Introduction
Bird flu, or avian influenza, has had a high profile spot in the news recently. This has prompted several people to query whether migrant birds can be a carrier of this disease to South Africa. Amur Falcons, in particular, come from areas where avian influenza has been recorded.
Below is some information to shed light on the matter, shared to us by two experts in the field, Dr Zephné Bernitz and Dr Alan Kemp. Dr Bernitz has also provided some additional information on research work on Avian Influenza in South Africa.
From Zephné Bernitz:
Avian flu update (14 November 2005)
Avian flu (AI) continues its spread westwards with a new incident reported from Croatia. Several mute swans were reported dead, and in one bird the presence of H5N1 was confirmed. The westward spread of the virus increases fears of the further spread of the disease to Africa. Due to socio-economic conditions in Africa, it is feared that early detection of spread of the virus will not occur. Veterinary capacity is very limited, and contingency plans are not in place. Due to the fact that animals, in this case, poultry, and household members cohabitate, conditions would be ideal for Avian influenza virus to jump to humans. Clusters of infection would not be likely to be detected early, which is crucial in preventing the further adaptation of the virus to rapid passage in humans.
The widespread presence of other viral diseases e.g. Newcastle Disease (NCD), in unvaccinated small scale (back yard) poultry operations in Africa means that mortality from Avian influenza would not easily be detected. Symptoms and mortality patterns from NCD closely resemble AI, and diagnosis on a molecular level is beyond the veterinary capabilities of most African countries. In this respect, South Africa is poised to play a leading role in the continental fight against AI. Surveillance has been under way in Southern Africa since before the current Asian outbreak of AI. A recent outbreak of Avian flu in ostriches in the Eastern Cape was not caused by the same virus (H5N1) as has been implicated in the current Asian epizootic. The culling of all exposed birds and subsequent elimination of the disease focus exemplifies the successful control of the disease by increased levels of bio-security. Recent cases of Newcastle Disease in the Mpumalanga highveld have been carefully monitored to exclude the possibility of Avian Flu. Mortalities in wild birds, especially doves, have also been reported and have been ascribed to NCD and other paramyxoviral infections. Amur falcons that were killed in a freak storm which damaged their roost tree on Christmas day last year were sampled for the presence of H5N1 by Onderstepoort Veterinary Institute, and all tested negative. Sampling of wild birds in South Africa is ongoing, with the main target species being intercontinental migrants such as the migrating kestrels, waders and other water-associated birds.
Medical advice to persons who could possibly come in contact with birds infected with Avian flu (veterinarians, stock inspectors, lab technicians, ringers, rehabilitators) is to be vaccinated with current strains of influenza vaccine as available at your local pharmacy, clinic or medical practitioner. Vaccine against current human strains is unlikely to provide protective immunity against the strain of the present Avian flu, but would be of value in helping prevent genetic swapping of virulence characteristics between the two strains of virus. Said in layman's terms, if you are vaccinated against flu, you are less likely to get the mild human flu currently in circulation. Any person clinically ill with this flu who is exposed to avian virus could develop a mixed infection. The characteristics and genetic make-up of the flu virus is such that if co-infection by different viruses occurs in the same cell, progeny viruses may originate from the reassortment of parental genes. Swapping of genetic components occurs readily, and would be facilitated by people suffering from the flu coming in contact with carrier birds.
Mortality estimates if the H5N1 strain were to adapt to humans are predicted to exceed numbers in any pandemic since the Spanish flu of 1918. Western countries are already stockpiling Tamiflu (oseltamivir phosphate), a new generation antiviral that is at least partly effective against the H5N1 virus. As is the case with any strain of human flu, those especially at risk are the very young, the old, those with pre-existing lung and heart conditions and immuno-compromised people.
