Isao Kimata

Subgenotype analysis of Cryptosporidium parvum isolates from humans and animals in Japan using the 60-kDa glycoprotein gene sequences

Cryptosporidium parvum is a well-known intestinal parasite which is associated with severe acute diarrhea in humans and animals. This parasite is composed of morphologically identical but genetically different multiple genotypes. In humans, cryptosporidiosis is mainly caused by two C. parvum genotypes, human genotype (previously known as genotype 1 and recently proposed as new species C. hominis) and cattle genotype (previously known as genotype 2). However, recent molecular studies indicate the genetic heterogeneity among the isolates of C. parvum human or cattle genotype. Therefore, identification of the isolates at the subgenotype level is more useful for control of the Cryptosporidium infection or for understanding of the population structure of C. parvum genotypes. In the present study, we identified the subgenotypes of the C. parvum human or cattle genotype isolates from humans and animals in Japan using DNA sequencing analysis of the C. parvum 60-kDa glycoprotein gene (GP60) and showed the new subgenotype in a raccoon dog isolate. This study suggested that C. parvum cattle genotype might be composed of zoonotic and host-specific multiple subgenotypes.

Cryptosporidium infection in dogs in Osaka, Japan.

Cryptosporidium parvum is a zoonotic pathogen composed of genetically distinct but morphologically identical genotypes. Recent molecular study indicates that dogs may transmit the cattle genotype, which is known to be pathogenic to humans. Although large-scale studies of Cryptosporidium infection in dogs have been performed in several countries, the isolates were not accurately identified because of the lack of a method for molecular analysis. It is important to identify the isolates harbored in dogs, which come in close contact with humans, in order to control human cryptosporidiosis. The aim of the present study was to calculate the prevalence of Cryptosporidium infection in dogs in Osaka city, Japan, and to characterize the isolates molecularly. The prevalence was determined to be 9.3% (13/140) by PCR. All isolates were found to be Cryptosporidium canis (previously known as the dog genotype), which is thought to be non-pathogenic in humans, based on the sequencing of diagnostic fragments. These results indicate that PCR-based diagnostic methods are a useful tool for the diagnosis and molecular epidemiology of Cryptosporidium infection in dogs, and that dogs living in Osaka are not a significant reservoir for human cryptosporidiosis. It is unclear why C. canis is dominant in dogs. Further study is required to understand this partial parasitism.

Fecal-oral transmission of the cyst form of Blastocystis hominis in rats.

The infectivity of two Blastocystis hominis strains, RN94-9 and NIH:1295:1, was examined in 3-week-old SPF Wistar rats. The NIH:1295:1 strain, originally isolated from a guinea pig, was only able to infect rats via intracecal inoculation of the cultured organisms, while the RN94-9 strain, originally isolated from a laboratory rat, was able to infect rats by oral inoculation of the cultures due to the presence of a cystic form in the in vitro culture. Since many cysts were discharged in the feces of the infected rats, the infectivity of the concentrated cysts was compared between the two strains. Successful oral infection was observed in rats inoculated with 1×102–1×106 cysts of the RN94-9 and NIH:1295:1 strains. The infectivity of the ten cysts varied in the three experiments of ten rats, being 20–100% and 30–100% in the RN94-9 and NIH:1295:1 strains, respectively. When an uninfected normal rat was housed with five experimentally inoculated rats, the normal rat became infected, demonstrating the fecal-oral transmission of the cyst form of this parasite. These results show that the Wistar rat is an ideal host for the propagation of strains RN94-9 and NIH:1295:1 of B. hominis, and demonstrate that the cyst form is the only transmissible form of this parasite.

Novel Mutations in K13 Propeller Gene of Artemisinin-Resistant Plasmodium falciparum

We looked for mutations in the Plasmodium falciparum K13 propeller gene of an artemisinin-resistant parasite on islands in Lake Victoria, Kenya, where transmission in 2012–2013 was high. The 4 new types of nonsynonymous, and 5 of synonymous, mutations we detected among 539 samples analyzed provide clues to understanding artemisinin-resistant parasites.

Survey and molecular characterization of Cryptosporidium and Giardia spp. in owned companion animal, dogs and cats, in Japan

Compared with other countries, surveys of these parasites have been rarely performed in companion animals of Japan in spite of their significance for public health. Here, we investigated pet dogs and cats in Japan for the first time, and genetically analyzed the isolates to evaluate the risk of zoonotic infections. Seventy-seven fecal samples were collected from privately owned dogs and 55 samples from owned cats in Osaka city, Japan. Cryptosporidium oocysts were identified in 3/77 dogs (3.9%) and 7/55 cats (12.7%), and Giardia infection in 2/77 dogs (2.6%) and 1/55 cats (1.8%). Amplification of the target regions for genotyping was successful, Cryptosporidium isolates in dogs and cats were identified as C. canis and C. felis, respectively, and those of Giardia in dogs and cats were G. intestinalis Assemblages D and F. The discharge period of the oocysts varied within 3-16 weeks and that of the cysts was 12 weeks. To date, zoonotic types of both parasites have been identified in other animals in Japan, and further large-scale studies are needed to determine the distribution of zoonotic genotypes in these animals, especially those closely associated with humans.

