Special Veterinary Pathology

OCHRATOXICOSIS

• Also known as “Mouldy nephrosis/nephropathy of swine” and “Citrinin toxicity” in ochratoxicosis several nephrotoxic mycotoxins, which are isocoumarin derivatives of phenylalanine, are involved
• These are prodced by species of Penicillium and Aspergillus, especially P. viridicatum and A. ochraceus
• In India, prevalence of A. ochraceus and ochratoxicosis has been widely reported
• Ochratoxin A is the most important toxin in natural poisonings in pigs and poultry
• Horses are suspected to suffer
• Dogs are especially susceptible to ochratoxin A experimentally, but natural poisoning has not been described
• The fungi can grow on a variety of animal feeds, including maize, oats wheat and barely
• The same fungi also produces another nephrotoxin, citrinin, which produces a similar syndrome in pigs and birds
• Citrinin is believed to contribute to nephropathy in pigs and birds, but does not appear to be the primary cause
• The important clinical signs are polydipsia (excessive thirst), polyuria (excessive urination) and dehydration
• Growth rate is significantly retarded

Lesions

• Lesions are restricted to the kidneys
• Grossly, kidneys are enlarged, grey yellow and firmer than normal
• Ochratoxin in pigs is particularly toxic to the proximal convoluted tubule
• Microscopically, epithelial cells lose their brush border and become shorter than usual, with enlarged vesicular nuclei
• Later, pyknosis and necrosis of the cells occur and cells may slough into the lumen
• Peritubular fibrosis occurs secondarily, which progresses until most of the kidney, including the glomeruli, are sclerotic (hard)
• These lesions have been reproduced in experimentally poisoned pigs
• Experimentally, ochratoxin is also nephrotoxic in dogs and chickens
• The effect is mainly on the proximal convoluted tubule
• In contrast to pigs, lesions also develop in other tissues in these species
• These include fatty change and focal necrosis of the liver, ulcerative enteritis and colitis and proctitis and necrosis of lymphoid tissues
• Ochratoxin is suspected to be a cause of abortion in cattle fed mouldy hay
• It is also suspected to cause fatal chronic nephropathy in humans