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Theileria sergenti Shintoku stock consists of 2 parasite populations bearing 2 allelic forms of p33/32, an immunodominant piroplasm surface protein. Parasite population changes during parasite passages among cattle and tick vectors, and during persistent infection in individual calves were analysed by using allele-specific polymerase chain reaction (PCR). The parasite DNAs were prepared from piroplasms from calves which had been infected with Shintoku stock by inoculation of sporozoite stabilates or parasitized erythrocytes, and from sporozoite stabilates which had been prepared from Shintoku stock-infected ticks. Changes in a dominant parasite population were demonstrated during transmission from calves to vector ticks and from infected ticks to calves. Parasite population changes were also apparent during persistent infection in cattle over several months, and this change is thought to occur under host immune pressure. The results of this study indicate that expression of diverse forms of p33/32 may play a role in parasite persistence within mammalian hosts and its transmission from tick vector.

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ABSTRACT. Two pairs of PCR primers were designed to perform nested PCR targetting of a 540 bp fragment of the nucleocapsid (N) protein gene (N gene) of porcine epidemic diarrhea virus (PEDV). The N gene of PEDV was amplified with 4 PEDV strains and 11 small intestines of PEDV-infected piglets collected from 2 farms in Kagoshima prefecture, Japan. Nucleotide sequences of the PCR products from a Korean and two Japanese strains (KKN96-1 and S1) of PEDV isolated in 1993 and 1996, respectively, were almost identical. These results suggest that the PCR is an available tool for detection of PEDV from pigs in the field, and that the two Japanese strains (KKN96-1 and S1) were genetically similar to the Korean strain.-KEY WORDS: nested PCR, nucleocapsid protein gene, porcine epidemic diarrhea virus.

ABSTRACT. Benign Theileria species distributed in China and Korea were characterized by allele-specific polymerase chain reaction (PCR), based on the sequences of major immunodominant piroplasm surface protein genes. In China, all the isolates contained Chitose (C) type parasites. One out of 5 isolates tested was a mixed population of Ikeda (I), C and B-2 types, whereas, all the isolates from Korea consisted of I type parasites. Except for 4 isolates, 29 isolates from Korea consisted of more than two types of parasites. The present data showed that benign Theileria species distributed in these countries were mixed parasite populations. -KEY WORDS: allele, PCR, Theileria sergenti/ buffeli/orientalis.