D. Catalano

Neurological signs associated with aflatoxicosis in Piedmontese calves

MYCOTOXINS are secondary metabolites produced by fungi, which may be developed under particular storage and environmental conditions. The principal mycotoxins affecting agriculture and livestock are aflatoxins, ochratoxins, trichothecenes, zearalenone and fumonisins; these agents may significantly affect public health and economies worldwide (Moss 1991). The toxicity of mycotoxins varies according to the livestock species affected. Ruminants are among the most mycotoxin-tolerant species, as the agents are partly degraded by the rumen microbiota (Hussein and Jeffrey 2001, Yiannikouris and Jouany 2002). In bovids, natural intoxication by fumonisin is rare, and toxicological studies on this mycotoxin have been mostly experimental (Osweiler and others 1993, Mathur and others 2001). Aflatoxins are among the most widely diffuse mycotoxins in foods and feedstuffs. In bovids, the prolonged consumption of contaminated feed has a negative impact on both production and reproduction (Dekman and Green 1992, Pier 1992, Hussein and Jeffrey 2001). By binding to macromolecules such as nucleic acids and nucleoproteins, aflatoxins cause a number of toxic effects such as mutagenesis, carcinogenesis, teratogenesis, reduced protein synthesis and immunosuppression (Hussein and Jeffrey 2001). The liver is the principal target organ of aflatoxicosis, and chronic intoxication induces lesions that are characterised by proliferation and fibrosis of the bile ducts accompanied by hepatocyte megalocytosis (Marcato 2002). This short communication describes the clinical, laboratory, macroscopic and histopathological findings relating to an outbreak of hepatic encephalopathy consequent to accidental intoxication by aflatoxin in Piedmontese calves. The affected farm housed 75 Piedmontese cows that were kept for the production of beef calves. Animals kept for reproduction were fed hay, while the beef calves were fed home-produced cornmeal for approximately four months. A clinical examination carried out on site identified six calves, aged six to 15 months, showing varying degrees of clinical signs; neurological signs of varying intensity had appeared 36 to 48 hours previously. Two animals (calves 1 and 2) were in lateral recumbency; physical examination revealed hypothermia and weight loss. Neurological examination showed a comatose mental status, characterised by the absence of response to any stimulus, including pain sensation. Generalised spinal hyporeflexia was also present, as well as dilated pupils and the absence of direct and consensual pupillary light reflexes. One of these animals showed myoclonus in the right forelimb. Blood samples and cerebro spinal fluid were collected from these two animals, which were euthanased and underwent postmortem examination. The remaining four animals showed signs of weight loss, dysorexia, ruffled coats and reduced ruminal activity. Neurological examination of each animal revealed a depressed mental status and compulsive behaviour characterised by anteropulsion and circling in large circles (Fig 1); hyperexcitability was also observed on occasion. The gait was slightly ataxic in all four animals, while the postural reactions were altered in one calf and slightly diminished in the other three. Spinal reflexes were normal, and evaluation of the cranial nerve reflexes revealed the absence of or reduction in the menace response of all four animals. Both direct and consensual pupillary light reflexes were normal. All four animals had a tendency to walk into objects, suggesting amaurosis. A blood sample was taken from one calf (calf 3) for analysis. The clinical signs were compatible with an intracranial prosencephalic localisation. On the basis of the history and clinical signs, differential diagnoses included inflammatory, toxicometabolic or degenerative pathologies. Haematology, blood chemistry analysis and electrophoresis of serum proteins was performed on the blood samples, and while waiting for the results of the diagnostic tests, the animals were administered a high dose (10 mg/kg) of intravenous vitamin B1. However, all four calves deteriorated and died within 48 hours. Calf 3 underwent postmortem examination. As the animals affected were only those that had consumed cornmeal, feeding with the cornmeal was discontinued. Hepatic, renal, encephalic and cervical spinal cord samples were taken during the postmortem examinations and fixed in 10 per cent buffered formalin. After embedding in paraffin, standard histological sections were stained with haematoxylin and eosin. The following areas of the central nervous system (CNS) were analysed: cervical spinal cord, medulla oblongata, pons, cerebellum, midbrain, thalamus, hippocampus, basal nuclei and cerebral cortex. Veterinary Record (2007) 160, 698-700

Comparison between light and electron microscopy in canine and feline renal pathology: a preliminary study.

The aim of this study is to compare the accuracy and clinical use of light and transmission electron microscopy in detecting the early stages of renal pathologies in domestic animals. We examined 30 samples of renal tissue from cats and dogs referred to the Veterinary Hospital of the Department of Animal Pathology for different systemic diseases. The progressions of the kidney pathologies were classified using the scheme system proposed by the International Renal Interest Society. All samples were submitted for conventional histology and ultrastructural examination. Our study shows that electron microscopy is necessary to complete the histological examinations, especially to define early stages of kidney diseases (minimal changes disease, epithelial tubular pathologies, tubular basement membrane and glomerular basement membrane changes). Electron microscopy can be more accurate in defining the level of focal lesion, and permits discrimination between different clinical and pathological alterations such as fibrillary deposits. In conclusion, transmission electron microscopy associated with clinical, histological, histochemical and immunological examinations, is an essential method for diagnosis and prognosis of renal disease.

Bovine cerebral theileriosis: Histological and ultrastructural investigations

Bovine cerebral theileriosis (BCT), or turning sickness is a clinical presentation of parasitic infections of cattle, caused by Theileria spp., that occurs sporadically in South Africa, Burundi, Uganda, Kenya and Tanzania. Clinical signs include circling, blindness, ataxia, opisthotonus and paralysis. The disease can be acute, subacute or chronic, and mainly affects animals between 3 and 5 years old. It is characterised by intense congestion and haemorrhages in the meninges and brain, encephalomalacia, and accumulation of parasitised lymphoblasts in cerebral blood vessels. Macroscopic, histological and ultrastructural lesions observed in 30 indigenous short-horn Zebu cattle from Northern Tanzania, aged 2–9-years-old, which presented characteristic neurological signs of a disease named “Ormilo” by local Maasai herders, were described. Brain smears, prepared from cerebral vessels and stained with Giemsa, revealed extensive lymphocytic infiltration associated with numerous schizonts. Histologically, areas of congestion and haemorrhage associated with obstruction of cerebral vessels with large numbers of parasitised lymphoblasts were the main lesions. Ultrastructural investigations demonstrated the presence of parasites morphologically comparable to flagellated protozoa inside lymphoid cells. This has never been described before in the end host (cattle), but only during the sexual stages within the gastrointestinal tract of ticks. PCR results showed positivity for Theileria taurotragi in 13 samples, suggesting that the parasite could be involved in the aetiology of Ormilo. The alternative hypothesis is that the parasite belongs to a different unknown protozoal genus, having an intra-lymphocytic phase, and being associated with infestation with Theileria spp. Further studies are needed to better understand the morphology of the parasite, its role in BCT, and its potential pathogenic importance for animals.