sou · GLB3132d2 · 1998-01-01 00:00:00 — 5Toxicological and related effects of antibacterial feed additives As animals are fed for long periods of time, knowledge on bioaccumulation, chronic toxicity and problems associated with residues is imperative. are defined chemical substances and might as such have toxic or allergenic properties. According to directive 70/524/EEC and the guidelines provided in 94/40/EC, satisfactory information relating to these topics has to be presented before approval. Toxic effects, if any, could be seen either in target animal species (or non- target animals as a result of accidental intake) or in humans. Animals and humans may be exposed via residues in animal products and humans also when handling products containing the substances. If the product has unwanted properties, such as organ toxicity, mutagenicity or allergenicity, both ways of exposure could be harmful. Some are poorly absorbed from the gut. Residues are therefore normally not an issue for these substances. Other such as ardacin and avilamycin are absorbed to some extent, and tylosin, spiramycin, olaquindox and carbadox are well absorbed after oral administration (FAO/WHO, 1991; , 1991; FAO/WHO, 1994). Further, the possibility of accumulation in the animal must also be addressed. In the following, some information with relevance to the topic will be discussed. Toxicological aspects of coccidiostats, nitroimidazoles and ionophoric are discussed in chapter 7. 5.2Toxicity for target species With a few exceptions, are not expected to cause toxic reactions in target species at the levels permitted. Bacitracin is nephrotoxic (Prescott and Baggot, 1993), but is not absorbed from the gut. Toxic effects are therefore not to be expected. Flavomycin is reported to have very low toxicity (Huber, 1979) and is only absorbed in small quantities (Sambeth ET AL , 1974). Some macrolides have been reported to cause gastrointestinal disorders, mainly diarrhoea, at therapeutic levels (Prescott and Baggot, 1993). This is not likely to pose a clinical problem as the concentrations used for growth promotion are comparatively low. Moreover, this should probably be regarded as a disturbance of the intestinal microflora and not as a toxic effect on the animal. Carbadox and olaquindox are known to cause adrenal damage at growth promoting levels (van der Molen, 1988; Nabuurs ET AL , 1990). Lowered aldosterone production is found in porcine adrenal glands exposed to carbadox IN (Spierenburg ET AL , 1988b; Spierenburg ET AL , 1988a). (1988) demonstrated a dose-response as well as a time-response relationship between in-feed carbadox and adrenal damage in pigs. After 10 weeks of carbadox at 25 ppm or more, damage to adrenal glomerular cells could be observed histologically at post-mortem examination. Adrenal damage leads to profound hormonal disturbances. This means that the use of carbadox as a feed additive probably results in, at least to some degree, disease (a syndrome caused by impaired function of the adrenal glands) in pigs. The clinical signs observed are dose-related, ranging from mild to severe. At 50 ppm, mild effects of increased faecal dryness may be observed. Other signs include symptoms indicating salt imbalance (urine drinking), decreased abdominal volume and lowered haematocrit values. Further, changes in hair quality, with hair becoming longer and withered, irritable behaviour and a decrease in feed intake and weight gain may be observed. Olaquindox has the same toxic effects, although less pronounced, at dosages of 100 ppm or more (Nabuurs ET AL , 1990). Also in other respects, there is a difference in activity between the substances. Carbadox is permitted in feed at a concentration of 50 ppm, whereas olaquindox is used at 100 ppm (see table 3.III). Accidental overdosing of olaquindox (Köfer ET AL , 1990; Stockhofe-Zurwieden ET AL , 1991) and carbadox (ET AL , 1989) has been reported to cause death and severe adrenal damage in piglets. As the main early sign of intoxication with quinoxalines, i.e. dry faeces, may be mistaken for recovery from enteric disease, mild intoxications are expected to be overlooked by farmers and farm workers. Most are not expected to cause toxic reactions in target species at the levels used. Quinoxalines and carbadox in particular, cause adrenal damage in pigs at doses used for growth promotion. This poses a serious risk for the well-being of the animals. 