Claudio Severo Lombardo Barros

RESUMO: Este artigo descreve a filosofia por trás do sistema de diagnóstico das doenças dos animais de produção, desenvolvido e consolidado ao longo das últimas seis décadas e atualmente aplicado na maioria dos laboratórios de diagnóstico veterinário no Uruguai, Brasil e Argentina. A origem desse modo de operação é complexa, envolvendo diversos eventos históricos, como o período pós-guerra, mudanças de governo, ditaduras e crises econômicas, além das contribuições de instituições e pessoas. Sem dúvida, o surgimento de patologistas brilhantes entre as décadas de 1950 e 1970 foi decisivo nesse processo. Curiosamente, vários laboratórios de diagnóstico reconheceram a importância de integrar o trabalho de campo à prática laboratorial, transformando essa interação em um estilo de vida e em uma ferramenta crucial para enfrentar os desafios sanitários dos produtores. O resultado foi a criação de um sistema misto de entrada de casos, caracterizado pela investigação ativa por meio de visitas recorrentes ao campo e pela recepção passiva de amostras enviadas por veterinários de campo. Além disso, métodos de diagnóstico modernos e robustos foram aplicados, fornecendo a base para publicações científicas de impacto e teses de pós-graduação. A patologia diagnóstica integra achados morfológicos dos exames anatomopatológicos a métodos laboratoriais complementares que aumentam a precisão diagnóstica. Esse enfoque consolidou uma identidade regional capaz de resistir e superar limitações de investimento em ciência veterinária básica e aplicada, sustentada por uma visão multidisciplinar e interinstitucional. Alguns princípios fundamentais orientaram a fundação dos laboratórios de diagnóstico veterinário: 1) capital humano especializado; 2) infraestrutura, veículos, equipamentos e técnicas diagnósticas modernas; 3) financiamento de longo prazo; 4) pesquisa voltada para a solução dos problemas reais dos produtores; 5) coleta e processamento contínuos de dados epidemiológicos; 6) intercâmbio permanente de técnicas e informações entre laboratórios de diagnóstico; e 7) participação ativa de pesquisadores dos laboratórios como orientadores em programas de pós-graduação, com envolvimento de estudantes de pós-graduação nas atividades diagnósticas. Esse modo de operação desencadeou uma reação catalisadora que transformou a trajetória da saúde animal nas últimas décadas, mesmo quando os princípios 2 e 3 não foram plenamente atendidos. Adaptado às condições da América do Sul, esse modelo permitiu a construção de uma visão holística da saúde humana, animal e ambiental, fortalecendo a integração entre pesquisa, ensino, extensão, desenvolvimento científico e confiança nos serviços veterinários, tanto nos mercados internos quanto internacionais. O novo paradigma é que as futuras gerações de patologistas possam levar esse conhecimento adiante. Porque as vacas continuam no campo!

This article outlines the philosophy underlying the livestock diagnostic system that has been developed and consolidated over the past six decades and is now used in most veterinary diagnostic laboratories in Uruguay, Brazil, and Argentina. The origins of this approach are complex, having been shaped by historical circumstances such as the post-war period, political transitions, military dictatorships, economic crises, and the contributions of numerous institutions and individuals. The emergence of outstanding veterinary pathologists between the 1950s and 1970s played a decisive role in this process. Several diagnostic laboratories recognized the importance of integrating fieldwork and laboratory practice, making this interaction both a lifestyle and a crucial tool for addressing the health challenges of livestock. As a result, a mixed case-entry system was established, combining active investigation through regular field visits with the passive reception of samples submitted by field veterinarians. In parallel, modern and robust diagnostic methods were progressively incorporated, providing a strong basis for impactful scientific publications and postgraduate research. Diagnostic pathology combines morphological findings from anatomopathological examinations with laboratory methods to improve diagnostic accuracy. This systematic approach fostered the development of a regional identity capable of enduring, and often overcoming, the limitations imposed by restricted investment in basic and applied veterinary sciences. Such resilience was sustained by a multidisciplinary and interinstitutional perspective. Several fundamental principles guided the establishment of veterinary diagnostic laboratories: (1) the training and availability of specialized human resources; (2) adequate infrastructure, vehicles, equipment, and modern diagnostic techniques; (3) long-term and stable funding; (4) research oriented toward solving the real problems faced by livestock producers; (5) the continuous collection and processing of epidemiological data; (6) the constant exchange of diagnostic techniques and information among laboratories; and (7) the active participation of researchers as mentors in graduate programs, alongside the direct involvement of graduate students in diagnostic activities. Over the past decades, this approach has significantly transformed animal health in the region, even during periods when principles such as infrastructure and long-term funding were only partially fulfilled. Adapted to South American conditions, the model has enabled a holistic perspective on human, animal, and environmental health, strengthening the integration of research, teaching, extension, scientific development, and trust in veterinary services in both domestic and international markets. The emerging paradigm is that future generations of pathologists will carry this knowledge forward, because the cows are still in the field!

