Feeding Experiments with Ochratoxin a Contaminated Barley for Bacon Pigs

Tissue distribution of ochratoxin A in pigs after administration of two-levels contaminated diets

The aim of the present study was to determine the levels of ochratoxin A (OTA) in pigs experimentally exposed to this mycotoxin and to evaluate if bile may be used to assess exposure to OTA. Twelve hybrid pigs were divided into 3 equal groups, a control group D0, and 2 experimental groups, D1 fed with 50 µg OTA/kg diet, and D2 fed with 500 µg OTA/kg diet for 15 days. At the end of the test, the animals were euthanized and samples of different tissues and biological fluids were analysed by HPLC-fluorescence detection for the presence of OTA. Samples of unconventional edible tissues such as lung and heart were also taken for analysis because they are used in typical Italian regional dishes. The Italian guidance value for OTA of 1 µg/kg established for pork meat and derived products has been exceeded in all the matrices from both the experimental groups. The comparison between OTA levels detected in D1 and D2 groups showed clearly a linear dose-response relationship. Based on the mean values measured, OTA distribution follows the order blood plasma > lung > kidney (in D1 group), heart (in D2 group) > heart (in D1 group), kidney (in D2 group) > bile > liver > fat > muscle. Analysis of bile can be useful for the detection of OTA in pigs. However, since blood can easily be taken from pigs, and given the correlation between the mycotoxin concentration detected in this matrix and the concentrations detected in the others, OTA level in blood is a more viable approach to assessing the presence of OTA in edible tissues. As lung and heart may contain high concentrations of OTA, the analytical controls should also include these matrices.

Determination of ochratoxin A in serum and urine of pigs

The objective of the study was to determine ochratoxin A (OTA) concentrations in serum and urine of pigs during 30-day OTA treatment. OTA was administered orally to the experimental group (n=5) at a dose of 0.78 mg per animal per day, whereas control animals (n=5) were left untreated. OTA concentrations were determined using a validated enzyme-linked immunosorbent assay (ELISA). Method validation resulted in mean recoveries of 93-101% for serum and 98-106% for urine, with acceptable mean inter- and intraday relative standard deviations (<8% for urine and <7% for serum). The ELISA method can be effectively used as a simple screening method to determine OTA exposure in pigs during fattening. The maximum mean OTA concentration in serum was recorded on day 22 (8.75±2.93 ng/ml) and in urine on day 20 (43.56±35.76 ng/ml), indicating significant differences in OTA concentrations between these two matrices.

Review. Ochratoxin A: Presence in Human Plasma and Intake Estimation

Ochratoxin A (OTA) is a fungal toxic secondary metabolite that can be found in several foodstuffs and thereby ingested by humans. One way to assess exposure of humans to OTA is the determination of the levels of this mycotoxin in blood plasma from a certain population. Such studies have been done in many countries, both in healthy people and nephropathy patients. Relationships with individual characteristics were investigated in several cases. Thus, most studies found no correlation with age, either with gender. However, the few studies that found correlation between OTA plasma levels and gender showed that men presented the highest values. When sampling was done over more than one season, the highest OTA plasma levels were found mostly in summer. Differences within regions of a country were related to dietary habits of each area. OTA levels of group populations showed variations from year to year, whereas intraindividual repetitions showed no specific trend. Daily intake of the toxin can be estimated from OTA plasma concentrations by the Klaassen equation. OTA toxicokinetics are considered in this review. Calculated daily intake of OTA by different studies did not overpass the proposed tolerable daily intakes of OTA.