Molecular characterization of crane Coccidia, Eimeria gruis and E. reichenowi, found in feces of migratory cranes

Eimeria gruis and E. reichenowi have lethal pathogenicity to a number of species of cranes. These parasites develop at multiple organs or tissues in infected cranes, thus lacking the specificity of infection sites shown by other Eimeria spp. in spite of morphologic similarity. To date, there have been many reports of crane Eimeria infections, however, genetic examinations of these parasites have never been published. In the present study, we isolated oocysts of E. gruis and E. reichenowi from crane feces at a wintering area in Japan. By phylogenic analysis, we first demonstrated that partial sequences of the isolates formed their own cluster, located separately from other Eimeria spp.

The detection of a novel type of Cryptosporidium andersoni oocyst in cattle in Japan

Cryptosporidium muris, found in rodents and cattle, has been recognized as a valid species. However, this organism from cattle was recently separated from C. muris infecting rodents based on molecular data and a transmission study. As a consequence, it has been proposed as a new species, C. andersoni. More recently, C. andersoni, which has infectivity to rodents, was detected in cattle in Japan, where it has been designated as a novel type. However, isolates from cattle in Japan have not been analyzed genetically, and therefore it remains unclear whether a novel type of C. andersoni is distributed widely in Japan. In the present study, we detected Cryptosporidium oocysts from cattle reared in a different area than those examined previously in Japan. These were identified by molecular analysis and experimental transmission. The 18S ribosomal RNA gene sequence of the isolate examined was identical with that of C. andersoni reported previously, and the isolate was successfully transmitted to severe combined immunodeficiency mice. Therefore, the isolate from cattle examined in the present study was identified as a novel type of C. andersoni. Our data suggests that it is widespread in cattle in Japan.

RECOMBINANT BOVINE HERPESVIRUS-1 EXPRESSING p23 PROTEIN OF CRYPTOSPORIDIUM PARVUM INDUCES NEUTRALIZING ANTIBODIES IN RABBITS

In order to develop a vaccine against cryptosporidiosis in cattle, we constructed a recombinant bovine herpesvirus-1 (BHV-1) expressing an immunodominant surface protein, p23, of Cryptosporidium parvum sporozoites. In the recombinant virus, the p23 gene under the control of a CAG promoter and a gene coding for an enhanced green fluorescent protein were integrated into the gG gene of BHV-1. Despite a low frequency of homologous recombination, cloning of the recombinants was easy because of the specific fluorescence of the plaques formed by recombinants. These plaques were among the plaques of the nonfluorescent parental virus. All clones selected for fluorescence also contained the p23 gene. In MDBK cells infected with the recombinant BHV-1, the antibody against the p23 protein recognized the p23 protein as an approximately 23-kDa specific band in Western blotting analysis. Rabbits immunized with the recombinant produced IgG against the p23 protein. It was also demonstrated that the sera of immunized rabbits reduced infection of C. parvum sporozoites in HCT-8 cells. The serum of an immunized rabbit reduced infection compared with the normal rabbit serum control. These results indicate that the recombinant BHV-1 induces neutralizing antibodies in rabbits.

Molecular Survey of Enterocytozoon bieneusi in a Japanese Porcine Population

Enterocytozoon bieneusi is an emerging and clinically significant enteric human pathogen that is mainly associated with chronic diarrhea. It has been identified in a variety of wild, domestic, and companion mammals and birds. This pathogen is genetically diverse and is composed of over 80 host-specific and zoonotic genotypes. Pigs are considered one of the main reservoirs of this pathogen given its high reported prevalence in pigs, and pigs may harbor zoonotic and pig-specific genotypes. Therefore, genotyping of isolates from pigs and other animals is essential for the control of E. bieneusi infection. In Japan, it remains unclear whether this pathogen is present in the porcine population. In the present study, we examined 30 fecal samples from pigs reared on 6 farms in western Japan. Ten pigs (33%) were found to be positive when assessed by polymerase chain reaction. The genotypes were varied and were found to be animal specific (EbpA, H, PigEBITS5) and zoonotic (D, EbpC) in genotype. The observation that pigs in Japan appear to be infected with zoonotic and animal genotypes of E. bieneusi raises questions about the prevalence of this infection among the human population in Japan.

Expression of P23 of Cryptosporidium parvum in Toxoplasma gondii and evaluation of its protective effects.

In this study, P23 of Cryptosporidium parvum sporozoites, an immunodominant surface protein, was stably expressed in Toxoplasma gondii (Tg/P23) and its protective effects were evaluated in a mouse model. The molecular weight and antigenic property of P23 expressed by Tg/P23 were similar to those of the native P23. Mice immunized with lysed Tg/P23 tachyzoites produced specific neutralizing antibodies against C. parvum. These findings indicate that the T. gondii vector may provide a new tool for the production of a recombinant vaccine against cryptosporidiosis in animals.