Background Aleutian mink disease virus (AMDV) causes major economic losses in fur-bearing animal production. The control of most AMDV outbreaks is complex due to the difficulties of establishing the source of infection based only on the available on-farm epidemiological data. In this sense, phylogenetic analysis of the strains present in a farm may help elucidate the origin of the infection and improve the control and biosecurity measures. Objectives This study had the following aims: characterize the AMDV strains from most outbreaks produced at Spanish farms between 2012–2019 at the molecular level, and assess the utility of the combined use of molecular and epidemiological data to track the possible routes of infection. Methods Thirty-seven strains from 17 farms were partially sequenced for the NS1 and VP2 genes and analyzed phylogenetically with other strains described worldwide. Results Spanish AMDV strains are clustered in four major clades that generally show a good geographical correlation, confirming that most had been established in Spain a long time ago. The combined study of phylogenetic results and epidemiological information of each farm suggests that most of the AMDV outbreaks since 2012 had been produced by within-farm reservoirs, while a few of them may have been due to the introduction of the virus through international trade. Conclusions The combination of phylogenetic inference, together with epidemiological data, helps assess the possible origin of AMDV infections in mink farms and improving the control and prevention of this disease.

Porcine circovirus type 2 (PCV2) is the aetiological agent of PCV2-Systemic Disease (PCV2-SD) and PCV2-Subclinical Infection (PCV2-SI). PCV2 is highly resistant to environmental conditions, being able to remain in the farm environment and thus represent a risk for infection maintenance. The aim of this study was to identify, under field conditions, the possible critical points in the environment of non-vaccinated farrow-to-weaning swine farms where PCV2 could accumulate and persist. For that, environmental samples from five swine farms with PCV2-SD or PCV2-SI were taken and analysed by qPCR, including different farm areas, farm personnel and management implements. PCV2 DNA was detected in the environment of all farms (42.9% of positive samples). Overall, the PCV2-SD herd seemed to present more positive samples and higher viral loads than the PCV2-SI herds. At individual farm level, weaning areas appeared to be the most contaminated facilities. In addition, PCV2 was found at high levels in most samples from farm workers, especially work boots, suggesting that they may play a role in within-farm transmission. In addition, PCV2 was detected in areas without animals the like warehouses, offices and farm perimeter. Therefore, this study is helpful to improve measures to reduce within-farm PCV2 dissemination.

Air and surfaces of swine farms are the two alternative samples to obtain information about the health status of the herd. The aim of this study was to assess air and surface sampling for the detection of porcine circovirus type 2 (PCV2) in vaccinated and unvaccinated fattening farms, studying the relationship between the viral load in these samples with the viremia at herd level. Three swine fattening batches (one unvaccinated; two vaccinated) were monitored at 10, 12, 14, 16 and 18 weeks old; at each stage, blood, air and different surfaces were sampled and analysed by qPCR. In all herds, PCV2 was detected in all types of samples. Whenever viremia was detected, PCV2 was also detected in air and surface samples, even in those cases with a low estimated prevalence (1.6%); moreover, in two out of the three herds, PCV2 was detected in air and surface samples earlier than in the blood of the sampled population. In addition, a good correlation between the viremia of pig population and the PCV2 load in air and surface samples was found in both cases (τ = 0.672 and 0.746, respectively; p <0.05). These results show that air and surface samples could be useful tools to monitor PCV2 infection, being suitable for detecting the virus in cases of low prevalence and even before pigs develop viremia; therefore, these sampling techniques would speed up the implementation of the required measures to prevent productive and economic losses due to PCV2 infection.

Porcine Circovirus Type 2 (PCV2) and Mycoplasma hyopneumoniae are economically important pathogens in swine farms. Vaccination is the main preventive measure for both infections. In order to test two ready-to-use bivalent vaccines, 646 piglets from a herd actively infected with both pathogens were stratified according to the sow parity number and randomly assigned to three groups: A and B were vaccinated with two different vaccines, respectively, while C remained as the unvaccinated control. Vaccine efficacy was assessed based on the weight, average daily weight gain (ADWG), degree of lung lesions, presence of PCV2 viremia by qPCR and presence of PCV2 and M. hyopneumoniae antibody levels by ELISA. Our data revealed that the sow parity did not influence the vaccine outcomes. Good results for most of the analyzed parameters were observed in both vaccinated groups. ADGW and final weight were higher and lung lesions were less evident in both vaccinated groups than in the control one, but only Group A showed a significant improvement. PCV2 viremia was not detected in Group A, but it did appear in Group B coinciding with its peak in Group C. Finally, both the PCV2 and M. hyopneumoniae serological patterns differed depending on the employed vaccine.

Enterotoxigenic Escherichia coli (ETEC) is one of the major pathogens involved in neonatal calf diarrhoea (NCD) causing high economic losses in dairy farms. Antibiotic treatment is common in cases of systemic illness caused by NCD, but antimicrobial susceptibility tests (AST) are usually not performed. Thus, the aim of this study was to characterize the antimicrobial susceptibility of ETEC strains obtained from calves with diarrhoea between 2018–2020. Faecal samples (n = 420) were analyzed to detect the typical ETEC virulence factors F5 and STa. Positive samples were cultured to identify and isolate ETEC strains (n = 41) and ASTs were performed. Our results are alarming since ETEC strains resistant to three or more families of antimicrobials were detected in all isolates. Only four antibiotics (ceftiofur, cefoperazone, cefquinome and gentamicin) presented efficacy against more than 90% of the ETEC strains, while the other ten antibiotics were effective against less than 40% of the strains. In addition, a high number of strains were resistant to most first-line antimicrobials used in veterinary practice. For this reason, when ETEC infection is suspected, an AST must always be performed to select the most appropriate antimicrobial in each case and to avoid the emergence of new resistance mechanisms.