BEN - Notiziario ISS - Vol.16 - n.7-8
Antibiotic use in cattle farms: Results of a survey among veterinarians
Luca Busani1, Caterina Graziani1, Alessia Franco2, Alessandra Di Egidio2, Goffredo Grifoni2, Giovanni Formato2, Marcello Sala2, Nancy Binkin3 and Antonio Battisti2
1Laboratory of Veterinary Medicine, ISS
2Istituto Zooprofilattico Sperimentale of Lazio and Tuscany, Rome
3Laboratory of Epidemiology and Biostatistics, ISS
Antibiotics are fundamental for the control in infectious diseases in man and animals. In animals, their use may accelerate growth and increase productivity. In recent years, however, there has been considerable concern about the emergence and diffusion of antibiotic resistance resulting from antibiotic use in the veterinary sector, with possible risks for the human population.
To study the knowledge and attitudes of veterinarians who work with beef and dairy cattle regarding antibiotic use and detemine the extent to which their practices are in keeping with the principles of prudent antibiotic use use as published by various international organizations, we performed a national study between June and September 2002. The study had the following objectives:
From the membership lists of two scientific societies (1143 members), 250 were selected using simple random sampling. Only those veterinarians in private practice who served as consulting veterinarians for meat and dairy cattle were eligible for inclusion. Those selected were contacted telephonically, and after ascertaining study eligibility, an interview was conducted concerning:
Data were entered in EpiData 2.1 and analysed using EpiInfo 2002.
One hundred six veterinarians were interviewed, representing 42% of the original sample. Of the remaining 144, 48 were not eligible, 92 could not be contacted despite multiple attempts, and 4 refused to participate. The veterinarians interviewed provide care for about 5% of the total cattle population of the country; most (81%) worked in the north and provided consultation for dairy cattle.
The veterinarians recommended vaccination for respiratory infections for 3% of the dairy farms 34% of the cattle farms in their practices; for neonatal enteritis, the corresponding figures were 24% and 30%.
Laboratory diagnosis was used by 67% of the veterinarians “sometimes” or “always” for mastitis, by 37% for neonatal enteritis, and by 17% for respiratory infecdtion. More than 60%, however, practices empiric therapy while awaiting culture and sensitivity results.
The antibiotics most frequently prescribed are reported in the Table. “New generation” antibiotics (3rd and 4th generation cephalosporins, new aminoglycosides, and fluoroquinolones) listed among the drugs of first choice by 12% of veterinarians for treating mastitis; these drugs were among the first choices of 68% of veterinarians for neonatal enteritis treatment and of 28% for respiratory diseases; this preference was especially common among veterinarians providing care for large cattle farms. An additional 12% listed phenicols (fluorphenicaol) as their first choice for respiratory infections.
Antibiotic use was also common for prophylaxis, with 20% reporting using antibiotics for the prevention of neonatal enteritis, 28% to prevent respiratory diseases, and 62% to prevent mastitis during the drying off period.
Therapeutic failure was reported “often” by 21% and “sometimes by 64% of the veterinarians. Those who experienced failures were more likely to use new generation antibiotics. A series of multivariate analyses showed a significant association between:
None of the other variables in the models, including training and specialization, area of practice, or continuing education experiences were significantly associated with the use of these antibiotics.
More than 75% of the veterinarians had participated in conferences or continuing education courses in the previous year, were subscribers to Italian journals, and received updates from the drug industry; 39% participated in mailing lists and 24% subscribed to international journals; approximately 20% used all of the above methods to remain current. More than 20% responded correctly to all questions regarding antibiotic resistance.
The sample interviewed was young, used a variety of methods to remain current, and were aware of the potential risks of antibiotic resistance, but a substantial number nonetheless used “new generation” antibiotics or fluoroquinolones when other antibiotics are clearly available. This use was not influence by continuing education experience, perception of the problem of resistance, or use of the laboratory; instead it may result from the perceived need to rapidly resolve a problem and the belief that this will be more likely to occur if such antibiotics are used. Indeed, we found a seemingly paradoxical relationship between use of the laboratory for culture and sensitivity for enteric infections and the use of fluoroquinolones; of those using laboratory testing, 38% recommended fluorquinolones as their first choice drug.
These practices, which may pose public health risks, were seemingly unaffected by levels of knowledge and training. Increased use of such antibiotics is of particular concern for the treatment of conditions such as neonatal enteritis, which frequently is viral in origin and for which treatment is recommended only when the animal shows signs of systemic infection.
The resistance of microorganisms to antibiotics is considered to be a major international public health problem and involves the fields of both human and veterinary medicine. It has been widely demonstrated that the use of antibiotics in animals can lead to the selection of resistant strains that colonize the intestines and are subsequently excreted, which may lead to contamination of the environment and of meats destined for human consumption.
There are essentially two ways in which use of antibiotics in the veterinary sector may potentially lead to human disease with resistant strains. One possibility is that humans may be infected with resistant disease-producing microorganisms (e.g. Salmonella and Campylobacteria). Alternatively, bacteria that are non-pathogenic for humans may undergo selective pressure in the intestines of animals treated with antibiotics and thereby develop resistance that may be transmitted to other microorganisms that are pathogenic to humans.
In a recent study, Escherichia coli and Enterococci, a commensal organism that is sometimes responsible for major hospital infections, were isolated from the intestines of cattle undergoing routine slaughter in the Veneto region of northern Italy and tested for antibiotic resistance. For both organisms, the highest level of resistance was seen in strains isolated from young calves. This was most likely due to the massive usage of antimicrobials in this category of animals. In particular, the levels of resistance in E. coli to trimethoprim/sulfamethoxazole (58,3%), cloramphenicol (30,6%), and fluoroquinolones (16,7% to enrofloxacin ) were of concern. No resistance was noted to cephalosporins. In calves, resistance levels in Enterococci were high for erythromycin (88.5%) and spiramycin (96,2%) but were lower for ampicillin and (< 10%), as well as for vancomycin (26.9%) and techicoplanin (7.7%). These last two values are nonetheless of considerable concern since both antibiotics are particularly important in the treatment of multiresistant Enterococcal infections in humans; in 1997, on the basis of evidence that vancomycin resistance had occurred in bacteria of animal origin, the use of avoparicin, an analogue of vancomycin that had been used as a growh promoter, was banned at the European Community level (3).
The results from Veneto are of particular note in light of the research done by Busani et al and demonstrate the importance of establishing a nationwide plan for monitoring the resistance of antibiotics and ensuring the cautious use of antibiotics in the veterinary sector.
1. Ricci A, Vio D, Zavagnin P, et al. Monitoraggio dell’ antibioticoresistenza in batteri zoonotici e commensali isolati da bovini al momento della macellazione. Atti della Società Italiana di Buiatria 2003; 35: 59-66.
2. Van den Bogaard AE, Stobberingh EE. Epidemiology of resistance to antibiotics. Links between animals and humans. Int J Antimicrobial Agents 2000; 14(4): 327-35.
3. Direttiva 97/72/CE della Commissione del 15 dicembre 1997 relativa agli additivi nell'alimentazione degli animali. GU n. L 351 del 23 dicembre 1997. p. 0055-9.