ANIMAL HEALTH & PRODUCTION ISSUES

This is a column that discusses current animal health and production problems in the tropics with special reference to events in the Nigerian industry. Dr. I. Charles Okoli is of The Tropical Animal Health and Production Research Laboratory, Department of Animal Science and Technology, Federal University of Technology, PMB 1526, Owerri, Nigeria. dr_charleso@yahoo.com All reactions to the issues raised in the column should be addressed to his E. mail address or to the Editor-in-Chief.

#Antibiotic Management in the Nigerian poultry industry

I N T R O D U C T I O N

Modern poultry production involves the rearing of high performing hybrid strains of chicken on commercial scales. It is a high-risk sensitive venture and presents certain challenges in terms of management, nutrition and maintenance of the productive health of the flock. The peculiar climatic features of the tropics favor high incidence of infectious diseases and this has provoked a liberal use of anti-microbial agents in poultry farms in most countries of the region. For example, although there is no available data on quantity of anti-microbial products utilized in animal production in Nigeria, reliance on these products especially in poultry production is common practice. Tetracycline is indicated as drug of choice in the management and prevention of most bacterial infections especially during the brooding stage and as growth promoting and egg laying enhancement agents for broilers and layers respectively. This practice invariably contributes to the evolution and spread of anti-microbial resistance among bacterial organisms responsible for such tropical infections.

In Nigeria, the level of anti-microbial resistance among bacterial isolates from poultry has reached an alarming state. A recent study revealed resistance among strains of avian E. coli isolated from a southeastern state to be as high as 97%. This study also demonstrated high level of resistance (60-93%) against the first line in-expensive readily available broad-spectrum antibiotics. In most cases of suspected bacterial infection in the Nigeria, the causative organism is never known hence diagnosis and antibiotic management of such cases may be based on scientifically unfounded empiric prescription. Thus, certain behavioral antecedents of persons involved directly or indirectly in the use of antibiotics have been found to influence selection for resistant organisms and this contributes to the escalating worldwide problem of anti-microbial resistance. This article reports the findings a recent study on the human factors associated with antibiotic resistance acquisition in poultry bacterial pathogens in Nigeria.

COMMERCIAL FIXED DOSE COMBINATIONS

An increasing number of soluble antibiotic powders imported into Nigeria for the treatment of poultry infections were found to contain fixed-dose combinations of anti-microbial substances. Our survey showed that 60% of the over 80 different antibiotic preparations marketed in the country contained four different antibiotics. Instances abound where oxytetracycline, chloramphenicol, streptomycin, neomycin and furazolidone or colistin, erythromycin, streptomycin, oxytetracycline and chloramphenicol were combined in a single commercial product.

The rational behind this practice is questioned since such products may contain sub-optimal levels of the various active compounds and it may not be possible to effect an increase in the dose rate of any one drug in the combination without increasing the others. Furthermore, continuous use of such products may result in a concurrent development of resistance against the various antibiotics. More importantly, where mutual compatibility is doubtful or pharmacodynamics of the combined drugs are not similar, they may induce toxicity and cause damage to the vital organs.

UNREGULATED RETAILING OF VETERINARY DRUGS

In Nigeria, any veterinary pharmaceutical can be purchased without prescription. In southeastern Nigeria, hawkers, small traders and illiterate market women were actively involved in the retailing of veterinary drugs especially poultry medicines. Our surveys showed that in this part of the country 69.9% (110 out of 158 veterinary drug outlets) were manned by unqualified persons. In Onitsha in particular, as much as 90.2% of these outlets were being controlled by semi-literate traders. Pharmacists were found to be completely uninvolved in such businesses.

Soluble antibiotic powders were usually dispensed in small quantities of less than 5gm and then wrapped with transparent polythene material by these retailers. Such repacked drugs usually remain on display for long periods fully exposed to harsh tropical sunlight, high ambient temperatures and humidity. Farmers for the treatment of any condition subsequently use these compromised drugs. Often the correct dosage of the drug is not used or may even be administered against the wrong ailment. Similarly, most human drug vendors in Nigeria have been shown to exhibit little knowledge of dosage, regimen, indications and contraindications.

