Production of fumonisins by Fusarium moniliforme and Fusarium proliferatum isolates associated with equine leukoencephalomalacia and a pulmonary edema syndrome in swine

Taxonomy, biology, and clinical aspects of Fusarium species

There are several taxonomic systems available for identifying Fusarium species. The philosophy used in each taxonomic system is discussed as well as problems encountered in working with Fusarium species in culture. Fusarium species are toxigenic, and the mycotoxins produced by these organisms are often associated with animal and human diseases. The implications for the association of the carcinogens, fumonisins, produced by Fusarium moniliforme and other Fusarium species with human diseases are discussed. Foreign-body-associated fusarial infection such as keratitis in contact lens wearers, onychomycosis, skin infections, and disseminated multiorgan infections are discussed. Disseminated fusarial hyalohyphomycosis has emerged as a significant, usually fatal infection in the immunocompromised host. Successful outcome is determined by the degree of immunosuppression, the extent of the infection, and the presence of a removable focus such as an indwelling central venous catheter. These infections may be clinically suspected on the basis of a constellation of clinical and laboratory findings, which should lead to prompt therapy, probably with one of the newer antifungal agents. Perhaps the use of such agents or the use of colony-stimulating factors may improve the outcome of this devastating infection. However, until new approaches for treatment develop, effective preventive measures are urgently needed.

Mycoflora of the toxic feeds associated with equine leukoencephalomalacia (ELEM) outbreaks in Brazil

The mycoflora of 39 feed samples associated with 29 Equine Leukoencephalomalacia (ELEM) outbreaks was studied from 1988 to 1990, in Brazil. Microbiological examination indicated Fusarium spp. as the most frequent mold which occurred in 97.4% of samples followed by Penicillium spp. in 61.5% and Aspergillus spp. in 35.9%. The moisture content of feed implicated in death of horses was above 15% which can favor the development of Fusarium spp. From the genus, F. moniliforme was the predominant species with an occurrence of 82.0%. Two additional species, not commonly associated with animal toxicosis, were isolated in low frequency, F. proliferatum (12.8%) and F. subglutinans (2.6%). It is important to emphasize that the isolation of F. proliferatum and F. subglutinans from feed obtained from the epizootic areas has not been documented previously in Brazil.

Occurrence of fumonisins B1 and B2 in corn and corn-based human foodstuffs in Italy

A survey has been carried out in Italy on the natural occurrence of fumonisins B1 (FB1) and B2 (FB2) in corn kernels from regional distributors and corn genotypes from breeding stations as well as in commercially available corn-based food products. All corn samples were fumonisin positive at levels up to 5310 ng/g for FB1 and up to 1480 for FB2. In corn-based foods, the highest fumonisin contamination levels were recorded in puffed (extruded) corn containing up to 6100 ng/g of FB1 and up to 520 ng/g of FB2. Levels ranging from 420 to 3760 ng/g FB1 and from 80 to 910 ng/g FB2 were detected in corn grits, corn flour or polenta (a sort of thick porridge made with corn flour). All sweet corn samples examined were positive for FB1, at levels varying from 60 to 790 ng/g FB1, but negative for FB2. Lower levels of fumonisins were found in other commodities, such as popcorn (up to 60 ng/g FB1 and 20 ng/g FB2), tortilla chips (up to 60 ng/g FB1 and 10 ng/g FB2), and corn flakes (10 ng/g FB1). These findings indicate a high degree of human exposure to fumonisins in Italy through the ingestion of commercially available corn-based foodstuffs.

Occurrence of Fumonisins B 1 and B 2 in Corn-Based Products from the Spanish Market

The natural occurrence of fumonisins B 1 and B 2 , the incidence of Fusarium organisms, and the capacity of Fusarium isolates to produce fumonisins were investigated with 50 corn-based samples from Spain destined for human consumption. Eight samples (16%) were found to be contaminated with fumonisins. The levels of contamination were very low, with a mean of 80 ng/g.

Fumonisin occurrence in corn from high- and low-risk areas for human esophageal cancer in China

Forty-seven corn samples were collected in 1989 from Linxian and Shangqiu Counties in Henan Province, the high- and low-risk areas, respectively, for human esophageal cancer in the People's Republic of China. The samples were analyzed for fumonisin (fumonisin B1 [FB1] and FB2) contamination. Of the fumonisin-positive samples, the mean levels in Linxian corn were found to be 872 ng/g for FB1 and 448 ng/g for FB2, while the Shangqiu corns had 890 ng of FB1 and 330 ng of FB2 per g. The incidence of fumonisin contamination of Linxian corn (48%) was about two times higher than that of Shangqiu corn (25%), and the former corn samples were frequently cocontaminated with trichothecenes. Fusarium species isolated from corn from Linxian County produced FB1 at levels ranging from 1,280 to 11,300 micrograms/g.

