«The Economic and Social Aspects of Biodiversity Benefits and Costs of Biodiversity in Ireland REPORT PREPARED BY: CRAIG BULLOCK, OPTIMIZE CONSULTANTS ...»
In Ireland, HIV has infected 4,251 people (to 2006), resulting in 895 AIDS cases and over 400 deaths, since 1994 (NDSC, 2006).This is relatively low in European terms. However, the rate of spread has increased in recent years and now stands at over 300 cases reported or diagnosed per year sine 2001. Globally, the World Bank has estimated that the economic impact of HIV Aids has reached over $1.6 Billion ( 1.2 billion). No information is available on the economic costs of HIV management and control in Ireland. However, in the UK, the costs are estimated at £16,000 ( 23,000) per patient per year. The UK government has estimated that every infection of HIV prevented saves between £500,000 and £1 million ( 735,000- 1,470,000) in direct and indirect costs. Other recurring and unavoidable costs include public education and awareness programmes, vaccine and other medical research, screening of transfusion products and transplant organs, etc.
9.5.3 A v i an I n fl u e n z a The influenza viruses are a group of pathogens of man, animals and a wide variety of avian species.
Avian influenza may be transmitted from one species to another, either directly from birds to people or other species, or through an intermediate host, such as pigs or cats (Lamb & Krug, 1996).
This creates a genetic 'melting pot' in which viruses can swap their genes and acquire each other's properties, thus generating new viruses that would pose a further threat to human health.
The recent spread of highly pathogenic H5N1 avian influenza through Asia into Africa and Europe has involved at least 53 countries (including 23 in Europe), and resulted in huge impacts on the poultry industry across at least 12 countries (WHO 2007). Hundreds of millions of domestic fowl have died or been killed during the outbreak.The total economic losses is estimated at in excess of US$10 billion, with other unquantified economic and psychological impacts on farm workers and people in associated industries whose livelihoods have been affected. The World Bank has predicted that the continuing spread of the virus could significantly affect global economic growth. At present (May 2007), the H5N1 virus does not have the capability of spread from person to person.
However, the genetic material of the virus could evolve gradually into more virulent strains or, alternatively, could combine its genetic material with that from other influenza viruses that already infect humans (referred to as “genetic reassortment”). The more frequently humans come in contact with infected birds; the more likely this is to happen.
It has long been recognised that wild birds can introduce low pathogenic influenza virus (LPAI) into domestic poultry. Depending on the nature of the poultry population and the animal husbandry techniques used, strains of LPAI have the potential to become highly pathogenic (HPAI) within poultry flocks, resulting in severe outbreaks and mortality amongst farm birds (Lamb & Krug, 1996).
On occasion, these massive outbreaks can spill-over into wild bird populations or to other animals.
For example, the H5N1 HPAI virus has infected domestic and wild cats, pigs and horses, as well as humans. In Sweden and Germany, mink and pine marten respectively have been infected with HPAI after feeding on infected birds (ECDC/Eurosurveillance, 2006). Until recently, it was considered that wild birds could not act as a source for long range transmission of HPAI strains due to their lethality – commonly referred to as the “dead birds don’t fly” premise.Trade in poultry and wild animals and international travel were therefore considered to be the most likely risk factors.
However, analysis of the recent international spread of the H5N1 virus has led to a change in this model of HPAI epidemiology (EC, 2006). The large spill-over of H5N1 into wild bird populations, together with the persistence of infection within local areas (suggesting the emergence of local wild reservoirs for the virus), the rapid spread of the disease along bird migration routes, and the apparent absence of coinciding trade outbreaks, indicates that at least some wild bird species are capable of carrying and spreading the disease across long distances to domestic flocks.
While it is considered that all bird species are capable of being infected with H5N1, the species considered most likely to be implicated in long-range spread are migratory species of waterfowl, including geese, swans and ducks. The international wild bird trade is also recognised as a major risk factor for the global spread of H5N1, as evidenced by the first case in the UK in 2005, which occurred in an infected Suriname parrot which died in a quarantine station. The wild bird trade and transboundary movements of poultry flocks are now strictly monitored and subject to intensive infection control and quarantine procedures, though illegal trade activities worldwide still represent a high degree of risk. Migratory movements of wild birds cannot, however, be controlled.
For Ireland, where we are currently HPAI-free, the most likely potential entry route of the H5N1 virus is through wild bird migration. Compared to most other EU countries, Ireland is a relatively small country with disproportionately high numbers of wintering waterbirds (EC, 2006). H5N1 has spread to parts of Southeast Asia, the Urals, Kazakhstan and Siberia from where some waterbird species migrate to EU countries. From here, the continent-wide dispersal of the virus through migration and vagrant bird movements would be possible. An assessment of migratory waterbirds conducted for the European Commission in 2006 identified the main risk species and their migration routes. Of the 17 highest risk species identified, 13 occur in Ireland, with large numbers of many of these species coexisting in wetland areas upon their arrival after migration.
Once the link between wild bird migrations and the spread of H5N1 was made, there were calls worldwide from agricultural communities, and from some government agencies, for the mass culling of wild birds and draining of wetlands in which they congregate, in order to prevent the spread of the disease and to protect poultry flocks and livelihoods. However, any such impact on wild bird populations may actually increase the risk of global spread, as well as increasing the risk of a more virulent strain of the virus evolving (BirdLife 2007, FAO 2007).
