Paulo Vargas Peixoto

Poisonous plants affecting livestock in Brazil

Plant poisoning, together with rabies and botulism, are the main causes of death in adult cattle in Brazil. Estimates indicate that about one million head of cattle die annually through plant poisoning in this country. There are approximately 75 plants of practical importance to animal husbandry that have had their toxicity confirmed by experiments with the animal species affected under natural conditions. The great majority of these plants only occur in Brazil and neighbouring countries. A few of them are forage plants that can become toxic under certain conditions. In this review the poisonous plants of interest to animal husbandry of Brazil are divided according to the clinical-pathological picture they cause in cattle; only cyanogenic plants, plants that cause nitrate/nitrite poisoning and the ones that cause oxalate poisoning, are grouped according to their toxic principles. Plants and their toxic principles, or of which possible toxic compounds have been isolated, are listed.

Estudos histológico, histoquímico e ultra-estrutural de fígados e linfonodos de bovinos com presença de macrófagos espumosos ("foam cells")

Samples of liver, kidney, spleen, and hepatic, mesenteric, retromandibular, prescapular and mediastinic lymph nodes, collected from 12 groups of cattle of different ages from the State of Mato Grosso, were studied. A total of 120 bovines was examined. According to their history, the animals were kept in pastures where Brachiaria decumbens and Brachiaria brizantha were the predominant plants. Grossly there was a yellowish liver which was more evident after 24 hr. fixation with formalin. Hepatic and mesenteric lymph nodes had normal size, however, on the cut surface there were whitish grooves, extending from the cortex to the medular, and multiple small white nodular areas in the medular. Beside these areas there were red, sometimes hemorrhagic, foci. Microscopically all animals had cells with foamy citoplasm in the liver and in the hepatic and mesenteric lymph nodes, often forming multinucleated cells. In the lymph nodes these infiltrates were adjacent to necrotic, hemorrhagic areas. In the liver the foamy cells were irregularly disseminated throughout the parenchyma or formed nodules around the central vein. These cells did not stain with PAS but weakly with oil red. Ultrastructurally foamy cells and hepatocytes showed negative images of crystals involved partially or totally by membranes. Mediastinic, retromandibular and prescapular lymph nodes of the same animals showed no gross and microscopic alterations.

Fotossensibilização hepatógena em eqüinos pela ingestão de Brachiaria humidicola (Gramineae) no Estado do Pará

Data on the clinical-pathological aspects and on the epidemioloy of a disease in horses, characterized by phototsensitization, which occurs in northeastern of Para, Brazil, are presented. Of a total of 40 horses examined clinically, post-mortem examination was performed on seven. Due to the characteristic lesions found on the non-pigmented skin, the macroscopic and histological alterations in the liver, and knowing that Brachiaria grasses contain saponins with toxic properties, which cause liver lesions and photosensitization in cattle and sheep, it is concluded that this disease in horses is caused by grassing exclusively Brachiaria humidicola.

Relação entre macrófagos espumosos ("foam cells") no fígado de bovinos e ingestão de Brachiaria spp no Brasil

To establish the etiological relationship and the appearance of foamy macrophages in the liver of cattle from tropical regions of Brazil, liver samples from the files of the Pathology Section of Embrapa-Projeto Sanidade Animal, Rio de Janeiro, were reviewed. A total of 55 liver samples of cattle which died from different causes between 1970 and 1991 were reexamined. Only samples of animals which grazed known pastures were reviewed. Foamy macrophages were not seen in the samples from 1970 to 1975, although 40 samples (72%) were from this period. Foamy macrophages were observed from 1976 on, coinciding with the introduction of Brachiaria decumbens from Australian seeds into Brazil. Some samples were from cattle with histories of photosensitization, which were at that time attributed to Pithomyces chartarum. The results of this study indicate that the liver changes are related to prolonged ingestion of Brachiaria spp.

