Mycotoxicosis

Mycotoxicosis due to incorporation of various mycotoxins in the feed is known in all farm animals, especially horses, but also has been described in pet animals such as in guinea pigs. Mycotoxins are toxic fungal metabolites that can contaminate a wide array of food and feed. In terms of agricultural and animal production, the most important mycotoxins are aflatoxins-AF (B1, B2, G1, G2), ochratoxin A (OTA), fumonisins (FB1, FB2), zearalenone (ZEA) and trichothecenes (deoxynivalenol-DON, T-2, HT-2).3 Mycotoxin-producing fungi can be classified into either field or storage fungi. Field fungi, such as the Fusarium species, produce mycotoxins on the crops in the field, whereas storage fungi, such as the Aspergillus and Penicillium species, produce mycotoxins on the crops after harvesting, both of which produce ochratoxin A carcinogenic toxin.3 Fusarium mycotoxins are capable of inducing both acute and chronic toxic effects.2 Rabbits are one of the most sensitive animals to toxins such as aflatoxins produced by Eurotium species. Aflatoxicosis in rabbits has been reported with aflatoxin B1 in feed. The rabbits affected show loss of coordination, loss of weight, and jaundice before death. Other aflatoxins affect viability of embryos and fertility.



Rabbit feed ingredients that constitute complete feed products are derived from different raw materials. Inadequate management of raw materials can lead to undesirable growth of fungi, leading to loss of nutritive substances and resulting in contamination by mycotoxins. Due to the modern agricultural methods, acute intoxications in livestock animals are rare, while subacute or chronic progression is more common. Fusarium toxins are the most important mycotoxins with regard to animal health. Ingestion of low to moderate amounts of Fusarium mycotoxins is common and generally does not result in obvious intoxication. However, these low amounts may impair intestinal health, immune function or pathogen fitness, resulting in altered host pathogen interactions and thus a different outcome of infection. For example, Fusarium mycotoxins worsens infections with parasites, bacteria and viruses, such as coccidiosis in poultry, salmonellosis in pigs, colibacillosis in pigs, necrotic enteritis in poultry, enteric septicemia of catfish, swine respiratory disease, as well as aspergillosis in poultry and rabbits.2

One of the main features of mycotoxicosis in rabbits is feeding reduction (about 20–60%) which causes a delay in growth. Young rabbits (aged 113 ± 20 days) with mycotoxicosis develop hair loss, erosions, crusts and necrosis in the tail area. These symptoms suggest chronic active dermatitis with granulation tissue formation. As rabbits are a coprophagic species, toxins in feces undergo a recycling process, which could enhance toxin resorption. In fact, high toxin levels were found in the feces in rabbits with clinical symptoms.1 In addition, fumonisin B1 toxin can cause multiorgan failure (kidneys, liver, lungs, heart, brain), reduction in the fetus weight and death due to diarrhea.

Rabbit tail dermatitis due to mycotoxicosis
Image source: Tail necrosis of one severely affected rabbit

References

  1. Dietary ergot alkaloids as a possible cause of tail necrosis in rabbits
  2. The Impact of Fusarium Mycotoxins on Human and Animal Host Susceptibility to Infectious Diseases





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