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Different tissues have a normal color spectrum that reflects their cellular composition and/or metabolic features. Similarly, distinct color variations may occur in tissues that have undergone pathologic or nonpathologic changes. Common examples of color changes in domestic animal tissues include red (associated with erythrocytes, hemoglobin, and myoglobin), brown (ferric hemoglobin or myoglobin, suppurative inflammation, lipid oxidation, postmortem autolysis, formalin fixation, neoplasms arising from cytochrome-rich tissues), yellow (hemoglobin and iron degradation, biliary pigment and by-products, carotenes, keratin, necrosis, suppurative or fibrinous inflammation), green (hemoglobin and iron degradation, biliary pigment and by-products, meconium, eosinophilic or suppurative inflammation, oomycete and algal infections), white (lack of blood, adipose tissue and its neoplasms, chylous effusion, necrosis, mineralization, fibrosis, lymphoid tissue, round cell neoplasms), translucent (transudate, cysts), black to gray (hemoglobin and iron degradation, melanin, carbon, tattoos), and blue to purple (poorly oxygenated blood, tattoos). Pathologists and pathology trainees can benefit from understanding why particular colors are present in a tissue or organ and are advised to recognize the color dynamics that occur over time, such as hemorrhage progressing from red to purple and subsequently to yellow, green, and brown. Therefore, clear and precise color recognition and description is a key feature of a gross examination. Understanding the relationship between color changes in tissues and the underlying biologic or pathologic processes can help elucidate disease recognition and diagnosis.

Botulism is a neuroparalytic disease caused by ingesting neurotoxins (BoNTs) produced by the anaerobic bacterium Clostridium botulinum. It is a significant cause of cattle mortality in Brazil. BoNTs block the release of acetylcholine at the neuromuscular synapses and cause muscle flaccidity. The diagnosis of botulism is challenging due to two main factors: the absence of macro and microscopic lesions and the difficulties inherent in laboratory tests considered the gold standard for botulism. Due to these difficulties, reviews of botulism diagnoses in Mato Grosso do Sul and extensively in the Center-West of Brazil became discrepant according to the diagnostic methodology used, making it difficult to correctly assess the disease’s prevalence, epidemiology, and clinical picture. This study aimed to review the diagnoses of botulism in cattle reported in Brazil, comparing the criteria used in each case. We studied the cause, the pathogenesis, clinical signs, and all the diagnosis methods applied to botulism. Based on the subject reviewed, we propose a diagnostic protocol based on standards adequate to the Brazilian circumstances. We also reviewed the critical diseases of cattle diseases to be included in the differential diagnosis of botulism.

We describe an outbreak of leishmaniasis in seven guinea pigs (Cavia porcellus) in which nodular ulcerated skin lesions of varying sizes were observed in the nasal cavity, upper lip, pinnae, vulva, and periarticular region of the limbs. Cytologic exam of collected samples of the lesions in the auricle of one of the animals revealed macrophages containing parasitophorous vacuoles of approximately 4.0μm in diameter in their cytoplasm with morphology suggestive of Leishmania sp. Although skin lesions spontaneously regressed in two of the Guinea pigs, only one survived. All six animals that died were necropsied. Grossly, all animals showed bloody nodular cutaneous lesions with crusts. One of the guinea pigs had distended dark red and firm lungs. Histopathology of the skin lesions revealed histiocytic interstitial acanthotic dermatitis associated with a myriad of Leishmania organisms within macrophages cytoplasm. In the lung, the lesions were characteristic of broncho-interstitial pneumonia with focal infiltrates of neutrophils, epithelioid macrophages, and multinucleated giant cells containing 2µm basophilic amastigotes with morphology compatible with Leishmania spp. A focal granulomatous lesion ,associated with the causal agent in the lung is a novel description of leishmaniasis in guinea pigs caused by L. enriettii. The polymerase chain reaction (PCR) technique with mini-exon primer performed in samples of lesions from two affected guinea pigs was positive and equal to the reference strain, identifying Leishmania enriettii. The cytological, macroscopic, and histological lesions associated with the PCR technique allowed the diagnosis of leishmaniasis and the identification of the specie L. enriettii.

This report describes 2 events of degenerative myelopathy in 4- to 27-day-old piglets, with mortality rates reaching 40%. Sows were fed rations containing low levels of pantothenic acid. Piglets presented with severe depression, weakness, ataxia, and paresis, which were more pronounced in the pelvic limbs. No significant gross lesions were observed. Histologically, there were degeneration and necrosis of neurons in the spinal cord, primarily in the thoracic nucleus in the thoracic and lumbar segments, and motor neurons in nucleus IX of the ventral horn in the cervical and lumbar intumescence. Minimal-to-moderate axonal and myelin degeneration was observed in the dorsal funiculus of the spinal cord and in the dorsal and ventral nerve roots. Immunohistochemistry demonstrated depletion of acetylcholine neurotransmitters in motor neurons and accumulation of neurofilaments in the perikaryon of neurons in the thoracic nucleus and motor neurons. Ultrastructurally, the thoracic nucleus neurons and motor neurons showed dissolution of Nissl granulation. The topographical distribution of the lesions indicates damage to the second-order neurons of the spinocerebellar tract, first-order axon cuneocerebellar tract, and dorsal column-medial lemniscus pathway as the cause of the conscious and unconscious proprioceptive deficit, and damage to the alpha motor neuron as the cause of the motor deficit. Clinical signs reversed and no new cases occurred after pantothenic acid levels were corrected in the ration, and piglets received parenteral administration of pantothenic acid. This study highlights the important and practical use of detailed neuropathological analysis to refine differential diagnosis.

Histopathology is an old science that is still currently utilized for disease diagnosis and research. The routinely processed histologic slides stained with hematoxylin and eosin are still used worldwide in most if not every histopathology laboratory. The technique is inexpensive, quick to perform, and allows the diagnosis of a fantastic variety of tissue changes and diseases. Skills in description and interpretation in histopathology are a craft that can be learned by repeatedly and systematically observing simple rules. In this article, we offer a few advices to help trainees in veterinary pathology at the start of their careers. Those advices are drawn from our experience in the diagnostic pathology routine and from the veterinary pathology literature. To enhance the understanding of these important steps in the histopathologic description of tissues, we decided to illustrate most concepts expressed here. We hope that our effort can add a bit to the development of future pathologists. Just like Alice, let us follow the White Rabbit into his burrow for this challenging experience!