5.3Toxicity for non-target species There are various possibilities for ingestion of by non-target species, like mix-ups or contamination of feed at the feed mill, inadvertent feeding or inclusion of poultry in animal feed. Problems associated with residues in animal products in pet food could occur if the raw material contains residues. The latter is a direct parallel to residue problems in products intended for human consumption. The susceptibility to accidental intoxication varies between different non- target species. Even that are innocuous for the target species may cause adverse reactions in non-target species. For example, ruminants and horses are generally very sensitive to disturbance of the intestinal microflora by antimicrobial substances. Such disturbances may, in severe cases, cause fatalities. Accidental feeding of low doses of tylosin to cows has been reported to cause ruminal , inappetence, decreased milk production and hypersensitivity (Crossman and Poyser, 1981; Prescott and Baggot, 1993). Contamination of concentrate feed for dairy cows with bacitracin has also been reported. This may cause sudden drops in milk production (Woodger, Feeding of olaquindox at a concentration of 400 ppm to and broiler chickens caused adrenal damage in the birds (ReetzET AL, 1991). The severity of the consequences of accidental feeding of some to non-target species underlines the importance that maximum care should be taken to avoid such events. Accidental intake of by non-target species can result in serious consequences. Adequate procedures for risk management, such as adherence to Procedures, have to be applied. 5.4Adverse effects in humans If the substance used has unwanted properties, ingestion of residues in meat or occupational exposure could produce toxic effects of in humans. Substances with a potential for causing allergic reactions may be harmful at extremely low concentrations. Ingestion of a very small dose of any of these substances might trigger a reaction in an already sensitised person (, 1985). Regulations such as withdrawal times are meant to ensure that no harmful residues remain in animal products after slaughter. With the exception of the quinoxalines, do not have regulated withdrawal times but the use is usually restricted to a maximum age (see table 5.I.). The maximum age limits are often equal to, or perhaps in some regions even longer than, the life span of the animals. In reality, this means that some animals, particularly broilers and slaughter pigs, will be fed right up to the time of slaughter. Examples of MRLs and withdrawal times for some within the EU. Data compiled from Council directive 70/524/EEC annex I and Commission regulation EC 1442/95 unless otherwise indicated 4ABELL ) %XEMPEL P¥ -2, V¤RDEN MAXIMAL RESTKONCENTRATION OCH KARENSTIDER F¶R N¥GRA !&4 INOM %5 $ATA SAMMANST¤LLDA FR¥N 2¥DSDIREKTIV %%' ) OCH +OMMISSIONENS REGLERING %' OM INTE ANNAT (µg/kg) 1ND = not determined 2According to JECFA (FAO/WHO, 1991) Residue problems are addressed in reports from the Joint FAO/(). () are responsible for fixing acceptable daily intake () and maximum residue levels (MRL) for veterinary drugs in Union. For that are at present only used for growth promoting purposes, MRLs have not yet been set. For substances that are poorly absorbed from the gut, no residues in meat would be expected. is known about the possibility of residues due to faecal contamination. If the pharmacokinetics of these substances are similar in humans, ingested