Parasite最新文献

Trematode metacercariae are the most abundant and frequently encountered helminths in freshwater fish. Yet, accurate species identification remains challenging, potentially leading to an underestimation of trematode diversity. Using data from parasitological examinations of 1,030 fish (47 species) collected from diverse freshwater habitats in Lithuania (2022-2024), we assessed the contemporary diversity of trematode metacercariae, host associations, microhabitat preferences, and changes in diversity patterns and transmission dynamics. Through integrated morphological and molecular techniques, we identified metacercariae belonging to 51 species from eight families, more than doubling previously reported diversity (25 species). While trematode family composition remained largely unchanged - the Diplostomidae and Strigeidae remained the most diverse families - notable differences were observed at the species level. Metacercariae of the Echinochasmidae and Echinostomatidae were detected for the first time, while previously reported Clinostomidae were absent. Fish of the Leuciscidae hosted the highest trematode diversity. Host specificity of metacercariae was generally low, with most species being euryxenous. At the microhabitat level, eyes harboured the highest number of species, while muscles showed the highest metacercarial density. Notably, we detected species first genetically characterised in North America (Echinoparyphium sp. 2 and Ichthyocotylurus sp. 2) and species potentially belonging to the genus Neogogatea, previously known only from Asia and North America, highlighting potential invasion risks and suggesting that European trematode diversity remains substantially underestimated. Future efforts should obtain molecular data from correctly identified adult specimens to resolve the identity of species currently identified only to the genus or family level, thereby enabling assessment of their geographical distributions and ecological roles.

The genus Oswaldocruzia represents a taxonomically diverse group of nematodes with global distribution. Although Oswaldocruzia species are widespread and exhibit a remarkably wide host range in some species, their genetic diversity and biogeographic patterns remain poorly understood. This study investigated the genetic variability and distribution of Oswaldocruzia spp. in nine anuran species from the genera Bufo, Bufotes, Pelophylax, and Rana across Central Europe and the Balkans. Two species were identified: Oswaldocruzia filiformis and O. ukrainae, each exhibiting a different range of host associations. Phylogenetic analyses based on mitochondrial COI sequences revealed significant haplotype diversity in the generalist O. filiformis, with low geographic and host-associated genetic structuring. In contrast, O. ukrainae, which is closely associated with Bufotes viridis, exhibited only one genetic variant across all samples, highlighting its restricted genetic diversity. The findings emphasize contrasting genetic diversities among nematode parasites exhibiting different levels of host-specificity and expand the known distribution of O. filiformis into new regions of the Balkans. In addition, they highlight the need for additional studies on the ecological and evolutionary factors that influence the genetic diversity of parasites in amphibians.

Tritrichomonas foetus and Pentatrichomonas hominis are two causative agents of trichomoniasis in dogs and cats, manifesting primarily through diarrhea symptoms. However, information on the prevalence and identification of T. foetus and P. hominis in dogs and cats in China is limited. Thus, to investigate the prevalence of trichomoniasis in dogs and cats in Nanchang city, South China, a total of 405 fecal samples were collected from 111 cats and 294 dogs. The presence of T. foetus and P. hominis were determined using the nested polymerase chain reaction (PCR) method, targeting the ITS1-5.8SrRNA-ITS2 of T. foetus, and 18SrRNA of P. hominis. The overall prevalence of T. foetus was 15.3% (62/405), with a prevalence of 5.8% (17/294) in dogs and 40.5% (45/111) in cats. The total prevalence of P. hominis was 17.3% (70/405), with a prevalence of 22.4% (66/294) in dogs and 3.6% (4/111) in cats. Statistical analysis revealed significant correlations between the prevalence of T. foetus and factors including breed, season and environmental conditions in dogs; in cats, there was a significant correlation with season, breeds and age. For P. hominis, the different sampling sites of dogs showed a significant correlation. Our results reveal that T. foetus is predominantly found in cats and P. hominis is predominantly found in dogs in Nanchang city. These findings contributed to effective prevention and control of trichomoniasis in dogs and cats in this region.

