Taking HPAI To The Bank (Vole)

Bank Vole – Credit Wikipedia

 

# 10,041

 

For more than a decade a debate has raged on as to how HPAI viruses – like H5N1 – manage to get into so many commercial poultry operations, particularly in South Korea and Japan where farm biosecurity is heavily embraced. 

 

One possibility (as yet unproven) has been that small mammals – like dogs, cats, mice, or voles – are somehow vectoring the virus into commercial poultry flocks.

 

We’ve seen evidence that dogs and cats are both susceptible to H5N1, and of H5N8 Antibodies Detected In South Korean Dogs.  Additionally, we’ve seen H5N1 infections among   civets, raccoons, martens, and – of course – humans.  Scientists have experimentally infected cattle, along with ferrets and mice for testing.

 

A couple of years ago, in H7N9 Transmission and Replication In The Guinea Pig Model, and in 2012’s EID Journal: Guinea Pigs As Reservoirs For Influenza, we saw that the common guinea pig is susceptible to a wide variety of human and avian flu strains.

 

But avian viruses are thought to only rarely jump to mammals. 

 

Avian adapted flu viruses bind preferentially to the alpha 2,3 receptor cells found in the gastrointestinal tract of birds, while mammals typically have mostly alpha 2,6 receptor cells in their upper respiratory tract.   Some mammals – like pigs – have both types of receptor cells, and are therefore more likely to be infected by an avian virus.

 

Frankly,  there’s not been a whole lot of research on the ability for HPAI viruses to infect, replicate, and spread via small wild mammals. But we have a study, published today in the journal Veterinary Research, that undertakes just an experiment using bank voles.

 

Why bank voles, you ask?

 

Well, wild bank voles are likely to inhabit the same areas that wild and migratory birds regularly visit, they have a habit of inserting themselves into barns and farm settings looking for food, and they are already a known vector in Europe for the Puumala virus, a milder form of hantavirus (see Hantaviruses: Of Mice And Men).

 

As we learn from this study, bank voles were not only susceptible to two types of avian flu viruses (H5N1 & H7N1), most were able to carry the virus asymptomatically, shed the virus in copious amounts, and were able to pass on the virus to naïve co-housed sentinel voles.

 

I’ve only included some excerpts from a much longer, fascinating study.  Follow the link to read it in its entirety.

 

Susceptibility to and transmission of H5N1 and H7N1 highly pathogenic avian influenza viruses in bank voles (Myodes glareolus)

Aurora Romero Tejeda^1†, Roberta Aiello^1*†, Angela Salomoni¹, Valeria Berton¹, Marta Vascellari² and Giovanni Cattoli¹

Published: 13 May 2015

© 2015 Romero Tejeda et al; licensee BioMed Central.

Abstract

The study of influenza type A (IA) infections in wild mammals populations is a critical gap in our knowledge of how IA viruses evolve in novel hosts that could be in close contact with avian reservoir species and other wild animals. The aim of this study was to evaluate the susceptibility to infection, the nasal shedding and the transmissibility of the H7N1 and H5N1 highly pathogenic avian influenza (HPAI) viruses in the bank vole (Myodes glareolus), a wild rodent common throughout Europe and Asia.

Two out of 24 H5N1-infected voles displayed evident respiratory distress, while H7N1-infected voles remained asymptomatic. Viable virus was isolated from nasal washes collected from animals infected with both HPAI viruses, and extra-pulmonary infection was confirmed in both experimental groups. Histopathological lesions were evident in the respiratory tract of infected animals, although immunohistochemistry positivity was only detected in lungs and trachea of two H7N1-infected voles. Both HPAI viruses were transmitted by direct contact, and seroconversion was confirmed in 50% and 12.5% of the asymptomatic sentinels in the H7N1 and H5N1 groups, respectively.

Interestingly, viable virus was isolated from lungs and nasal washes collected from contact sentinels of both groups. The present study demonstrated that two non-rodent adapted HPAI viruses caused asymptomatic infection in bank voles, which shed high amounts of the viruses and were able to infect contact voles. Further investigations are needed to determine whether bank voles could be involved as silent hosts in the transmission of HPAI viruses to other mammals and domestic poultry.

<SNIP>

Discussion

The aim of this study was to investigate the susceptibility of the bank vole to infection with two HPAI strains, the H5N1 A/turkey/Turkey/1/2005 (Tk/H5N1) and the H7N1 A/ostrich/Italy/2332/2000 (Os/H7N1) isolates, and to establish whether those avian viruses are transmitted by infected animals to naïve co-housed sentinel voles.

