Antimicrobial resistance (AMR) is a global health emergency. The growing levels of multidrug-resistant bacteria in companion animals represent a critical but under-recognized threat, as pets can act as reservoirs and vectors of resistant pathogens, and bacteria can spread between species. Despite living in close proximity to humans and sharing many of the same antibiotic classes, companion animals remain largely overlooked in the AMR control strategies. A major obstacle to combating AMR in Europe is the absence of a mandatory and uniform surveillance system. Without a standardized approach, data collection remains inconsistent, leading to knowledge gaps and hindering effective investigation and policymaking. Surveillance failures prevent a comprehensive understanding of resistance patterns, making it difficult to implement timely and evidence-based measures. Existing laws and regulations are insufficient to contain the growing threat of AMR. Current policies fail to enforce strict antimicrobial stewardship across all European countries and lack the necessary scope to address resistance effectively. Urgent action is required—Europe must implement stronger, harmonized surveillance systems, enforce stricter veterinary antimicrobial regulations, and develop more active and binding programs to curb resistance before it reaches an uncontrollable level. A One Health approach, recognizing the interconnectedness of human, animal, and environmental health, is essential.

Aquatic resistomes are important reservoirs of antibiotic resistance genes (ARGs) and their precursors, which can proliferate and dissipate in pathogenic microorganisms that affect humans and animals, especially due to anthropogenic pressures such as the intensive use of antibiotics in aquaculture, often without effective regulation. This review addresses the mechanisms of horizontal gene transfer (HGT) in the dissemination of ARGs through mobile genetic elements (MGEs). In freshwater, genera such as Aeromonas, Pseudomonas and Microcystis stand out as vectors of ARGs. In the context of One Health, it is essential to implement sound public policies and strict regulations on the use of antibiotics in aquaculture, and the use of monitoring tools such as environmental DNA (eDNA) and metagenomics allows for the early detection of ARGs, contributing to the protection of human, animal and environmental health.

Y. enterocolitica is a cold-tolerant, foodborne pathogen that poses a significant risk to public health, with pigs identified as its main reservoir. This review explores the current knowledge on the epidemiology, transmission, and virulence of Y. enterocolitica in pigs, highlighting their central role in spreading the bacterium to humans—primarily through the consumption of raw or undercooked pork. The pathogen is frequently found in pig tonsils and intestines and can contaminate meat during slaughter. Among the various strains, bioserotype 4/O:3 is the most common cause of human illness. Y. enterocolitica carries a diverse set of virulence genes, such as ail, yst, inv, and yad, and evades immune responses. The review also covers major outbreaks, risk factors on farms and in slaughterhouses, and the limitations of current surveillance systems. Reducing the impact of Y. enterocolitica requires a One Health approach linking animal health, food safety, and public health.

Canine otitis externa is a common and recurrent ear infection in dogs, often caused by bacterial pathogens, and complicated by increasing antimicrobial resistance. The analysis of bacterial isolates from dogs with otitis externa revealed a predominance of Staphylococcus pseudintermedius, representing 41% of all cases, followed by Staphylococcus aureus (23%), and Pseudomonas aeruginosa (19%). Other less frequently isolated organisms included Escherichia coli, Streptococcus canis, and Proteus mirabilis. These results highlight the significant role of S. pseudintermedius in the pathogenesis of otitis externa in dogs, as well as the relevance of Gram-negative opportunistic pathogens like P. aeruginosa, which exhibits the highest recurrence rate, with 90% of the cases associated with highly resistant to β-lactams (93% for amoxicillin–clavulanic acid; >70% for third-generation cephalosporins). P. mirabilis showed complete resistance to tetracycline, partial resistance to doxycycline, and reduced susceptibility to carbapenems, nitrofurantoin, and polymyxin B. S. canis exhibited limited resistance to erythromycin and clindamycin, while S. epidermidis displayed extensive multidrug resistance, including β-lactams, fluoroquinolones, sulfonamides, and polymyxins. These findings highlight the high prevalence of multidrug-resistant pathogens in canine otitis externa, emphasizing the need for culture-guided therapy and raising concerns regarding One Health, due to potential zoonotic transmission and dissemination of genetic determinants of antimicrobial resistance.

This study aimed to assess the emergence and/or re-emergence of Tick-borne Diseases (TBD) in Portugal by linking the hemoparasite burden in companion animals to vector-borne disease dynamics through a One Health approach. Between 2015 and 2024, 1169 clinically suspected animals with hemoparasite infections, treated at the Hospital Veterinário de Santarém (HVS), underwent serological confirmation for Rickettsia conorii, Babesia canis, Ehrlichia spp., and Haemobartonella spp. A total of 3791 serological tests (3.2 tests per animal) were performed and 437 animals tested positive for at least one of the four hemoparasites under investigation. From 2020 to 2024, tests nearly tripled from 894 to 2883, raising positive cases and prevalence from 29.5% to 39.9%, especially for rickettsiosis and hemobartonellosis, indicating an increased circulation of their vectors. A national vector surveillance initiative identified Hyalomma spp., Rhipicephalus sanguineus, Ixodes ricinus, and Dermacentor sp. as primary tick vectors in Portugal for the hemoparasites mentioned above and for other agents like arbovirus, such as Crimean-Congo Hemorrhagic Fever Virus (CCHFV) and tick-borne encephalitis virus (TBEV). This study found that the vectors responsible for transmitting hemoparasitosis, given the high number of serologically positive cases detected in the HVS, represent an increasing risk for TBD. These findings highlight the relevance of companion animal monitoring as an early-warning component within a One Health surveillance approach.

Q fever, caused by Coxiella burnetii, is a globally distributed zoonotic disease with significant public health and veterinary relevance, yet its epidemiology in Portugal remains fragmented. This systematic review aimed to assess the epidemiology of C. burnetii infection and Q fever in Portugal by compiling, critically analysing and integrating available evidence from animal, human, and environmental studies, adopting a One Health perspective. A comprehensive literature search was conducted in international databases and national repositories in accordance with PRISMA 2020 guidelines. Studies reporting serological, molecular or isolation-based detection of C. burnetii in humans, animals or environmental samples were eligible. A total of 24 studies were included, covering human populations, ruminants, companion animals, wildlife and environmental matrices. Evidence was predominantly focused on ruminants, with consistently high and heterogeneous levels of exposure reported across different species, regions and production systems. Human epidemiological studies were limited and largely restricted to occupational groups and blood donors, but consistently indicated substantial exposure, suggesting underdiagnosis and underreporting. Data on companion animals, wildlife and environmental sources were scarce and methodologically heterogeneous. This review confirms endemic circulation of C. burnetii in Portugal, but highlights pronounced geographic and methodological gaps, reinforcing the need for harmonised, integrated One Health surveillance to improve risk assessment and evidence-based prevention strategies.