Department of Statistical Sciences
University of Cape Town
| Avian Demography Unit
Department of Statistical Sciences University of Cape Town |
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| What is Avian Influenza? |
Avian Influenza and wild birds |
Avian Influenza and poultry |
Avian Influenza and bird-ringers/birders |
Avian Influenza and the ADU |
What can you do? |
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Avian influenza (AI), or “bird flu”, is a contagious disease of animals caused by viruses that normally infect only birds and, less commonly, pigs. AI viruses are highly species-specific, but have, on rare occasions, crossed the species barrier to infect humans. In domestic poultry, infection with AI viruses causes two main forms of disease, distinguished by low and high extremes of virulence. The so-called “low pathogenic” form commonly causes only mild symptoms (e.g. ruffled feathers, a drop in egg production) and may easily go undetected. The “highly pathogenic” form is far more dramatic. It spreads very rapidly through poultry flocks, causes disease, affecting multiple internal organs and has a mortality that can approach 100%, often within 48 hours. Which viruses cause highly pathogenic disease? Influenza A viruses have 16 H subtypes and 9 N subtypes. Only viruses of the H5 and H7 subtypes are known to cause the highly pathogenic form of the disease. However, not all viruses of the H5 and H7 subtypes are highly pathogenic and not all will cause severe disease in poultry. On present understanding, H5 and H7 viruses are introduced to poultry flocks in their low pathogenic form. When allowed to circulate in poultry populations, the viruses can mutate, usually within a few months, into the highly pathogenic form. This is why the presence of an H5 or H7 virus in poultry is always cause for concern, even when the initial signs of infection are mild. For many questions and an update of the current global situation consult the World Health Organisation. What is a pandemic? If the AI virus infects a human (which has happened), and if humans can transmit it to other humans (which is not the case, but this might happen in the future), then a pandemic could occur. This is what's causing the panic at the moment. This panic is fuelled by hypes, misinformation and people who are trying to make money out of it (such as online pharmacies). The best remedy….obtain your information from reliable sources such as scientific journals (e.g. nature and science), reliable international organisations (e.g. FAO, WHO, OIE, UN-organisations) and reliable state departments (such as the National Institute of Communicable Diseases and the National Department of Agriculture) and not from newspaper opinion articles. Back to top |
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The most recent outbreaks suggest that migratory birds may have played a role in transmitting the disease between countries or regions, but in the majority of cases the movements of domestic poultry or poultry products, have been largely implicated in the spread of the disease in SE Asia.
There have been no recorded instances of transmission of the disease between infected wild birds and humans. The H5N1 virus strain is not currently contagious between humans and most human cases to date have been associated with close contact with infected domestic poultry. The risk of a human contracting the disease from a wild bird is remote, unless there was excessive close contact with infected birds and their excreta. Culls of wild birds are highly unlikely to stop the spread of the disease and are extremely difficult to implement. Culls have the potential to make the situation worse by dispersing infected individuals and stressing healthy birds, making them more prone to disease. Moreover, it would divert resources away from important disease control measures. For more information regarding the avian flu and wild birds consult the website of Birdlife International and the United Nation Convention on the Conservation of Migratory Species (CMS). Click here to see a trip report from an AI surveillance trip to Lake Chilwa, Malawi in February 2006. Back to top |
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In the case of an increased risk of infection (which up to now is not the case since there are no confirmed cases in South Africa). The most efficient control techniques involve improved biosecurity, primarily within the poultry industry, to reduce the likelihood of contact between domestic stock and wild birds or infected water sources. This needs to be coupled with swift and complete culls of infected poultry flocks in the event of an outbreak. Further measures that should be considered include stricter controls on wild bird markets, and movements of domestic poultry. Such measures should be introduced worldwide. Countries currently free of the disease (such as South Africa) should consider a ban on imports of all wild birds for the pet trade and of domestic poultry from affected regions. Preventing public access to infected sites is also clearly a sensible precaution. For the most up to date information on avian flu and livestock consult the website of the Food and Agricultural Organisation (FAO) of the United Nations. For more information on AI and livestock refer to the link below of the Department of Environment, Health and Rural Affairs (UK). Additional information can also be obtained form the World Organisation for Animal Health (OIE) and the National Department of Agriculture. Back to top |
Bird-ringers must be aware that at the moment there is only a small risk. Recent evidence reveals that seemingly healthy wild birds may carry the Highly Pathogenic H5N1 and may transmit the disease.There is a recent outbreak in Nigeria, so for those catching inter-african migratory waterbirds or are active in west afica we recommend to take precautionary measures. It might be wise to increase basic hygiene standards, some of which include:
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The recently formed Avian Flu scientific taskforce of the UN Commission on the Conservation of Migratory Species called for action along five lines:
The international community should recognize that for African countries, including South Africa, combatting the theoretical threat of a worldwide flu-pandemic, has far less priority than combatting the harsh reality of the current HIV epidemic, which has cost approximately 1.2 million lives in South Africa. Thus, projects such as the monitoring of AI in wild birds and further identification of exact migration routes of waterbirds will have to rely on funding form the international community. Despite the current lack of funding we are currently working on:
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What should you do if you suspect AI? First of all, birds do not live forever, and sooner or later each individual dies. If you think that you observe unusual numbers of dead (wild) waterbirds, contact a local ornithologist. Most probably you have just observed a natural event. The chance is very, very small that the birds in fact have died from AI. If you do not know where to reach a local ornithologist please contact the ADU (Tel. 021-6502423 or email adu@adu.uct.ac.za). If you observe unusually high numbers of dead poultry, please inform/call the owner/farmer as soon as possible; they generally know how to proceed further. Do NOT enter the property or touch the dead birds. The risk that these birds were killed by AI are very small, and such mortality could well be due to another disease (see below). Ornithologists and waterbird counters should keep an eye on unusual high levels of starvation among waterbirds, particularly when conducting waterbird surveys. There is a very small chance that the starvation is due to AI and could well be attributed to outbreaks of botulism, blue-green algae or avian cholera, or something else. However, these cases should be reported to the owner or relevant management authority who will get in touch with the state vet. Back to top |