<SNIP>

The present study demonstrated that the bank vole is susceptible to infection with highly pathogenic H5N1 and H7N1 viruses of avian origin without prior adaptation, shedding viable virus in the environment, and transmitting the virus to contact voles. Interestingly, infection with the same HPAI strains demonstrated high pathogenicity and 100% of mortality in BALB/c mice [38], while infected voles were more resistant to the clinical condition and displayed zero or very low mortality rate.

These important findings may suggest that wild rodents could play a role as silent hosts in IA virus epidemiology, contributing to the spread of HPAI virus infections during an outbreak. If this occurs under natural conditions, the circulation of IA viruses in these rodents may provide opportunities for the acquisition of mammalian adaptive mutations, which could minimize the barriers to interspecies transmission of these viruses. However, the study of synanthropic wild mammals, and in particular wild rodents, is a critical and important gap in our knowledge of how IA viruses may evolve in new hosts [22], considering that these species share the same ecological habitats as waterfowl and live commensally around domestic poultry farms [32], thus running the risk of being exposed to IA viruses.

(Continue . . .)

China’s MOA Disputes Poultry As Source Of H7N9 Infections

Credit FAO

 

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While Chinese poultry – particularly poultry sold in live markets – are atop the suspect list for spreading the H7N9 virus, there remain many unanswered questions regarding where this virus resides, and how it is jumping to humans.  Prime among them, despite having the finger of suspicion directed at them, remarkably few birds have actually tested positive for the virus.

 

While only a few dozen H7N9 positive birds were detected last year out of tens of thousands tested, we saw an immediate and dramatic drop in the number of human cases once live bird markets were closed (see The Lancet: Poultry Market Closure Effect On H7N9 Transmission), making for a pretty compelling circumstantial case for live poultry being the prime vector.

As does the oft quoted (but hard to verify) statistic that 70% of human cases reported recent direct contact with live poultry.

 

The FAO, in their most recent update (see FAO Calls For Increased Regional Vigilance & Preparedness Over H7N9), stops short of making a definitive statement on the source of infection, but states:

 

There is strong evidence that people become infected following close contact with infected live poultry, mostly in live bird markets or when slaughtering birds at home.

 

As does the World Health Organization, in their most recent H7N9 Risk Assessment:

 

Source of human infection

Although much remains unknown about this virus, such as (1) the animal reservoir(s) in which it is circulating, (2) the main exposures and routes of transmission to humans, and (3) the distribution and prevalence of this virus among people and animals, human infection appears to be associated with exposure to live poultry or contaminated environments, including markets where live poultry are sold. This is based on the following:

• Most human cases report a history of exposure to birds or live poultry markets.

• The viruses isolated from humans are avian influenza viruses and genetically similar to those isolated from birds and the environment.

• Targeted testing of poultry and environment in live poultry markets that are epidemiologically linked with human cases of H7N9 infection has revealed more positive results than testing in areas not linked with human cases

 

While none of this equates to a `smoking chicken’, warnings regarding visiting live poultry markets have been prominently featured by Hong Kong’s CHP, Mainland China’s CDC, along with our own CDC, and the World Health Organization.

 

Unlike other dangerous avian flu viruses we’ve seen in the past, H7N9 doesn’t make poultry ill, making it very difficult to detect, control, or eradicate.  An avian virus that sickens and even kills people, carried stealthily by chickens or ducks, is the very definition of a nightmare scenario for the poultry industry.

 

But for China, where food insecurity remains high and poultry provides much of their diet’s protein – this scenario could prove economically, politically, and socially disastrous.

 

China, which produces more poultry than anyplace else on earth, reportedly raises over 15 Billion birds each year. Poultry - whether factory-farm produced or from backyard flocks - is a major source of income, and food, for hundreds of millions of people.

 

Anything that seriously threatens China’s poultry industry also raises the specter of mass hunger in the world’s most populous nation.  And with that comes political instability, and unpredictable outcomes.  Something which we looked at last April in Food Insecurity, Economics, And The Control Of H7N9.

 

While China’s CDC is primarily concerned with preserving the the health of the nation, their Minister of Agriculture (MOA) is concerned with feeding more than 1 billion people. With very different responsibilities and goals, and the price of failure high, I suppose we shouldn’t be too surprised to see conflicting messages regarding the H7N9 virus.

 

Today, on the eve of China’s biggest holiday celebration, their MOA has  publicly disputed the connection between live poultry and the infection of humans by the H7N9 virus.   This from CCTV.