residues would not be absorbed to any large extent and would thus not be expected to cause toxic reactions. Spiramycin, when fed to pigs at /kg per day for 7 days, resulted in residues of around /kg in liver at 0.5 days withdrawal time (FAO/WHO, 1991). The dosage used corresponds to to a pig weighing , roughly equivalent to 400 ppm in feed. For poultry receiving 300 ppm for 10 days, at zero-withdrawal liver residues were /kg. Neospiramycin is a major metabolite which is included in the MRL Maximum approved doses for growth promotion are 8 (swine) and 15 (poultry) times lower than the dosages used above. Assuming a linear relationship, MRLs are not likely to be reached in poultry even at zero- withdrawal. For pigs, the assumed residues at zero withdrawal are above MRL. (50µg/kg bodyweight, based on microbiological data) may be exceeded for pig liver and possibly also for poultry liver. Further investigations into residues of spiramycin, including neospiramycin, should be considered. When tylosin was fed to pigs at 200 ppm for 17 days, residues of /kg were detected in liver at zero withdrawal time (FAO/WHO, 1991). At dosages approved for growth promotion, MRLs are not expected to be reached. However, tylosin is extensively metabolised in the animal and there is still some uncertainty as to the appropriate marker residue(s). During storage, carbadox is rapidly decomposed to desoxycarbadox in kidney and liver samples, but is stable in eggs and muscle (Keukens ET AL , 1990; Binnendijk ET AL , 1991). Carbadox has shown dose-related increases of benign and malignant liver tumours in long-term feeding studies in rats, and gave positive results in 14 out of 15 mammalian and non-mammalian genotoxicity studies (FAO/WHO, 1990). Quinoxaline-2-carboxylic acid (QCA) is another major residual metabolite of carbadox. Studies on QCA elimination from liver after feeding of 50 ppm carbadox yielded residues above /kg in liver and kidney for 4 to 5 weeks (Baars ET AL , 1990; Baars ET AL , 1991). The authors opinion was that a withdrawal time of 8 weeks should be recommended. In an experiment by Rutalj (1996), QCA was still present at around /kg at 62 days after cessation of feeding of carbadox at 50 ppm. Detection of QCA is dependent on the extraction method used, and it has been suggested that this is due to other intermediate metabolites in the pathway of carbadox to QCA (Baars ET AL , 1991). In the 36th report of JECFA (FAO/WHO, 1990) it was concluded that an could not be established, due to the carcinogenic and genotoxic nature of carbadox and some of its metabolites. MRLs set in 1990 (FAO/WHO, 1990) for QCA as marker substance were apparently based on the detection limit of the analytical method. Olaquindox is extensively metabolised in the animal. The metabolites found vary between tissues and between animal species (FAO/WHO, 1995). One of the metabolites, 3-methylquinoxaline-2-carboxylic acid (MQCA), is known to be responsible for the IN mutagenicity of other quinoxaline derivatives and has therefore been chosen as a marker compound (FAO/WHO, 1995). The drug is rapidly absorbed from the gut and mainly excreted via urine. No bound residues appear to be present in tissue (FAO/WHO, 1995). In pigs given 60 ppm in-feed olaquindox up to 16 weeks of age, and with a withdrawal period of 28 days, olaquindox residues were below 0.005 ppm in muscle and below 0.01 ppm in kidney (FAO/WHO, 1995). An could not be allocated by JECFA 1995, because of the genotoxic potential of the parent compound and the absence of specific toxicity studies on the metabolites. No MRL has been set. Some comments on the quinoxalines Carbadox has, and olaquindox is suspected of having carcinogenic and genotoxic properties (Cihák and Srb, 1983; Nunoshiba and Nishioka, 1989; FAO/WHO, 1990; FAO/WHO, 1994; FAO/WHO, 1995). Carcinogenic and genotoxic effects in consumers could be possible at very low intake levels, especially if the substance in question is