Temporal and dose-response features in swine fed corn screenings contaminated with fumonisin mycotoxins

Fumonisin B1 (FB1), a mycotoxin produced by Fusarium moniliforme and F. proliferatum, induces liver damage and pulmonary edema in swine. We examined the temporal and dose-response features of FB1 toxicosis in male weanling crossbred pigs fed nutritionally balanced diets, containing corn screenings naturally contaminated with fumonisins, for 14 days. Total fumonisins (FB1 and FB2) in diets 1 through 6 were assayed at 175, 101, 39, 23, 5, and < 1 ppm (below detectable concentrations), respectively. Clinical signs, serum biochemical alterations, and morphologic changes were evaluated. Pigs were weighed, and bled for hematologic and clinical chemistry evaluation on days 5 and 14. They were euthanized on day 14, or earlier if respiratory distress was observed. Respiratory distress developed in 3/5 pigs fed diet 1 between days 4 and 6 due to severe pulmonary edema and pleural effusion. Histologic evidence of hepatic injury was present in all pigs fed diets 1 and 2, 3/5 on diet 3, and 1/5 on diet 4. Serum bilirubin and cholesterol concentrations, gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and arginase (ARG) activities were elevated in pigs fed diets 1 and 2. Based on liver histopathology, the no observed adverse effect level (NOAEL) for fumonisin toxicity in swine was < 23 ppm total fumosins for the 14-day period. Based on regression analyses of the clinical chemistry profiles at 14 days, the NOAEL was < 12 ppm, with ALP being the most sensitive parameter. In conclusion, pulmonary edema occurred only at the highest fumonisin concentration (175 ppm), while liver damage occurred at much lower concentrations with a NOAEL of < 12 ppm.

Fumonisin-contaminated maize: physical treatment for the partial decontamination of bulk shipments

Ten maize samples, randomly selected from a bulk shipment imported into South Africa, were characterized by a wide distribution in particulate size. Following fractionation by sieving through a 3 mm screen, the 'kernels' (fractions > or = 3 mm) corresponding to between 80.0 and 95.3% of the samples by mass, were contaminated with total fumonisin levels of between 530 and 1890 ng/g. Conversely, those fractions termed 'fines' (< 3 mm) had significantly higher total fumonisin concentrations of between 12,340 and 27,460 ng/g, and accounted for between 4.7 and 20.0% of the samples by mass. The data indicated that removal of the 'fines' resulted in overall reductions in total fumonisin levels of between 26.2 and 69.4%. It is suggested that initial removal of 'fines' from bulk shipments of maize, prior to further processing, could be considered as a preliminary fumonisin-decontamination procedure.

Pharmacokinetic fate and pathological effects of 14C-fumonisin B1 in laying hens

Presence of fumonisin B1 (FB1), a major metabolite of Fusarium moniliforme, in corn is of great concern to both human and animal health because of its wide range of toxicity. The pharmacokinetics of FB1 was studied in laying hens following oral and intravenous administration of 14C-labelled FB1. After iv dosing (2.0 mg = 23.68 kBq/kg bw) plasma radioactivity underwent a very rapid bi-exponential decline (t1/2 alpha = 2.5 +/- 0.3 min; t1/2 beta = 48.8 +/- 11.2 min) with negligible levels measured after 4-6 hr. Mean value for the apparent volume of distribution at steady state (Vdss) was 18.27 ml/kg, apparent volume of central compartment (Vd beta) was 82.20 ml/kg and plasma clearance was 1.18 ml/min/kg. At 24 hr post-dosing only trace residues were present in liver, kidney, and cecum. When dosed by the oral route (2.0 mg = 47.36 kBq/kg bw), systemic absorption of fumonisin appeared to be poor (F = 0.71 +/- 0.5%) with peak plasma concentrations of only 40-145 dpm/ml (equivalent to 28-103 ng FB1 and/or metabolites per ml) between 1.5 and 2.5 hr. At 24 hr post-dosing only trace amounts were present in crop, liver, kidney, small intestine, and cecum. In both orally and iv dosed birds almost all (97.7 +/- 3.73%) of the radioactivity was recovered in excreta by the end of the 24 hr experiment period and no residues were found in eggs laid during the 24 hr post-dosing period.(ABSTRACT TRUNCATED AT 250 WORDS)

