Pathogens

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infection in infants, but circulating biomarkers for severity stratification remain insufficiently validated. This systematic review evaluated circulating biomarkers associated with acute RSV disease severity in children aged≤ 24 months. PubMed, Web of Science, and Scopus were searched for English-language reports published between 1 January 2016 and 1 March 2026, with the last searches performed on 1 March 2026. Study-level risk of bias was assessed using the Newcastle–Ottawa Scale or the Joanna Briggs Institute checklist, according to study design. Findings were synthesized descriptively using study-level effect estimates and reported severity-discrimination measures. Twenty-four studies contributed 174 extractable comparisons. Biomarker associations varied across populations, age strata, sampling times, and severity definitions, and reproducibility across independent cohorts was limited. In one cohort, fibrinogen and the fibrinogen-to-albumin ratio (FAR) showed large differences between severity groups; FAR had a reported AUC of 0.875. These findings do not establish comparative superiority or external validity. Important limitations include heterogeneous clinical comparisons, limited confounder adjustment, and predominantly single-cohort evidence. Current evidence does not support using FAR, the neutrophil-to-lymphocyte ratio (NLR), or other circulating biomarkers alone to predict subsequent clinical deterioration. Whether these markers add useful information to clinical assessment requires prospective validation. Registration: PROSPERO, CRD420261471336.

Viral nervous necrosis (VNN), caused by betanodaviruses, is a major constraint to marine finfish aquaculture worldwide. This study reports the first detection and molecular characterization of an RGNNV/SJNNV reassortant betanodavirus in farmed gilthead seabream (Sparus aurata) in the Suez Canal basin, Egypt. Four mortality episodes in two adjacent marine hatcheries affected fry from 12 days post-hatching through juveniles of seven months. Affected fish showed nervous signs, and brain histopathology revealed spongiform vacuolation and neurodegeneration. No parasitic or bacterial pathogens were detected. RT-qPCR and conventional RT-PCR detected betanodavirus RNA in clinically affected fry and juveniles and in brains of apparently healthy broodstock. In one hatchery, viral RNA was also detected in incoming well water. Partial RNA1 and RNA2 sequencing of a virus from a single adult fish identified a reassortant strain, designated EGY_Waf25, comprising RGNNV RNA1 and SJNNV RNA2. EGY_Waf25 clustered with Mediterranean and North African reassortant betanodaviruses but formed a distinct branch in RNA1-, RNA2-, and concatenated RNA1/RNA2-based analyses. Genetic distance analyses supported this placement while indicating local differentiation. These findings extend the recognized geographic occurrence of RGNNV/SJNNV reassortants to the Suez Canal basin and identify a potential regional biosecurity risk for Egyptian mariculture. Enhanced surveillance, routine broodstock screening, and water monitoring are recommended.

Parasites impose energetic and physiological costs on their hosts, potentially influencing behavioural time budgets, yet responses may vary among parasite taxa and host sexes. In this study, relationships between parasite burden and activity budgets in free-ranging bighorn sheep (Ovis canadensis) in southwestern Alberta, Canada were investigated. Behavioural observations and fecal samples were collected over seven months, and fecal egg, larval, and oocyst counts were used to quantify infection with multiple gastrointestinal helminth, lungworm, and protozoan taxa. Generalized linear mixed models examined associations between parasite burden and the proportion of time allocated to grazing, rumination, and movement while accounting for age, sex, and parasite-by-sex interactions. Females spent a greater proportion of time grazing than males. Grazing also showed weak evidence of sex-specific associations with lungworm larval counts and Trichuris fecal egg counts. Rumination was associated with a significant interaction between sex and Nematodirus fecal egg counts, indicating that males and females differed in their behavioural responses to this parasite. No predictors were associated with the proportion of time bighorn sheep spent moving. Overall, behavioural responses to parasitism showed stronger evidence for sex-dependent relationships than for consistent main effects of parasite abundance. These findings highlight the complexity of behavioural responses to parasitism in wild ungulates and suggest that host sex may influence how parasite infections are reflected in time allocation to different activities.