Vaccination of rare or endangered and very valuable birds against Avian flu is problematic: vaccination with homologous strains prevents differentiation between natural infection and vaccine reactions which would interfere with control of outbreaks. Vaccination with genetically engineered(recombinant) strains of poxvirus or ILTV that express H5 antigen will not replicate in and therefore also not confer immunity in birds previously exposed to and therefore immune to pox or ILTV. Also, not all species of birds can be expected to mount an immune response against a disease to which they are not normally susceptible eg. turkeys do not respond to ILTV. Vaccination reduces the susceptibility to infection by increasing the infective dose necessary to produce disease, and reduces the amount of virus shed. The mainstay of the control of Avian flu therefore remains early detection of outbreaks in poultry, culling, controlled vaccination of commercial flocks under certain circumstances, increased bio-security, and surveillance to detect the first signs of genetic shift and drift to human populations.
Links: www.fao.org
www.who.int
www.oie.int
From Alan Kemp:
Craig Symes and Adam Welz before him have raised the issue of the
expanding distribution of highly pathogenic avian influenza (HPAI),
strain H5N1, and its implications for bird communities worldwide, after
the authorities in various northern hemisphere countries raised the
spectre of wild, migratory species being responsible for that expansion.
No doubt, the outcome of the European investigations will be closely
followed by our own veterinary and medical health authorities.
The following messages appeared on the ProMED list and website (see http://www.promedmail.org/pls/promed/f?p=2400:1000), which is a good source for information on current emerging diseases:
"Archive Number 20051014.2994
Published Date 14-OCT-2005
Subject PRO/AH/EDR> Avian influenza - Eurasia (06): H5N1
AVIAN INFLUENZA - EURASIA (06): H5N1
************************************
A ProMED-mail post
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ProMED-mail is a program of the
International Society for Infectious Diseases
http://www.isid.org
Sponsored by Elsevier, publisher of The Journal of Hospital Infection http://thelancet.url123.com/a5wh7
[4]
Date: Fri, 14 Oct 2005
From: ProMED-mail promed@promedmail.org
Source: Surfbirds news, 14 Oct 2005 [edited]
http://www.surfbirds.com/sbirdsnews/archives/2005/10/avian_influenza.html
Over the last few weeks, many birdwatchers will have become aware of considerable media interest in the subject of avian influenza or 'bird flu', following outbreaks in central Asia and the Black Sea region of the highly pathogenic type of the H5N1 virus strain which developed within poultry.
Representatives of BTO (British Trust for Ornithology), WWT (Wildfowl and Wetlands Trust), RSPB (Royal Society for the Protection of Birds), and JNCC (The Joint Nature Conservation Committee = UK Government's wildlife adviser) have been involved in discussions with the relevant government agencies, principally to advise on the latest knowledge of the origins of birds wintering in the UK, migration routes and timing, and bird distributions within the UK. Such information is derived in large part from the hard work of volunteers working on schemes such as the BTO Ringing Scheme and the BTO/WWT/RSPB/JNCC Wetland Bird Survey (WeBS). We have also remained in close contact with international colleagues.
The overall assessment is that the chance of this strain of the virus being carried to the UK by a migrating bird is currently low (and perhaps much less than the chance of transmission via illegally imported poultry). In addition, even if the highly pathogenic form of H5N1 avian influenza did make it to the UK, it is important to note that there are no known cases of transmission from wild birds to humans. In South East Asia, the virus has spread (infrequently) to humans as a result of people coming into close contact with infected poultry within the context of the confined proximities of poultry farms. Thus, the risk to human health from wild birds carrying avian influenza would currently appear to be very low.
Nevertheless, it is clearly sensible to keep the situation under review. A number of organisations are working together to deliver a national surveillance programme for wild birds on behalf of Defra; for further details see http://www.defra.gov.uk/animalh/diseases/notifiable/disease/ai/index.htm.
This will include enhanced monitoring for sick or dead birds, coupled with a programme of taking faecal samples from a) apparently healthy live birds, and b) birds shot as part of legal wildfowling activities. As part of this process, we would ask birdwatchers in the field to keep an eye out for any suspicious cases of large-scale mortality or sickness among wild birds.
