Avian Flu Diary: Netherlands: Multiple Farms Report LPAI H6

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Although LPAI H3 viruses aren't supposed to produce serious illness in poultry - and are not considered `reportable' by the OIE - for several months over the spring and summer we followed an unusual outbreak of H3N1 in Belgium which produced significant losses to their poultry industry (see NL AVINED: LPAI H3N1 Updates).

Today, we are seeing reports of multiple outbreaks of a LPAI H6 virus in turkey farms across the Netherlands, which is also consider a non-reportable virus.

There are two broad categories of avian influenza; LPAI (Low Pathogenic Avian Influenza) and HPAI (Highly Pathogenic Avian Influenza).

LPAI viruses are common in wild birds, cause little illness, and only rarely death. They are not considered to be a serious health to public health (LPAI H7N9 being the exception). The concern is (particularly with H5 & H7 strains) that LPAI viruses have the potential to mutate into HPAI strains.

HPAI viruses are more dangerous, can produce high morbidity and mortality in wild birds and poultry, and can sometimes infect humans with serious result. Again, H5 and H7 viruses are of greatest concern, but other subtypes have also caused human illness and large poultry losses.

Before the middle of the last decade, there was no uniform requirement to report or track LPAI infections. That changed in 2006 when the OIE made reporting of LPAI H5 & H7 viruses mandatory.

While other LPAI subtypes are not currently reportable to the OIE (see Terrestrial Animal Code Article 10.4.1.), that doesn't make them entirely benign.

The most obvious, and worrisome loophole is for LPAI H9N2, which is common in Asia and the Middle East, and has recently moved into Africa. While not a notifiable virus, H9N2 has demonstrated its ability to infect humans and to reassort with other viruses, and is on the CDC's short list of novel viruses with pandemic potential (see CDC IRAT Score).

There are other non-notifiable LPAI viruses we keep a close eye on, including:

LPAI H6N1 which caused a human infection in Taiwan in 2013 - jumped to Taiwanese dogs in 2014, and in 2015's EID Journal: Seropositivity For H6 Influenza Viruses In China, researchers found a a small, but significant number of people in their survey who tested positive for H6 influenza antibodies (indicating previous exposure).
LPAI H4N6 - which while common in wild and migratory birds - has also been found in Chinese, Canadian (1999) and American swine (see Virology: Detection & Characterization Of Avian H4N6 In Midwestern Swine (2015)) and has shown signs of human adaptation (see Cell: Avian-to-Human Receptor-Binding Adaptation by Influenza A Virus Hemagglutinin H4).

Unlike H3N1 earlier this year, the LPAI H6 outbreaks in the Netherlands appear to be benign in poultry, and the risks of it mutating into into a more dangerous HPAI virus are believed negligible.

This (translated) report (Nov 25th) from the Netherlands AVINED.

Low pathogenic bird flu H6 in the Netherlands

It is currently quiet in the area of the highly pathogenic bird flu and in the area of the low pathogenic bird flu H3N1. In Belgium, screening at companies has been positive and no new cases of H3N1 have been detected. However, vigilance for bird flu remains necessary. Several cases of the low pathogenic bird flu of the (not subject to control) type H6 have recently been found in the Netherlands.

Several cases of low pathogenic avian influenza H6 have recently been found in laying farms and turkeys. This is a variant of bird flu that is not subject to control. Most cases were detected via monitoring (serologically positive) and a single case based on clinical symptoms.

These were companies in the provinces of Overijsel, Flevoland, Gelderland, Friesland, Groningen and Noord-Brabant.Be carefulAVINED is happy to point out the importance of strict biosecurity and hygiene at your company. Also be aware of disease symptoms, so that an infection is discovered as early as possible.

If in doubt, contact your veterinarian. And, in consultation with your veterinarian, make use of the possibility to send in Early Warning swabs. In the event of a failure of more than 0.5% during two days, or more than 3% per week per couple, a notification obligation applies to the NVWA (045 - 546 3188).

The lesson of Belgium's H3N1 outbreak earlier this year is that the conventional wisdom on avian flu is subject to change at any time.

LPAI H7 viruses were relatively recently thought to be a weak cousin of HPAI H5N1, and incapable of producing the same level of virulence in humans.

The emergence of LPAI H7N9 in China in 2013 - sporting a mortality rate (among those hospitalized) of 30% - has dispelled that notion. A severe human infection with LPAI H7N4 in China last year showed this was not a fluke.

While the risks to poultry - and to human health - by this outbreak are likely very low, the fact that it has spread widely in the Netherlands is noteworthy.