Half of the growing-fattening pigs on a pig farm in Saitama Prefecture, Japan had exhibited diarrhea and growth retardation since September 2006. In January 2007, four 60-day-old, underdeveloped pigs from the farm were examined. Similar pathological findings were obtained among these pigs. In the lymph nodes, lympho cyte depletion was observed together with infiltration of macrophages, some of which contained cytoplasmic inclusion bodies. Porcine circovirus type 2 (PCV2) antigen was demonstrated in the cytoplasm of macrophages in the lymph nodes. Porcine reproductive and respiratory syndrome virus (PRRSV) was isolated from the lungs of the four pigs. In two of the four pigs, numerous round-to-ovoid organisms were found on the epithelium from the ileum to the colon, histologically. Immunohistochemically,
Cryptosporidium parvum oocyst antigen corresponded to the organisms in the intestines. In 30 of 40 (75%) fecal samples of penmates,
Cryptosporidium oocysts were detected by immunofluorescent microscopy. Using a polymerase chain reaction restriction fragment length polymorphism technique at the 18S small-subunit ribosomal RNA gene, they were identified as
C. parvum pig genotype Ⅱ or
C. suis. These findings indicated that
Cryptosporidium would be associated with diarrhea in the immunocompromised pigs with PCV2 infection and PRRS.
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