Trichomonas gallinae is a protozoan parasite of major concern in avian medicine, particularly in domestic pigeons ( Columba livia ). This study investigated the risk factors associated with the frequency of nitroimidazole resistance and T. gallinae prevalence in domesticated pigeons from Eastern Spain, kept for different competitions. A total of 220 pigeons from 11 lofts were sampled and examined by microscopy and culture, revealing a 63.6% infection prevalence. Genotyping identified genotype C as predominant, with occasional detection of genotype A, mixed A/C infections, and one isolate of Lineage III. In vitro susceptibility testing of 42 isolates showed a high prevalence (81%) of metronidazole resistance (MIC values ≥ 20 µg/ml), with minimum inhibitory concentrations (MICs) ranging from 5 to >100 µg/mL in 9/11 pigeon lofts examined. Resistance was significantly associated with the use of metronidazole and was more frequent in young and non-reproductive birds. Biannual treatments and the combination of ronidazole and dimetridazole at higher doses were associated with lower infection rates than monotherapies or annual treatments. No significant associations were found between resistance and environmental or loft management parameters, although poor hygiene and high bird density were common in lofts with resistant strains. These findings highlight the urgent need for regulated treatment protocols, improved biosecurity, and the development of alternative trichomonacidal agents to combat the emergence of drug-resistant T. gallinae in pigeon populations.

Ovine Respiratory Complex is a multifactorial disease involving interactions between pathogens, host factors, and environmental conditions. This study investigated associations between selected bacterial agents, including Mycoplasma ovipneumoniae infection and members of the Pasteurellaceae family, and clinical, auscultatory, ultrasonographic, and post-mortem findings in Lacaune fattening lambs. A total of 80 animals were evaluated using clinical examination, thoracic auscultation, ultrasonography, post-mortem assessment, bacteriological culture, and quantitative PCR (qPCR) for Mycoplasma ovipneumoniae. Associations between microbial detection and disease severity scores were analyzed. Mycoplasma ovipneumoniae was the most frequently detected organism (50%), followed by Pasteurella multocida (32.9%) and Trueperella pyogenes (27.8%). Detection of specific microorganisms was more frequently observed in animals with increased disease severity across multiple diagnostic modalities. Coinfection was identified in 60.8% of animals and was significantly associated with increased severity according to clinical, auscultatory, ultrasonographic, and post-mortem scores. These findings underscore the polymicrobial nature of ORC and emphasise the necessity of employing complementary diagnostic approaches for disease evaluation.

Trichomonas gallinae is a protozoan parasite of major concern in avian medicine, particularly in domestic pigeons (Columba livia). This study investigated the nitroimidazole susceptibility and T. gallinae occurrence in domesticated pigeons from Eastern Spain, kept for different competitions. A total of 220 pigeons from 11 lofts were sampled and examined by microscopy and culture, revealing 63.6% of infected birds. Genotyping identified genotype C as predominant, with occasional detection of genotype A, mixed A/C infections, and one isolate of Lineage III. In vitro susceptibility testing of 42 isolates showed a high occurrence (45.2%) of elevated metronidazole minimum lethal concentrations (MLC) values (MLC ≥40 μg/mL) ranging from 5 to >100 μg/mL in 9/11 pigeon lofts examined. MLC values were not associated with sex, age, or reproductive status. In contrast, higher IC₅₀ values were observed in isolates obtained from pigeons bred for Pica competitions, and metronidazole exposure was associated with higher MLC values compared with ronidazole. No significant associations were found between in vitro nitroimidazole susceptibility values and environmental or management parameters, although suboptimal hygiene and high bird density were common in lofts with strains with reduced susceptibility to metronidazole. The findings of this study underscore the urgent need to establish evidence-based therapeutic protocols, strengthen biosecurity measures, and promote the development of novel therapeutic alternatives for the control of avian trichomonosis, in order to mitigate the spread of T. gallinae strains resistant to currently available drugs in pigeon populations.