Molecular phylogeny of Blastocystis isolates from wild rodents captured in Indonesia and Japan.

Blastocystis sp. is a common intestinal protist found worldwide in a variety of animals, including humans. Currently, 17 subtypes (STs) of Blastocystis isolates from mammalian and avian host species have been reported based on the small subunit ribosomal RNA gene (SSU rDNA). Among these, human Blastocystis were only identified among STs 1-9. Except ST9, all other STs comprised isolates from humans and other animal species. Entire sequence data of the SSU rDNA of nine Blastocystis isolates from laboratory rats or guinea pigs previously showed ST4, whereas Blastocystis isolates from wild rodents have not been addressed genetically. In this study, Blastocystis infection in wild rodents was surveyed in Indonesia and Japan, and 11 and 12 rodent Blastocystis parasites were obtained from Rattus exulans and R. novercious, respectively. All new Blastocystis isolates from wild rodents were identified as ST4 based on the SSU rDNA sequences. The best tree inferred with the entire sequences of the SSU rDNA of all ST4 isolates including 17 data registered in GenBank clearly showed monophyletic ST4A and ST4B clades. Although ST4 isolates from laboratory rats were separated into these two clades, all Blastocystis isolates from wild rodents in the present study were positioned into the clade ST4A and further separated into two sub-clusters within the clade ST4A according to the location of the host species. Considering the fact that laboratory rats were susceptible to both ST4A and ST4B, separation of the monophyletic sub-clusters of Blastocystis isolates from Indonesian Polynesian rats and Japanese brown rats may indicate the presence of geographical variations rather than a host-specific separation. In either way, the robust host preference to rodent species of ST4 Blastocystis was also confirmed.

Positive correlation of HIV infection with Giardia intestinalis assemblage B but not with assemblage A in asymptomatic Kenyan children.

A cross-sectional molecular epidemiological study of Giardia intestinalis infection was conducted among asymptomatic Kenyan children with (n = 123) and without (n = 111) HIV infection. G. intestinalis assemblage B infection was positively correlated with HIV infection [HIV (+), 18.7% vs. HIV (-), 11.7%; P = 0.013], whereas assemblage A infection was not [HIV (+), 4.1% vs. HIV (-), 6.3%; P = 0.510]. Thus, HIV infection is a risk factor for G. intestinalis assemblage B infection but not for assemblage A infection.

Molecular survey of Blastocystis sp. from humans and associated animals in an Indonesian community with poor hygiene.

Blastocystis sp. is a common parasite found in human and animal fecal samples. Currently, human Blastocystis isolates are classified into nine subtypes (STs) based on the phylogeny of their small subunit ribosomal RNA genes (SSU rDNAs). Since eight of the nine STs, except for ST9, have been reported in both humans and animals, these parasites are considered to be potentially zoonotic STs. To evaluate whether zoonotic transmissions play a main role in the lifecycle of Blastocystis, STs derived from humans, domestic pigs, domestic chickens, and wild rodents in a community with poor hygiene in Sumba Island, Indonesia were surveyed. Although fecal cross-contaminations between humans and animals were likely common at the investigation site, the confirmed major Blastocystis STs, which were detected as intense bands on gels following PCR targeting of the SSU rDNA, were different in each host species. STs 1-3 were found in resident children, while ST5, ST7, and ST4 were found in domestic pigs and chickens, and in wild rodents, respectively. Faint bands of STs 1, 2, and 7 were detected in samples from pigs, while no minor STs were observed in samples from the other host species. The distinct distributions of the major STs among the host animals examined, including humans, indicate host specificity in the lifecycle of Blastocystis. Considering the coprophagous nature of pigs, the presence of minor STs observed only in pigs could be explained by the mechanical passage of contaminated fecal materials.

Lower prevalence of Entamoeba species in children with vertically transmitted HIV infection in Western Kenya.

A cross-sectional molecular epidemiological study of Entamoeba species was conducted among asymptomatic Kenyan children with (n = 123) and without (n = 111) HIV infection. The prevalence of E. histolytica was low (0.4%). Entamoeba species infection was inversely related with HIV infection [HIV(+): 29.3% vs. HIV(-): 55.0%, P < 0.001]: multiple-species infection was related to higher CD4 T-cell counts. Thus, HIV infection is not a risk factor for amebic infection, and multiple-species infection can be an indicator of better immune status.