Molecular studies on pig cryptosporidiosis in Poland. 
Cryptosporidium intestinal parasites have been detected in farmed pigs worldwide.  Infections are usually asymptomatic with a low number of oocysts shed in pig feces.  This makes the recognition of infection difficult or unsuccessful when microscopic methods are used.  The aim of this study was molecular identification of Cryptosporidium species in pig herds raised in Poland with regard to the occurrence of zoonotic species.  In total, 166 pig fecal samples were tested.  The examined pigs were aged 1 to 20 weeks.  Overall, 39 pig farms were monitored for parasite presence.  The detection and identification of Cryptosporidium DNA was performed on the basis of PCR-RFLP and nucleotide sequence analysis of the amplified 18 SSU rRNA and COWP gene fragments.  Infected animals were housed in 21 (53.8%) of the pig farms monitored.  The presence of Cryptosporidum was confirmed in 46 (27.7%) samples of pig feces.  Among positive fecal samples, 34 (29.3%) were collected from healthy animals, and 12 (24%) from diarrheic pigs.  Most infected animals (42.1%) were 2 to 3 months old.  The following parasite species were detected: C. scrofarum, C. suis and C. parvum.  Indeed, asymptomatic infections caused by C. scrofarum were observed in the majority of the herds.  Mixed infections caused by C. suis and C. scrofarum were not common; however, they were observed in 8.6% of the positive animals.  C. parvum DNA was found only in one sample collected from a diarrheic pig.  The application of molecular diagnostic tools allowed for detection and identification of Cryptosporidium species in pigs.  The sporadic findings of C. parvum are subsequent evidence for the contribution of pigs in the transmission of cryptosporidiosis from animals to humans.