Levels of fumonisin B1 in corn naturally contaminated with aflatoxins

Aflatoxins and fumonisin B1 are hepatotoxic and carcinogenic metabolites produced by Aspergillus flavus and Fusarium moniliforme, respectively. These fungi are common natural contaminants of corn, and both aflatoxins and fumonisin B1 have been implicated as aetiological agents in animal and human diseases. To determine whether these mycotoxins co-exist on corn under natural conditions, 28 samples from the 1991 Georgia (USA) corn crop were assayed for (total) aflatoxin and fumonisin B1. 27 samples were positive for aflatoxin, 24 samples were positive for fumonisin B1, and 23 samples had detectable levels of both. In the positive samples, the mean aflatoxin concentration was 73 ppb (SD = 86), and the average fumonisin B1 concentration was 0.87 ppm (SD = 0.65). A correlation between aflatoxin and fumonisin B1 concentrations was not evident. None the less, these results demonstrate that exposure to both mycotoxins can occur simultaneously by consumption of co-contaminated corn.

Lymphocyte cytotoxicity and erythrocytic abnormalities induced in broiler chicks by fumonisins B1 and B2 and moniliformin from Fusarium proliferatum

Peripheral blood lymphocytes were isolated from broiler chicks that had ingested feed amended with autoclaved Fusarium proliferatum culture material containing fumonisin B1 (FB1), fumonisin B2 (FB2) and moniliformin. Lymphocyte viability was determined for birds that were placed on amended rations at day 1 or day 7 of age at three different levels of mycotoxins, ranging from 61-546 ppm FB1, 14-94 ppm FB2 and 66-367 ppm moniliformin. Reduction of the tetrazolium salt, MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide], to yield MTT formazan, based on mitochondrial metabolic activity, was used to assess cell viability. Lymphocyte cytotoxic effects were observed in all treatment groups on day 21; chicks that started on amended feed at day 1 of age were affected more than those that started at day 7. Abnormal erythrocytes resembling early stages of erythroblasts were observed in peripheral blood from test chicks. Abnormally shaped red cells (poikilocytes) having a spindle-shape with one or both ends pointed were present. Some red cells appeared to be undergoing mitosis. Both reduced lymphocyte viability and abnormal erythrogenesis occurred in chicks given feed amended with F. proliferatum culture material containing FB1, FB2 and moniliformin.

Mortality in broiler chicks on feed amended with Fusarium proliferatum culture material or with purified fumonisin B1 and moniliformin

Two hundred twenty-eight male chicks (Columbia x New Hampshire) were given feed amended with autoclaved culture material (CM) of Fusarium proliferatum Containing fumonisin B1 (FB1), fumonisin B2 (FB2) and moniliformin in 3 separate feeding trials. Purified FB1 and moniliformin were given separately and in combination in a fourth feeding trial. Birds were given amended rations at day 1 (Trial 1 and 4), day 7 (Trial 2), and day 21 (Trial 3) and their respective ration was given for 28 days (Trial 1), 21 days (Trial 2), 7 days (Trial 3), and 14 days (Trial 4). FB1 concentrations were 546, 193, and 61 ppm; FB2 were 98, 38 and 14 ppm; and moniliformin were 367, 193, and 66 ppm in the first 3 feeding trial regimens. Chicks in Trial 4 were given dietary concentrations of purified FB1 at 274 and 125 ppm, and moniliformin at 154 and 27 ppm. FB1 and moniliformin, both alone and in combination, produced dose-responsive clinical signs, reduced weight gains and mortality in chicks. Age of birds given amended feeds had little difference in the clinical response; however, those given the rations from days 7 or 21 were slightly less susceptible than those given rations beginning at 1 day of age. Additive effects were noted when the toxins were given in combination. When toxins were given separately, adverse effects took longer to occur. A system to monitor pattern and rate of defecation (RD) was developed for assessing the chicks' approach to feed, water and heat source as illness progressed. Our results indicate that chicks fed corn heavily infected with F. proliferatum under field conditions could suffer acute death similar to that described for 'spiking mortality syndrome' during the first 3 weeks of age.