Waterbirds are potentially among the most vulnerable wild birds. Obviously, all birdwatchers encounter dead birds occasionally, almost all due to perfectly natural causes, so use your common sense. However, if you should come across an incident that seems out of the ordinary, this should be reported via the Defra Helpline on 08459 335577. Calls would then be referred to more local laboratories. Specialists at the labs would then make an assessment on what further action, if any, should be taken.
Although there have been no proven cases of humans catching the disease from wild birds, the virus is spread through nasal secretions and faeces, so please do not touch sick birds or carcasses in the event of a suspicious die-off. Note that separate guidelines have been provided to ringers and these will be made available to anyone else who regularly handles wild birds. In general, however, to guard against a wide variety of illness including avian influenza it is always prudent to exercise basic hygiene (such as washing hands with soap, especially before eating) when coming into close contact with wild animals.
At a time when there is a lot of misinformation circulating on this issue, it is essential to keep matters in perspective and to sift fact from fiction. We reiterate that, to the best of our current knowledge, we consider the chance of wild birds bringing highly pathogenic H5N1 to the UK to be low and the potential for onward transmission from wild birds to people to be very low. Obviously, however, we are continuing to monitor the situation and if there are any further developments we will communicate these widely, in the first instance via organisational websites.
- --
ProMED-mail
promed@promedmail.org
[The advice to birdwatchers provided in the common statement of the 4 British ornithology-related organisations, includes information and instructions which are currently useful for birdwatchers anywhere. They are applicable in the many other countries -- particularly in Europe and the Middle East -- which have recently intensified the surveillance in wild and migrating birds. This has become particularly important in view of the following new OIE press release. - Mod.AS]
******
[5]
Date: Fri, 14 Oct 2005
From: Maria Zampaglione, Communication Department, OIE
m.zampaglione@oie.int
Source: OIE press release, 14 Oct 2005 [edited]
At the request of the Russian authorities the World Organisation for Animal Health sent a team of worldwide renowned experts in avian influenza and ornithology to Siberia in order to assess the avian influenza situation in the region (see OIE press release of 4 Oct 2005].
The complete Mission Report of this scientific mission will
be available online in the Highlights of the OIE website
this afternoon(
One of the main conclusions of the report is that in certain
conditions migratory birds could carry the Asian H5N1
influenza virus to other parts of the world. The migratory
routes of these potentially infected wild birds are mainly
directed to the Caspian Sea, the Middle East, and Africa. A
number of these birds could rest during the migration or
migrate to western Europe.
Facing the current and potential evolution of the Avian
influenza spread, the OIE confirms its position about the
priority of eliminating the virus at the animal source,
emphasizing the importance of the early detection and rapid
response mechanisms carried out by Veterinary Services in
countries at risk.
- --
[The Mission's report (29 pages) has become available in the
meantime; see
http://oie.int/downld/Missions/2005/ReportRussia2005Final2.pdf
The official statement from BirdLife International
For immediate release
20 October 2005
Waterbird culls and wetland drainage could worsen spread of Avian Influenza, BirdLife warns
BirdLIfe International [1] today warned that hasty responses to Avian Influenza based on incomplete or unsound data could do great damage to birds and other biodiversity, while actually raising the risk to people and to the economically important poultry industry. BirdLife International's Partners throughout Europe, such as the RSPB (BirdLife in the UK), are working or preparing to work with their governments to monitor migratory wild bird populations and to provide scientific data and expert guidance.
Recent outbreaks of the highly pathogenic H5N1 strain of avian influenza [2] in Europe have occurred along migratory flyways (including the Danube delta, a great gathering place for migratory waterbird) during the autumn migration. There is no concrete evidence that migratory birds have helped transmit the disease between countries or regions, but the possibility cannot be ruled out.
The spread of H5N1 within and beyond South-east Asia appears attributable to movements of infected poultry [3, 4, 5]. The patterns of spread are not consistent with the timing and direction of movements of wild birds
BirdLife International strongly opposes any suggestion that wild birds should be culled as a way of controlling the spread of the disease, on grounds of practicality and effectiveness, as well as conservation. Any such attempts could spread the virus more widely, as survivors disperse to new places, and healthy birds become stressed and more prone to infection. The World Health Organisation, Food and Agriculture Organisation and OIE (the World Organisation for Animal Health) agree that control of avian influenza in wild birds by culling is not feasible, and should not be attempted.
