Giardia lamblia

Gardia lamblia is one of the earliest parasites to have evolved and can be found world wide. It is a protozoan and one of the smaller parasites (non visible to the naked eye) with the potential to cause a lot of trouble in the notifiable disease referred to as Giardiasis. Giardia can be transmitted directly between people both due to lack of hand hygiene but also through sexual transmission. In other parts of the world poor quality of water is also a possible transmission route. 

It takes a very small amount to be significantly affected by a Giardia infection. Untreated, the infection can last for months, years or a lifetime. The incubation period is usually 7-25 days from the time of infection until symptoms of severe stomach cramps, nausea, weight loss, fatigue and diarrhea occur.