Fumonisins

Fusarium moniliforme Sheldon is a common fungal contaminant of corn and produces a variety of mycotoxins. Among these are the recently discovered fumonisins, which are now known to cause certain animal diseases, namely leukoencephalomalacia in horses and pulmonary edema in swine. There is a significant association between their presence in corn and human esophageal cancer in southern Africa. Fumonisin B1 causes liver cancer in rats. Five other fumonisins--B2, B3, B4, A1 and A2, have been isolated; the last two are N-acetates of fumonisins B1 and B2 and do not appear to be toxic. Several other Fusarium species are now known to produce fumonisins. Procedures for detection and determination of fumonisins include thin layer chromatography, liquid chromatography (with fluorescence derivatization), post-hydrolysis gas chromatography, immunochemical assay, and mass spectrometry. In addition to their natural occurrence in corn-based animal feeds and in home-grown African corn used for food, fumonisins are frequently found in commercial corn-based foods. Fumonisins are moderately heat-stable. No effective detoxification process has yet been developed for use with fumonisin-contaminated feeds.

Fumonisins--mycotoxins produced by Fusarium moniliforme

Fumonisins are toxic metabolites of the fungus Fusarium moniliforme, which is a common contaminant of corn everywhere in the world. The fumonisins are carcinogenic in laboratory rats, and cause acute toxicity of domestic animals that mimics field cases of disease attributed to contamination of feed by F. moniliforme. These include both equine leukoencephalomalacia and porcine pulmonary edema. Fusarium moniliforme contamination of corn consumed by humans in certain areas of the world is associated with higher than average incidence of esophageal cancer, and fumonisins may be responsible. Analytical methods have been developed for fumonisins, but improvements are needed so that more accurate, less expensive, and more rapid assays of food and feedstuffs can be done. Fumonisins are structurally similar to sphingosine, and may exert their biological activity through their ability to block key enzymes (sphinganine- and sphingosine-N-acyltransferases) involved in sphingolipid biosynthesis. Much more research is needed to define the extent to which this mycotoxin adversely affects the food supply, and its involvement in animal and human diseases.

Biological action of mycotoxins

Mycotoxins are ubiquitous, mold-produced toxins that contaminate a wide variety of foods and feeds. Ingestion of mycotoxins cause a range of toxic responses, from acute toxicity to long-term or chronic health disorders. Some mycotoxins have caused outbreaks of human toxicoses, and at least one mycotoxin, aflatoxin B1, is a presumed human hepatocarcinogen. As part of a comprehensive effort to curtail the adverse health effects posed by mycotoxins, substantial research has been conducted to determine the mechanism of action of mycotoxins in animals. This review presents some of the current knowledge on the biological action of four diverse classes of mycotoxins--aflatoxin B1, tricothecenes, zearalenone, and fumonisin B1--with particular emphasis on mechanisms of action.

Isolation and purification of AAL-toxin from Alternaria alternata grown on rice

An isolation and purification procedure is described for AAL-toxin, a secondary metabolite produced by Alternaria alternata. The method involves growth of the fungus on rice media, extraction with chloroform followed by methanol: water from fungus-infested rice, and purification of the aqueous layer that contains AAL-toxin by using chromatography methods. The AAL-toxin was of type A, and white in color, and its purity was > or = 95% with mol. wt 522 (M + 1).

Biological activities of fumonisins, mycotoxins from Fusarium moniliforme, in jimsonweed (Datura stramonium L.) and mammalian cell cultures

Fumonisins A1, A2, B1, B2 and B3 are a series of mycotoxins produced by strains of Fusarium moniliforme. Fumonisins are hydroxylated long-chain alkylamines esterified with propanetricarboxylic acid moieties that represent approximately half the mol. wt of the toxins. The A-series fumonisins are N-acetylated, whereas the B series contains free amino groups. Hydrolytic removal of the propanetricarboxylic acid moieties from fumonisins B1 and B2 yields the corresponding aminopentols, AP1 and AP2, respectively. These compounds were tested for toxicity on widely differing bioassay systems, representing plant and animal systems. The plant bioassay system employed jimsonweed (Datura stramonium L.) leaves and leaf discs in which toxicity was detected as electrolyte leakage, photobleaching and quantitation of chlorophyll reduction. The animal bioassay system employed cultured mammalian cell lines in which toxicity was detected as inhibition of cell proliferation. Fumonisins B1, B2 and B3 at 50 micrograms/ml or less were effective toxins after exposure periods greater than 24 hr in all plant and animal bioassay systems examined, except 3T3 mouse fibroblasts, whereas fumonisins A1 and A2 exhibited little or no activity. However, the hydrolytic degradation products AP1 and AP2 exhibited toxicity similar to or greater than B-series fumonisins in all test systems, including substantial toxicity to 3T3 mouse fibroblasts.

