In the complex conditions of intensive pig breeding, respiratory diseases remain a significant health and economic challenge, despite substantial progress in diagnostics and control measures. This study analyzes the pathoanatomical and histopathological changes in the respiratory organs of dead pigs from different production categories, as well as in clinically healthy fattening pigs inspected on the slaughter line. The research was conducted on a farrow-to-finish pig farm in southern Serbia without immunoprophylaxis against respiratory infections. A total of 182 animals were examined: 50 suckling piglets, 50 weaned pigs, 30 pre-fattening pigs, and 52 fattening pigs. Macroscopic and microscopic analysis of lungs, trachea, tonsils, and tracheobronchial lymph nodes revealed interstitial pneumonia predominated in young pigs categories (suckling and weaned), while older pigs (pre-fattening) showed purulent, fibrinous, and mixed broncho-interstitial pneumonia, often with pleural adhesions. Among fattening pigs, 82.7% showed no macroscopic lung changes. In cases of interstitial pneumonia, histology revealed type II pneumocyte hyperplasia, fibrosis, and inflammatory cell accumulation in the interstitium. Purulent bronchopneumonia exhibited neutrophilic granulocytes and epithelial desquamation, while fibrinous bronchopneumonia showed extensive fibrin deposits. Catarrhal inflammation of the trachea was most common in weaned pigs (38.0%), while tonsillitis occurred most frequently in suckling piglets (24.0%) and weaned pigs (28.0%). Reactive lymphadenitis in the tracheobronchial lymph nodes was highest in pre-fattening pigs (63.3%), suckling piglets (44.0%) and weaned pigs (40.0%). Although pathomorphological findings alone cannot confirm an etiological diagnosis, they guide further diagnostic investigations and emphasize the need for improved control, prevention, and diagnostic programs for respiratory infections in pigs.

Cytokinins, plant hormones derived from adenine, are best known for regulating growth and stress responses in plants. Recent findings suggest they may also influence microbial viability, yet their direct antimicrobial potential remains underexplored. This study evaluates the antimicrobial activities of four natural cytokinins (iPA, B, K, and p-T) and their N⁹-ribosides (iPAR, BR, KR, and p-TR) against selected human pathogens. Using the broth microdilution method, we assessed their effects on Gram-positive and Gram-negative bacteria, as well as fungal strains. While Gram-negative species showed no susceptibility, all tested compounds exhibited bacteriostatic activity against Bacillus subtilis and Enterococcus faecalis. Most notably, kinetin (K) and kinetin riboside (KR) displayed strong antifungal activity against Candida albicans, with MIC values comparable to the reference drug nystatin. Molecular docking studies supported these findings by showing that K and KR form favorable interactions with two validated antifungal targets in Candida albicans: secreted aspartic proteinase 3 (SAP3) and dihydrofolate reductase (DHFR). This is, to our knowledge, the first report linking natural cytokinins to direct antifungal action against C. albicans supported by in silico evidence. These findings highlight the potential of K and KR as promising leads for the development of cytokinin-based antifungal agents.

This study compared serological and molecular approaches for detecting Leptospira spp. using paired blood and urine samples from 124 asymptomatic stray dogs. Blood sera were screened via the microscopic agglutination test (MAT) for ten serovars. Urine samples were analyzed using four PCR assays: a commercial quantitative PCR (qPCR), a lipL32 qPCR, a conventional rrs PCR, and a multiplex PCR (mPCR). Serological exposure was detected in 26 (20.97%) dogs, while commercial qPCR, rrs PCR, lipL32 qPCR, and mPCR assays yielded positive results in 31 (25.00%), 34 (27.42%), 25 (20.16%), and 23 (18.55%) dogs, respectively. Compared with commercial qPCR, the lipL32 qPCR, rrs PCR, and mPCR demonstrated Positive Percentage Agreement (PPA) values of 80.65%, 87.10%, and 67.74%, and Negative Percentage Agreement (NPA) values of 100.00%, 92.47%, and 97.85%. Nineteen urine samples were positive across all four PCR assays. Overall, 42.74% (53/124) of dogs had at least one positive serological or molecular finding, including nine additional conventional PCR-positive findings without reliable sequence confirmation. Sequencing and phylogenetic analysis of 24 samples identified L. interrogans and L. borgpetersenii, representing the first molecular characterization of Leptospira in Bosnia and Herzegovina. The findings demonstrate the complementary value of serological and molecular approaches for Leptospira surveillance while emphasizing the need for cautious interpretation of unconfirmed molecular findings.

