The Role of Histopathology as a Complementary Diagnostic Tool in the Monitoring of Bovine Tuberculosis

Proteomic analysis of granulomas from cattle and pigs naturally infected with Mycobacterium tuberculosis complex by MALDI imaging

Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) has recently gained prominence for its ability to provide molecular and spatial information in tissue sections. This technology has the potential to uncover novel insights into proteins and other molecules in biological and immunological pathways activated along diseases with a complex host-pathogen interaction, such as animal tuberculosis. Thus, the present study conducted a data analysis of protein signature in granulomas of cattle and pigs naturally infected with the Mycobacterium tuberculosis complex (MTC), identifying biological and immunological signaling pathways activated throughout the disease. Lymph nodes from four pigs and four cattle, positive for the MTC by bacteriological culture and/or real-time PCR, were processed for histopathological examination and MALDI-MSI. Protein identities were assigned using the MaTisse database, and protein-protein interaction networks were visualized using the STRING database. Gene Ontology (GO) analysis was carried out to determine biological and immunological signaling pathways in which these proteins could participate together with Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Distinct proteomic profiles between cattle and pig granulomas were displayed. Noteworthy, the GO analysis revealed also common pathways among both species, such as "Complement activation, alternative pathway" and "Tricarboxylic acid cycle", which highlight pathways that are conserved among different species infected by the MTC. In addition, species-specific terms were identified in the current study, such as "Natural killer cell degranulation" in cattle or those related to platelet and neutrophil recruitment and activation in pigs. Overall, this study provides insights into the immunopathogenesis of tuberculosis in cattle and pigs, opening new areas of research and highlighting the importance, among others, of the complement activation pathway and the regulation of natural killer cell- and neutrophil-mediated immunity in this disease.

Pathological findings and differential diagnoses of lymph node diseases in slaughtered cattle in Brazil: A study of 2000 samples

Slaughterhouse inspections play a crucial role in the sanitary control of zoonoses and foodborne diseases. This study aimed to identify and analyze the frequencies of lymph node diseases in cattle slaughtered for human consumption, using the samples sent to the anatomic pathology service of the Federal Laboratory for Agricultural Defense (Laboratório Federal de Defesa Agropecuária), Minas Gerais, Brazil, from January 2015 to September 2022. In total, 2000 lymph node samples were analyzed, and additional information was individually retrieved. Lesions were most frequently identified in thoracic lymph nodes. Bacterial isolation and quantitative polymerase chain reaction (qPCR) were performed using samples suspected of tuberculosis. Tuberculosis cases accounted for 89.3% of the samples. Histopathology was more sensitive than other ancillary tests for diagnosing tuberculosis. Paraffin-embedded tissues from lymphoma cases were subjected to immunophenotyping using anti-CD3 and anti-CD79a immunohistochemistry. Frozen and/or paraffin-embedded tissues from lymphoma cases were used to identify the enzootic bovine leukosis (EBL) retrovirus through qPCR. Other diagnoses included primary (T- and B-cell lymphoma) and metastatic neoplasms (squamous cell carcinoma, pulmonary adenocarcinoma, undifferentiated carcinoma, undifferentiated adenocarcinoma, undifferentiated sarcoma, undifferentiated round cell tumor, mesothelioma, hepatic carcinoid, meningioma, and seminoma), actinogranulomas (pyogranulomatous lymphadenitis [actinobacillosis and actinomycosis]), idiopathic lymphadenitis (neutrophilic and/or histiocytic, granulomatous, and suppurative), and miscellaneous nonspecific lymphadenopathies (depletion/lymphoid atrophy, lymphangiectasia, erythrocyte drainage, parasitic eosinophilic lymphadenitis, follicular hyperplasia, and toxic granulomatous lymphadenitis). The combination of histopathology with complementary techniques is important for successful diagnosis, especially in complex cases of high epidemiological, economic, and zoosanitary importance, such as tuberculosis and EBL.

Assessment of the diagnostic performance of intradermal tuberculin test and post-mortem inspection for the diagnosis of bovine tuberculosis according to WOAH guidelines

Bovine tuberculosis (bTB) constitutes a global challenge for public and animal health with still some deficiencies regarding its diagnosis. This study aimed to estimate the accuracy of the single intradermal tuberculin test (SIT) and post-mortem inspection for different diagnostic objectives following WOAH guidelines. Tissue samples from 59 microbiological culture/PCR-positive and 58 microbiological culture/PCR-negative cattle were evaluated. The diagnostic sensitivity and specificity, the positive and negative probability indices as well as the positive and negative predictive values (PPV and NPV) of each technique were estimated for different pretest probabilities. The SIT with strict interpretation demonstrated moderate precision in confirming the absence of infection in populations historically free of bTB, with a 12.1% rate of false positives, but also detecting positive animals in the early stage of the eradication programs, with a 13.6% rate of false negatives. The diagnostic performance for ruling out bTB was notably high (NPV > 90%) in animals with a pre-test probability (PTP) below 42%. Post-mortem inspection constituted an interesting alternative tool to confirm suspected and positive cases for SIT, particularly in areas with bTB prevalence exceeding 19%, where implementing SIT and eradication measures may be impractical. In these areas, the likelihood that animals with tuberculosis-like lesions are affected by the disease surpasses 90%. Similarly, in herds with a PTP below 25%, the absence of bTB could be confidently ruled out with over 90% certainty. These findings highlight the effectiveness of SIT and post-mortem inspection as valuable techniques for current eradication programs and controlling bTB in high-prevalence areas where molecular techniques may not be feasible.