Mycotoxins in review

The putative involvement of mycotoxins in human diseases, including cancer, is reviewed with reference to ergotism, citreoviridin toxicosis, alimentary toxic aleukia, stachybotryotoxicosis, Balkan endemic nephropathy and aflatoxicoses. Analytical and sampling problems in determining the occurrence of and exposure to mycotoxins are discussed against the background that over 300 mycotoxins have been identified, produced by some 350 fungal species, and that the potency of some of them demands the quantitation of extremely small quantities of analyte. Mycotoxins associated with food and originating from Alternaria, Aspergillus, Fusaria, Penicillia and Claviceps spp. are reviewed with reference to the toxicological, regulatory and economic issues arising. It is concluded that continued efforts are needed to: identify and quantify human/animal exposure; estimate health risks and make defensible risk-benefit judgements; develop sampling plans based on experimental observation; arrive at agreed regulatory levels based on legitimate sampling plans, analytical capabilities and economic considerations; develop procedures for disposal of contaminated lots; and develop plant varieties resistant to fungal invasion.

Production of the Mycotoxin Fumonisin B 1 by Alternaria alternata f. sp. lycopersici

The mycotoxin fumonisin B 1 , originally described as being produced by Fusarium moniliforme , was detected in liquid cultures of Alternaria alternata f. sp. lycopersici , a host-specific pathogen of tomato plants. The metabolite was detected by high-pressure liquid chromatography and mass spectrometry. Its identity was confirmed by fast atom bombardment and ion spray mass spectrometry, as well as parent-daughter tandem mass spectrometry. In three separate experiments, the concentrations found ranged between 5 and 140 ppm (μg/ml).

Heritability of fumonisin B1 production in Gibberella fujikuroi mating population A

Fumonisins are mycotoxins produced by strains belonging to several different mating populations of Gibberella fujikuroi (anamorphs, Fusarium section Liseola), a major pathogen of maize and sorghum worldwide. We studied the heritability of fumonisin production in mating population A by crossing fumonisin-producing strains collected from maize and sorghum in the United States with fumonisin-nonproducing strains collected from maize in Nepal. Random ascospore and tetrad progeny from three of these crosses were analyzed by gas chromatography-mass spectrometry and high-performance liquid chromatography for their ability to produce fumonisins on autoclaved cracked maize. In all three crosses, the ability to produce fumonisins, predominately fumonisin B1, segregated as a single gene or group of closely linked genes. Intercrosses between appropriate progeny and parents were poorly fertile, so we could not determine if the apparent single genes that were segregating in each of these crosses were allelic with one another. Mating type and spore-killer traits were scored in some crosses, and each segregated, as expected, as a single gene that was unlinked to the ability to produce fumonisins. We conclude that G. fujikuroi mating population A provides a powerful genetic system for the study of this important fungal toxin.

Occurrence of Fumonisin in Forage Grass in New Zealand

Fumonisin B 1 (FB 1 ) was isolated from samples of forage grass originating in paddocks associated with an idiopathic disease of Canadian wapiti and wapiti-red deer hybrids characterized by “ill thrift” and liver dysfunction. Four of 40 samples contained 1, 3, 6, and 9 ppm (micrograms per gram) of FB 1 and 4, 0.5, 2, and 0.5 ppm, respectively, of the methyl ester of FB 1 . Analyses were done by ion spray mass spectrometry and confirmed by both fast atom bombardment (solids probe) and mass spectral analysis by electron impact ionization of the trifluoroacetate derivative of the base hydrolyzed product (pentolamine) of FB 1 . This article contains the first report of the presence of fumonisin B 1 in grass.