Ochratoxin A: An overview on toxicity and carcinogenicity in animals and humans

Ochratoxin A (OTA) is a ubiquitous mycotoxin produced by fungi of improperly stored food products. OTA is nephrotoxic and is suspected of being the main etiological agent responsible for human Balkan endemic nephropathy (BEN) and associated urinary tract tumours. Striking similarities between OTA-induced porcine nephropathy in pigs and BEN in humans are observed. International Agency for Research on Cancer (IARC) has classified OTA as a possible human carcinogen (group 2B). Currently, the mode of carcinogenic action by OTA is unknown. OTA is genotoxic following oxidative metabolism. This activity is thought to play a central role in OTA-mediated carcinogenesis and may be divided into direct (covalent DNA adduction) and indirect (oxidative DNA damage) mechanisms of action. Evidence for a direct mode of genotoxicity has been derived from the sensitive 32P-postlabelling assay. OTA facilitates guanine-specific DNA adducts in vitro and in rat and pig kidney orally dosed, one adduct comigrates with a synthetic carbon (C)-bonded C8-dG OTA adduct standard. In this paper, our current understanding of OTA toxicity and carcinogenicity are reviewed. The available evidence suggests that OTA is a genotoxic carcinogen by induction of oxidative DNA lesions coupled with direct DNA adducts via quinone formation. This mechanism of action should be used to establish acceptable intake levels of OTA from human food sources.

Toxicokinetics and toxicodynamics of ochratoxin A, an update

Ochratoxin A (OTA) is a mycotoxin produced by fungi of two genera: Penicillium and Aspergillus. OTA has been shown to be nephrotoxic, hepatotoxic, teratogenic and immunotoxic to several species of animals and to cause kidney and liver tumours in mice and rats. Because of differences in the physiology of animal species, wide variations are seen in the toxicokinetic patterns of absorption, distribution and elimination of the toxin. Biotransformation of OTA has not been entirely elucidated. At present, data regarding OTA metabolism are controversial. Several metabolites have been characterized in vitro and/or in vivo, whereas other metabolites remain to be characterized. Several major mechanisms have been shown as involved in the toxicity of OTA: inhibition of protein synthesis, promotion of membrane peroxidation, disruption of calcium homeostasis, inhibition of mitochondrial respiration and DNA damage. The contribution of metabolites in OTA genotoxicity and carcinogenicity is still unclear. The genotoxic status of OTA is still controversial because contradictory results were obtained in various microbial and mammalian tests, notably regarding the formation of DNA adducts. More recent studies are focused on the OTA ability to disturb cellular signalling and regulation, to modulate physiological signals and thereby to influence cells viability and proliferation. The present paper offers an update on these different issues. In addition since humans and animals are likely to be simultaneously exposed to several mycotoxins, especially through their diet, the little information available on the combined effects of OTA and other mycotoxins has also been reviewed.

Content of ochratoxin A in paired kidney and meat samples from healthy Danish slaughter pigs

In 1999, paired samples of kidney and meat were taken from 300 healthy Danish pigs and analysed for ochratoxin A. The concentrations of ochratoxin A in kidney ranged from 0 to 15 microg kg(-1) (mean 0.50 microg kg(-1), median 0.18 microg kg(-1)) and in meat from 0 to 2.9 microg kg(-1) (mean 0.12 microg kg(-1), median 0.03 microg kg(-1)). The data together with the Danish control data show that today the pig industry in Denmark has no problem keeping the content of ochratoxin A in pig at very low levels even in years with wet harvest conditions. The mean ratio 'content in meat/content in kidney' for paired samples was 39%. For kidney samples >1.0 microg kg(-1), the mean ratio was 22%. The Danish control system for ochratoxin A in pig kidney established in 1978 can be regarded as a success because the levels in pig have been reduced substantially, and hence for the consumer the contribution from pig products to the total intake of ochratoxin A is very small compared with other sources.