Princípios de suplementação mineral em ruminantes

Muito embora ja haja um solido conhecimento sobre as deficiencias minerais e suas consequencias para a saude e a produtividade dos bovinos no Brasil, paradoxalmente, essas informacoes, na maioria das vezes, nao vem sendo empregadas pelos profissionais das ciencias agrarias, que persistem em estimular o uso generalizado das misturas minerais ditas completas. A deficiencia de diversos minerais incluidos nestes suplementos, como ferro, cromo, enxofre, entre outros, nao ocorre sob condicoes naturais ou so existe em raras situacoes muito particulares. O presente topico aborda os equivocos e problemas relacionados com a suplementacao mineral tradicionalmente feita e discute os principais aspectos da denominada suplementacao mineral seletiva, que e fundamentada no fornecimento exclusivo do(s) mineral(is) deficiente(s) e na(s) quantidade(s) necessaria(s). Essa alternativa pode permitir uma economia expressiva (por vezes, de ate 700%) em relacao a suplementacao mineral comercial normalmente utilizada. De acordo com diversas estimativas, a suplementacao mineral pode constituir de 20 a 30 % dos custos totais de producao de gado de corte criados em pastagens, dai a importância de diminuir esses gastos. Um ensaio de reversao, no qual um grupo de animais recebe a mistura mineral comercial rotineiramente utilizada na propriedade e outro grupo, o suplemento seletivo, e a melhor opcao para discriminar os efeitos (positivos ou negativos) entre dois esquemas de suplementacao mineral para uma especifica fazenda. Por esse ensaio, investigam-se, racionalmente e por um longo periodo, os efeitos das duas opcoes de suplementacao mineral em teste, com minimo risco de perdas economicas.

Intoxicação experimental por monofluoroacetato de sódio em bovinos: aspectos clínicos e patológicos

Sodium monofluoroacetate (MF) was identified, by cromatography, in three of the 12 plants that cause sudden death in cattle in Brazil, including Palicourea marcgravii, the most important plant of this group. A special kind of hydropic-vacuolar degeneration (HVD) of the distal convoluted uriniferous tubules was considered typical for the poisoning by some authors. The objective of this study was to verify if the ingestion of MF causes similar clinical signs and lesion in cattle poisoned by plants that cause sudden death. Six cows received orally 0.5 and 1.0mg/kg of M diluted in 50mL of distilled water. Clinically the animals presented tachycardia, engorgement and positive pulse of the jugular vein, abdominal breathing, swaying gait, subtle unbalance, and recumbency with head placed the on the flank. In the agonal phase all the animals in lateral recumbence presented muscular fasciculation, tonic contraction, peddling movements, opisthotonus, nystagmus, and died between 2 and 14 minutes. At postmortem examination, the heart auricles, jugular and pulmonary veins were moderately distended and engorged with blood. Slight to moderate edema of the subserosa was seen around the gall bladder and the duodenum near to the pancreas. At light microscopy, HVD associated with nuclear picnosis of the epithelial cells of the distal convoluted uriniferous tubules was present in all animals. Ultrastructurally, the cell lesion represents formation of cytosolic vacuoles, likely due to accumulation of water. Coagulation necrosis of individual or groups of hepatocytes and slight hepatic congestion secondary to the venous stasis were also observed. Hydropic-vacuolar degeneration has been observed in cases of poisoning by many substances, which cause acute tubular nephrosis, however not restricted to the distal renal tubules and without nuclear picnosis. This study demonstrates that the HVD in the kidney can be caused by MF and, in analogy, the compound should be considered responsible for the death of cattle that ingest toxic plants which cause sudden death in Brazil. Our results can be supportive to studies that will focus on the degradation of MF by rumen bacteria, what might have economic implications, as at least 500.000 cattle die annually by sudden death causing toxic plants in Brazil.

Intoxicação por antibióticos ionóforos em animais

The therapeutic use of ionophores in veterinary medicine has grown in the last years, with resultant increase in the risk of poisoning in animals. Ionophores are used as food additives as coccidiostacts in several animal species and growth promoter and bloat prevention in ruminants. The most often used ionophores are monensin, lasalocid, narasin and salinomycin. There is a great variation in the susceptibility to the toxic effect of ionophores in different animal species. Poisoning can occur when the dosage is too high or when not correct doses for a certain animal species are given. Cases of poisoning have been described in sheep, swine, horses, dogs and poultry. For horses ionophores are extremely toxic. The use of ionophores is only safe when used accordingly to the instructions of the manufacturer and especially for each animal species. In this paper the most important data regarding clinical-pathological and pathogenic aspects, and also the conditions in which the poisoning may occur are critically reviewed.