Mycological condition of maize products

Maize and maize-related products were investigated in a collaborative study for viable moulds and antigenic extracellular polysaccharides (EPS) produced by Aspergillus and Penicillium species. In addition, the samples were tested for the presence of aflatoxin B1. All maize products, with the exception of the heat processed products, contained viable moulds on an average of (log10 values) 3.3 +/- 0.7 colony-forming units per gram. In most samples a mixed mould flora was present. Species of the genus Fusarium were dominant, followed by Aspergillus, Eurotium and Penicillium. The mould colony count correlated positively with the presence of antigenic extracellular polysaccharides produced by species of Aspergillus and Penicillium. Gamma irradiation did not affect the detection of antigenic extracellular polysaccharides. Aflatoxin B1 was detected in two out of 35 samples; these contained 0.6 and 0.8 microgram/kg. From one of these aflatoxin B1-containing samples, Aspergillus flavus was isolated.

A rapid, sensitive thin layer chromatography procedure for the detection of fumonisin B1 and B2

A thin layer chromatography (TLC) method was developed for the detection of fumonisin B1 and B2 in corn and corn-based feedstuffs. Finely ground samples were extracted with acetonitrile:water (1:1), filtered, and applied to C18 cleanup columns. The columns were washed with 1% aqueous KCl followed by acetonitrile: 1% aqueous KCl (1:9), and the fumonisins were eluted with acetonitrile:water (7:3). The eluants were concentrated and spotted on reverse-phase C18 TLC plates along with fumonisin B1 and B2 standards, and the plates were developed in methanol: 4% aqueous KCl (3:2). The fumonisins were visualized by spraying the TLC plates successively with 0.1 M sodium borate buffer, fluorescamine, and 0.01 M boric acid. The plates were then dried and examined under longwave ultraviolet light. Fumonisin B1 and B2 appeared as bright yellowish-green fluorescent bands at Rfs of 0.5 and 0.1, respectively. The detection limit for the fumonisins on the TLC plate was 0.1 ppm in corn. Recoveries from spiked samples averaged greater than 80%. The identification of the fumonisins was confirmed by hydrolyzing the parent compounds of B1 and B2 to their respective C22 amino-alcohols and reexamining by TLC with the same visualizing reagents. This procedure was used to survey 193 corn samples collected from University of Missouri test plots in 1990 for fumonisin B1. Fumonisin B1 was detected in 15% of the corn samples.

Fumonisin B1 production by Fusarium species other than F. moniliforme in section Liseola and by some related species

Strains of Fusarium proliferatum, F. subglutinans, F. anthophilum, F. annulatum, F. succisae, F. beomiforme, F. dlamini, F. napiforme, and F. nygamai from a variety of substrates and geographic areas were tested for the production of fumonisin B1 in culture. None of the cultures of F. subglutinans (0 of 23), F. annulatum (0 of 1), F. succisae (0 of 2), or F. beomiforme (0 of 15) produced fumonisin B1 in culture. Strains of F. proliferatum (19 of 31; 61%) produced fumonisin B1 in amounts ranging from 155 to 2,936 ppm, strains of F. anthophilum (3 of 17; 18%) produced fumonisin B1 in amounts ranging from 58 to 613 ppm, strains of F. dlamini (5 of 9; 56%) produced fumonisin B1 in amounts ranging from 42 to 82 ppm, strains of F. napiforme (5 of 33; 15%) produced fumonisin B1 in amounts ranging from 16 to 479 ppm, and strains of F. nygamai (10 of 27; 37%) produced fumonisin B1 in amounts ranging from 17 to 7,162 ppm. Of the species tested, F. proliferatum is the most important producer of fumonisin B1 because of its association with corn and animal mycotoxicoses such as porcine pulmonary edema. F. napiforme and F. nygamai also may be important because of their association with the food grains millet and sorghum. At present, F. anthophilum and F. dlamini are of minor importance because they are not associated with corn or other major food grains and have only a limited geographic range. This is the first report of the production of fumonisins by F. anthophilum, F. dlamini, and F. napiforme.

A review and update of animal toxicoses associated with fumonisin-contaminated feeds and production of fumonisins by Fusarium isolates

During the 1989 corn harvest season, numerous reports of equine leukoencephalomalacia (ELEM) outbreaks and a pulmonary edema (PPE) syndrome in swine from several regions of the United States were received by the National Veterinary Services Laboratories (NVSL), Ames, Iowa. Previous and concurrent research linked Fusarium moniliforme and fumonisin-contaminated feeds to both diseases. Chemical and mycological investigations revealed fumonisin B1 (FB1) concentrations of 20 to 360 ppm in suspect swine feeds and 8 to 117 ppm in suspect equine feeds. Nonproblem feeds contained concentrations below 8 ppm. Fusarium moniliforme and Fusarium proliferatum were isolated from both problem and nonproblem equine and swine feeds. When cultured on autoclaved corn, the F. moniliforme and F. proliferatum isolated produced respective FB1 and fumonisin B2 (FB2) that range from less than 5 to more than 2450 ppm and less than 5 to more than 1000 ppm, respectively. Isolates from both problem and nonproblem feeds produces high levels (greater than 500 ppm) in culture. Reported here is a review of chemical and mycological data resulting from the study of several cases of PPE and ELEM.