ingested regularly over a number of years. Farm and feedmill workers are a special risk group, frequently exposed to when handling animal feed. If appropriate protection cannot be ensured, the handling of animal feed containing quinoxalines and other with potentially toxic effects must be regarded as an occupational hazard. A conservative approach is often recommended for genotoxic substances in order to prevent underestimation of the risks. Experimental feeding of 60 ppm radiolabelled avilamycin to swine for 14 days resulted in residues of /kg in muscle, /kg in liver, /kg in kidney and 550µg/kg in fat at zero withdrawal time (, 1991). The majority of the parent compound is metabolised or degraded and most of the residue is derived from the oligosaccharide portion of avilamycin (, 1991). MRL has not been determined. Experimental feeding of broiler chickens with 15 ppm ardacin for 30 days resulted in liver residues of up to /kg after a 7 day withdrawal period (Gottschall ET AL , 1995). Ardacin is not biotransformed to any large extent (Gottschall ET AL , 1995). No MRL has been established. Humans may be exposed to substances during production and mixing in feed. Allergic reactions due to macrolides (including spiramycin and tylosin) are reported to be frequent in farmers and other people who handle these substances daily (Veien ET AL , 1980; Gollins, 1989; , 1989; Caraffini ET AL , 1994; Danese ET AL , 1994). Allergic reactions to streptogramins (Pillette ET AL , 1990) and bacitracin (and , 1987; Grandinetti and , 1990) have been reported in association with clinical therapy. Photoallergic reactions due to exposure to olaquindox are well known (de Vries ET AL , 1990; Schauder ET AL , 1996). Although the population at risk for these reactions must be regarded as comparatively small, the consequences of an allergy can be debilitating. This occupational hazard for farmers handling cannot be ignored. Most , if present in food, would be expected to be at concentrations too low for toxic effects. Quinoxalines have a genotoxic potential which may be harmful even at extremely low concentrations. Many have allergenic properties. Such properties are clearly unwanted in substances of common use. The consequences of an allergy can be debilitating As some can cause allergic reactions and are potentially genotoxic, the risks of long term continuous exposure to low dosages of genotoxic substances (e.g. workers at feed mills and farmers) need to be evaluated. As are fed continuously, other substances such as therapeuticals are likely to be administered simultaneously at some time. Therefore, there is a need for information on possible interactions. Some interactions that could be envisaged are intoxication due to amplification of toxic effects, loss of therapeutic effect due to antagonism between the two drugs, or other side effects. Intoxication by ionophores induced by simultaneously administered tiamulin is well known (see chapter 7). No reports have been found on interactions between other and therapeutic substances. As are a part of the feed, it is likely that their use would not be connected with disturbances during therapy. Interactions between and other substances might therefore easily be overlooked. information is available on possible interactions. For humans, the use of is an occupational hazard. The risks involved are allergy and, for quinoxalines, genotoxicity. The population at risk includes farmers, farm workers, feed mill workers and other persons handling products containing the substances. In target animals, the use of quinoxalines results in adrenal damage (disease). This is deleterious for animal well being. * *, 0 3PIERENBERG 4 * DE 'RAAF ' * AND 3EINHORST * 7 , 1991. Residues of carbadox metabolites in edible pork products. * 'INKEL , ! !ERTS - - , DE 'RAAF ' * 3EINHORST * 7 +EUKENS ( * 3CHWILLENS 0 , 7 * 3PIERENBURG 4 * AND *, 0 , 1990. Kinetics of carbadox residues in pigs. )N PROCEEDINGS OF 2ESIDUES OF