International journal for parasitology最新文献

Giardia duodenalis is a gastrointestinal parasite and one of the most frequently reported parasitic infections associated with contaminated water. This study investigated the diversity of domestic and imported Giardia assemblages in Norway, with a focus on the genetic characterization of domestic assemblage A isolates using multi-locus sequence typing (MLST) targeting six genome markers. We analysed 340 human, and 40 animal faecal samples collected between February 2022 and January 2024 from six medical microbiology laboratories and one veterinary diagnostic center across four Norwegian health regions. All the samples were analysed using nested PCR targeting part of the triose-phosphate isomerase (tpi) gene, and MLST was performed on 33 assemblage A isolates, targeting six polymorphic markers. The results revealed that assemblage B was most prevalent in humans (59 %), followed by assemblage A (41 %). Among the sub-assemblages, AII was the most frequently identified (37 %), followed by BIII (32 %), and BIV (27 %). Regarding the origin of infection, 30 % were of domestic origin, while 33 % were reported as imported-primarily originating from Africa (48 %) and South-East Asia (22 %). Sub-assemblage AII (46 %) was more common in domestic cases, whereas BIV (42 %) predominated in imported cases. We found a regional clustering of sub-assemblages, with AII frequently identified in Western Norway, BIII in South-Eastern Norway, and BIV in Mid Norway. The MLST analysis of domestic assemblage A isolates demonstrated high genetic variation, identifying 20 distinct MLST types among 21 isolates, including five novel variants. In animals, assemblage E was most common (62 %). This study provides a comprehensive overview of Giardia assemblages in human infections in Norway, offering insights into their genetic diversity. It also underscores the feasibility of employing MLST as a tool to evaluate potential epidemiological links of Giardia assemblage A isolates.

This paper examines the impact of climate change in Africa on the transmission potential (Q₀) of Haemonchus contortus (H. contortus), a highly pathogenic haematophagous gastrointestinal nematode (GIN) parasite that has significant implications for the health and productivity of small ruminants. Changes in Q₀ were assessed over the period 1981-2070 under a high emission scenario (RCP 8.5). Climate data was sourced from bias-adjusted Coordinated Regional Climate Downscaling Experiment (CORDEX) models for Africa, which was split into 13 subregions based on areas within each having approximately similar rainfall seasons, which also defines typical periods of H. contortus transmission in Africa. Results indicate that while the transmission potential of H. contortus may increase across some months in the Atlas region and in some high-elevation and coastal areas, Q₀ is more widely projected to decrease across much of Africa. While climate change is not expected to alter the length of the transmission season in most areas of Africa, marginally shorter transmission periods are expected in southern East Africa, the Gulf of Guinea, and the Eastern Sahel, while new periods of transmission are projected to occur in western Southern Africa. Future research should focus on optimising the model for Africa and developing a decision-support tool for farmers, advisors and animal health services that classifies Q₀ by hazard severity and provides tailored management recommendations for each category.

The protozoan parasite Toxoplasma gondii relies on antioxidant proteins and systems to protect against the host's immune responses and to neutralize free radicals produced by its own metabolism. In this study, we identified and characterized a new thioredoxin protein, TgTrx1, which is mainly found in the cytoplasm of T. gondii tachyzoites and contains a conserved -CXXC- catalytic motif. Using CRISPR-Cas9 gene editing, we disrupted the TgTrx1 gene to generate a knockout strain (RHΔtrx1) and studied the effect of gene loss on various aspects of the infection process. RHΔtrx1 parasites showed a marked reduction in their ability to invade host cells, secrete microneme proteins, replicate intracellularly, egress from host cells, and tolerate oxidative stress. They also displayed abnormal mitochondrial morphology and asynchronous cell division. Transcriptomic analysis revealed significant changes in the expression of genes involved in oxidative stress response and bradyzoite differentiation. Mice injected intraperitoneally with 10⁶ RHΔtrx1 tachyzoites showed no clinical symptoms. However, the immunity induced by these attenuated tachyzoites conferred only partial protection against subsequent acute and chronic T. gondii infections. This limited protective effect is likely related to the parasite's impaired replication, which may lead to rapid clearance by the host immune system and insufficient antigenic stimulation to elicit a fully protective immune response. These findings establish TgTrx1 as a multifunctional redox protein important for T. gondii survival, redox balance, synchronous cell division, and virulence.

Fasciola hepatica and Calicophoron daubneyi are trematodes with significant health and economic impacts on ruminant livestock farms. An effective and reliable diagnosis is essential to control their spread. To improve copromicroscopic diagnosis, the Kubic FLOTAC Microscope (KFM), a portable digital microscope, was designed for both laboratory and field use. It is based on the use of FLOTAC/Mini-FLOTAC techniques and combines their high sensitivity, accuracy and precision with a reliable system based on an Artificial Intelligence (AI) predictive model. It features automated parasite egg detection, powered by an integrated battery, a web interface for microscope control, and a dedicated AI server for image analysis. In this study, the system was optimized to better discriminate between the eggs of these two parasites through additional processing steps and a robust detection model. Two protocols, egg-spiked samples and naturally infected samples, were used to simulate different sample conditions, creating a dataset for model training and evaluation. A second dataset of field samples, with egg counts verified by optical microscopy, was used to assess performance. The detection performance during the evaluation of samples from both protocols was found to be satisfactory. Specifically, the average fecal egg count, obtained through the clinical report generated by the KFM system, exhibited a mean absolute error of only 8 eggs per sample. This result demonstrates that the KFM is a valuable tool for parasitological diagnosis that supports the livestock industry.