Surveillance of particularly dangerous infectious animal diseases relies on risk assessment, timely recognition of clinical suspicion, appropriate selection of animals and samples for testing, reliable laboratory diagnostics, and correct interpretation of results in relation to the epizootiological situation. Although diagnostic reliability is often associated primarily with the performance of the laboratory method used, the test result represents only the last step of a process that begins with clinical or pathological examination of animals and collection of relevant information needed to define the epizootiological context. The choice of animal, sample type, timing and method of sampling, sample identification, and storage and transport conditions directly affect the quality of laboratory results. Sample quality is therefore a key element of surveillance and of the effectiveness of the surveillance system. Sample quality should not be considered solely in terms of technical suitability for testing. Within surveillance systems, it also depends on the epizootiological justification for selecting a particular animal, selection of the appropriate sample type in relation to pathogen characteristics and disease pathogenesis, timing of sampling in relation to the stage of infection, sampling technique, quantity of material, preservation during storage and transport, and full traceability from the animal and holding to the laboratory result. A technically satisfactory sample collected from an inappropriate animal or at an inappropriate stage of infection may have limited diagnostic value. Also, epizootiologically appropriate selection of an animal does not ensure a reliable result if an unsuitable specimen is collected or managed improperly before testing. The relationship between disease pathogenesis, sample type, and sampling timing is particularly important. The presence and concentration of a pathogen in blood, secretions, excretions, tissues, or affected organs may change during various stages of infection. At the same time, a specific humoral immune response develops after a time lag and varies over time. Sample selection must therefore be aligned with the diagnostic objective: detection of the pathogen itself, its antigens or nucleic acids, or demonstration of a specific immune response. Within passive surveillance and when testing animals with clinical suspicion, priority should be given to animals in which the probability of detecting the pathogen by the recommended laboratory method is highest, including diseased, dead, or epizootiologically linked animals. In active surveillance, sampling must also meet requirements for representativeness of the target population and the planned surveillance design. In targeted risk-based surveillance, selection of animals, holdings or areas is directed by factors associated with increased probability of introduction, presence or spread of infection. In surveillance programs for enzootic diseases based on serological testing, animal selection and sampling timing must reflect the purpose of testing, such as assessment of population exposure, distribution of infection, immune status, or effects of applied measures. Interpretation may then also depend on animal age, vaccination status, and previous exposure to the pathogen. Inadequate sampling may be particularly important when highly analytically sensitive procedures are used. High analytical performance cannot compensate fully for deficiencies in a sample in which the target analyte is absent or present in insufficient quantity. Incorrect timing, inappropriate specimen type, insufficient material, dilution or contamination, degradation during transport, or substances that interfere with testing may reduce the probability of obtaining a reliable result. A result should therefore not be interpreted apart from sample type, timing of collection, clinical presentation and epizootiological information. This is particularly important when the laboratory finding is inconsistent with clinical, pathological or epizootiological findings supporting suspicion of disease or in the opposite case. Correct sample identification and traceability are also important determinants of surveillance quality. The link between the sample, animal, holding or other epizootiological unit, place and time of sampling, and the reason for sampling provides the basis for correct interpretation of the laboratory finding. A sample that cannot be reliably linked to its source may be assessed correctly from an analytical standpoint, but its value for epizootiological decision-making remains limited. The same applies to incomplete accompanying documentation, particularly when information on clinical status, morbidity, mortality, previous findings, vaccination, animal movements, or other circumstances influencing the probability of infection is missing. Storage, packaging, and transport are a follow-up of the sampling process rather than separate activities. Appropriate temperature conditions, the time from sampling to laboratory testing, prevention of leakage, cross-contamination and mechanical damage, and implementation of appropriate biosafety measures directly affect preservation of the diagnostic value of the sample. In the case of particularly dangerous infectious animal diseases, preventing dissemination of infectious material during handling of animals, samples and equipment is of particular importance. The outcomes of inadequate sampling surpass the need to repeat an individual laboratory test. A reduced probability of detecting infection due to poor sample selection or quality may delay disease confirmation, lead to an incorrect assessment of the health status of an animal or population, and delay implementation of control measures. In early detection systems, diagnostic delay may influence outbreak progression, allow continued spread of infection, and increase the scale of measures and resources required for control. Sample...