A new fumonisin from solid cultures of Fusarium moniliforme

A new fumonisin has been isolated from Fusarium moniliforme isolate MRC826 grown on corn. It was shown by NMR and mass spectrometry to be an isomer of fumonisin B2 that has free hydroxyl groups at C-3 and C-10 instead of the normal C-3 and C-5. This new fumonisin was detected in cultures of most isolates of F. moniliforme that were examined and was usually present at concentrations similar to those of fumonisin B2. Two isolates of F. moniliforme that produce significantly higher levels of this new isomer were identified.

Taxonomy and biology of Fusarium moniliforme

Fusarium moniliforme is one of the most prevalent fungi associated with basic human and animal dietary samples such as corn. This fungus has been suspected of being involved in human and animal diseases since its original description. Fusarium moniliforme is in the section Liseola along with F. proliferatum, F. subglutinans, and F. anthophilum. Cultural mutation often occurs when F. moniliforme is grown on a medium rich in carbohydrates. Mutants may be either the mycelial or pionnotal type and often lose virulence and the ability to produce toxins. Toxins produced by F. moniliforme are fusaric acid, fusarins, gibberellins, moniliformin, and fumonisins. The fumonisins are produced most often when F. moniliforme grows on corn. Fusarium moniliforme causes ear rot and stalk rot of corn and infection of corn kernels by this fungus is widespread. Infection of developing corn kernels may occur through the silks, through holes and fissures in the pericarp or at points where the pericarp is torn by the emerging seedling, and as a result of systemic infection of the corn plant by F. moniliforme. These models of infection as well as infestation of the kernel surface are important factors when considering the production of fumonisins in corn.

Experimental reproduction of ELEM. A study to determine the minimum toxic dose in ponies

An experiment to gain insight into the minimum toxic dose of fumonisins was conducted by feeding ponies rations with known fumonisin concentrations. Naturally contaminated corn screenings (CS) were blended with pellets, corn, and molasses to formulate individual daily diets. One group of 4 ponies was fed a ration with fumonisin B1 (FB1) varying from less than 1 ppm to 22 ppm. A second group of 5 ponies was fed a ration at varying rates containing 8 ppm FB1 for 180 days. A panel of clinical chemistry parameters was evaluated twice weekly for both groups. One pony in the first group died of equine leukoencephalomalacia (ELEM) after 225 days of which the final 55 days' diet contained 22 ppm FB1. Approximately 9 days prior to death, this animal experienced elevated liver chemistry values. All 5 ponies in the second group experienced mild, transient, clinical signs; were euthanized at 180 days; and had mild, histopathological brain lesions.

Fumonisin B1 production and vegetative compatibility of strains from Gibberella fujikuroi mating population 'A' (Fusarium moniliforme)

We examined 25 strains of Fusarium moniliforme from eight states known to be associated with equine leukoencephalomalacia, a disease caused by the mycotoxin fumonisin B1. We determined the mating population, mating type, and vegetative compatibility group to which each of these strains belonged. All 25 strains were in the 'A' mating population; 12 were A+ and 13 were A-. Seventeen of the 25 strains were female fertile; these strains also averaged higher levels of fumonisin B1 production than did the strains that were female sterile. Nitrate non-utilizing (nit) mutants were generated in all 25 strains and each strain was assigned to a unique vegetative compatibility group based on the inability of the derived nit mutants to form a prototrophic heterokaryon with complementary nit mutants derived from any of the other strains examined. From these data, we concluded that the production of fumonisin B1 is a general characteristic of strains from the 'A' mating population of Gibberella fujikuroi associated with equine leukoencephalomalacia, since all 25 of the isolates that we examined were genetically distinct individuals.

