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The cat is a reported reservoir for several zoonotic pathogens, including Cryptosporidium spp., Giardia duodenalis, and Blastocystis sp. These parasites represent a significant, but often neglected, threat to humans and animals. Furthermore, Tritrichomonas foetus has been described inhabiting the digestive tract of cats, and may be causative agents of gastrointestinal symptoms. However, scant data are available concerning the molecular epidemiology of these parasites in domestic cats in China. This study examined fecal samples from domestic cats in Eastern China to unravel the molecular epidemiology of four protozoans. Of the 346 samples examined, 47 (13.6%) were positive for the detected pathogens, including 8 (2.3%), 5 (1.4%), 2 (0.6%), and 35 (10.1%) samples positive for Cryptosporidium spp., G. duodenalis, Blastocystis sp., and T. foetus, respectively. Co-infection with Cryptosporidium spp. and T. foetus was detected in three cats, no other mixed infections were observed. No age, sex or fecal condition predisposition was observed with any of the four pathogens. The species/assemblages/subtypes/genotypes were C. felis, Assemblage A and F, ST1, and cat genotype for Cryptosporidium spp., G. duodenalis, Blastocystis sp., and T. foetus detected in this study, respectively. The presence of zoonotic species/assemblages/subtypes/genotypes poses a threat to public health. These findings provide useful information for the design of prevention and control strategies to reduce the burden of protozoal infections in cats.

Tritrichomonas species flagellates (IMC strain) were isolated from the biliary tract of an individual who had developed cholecystitis as a complication of acquired agammaglobulinemia. Sequence analysis of Tritrichomonas sp. (IMC clone 2 (cl2)) was performed for several genetic regions including the ITS1-5.8S rDNA-ITS2 region, the cysteine protease (CP)-1, CP-2 and CP-4 to CP-9 genes, and the cytosolic malate dehydrogenase 1 gene. In addition to comparison of the variable-length DNA repeats in the isolate clone with those in T. foetus (Inui cl2) and the T. mobilensis (U.S.A.: M776 cl2) reference strains, this analysis showed that the Tritrichomonas sp. (IMC cl2) was T. foetus (cattle/swine genotype). Injection of T. foetus (IMC cl2) directly into the livers of CBA mice resulted in liver abscess formation on Day 7. Moreover, inoculation via orogastric intubation caused infection in the cecum on Day 5 in CBA mice co-infected with Entamoeba histolytica (HM-1: IMSS cl6). T. foetus (IMC cl2) was able to grow in YI-S medium for over 20 days, even at 5°C. These results indicate that the T. foetus isolate is able to survive in the feces and edible organ meat of the definitive host for a prolonged period of time, and it is possible that the parasite could infect humans.

Tritrichomonas suis (=T. foetus) is a protozoan parasite of pigs, cattle and cats. Based on host range and genetic differences, T. suis has been divided into a 'cat genotype' and a 'cattle genotype', with the latter genotype capable of infecting both cattle and pigs. Since no information is currently available on the genetic characteristics of T. suis from pigs in Japan, we conducted a molecular survey of T. suis using fecal DNA from pigs in Japan. Of the 64 pigs examined, nested PCR revealed that 36 (56.3%) were positive for T. suis. Sequence analysis of 8 positive samples showed that 7 of the pig isolates belonged to the 'cattle genotype' and the remaining isolate belonged to the 'cat genotype'. The findings revealed that T. suis infection is common in pigs in Japan and that pigs can be infected by both genotypes.

Tritrichomonas suis (=T. foetus) has recently been reported to be a causative agent of chronic large-bowel diarrhea in cats. While the disease was previously attributed to Pentatrichomonas hominis, the etiologic agent for feline trichomonal diarrhea was identified as T. suis. Although feline trichomonosis due to T. suis has been reported at prevalences ranging from 14 to 31% in Europe and the U.S., no reports of the pathogen have been published to date in Japan. In 2008, however, we encountered a case of feline trichomonosis at the Veterinary Teaching Hospital of Hokkaido University. The parasite was identified as T. suis by nested PCR amplification of partial internal transcribed spacer region 1 and 5.8S ribosomal RNA gene sequences with T. suis-specific primers and DNA sequencing of the amplified products. We then conducted surveys for feline trichomonosis in three different animal hospitals using either cultivation and/or PCR-based assays. The results revealed that 13 of 147 samples (8.8%) were positive for T. suis, and that 5 of the 13 infected cats, which ranged between 1 month and 7.5 years-old, showed chronic diarrhea. Seven of the infected cats were purebred and 6 were mixed breed. These findings suggested that feline trichomonosis is prevalent in Japan, and that T. suis may play a role as a causative agent of feline chronic diarrhea.