The alternation between wet and dry seasons in tropical regions can dramatically affect parasite infection dynamics by influencing larval survival, intermediate-host density, definitive-host foraging behaviour, and host immune function. Freshwater chelonians are excellent models for studying parasite-host ecology. Their longevity, site fidelity, and dietary breadth make them valuable sentinel species for aquatic ecosystem health. Here, we identified the gastrointestinal helminth fauna of scorpion mud turtle (Kinosternon scorpioides) from Marajó Island and evaluated seasonal effects on parasite community dynamics. We observed a 71% reduction in parasite load during the dry season and substantial compositional shifts, in addition to species-specific responses: Spiroxys figueiredoi exclusively during floods and Nematophila grandis peaking during dry periods. Parasite species with flexible transmission pathways may thrive while specialists decline. Kinosternon scorpioides and its parasites function as sentinels, and monitoring helminth community composition could more accurately track ecosystem health than measuring host abundance alone.

Marsupials have been the subject of experimental and natural parasitological studies on helminths in the Americas. Brazil has a significant proportion of the American marsupial fauna, with approximately 15 genera and 69 species out of 95 extant. Helminths have been reported for approximately one-third of the Brazilian marsupial species. Consequently, an update of this information is necessary to ensure the correct identification of the species. This work represents the first comprehensive review of the helminths of the Brazilian marsupials, including taxonomic information on both parasites and hosts. The data were extracted and compiled from references published from 1819 to 2023 and organised according to the classification of the helminths by the host name of the original description, followed by the updated host species nomenclature, geographical distribution, site of infection, and references. In total, 1,047 records of helminths parasitising 22 marsupial species in Brazil were compiled. The list included 93 identified species, including five of the phylum Acanthocephala, 58 of the phylum Nematoda, and 30 of the phylum Platyhelminthes. In addition, 51 other morphospecies were reported. This work may serve as a reference for future studies.

Metacercariae of Diplostomum spp. are globally distributed pathogens that infect the eyes and brains of fish and lampreys, including populations in northern latitudes. This study investigated the species diversity and distribution of Diplostomum in juvenile Atlantic salmon Salmo salar and brown trout Salmo trutta from 11 rivers in northwestern Russia. Phylogenetic analyses revealed two diplostomid species: ‘D. mergi’ Lineage 3 and D. numericum. It is the first record of these species in the Russian part of the Arctic. These species, previously recorded in Western/Central Europe and Russian Karelia, likely spread via major migratory flyways of their avian definitive hosts. The species composition of Diplostomum metacercariae in riverine salmonids of the studied region was notably poorer than in lacustrine salmonids from other Arctic localities. The haplotype distributions of recorded Diplostomum species showed no spatial structuring, consistent with broad-scale dispersal processes.

We analysed weekly influenza A intensive care unit (ICU) or high dependency unit (HDU) admissions reported by age group and subtype by NHS trusts in England through mandatory surveillance during the 2023–2024 influenza season. We investigated whether subtype reporting varied with patient age group, NHS trust type and region. We estimated the subtype ratio and explored whether this estimate varied among subsets of trusts grouped by the regularity of subtype reporting. Our aim was to explore factors relating to subtype reporting and investigate how these affect subtype ratio estimates. 112 NHS trusts reported data, with 86 trusts reporting influenza A cases and 28 trusts reporting subtyped influenza A cases. The proportion of subtype reporting trusts varied with region and trust type, but not patient age group. The estimated ratio of influenza A(H1N1)pdm09 to influenza A(H3N2) was 3.13 (95% CI: 2.17, 4.51), indicating that influenza A(H1N1)pdm09 was dominant; this was approximately similar across levels of regularity of trust subtype reporting. The accuracy of subtype ratio estimates depends on the availability of influenza A subtype information and data representativeness. We identified low levels of subtype reporting, which likely limits early recognition of new influenza strains and informing of the prescription of antivirals in influenza outbreaks.

