Chlamydial infections are one of the most common sexually transmitted bacterial infections worldwide, which is related to serious consequences for the mental, sexual, and reproductive health of women and men. The infection is commonly asymptomatic; consequently, screening programs for infection control have been introduced in some countries. The detection methods of Chlamydia trachomatis infections have evolved since the establishment of the first gold-standard detection method in the 1970s, the culture assay. Over the decades, many efforts were made to find methods with a higher sensitivity, until the 1990s, when, as a result of advances in molecular biology, nucleic acid amplification tests came into use with more sensitivity, and, currently, there are several available with which to detect infection. Therefore, herein, we will review the main methods used for CT detection and the differences between them, in terms of targets, infections that can be detected, sensitivity, and specificity. We will focus on some of the FDA-approved CT detection tests and highlight the major advantages and superiority of using molecular biology techniques. In addition, we will examine the larger challenges and limitations of the methods currently in use and discuss how they might be surpassed. Moreover, in this review, we will describe the next step to carry out after testing positive for CT infection.

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led the medical and scientific community to explore the pathogenesis and clinical manifestations of coronaviruses. In felines, a widespread coronavirus known as feline coronavirus (FCoV) can lead to feline infectious peritonitis (FIP), a highly fatal disease characterised by severe systemic inflammation. Diagnosing FCoV remains challenging due to the limited accuracy of the available methods. The present study introduces the FIP Effusion Index, a novel diagnostic method that combines the albumin-to-globulin (ALB/GLOB) ratio with the delta total nucleated cell (∆TNC) count obtained via flow cytometry using the Sysmex XN-1000V^® analyser in effusions. Samples from cats (n = 50) with suspected FIP were analysed for ∆TNC, with findings showing that a ∆TNC ≥ 2.1 is highly indicative of FIP and a ∆TNC ≥ 4.9 can be considered diagnostic. The FIP Effusion Index enhanced diagnostic precision in our group of samples, achieving 96.3% sensitivity and 95.7% specificity for values ≥ 5.06, and reaching perfect specificity (100%) with 96.3% sensitivity for values ≥ 7.54. This combined approach surpasses the accuracy of individual parameters, establishing the FIP Effusion Index as a superior diagnostic tool for FIP, with potential applications in both veterinary and human medicine for related coronavirus diseases.

Chlamydia trachomatis (CT) remains the most commonly reported bacterial sexually transmitted infection (STI) globally, with particularly high incidence among adolescents and young adults. In Europe, CT cases have continued to rise over the past decade, despite ongoing public health efforts in prevention and screening. Screening coverage, however, remains inconsistent across countries. CT infections are often asymptomatic, especially in women, yet can lead to serious CT-related reproductive complications if left untreated, including pelvic inflammatory disease (PID), tubal factor infertility, and ectopic pregnancy. Emerging evidence highlights the cervicovaginal microbiota as a key factor influencing susceptibility to STIs, including CT infection, its progression, and associated outcomes. A Lactobacillus-dominated microbiota, particularly L. crispatus, is well-known to be a protective factor against CT acquisition, whereas vaginal dysbiosis, characterized by a depletion of these species and an overgrowth of anaerobes, such as Gardnerella vaginalis, Atopobium vaginae, and Prevotella spp., has been linked to increased CT acquisition risk, reduced immune control, and impaired infection resolution. Interaction between microbial communities and host immunity may modulate whether CT infections spontaneously clear, persist, or progress into pathological conditions. This review explores the natural history of CT genital infection in women, emphasizing the role of cervicovaginal dysbiosis in disease progression and reproductive sequelae. By integrating current knowledge about resident cervicovaginal microbes, host-microbe interaction, and CT-related reproductive outcomes, we discuss how microbiota-targeted strategies, including probiotic or microbiome-modulating strategies, may complement current CT prevention, diagnosis, and treatment approaches.

