Introduction
Food safety and food control have been recognised as important issues worldwide. For more than a century, developments in food animal production and new control approaches have contributed to new food safety systems in most developed countries considered by many to be effective in the reduction and prevention of food borne diseases. Food safety of poultry products remains a serious problem in many countries in the world. Each year, an estimated 76 million people experience food borne infections in the United States, causing 325,000 hospitalisations and 5,000 deaths (Mead et al., Reference MEAD, SLUTSKER, DIETZ, MCCAIG, BRESEE, SHAPIRO, GRIFFIN and TAUSE1999). Food borne illnesses from Salmonella enteritidis in eggs alone were estimated to cause 182,060 cases in the United States during the year 2000 (Schroeder et al., Reference SCHROEDER, NAUGLE, SCHLOSSER, HOGUE, ANGULO, ROSE, EBEL, DISNEY, HOLT and GOLDMAN2005). Data from the national surveillance system in England and Wales revealed that from 1996 to 2000, an estimated 1,724,315 cases of indigenous food borne diseases per year resulted in 21,997 hospitalisations and 687 deaths (Adak et al., Reference ADAK, MEAKINS, YIP, LOPMAN and O'BRIEN2005).
According to the study and reports made by the World Health Organization (WHO) and Food and Agriculture Organization (FAO) of the United Nations (2002), illness due to contaminated food is one of the most widespread health problems in the world and an important cause of reduced economic productivity, especially in developing and under developed countries. The rate of incidence of food borne diseases differs in different parts of the world; in industrial countries many such maladies do not exist or have been halted due to food safety education, higher standards of hygiene, improved water supplies and sanitation, and the application of safe food processing technologies.
In the past, bacteria, parasites and viruses were the most biological important causal agents of diseases in humans consuming contaminated food. Although, these organisms still play a major role in creating health problems in humans, new hazards, including veterinary drug residues, pesticides and other contaminants, such as heavy metals and environmental agents, are additional pollutants which are important biological factors. Residues in poultry products are leftovers of compounds used in the production of birds to enhance productivity and reduce or eliminate disease organisms or parasites. Antibiotics are used by the poultry industry and poultry veterinarians to enhance growth and feed efficiency and reduce diseases. Coccidiostats, antimicrobials, wormers, mould-inhibitors, toxin binders, and pesticides used for mites and/or lice control are potential residue sources. In addition, compounds used indirectly, such as rodenticides, insecticides, and herbicides, can become residues if birds come into contact with them. There is a legal requirement that drug concentrations in edible animal products are not at levels greater than those established as safe by the relevant regulatory authority in the country. In many countries of the world, this upper level is referred to as the ‘maximum residue level’ (MRL), while in United States it is termed as ‘tolerance’ (Riviere, Reference RIVIERE1999).
Poultry production in Iran
The Islamic Republic of Iran, which has a 1,648,195 square kilometre area, is located in the north eastern hemisphere between 25.3 to 39.47 latitude and 44.5 to 63.8 longitude in Asia. It is one of the world's most mountainous countries. This country has a variable climate. In the northwest, winters are cold with heavy snowfall and subfreezing temperatures during December and January. Spring and autumn are relatively mild, while summers are dry and hot. In the south, winters are mild and the summers are very hot, having average daily temperatures in July exceeding 38°C. The maximum and minimum annual rainfall in humid and dry regions of the country is 2000 mm and 30 mm respectively, with an annual mean of 270 mm for the country. Almost 12.3 million hectares, which accounts for 7.48% of the total area of the country, are cultivated and, considering the diversity in climatic conditions, production of many different agronomic and horticultural products is achievable (World Health Organization and Food and Agriculture Organization, 2002).