This study provides the first integrative analysis of Megacoelium spinicavum Thatcher & Varella, 1981 (Digenea: Haploporidae) from the Amazon sailfin catfish Pterygoplichthys pardalis Castelnau, 1855 (Siluriformes: Loricariidae) in the Peruvian Amazon. A detailed morphological description is presented, including the first scanning electron microscopy (SEM) images of tegumental structures, which revealed two distinct types of tegumental spines: (1) small, button-like spines and (2) sharply pointed spines. Partial sequences of the 28S rDNA and mitochondrial cox1 genes were generated and analysed to investigate the phylogenetic position of Megacoelium Szidat, 1954, within the Haploporidae Nicoll, 1914. Phylogenetic analyses placed M. spinicavum within the ‘robust species’ clade of Saccocoelioides Szidat, 1954, clustering with S. bacilliformis Szidat, 1973, although with weak support. These results provide additional evidence that Saccocoelioides is not monophyletic and support restricting the genus to the ‘minute species’ clade containing the type species. The ‘robust species’ clade appears to comprise at least three divergent lineages, potentially representing distinct genera, one of which includes M. spinicavum. The absence of molecular data for M. plecostomi Szidat, 1954, the type species of Megacoelium, continues to obscure its phylogenetic placement. We highlight the need for comprehensive morphological and multilocus molecular analyses, including SEM, to clarify the taxonomic status of Megacoelium and to resolve the evolutionary relationships of chalcinotrematine digeneans in Neotropical fishes.

An adult female great curassow (Crax rubra) and an adult female crested guan (Penelope purpurascens) were examined post-mortem and found to harbour trematode flukes in their pulmonary air sacs and coelom, with severe pathological changes. Seven trematode specimens (four from C. rubra and three from P. purpurascens) were stained with hydrochloric acid–carmine for optical microscopy, while four specimens (two from each bird species) were submitted to molecular analysis. Morphological and molecular analyses identified the specimens as Circumvitellatrema momota. Phylogenetic analysis showed that C. momota from different geographical origins constitutes a single species within the subfamily Cyclocoelinae and is clearly distinct from other cyclocoelid genera. This is the first documented case of C. momota infecting members of the Cracidae family. These findings highlight the importance of monitoring parasitic infections in captive and free-ranging cracids under conservation programmes.

The white mullet, Mugil curema (Mugilidae), is a catadromous euryhaline fish with an omnivorous diet, and is distributed mainly along the Pacific and Atlantic coasts of the Americas. Mullets represent an important economic resource for the artisanal fisheries in Mexico. In this study, 73 individuals of M. curema were analysed; specimens were sampled in 4 coastal lagoons of the Yucatán Peninsula, Mexico, between 2022 and 2024. Parasite identification was accomplished by using DNA sequences. Nineteen parasite taxa were found, including 1 monopisthocotylan, 1 copepod, 1 acanthocephalan, 1 nematode, and 15 trematodes. Specimens were sequenced for a nuclear or mitochondrial molecular marker. Ten taxa are reported for the first time in this host species, including the adult trematodes Saccocoelioides olmecae; Schikhobalotrema sp. 1 and sp. 2, Hemiuridae gen. sp., the larval trematodes Mesostephanus microbursa, M. cubaensis, Cardiocephaloides medioconiger, Saccularina sp., Bucephalus sp., as well as the larval nematode Contracaecum fagerholmi. Of the 21 metazoan parasites recorded, 58% were adults and 42% were larval stages. The checklist of the metazoan parasites of M. curema was updated. Our study contributes to the understanding of the parasite diversity of an economically important fish species with a wide distribution range and corroborates the usefulness of combining morphological and molecular data for species identification and for linking larval forms with adults to complete parasite life cycles. Our results will be useful in further studies of parasites as bioindicators of ecosystem health, and studies of the role of parasites in food webs in coastal lagoons.

TEM analyses of germinal elements in miracidia and 6-day-old mother sporocysts of Echinostoma caproni were performed. Germinal elements in miracidia are represented by undifferentiated cells and germinal cells. They are localised in the posterior half of the body and form the primordium of the germinal mass, which plays the role of the gonad. In mother sporocysts the germinal mass is located caudally and plays the dual role of the gonad and the uterus. In addition to the undifferentiated cells and germinal cells, it contains embryos, which develop there up to the stage of germinal balls and then move into the sporocyst’s schizocoel, which plays the role of the brood chamber. New germinal cells are formed only by division of undifferentiated cells. No differences between undifferentiated and germinal cells in miracidia and those in sporocysts were found.

