Uh Oh! Scientists show Ebolavirus can be transmitted by air

Kaye Beach

Nov. 16, 2012

Truly frightening!  Look what just rolled across the ProMed newswire;


Canadian scientists have shown that the deadliest form of Ebolavirus
could be transmitted by air between species.

In experiments, they demonstrated that the virus was transmitted from pigs to monkeys without any direct contact between them. The
researchers say they believe that limited airborne transmission might
be contributing to the spread of the disease in some parts of Africa.
They are concerned that pigs might be a natural host for the lethal
infection. Details of the research were published in the journal

Scientific Reports [Hana M Weingartl et al. Transmission of Ebola
virus from pigs to non-human primates.


Scientific Reports 2, Article
number 811, doi:10.1038/srep00811;

According to the World Health Organization (WHO), the infection gets
into humans through close contact with the blood, secretions, organs,
and other bodily fluids from a number of species, including
chimpanzees, gorillas, and forest antelope. The fruit bat has long
been considered the natural reservoir of the infection. But a growing
body of experimental evidence suggests that pigs, both wild and
domestic, could be a hidden source of Zaire Ebolavirus, the most
deadly of the Ebolaviruses. Now, researchers from the Canadian Food
Inspection Agency and the country’s Public Health Agency have shown
that pigs infected with this form of Ebolavirus can pass the disease
on to macaques without any direct contact between the species.

In their experiments, the pigs carrying the virus were housed in pens
with the monkeys in close proximity but separated by a wire barrier.
After 8 days, some of the macaques were showing clinical signs typical
of Ebolavirus [infection] and were euthanised. One possibility is that
the monkeys became infected by inhaling large aerosol droplets
produced from the respiratory tracts of the pigs. Pigs could act as a
host and amplify Ebola-like viruses. One of the scientists involved is
Dr Gary Kobinger from the National Microbiology Laboratory at the
Public Health Agency of Canada. He told BBC News this was the most
likely route of the infection. “What we suspect is happening is large
droplets; they can stay in the air, but not long; they don’t go far,”
he explained. “But they can be absorbed in the airway, and this is how
the infection starts, and this is what we think, because we saw a lot
of evidence in the lungs of the non-human primates that the virus got
in that way.”

The scientists say that their findings could explain why some pig
farmers in the Philippines had antibodies in their system for the
presence of a different version of the infection called Reston
Ebolavirus. The farmers had not been involved in slaughtering the pigs
and had no known contact with contaminated tissues. Dr Kobinger
stresses that the transmission in the air is not similar to influenza
or other infections. He points to the experience of most human
outbreaks in Africa. “The reality is that they are contained, and they
remain local; if it was really an airborne virus like influenza is, it
would spread all over the place, and that’s not happening.”

The authors believe that more work needs to be done to clarify the
role of wild and domestic pigs in spreading the virus. There have been
anecdotal accounts of pigs dying at the start of human outbreaks. Dr
Kobinger believes that if pigs do play a part, it could help contain
the virus. “If they do play a role in human outbreaks, it would be a
very easy point to intervene,” he said. “It would be easier to
vaccinate pigs against Ebolavirus infection than humans.”

Other experts in the field were concerned about the idea that
Ebolavirus was susceptible to being transmitted by air even if the
distance the virus could travel was limited. Dr Larry Zeitlin is the
president of Mapp Biopharmaceuticals. “It’s an impressive study that
not only raises questions about the reservoir of Ebolavirus in the
wild but, more importantly, elevates concerns about Ebola as a public
health threat,” he told BBC News. “The thought of airborne
transmission is pretty frightening.”

[byline: Matt McGrath]

communicated by:
ProMED-mail <promed@promedmail.org>

[The reference for the original publication is: Hana M Weingartl,
Carissa Embury-Hyatt, Charles Nfon, Anders Leung, Greg Smith, Gary
Kobinger. Transmission of Ebola virus from pigs to non-human primates.
Scientific Reports 2, Article number: 811 doi:10.1038/srep00811;
The abstract of the paper reads as follows:

“Ebola viruses (EBOV) cause often fatal hemorrhagic fever in several
species of simian primates including humans. While fruit bats are
considered the natural reservoir, involvement of other species in EBOV
transmission is unclear. In 2009, Reston-EBOV was the 1st EBOV
detected in swine with indicated transmission to humans. In-contact
transmission of Zaire-EBOV (ZEBOV) between pigs was demonstrated
experimentally. Here, we show ZEBOV transmission from pigs to
cynomolgus macaques without direct contact. Interestingly,
transmission between macaques in similar housing conditions was never
observed. Piglets inoculated oro-nasally with ZEBOV were transferred
to the room housing macaques in an open, inaccessible cage system. All
macaques became infected. Infectious virus was detected in oro-nasal
swabs of piglets and in blood, swabs, and tissues of macaques. This is
the 1st report of experimental interspecies virus transmission, with
the macaques also used as a human surrogate. Our finding may influence
prevention and control measures during EBOV outbreaks.”

These experiments are interesting in that they demonstrate the
susceptibility of pigs to Zaire Ebolavirus and that the virus from
infected pigs can be transmitted to macaques under experimental
conditions by an aerosol route. They fall short of establishing that
this is a normal route of transmission of Ebolavirus in the natural
environment. The evidence that pigs play a role in the transmission of
Ebolavirus, other than Reston Ebolavirus, remains circumstantial but
something that should be pursued with urgency. It is curious that
transmission between macaques in similar housing conditions was never
observed. – Mod.CP

Clearly Ebolavirus is very contagious but there is only weak
circumstantial evidence that transmission from pigs occurs via the
porcine breath aerosol. Anyone who has been around pigs knows that
they urinate and not in dribbles. Splashing urine (+ Ebolavirus) could
readily produce a urine mist that could make its way to an immediately
adjoining cage with macaques and in their grooming themselves get
infected. – Mod.MHJ


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