The poultry industry in Iran has been and is under dynamic and progressive development. At present, there is a pure broiler line producer and many farms for rearing grandparents (GP), parent stock (PS), broilers and layers. There are about 15 GP farms, which can supply the required PS flocks. The pure broiler line farm is well established now, and has the capacity to supply high quality GP flocks for the local market and export. In the year 2008, the numbers of broiler and layer PS farms were 490 and 18 units, respectively, and the numbers of commercial broiler and layer farms were 17,168 and 1,448 units, respectively. Meanwhile, different European breeding companies are also in the market and present their birds for GP and PS rearing. Most of the broiler farms are located closer to more densely populated regions and in the north (the wetter) part of the country. The poultry industry is private and some services are provided through the cooperatives. Few poultry farms are under government management and, according to the government policy for supporting privatisation, it is planned for these farms to be sold to the cooperatives and private sectors (Kamalzadeh et al., Reference KAMALZADEH, RAJABBAIGY, MOSLEHI and TORKASHVAND2009).
Common infectious diseases
Despite the advancements in the poultry industry, Iran's poultry industry is facing heavy losses caused by infectious diseases. In 1998 an outbreak of low pathogenic avian influenza virus (H9N2 subtype) occurred in the Iranian poultry industry (Pourbakhsh et al., Reference POURBAKHSH, KHODASHENAS, KIANIZADEH and GOODARZI2000; Vasfimarandi and Bozorgmehrifard, Reference VASFIMARANDI and BOZORGMEHRIFARD2002; Nili and Asasi, Reference NILI and ASASI2003). Since then, mixed infections of the influenza virus with other respiratory pathogens, particularly the infectious bronchitis virus, Mycoplasma gallisepticum and avian pathogenic Escherichia coli are thought to be responsible for high mortality rates and significant economic losses in chicken and turkey flocks (Seifi et al., Reference SEIFI, ASASI and MOHAMMADI2010; Hadipour et al., Reference HADIPOUR, HABIBI, GOLCHIN, M.R. and SHAYANPOUR2011). There can be little doubt that the severe form of Newcastle disease (ND) is a serious problem either as an enzootic disease or as a cause of regular, frequent epizootics throughout some areas of Africa, Asia, and Central and South America (Spradbrow, Reference SPRADBROW1988). Iran's poultry industry suffers from ND, due to both occasional outbreaks and vaccination costs. More recently, the prevalence of avian metapneumovirus (aMPV) infection was reported in broiler and broiler breeder chickens in Iran (Rahimi, Reference RAHIMI2011). In the past few years, the prevalence of emerging poultry pathogens such as Ornithobacterium rhinotracheale has also been reported from different parts of Iran (Banani et al., Reference BANANI, MOMAYEZ, POURBAKHSH, GOODARZI and BAHMANINEJAD2002; Allymehr, Reference ALLYMEHR2003; Rahimi and Banani, Reference RAHIMI and BANANI2007; Asadpour et al., Reference ASADPOUR, BOZORGMEHRIFARD, POURBAKHSH, BANANI and CHARKHKAR2008; Rahimi et al., Reference RAHIMI, MOHAMMADI and MOHAMMADZADEH2012). There are issues needing attention, particularly the food borne diseases of humans caused by pathogenic bacteria, drug and chemical residues (World Health Organization, Reference WORLD HEALTH ORGANIZATION2000), because laboratory-based surveillance may not be employed throughout the entire food production chain (World Health Organization, Reference WORLD HEALTH ORGANIZATION2002).