POOR HANDLING AND STORAGE OF ANTIMICROBIAL DRUGS

The conditions of storage of pharmaceuticals awaiting clearance at the Nigerian ports were found grossly inadequate. Medicines were stored in open halls with other imported goods or left in shipping containers for long periods. During transportation to the various markets, medicines were usually exposed to adverse tropical conditions. Drugs manufactured according to the standards of temperate environment are known to become degraded under such conditions. Furthermore, prolonged exposure of anti-microbial drugs to the vagaries of the tropical climate has been shown to seriously affect the products’ ability to treat clinical illness. Most poultry farmers in Nigeria hardly consider the reputation of drug suppliers and storage facilities available to them before purchasing their products.

Common errors observed in the on-farm handling and storage of veterinary pharmaceuticals included exposure of drugs to heat, improper storage of partly used products and contamination of products with dirty needles and scoops. Because of poor product rotation, drugs stocked in the farm sometimes expire before being used. These practices could readily compromise such therapeutic products.

ANTIBIOTICS MISUSE BY FARMERS

The development of efficacious therapeutic agents and selective use of correct medicine has helped the poultry industry to take root in most developing countries. However, the Nigerian poultry industry may currently be threatened by on-farm indiscriminate use of highly potent compounds, which ordinarily require careful selection and usage. Misuse of therapeutic agents by farmers was found to arise through unintelligent use of human preparations for the treatment of poultry disease, poor compliance to veterinary prescriptions and lack of observation of withdrawal instructions of the manufacturers.

Use Of Human Drugs For Treatment Of Poultry Diseases

The need to cut costs has led many poultry farmers in Nigeria to increasingly use human preparations for the treatment of poultry illnesses. Our survey showed that 20% of 110 and 40% of 120 poultry farmers interviewed in southwestern and southeastern Nigeria respectively used human anti-microbial preparations regularly in the treatment of poultry infections. Human chemotherapeutic preparations routinely employed for this purpose included tetracyclines, ampicillin, chloramphenicol and amoxycillin capsules; erythromycin, trimethopri - sulfur, metronidazole and triple sulfur tablets. Streptomycin, procaine penicillin and gentamycin injectable solutions and powders were also in common use.

Such practices are clearly wrong since the intensity of response and duration of therapeutic activity of a drug may differ widely between humans and chickens in accordance with body temperature, pH of the gastrointestinal tract, physiological pattern of metabolism and competence of excretory mechanism. Furthermore, when illiterate farmers use these human preparations in the treatment of poultry diseases, the tendency to over dose or under dose may arise.

Poor Compliance To Veterinary Prescriptions

It was a common practice for cost conscious farmers to purchase incomplete regimens of prescribed drugs and discontinue treatment when symptoms disappear even though the pathogen may not have been eliminated. Sometimes, the long distance between the farm and the nearest veterinary shop may hinder the farmer from making a follow-up visit or the veterinarian may be hindered from visiting such farms because of inability of the farmer to foot call fees.

Many poultry farmers in the study area were found to be either semi-literate or out-rightly illiterate and were unable to read or understand drug labels. Strict compliance to veterinary prescriptions is important since early discontinuation of therapy or interruption of usage may cause relapse of infection or induce resistance.

Refusal To Observe Withdrawal Instructions

Most anti-microbial drugs distributed in Nigeria carry printed instructions to the user on certain withdrawal interval during which animal products were considered unfit for human consumption. This period of withdrawal is intended to help prevent the transfer of sub-therapeutic levels of the drug to the consumer through meat or egg. This aspect of disease treatment was found to hardly receive attention in Nigeria probably because of the absence of functional insurance cover of most farming operations.