Similarly, attempts to drain wetlands to keep waterbirds away are also likely to be counterproductive, as well as disastrous for the environment, the conservation of threatened species, and for vital ecosystem services such as flood control and water cleansing. Birds will seek alternative staging places and waterbirds forced to fly further and endure more crowded conditions along their migration route will be more prone to infection. Some Asian and Middle Eastern governments are reported to be already formulating proposals for draining wetlands.
The most efficient control techniques involve improved biosecurity, to reduce the likelihood of contact between poultry and wild birds or infected water sources. Further measures include stricter controls or even bans on movements of domestic poultry, and on wild bird markets. Countries should also ban imports of wild-caught birds from infected areas. Such measures should be introduced worldwide.
BirdLife International therefore welcomes the recommendations by the European Commission that surveillance and biosecurity measures at poultry farms in the European Union should be strengthened, and that the Member States and experts have been advised to increase resources and efforts to monitor migratory bird species.
"We would like to offer our expertise in the Member States through our Partners and invite the EU state administrations to contact our Partners in country for help especially with the wild bird monitoring programmes," said Dr Clairie Papazoglou, BirdLife International's Head of EU Policy,.
BirdLife International's Director of Science, Dr Leon Bennun, stressed the importance of informed and balanced judgement in responses to the threat of avian influenza, and in the public dissemination of information about it. "It is important that discussions of the issues relating to avian influenza should differentiate between the real problems caused by the spread of the disease within bird populations, especially within the poultry industry, and the theoretical risks of a human pandemic."
Contacts
Ade Long, Communications, BirdLife International, tel: +44 1223 277812
email: adrian.long@birdlife.org
Notes
[1] BirdLife International is a partnership of people working together for birds and the environment. It promotes sustainable living as a means of conserving birds and all other forms of biodiversity and is the leading authority on the status of birds and their habitats. Over 10 million people support the BirdLife Partnership of national non-governmental conservation organisations and local networks.
[2] There are at least 144 strains of avian influenza, many of which circulate in wild birds at low levels. Most strains are mild and are designated 'Low Pathogenicity Avian Influenza' (LPAI). But a few 'subtypes' can cause massive mortality in poultry and are designated 'High Pathogenicity Avian Influenza' (HPAI).
Wild birds can also be infected with, and killed by, HPAI viruses. They appear to acquire the virus through contact with infected poultry or with facilities used by them.
Subtype H5N1 evolved in poultry from Low Pathogenicity Avian Influenza viruses that were probably acquired from wild birds. Conditions in poultry flocks (such as crowding, and prolonged contact with faeces, saliva and other bodily secretions) keep the viruses circulating as they evolve
[3] The current series of outbreaks began in 2003 in South-east Asia, where a dramatic increase in intensive poultry production is sometimes combined with poor hygiene and bio-security in small "backyard" enterprises. Domestic ducks are commonly turned out to feed in rice fields alongside waterbirds during the day, and confined with other poultry at night. Birds from different areas are brought together in networks of poultry markets, and often transported hundreds of miles.
[4] Within south-east Asia, movements of poultry and poultry products are known to have been involved in the virus's spread among flocks and between countries. Outbreaks in China, Kazakhstan and southern Russia are connected by major road and rail routes. The "transmission routes" between outbreaks in Asia do not follow migratory flyways. Many of these outbreaks also occurred in summer, when birds are moulting and do not fly far.
[5] There are several ways through which H5N1 might be transmitted, including movements of poultry (and feathers), migrating birds, the trade in wild-caught birds, and the movement of soil/mud on wheels and feet. The relative importance of each of these factors in the transmission of H5N1 is unknown, but to date, all outbreaks that have been investigated have been traced back to poultry movements.
ProMED-mail
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- - Mod.AS]"
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