Food safety controls
Iran intends to standardise and support the exportation of products. Similar to many other countries, the development of food safety standards is handled by governmental bodies such as Ministries of Agriculture (the Iran Veterinary Organisation, IVO), Health and Medical Education, and the Institute of Standards and Industrial Research. In the mean time, research continues on the promotion of national food safety quality (World Health Organization and Food and Agriculture Organization, 2002). In spite of the advances in this field, the issue of food borne pathogens and drug and chemical residues remains. For instance, oxytetracycline (Salehzadeh et al., Reference SALEHZADEH, MADANI, SALEHZADEH, ROKNI and GOLCHINEFAR2006) and enrofloxacin residues (Salehzadeh et al., Reference SALEHZADEH, SALEHZADEH, ROKNI, MADADI and GOLCHINEFAR2007) have been found above the MRL in chicken tissues in Iran. Recommended antimicrobial withdrawal times are not implemented by some poultry farmers in Iran. Resistance of E. coli isolates recovered from poultry to a variety of antimicrobial drugs has been reported from different parts of Iran (Tabatabaei and Nasirian, Reference TABATABAEI and NASIRIAN2003; Salehi and Bonab, Reference SALEHI and BONAB2006; Saberfar et al., Reference SABERFAR, POURAKBARI, CHABOKDAVAN and DOLATSHAHI2008). Multiple drug resistance has been found in 63.3% of E. coli isolates recovered from chickens with colibacillosis in west of Iran (Rahimi, unpublished work). Hashemy-Tonkabony and Mosstofian (Reference HASHEMY-TONKABONY and MOSSTOFIAN1979) detected varying concentrations of chlorinated pesticide, dichlorodiphenyltrichloroethane (DDT), dieldrin, and aldrin residues in chicken egg, throughout the Tehran and Mazandaran provinces.
Almost all market type poultry produced in Iran are slaughtered in modern industrial slaughterhouses, which number more than 200 across the country. The IVO is responsible for the supervision for all kinds of food derived from animals. It has appointed meat inspectors in all processing plants, including slaughterhouses. Meat inspection at poultry processing plants has been successful, but obviously has certain limitations. More importantly, the drug, pesticide, mycotoxin and other chemical residues must be detected and monitored in poultry meat and eggs. This work has to be carried out in close collaboration with human and environmental health professionals, analysts, epidemiologists, poultry farmers, processors, and traders. In rural areas and small towns, live bird markets are the main sources of providing poultry meat and eggs for customers. Live bird markets and rural shambles may be the most important health hazards in the country, as they make it too difficult to control and eradicate poultry diseases on these sites, and, as a result, there is no hygienic control on poultry meat and eggs sold in such markets.
Effective food safety management requires multidisciplinary scientific and technical inputs, and a high level of communication and consultation with all interested parties. Veterinarians have a major role to play in this process (Institute of Food Technologists, Reference INSTITUTE of FOOD TECHNOLOGISTS2001). Poultry veterinarians may provide poultry farmers with information, advice and training on how to avoid, eliminate or control food safety hazards including drug and pesticide residues, mycotoxins and environmental contaminants in poultry production. Numerous poultry farms are located in some geographically restricted areas in Iran which can lead to poultry health, food safety, environmental, and human health problems due to improper implementation of biosecurity measures. Iranian poultry veterinarians and IVO need to play a decision-making role in the development of the poultry industry, because it is the veterinarian who is likely to recognise problems in concentrated poultry production farms within these restricted areas.
The ultimate goal of poultry food safety systems is establishing public trust and consumer confidence. It is recommended that control should be made at the farm level and poultry processing plants in order to realise a comprehensive food safety control from the farm to the consumer's table. Authorities should inform and educate the public about the hazards of drug residues in poultry products. The IVO and Iran Veterinary Council should provide regular training courses for poultry producers in relation to overall food safety measures. Interdisciplinary collaboration in food safety among poultry producers, poultry processors, retail markets and consumers is an emerging necessity.
Conclusions
In spite of the advances in the poultry industry in Iran, the issue of food borne pathogens and drug and chemical residues remains. Recommended antimicrobial withdrawal times are not implemented by some poultry farmers in Iran, and laboratory-based surveillance may not be employed throughout the entire food production chain. There is a legal requirement that drug concentrations in edible poultry products are not at levels greater than those established as safe by the relevant regulatory authority in the country. Mandatory regulatory activity for enforcement by authorities is required to ensure that all poultry products are safe for human consumption.
