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Toxicity of rhizonin A, isolated from Rhizopus microsporus, in laboratory animals
Abstract:
Maize culture material of 25 isolates of the genera Rhizopus and Mucor caused deaths in day-old unsexed Pekin ducklings when fed as a 50% (w/w) mixture with duckling feed. Nine of these isolates were tested for toxicity in young inbred male BD IX rats, which were fed a mixture of 50% (w/w) culture material and rat feed. Only one isolate of Rhizopus microsporus was clearly toxic, causing 100% mortality in rats within 10 days. Growth in rats was reduced by adding culture material of this isolate to the feed in concentrations of 2.5, 5, 10 or 20% (w/w). The same isolate of R. microsporus was used to produce the mycotoxin rhizonin A. Pure rhizonin A was dissolved in dimethylsulphoxide and given to young male partially inbred albino rats by gavage in single doses of 70, 96, 131 or 180 mg/kg. The lowest dose exceeded the LD100. Evaluated by light microscopy, lesions in livers and kidneys were similar in rats fed culture material and in those intubated with rhizonin A. Hepatocytes showed changes ranging from degeneration to necrosis, the liver-tissue architecture was changed by disassociation of liver cell cords and there was periportal bile-duct proliferation. Renal tubular epithelium showed changes ranging from degeneration to necrosis.
Insights
Certain Rhizopus and Mucor fungal isolates from maize are toxic to ducklings and rats. One Rhizopus microsporus isolate produced the mycotoxin rhizonin A, causing liver and kidney damage in rats.
Area of Science:
- Mycology
- Toxicology
- Veterinary Pathology
Background:
- Fungal contamination of feed can pose risks to animal health.
- The genera Rhizopus and Mucor are common molds found in agricultural settings.
Purpose of the Study:
- To assess the toxicity of maize-associated Rhizopus and Mucor isolates in poultry and rodents.
- To identify specific toxic isolates and characterize the mycotoxin involved.
Main Methods:
- Feeding trials with day-old ducklings and young rats using 50% fungal culture material mixed with feed.
- Toxicity testing of a specific Rhizopus microsporus isolate in rats.
- Administration of purified rhizonin A to rats via gavage.
- Histopathological examination of liver and kidney tissues.
Main Results:
- Maize culture material from 25 isolates caused mortality in ducklings.
- One isolate of Rhizopus microsporus was highly toxic to rats, causing 100% mortality.
- Rhizopus microsporus culture material inhibited rat growth in a dose-dependent manner.
- Rhizonin A administration induced liver and kidney lesions, including hepatocellular degeneration/necrosis and renal tubular damage.
Conclusions:
- Specific isolates of Rhizopus and Mucor from maize possess significant toxicity.
- Rhizopus microsporus produces a mycotoxin, rhizonin A, responsible for observed toxic effects.
- Rhizonin A causes characteristic liver and kidney pathology in rats, highlighting its potential as a feed contaminant hazard.