VETERINARY DRUGS IN FOOD %URO2ESIDUE CONFERENCE 21-23, Noordwijkerhout. "INNENDIJK ' - !ERTS - - , AND +EUKENS ( * , 1991. ruggedness testing of the determination of residues of carbadox and metabolites in products of animal origin. Stability studies in animal tissues. *OURNAL OF #HROMATOGRAPHY 401-410. #ARAFFINI 3 !SSALVE $ 3TINGENI , AND ,0 , 1994. Tylosin, an airborne contact allergen in veterinarians. #ONTACT $ERMATITIS 327-328. #IH¡K 2 AND 3RB 6 , 1983. Cytogenetic effects of quinoxaline-1,4-dioxide-type growth- promoting agents. -UTATION 2ESEARCH 129-135. #ROSSMAN 0 * AND 0OYSER - 2 , 1981. Effect of inadvertently feeding tylosin and tylosin with dimetridazole to dairy cows. 6ETERINARY 2ECORD 285. $ANESE 0 :ANCA ! AND "ERTAZZONI - ' , 1994. Occupational contact dermatitis from tylosin. #ONTACT $ERMATITIS 122-123. DE 6RIES ( "EYERSBERGEN (ENEGOUWEN ' - +ALLOE & AND "ERKHUYSEN - ( , 1990. Phototoxicity of olaquindox in the rat. 2ESEARCH IN 6ETERINARY 3CIENCE &!/ 7(/, 1990. 36th report of : Evaluation of Certain Veterinary Drugs.4ECHNICAL REPORT SERIES .O 50-56. &!/ 7(/, 1991. Monographs prepared by the 38th meeting of the Joint FAO/WHO Residues of some veterinary drugs in animals and foods.&!/ &OOD AND .UTRITION 0APER 41/4 pp.136. &!/ 7(/, 1994. Forty-second Meeting of the Joint FAO/on Toxicological evaluation of certain veterinary drug residues in food.7(/ &OOD !DDITIVES 3ERIES pp. &!/ 7(/, 1995. Forty-second report of the joint FAO/on Evaluation of certain veterinary drug residues in food.7(/ 4ECHNICAL 2EPORT 3ERIES .O pp. 'OLLINS 7 * , 1989. Occupational asthma due to tylosin tartrate. "RITISH *OURNAL OF )NDUSTRIAL -EDICINE 894. 'OTTSCHALL $ 7 &ILTER - , AND 7ANG 2 , 1995. Analysis of tissue residues and comparative metabolism of ardacin in cattle, broilers, and rats. *OURNAL OF !GRICULTURAL AND &OOD #HEMISTRY 2956-2963. 'RANDINETTI 0 * AND &OWLER * & *R , 1990. Simultaneous contact allergy to neomycin, bacitracin, and polymyxin. *OURNAL OF !MERICAN !CADEMY OF $ERMATOLOGY 646- (UBER ' , 1979. Moenomycin and related phosphorus-containing antibiotics. )N F.E. ), !NTIBIOTICS Vol. 5, pt 1. +ATZ " % AND &ISHER ! ! Bacitracin: a unique topical antibiotic sensitizer. *OURNAL OF !MERICAN !CADEMY OF $ERMATOLOGY 1016-1024. +EUKENS ( * INNENDIJK ' - AND !ERTS - - , , 1990. Determination of residues of carbadox and metabolites in edible tissues - IN stability studies. )N PROCEEDINGS OF 4HE %URO2ESIDUE CONFERENCE 2ESIDUES OF 6ETERINARY $RUGS IN &OOD 21- 23, Noordwijkerhout. +¶FER * (¶CHER ( AND (INTERDORFER & , 1990. 7IENER 4IER¤RZTLICHE -ONATSSCHRIFT 135-137. ,EE ( 3 7ANG 9 4 9EO # 4 4AN + 4 AND 2ATNAM + 6 , 1989. asthma due to tylosin tartrate. "RITISH *OURNAL OF )NDUSTRIAL -EDICINE 498-499. -AGNUSSEN * $ $ALIDOWICZ * % 4HOMSON 4 $ AND $ONOHO ! , , 1991. Tissue residues and metabolism of avilamycin in swine and rats. *OURNAL OF !GRICULTURAL AND &OOD #HEMISTRY 306-310. .ABUURS - * ! -% * DE 'RAAF ' * AND *, 0 , 1990. signs and performance of pigs treated with different doses of carbadox, cyadox and olaquindox. *OURNAL OF 6ETERINARY -EDICINE 3ERIES ! .UNOSHIBA 4 AND .ISHIOKA ( , 1989. Genotoxicity of quinoxaline 1,4-dioxide derivatives in %SCHERICHIA COLI and 3ALMONELLA TYPHIMURIUM. 0ILLETTE - #LAUDEL * 0 -# AND ,ORETTE ' , 1990. Pristinamycine après sensibilisation à la virginiamycine topique. !LLERGIE ET )MMUNOLGIE 197. 0OWER 3 " $ONNELLY 7 * # -C,AUGHLIN * ' 7ALSH - # AND $ROMEY - & , Accidental carbadox overdosage in pigs in an Irish weaner-producing herd. 6ETERINARY 2ECORD 367-370. 0RESCOTT * & AND "AGGOT * $ EDS , 1993. !NTIMICROBIAL THERAPY IN VETERINARY MEDICINE 2nd ed. 2EETZ * "USCH ! AND 7ITTHUHN 5 , 1991. Nebennierenveränderungen bei Puten- und Broilerküken. -ONATSHEFTE F¼R 6ETERIN¤RMEDIZIN 220-225. Toxicological assessment of residues of feed additives and veterinary medicinal products in foodstuffs of animal origin. )N PROCEEDINGS OF TH %UROPEAN 6ETERINARY #ONGRESS , Exeter. 