Avian Flu Diary: Vietnam Reporting H5N1 Poultry Vaccine `Failures’

Photo Credit – FAO

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We’ve a pair of (likely related) reports this morning regarding the spread of the the 2.3.2.1C clade of H5N1 and the recent illness in previously vaccinated ducks in Southern Vietnam’s Tra Vinh Province.

The first report, from Thanh Nien News, reports on H5N1 infection among vaccinated ducks in Tra Vinh province, which they somewhat vaguely report as due to a `possible mutation’ of the H5N1 virus.

Vietnam reports bird flu virus mutation

Friday, March 07, 2014 12:10

Vaccine-resistant mutation of H5N1 bird flu virus strain has been confirmed in the Mekong Delta province of Tra Vinh while vaccinated fowls fell sick in central Vietnam.

Ngo Duc Thanh, director of Tra Vinh animal health department, said the kinds of vaccine that have been used for many years showed weaker effects this year.

Thanh said most samples from sick poultry would be tested for a new mutation.

(Continue . . . )

A somewhat more specific report comes this morning from Xinhua News, which states that the 2.3.2.1C clade of the H5N1 virus – previously seen in Northern and Central Vietnam and known to evade older vaccines - has moved further south in Vietnam, and has been detected in nearby Dong Nai province.

The `mutation’ mentioned in the Tra Vinh report may well turn out to be this already-known, but continually expanding variant of the H5N1 virus. Testing will tell us if it is that, or (less likely, but still possible) a new variant of the virus. It is also possible that this flock was not properly vaccinated to begin with.

H5N1 spreads to Vietnam's southern province

English.news.cn 2014-03-07 13:45:59

HO CHI MINH CITY, March 7 (Xinhua) -- The H5N1 strain of avian influenza virus, clade 2.3.2.1C, which has been prevalent in Vietnam's northern regions, was discovered for the first time in a number of dead ducks in southern Dong Nai province, about 1,120 km from capital Hanoi, local media reported Friday.

State-run Vietnam News Agency quoted an official from Dong Nai province's Animal Health Department as reporting that results were confirmed after a sample from the birds tested positive for the virus.

Previously, the A/H5N1 strain, clade 1.1, were found in affected poultry sold at many markets across Vietnam, with the availability rate up to 6 percent in 2013.

From late 2013 and particularly in the first two months of 2014, the A/H5N1 strain, clade 2.3.2.1.C, has penetrated into southern regions, along with clade 1.1. To date, eight out of 13 city and provinces in southern Mekong delta were reported to be struck with avian flu outbreaks.

Dong Nai province is home to the largest number of poultry raised nationwide, with over 12 million. It is also located at the gateway of Ho Chi Minh City, the key economic hub in the south. As such, the transportation of poultry products is more likely to trigger the outbreak of bird flu, according to the local animal health department.

Currently, only 10 percent of the poultry in Dong Nai has been vaccinated against the A/H5N1 strain of the virus. Earlier, the province detected two bird flu cases in Trang Bom and Cam My districts.

The latest statistics from the National Steering Committee on Bird Flu Prevention and Control revealed that the H5N1 virus hit 23 provinces and cities across Vietnam, with over 80,000 infected poultry culled. Two Vietnamese died from the virus so far this year, one in southern Binh Phuoc and the other in Dong Thap provinces.

While most countries have adopted a strict `quarantine and stamp out (cull)’ policy when it comes to avian flu, China, Indonesia, Vietnam & Egypt have – for a variety of economic and social reasons – embraced poultry vaccines as a major part of their control strategy.

The challenge is that the H5N1 virus is continually evolving, and over time new strains emerge that can (either partially, or totally) evade the vaccines in current use.

In 2012, in Egypt: A Paltry Poultry Vaccine, we looked at a study conducted by the Virology department at St. Jude Children’s Research Hospital appearing in the journal Poultry Science, that gauged the effectiveness of six commercially available H5 poultry vaccines currently deployed in Egypt.

Of the 6 vaccines tested, only one (based on a locally acquired H5N1 seed virus) actually appeared to offer protection.

Poultry vaccines that provide only partial protection can mask infections, but may not prevent the spread (and possible mutation) of a virus. A situation that experts, like Professor C.A. Nidom, of the Institute of Tropical Disease, Airlangga University have warned about in the past (see Indonesia: Debate Over Poultry Vaccination).

The World Health Organization's Western Pacific Office (WPRO) has a detailed fact sheet on Vietnam’s H5N1 challenges (below), from which I’ve pulled a few excerpts.

H5N1 in Viet Nam

(EXCERPTS)

Viet Nam is considered to be endemically infected with H5N1, with disease outbreaks being detected in a number of provinces across the country in 2012. In the south of Viet Nam the clade 1 virus persists since 2004 indicating that there is an endemic disease cycle with that particular clade and with no persisting introductions from other areas or countries.

In contrast, in northern and central Viet Nam the previous clade 2.3.4 virus was replaced from 2009 by clade 2.3.2.1 suggesting that additional incursions of new viruses were still occurring. Viruses belonging to the 2.3.2.1 “clade” have been detected in many countries in Asia, Middle East and Eastern Europe.

This pattern of incursion and establishment of new clades or variants has continued. In 2011, a new variant of H5N1 within clade 2.3.2.1 was detected and this virus caused immediate concern as the available poultry vaccines gave poor protection against it. A similar event has occurred in 2012 with another variant appearing. As of September 2012 at least three different H5N1 viruses variants were causing disease in poultry.

The Government of Viet Nam has, through the H5N1 control programme, detected these new virus strains as a result of disease outbreaks being reported and subsequent virus monitoring in the laboratory. This detailed knowledge of the viruses present is a very important outcome of the monitoring programme.

Department of Animal Health-led trials, supported by FAO, continually test vaccine efficacy against emerging strains of virus. In September 2012 a vaccine trial was underway to test a newly available H5N1 vaccine against the second 2.3.2.1 variant found two months previously. Information is on hand from earlier work about vaccine effectiveness against previously recognized viruses.

The different clades of the H5N1 viruses continue to be present in Viet Nam for two main reasons –trade in poultry with neighbouring countries and virus circulation in older ducks, commonly layers, which can become infected and not show clinical disease. Also, wild birds are known to carry influenza viruses, but H5N1 viruses of the 2.3.2.1 clade have not been detected to date in wild birds in Viet Nam.

Essentially, as long as these novel viruses are able to survive in the wild, or in domesticated poultry flocks - they continue to evolve – pitting our vaccine technology, surveillance methods, and biosecurity protocols against their evolutionary prowess and growing diversity.

A viral `arms race’, that shows no signs of abating, and that has recently been joined by H7N9, H5N8, and a short-but-growing list of other worrisome novel flu viruses.

For more on the evolution of the H5N1 virus, you may wish to revisit these earlier blogs.