Estudo comparativo entre citopatologia e histopatologia no diagnóstico de neoplasias caninas

A comparative study between cytology and histopathology of various neoplasms from 150 dogs was carried out. Several staining methods including Wright, May-Grunwald-Giemsa, New-Methylene Blue and Papanicolau, and histological staining methods such as Hematoxilin & Eosin, van Gieson, Sudan, Toluidine Blue and Periodic Acid Schiff were used. The data obtained indicated an 85.3% accuracy for the cytological diagnosis when the histopathological diagnosis was considered as the correct parameter. In 4.0% of the cases only the embrionary origin of the neoplasms was determined, and in 1.3% only the prognosis was established. The cytological diagnosis differed from the histopathological diagnosis in 8.1% of the cases. In two cases (1.3%), although the cytological and histopathological diagnoses differed, a reexamination determined that the former was correct which increased its accuracy up to 86.6%. Fine needle aspiration biopsy proved to be the best technique to obtain samples for the study. Cytology was found not suitable for the diagnosis of mammary neoplasms due to the wide variation of the cytological aspects from different areas. The imprint on slides is a technique not recommended to evaluate mesenchymal tumors and should be replaced by exfoliative cytology. The Wright method proved to be the more efficient staining method. Adapted staining methods from histopathology such as van Gieson for leiomyomas and leiomyosarcomas, Sudan Black B for lipomas and liposarcomas, and Periodic Acid of Schiff and Toluidine Blue for mastocytomas, were especially useful in visualizing the fine morphological details of various epithelial and mesenchymal neoplasms examined.

Intoxicações experimental e natural por Ipomoea asarifolia (Convolvulaceae) em búfalos e outros ruminantes

Ipomoea asarifolia R. et Schult. is a plant responsible for occasional outbreaks of poisoning in cattle, sheep and goats. Its oral administration to cattle and buffalos showed that the buffalo is as susceptible as cattle. One to 4 daily doses of 10-20g/kg caused similar symptoms in both species, as incoordination, muscular twiching and swaying of the head and anterior part of the body (pendular movement). In buffaloes the signs of incoordination were observed to a smaller extent. There is no report yet on natural poisoning by I. asarifolia in buffaloes, possibly because cases are not being noticed.

Estudos experimentais com plantas cianogênicas em bovinos

These studies were performed in order to obtain additional data on Brazilian cyanogenic plants. Three animals, severely poisoned by Piptadenia macrocarpa (=Anadenanthera macrocarpa), recovered readily when treated intravenously with 660 mg/kg of sodium hyposulphite (sodium thiosulphate) plus 30 g dissolved in water given by stomach tube. Fresh leaves (in the sprouting phase), fed in October, were more poisonous than mature leaves fed in March. Dried leaves slowly lost their toxicity within a few months. Both the fresh and dried leaves of Piptadenia viridiflora showed similar toxic effects to P. macrocarpa. As this was also readily reversed by the administration of sodium hyposulphite in two animals, P. viridiflora can be included in the group of toxic cyanogenic plants. Four animals severely poisoned by the leaves of Holocalyx glaziovii (=Holocalyx balansae) also recovered readily after receiving sodium hyposulphite. The dried leaves of H. glaziovii also slowly lost their toxicity within a few months. Two animals severely poisoned by the leaves of Manihot glaziovii also recovered readily with sodium hyposulphite. However, dried leaves were no longer poisonous. The leaves of H. glaziovii and of M. glaziovii always gave a quick (in less than 5 minutes) positive reaction to the picrate test for cyanide. Those of P. macrocarpa and P. viridiflora reacted more slowly (after 15 and 10 to 30 minutes respectively) when in the sprouting stage, and even slower when the leaves were mature. The slower reactions seen with Piptadenia spp indicate a slower breakdown of the hidrocyanic glycosides and this also explains the longer course of poisoning seen in cattle fed these species. The dried leaves of Piptadenia spp and also of H. glaziovii gave slower reactions than the fresh leaves. These data permit the conclusion that the picrate test for cyanide is of relative value when evaluating the amount of cyanogenic glycosides in plants.