Leishmania infantum is the causative agent of canine leishmaniosis (CanL), a zoonotic disease of considerable clinical and epidemiological concern. Quantification of parasite load is valuable for clinical management, particularly in low-parasite-load cases. This pilot study evaluated the correlation between cytological and molecular techniques in bone marrow samples from dogs clinically affected with leishmaniosis. Amastigotes were quantified by two independent observers using light microscopy, and the same samples were analysed by real-time polymerase chain reaction (qPCR) employing Leishmania spp. specific commercial primers. Inter-observer agreement was moderate according to Cohen’s kappa (κ = 0.47) and substantial according to the intraclass correlation coefficient (ICC = 0.63), respectively, confirming measurement reproducibility. A very strong inverse correlation was found between parasite counts and qPCR cycle threshold (Ct) values (Spearman’s ρ = −0.89; p < 0.001). Furthermore, a robust logarithmic relationship (amastigotes/μL = 10^{(−0.158 × Ct + 7.61)}; R² = 0.99994) was established allowing direct estimation of in vivo parasite concentration from molecular data. These preliminary findings suggest that qPCR can serve as a reliable, semi-quantitative tool, offering higher sensitivity in subclinical infections. The integration of molecular quantification with cytological methods enhances diagnostic accuracy and supports personalised therapeutic decision-making, advancing clinical management of CanL in a One Health context.

Brucella canis is a neglected zoonotic pathogen associated with canine reproductive disorders and emerging public health concerns. This study presents the first nationwide systematic review and meta-analysis of Brucella spp. in Portugal, integrated with a 13-year retrospective seroepidemiological investigation (2013–2025) of B. canis in dogs across mainland Portugal and Insular Autonomous Regions. Among 132 canine serum samples, a seropositivity of 23.48% was observed using an immunochromatographic assay confirmed by indirect immunofluorescence (IFAT). Significant associations were identified with seasonality (p < 0.001) and breed (p = 0.001), while sex and age were not statistically significant. Municipal-level analysis revealed marked heterogeneity, with Trofa showing the highest seropositivity (58.82%) and a pooled odds ratio of 11.28 (95% CI: 2.90–43.94; p < 0.001). In parallel, meta-analyses of published data estimated a pooled seroprevalence of 2.42% in animals (95% CI: 1.79–3.13) and 10.57% in humans (95% CI: 8.80–12.47), underscoring the broader burden of Brucella spp. exposure in Portugal. These findings suggest underdiagnosis of canine brucellosis and highlight the need for enhanced surveillance in high-risk breeds and regions. The study reinforces the importance of integrated One Health strategies to improve early detection, control, and prevention of B. canis infection in both veterinary and public health contexts.

Cryptococcosis, caused by the Cryptococcus neoformans and Cryptococcus gattii species complexes (pathogenic Cryptococcus spp.), is an environmentally acquired mycosis of One Health relevance. This study integrates a PRISMA-compliant systematic review (2000–2025) of Portuguese animal, human, and environmental reports with a 13-year retrospective dataset of laboratory-confirmed veterinary cryptococcosis cases (2013–2025). Clinical specimens were cultured and identified by MALDI-TOF mass spectrometry, and associations were assessed using χ² and Fisher’s exact tests. Of 1059 submissions, 48 (4.5%) were culture-positive: 6.8% of canine, 5.3% of feline samples, and 4.0% of avian samples, with no detections in other vertebrate groups (p = 0.705). Cryptococcus neoformans predominated in carnivores (73.7%), while Papiliotrema laurentii (formerly Cryptococcus laurentii) was most frequent in birds (86.2%). Infection was not associated with sex or age. Seasonality was evident, with a July peak and summer predominance (p = 0.010). Most cases were from the Centre region (62.5%), with significant regional variation of Cryptococcus spp. distribution (p < 0.001). The systematic review confirmed autochthonous C. gattii complex disease and widespread C. neoformans contamination in pigeon guano and arboreal niches. These findings demonstrate a compartmentalised eco-epidemiology, reinforcing the need for integrated molecular typing, antifungal susceptibility testing, and coordinated human–animal–environment surveillance to inform targeted prevention and control strategies in Portugal.