Microsoft word - the one health concept in low resource countries.doc
The One Health concept in low resource countries: Literature review Tanguy MARCOTTY, April 2009 Department of Animal Health, Institute of Tropical Medicine, Antwerp, Belgium
The “One Health” or “One Medicine” concept was first formally introduced by Calvin W Schwabe in his book “Veterinary Medicine and Human Health” (Schwabe, 1984). It was then supported by numerous authors who refined the idea and advocated for a close collaboration between the medical and the veterinary professions, both in industrialised (Kahn, 2006; Steele, 2008; Murphy, 2008) and in low-resource countries (Zinsstag et al., 2005; WHO, 2006). The “One Health” concept includes the impact animal husbandry has on human welfare as a source of food and power, the role of infectious disease reservoir played by wild and domestic animals (zoonoses), the fact that a number of drugs are used both in animals and human beings raising the question of transfer of drug resistance and, notably, the use of animals as epidemiological and experimental models in a huge number of fields ranging from anatomy to epidemiology, including physiology, immunology, pharmacology and surgery (Gryseels and Berkvens, 1999; Cardiff et al., 2008; Sargeant, 2008). Also, for certain diseases such as tuberculosis, pathogens occurring both in human beings and in animals can be advantageously studied in animals to improve their understanding in man. Natural hosts were found to be more appropriate for such studies than laboratory animals (Van Rhijn et al., 2008). Some authors suggest that the one health concept also covers the interdependence of health in various regions of the world: the world has become a global village in terms of infectious diseases and exposure to pollutants and contaminants. Finally, the various types of medicine, including ethnomedicine, have as common objective to contribute to health (Green, 1998).
Animals are used throughout the world as a source of food, power and welfare. Zinsstag (2001) reviewed how outbreaks in livestock can affect indirectly farmer’s health, mostly from a psychological perspective. In low-resource countries outbreaks in livestock also have significant effects on livelihood, production and availability of food and, eventually, on people’s health (Boonstra et al., 2001). Zoonosis and diseases emerging from animals may have direct impacts on human health.
Zoonoses are diseases that can be transmitted naturally from animals to human beings. They constitute a large proportion of the emerging infectious diseases of humans at the start of the 21st century. According to Taylor et al. (2001), who catalogued 1 415 known human pathogens, 62% were of zoonotic origin. Zoonoses can be classified according to the species acting as reservoir, the target species and the mode of transmission. A reservoir is usually defined as an epidemiological unit in which pathogens are maintained and from which they are transmitted to the target population (Haydon et al., 2002). From a medical perspective, humans are the target population or the population of interest. Ashford (2003) refined the definition and proposed to consider a reservoir as an ecologic system in which an infectious agent survives indefinitely. Such a reservoir system
includes all ecological components (appropriate hosts, population size and interactions) that are required for the maintenance of the pathogen. Yet, animals do not only play a major role in the maintenance of zoonotic pathogens, they are also the source of emerging human pathogens (Taylor et al., 2001; Feldmann et al., 2002), including HIV/AIDS (Wain et al., 2007), SARS (Cheng et al., 2007), Ebola, H5N1 influenza. Some authors showed how increased contacts and interactions between man and wild or domestic animals can increase the risk of emergence of new human diseases (Reluga et al., 2007; Jones et al., 2008). It is therefore in the interest of both the animal health and the medical sectors to collaborate in the surveillance of zoonotic and emerging infections and their control (Rezza, 2007).
Endemic zoonoses such as bovine tuberculosis, brucellosis, anthrax, rabies, trypanosomosis, leishmaniosis, hydatidosis or cysticercosis are often neglected in low-resource countries (WHO, 2006). In these countries, their impact on the human target population is often poorly documented, particularly for those that are difficult to diagnose as bovine tuberculosis, brucellosis, trypanosomosis and cysticercosis (Cosivi et al., 1995; Sheik-Mohamed and Velema, 1999; Zoli et al., 2003). The presence of zoonotic agents in livestock or wildlife and the practice of risk behaviours by the communities have been extensively described. However, data on the actual transmission of the pathogens to man, the severity of such infections, the perception people have of these infections and the need for control are scarce. Some authors emphasized on the relevance and the need for the veterinary and the public health sectors to collaborate on disease surveillance (King and Khabbaz, 2003; Stark et al., 2006), control (Zinsstag et al., 2007) and service delivery (Mathias, 1998; McCorkle and Green, 1998; Zinsstag et al., 2005), especially as resources are limited (Torgerson and Torgerson, 2008). Joint disease surveillance implies that information is shared when outbreaks occur in humans or animals. As far as the control of zoonoses is concerned, intersectoral collaboration is required to define cost-efficient control or eradication strategies. Finally, given the fact that veterinary and public health services require the same type of biological specimen collections, biomedical analyses, transfer of information, drug and vaccine storage facilities, intersectoral collaboration is likely to be very beneficial for all (Schwabe, 1998; Schelling et al., 2007).