Characterization of an epizootic of pulmonary edema in swine associated with fumonisin in corn screenings

In 1989, corn screenings were associated with acute interstitial pulmonary edema, hydrothorax, and death in swine. Attack rate was 5-50%, case fatality rate was 50-90%, and clinical course was 1-2 days. Screenings from farms with pigs affected with pulmonary edema contained 20-330 micrograms fumonisin B1 per gram. Screenings containing 92 micrograms fumonisin B1 per gram fed to weanling pigs caused pulmonary edema and death. Sterilized corn inoculated with Fusarium moniliforme and diluted 1:1 with clean corn contained fumonisin B1 (17 micrograms/g) and caused acute pulmonary edema when fed for 5 days. Survivors developed subacute hepatotoxicosis with individual hepatocellular necrosis, hepatomegalocytosis, and increased numbers of mitotic figures. Similar liver lesions occurred in pigs given fumonisin B1 intravenously at 0.8 mg/kg body weight for 14 days.

Fate of Fumonisin B 1 in Naturally Contaminated Corn during Ethanol Fermentation

Two lots of corn naturally contaminated with fumonisin B 1 (15 and 36 ppm) and a control lot (no fumonisin B 1 detected) were used as substrates for ethanol production in replicate 8.5-liter yeast fermentations. Ethanol yields were 8.8% for both the control and low-fumonisin corn, while the high-fumonisin corn contained less starch and produced 7.2% ethanol. Little degradation of fumonisin occurred during fermentation, and most was recovered in the distillers' grains, thin stillage, and distillers' solubles fractions. No toxin was detected in the distilled alcohol or centrifuge solids. Ethanol fermentation of fumonisin-contaminated corn coupled with effective detoxification of distillers' grains and aqueous stillage is suggested as a practical process strategy for salvaging contaminated corn.

Toxicity of the mycotoxins fumonisins B1 and B2 and Alternaria alternata f. sp. lycopersici toxin (AAL) in cultured mammalian cells

Fumonisins B1 and B2 and AAL toxin are a series of structurally related mycotoxins. Fumonisins B1 and B2, produced by Fusarium moniliforme Sheldon induce toxic hepatitis and hepatomas in rats and leukoencephalomalacia in horses. The cancer-promotion assay which has been used to guide their purification is slow and consumes large amounts of sample. We have examined a series of cultured mammalian cell lines in order to develop a more rapid and sensitive bioassay system, which may be useful for examining structure-activity relationships and the mechanism(s) of action of these toxins. Of 9 rat hepatoma cell lines tested, all except the two most de-differentiated line were sensitive to the three toxins, with a toxic response visible by 48 h. Approximate IC50 values for the most sensitive hepatoma line, H4TG, were 4, 2 and 10 micrograms/ml for fumonisins B1, B2 and AAL toxin, respectively, in 100 microliters cultures. Among 15 cell lines from other sources, only MDCK dog kidney epithelial cells were sensitive (IC50 = 2.5, 2 and 5 micrograms/ml, respectively). Studies in co-cultures of sensitive and insensitive cell lines and in cultures of a sensitive cell line over a range of cell densities indicated that cytotoxicity of fumonisins B1 and B2 does not involve metabolite activation to a derivative stable enough to diffuse to adjacent cells.

Production of fumonisins by Fusarium moniliforme strains from various substrates and geographic areas

Strains of Fusarium moniliforme from different geographic areas and from corn and other substrates were tested for the ability to produce fumonisins in culture. The test results indicate that the potential exists for production of fumonisins by such strains in agricultural commodities and other substrates in widespread geographic areas.

Survey of fumonisin production by Fusarium species

Fumonisins B1 (FB1) and B2 (FB2), two structurally related mycotoxins with cancer-promoting activity, were recently isolated from corn cultures of Fusarium moniliforme MRC 826. These toxins have been reported to be produced also by isolates of F. proliferatum. Contamination of foods and feeds by F. moniliforme has been associated with human esophageal cancer risk, and FB1 has been shown to be the causative agent of the neurotoxic disease leukoencephalomalacia in horses. Because of the toxicological importance of the fumonisins, the potential to produce FB1 and FB2 was determined in a study of 40 toxic Fusarium isolates representing 27 taxa in 9 of the 12 sections of Fusarium, as well as two recently described species not yet classified into sections. With the exception of one isolate of F. nygamai, fumonisin production was restricted to isolates of F. moniliforme and F. proliferatum, in the section Liseola. The F. nygamai isolate produced 605 micrograms of FB1 g-1 and 530 micrograms of FB2 g-1, and the identity of the toxins was confirmed by capillary gas chromatography-mass spectrometry. This is the first report of the production of the fumonisins by F. nygamai.