Cryptosporidium and Giardia: treatment options and prospects for new drugs.

Cryptosporidium species and Giardia intestinalis are the most common enteric protozoan pathogens affecting humans worldwide. In recent years, nitazoxanide has been licensed in the United States for the treatment of cryptosporidiosis in non-immunodeficient children and adults, becoming the first drug approved for treating this disease. There is a need for a highly effective treatment for cryptosporidiosis in immunodeficient patients, but the quest for such a drug has proven to be elusive. While not effective against Cryptosporidium, nitroimidazoles such as metronidazole or tinidazole are effective treatments for giardiasis and can be administered as a single dose. Albendazole and nitazoxanide are effective against giardiasis but require multiple doses. Nitazoxanide is the first new drug developed for treating giardiasis in more than 20years. New potentially promising drug targets in Cryptosporidium and Giardia have been identified, but there appears to be little activity toward clinical development of new drugs.