Giardia, Canine - contd.
Giardia is a protozoan organism that can cause infection in dogs, cats, and humans. The organisms may be found either as trophozoites that swim freely in the intestines or as trophozoites housed in cysts that protect them from the environment and thereby facilitate their transmission. Animals usually contract Giardia by coming into contact with the cyst form in the external environment; the feces of infected animals periodically contain these cysts. Animals that ingest the infected feces will take these cysts into their small intestines, where the trophozoites will excyst, or come out of their protective housing, and infect the animal by multiplying within the intestines. Afterwards, many trophozoites will encyst, or revert to cyst form, before returning to the external environment within the feces. The cysts may survive in the environment and infect other animals for a period of weeks; conversely, trophozoites that have passed into the feces without encysting will die quickly and cannot transmit the disease.
Giardia is commonly found either in dogs that have poorly functioning immune systems or in dogs that have been grouped together in close quarters and hence have been exposed to an unusually large number of the parasites. Consequently, young puppies, older dogs that are sick and debilitated, and dogs that are kept in kennels are susceptible to Giardia.
