Guidelines for the Use of Antibiotic Drugs

Antibiotic drugs are commonly used in veterinary medicine to treat infectious diseases that are caused by bacteria and certain other microorganisms. There are many different classes of antibiotics available for use in animals, including penicillins, cephalosporins, cephamycins, aminoglycosides, quinolones, sulfonamides, tetracyclines, and macrolides. Some are effective against a wide range of organisms, while others are more closely targeted (for example, they may be effective against some bacteria but less effective against other bacteria). Thus, antibiotics are often referred to as broad-spectrum or narrow-spectrum drugs, respectively.

Successful antibiotic treatment is based on 4 principles: 1) identifying the disease-causing agent and selecting the appropriate drug for treatment; 2) attaining effective concentrations of the drug at the site of infection for a sufficient period of time; 3) choosing a dose rate, frequency, and method of administering the dose that maximizes the likelihood of a cure, prevents relapse, and minimizes the risk of developing resistance while causing no harm to the animal; and 4) using specific and appropriate supportive treatment to improve the animal’s ability to overcome the infection and associated disease conditions.

The emergence of bacteria that are resistant to currently available antibiotics within the animal or human population is of great concern. When resistance occurs, previously successful drugs can no longer be considered effective treatment, and new drugs must be developed. Resistance may develop in several different ways. However, when used properly (that is, the right antibiotic is used and it is given as prescribed for the appropriate amount of time), antibiotics are less likely to contribute to the selection of antibiotic-resistant organisms.

When given a prescription from your veterinarian for your pet, make sure that it is given exactly as instructed and that the entire prescription is given. Not following dosage schedules or not giving all of the prescription can cause a relapse, a reinfection, or development of antibiotic-resistant organisms.

Anthelmintic drugs

Anthelmintics are drugs that are used to treat infections with parasitic worms. This includes both flat worms, e.g., flukes and tapeworms and round worms, i.e., nematodes. They are of huge importance for human tropical medicine and for veterinary medicine. The World Health Organization estimates that a staggering 2 billion people harbour parasitic worm infections. Parasitic worms also infect livestock and crops, affecting food production with a resultant economic impact. Also of importance is the infection of domestic pets. Indeed, the companion animal market is a major economic consideration for animal health companies undertaking drug discovery programmes. Despite the prevalence of parasitic worms, anthelmintic drug discovery is the poor relation of the pharmaceutical industry. The simple reason is that the nations which suffer most from these tropical diseases have little money to invest in drug discovery or therapy. It comes as no surprise therefore that the drugs available for human treatment were first developed as veterinary medicines. There is thus a pitifully small repertoire of chemotherapeutic agents available for treatment (see Table 1). In some respects, this situation has been exacerbated by the remarkable success of ivermectin over the last twenty years (Geary, 2005), which has decreased motivation for anthelmintic drug discovery programmes (Geary, Sangster and Thompson, 1999). This prompts concern, as anthelmintic resistance has been widely reported in livestock and it may also only be a matter of time before this phenomenon occurs in parasites of humans.

Broad spectrum anthelmintics are effective against parasitic flat worms and nematodes. However, the majority of drugs are more limited in their action, e.g., praziquantel, a drug used in the treatment of schistosomiasis and thought to act by disrupting calcium homeostasis (Greenberg, 2005), has no activity against nematodes (see Table 1). For the purpose of this review we will focus on drugs used in human and veterinary medicine to treat parasitic nematode infection.