End of avian flu season in sight for Japan

Avian influenza control efforts in Japan appear to have been successful so far.

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Following an 18-month battle, efforts to control highly pathogenic avian influenza (HPAI) in poultry have been effective in Japan.

The disease is also reported as resolved in Turkey. Meanwhile, South Korea’s authorities have retrospectively registered two outbreaks in commercial birds that started in April, and three more farms have confirmed recent cases in Nepal. In China, two more infections have been recorded in human patients with prior exposure to backyard poultry.  

Last week, Japan animal health authority officially declared an end to two concurrent HPAI outbreak series affecting the country’s commercial poultry.

First cases of the disease linked to the H5N1 virus serotype were detected in October of 2021, according to a notification to the World Organisation for Animal Health (WOAH).

Since then, more than 17.5 million of the country’s poultry have been directly impacted by further outbreaks.

At 83 different locations, outbreaks linked to this virus family occurred in 25 of Japan’s 47 prefectures, and in all eight of its regions. Well over half of the affected farms had laying hen flocks of up to around 1.4 million birds. Most recent confirmed outbreak was in early April of this year.

As well as the H5N1 virus, the H5N2 HPAI variant was also detected in Japan during the last HPAI “season.”

According to WOAH notifications, it was the first detection of this serotype in a Japanese poultry flock, and it was associated with just one outbreak. This occurred in January of this year, and involved a broiler flock of 55,400 broilers on Kyushu — the island to the south of Honshu.

No further cases of either infection has been reported on Japan’s farms.

However, the risk of further outbreaks cannot be ruled out as the H5N1 outbreak series involving wild birds is still active in Japan.

As recently as late April, three crows tested positive for this virus. According to the latest WOAH report, these birds were found dead in the Tohoku region in northeastern Honshu.   

South Korea’s HPAI toll passes 8.5 million

In the past few days, the nation’s veterinary agency has registered with WOAH two further outbreaks of HPAI linked to the H5N1 virus serotype.

Both date back to mid-April, and involved commercial poultry flocks in the southwestern province of South Jeolla.

Since the current HPAI outbreak series began in November of 2021, there have been 122 confirmed outbreaks on South Korea’s poultry farms. Directly impacted have been more than 8.85 million birds. This total includes around 61,500 dead and 8.78 million culled to prevent further spread of the infection. 

Nepal registers three more outbreaks in poultry

All three of the recently reported avian flu outbreaks in Nepal were in commercial layer flocks around the beginning of this month.

Each of the outbreaks involved between 1,300 and around 5,750 birds — a total of 8,547 poultry.

The H5N1 virus serotype has been linked to 15 outbreaks on Nepal’s poultry farms since January of this year. All affected premises were located in Bagmati Pradesh, and near to the capital, Kathmandu.

In total, more than 38,000 birds have died in these outbreaks, and a further 49,000 have been destroyed. 

Bird flu developments elsewhere in Asia

To WOAH, the veterinary authority of Turkey (Republic of TĂĽrkiye) has declared the HPAI situation in poultry “resolved.”

In late January of this year, the H5N1 virus was detected in the country for the first time since 2015. By the end of the following month, two flocks totaling 4.36 million commercial poultry had tested positive for this virus. Affected premises were in two provinces in the west of the country.  No further cases have been detected in the meantime.

Recently, Indonesia confirmed its first HPAI cases linked to the H5N1 virus serotype. In April, there were more than 4,000 cases among a flock of domestic ducks. They were part of a village flock in South Kalimantan — the southernmost Indonesian province on the island of Borneo.

Around one month ago, a 20% year-on-year drop in egg production in the Philippines was blamed on HPAI outbreaks.

According to a report in PhilStar, the chair of the nation’s chicken meat and egg industry association said 10% of the country’s laying hens died from HPAI.  Current official estimates put the flock size at around 45 million, so the mortality has unbalanced the country’s egg supply. 

Further human cases of avian influenza in China

In the Western Pacific region, two new infections with influenza A virus of avian origin have been confirmed to the World Health Organization [https://www.who.int/] (WHO). Both occurred in China.

Linked to the avian influenza A(H9N2) virus, the first of these latest cases was a seven-month-old boy in the eastern province of Jiangxi.

In early May, his symptoms started. They remained mild, and he has since recovered. Previously, the boy had contact with backyard poultry. No members of his family have become infected.

This brings to 88 the number of lab-confirmed infections with this virus in the Western Pacific region reported to WHO since December of 2015. All but two were in China. Two of the patients died, likely due to pre-existing health conditions.

During the second half of last month, a 54-year-old woman was admitted to hospital in Sichuan province with severe pneumonia. Her infection was confirmed as avian influenza A(H5N6).

The patient’s present condition is not reported. She had prior contact with backyard poultry, and an influenza virus of the H5 family was detected in environmental samples.

Since 2014, 85 infections in the Western Pacific region linked to this virus serotype have been reported to the WHO. Of these, 33 patients have died.  

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