Consumption of sick or dead birds currently receiving antibiotic medication was also common in most parts of the country. Sub-therapeutic levels of antibiotics in the meat of such dead fowls could lead to the development of multi-drug resistance factors in bacteria strains. Such multi-drug resistant factors harboring bacterial strains can be disseminated in the environment and become the major candidates for selection of resistance during subsequent anti-microbial exposure.

ANTIBIOTICS MISUSE BY UNSKILLED ANIMAL HEALTH PRACTITIONERS

In many African countries, including Nigeria, the number of well-trained animal health personnel is well below the recommended ratio of 20,000 Veterinary Livestock Unit (VLU) per veterinarian. Because of this limited number of trained veterinarians, greater reliance is usually placed on auxiliary personnel in Nigeria. These auxiliary personnel may possess just a couple of weeks to a few years of formal veterinary training. Although field experience can greatly enhance their capabilities, auxiliaries are seldom adequate substitutes for trained veterinarians. Thus, the quality of care and advice the auxiliary may provide may be inadequate. For example, such may be less aware of the deleterious effects of inappropriate antibiotic use.

In addition, many untrained drug sellers were found to offer alternatives when the prescribed drugs were out of stock or refilled prescriptions without consulting the prescriber. A high proportion of poultry farmers in Nigeria preferred the services of unskilled practitioners because of the cheaper immediate cost of consulting them and only consulted trained veterinarians when misdiagnosis and complications arose.

ANTIBIOTICS MISUSE BY VETERINARIANS IN POULTRY PRACTICE

These were found to arise through excessive prescription of antibiotics, errors due to water medication and lack of anti-microbial susceptibility testing.

Excessive Prescription Of Antibiotics

A prevailing practice of prescribing antibiotics for just about any poultry problem by veterinarians was observed in the Nigerian poultry industry. While the relationship between anti-microbial use and the emergence and spread of resistance may be complex, the phenomenal increase in the use of antibiotics in animal production has been partly linked with the escalating rates of bacterial resistance worldwide. Since anti-microbial use provides selective pressure favoring resistant bacterial strains and inappropriate use increases the risk for selection and dissemination of anti-microbial resistant bacteria, which are placed at a competitive advantage, a sound regimen of bio-security to enforce prophylaxis against infections should remain the priority of all poultry practitioners. The professional competence and discretionary acumen of the poultry practitioners are called to task here, since almost every ailment tends to appear as a multidimensional problem in terms of signs, symptoms, lesions, morbidity and mortality and hence demands a holistic therapeutic approach. To prescribe a line of treatment therefore calls for in-dept awareness of the interaction between the animal body, drug and the disease causing organisms.

Errors Due To Water Medication

The most common cause of drug under-dosing or overdosing in poultry practice in Nigeria was found to be through water medication or the volumetric dosage approach. Errors usually arose through inconsistencies and variability in water consumption. A recent review of the sources of error from this type of medication, stated that discrepancies in water consumption rates brought about by variations in environmental temperature, types of feed ingredients, water quality, body weight, species and flock health could adversely affect the amount of drugs consumed by the bird. Practitioners during medication in Nigerian poultry industry hardly ever considered these variables. Anti-microbial therapy based on milligrams of units dosed per kilogram of body weight has been found more precise in providing more accurate and scientifically sound dosage regimen in poultry practice.

Lack Of Antimicrobial Susceptibility Testing

Poultry practitioners in Nigeria are hardly ever guided by susceptibility testing mostly because they found it easier to dispense drugs without going through the laborious process of susceptibility testing. For example our study carried out among poultry practitioners in December 1998 showed that 85% of the 120 veterinarians interviewed had not sent samples to a laboratory for susceptibility testing in the previous three years. Reasons given for this included lack of functional veterinary diagnostic labs. and clients’ unwillingness to absorb the extra cost of susceptibility testing. Furthermore, 50% of skilled and 19.3% of unskilled practitioners felt that presenting signs and lesions were suggestive enough and therefore are enough aid in arriving at a diagnosis. Ten percent and 28.6% of the skilled and unskilled practitioners respectively also felt that susceptibility results obtained from human diagnostic labs were unsuitable.

