Antibiotic use in animals

Of the boons vouchsafed to humanity, the discovery and development of penicillin is one of the greatest. That golden era has passed and few, if any, new discoveries are in prospect. Dr Patrick and his colleagues (BCMJ 2004;9:472) in his report from the BC Centre for Disease Control, has expressed his concern that the beneficial effects of the antibiotics are being lost due to ill-advised usage. Dr Patrick elaborates on the reasons for the emergence of drug resistance but not the mechanisms and lays much of the responsibility on the medical profession. In passing he draws attention to the widespread use of these drugs in animals.

A visit to the agricultural side of my family is revealing in this regard. The pig operation, located just outside Bromsgrove, produces about 36 000 porkers a year, and with so many animals crowded into so small a space infection control is simply a matter of survival. Visitors to the site are about as welcome as a call from the tax department. The pig feed, which is delivered in bulk tractor trailer units, is mixed with tetracycline. The feed compounders buy their antibiotic, not in capsules, but in drums. The beneficial effect to the breeders is that conversion of feed to pig meat is about 4:1 and is significantly improved so that the extra cost of antibiotics is more than covered. The fermenters, and by this I mean those manufacturing industrial-scale antibiotics, and not the beverages, tea, cocoa and alcohol, are also content because they too can look forward to healthy profits.

Having spent some time exercising race horses I encountered a similar but less dramatic antibiotic abuse. If a horse has catarrh (“the snots”) or a cough (“the pimples”) a large draught or “drench” of penicillin is called for. If exhibition of drugs can make a difference of as little as two seconds in a half-mile race and it means a five-figure cheque, the decision is an easy one. So prevalent is medication of one kind or another that winning animals are routinely tested for drugs, including antibiotics. The knowledgeable trainer is fully familiar with the half lives of the drugs she is using and takes a lively interest in such matters.

Similarly two of my nephews have herds of milking cows. These huge Holsteins have udders like cart wheels commensurate with the ten or more gallons of milk they yield in a day. Stimulated to ever greater production by injection of bovine somatomammotropin the animal does little but eat and chew the cud. The overstimulated teats with the large single lactiferous ducts are singularly prone to mastitis. Milk is routinely tested for the presence of antibiotics and milk from cows being treated must be excluded from sale. Would a farmer with hungry calves to feed and milk she is unable to sell pour it down the sewer? Another easy decision.

Worse yet is the abuse of second- and third-generation antibiotics by our veterinary colleagues in their treatment of pets. The love of those who are childless is being lavished on the anthropomorphized family pet. The veterinarian is complicit in keeping alive, often at enormous cost, pets whose life span has been exceeded. Should the neighborhood tomcat who caterwauls under my bedroom window develop chronic osteomyelitis after being bitten by one of his rivals, ought he to be administered triple antibiotic therapy? Not if I have any say in the matter.

The problems enumerated are much greater than those described by Dr Leslie Andrews (BCMJ 2005;47:9) who decries the advertising for antibiotic lotions and over-the-counter drugs. It is axiomatic that people will act in their own best short-term interests: to exhort responsible behavior is pointless. We are, through ignorance and greed, witnessing the loss of one of our most important therapeutic agents. Should we merely shrug our shoulders in resignation and accept that we have been the authors of our own misfortunes, or should we restrict the use of the few really effective third-line drugs to a limited number of experts, for example infectious disease consultants, as we have with certain other drugs such as methadone? The huge increase of the world’s population has been sustained by control of infection. To feed that increase we have the factory farms and fish farms which in turn need antibiotics to maximize production. The circle is complete.

Dr Patrick and his colleagues have written an authoritative report: its recommendations should be heeded.

—Ewart Woolley, MD
Vancouver