Maintaining genetic biodiversity within wild bird populations is likely to be an important factor in the limitation of spread of avian influenza viruses. Genetic diversity provides the basis for resistance to environmental stresses and diseases within any given animal or plant population. As the culling of wild birds would reduce genetic diversity, this could conceivably impact on the development of resistance to HPAI strains and actually facilitate the development of more virulent forms of the virus. Furthermore, it is known that disturbance of habitats such as wetlands can affect migration routes and patterns, potentially leading to the spread of the virus into areas not normally at risk, or the possibility of reassortment through mixing of species or flocks that would not otherwise naturally come into contact (Karesh 2005, Corvalan et al. 2005, Kapan 2006). The World Health Organisation (WHO) and Food and Agricultural Organisation (FAO) of the United Nations, and the International Organisation on Animal Health (OIE) have urged national governments to prohibit the culling of wild birds for precisely this reason.
Protection of wider biodiversity and ecosystem health may play an important role in preventing the spread of HPAI by maintaining the resilience of non-avian animals to the disease. Other environmental stresses (including pollution, habitat disturbance, or impacts on food species), which impact on the biodiversity and ecosystems that support wildfowl populations, can affect wildfowl behaviour and the distribution and movement of bird populations. Therefore, the protection of biodiversity in the wider natural environment, including wetland areas and associated habitats, is considered an important aspect of regulating and limiting the spread of H5N1 (Rapport 2006).
Av i a n I n fluenza monitoring in Ire l a n d
The last recorded outbreak of HPAI in Ireland was in 1983, when a H5N8 HPAI strain infected two commercial turkey flocks, one commercial duck flock and one broiler flock. In the subsequent period to 2006, LPAI outbreaks (associated with several distinct strains) occurred in eleven years. Surveys in wild birds only commenced in Ireland in 2003 as part of an annual EU-wide survey, so the possible links between domestic and wild flock outbreaks in previous years is unknown. Although LPAI has been isolated from wild birds in Ireland in each year from 2003 to 2006, there have been no concurrent outbreaks in domestic flocks. The absence of AI in Irish domestic flocks since 1998 may be attributable to improved animal husbandry practices in line with revised EU and WHO guidance and standards. However, as shown by the current global spread of H5N1, the risks of spread via migratory birds are significant, and there are many factors at play including travel, trade, agricultural practices and environmental conditions. A number of rare bird species in Ireland including corncrake, lapwing, godwits, snipe and curlew, could be threatened by an outbreak of H5N1 HPAI in this country. It is therefore imperative that a holistic and trans-disciplinary approach to preventing novel HPAI outbreaks is taken, and that the health, agricultural, and environmental sectors collaborate to devise a strategy that recognises the importance of protecting ecosystem integrity and wildlife health.
sources: NDSC, FAO, CBD and WHO.
9.5.4 B ov i n e Tu b e rc u lo s i s ( T B ) As an example of an economically significant disease associated with wildlife, bovine TB is of particular relevance and importance to Ireland. The role of wild badgers in the spread of TB to cattle has been researched extensively. It has long been acknowledged that badgers probably do spread the bacterium to cattle when they feed or commute through pasture. About 20-25% of badgers in Ireland may be infected with TB, and it is suspected that between 10% and 20% of outbreaks in cattle are due to cross-infection from badgers (Hayden 2000). Wild deer have also been identified as a potential source of cross-infection, with other species such as foxes and stoats, potentially playing a role in the spread of the disease.
In the UK, following publication of the Krebs report on bovine TB, a major programme of culling and localised eradication of badger populations was implemented. The trial was abruptly called off after only two years when it became clear that the incidence of TB in cattle actually rose.
Subsequent studies clearly indicated that in at least some areas, the greater incidence arose from the displacement of ‘carrier’ animals from setts and the redistribution of badgers through the countryside. Furthermore, research has shown that, at least in certain regions, the route of TB has been from farm animals to badgers, contrary to what was previously thought.This was demonstrated during the foot and mouth epidemic in 2001, when the nationwide suspension of cattle TB controls actually led to an increased incidence of TB in badgers. It is possible that the development and intensification of cattle farming across the countryside has created the conditions under which bovine TB became endemic within the badger population, facilitating further spread of the disease to cattle. (Woodroffe et al, 2006) Although the status of the badger as a common animal in Ireland is not under any immediate threat, the UK experience suggests that there is a very real risk that localised disturbance of badger territory, fragmentation of habitats, and the resulting displacement of local badger populations (all of which can result from human activity), could result in an increase in the occurrence of TB in cattle.
There has been extensive research into badger biology and TB in Ireland, but no assessment has been carried out to date on how the current rate or future patterns of landscape change in Ireland might impact on the health of livestock or wider ecosystems. Such research is urgently required, and long overdue as the pace of infrastructure development increases.
9.5.5 Other diseases A number of other disease organisms which occur in Ireland have been associated with outbreaks in other countries that have been exacerbated by human impacts on biodiversity, some with significant economic and public health implications.
For example, there is also some evidence, albeit largely anecdotal, that changes in fox populations and their distribution may be leading to the emergence of the parasitic disease toxoplasmosis amongst domestic animals and people. In many countries in the EU and worldwide, the spread of toxoplasmosis has been related to changes in mammal populations that have occurred as a result of urbanisation. It is important that similar situations are avoided in Ireland through a more holistic approach to both nature conservation and health protection.