Droplet digital PCR as alternative to microbiological culture for Mycobacterium tuberculosis complex detection in bovine lymph node tissue samples

Introduction

Bovine tuberculosis (bTB) caused by Mycobacterium tuberculosis complex (MTC) remains a significant concern for public health. Direct real-time PCR and droplet digital PCR (ddPCR) are proposed as alternative tools to enhance diagnostic precision and efficiency. This study aims to assess the diagnostic performance of a ddPCR assay targeting IS6110 for the detection of MTC DNA in both microbiological culture and fresh lymph node (LN) tissue samples obtained from cattle, in comparison with the established reference standard, the microbiological culture followed by real-time PCR.

Methods

The fresh LNs (N=100) were collected each from a different cattle carcass at the slaughterhouse. The limit of detection of ddPCR-IS6110 was set to 101 copies per 20 μl reaction.

Results

DdPCR-IS6110 detected 44 out of 49 reference-standard positive samples and yielded negative results in 47 out of 51 reference-standard negative samples, resulting in adjusted sensitivity (Se) and specificity (Sp) of 90.76% [95% confidence interval (CI): 82.58 - 98.96%)], and 100% (95% CI: 100%) respectively. The estimated adjusted false negative rate (FNR) was 9.23% (95% CI: 1.04 - 17.42%) and the false positive rate (FPR) was 0% (95% CI: 0%). When directly applied from fresh bovine LN tissues, ddPCR-IS6110 identified 47 out of 49 reference-standard positive samples as ddPCR-IS6110-positive and 42 out of 51 reference-standard negative samples as ddPCR-IS6110-negative, resulting in adjusted Se and Sp values of 94.80% [95% (CI): 88.52 - 100%] and 100% (95% CI: 100%), respectively. The adjusted FNR was 5.20% (95% CI: 0 - 11.50%) and the FPR was 0% (95% CI: 0%). Noteworthy, ddPCR-IS6110 disclosed as positive 9 samples negative to reference-standard.

Discussion

DdPCR-IS6110 proved to be a rapid, highly sensitive, and specific diagnostic tool as an alternative to reference-standard method.

Monitoring the immune response of macrophages in tuberculous granuloma through the expression of CD68, iNOS and HLA-DR in naturally infected beef cattle

Bovine tuberculosis still represents a universal threat that creates a wider range of public and animal health impacts. One of the most important steps in the pathogenesis of this disease and granuloma formation is the phagocytosis of tuberculous bacilli by macrophages. Mycobacteria replicate in macrophages, which are crucial to the pathophysiology of mycobacterial infections; however, scarce information is available about the dynamics of the granuloma-stage immunological response. Therefore, immunohistochemistry was used in this work to evaluate the expression of CD68, iNOS, and HLA-DR in different stages of TB granulomas from naturally infected cattle with tuberculosis. Two thousand, one hundred and fifty slaughtered beef cattle were examined during the period from September 2020 to March 2022. Sixty of them showed gross tuberculous pulmonary lesions and samples were collected from all of them for histopathological examination, Ziehl-Neelsen (ZN) staining, and bacteriological culturing. Selected samples that yielded a positive result for ZN and mycobacterial culturing were subjected to an immunohistochemical study of CD68, iNOS, and HLA-DR expression by macrophages according to granuloma stages. Immunohistochemical analysis revealed that the immunolabeling of CD68+, iNOS+, and HLA-DR+ macrophages significantly reduced as the stage of granuloma increased from stage I to stage IV (P < 0.003, P < 0.002, and P < 0.002, respectively). The distribution of immunolabeled macrophages was similar for the three markers, with immunolabeled macrophages distributed throughout early-stage granulomas (I, II), and surrounding the necrotic core in late-stage granulomas (III, IV). Our results suggest a polarization to the pro-inflammatory environment and increased expression of CD68+, iNOS+, and HLA-DR+ macrophages in the early stages of granulomas (I, II), which may play a protective role in the immune response of naturally infected beef cattle with tuberculosis.

Wild Boars (Sus scrofa, L. 1758) from Castile and Leon Region (Spain): A Histopathology Survey

Wild boars are wild ungulates with a wide distribution in Europe, with a relevant role in wildlife and public health. In Spain, high (and sometimes artificial) densities of wild boars are responsible for several health problems. Regular surveys, with hunters' collaboration, are crucial to monitor these diseases. Histological analyses were performed for lung, liver, and kidneys from 72 wild boars (58 from Zamora, 16 from Palencia). Lungs were the most affected organs, mainly revealing parasitic pneumonia (34.7%). Hydropic, vacuolar, and other cellular changes (33.3%) and congestion (16.7%) were found in the liver, and only 30.6% of the wild boars presented no alterations in this organ. Regarding the kidney, non-purulent nephritis (22.2%) was the most common lesion. This study gives an overview of the health status of wild boar populations in Castile and León. Other laboratory analyses are needed to obtain definitive diagnoses of these lesions, reach other conclusions, or apply any mitigation strategies to protect animals' or consumers' health.