Dactylogyrus Diesing, 1850 is the most speciose genus of platyhelminths with more than 900 species, and over a hundred species recorded from Africa. Of the latter, six are from the straightfin barb, Enteromius paludinosus (Peters). Dactylogyrus teresae Mashego, 1983 and Dactylogyrus dominici Mashego, 1983 were collected from E. paludinosus in the Vaal River system, Gauteng, South Africa and their taxonomic data revised using standard protocols and modern approaches, alongside the type material. Whole worms were mounted on glass slides with glycerine ammonium picrate (GAP) and studied using light microscopy (LM). For scanning electron microscopy (SEM), whole worms were placed on concavity slides and the soft tissue digested to release the sclerotised copulatory organs and haptoral sclerites. A combination of these approaches (LM and SEM) was employed for the first time to study the sclerotised structures of GAP-mounted material. Soft tissues of SEM analysed specimens were genetically characterised using CO1 mtDNA, 18S-ITS1-5.8S rDNA and partial 28S rDNA fragments. Phylogenetic topologies were constructed using Bayesian inference. Results confirmed the morphologic and genetic distinctness of D. dominici and D. teresae, highlighting the importance of studying the varying orientations of specifically the vagina and transverse bar. This study presents a new locality record, the first SEM study of isolated sclerotised structures, as well as the first molecular data for the Dactylogyrus afrobarbae-like species. The multifaceted approaches applied to the same specimen in this study enabled improved resolution of individual specimens, showing promise for studies where limited specimens are available.

Microcotylids have rarely been reported along the South African coast, even though the Microcotylidae is one of the dominant polyopisthocotylan families. The present study focused on elucidating the parasite diversity of the Cape white seabream, Diplodus capensis (Smith), from various localities along the South African coast. By combining molecular and morphological techniques, two previously undescribed species of the Microcotylidae were identified. Atriaster ibamba n. sp. primarily differs from its congeners by the number and size of the hooks surrounding the genital atrium. Polylabris dassie n. sp. has a single vagina and is unique to most others of this genus by having a smaller male copulatory organ, and by the shape of this organ. This is the first report of species of Atriaster from South Africa, as well as the first report of any polyopisthocotylan from D. capensis. The present study also contributes the first genetic sequences of marine microcotylids from South Africa.

Toxoplasma gondii is the protozoan parasite responsible for toxoplasmosis, a zoonosis that represents a health risk for mammals, including marine species. Felines are the only definitive hosts of this parasite, playing a critical role in the introduction and maintenance of the pathogen in a new environment. Recent data demonstrate the contamination by T. gondii of the terrestrial and seawater environment of the Galapagos archipelago, in the Pacific Ocean. Little is known about the exposure of Galapagos' threatened species to T. gondii, although introduced domestic cats in the archipelago are known to be seropositive for T. gondii. We documented for the first time exposure to T. gondii of Galapagos sea lions (Zalophus wollebaeki), an endemic and emblematic species of the archipelago. The modified agglutination test revealed the presence of antibodies against T. gondii in 61 of 77 plasma samples collected in 2016-2017 from 2- to 4-year-old wild sea lions live-handled in their breeding sites on the inhabited island of San Cristóbal. Antibodies were also detected in 4 of 19 serum samples (21%) from sea lions whose corpses were found in 2021 on the same island. In addition, T. gondii DNA was detected in a lung sample from one necropsied pup and a tissue cyst-like structure was found in another, suggesting infection. These results, together with the high prevalence of antibodies in 2 to 4-year-olds, indicate that Galapagos sea lions are frequently exposed to T. gondii and raise concerns that toxoplasmosis may pose a threat to this endemic species.

Innovative control tools are needed against Aedes mosquitoes. The boosted sterile insect technique (bSIT) consists of treating sterile males with a biocide prior to their release to contaminate larval habitats. We compared the efficacy of SIT and boosted SIT to prevent the emergence of adult Aedes albopictus in large cages. We tested two sterile-to-fertile male ratios: 5:1 (SIT5) and 1:1 (SIT1), with and without pyriproxyfen enhancement (bSIT or SIT). The eggs were collected in ovitraps and the immature stages were monitored until adult emergence or up to 15 days after hatching to estimate the relative risk (RR) of adult emergence compared to the control category. The concentration of pyriproxyfen in the ovitrap water did not change when sterile males were released with females or alone (χ² = 0.99, df = 1, p = 0.547). This concentration was higher when the sterile-to-fertile male ratio was increased from 1:1 to 5:1: χ² = 18.8, df = 1, p = 0.006. All four treatment categories were effective in suppressing mosquito populations. With a relative risk RR = 0.194 95% CI [0.128; 0.275], SIT5 was the most effective. Boosted SIT was not as effective as SIT. However, bSIT1 (RR = 0.418 [0.351; 0.492]) and bSIT5 (RR = 0.512 [0.431; 0.596]) were equally effective. Boosted males directly vectored pyriproxyfen to breeding sites. Boosted SIT was more effective than SIT alone with a low sterile-to-fertile male ratio. Under operational conditions, it could be initially deployed to suppress the target population and then switched to standard SIT.

