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Giardiasis is an intestinal infection caused by the parasitic protozoan Giardia lamblia. The diarrhea-causing infection is highly prevalent in developing nations and is a severe public health problem. It stands as one of the leading causes of death in developing countries. According to recent studies, it accounts for 3 to 4 million deaths each year in children younger than five years of age (Ochoa, 2004).

Giardia is found in both developed and in undeveloped countries. The disease, however, appears to have the largest impact in undeveloped regions where medical access and sanitation programs are not readily available. The most important effects of this disease may be seen in children in which appear to be more susceptible to the disease than adults. This may be attributed to exposure and immunity patterns. Once a person has been exposed to Giardia spp. they will develop immunity to it, thus, suppressing the usual clinical symptoms. Children, however, will show clinical signs and become ill until they build up antibodies and fight off the disease. In undeveloped countries, child mortality is much higher than in the United States. Mortality rises due to malnourishment and unfiltered, runoff water reservoirs in concert with an underdeveloped immune system. Similar patterns can also be seen in those with weakened immune systems such as, HIV/AIDS infection, organ transplant recipients, international travelers, or persons working in a daycare where individuals are at a higher risk of contracting giardiasis (www.fsis.usda.gov, 2001).

While actual vaccines to prevent disease are not available, there are some ways for humans to prevent the risk of giardiasis. Practicing sanitary awareness is the most effective tool in prevention. Washing hands with hot, soapy water before handling foods and eating after using the toilet or changing a child, staying away from unprocessed foods, such as non-pasteurized milk, and washing, peeling or cooking raw foods and vegetables that could have potentially been fertilized by manure could decrease spread via a fecal-oral route. Only drinking water from a filtration system also prevents waterborne transmission.

A vaccine has been recently released in the United States for the prevention of Giardiasis in dogs and cats. The Giardia spp. vaccine has proven successful in the reduction of giardiasis associated symptoms. It is not used for humans. However, it is a first step for controlling the parasitic disease in the face of zoonotic transmission. However, zoonotic transmission is still unclear (Pozio, 2004). Immunoprophylaxis offers a way to help control infection in high-risk populations, whether symptomatic or asymptomatic (Olsen et al., 2000). This disease is very prevalent in animals and it is important to control it since zoonotic transmission may result in spread to humans. The vaccine reduces shedding of cysts, fecal-oral transmission, and environmental contamination of water and food keeping spread to a minimum. Resultantly, both humans and animals are benefited. There are some available treatments for both humans and animals.