Curious Cook: Bird flu may be forever


Wild birds tend to transmit the avian influenza. — ENGIN AKYURT/Pexels

Spring has finally arrived here in France, and this time, it came with some unwanted surprises. The war in Ukraine has led to shops limiting the purchases of pasta, flour, and cooking oils due to the lack of exports from Ukraine. To make matters worse, France is currently suffering from the worst avian flu crisis in its history, which is causing the prices of poultry to rise to previously unimaginable levels.

An estimated 15 million high-quality farm birds have already been culled in France due to HPAI (Highly Pathogenic Avian Influenza), and the irony is the poultry most likely to be destroyed are those that are free to roam outdoors, as HPAI is transmitted by the many wild birds that criss-cross the country, usually as migratory flocks.

A kilo of prime duck breast filet now costs over 25 EUR (RM115), with probably more price rises on the way, and I found this out the hard way, buying some duck for a family dinner last week. This is an increase of over 30% from what I would normally expect to pay. In the UK, one cannot even buy free range eggs as all the hens are kept inside barns to prevent them from catching HPAI.

According to the columnist, the price of duck breasts have gone up by 30%. — SEBASTIAN COMPAN PHOTOGRAPHY/UnsplashAccording to the columnist, the price of duck breasts have gone up by 30%. — SEBASTIAN COMPAN PHOTOGRAPHY/Unsplash

France is particularly hard hit because poultry farms here tend to produce the highest quality eggs and birds for eating. Many farms rear their birds on open grazing lands, with a large proportion also fed on organic feeds, and generally they are also harvested later than birds in the UK or USA (where the average lifespan of a chicken is around 40-42 days).

In France, there are more varieties of chickens, and they are generally kept 48-50 days or longer, with some quality chickens kept over 80 days in free range conditions, which would just be uneconomical in other countries.

But the provision of high-quality poultry in open air or free range or organic conditions has come at a huge ecological cost. Of the 2,109 HPAI events at poultry farms notified in continental Europe at the beginning of May 2022, 1,297 such events occurred in France, some 61.5% of the total cases.

The next most affected country was Italy, with 317 events. Germany had only 72 farm-reported events, but had detected 1,193 cases in wild birds, mostly migratory species. However, this may be just a reflection of the amount of testing done on wild birds by the Germans.

Worry?

Should we be worried? To some extent, ‘Yes’, but not excessively, at least for the current moment. And I am not referring to the price of poultry in the shops.

There are several strains of bird flu that cause HPAI, all from a family of viruses scientifically distinguished by the types of 2 proteins called Hemagglutinin and Neuraminidase found on the surface of the virus. Hence, H5N1 means Hemagglutinin type 5 and Neuraminidase type 1.

The 4 major HPAIs of concern to birds are H5N1, H7N9, H5N6 and H5N8. To some degree, some of these strains of bird flu are also of grave concern to humans.

These viruses are extremely persistent in the environment and especially in wild birds. More concerning may be evidence that some of these avian viruses have already adapted to mammals such as red foxes, otters, polecats, ferrets, and lynxes and this has happened very quickly, just over the last few years. Mostly, these mammals caught the virus from eating infected birds.

In the UK, hens are kept in barns to prevent them from catching avian flu. — ARTEM BELIAIKIN/PexelsIn the UK, hens are kept in barns to prevent them from catching avian flu. — ARTEM BELIAIKIN/Pexels

Also 17 cases of HPAI infections in humans, from the strain H5N6, have been reported from China since 2019, plus one minor H5N1 human infection in the UK. Another 15 human infections from a related virus, H9N2, have also been reported from China and Cambodia since 2019.

However, recent incidences of avian flu which is deadly to humans are relatively small. In 2013, a variant of bird flu called novel H7N9 caused 36 deaths in China out of an infected pool of 130 people (a mortality rate of over 27%). There is no confirmation that human-to-human transmission of novel H7N9 was possible, and this strain was found in chickens, ducks, and pigeons, curiously without causing any visible symptoms in the birds.

