**1. Introduction: veterinary pharmaceuticals and antimicrobials**

Veterinary pharmaceuticals include drugs, medications, and other substances in use to treat or prevent animal diseases for health, growth promotion, and productivity [1]. These drugs can be broadly divided into categories according to the different pathogens or targeted infections. They include antiparasitic drugs, antiinflammatory, reproductive medication, surgical medications, anesthetics, nutritional drugs, and feed additives sometimes used as growth promoters (**Table 1**). Among commonly used drug in veterinary medicine are antibiotics. These drugs and medicaments can be administered in form of injectable, tablet, bolus, drench, and bath/wash or added to feed and drinking water. There are documented evidence of earlier norms and practices of animal husbandry regarding how shepherd and nomads provide


*Source: survey of commonly use veterinary antimicrobials in Nigeria, courtesy of Dr. Jolly Amoche of National Veterinary Research Institute, Vom.*

#### **Table 1.**

*Some veterinary pharmaceuticals distributed in Nigeria.*

medication for livestock. Some were written document by priests in monasteries, such as the use of garlic (*Allium sativum L.*) and ointment made from honey and grease [2]. This is similar to what has now been recognized in modern veterinary medicine as ethno-veterinary or alternative medicine in human and according to the World Health Organization (WHO); 75% of the world's population are using herbs for basic healthcare [3]. Such practices predate modern day pharmacopeia, which has, however, refined and synthesized the delivery of veterinary and human medicines. Some global industrial leaders in modern veterinary pharmaceuticals include Zoetis (formerly Pfizer Animal Health), Merck, Bayer, Elanco Animal Health, Boehringer Ingelheim Animal Health (Merial), Norvatis Animal Health, and many others. These companies and their subsidiaries are engaged in the multibillion dollars profitable business of drug distribution in developing countries (and also from Asia to Africa) in millions of doses some of which may be overused and contributing to drug resistance [4, 5].

#### *Veterinary Pharmaceuticals and Antimicrobial Resistance in Developing Countries DOI: http://dx.doi.org/10.5772/intechopen.84888*

Globally, there are more livestock in the world than human, with livestock systems occupying about 30% of the planet's ice-free terrestrial surface area [6]. Most of these animals are kept in free range husbandry systems in under-developed countries where the enterprise supports the livelihood of about 600 million small holders [7]. The livestock sector in developing countries is also evolving in response to rapidly increasing demand for livestock products with changes in the demand for livestock products being driven among other factors by human population growth, urbanization, and increasing income [8, 9].

A major limiting factor in profitable livestock production in developing country is the burden of infectious diseases. These livestock diseases cause great socioeconomic impact, and the burdens are most of the time exasperated by poor biosecurity in both intensive and open production systems. This has made the use of antimicrobials for treatment of diseases indispensable [10]. It is important to emphasize that the reduction in the burden of infectious livestock diseases has been possible due in part to the use of a wide range effective drugs and vaccines and improvements in diagnostic techniques and services [11].

Therapeutic treatments are targeted at animals that are diseased. In food animals, it is usually often more convenient to treat entire groups by administering medication through feed or water, though individual animals may also be treated. For animals like poultry and fish, mass medication is the most feasible means of treatment but with the possibility of drug dispersal into the environment via leaching and agricultural wastewater [12]. Furthermore, certain mass-medication procedures called metaphylaxis, aimed at treatment of sick animals while medicating others in the group that may not be sick but exposed, can also be counterproductive. Other prophylactic antimicrobial treatments are typically used during high-risk periods for infectious diseases even, while the animals may not be infected also described as nonspecific infection prevention [13]. These practices, however plausible, are currently considered as contributing to emergence of antimicrobial resistance due to subtherapeutic exposure to veterinary pharmaceuticals by both infected and noninfected animals, as well as the environment [14].

Antimicrobial resistance has been described as the ability of bacterial, parasites, viruses, and fungi to survive and spread despite treatment with specific and combination therapy that are normally used against them [15]. The World Health Organization also emphasized that resistance happens when microorganisms change when they are exposed to antimicrobial drugs (such as antibiotics, antifungals, antivirals, antimalarials, and antihelmintics). These microorganisms that develop antimicrobial resistance are sometimes referred to as "superbugs". Antimicrobial resistance may be spontaneous and occur as a natural process, and resistance to antimicrobials dates back as far as when the first generations of antibiotics including penicillin were introduced in 1943/44 by Alexander Fleming [13]. In evolution, selection pressure is bound to cause subpopulation of microorganism with resistance genes to emerge [16]. This selective pressure has been ascribed to appropriate and inappropriate use of antimicrobials but aggravated by (1) intensity of usage, (2) persistence of usage, (3) under usage and subtherapeutic doses that animals are exposed to in prophylactic treatment, and (4) unintended human exposure through antimicrobials in food residues and the environment [10].

