giardiasis

introduction

in humans is a diarrheal infection of the small intestine caused by a single-celled protozoan parasite Giardia lamblia.
giardiasis is caused by the ingestion of infective cysts
multiple modes of transmission, including person-to-person, water-borne (eg. hikers drinking contaminated stream water from cattle faeces), and venereal
occurs worldwide
annual incidence is estimated at 2 million people
has a wide range of mammalian hosts besides humans, thus making it very difficult to eradicate.
can be fatal in the immunocompromised such as those with HIV / AIDS
incubation period 1 to 2 weeks (average 7 days)
symptoms may last 2 to 6 weeks in healthy individuals although may last longer.

the majority of infected persons develop gradual symptoms that become recurrent.
a small number of infected individuals experience an abrupt onset of abdominal cramps, watery diarrhea, vomiting, foul flatus, and fever which may last for 3–4 days before proceeding into a more sub-acute phase.
stools become greasy and malodorous but do not contain blood or pus because giardiasis does not involve dysenteric symptoms.
watery diarrhea may cycle with soft stools and constipation
upper GI symptoms including nausea, early satiety, bloating, substernal burning, egg-smelling halitosis, and acid indigestion may be exacerbated by eating and are generally present in the absence of soft stools.
anorexia, malaise, fatigue are common
weight loss affects more than 50% of patients.
other possible features:
- lactose intolerance
- biliary tract disease
- allergic manifestations such as erythema multiforme, bronchospasm, and urticaria.