Survey of Romanian slaughtered pigs for the occurrence of mycotoxins ochratoxins A and B, and zearalenone

Blood serum, kidney, liver and muscle sample per animal were collected from slaughtered pigs (n = 52). The samples were analysed for ochratoxin A (OTA) and B (OTB) by HPLC methods. Zearalenone (ZEA) in serum was analysed by enzyme immunoassay. A total of 98% serum samples were OTA positive in the range of 0.05-13.4 ng/ml and 85% contained under 5 ng OTA/ml. The incidences of OTA in kidney and liver were very similar (79%, 75%) with mean levels of 0.54 ng/g and 0.16 ng/g, respectively. The lowest incidence (17%) and the lowest mean level contamination (0.15 ng/g) were in muscle samples. The mean distribution in tissues followed the pattern serum > kidney > liver > muscle (100%; 0.26%; 8.5%; 2.57%). No kidney, liver or muscle sample was found OTA positive above the maximum admitted limit in Romania (5 ng/g). No sample was found to be positive for OTB. A very similar OTA contamination (mean = 4.19 ng/ml, coefficient of variation = 34.4%) was observed in the serum samples (n = 10) collected from the same farm. A possible difference in regional distribution of OTA in Romania is suggested. Zearalenone was detected only in 17.3% of the serum samples with a maximum concentration of 0.96 ng/ml. This study shows the presence of OTA and ZEA in Romanian slaughtered pigs at levels comparable to those reported in other countries.

A French monitoring programme for determining ochratoxin A occurrence in pig kidneys

Ochratoxin A is a carcinogen and nephrotoxin which can enter the food chain resulting in human exposure. As pig herds are exposed to ochratoxin A through their feed, their kidneys, livers and pork meat are considered as a possible route of exposure for humans. France, an important producer of pork and pork products, set up a national monitoring programme which included the training of six routine public laboratories in the analysis of ochratoxin A using an immunoaffinity step followed by a HPLC-fluorimetric detection. The programme randomly sampled 300 healthy and 100 nephropathic pig kidneys in 1997 and 710 healthy pig kidneys in 1998. Less than 10% of samples were significantly contaminated by ochratoxin A : in the 1997 survey, 1% of samples contained 0.40-1.40 microg kg(-1) of ochratoxin A and in the 1998 survey 7.6 % exhibited ochratoxin A levels in the range 0.5-5 microg kg(-1). In the case of nephropathic kidneys, only traces of ochratoxin A (0.16 to 0.48 microg kg(-1)) were detected in six samples out of 100. Even if not a major route of exposure for humans, pigs are clearly exposed to this mycotoxin and monitoring of pork products and of feed for swine is necessary.

Survey of pork, poultry, coffee, beer and pulses for ochratoxin A

Surveys have been carried out to estimate the levels of ochratoxin A in pork, poultry, coffee, beer and pulses. A total of 286 samples were analysed. The results show that compared with cereals and cereal products the contribution from the foods surveyed to the total intake of ochratoxin A by the Danish population must be considered to be of less importance.

Porcine nephropathy in Bulgaria: a progressive syndrome of complex or uncertain (mycotoxin) aetiology

Macroscopic nephropathy was observed in 506 pigs at slaughter in Bulgaria in 1993/94. Histopathological changes were mainly degenerative and proliferative, and were linked with kidney hypertrophy similar to that of the classical Danish Syndrome. Retention cysts formed by dilated tubules, activation or proliferation of capillary and vascular endothelium, and the development of neoplastic tissue were also observed. The most advanced pathology took the form of extensive interstitial fibrosis. Traces of ochratoxin A were found in the kidneys of the majority of 96 cases examined, and in some feed samples taken retrospectively from farms or commercial sources. The dietary ochratoxin concentration (100 micrograms/kg), calculated from serum analyses, closely matched the average of individually analysed feeds. In other feeds no ochratoxin A was detected and the cosmopolitan mycobiota isolated did not include the ochratoxinogenic Penicillium verrucosum that caused the Danish syndrome. Aspergillus ochraceus was rare and the isolates did not synthesise ochratoxin in laboratory culture. The unconfirmed diagnosis of ochratoxicosis suggests a complex or multi-toxin aetiology for this rather common chronic disease in Bulgaria.