The burden of infectious diseases in developing countries and intensive use of antimicrobials to combat this has also been stressed in a study that suggested that up to a third of the global increase (67%) in antibiotic consumption will be in food animals, over the period 2010–2030 and attributable to low-middle income countries [17]. This challenge is in view of the high burden of foodborne infectious and zoonotic diseases especially also in developing countries [18]. Veterinary practices use drugs for mitigating these diseases in animals, including food animals that

have to be maintained in health and productivity (meat, egg, and milk). To prevent these drugs from getting into the food chain and being consumed by humans, "withdrawal time," which is the last time any drug may be administered before egg/milk and meat from such animals are collected and consumed is specified. The withdrawal time for antimicrobials is intended to prevent harmful drug residues in meat, milk, and eggs [19]. These waiting periods need to be observed from the time of treatment to when the animals are slaughtered for food. This is important because food products that contain antimicrobial residues not metabolized leaves residues beyond permissible limits at the end of the withdrawal period may be considered unwholesome for consumption and may contribute to antimicrobial resistance in humans [20].

Veterinary pharmaceuticals, therefore, contribute in many ways to the emergence of antimicrobial resistance either directly in suboptimal usage in animals or indirectly in human who consume subtherapeutic doses in animal products [13]. When resistant organism emerges, it has also been argued that human sources also seed these resistant bacteria to animals and the environment through sewage [21]. A recent study by Marcelino et al. [22] described high levels of antibiotic resistance gene expression among birds living in a wastewater treatment plants. The study observed that birds feeding at a wastewater treatment plant carried greatest resistance gene burden, suggesting that human waste, even after treatment, contributes to the spread of antibiotic resistance genes to the wild. Domestic and wild animals, including rodents, and birds, can acquire these environmental contaminants and pass them on via their excreta to grazing land or feed of food animals, which may in turn end up in human through the food chain [23]. While it is imperative to canvass AMR stewardship through rational and circumspect usage of antimicrobial in animals, it is important to bear in mind that human also present risk to animals. The USFD described the phenomenon of antimicrobial resistance as a very complex and nonvictimless phenomenon, affecting both human and animal health [13].

### **2. Livestock diseases and the application of veterinary pharmaceuticals**

In the management of infectious and noninfectious diseases of livestock in developing countries, a number of veterinary pharmaceuticals are administered. The choice of drugs is often determined by efficacy, availability, and cost. These factors are explored by manufacturers mostly based in developed countries from where the drugs are exported to developing countries. This distribution chain is also largely driven by business interest such that drug companies sell volumes that are targeted at frequent, intensive usage that may have deleterious effect such as emergence of AMR.

Intensive use of veterinary chemotherapy on the other hand may be justifiable considering that many bacterial, viral, and parasitic diseases like mycoplasmosis, Newcastle disease, avian influenza, anthrax, coccidiosis, brucellosis, foot and mouth disease (FMD), rift valley fever, etc. threatens socioeconomics, instills fear that shock systems, either by suddenly and rapidly killing large number of animals or causes large-scale drop in demand through fear of zoonotic diseases [24, 25]. On the other hand, the growing concern that animals are major sources of human diseases and that around 60% of all animal diseases are zoonotic [26] make treatment of such diseases in animals an essential control measure before it is transmitted to human, and to reduce their capacity to cause epidemics and pandemics.

The livability and economic impacts of animal disease disaster is well documented, for instance, highly pathogenic avian influenza recently killed millions of poultry birds in Nigeria (including other countries in West Africa) and wiped out entire farms [27]. The costs of epidemic African swine fever in Cote d'Ivoire was estimated at

*Veterinary Pharmaceuticals and Antimicrobial Resistance in Developing Countries DOI: http://dx.doi.org/10.5772/intechopen.84888*

\$9.2 million; Nipah virus in Malaysia \$114 million, while contagious bovine pleuropneumonia in Botswana costs about \$300 million [25]. In the absence of preventive measures such as biosecurity and vaccination, the use of antimicrobial especially for nonviral infections is essential for profitable livestock production and to prevent infections that may be transmitted from animals to human as attested to by WHO [28].