China was once a major endemic zone for Schistosoma japonicum, but decades of control efforts have dramatically reduced transmission. Suzhou City, in Jiangsu Province, a former hyperendemic area, achieved transmission interruption in 1995. However, the intermediate host Oncomelania hupensis persists and new habitats in non-endemic villages pose resurgence risks if parasites are reintroduced. To evaluate genetic resilience and dispersal potential, we analyzed six O. hupensis populations (214 snails) from ecologically distinct habitats in Wuzhong district, Suzhou (2018 to 2021): Guangfu (GF20 and GF21: wetlands), Jinting (JT18, JT19, and JT20: isolated island), and Dongshan (DS19: lakeside hills). Using nine microsatellite loci, we identified 91 alleles and assessed genetic diversity, structure, and demography. All populations exhibited low observed heterozygosity (Ho < 0.5), with bottlenecks detected in GF21, GF20, and JT20. Paradoxically, infinite effective population sizes (Ne) at 95% CI upper limits suggested retained adaptive potential. Significant genetic differentiation (F_ST = 0.287, p < 0.01) reflected habitat-driven isolation: Jinting's island populations diverged markedly from Dongshan and Guangfu, while bidirectional gene flow (Nm > 1) between Guangfu's temporally sampled populations indicated sustained genetic connectivity over time. DIYABC modeling traced JT20's ancestry to admixture between Jinting (JT18) and Guangfu (GF20) sources, implicating flood-mediated dispersal. Despite local control efficacy, snails retain resilience via large Ne. These findings mandate habitat-tailored strategies: habitat modification and intensified molluscicide campaigns in Guangfu and targeted eradication of Jinting's isolated populations. Integrating genetic surveillance into snail monitoring programs will be critical to sustaining transmission interruption and achieving elimination in ecologically complex regions.

In addition to the ribosomal internal transcribed spacer (ITS) locus, four loci (MS1, MS3, MS4, and MS7) have been identified to develop multilocus sequence typing tools for high-resolution genotyping of Enterocytozoon bieneusi in previous studies. However, the use of only five loci was insufficient for population genetic analysis of E. bieneusi from diverse hosts. In this study, comparison of a clinical genome sequence (C44566) with the whole genome sequence of an E. bieneusi isolate (H348) in GenBank led to the selection of the hypothetical protein 1 (hp1) and tubulin 1 (tub1) loci. Further analysis of the two loci with 156 E. bieneusi-positive samples showed high sequence polymorphisms in ITS Groups 1-6 and 10. Altogether, 30 and 23 sequence types were identified at hp1 and tub1, respectively. Genotyping based on the two loci confirmed the lack of genetic differentiation between Group 1 and Group 2 genotypes, as previously reported. Moreover, the genotypes in Groups 4 and 5 are more divergent from other genotypes within Groups 1-10. However, isolates in Group 11 and 12 could not be amplified at the hp1 and tub1 loci, supporting the previous conclusion of genetic uniqueness of the two genotype groups. The identified genetic markers and generated data could be used to develop a multilocus sequence typing tool for high-resolution genotyping of E. bieneusi, which would also have implications for understanding the taxonomy of Enterocytozoon spp., the public health significance of E. bieneusi in animals, and sources of E. bieneusi infections in humans.

Cryptosporidium is a significant zoonotic parasite with broad distribution in both humans and rodents. In this study, 510 fecal samples were collected from nine species of wild rodents across Guangxi, Yunnan, and Hunan Provinces in China. Nested PCR analysis targeting the SSU rRNA gene revealed an overall Cryptosporidium infection rate of 1.8% (9/510) among rodents in these provinces. The highest positivity rate was observed in Guangxi Province at 4.9% (5/103), followed by Yunnan Province (2.3%, 2/88), and Hunan Province (0.6%, 2/319). Notably, Rattus losea exhibited the highest prevalence rate at 9.8% (4/41), while Rattus flavipectus and Niviventer lotipes showed rates of 5.1% (2/39) and 4.4% (1/23), respectively. Various genotypes/species were identified, including Cryptosporidium viatorum, Cryptosporidium muris, Cryptosporidium vole genotype VII, and Cryptosporidium ratti, rat genotypes II, and IV. The study also found that wild rodents inhabiting mountainous areas had a higher prevalence rate at 4.9% (5/103) compared to those residing in fields and lake beaches, where prevalence rates were 2.1% (2/95) and 0.6% (2/312), respectively. This study provides new insights into Cryptosporidium infection rates among wild rodents and identifies two zoonotic species, C. viatorum and C. muris. These findings underscore the potential risk posed by Chinese wild rodent populations in transmitting zoonotic Cryptosporidium, which could significantly impact public health. Therefore, effective control strategies are needed to prevent transmission between humans and rodents.