A well - standardized anti-microbial susceptibility assay provides reliable results that could serve as a veritable tool in the appropriate treatment of bacterial infections. Where this is lacking, the veterinarian becomes handicapped and usually resorts to empirical prescribing. Anti-microbial susceptibility patterns of bacterial isolates from poultry in Nigeria are currently unknown. In addition, national surveillance programs for antibiotic resistance in farm animals are not organized.

IMPORTATION OF POOR QUALITY ANTIMICROBIAL PRODUCTS

A lack of functional regulatory agency on the importation of human and veterinary pharmaceuticals was also observed during this study. This has created avenues for unscrupulous importers to flood the market with vast quantities of substandard products. Such substandard products have been reported to be either counterfeited or recycled and relabeled expired drugs.

The present investigation showed that most of these products remain undetected until they cause therapeutic failures at the farm level. Furthermore analytic equipment available to the regulatory agencies for the enforcement of standards are usually either inadequate or lacking entirely, hence their staff were unable to keep track of the profusion of brands and generic drugs circulating in the country. In addition, official and unofficial corruption arising from poor remuneration of concerned agency staff also compound the situation thereby creating avenues for the passage of substandard products into the market.

DISSEMINATION OF RESISTANT ORGANISMS

The warm humid tropical climate of most parts of Nigeria, and the poor application of basic concepts of management, hygiene and bio-security observed in most poultry operations in the country, are known to contribute to the high prevalence of infectious poultry diseases. For example this study revealed that 77.9% of poultry farmers in the southeastern states fail to carry out basic hygienic procedures such as microbiological analysis of poultry drinking water, vermin control, microbiological analysis of feedstuff and diseases screening of incoming stock. Other important management practices such as restriction of human movements, “all-in-all-out” system and segregation of different breeds of poultry were lacking or ineffectively enforced in the farms visited and may have contributed to the spread of anti-microbial resistant commensal and pathogenic organisms.

The sale and consumption of dead birds, a common practice in many parts of the country may also contribute to the spread of resistant organisms. Furthermore, the unhygienic disposal of poultry manure, overcrowding and crude handling of meat products commonly observed in many poultry farms might also enhance the spread of disease, the need for anti-microbial therapy and subsequent development of anti-microbial resistance. A lack of proper regulatory control and monitoring of trade in animal feeds, feed ingredients especially fish meal and breeding stock was equally observed in the country and may be implicated in the spread of antibiotic resistant bacteria.

SOLUTIONS

The recommendations of OIE, EEC and WHO for ensuring control of spread of infectious agent resistance factors and rational drug use could be adapted to local situations in the fight against the escalation of anti-microbial resistant commensal and pathogenic bacterial. The development and strict enforcement of sound regulatory policies in line with international standards could alleviate the misuse of anti-microbial drug by the different interest groups in the industry. Proper orientation of regulatory agency staff would help to fight corrupt practices, which may hamper efficient enforcement of import regulations. Continuing veterinary and public health education would help poultry practitioners and other key players in the industry to keep abreast of current techniques and information. Proper funding of relevant government institutions charged with veterinary public health and preventive medicine is also necessary. Moreover, a national surveillance program for anti-microbial resistance in poultry pathogens should be developed. Such surveillance should be conducted regularly and continuously because resistance rates can vary in one region of a country over time.

Finally, since development of anti-microbial resistance in animals and humans are related to anti-microbial use, there is need to establish joint monitoring programs for anti-microbial resistance in pathogenic and commensal bacteria of humans, food animals and their shared environment.

# This is a modified version of an article that was originally published in the volume 3 of International Journal Of Environmental Health And Human Development.