Giardia lamblia, also known as Giardia duodenalis or Giardia intestinalis, is a parasite that causes an infection called giardiasis or lambliasis, which is relatively common in many developing countries. Since Giardia lamblia is a parasite, it needs a host to survive. However, G. lamblia cysts can survive outside of a host. These cysts are very resistant, and they can survive weeks outside of a host as long as they stay moist. If these cysts reach the mouth, oesophagus or stomach of a host animal, the parasite can multiply and attach to the mucosal wall of the intestines. The parasite causes lesions to the intestines and new cysts leave the body through the stool. Possible hosts include humans, cats, dogs, birds, and many other types of mammalians. The parasite is most common in tropical areas. Giardiasis typically affects small children and incidence peaks around the summertime. Hygiene plays a big role in the prevention of giardiasis: washing hands thoroughly makes the cysts less likely to spread.