Amerotyphlops brongersmianus (Vanzolini, 1976) is the only representative of its family in Argentina, and to date, there have been no records of its parasites. Between 2013 and 2018, 46 specimens of A. brongersmianus were collected in Corrientes province and investigated for helminths. Eighty-three specimens of Serpentirhabdias aff. vellardi were collected from the lungs of nineteen hosts. Sixty-nine percent of the nematodes were collected from the vascular lung mostly, with a prevalence of 41.3% and a mean intensity of 3.74 worms. Adult snakes had higher prevalence and mean abundance than juveniles; the mean intensity was similar between sexes and sexual maturity groups. The association between sexual maturity and the presence of lungworms was statistically significant. Lungworm abundance, weight, and length of adult snakes showed weak to strong positive correlations, with stronger correlations in males; however, these were not statistically significant. Nematodes followed a negative binomial distribution. Seasonal differences in parasitological descriptors and mean body length of lungworms were not statistically significant. Nonetheless, a significant negative correlation was observed between lungworm abundance and body length in spring, suggesting a clustering effect. Our results are discussed based on host phenology, ecology, biology, and anatomy. The life cycles of lungworms, the abundance of potential transport hosts, as well as abiotic factors (rainfall and temperature), are also considered. This is the first report of lungworms in A. brongersmianus throughout its range, the second global report of helminths in a Typhlopidae species in the 21st century, and the first in South America and Argentina, providing ecological data.

Community-acquired pneumonia (CAP) remains an important public-health problem, and the COVID-19 pandemic and non-pharmaceutical interventions (NPIs) may have altered its burden. This study aimed to provide updated CAP burden among adults in Shanghai from 2016–2023.We analysed 61,230 participants aged 20–74 years from the Shanghai Suburban Adult Cohort and Biobank. CAP episodes were ascertained via ICD codes and clinical diagnoses. We calculated incidence rates before, during, and after NPIs, conducted subgroup analyses by age, sex, comorbidity and lifestyle. We used Poisson regression to compare stages, and Cox models to identify risk factors. The Overall CAP incidence was 42.1 per 1,000 person–years (95% CI 41.3–42.8). Incidence declined during NPIs (24.2/1,000 py) and rose after NPIs (95.9/1,000 py). The inpatient-to-outpatient ratio increased to 10.1% during NPIs and fell to 5.7% post–NPI. Among those without underlying conditions, rates were 40.1, 20.1 and 73.6/1,000 py before, during and after NPIs. Incidence was higher in participants ≥60 years and in those with multiple comorbidities, especially respiratory diseases. CAP burden temporarily fell during NPIs but resurged post–NPI, notably among high–risk groups. These findings highlight the need for targeted preventive strategies and continued CAP surveillance in the post-pandemic era.

Orientia tsutsugamushi, the causative agent of scrub typhus, is endemic to the Asia–Pacific region. In South Korea, the Boryong strain is considered dominant; however, nationwide phylogeographic distribution and genetic diversity based on clinical isolates remain incompletely characterized. In this study, 121 O. tsutsugamushi clinical isolates were collected from scrub typhus patients at 11 hospitals across South Korea between 2015 and 2024. Isolates were genotyped using 56-kDa gene sequencing and multilocus sequence typing (MLST) of seven housekeeping genes. Sequence analysis and phylogenetic reconstruction were performed using BLAST, PubMLST, BURST, MEGA11, DnaSP6, and R-based tools. Five 56-kDa genotypes were identified: Boryong (93.4%), Ikeda, Je-cheon, Young-worl, and Yeo-joo. MLST revealed 11 sequence types (STs), including five novel STs. While the Boryong strain and related STs were distributed nationwide, minor strains showed restricted distribution in northern regions. Several isolates sharing the same 56-kDa genotype exhibited different MLST STs, indicating possible recombination or local microevolution. This study provides the first nationwide MLST-based characterization of O. tsutsugamushi in South Korea and demonstrates the dominance of the Boryong strain alongside localized diversity. Our findings underscore the utility of MLST for higher-resolution typing and support the need for continued molecular surveillance to inform regional epidemiology and disease management.

This study examined whether coronavirus disease 2019 (COVID-19) infection experience enhances preventive behaviour (i.e., hand disinfection and mask-wearing), with risk perception acting as a mediating factor. The study included participants aged ≥18 years residing in Japan, enrolled in a 30-wave cohort study conducted from January 2020 to March 2024. Using propensity score matching, 135 pairs of participants with and without infection were extracted, adjusting for dread and unknown risk perception, preventive behaviours, sociopsychological variables, and individual attributes. Comparisons of risk perception and preventive behaviour were made between groups post-infection experience, and mediation analysis was conducted to test whether risk perception mediated the effect of infection experience on preventive behaviour. Following the infection experience, participants in the infection group reported significantly higher scores for one item of unknown risk perception and a greater proportion of mask-wearing. The indirect effect of infection experience on mask-wearing, mediated by the unknown risk perception item, was significant. COVID-19 infection experience increased perceptions of unknowable exposure, which in turn promoted mask-wearing behaviour. Incorporating insights from personal infection experiences into public health messaging may enhance risk perception and promote preventive behaviour among non-infected individuals, offering a novel approach to infection control at the population level.