Spliceosomal introns, distinctive features of eukaryotic genomes, are non-coding sequences excised from pre-mRNAs by the spliceosome, contributing to genome evolution and protein diversity. Although spliceosomal introns have been characterised in several eukaryotic lineages, their origin and evolution remain unresolved. The protozoan parasite Trichomonas vaginalis is a highly divergent eukaryote with a large genome and a rich gene repertoire, but apparently few spliceosomal introns. Following from the discovery of a group of unusually short introns in this organism, we developed here a fluorescent reporter system and combined with extensive mutagenesis to dissect the splicing requirements of these short introns, comparing them to conventional long introns. We found that short introns have reasonable but limited flexibility in their length, including extreme juxtaposition of the branch site and the 3' splice site, which, to our knowledge, is an unprecedented feature among eukaryotic introns. Additionally, they clearly exhibit splice signal features that distinguish them from long introns, including a highly degenerate 5' splice site. Remarkably, we found that T. vaginalis is capable of trans-splicing an endogenous intron that was deliberately split and a naturally split intron from Giardia lamblia, a more distant diplomonad within the same Metamonada supergroup. Collectively, our findings highlight the evolutionary plasticity of RNA splicing systems in divergent eukaryotes, offering new perspectives on splicing mechanisms by the spliceosome.

Taenia solium is a zoonotic parasite causing significant health and economic burdens, with complex transmission dynamics that demand improved control strategies. This study examines how infection and reinfection affect cyst development in pigs and how acquired immunity constrains parasite burden. A total of 116 pigs were purchased from commercial farms in northern Peru and housed under controlled conditions. Of these, 110 pigs were allocated to 18 experimental groups to evaluate the impact of single and repeated infections with varying doses of T. solium eggs and to model the number of live cysts produced based on dose and age at infection. Gravid proglottids collected from human cases were used to prepare viable egg pools. Infections were administered orally via esophageal catheterization, and pigs were necropsied 10 weeks after the final infection to quantify cyst burden. A negative binomial regression model assessed the influence of infection dose, prior infection, age, and other factors. No significant differences in cyst counts were found between singly infected and reinfected pigs, regardless of initial or reinfection doses, highlighting that infection induces strong acquired immunity that prevents subsequent infections. A dose-response analysis indicated that cyst burden follows a power relationship with egg dose. Integrating data from both single and reinfected pigs into a unified model improved prediction precision. Furthermore, incorporating age at infection allowed us to model the combined effects of acquired and innate immunity, reflecting changes in susceptibility over time. These findings demonstrate that a single exposure to T. solium eggs can generate robust protective immunity in pigs. The resulting quantitative model, predicting viable cyst counts based on dose and age, offers valuable insights for integrating immunity dynamics into transmission models, supporting the development of more effective strategies for controlling T. solium.

Small wildlife species host flea and tick species that can also infest or transmit pathogens to domestic animals and humans, including Anaplasma, Babesia, Bartonella, Borrelia, Ehrlichia, and Rickettsia species. Despite their zoonotic potential, little is known regarding the prevalence, diversity, and epidemiology of these pathogens. Therefore, we aimed to survey the ectoparasites found on Eastern Cottontail Rabbits (rabbits), Eastern Grey Squirrels (squirrels), and Virginia Opossums (opossums) in south-central Wisconsin, and describe the prevalence of select pathogens. Ectoparasites were opportunistically collected from small mammals, then identified to the species level, pooled, washed, and DNA extracted for quantitative PCR (qPCR) to detect Anaplasmataceae, Apicomplexa, Bartonella, hemotropic Mycoplasma, and Rickettsia. To analyze the genomic diversity of uncharacterized Bartonella, three flea pools were subject to metagenomic sequencing. Cediopsylla simplex and Haemaphysalis leporispalustris were the most common ectoparasites on rabbits, while Orchopeas howardi was most common on squirrels and opossums. Bartonella species were detected in C. simplex pools (n = 52), most commonly two distinct Bartonella alsatica-like bacteria (38 %; 20/52). Bartonella durdenii, definitively identified by metagenomic sequencing, was detected in 42 % (13/31) of O. howardi pools from squirrels. From metagenomic sequencing, B. alsatica-like species displayed a 4.8 % dissimilarity rate while B. durdenii displayed a 0.4 % dissimilarity rate. Sequencing of one B. alsatica-like flea pool also identified phage-associated genes not found in the B. alsatica genome. Rickettsia felis (n = 1) and opossum-associated hemotropic Mycoplasma sp. (n = 2) were detected in O. howardi from opossums. Rickettsia bellii and Anaplasma sp. were detected in Haemaphysalis leporispalustris from rabbits. These findings reinforce the value of metagenomic sequencing, facilitating the correct identification of B. durdenii and identifying genes not found in the type strain, specifically phage related genes. Due to the known zoonotic potential of B. alsatica, further examination of B. alsatica-like and B. durdenii pathogenicity is warranted.