2UTALJ - "AZULIC $ 3APUNAR 0OSTRUZNIK * :IVKOVIC * AND ,JUBICIC ) , 1996. Quinoxaline-2-carboxylic acid (QCA) in swine liver and muscle. &OOD !DDITIVES AND #ONTAMINANTS 879-882. 3AMBETH 7 "AUER & $OST ' AND .ESEMANN ' , 1974. Evaluation of the saferty of flavomycin in poultry. )N PROCEEDINGS OF 86 7ORLD S 0OULTRY #ONGRESS 11- 3CHAUDER 3 3CHR¶DER 7 AND '* , 1996. photoallergic contact dermatitis followed by transient or persistent light reactions in 15 pig breeders. #ONTACT $ERMATITIS 344-354. 3PIERENBURG 4 * "AARS ! * DE 'RAAF ' * AND *, 0 , 1988a. induced inhibition of aldosterone production in porcine adrenals IN . )N PROCEEDINGS OF TH #ONGRESS OF %UROPEAN !SSOCIATION FOR 6ETERINARY 0HARMACOLOGY AND 4OXICOLOGY 28-September 2, . 3PIERENBURG 4 * "AARS ! * DE 'RAAF ' * AND *, 0 , 1988b. induced inhibition of aldosterone production in porcine adrenals IN . 4OXICOLOGY IN 6ITRO 141-143. 3TOCKHOFE :URWIEDEN . "RUNCKHORST $ 7ALDMANN + ( AND 0OHLENZ * , 1991. Pathomorphologische Verlaufsuntersuchungen nach Olaquindoxintoxikation bei Mastschweinen. 4IER¤RZTLICHE 0RAXIS 58-63. -% * , 1988. Pathological effects of carbadox in pigs with special emphasis on the adrenal. *OURNAL OF #OMPARATIVE 0ATHOLOGY 55-67. + (ATTEL 4 *USTESEN / AND .ORHOLM ! Occupational contact dermatitis due to spiramycin and/or tylosin among farmers. 7OODGER ' * ! Antibiotic contamination of compound cattle feed. 6ETERINARY 2ECORD 173. 6Environmental aspects on antibacterial feed additives Several factors are of interest for the assessment of environmental effects of . The environmental burden, i.e. the amount of the substance that enters and is deposited in the environment, as well as the distribution and transport between different environmental compartments, defines the exposure. Effects to be considered include: effects on soil microbes, earthworms, algae and aquatic organisms. Furthermore, safety for wildlife and other unintended recipients must also be considered. The environmental deposition of is related to the number of animals fed these substances, duration of use, dosage, metabolism, excretion pattern and method of waste disposal. As most of these substances are poorly, or not at all, absorbed in the gut, the amount excreted in faeces is almost as large as the total amount fed to various animal species. The impact on the environment from the use of is therefore through excretion in faeces. Some may also be excreted in urine. Although the concentrations in urine would be expected to be far lower than in faeces, evaporation and precipitation during storage could lead to higher concentrations, especially at the bottom of the storage tank. According to directive 70/525/EEC and the guidelines in 94/40/EC, studies on excreted residues and an environmental assessment should be performed on all feed additives. An overall assessment of environmental effects must include thorough estimations of secondary effects and evaluations of different production systems as a whole. For example, waste from the manufacture of has a high nitrogen content and may also include other potentially harmful components, excess among others. The disposal of this waste must be taken into account. The need for long-term assessments when it comes to environmental effects cannot be overemphasised. In the following, some information available on environmental aspects of will be discussed. Corresponding information on coccidiostats (and ionophore ) is found in chapter 7. 6.2Exposure of the environment to Many of the are derived from soil microorganisms and are therefore likely to be, eventually, degraded in soil. Nonetheless, degradability and degradation rates must be determined for each substance. This testing must be standardised as far as possible. Many variables need to be considered in this standardisation (Bouwman and Reus, 1994). As the compounds will be excreted in faeces, degradation studies should be conducted in soil mixed with manure. The type of manure used is important in this regard.