Lawsonia intracellularis is the etiologic agent of proliferative enteropathy, which causes diarrhea in several animal species, including swine. Serology can be used both to determine the prevalence of antibodies against a specific pathogen in a herd and to obtain the serological profile, which is used to determine the dynamics of infection in the herd. The objective of this study was to determine the serological profile and seroprevalence of anti-L. intracellularis antibodies in swine herds from intensive production regions of Minas Gerais, Brazil, and to identify the risk factors related to the herd-level seropositivity. A total of 2999 serum samples were collected for this cross–sectional study in the four major regions of intensive swine production in Minas Gerais, Brazil. To obtain better estimates and increase the external validity of the seroprevalence, the sample data were weighted based on the pig population of each herd, the stratum in which the herd was classified and the swine population of the region where each herd was located. A questionnaire was used to identify potential risk factors related to this herd-level seropositivity. The overall weighted prevalence in Minas Gerais was 34.7 % (95 % confidence interval: 32.12 - 37.20 %), and there was no significant difference among the sampled regions, with the seroprevalence rates ranging between 32.06 and 37.66 %. Finishing pigs were the most prevalent among the sampled categories. Among the evaluated risk factors, “cleaning before disinfecting” had a negative impact in the seroprevalence (p < 0.05) and was considered a protective factor. The anti-L. intracellularis antibodies were detected in all of the investigated herds in Minas Gerais, which indicated a wide distribution of the agent in the state. The predominant serological profile was consistent with the dynamics of infection previously observed in pig herds in other countries with similar antimicrobial usage, in which the nursery pigs usually show the lowest seroprevalence and the finishing pigs exhibit the highest. Herds that adopt the practice of “cleaning before disinfection” can decrease their L. intracellularis antibody seropositivity.

Lawsonia intracellularis is an obligate intracellular bacterium which cannot be cultured by conventional bacteriological methods. Furthermore, L. intracellularis needs enriched medium and a unique atmosphere for isolation, cultivation and propagation. Because of this,there are only a few isolates of L. intracellularis available and few studies in vitro demonstrating the susceptibility of this bacterium to antimicrobial agents. The objectives of this study were to isolate South American and Southeast Asia strains of L.intracellularis and to determine the in vitro antimicrobial activity against these isolates. Tested antimicrobials included: chlortetracycline, lincomycin, tiamulin, tylosin and valnemulin(against both Brazilian and Thailand strains) and additionally, amoxicillin, zinc-bacitracin, carbadox, enrofloxacin, gentamicin, sulfamethazine, trimethoprim, spectinomycin and a combination (1:1) of spectinomycin and lincomycin were also tested against the Thai isolates. The minimum inhibitory concentration (MIC) was determined by the antimicrobial activity that inhibited 99% of L. intracellularis growth in a cell culture as compared to the control (antimicrobial-free). Two strains from Brazil and three strains from Thailand were successfully isolated and established in cell culture. Each antimicrobial was evaluated for intracellular and extracellular activity. Pleuromutilin group (valnemulin and tiamulin) and carbadox were the most active against L. intracellularis strains tested. Tylosin showed intermediate activity, chlortetracycline had variable results between low and intermediate activity, as well as spectinomycin, spectinomycin and lincomycin, amoxicillin, sulfamethazine and enrofloxacin. L. intracellularis was resistant to lincomycin, gentamicin, trimethoprim, colistin and bacitracin in in vitro conditions. This is the first report of isolation of L. intracellularis strains from South America and Southeast Asia and characterization of the antimicrobial susceptibility patterns of these new strains.

Brachyspira hyodysenteriae and Lawsonia intracellularis coinfection has been observed in the diagnostic routine; however, no studies have evaluated their interaction. This study aimed to characterize lesions and possible synergisms in experimentally infected pigs. Four groups of piglets, coinfection (CO), B. hyodysenteriae (BRA), L. intracellularis (LAW), and negative control (NEG), were used. Clinical signals were evaluated, and fecal samples were collected for qPCR. At 21 days post infection (dpi), all animals were euthanized. Gross lesions, bacterial isolation, histopathology, immunohistochemistry, and fecal microbiome analyses were performed. Diarrhea started at 12 dpi, affecting 11/12 pigs in the CO group and 5/11 pigs in the BRA group. Histopathological lesions were significantly more severe in the CO than the other groups. B. hyodysenteriae was isolated from 11/12 pigs in CO and 5/11 BRA groups. Pigs started shedding L. intracellularis at 3 dpi, and all inoculated pigs tested positive on day 21. A total of 10/12 CO and 7/11 BRA animals tested positive for B. hyodysenteriae by qPCR. A relatively low abundance of microbiota was observed in the CO group. Clinical signs and macroscopic and microscopic lesions were significantly more severe in the CO group compared to the other groups. The presence of L. intracellularis in the CO group increased the severity of swine dysentery.

Canine mammary tumors (CMTs) are the most diagnosed neoplasms in dogs; however, there are few studies analyzing the influence of epidemiological, clinicopathological, and histopathological data on cancer‐specific survival (CSS), disease‐free interval (DFI), and overall survival (OS) in a large cohort. To contribute to the understanding of the biological behavior of this neoplasm, 385 cases were analyzed, 89% malignant, 4% benign, and 7% non‐neoplastic lesions. Among the dogs diagnosed with malignant neoplasms, 86% had early clinical stages (I–III), while 14% had regional or distant metastasis at the time of diagnosis. Carcinoma in a mixed tumor was the most frequent histological type with 44% of the cases and had the best prognosis. Analyzed factors such as the presence of pseudocyesis, previous history of the disease, advanced clinical stage (IV‐V), and presence of ulceration obtained significant results for CSS, DFI, and OS through univariate analysis and had a negative impact on the survival of the patients. Multivariate analysis showed that histological grading and age proved to be the best independent parameters for the prognostic evaluation of CSS and DFI in this study. These factors were also significant in the overall survival analysis. Therefore, these parameters should be considered valuable risk and prognostic factors for CMTs.

Nodular lung lesions in swine are frequently due to abscesses or granulomatous pneumonia. Although tumours are rarely reported in modern pig farming, they should be considered as a differential diagnosis when nodular lung lesions are found. A first-parity sow exhibiting respiratory signs was euthanized. Several whitish firm nodules, not encapsulated, ranging in diameter from 0.5 to 5 cm were present in all lung lobes. Microscopically, the nodules were composed of dense neoplastic cells, mainly in Antoni types A and B patterns, infiltrative and with development of emboli. All neoplastic cells stained positively by immunohistochemistry for vimentin and S-100 protein, with variable immunostaining for glial fibrillary acidic protein and stained negative for cytokeratin. Based on the gross, histological and immunohistochemical features, the tumor was diagnosed as malignant peripheral nerve sheath tumour.