 

No proof of direct poultry-to-human transmissions

China's Ministry of Agriculture says there is so far no proof of any direct transmission of the H7N9 bird flu from poultry to humans. The ministry said on Wednesday that it had collected over 1.6 million poultry and environment samples in 2013, of which only 88 samples had tested positive for the H7N9 virus.

 

So far in 2014, the ministry has taken another 33,000 samples, eight of which were found to be positive. All of the positive samples came from live poultry markets.

 

"So far we haven’t found any positive samples from live poultry farms. And we haven’t found any evidence to prove that poultry can pass the H7N9 virus directly to humans." Zhang Zhongqiu, bureau director of Ministry of Agriculture, said.

 

 

Admittedly, the paucity of positive tests out of more than a million samples introduces a degree of uncertainty regarding the transmission of this virus, and the possibility of there being more than one vector species can’t be ignored.

 

But until another vector can be identified, exposure to live market birds remains the most likely risk factor for contracting the virus.

 

Of course, should this virus ever acquire the ability to spread efficiently between humans, that point will quickly become moot.

Barnstorming Avian Flu Viruses?

Photo Credit – FAO

 

# 6782

 

 

My thanks to Helen Branswell this morning for tweeting the link to a new study that suggests that avian influenza viruses can be spread over considerable distance by the wind.  

Long time readers will recall we’ve visited this question a couple of times before. We’ll review those, but first, the new study which looked at the extensive outbreak of H7N7 in the Netherlands in 2003.

 

From the Journal of Infectious Diseases (the full study is behind a pay wall), we get a fair idea of their findings via the Abstract.

 

Genetic data provide evidence for wind-mediated transmission of highly pathogenic avian influenza

Rolf J.F. Ypma1, Marcel Jonges, Arnaud Bataille, Arjan Stegeman3, Guus Koch4, Michiel van Boven1, Marion Koopmans1,W. Marijn van Ballegooijen1 and Jacco Wallinga

Outbreaks of highly pathogenic avian influenza in poultry can cause severe economic damage, and represent a public health threat. Development of efficient containment measures requires an understanding of how these influenza viruses are transmitted from one farm to the next. However, the actual mechanisms of inter-farm transmission are largely unknown.

 

Dispersal of infectious material by wind has been suggested, but never demonstrated, as a possible cause of transmission between farms. Here we provide statistical evidence that the direction of spread of avian influenza A(H7N7) is correlated with the direction of wind at date of infection.

 

We find the direction of spread by reconstructing the transmission tree for a large outbreak in the Netherlands in 2003, using detailed genetic and epidemiological data. We conservatively estimate the contribution of a possible wind-mediated mechanism to the total amount of spread during this outbreak to be around 18%.

 

Although it occurred nearly 10 years ago, this outbreak of H7N7 continues to interest scientists, as it represents the largest cluster of human infection by H7 flu virus we’ve seen. 

 

This report from the December 2005 issue of the Eurosurveillance Journal.

 

Human-to-human transmission of avian influenza A/H7N7, The Netherlands, 2003

M Du Ry van Beest Holle, A Meijer, M Koopmans³ CM de Jager, EEHM van de Kamp, B Wilbrink, MAE. Conyn-van Spaendonck, A Bosman

An outbreak of highly pathogenic avian influenza A virus subtype H7N7 began in poultry farms in the Netherlands in 2003. Virus infection was detected by RT-PCR in 86 poultry workers and three household contacts of PCR-positive poultry workers, mainly associated with conjunctivitis.

 

More than 30 million birds residing on more than 1,000 farms were culled to control the outbreak.

 

One person - a veterinarian who visited an infected farm – died a week later of respiratory failure. The rest of the symptomatic cases were relatively mild.

 

Normally, when avian flu manages to spread among local farms, we think of transport mechanisms like the farm-to-farm movement of infected birds or eggs, or of contaminated or infected personnel or equipment, or even a bird or small mammal vector.

 

The idea that the virus might be blown (likely carried on dust, or some other particulate) – while unproven -  has come up before.

 

Back in January of 2008 I wrote a blog called The Virus My Friend, Is Blowin' In The Wind where I cast a dubious eye upon claims by the Indian Government that the bird flu virus (H5N1) was being blown by the wind across the border from neighboring Bangladesh, and was infecting hapless Indian Poultry.

 

It wasn’t impossible, of course.  And I went into some of the other types of pathogens (mostly fungi and bacteria) that are known to travel in the wind.

 

Then in May of 2010 (see Viruses Blowin’ In The Wind?) we saw a report in the journal Environmental Health Perspectives, that suggested that it was possible for H5N1 (or any Influenza A virus) to be transported across long distances in the air.