Independently of the obvious interdependence of medical and veterinary epidemiology in the field of zoonotic infections, methodologies and concepts developed in veterinary epidemiology prove to be useful for medical epidemiology (Sargeant, 2008). Indeed, epidemiological studies are much easier to carry out in animals than in people and the mechanisms of disease transmission and immunity are similar. For instance, the concept of endemic stability was first used in the veterinary profession (Coleman et al., 2001).
The “One Health” concept also applies to the fact that the whole world is concerned about disease outbreaks occurring anywhere in the world (Lashley, 2006). Recent outbreaks like HIV/AIDS (Gilbert et al., 2007), SARS (Skowronski et al., 2005) and chikungunya (Das et al., 2007; Simon et al., 2008; Townson and Nathan, 2008) illustrate how quickly and how widely diseases can spread. This should advocate for tight North-South collaboration for disease surveillance and control. Interestingly, some authors
(Guerin et al., 2007) propose to use European travellers as sentinels to detect emerging diseases in low-resource countries.
As far as drug resistance is concerned, the “One Health” concept is applicable to the appearance of resistance in zoonotic pathogens, the transfer of antibiotic resistance from animal commensals or pathogens to human pathogens and the lessons that were learned from the veterinary experience. Veterinary practices usually avoid using molecules that are used in human medicine to combat zoonotic pathogens. Chemotherapy in animals is indeed not favoured to control zoonoses that have serious impacts or threats on human health. The problem is more pronounced when antibiotics used in veterinary medicine or for increased production cause resistance in animal commensals or pathogens. These resistant bacteria might have the capacity to cause infections in human beings or to transfer their resistance gene to human pathogens (Moubareck et al., 2003; WHO, 2005). The environment, where a lot of bacteria are discharged from animals, probably plays an important role in the transfer of antibiotic resistance from livestock to humans and wildlife (Lillehaug et al., 2005; Sayah et al., 2005). Therefore, some authors advise to delay the emergence of antibiotic resistance as much as possible by using antibiotics as parsimoniously as possible both in animals and in people (WHO, 2005; Courvalin, 2008).
The veterinary profession has a great experience on drug resistance, particularly in helminthology and protozoology. The errors that caused the emergence of resistance against anthelminthics in animals were critically reviewed (Geerts et al., 1997). In spite of the warnings, the emergence of drug resistance in human hookworms, schistosomes (Cioli, 2000; Doenhoff et al., 2002; Fenwick et al., 2003), Onchocerca volvulus (Bourguinat et al., 2007; Osei-Atweneboana et al., 2007) and malaria (Enserink, 2008; Muller et al., 2009) have become a serious concern in tropical countries. The drug resistance mechanisms in human helminths appear to be worryingly similar to what was observed in animals (Geerts and Gryseels, 2000). These authors recommend a cautious use of anthelmintics in the field and questioned mass treatments against helminths (Gryseels, 2006).
Finally, it has been recognised that traditional medicine (or ethnomedicine) and scientific medicine have the same objectives (Green, 1998). In actual fact, ethnomedicine makes little differences between animal and human medicine (McCorkle and Martin, 1998) and thus has clearly integrated the “One Health” concept. However, ethnomedicine is based on different principles, sometimes incompatible with scientific medicine. They also address different aspects of diseases. Scientific medicine focuses more on the biology of the pathogen and on the physiopathology of the sick organism whereas ethnomedicine is mainly concerned about the pollution and personalistic aetiologies (Green, 1998). Therefore, the role of ethnomedicine focuses much more on social and psychological aspects, which proved to be highly important in the perception and the acceptance of pathology (Edginton et al., 2002). These aspects are usually neglected by modern medicines. A combination of modern and traditional medicine in a “One Health” initiative could be quite beneficial in low-economy countries (McCorkle and Green, 1998), particularly in the field of epidemiosurveillance, where traditional doctors could help in the early detection of diseases among animals or humans (Schwabe, 1984).
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LASIK Risk Score: An Easy Method to Predict Postoperative OutcomePURPOSE: To present a simple model for assessing the risk score of laser in situ keratomileusis (LASIK). METHODS: The LASIK surgery risk score is a number attributed to every LASIK procedure and depends on the presence of individual variables that might add diffi culty and increase the risk of the RESULTS: The score can vary from