The incidence and distribution of ochratoxin A in western Canadian swine

A survey of swine destined for slaughter in Manitoba was conducted to examine the incidence of ochratoxin A (OA) in swine herds from different regions of Manitoba throughout the year 1989-90. Thirty-six percent of the serum samples which were collected from 1600 pigs contained detectable levels of OA. The identity of this toxin was confirmed using liquid chromatography-mass spectrometry and enzymatic hydrolysis. There was a significant effect of the region from which the herds originated, as well as the season in which the samples were collected on both the incidence (p < 0.001) and concentration of OA (p < 0.001). In July, 65% of the samples contained detectable levels of OA, compared with 38, 21 and 17%, in April, October and January respectively. Furthermore, 24% of the samples collected in July contained greater than 15 ng/ml of OA, while only 2, 9, and 1% of the samples collected in April, October and January respectively, contained greater than 15 ng/ml of OA. Based on the six samples collected from each herd, it appears that the presence and concentration of OA within a herd may be estimated from a limited number of animals per herd.

Prevention of nephrotoxicity of ochratoxin A, a food contaminant

Ochratoxin A (OTA) is a mycotoxin produced by ubiquitous Aspergilli, mainly by Aspergillus ochraceus and also by Penicilium verrucosum. It was found all over the world in feed and human food and blood as well as in animal blood and tissues. The most threatening effects of OTA are its nephrotoxicity and carcinogenicity, since this mycotoxin is nephrotoxic to all animal species studied so far and is increasingly involved in the Balkan endemic nephropathy (BEN), a human chronic interstitial nephropathy which is most of the time associated to urinary tract tumours. Since it seems impossible to avoid contamination of foodstuffs by toxigenic fungi, detoxification and detoxication for OTA are needed. To reduce or abolish the OTA-induced toxic effects, several mechanisms were investigated. The results of these investigations showed that some of the potential antidotes were efficient in preventing the main OTA toxic effects whereas some others were not. Promising compounds are structural analogues of OTA, and/or compounds having a high binding affinity for plasma proteins such as piroxicam, a non-steroidal anti-inflammatory drug (NSAID). Some enzymes such as superoxide dismutase (SOD) and catalase, radical scavengers, vitamins, prostaglandin (PG) synthesis inhibitors, (such as piroxicam), pH modificators, adsorbant resin such as cholestyramine etc. are efficient in vivo. Some of the results obtained in vivo were already confirmed in vitro and gave useful information on how to safely use these antidotes. The most generally acting compound seems to be A19 (Aspartame), a structural analogue of OTA and phenylalanine. When given to rats A19 (25 mg/kg/48 h) combined to OTA (289 micrograms/kg/48 h) for several weeks largely prevented OTA nephrotoxicity and genotoxicity. When given after intoxication of animals with OTA it washes out the toxin efficiently from the body. In vitro, A19 (10 micrograms/ml) prevents OTA (20-500 micrograms/ml) binding to plasma proteins. Its general action without any known side effect in humans and in animals, points at A19 to be the best candidate for preventing the OTA-induced subchronic effects.

Characterization of pig liver purified cytochrome P-450 isoenzymes for ochratoxin A metabolism studies

In this paper, we report the characterization of 4 isolated, constitutive cytochrome P-450 fractions from pig liver microsomes. The two predominant forms, A2 and A3, exhibit several similarities: a Mr of 54 kDa, a lambda max CO-Fe++ at 448 nm, a relatively high ratio of the high-spin form and an immunological cross-reaction with polyclonal antibodies against rat liver P-450 IIB1. It is shown that these forms and the minor form Ba, which are active as benzphetamine N-demethylase, play an important metabolic role in ochratoxin A oxidation. This mycotoxin was oxidized by at least 3 different pig liver cytochrome P-450 fractions, each producing different metabolites, namely (4R)-, (4S)-hydroxyochratoxin A, and a new lipophilic metabolite. Since the pig is particularly susceptible to ochratoxin A toxicity, it represents a good animal model for in vitro studies of the metabolism of such a xenobiotic.

