Present and future control of cryptosporidiosis in humans and animals.

Although water treatment processes to remove Cryptosporidium are improving and detection methods for identifying the parasite in water are becoming more sensitive, outbreaks of cryptosporidiosis continue in the human population. Animals, especially dairy calves, often become infected as C. parvum oocysts are present in high numbers, remain viable for long periods of time after excretion and no disinfectants, prophylactic or therapeutic reagents exist. Vaccination against C. parvum is being attempted in ruminants for the purpose of generating hyperimmune colostrum containing antibodies that may be effective in passive immunotherapy against cryptosporidiosis in the young. A number of recombinant C. parvum surface or internal antigens have been expressed by DNA-cloning technology. Immune colostrum specific for several recombinant C. parvum proteins have demonstrated efficacy in murine and ruminant models against cryptosporidiosis. The P23 and CP15 antigens appear to be the most promising candidates for vaccine development. Recent studies have demonstrated efficacy of the drug nitazoxanide against C. parvum infection in humans. In the near future, control of this parasitic disease in humans and animals will rely on a combination of passive immunotherapy and selective drug treatment.