1. ¹Departamento de Especies productivas no tradicionales, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México (UNAM), México City, México
2. ²Departamento de Farmacología, Facultad de Medicina Veterinaria y Zootecnia, UNAM, México City, México
3. ³Departamento de Medicina Preventiva, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, México City, Mexico

Correspondence: Dr H Sumano, Departamento de Farmacología, Facultad de Medicina Veterinaria y Zootecnia, UNAM, México City 04510, México. E-mail: sumano@servidor.unam.mx

Received 21 July 2003; Revised 20 October 2003; Accepted 28 October 2003; Published online 2 December 2003.

Abstract

The major metabolite from the use of furazolidone (FZD) in mammals, birds and fish is 2,3-dihydro-3-cyanomethyl-2-hydroxy-5-nitro-1alpha, 2-di(2-oxo-oxazolidin-3-yl)iminomethyl-furo[2,3-]furan, also called 3-amine-2-oxazolidone (AOZ). A minor metabolite was identified as N-(5-amine-2-furfuryliden)-3-amine-2-oxazolidone (FOZ). To assess the potential carcinogenicity of FZD and the metabolic mixture of AOZ/FOZ, 11 mg FZD/kg feed/day was fed for 12 weeks to mollies (Poecilia formosa), an ornamental fish species prone to develop tumors. The rate of tumors was quantified and defined both in mollies and their offspring. Then, some fish was made into fishmeal and incorporated into fish food at 500 g of meal/kg of food and fed to other mollies for 12 weeks. The rate of tumors was assessed. A similar trial design was carried out in tilapia fish (Oreochromis niloticus) by adding 50 mg FZD/kg to the feed for 90 days. All animals were placed in glass fishponds under controlled laboratory conditions. Each week, a significant biomass was collected from both groups to assess the macroscopic and histopathological changes. All mollies developed melanohistiocytomic tumors in the liver and other organs. Offspring from surviving mollie females stimulated to breed showed no changes compared to control animals. None of the mollies fed with the mollie-meal food contaminated with AOZ/FOZ developed tumors. Neither tilapia medicated with FZD nor tilapia fed with tilapia-meal contaminated with AOZ/FOZ developed tumors. These results do not support the established viewpoint that FZD must be banned from trophic chains based on its potential carcinogenic properties.