The theory of how novel H7N9 evolved to become a killer human pathogen is also particularly interesting and a sobering example of how viruses can evolve to cross species barriers. A detailed study of the genetic history of H7N9 suggested it is a triple reassorted virus, probably assembled with genes from both the H7N3 duck virus from Zhejiang and the H9N2 finch (brambling) virus from Beijing, combined into the original H7N9 virus found in Korean wild birds.

How this reassorted novel H7N9 virus adapted itself to infect humans is unclear, but some points in its genetic code implied a shift which allowed the virus to bind to human cell receptors, and an increased ability for replication in humans.

At least modern technology means that a genetic trail of novel H7N9 may be available and importantly can also be monitored for future variations. Prior to that, there was another even more lethal variant of bird flu which affected humans. It was H5N1, and it caused the deaths of over 53% of the people infected during an outbreak which began in 1997. This outbreak is still persisting in small pockets around the world ever since.

The main hotspot in the beginning was Hong Kong, and the mean age of the people affected then was 19.8 years, compared to 60.9 years for H7N9. Both viruses appeared to have been transmitted to humans via infected poultry, though the evolution trail for H5N1 appears to be not as well analysed as for H7N9.

In 2003, a major outbreak of H5N1 surfaced in Egypt, which replaced Hong Kong as the H5N1 hotspot for humans. Over 346 people were infected and 116 of them died from the virus in Egypt, resulting in a mortality rate of over 33.5%. To date, there are no vaccines, drugs, or treatments available to effectively prevent H5N1, or indeed any HPAI viruses, and the only remedy is the complete culling of all infected or potentially infected birds.

A 2016 Egyptian study into H5N1 found that inoculation of poultry with various inactivated H5N1 and H5N2 viruses as vaccines caused the virus to display higher mutation rates, which promoted new variants able to escape the vaccines, thereby greatly reducing the efficacy of the vaccines.

Avian flu events

Many people tend to think of bird flu as a disease which affects mainly farm poultry, probably because they mostly read news about the mass culling of poultry flocks. However, the reality is that HPAI is killing countless numbers of wild birds too, to the extent that some species are endangered. And the number of avian flu outbreaks is now seemingly increasing every year. The UK is having its biggest ever outbreak of bird flu in 2022, at the same time as France, Germany, and several other European countries. It is unclear what measures may be adopted to reduce this trend.

Now can I worry?

In terms of catching bird flu, the risk to people not actively handling infected poultry is currently minimal. Almost everyone who has been ill or died from bird flu was in contact with infected birds and there is no evidence humans can spread bird flu. This situation may change, of course, and various health bodies around the world are carefully monitoring all incidents of human illnesses related to bird flu, just in case.

According to the columnist, the risk of catching bird flu is currently minimal for people who don’t work closely with infected poultry. — ZOE SCHAEFFER/UnsplashAccording to the columnist, the risk of catching bird flu is currently minimal for people who don’t work closely with infected poultry. — ZOE SCHAEFFER/Unsplash

HPAI is certainly a worry for poultry farmers and wildlife conservationists. Within a very short space of time, HPAI has changed from a seasonal threat during the migratory periods to a permanent threat in many countries. In short, it appears that HPAI is now killing farm and wild birds regardless of the seasons.

How this situation developed may well be linked to climate change. Due to changes in global climate, it has been observed that birds are starting their migrations at different times than usual. As a result, migration paths are criss-crossing the paths of other birds previously unencountered in pre-global warming times. The chances therefore of catching HPAI are likely to be significantly increased, and the disease is then carried into distant areas where other birds can be infected.

Although the risk to humans is currently low, one should still avoid contact with any sick domestic or wild bird, especially one with a swollen head, or a lack of coordination, or breathing difficulties, or drooping wings/dragging feet, or body tremors, etc.

The views expressed here are entirely the writer’s own.

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Curious Cook , Chris Chan , bird flu , chickens

   

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