 

Although researchers demonstrated influenza RNA could be detected in ambient air samplings, they didn’t establish that the virus remained viable over long distances.

 

But we have seen studies indicating that the H5N1 virus can – under the right environmental conditions – remain viable for hours or even days in the environment (see EID Journal: Persistence Of H5N1 In Soil and H5N1: Hiding In Plain Sight)

 

Lending at least a little credence to the idea that they might survive on the wind long enough to infect downwind farms.

 

It has also been suggested that dried chicken droppings (`poultry dust’) may also serve to spread the virus, and Indonesian authorities have mentioned this as a possible vector (see Indonesian Updates And Vector Concerns).

 

Hong Kong authorities also mentioned the possibility (of at least short-range windborne transmission) in a highly detailed epidemiological report issued by the University of Hong Kong, on the outbreak of H5N1 on a solitary chicken farm in the New Territories in 2008.

 

Epidemiology Report of the Highly Pathogenic Avian Influenza H5N1 Outbreak in December 2008 in a Chicken Farm in Ha Tsuen, New Territories

 

Excerpt

(ii) The strong winds and gust from the north and north-east from 4 to 6 December 2008 could have deposited potentially contaminated dust and leaves from the trees into the nearby shed no. 17 via its north opening. These contaminated materials could then have gathered at the corner of the shed where the initial high mortality in poultry occurred.

 

 

So . . . while none of this is a slam dunk proving wind-borne transmission of viable avian (or any other flu) viruses, we have at least some credible evidence that suggests it may have happened.

 

How big of a factor this plays in the spread of viruses remains to be seen.

 

But it does provide investigators another avenue of epidemiological query when multiple farms in close proximity are infected with avian influenza.

 

 

Note: `Barnstorming’ is an Americanism that some of my readers may not be familiar with.  It refers to the early days of aviation when pilots would fly to rural areas, land in farmer’s fields, and sell rides, or put on an air show for the locals.

Indonesian Updates And Vector Concerns

 

 

 

# 4978

 

 

Although the recent Sulawesi bird flu outbreak – according to officials – is `under control’, we continue to see an elevated number of local media stories on bird flu outbreaks (in poultry) there, and in other regions of Indonesia.

 

Thus far, none of the suspected human cases of H5N1 infections reported over the past couple of weeks have tested positive for the virus.

 

Nearly all of them appear to have been released from the hospital.

 

A few reports this morning from a variety of sources, including some local concerns on how the virus is spreading. 

 

First stop is BFIC where Ida has a report on 2010 Bird flu cases in Purwokerto, central Java - which is located quite far afield from the recent outbreaks in Sulawesi and Balikpapan.

 

 

Banyumas, Central Java ::: Bird flu outbreak in birds

Posted by Ida on October 13, 2010

Purwokerto – Participatory Disease Surveillance and Response (PDSR) of Livestock and Fishery Service (Dinnakan) in Banyumas, reported total 845 birds in Kabupaten (municipal) Banyumas had died of bird flu H5N1 virus. In details, the virus had hit 445 native chickens, 300 broiler (meat) chickens and 100 quails. This record was done from January to beginning of October 2010.

 

Prevalence was low during February to September, but then started to rise at the beginning of October.

 

Control measures are done by disinfection spraying to infected cages and housing free-ranged chickens.

 

People dumped dead chickens to the river which has caused bird flu spreading on area along the stream.

(Continue . . . )

 

Dutchy on FluTrackers had a similar report yesterday called 845 Tail of Poultry Bird Flu, which also mentioned the dumping of birds in the river, from a different source.

 

The practice of dumping the carcasses of dead chickens into local rivers and ponds is apparently fairly common, as we’ve heard similar reports in the past (see here, here, and here)

 

During early 2009 (see The Winter Of Our Disbelief), a number of dead H5N1-infected chickens washed up on the shores of Hong Kong, which led many to believe that large numbers of chickens were being disposed of somewhere up the Pearl River in Guangdong province.

 

Next stop is at the always busy Arkanoid Legent, with a report from Balikpapan- which has been the scene of numerous poultry deaths over the past couple of weeks (see Indonesia: Balikpapan Teenager Negative For H5N1)- that suggests the number of reports coming is slowing down.

 

Indonesia : Bird Flu slowed

Via Metro Balikpapan :

" BALIKPAPAN : The spread of H5N1 virus that causes bird flu in Aberdeen today are berangsug gradually decreased. Bird flu has caused the death of hundreds of chickens infected with H5N1 or whether destroyed en masse after the determination of the status of bird flu alert Balikpapan.