Long-term administration of low doses of mycotoxins in poultry. 1. Residues of ochratoxin A in broilers and laying hens

The occurrence and amount of residues of ochratoxin A (OA) in poultry tissues and organs were investigated in a trial aimed at measuring the effects of contamination approaching the patterns more frequently found in natural situations (i.e., small doses of OA in the diet for long periods). Hubbard male broilers and laying hens were treated with an OA-contaminated feed (50 ppb) from the 14th day of age onward. Both groups were further divided into subgroups, some of which underwent continual treatment (64 and 169 days, respectively) and others that were withdrawn from administration (maximum 28 and 82 days, respectively). Determination of residues was performed by high performance liquid chromatography. Residues in liver were higher in broilers (up to 11.0 ppb) than in hens (1.5 ppb), whereas the reverse occurred in kidney (up to .8 and 5.8 ppb, respectively). Residues (.8 ppb) were also in hen thigh muscle but not in breast muscle. Residues of OA in poultry appear to be of possible public health concern. Suggestions for monitoring are given.

Analysis, occurrence and control of Ochratoxin A residues in Danish pig kidneys

In Denmark, porcine kidneys displaying macroscopic lesions of mycotoxic nephropathy are analysed for Ochratoxin A and the carcass condemned if the concentration exceeds 25 micrograms/kg. Since late 1982 these analyses have been conducted centrally. The reliability of the one-dimensional thin layer chromatographic method is discussed and results from an interlaboratory comparison are presented. From 1980 to 1984 there has been an overall decline in the rate of ochratoxicosis, interrupted in 1983 by a major increase geographically located in the northern half of Jutland. During that year 7639 kidneys were examined; 3% contained more than 150 micrograms/kg and 29% more than 25 micrograms/kg Ochratoxin A, corresponding to a condemnation rate of 15 per 100 000 slaughterings. The early stage of the increased incidence was characterized by kidneys with extremely high levels of the toxin; later most of the samples were negative or near-negative, as affected pigs were presumably fed a toxin-free diet before slaughtering. The efficacy of the control program is discussed in view of the 1983 data.

Conversion of ochratoxin C into ochratoxin A in vivo

The conversion of ochratoxin C to ochratoxin A was studied in rats after oral and intravenous administration. The concentration of ochratoxin A in the blood as a function of time was the same after oral administration of equivalent amounts of either ochratoxin C or ochratoxin A. The maximum ochratoxin A concentrations were measured 60 min after administration. Given intravenously, ochratoxin C was also converted to ochratoxin A. Maximum concentrations were reached after 90 min. It is concluded that ochratoxin C is readily converted to ochratoxin A after both oral and intravenous administration. There is reason to believe that a comparable toxicity of the two toxins is based upon this conversion and that only interference with the biotransformation mechanisms may cause a difference in their toxicity.

Experimental ochratoxicosis A in pigs

Ochratoxin A was isolated from a culture of Aspergillus ochraceus grown on a cornmeal substrate. The mycotoxin was added to a grower ration for 14 kg young pigs at 2, 4, 8 and 16 mg/kg and fed to groups of 3 for periods ranging from 6 to 20 days. The highest dose rate group only became sick, with loss of appetite, weight loss, polydipsia, polyuria, proteinuria, glucosuria, elevation of serum creatinine, pale swollen kidneys, renal tubular degeneration and cortical fibrosis. The pigs on the 2 mg toxin/kg of diet appeared unaffected with only slight renal tubular degeneration present in one animal. Feeding diet contaminated with the intermediate doses of 4 and 8 mg toxin/kg diet lead to reduction of weight gain and/or reduced feed intake and feed conversion efficiency as well as mild renal lesions. Ochratoxin A has recently been reported on mould-affected grain in Queensland and some local strains of A. ochraceus in culture have been shown to be able to produce levels of ochratoxin A of up to 4000 mg/kg of substrate. Rare episodes of nephrotoxicity in pigs seen at slaughter in Queensland may thus be due to prior contamination of the diet with ochratoxin A.