure. A second course of the same drug should be effective in reinfections, whereas the use of an alternative drug should be effective in true treatment failures.
o Patients who fail repeated courses of treatment should be evaluated for hypogammaglobulinemia and may require combination therapy or chronic suppressive therapy.” [2]

 

A second e-Medicine article on the same topic refers to drug resistance and re-infection:

 

“Prognosis
• The prognosis is usually good.
• Reinfection is possible.
• Drug resistance has been observed in clinical experience.
• The parasite persists in the stool, and the symptoms continue for weeks if giardiasis is untreated.

 

Special Concerns
• Giardiasis is a common cause of chronic diarrhea and associated with significant morbidity, especially in children.
• If medical treatment is restricted, as in the first trimester of pregnancy, effective supportive treatment should be administered.
• Reinfection or treatment failure can be treated with a second course of the same drug or with an alternative drug.
• The potential development of later clinical infection or chronic disease is not rare in giardiasis.
Treatment of asymptomatic cyst passers can theoretically reduce the spread of infection, but whether it is cost effective remains unclear…” [3]

References
1. Patient Uk. Giardiasis. November 2007. (http://www.patient.co.uk/showdoc/40000456)
2. Pennardt A. Giardiasis. E-Medicine. February 2008. (http://www.emedicine.com/emerg/topic215.htm#section~Followup)
3. Hokelek M. Giardiasis. E-Medicine. May 2006. (http://www.emedicine.com/ped/topic847.htm#section~Followup)

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