(Continue . . . )

 

 

 

Another report getting a lot of play overnight is this one, which I found on the Flu Wiki posted by bgw in MT, relayed by dbg.

 

Below is a machine translation of the original article which appears in the Tribun Kaltim.   I’ll return with some more on the possible role of flies in spreading the virus.

 

 

The Fly Could Spread Bird Flu

Tuesday, October 12 2010 | 18:41 WITA

Reporter the East Kalimantan Stand, Niko Ruru

Tarakan, tribunkaltim.co.id - Section Head of Public Health Service and Food Crop Tarakan, Drh Wikan Addi Cahya said, the fly could become the spreading media of bird flu to humankind.

 

Moreover, this virus could spread if we were touching with the fellow humankind that just touched the poultry that infected bird flu.

 

"So not small the possibility of this bird flu circulated while in the territory that infected bird flu, then with dust, the vehicle and birds also could make us infected bird flu," he said.

 

To anticipate the widening of the plague of this bird flu, Wikan made a plea to all the breeders and the owner of the poultry to immediately wash his hands after touching the poultry. This was meant so that bird flu not spread to humankind.

 

"Washed him could with disinfectant, with detergent or bath soap also including disinfectant. Because this bird flu also spread to humankind through dust that was brought by air, then better this breeder cage the poultry," he said.

 

Although this report appears to be more of a generic warning, one that is designed to get those with poultry to adopt and maintain disinfection and hygiene procedures, the notion that flies might have a role in spreading the virus has come up before.

 

In 2004, in Japan, researchers found evidence of the virus in two species of blow flies. They wrote:

 

Detection and isolation of highly pathogenic H5N1 avian influenza A viruses from blow flies collected in the vicinity of an infected poultry farm in Kyoto, Japan, 2004.

The H5 influenza A virus genes were detected from the intestinal organs, crop, and gut of the two blow fly species, Calliphora nigribarbis and Aldrichina grahami, by reverse transcription-polymerase chain reaction for the matrix protein (M) and hemagglutinin (HA) genes.

The HA gene encoding multiple basic amino acids at the HA cleavage site indicated that this virus is a highly pathogenic strain. . . . . Our results suggest it is possible that blow flies could become a mechanical transmitter of H5N1 influenza virus.

 

 

In January of 2007 we saw a report in the Jakarta Post about a veterinary pathologist from Gajah Mada University and his claims that flies could carry the H5N1 virus (see Cats and Dogs and Flies, Oh My!).

 

Scientist warns of bird flu in flies

Sri Wahyuni, The Jakarta Post, Yogyakarta

A scientist has warned the government not to place too much of the blame for bird flu on poultry as it could result in the public being unaware of the fact that other animals can also carry the virus.

 

Veterinary pathologist Wasito of Gajah Mada University's veterinary medicine told The Jakarta Post at his office in Yogykarta on Tuesday that other animals, such as cats, dogs and even files, could also carry the virus.

 

"A study we are conducting here, for example, has convincingly found that it is possible for flies to spread the bird flu virus," he said.

 

Unanswered at the time was the question of whether flies might spread the virus by becoming infected themselves, or simply by physically transporting infected matter (dust, feces, etc) on the surface of their bodies.

 

And in Houseflies Revisited I brought you the story of researchers at North Carolina State University who reported that houseflies can carry both the Avian Influenza and Newcastle viruses.

 

As reported by World Poultry Net in 2007.

According to the researchers, “more than one-third of the adult Musca domestica sampled contained AI virus particles”.

 

Led by Wes Dawson and James Guy, the researchers said adult flies carried an infectious dose in their gut for more than three hours after feeding. “This might be important for spread of the virus when fly populations are high and in contact with highly virulent strains,” they explained.

 

Although flies are still mentioned from time to time as possible vectors, I’ve seen very little in the way of new research on the matter over the past couple of years.

 

While it appears possible (or perhaps even likely) that flies could spread the AI virus, how good they are at doing it – and under what conditions it might happen – hasn’t been determined.

 

At least, not yet.  But I’ve no doubt that scientists are researching the matter.

 

Currently outbreaks of H5N1 occur primarily in birds, although sporadic,widely scattered human cases are reported as well.

 

Most (but not all) have been linked to close contact with infected poultry or birds. The source of infection in a small number of human cases isn’t known.

 

While the virus has yet to adapt well enough to human hosts to transmit effectively between people, scientists still remain concerned that the virus could mutate into a pandemic strain someday.