Ebola Virus - Credit CDC
Although it doesn’t appear to present any kind of serious human health risk, a big story this morning is the announcement of the discovery of Ebola Reston among laboratory monkeys being kept at an unnamed research laboratory in the Philippines.
Ebola Reston is one of five known Ebola virus species, and the only one found to be endemic outside of Africa.
Unlike its African cousins, Ebola Reston – while capable of infecting humans – is not known to produce illness or death in man. It can, however, produce serious illness in non-human primates, and can infect pigs (generally asymptomatically).
Ebola Reston was first discovered in crab-eating macaques, imported from the Philippines, at a research laboratory in Reston, Virginia (USA) (hence the name) in 1989. This discovery was recounted somewhat sensationally in the book, The Hot Zone, by Richard Preston.
First, what we know about this latest discovery (which isn’t much), then I’ll return with some more background on this fascinating virus.
Saturday, September 05, 2015
MANILA — Several monkeys at a research and breeding facility in the Philippines have been infected with an Ebola virus strain that is non-lethal to humans, health officials said Saturday.
The facility's 25 workers have been tested for possible infection but all have been found negative for the Ebola Reston variety, said Health Secretary Janette Garin.
She said the virus was detected last week after the monkeys were observed to be suffering from measles, which could have lowered their resistance to Ebola.
Excerpts from Today’s MOH Press Conference – Credit Rappler.
As mentioned above, details are scant. The MOH did not disclose the name or location of the lab, how long these laboratory animals had been in captivity, how they might have been exposed to the virus, or whether or not animals had been recently shipped to or from this laboratory.
The risks to human health are believed low with Ebola Reston, although there is relatively limited experience dealing with this virus.
In the October 2014 CDC Review of Human-to-Human Transmission of Ebola Virus described the 1989 Reston laboratory outbreak and subsequent infection of personnel.
Similarly, an outbreak of Reston virus (Reston ebolavirus species, which does not cause EVD in humans) infection occurred in a quarantine facility housing non-human primates in separate cages and the transmission route could not be confirmed for all infected primates. Multiple animal handlers developed antibody responses to Reston virus suggesting asymptomatic infection was occurring in humans with direct animal contact and implicating animal handling practices in transmission between primates
Among workers in contact with monkeys or pigs infected with Reston ebolavirus, several infections have been documented in people who were clinically asymptomatic. Thus, RESTV appears less capable of causing disease in humans than other Ebola species.
However, the only available evidence available comes from healthy adult males. It would be premature to extrapolate the health effects of the virus to all population groups, such as immuno-compromised persons, persons with underlying medical conditions, pregnant women and children. More studies of RESTV are needed before definitive conclusions can be drawn about the pathogenicity and virulence of this virus in humans.
While Ebolaviruses are known to infect a wide variety of mammals (humans, primates, pigs, etc.) they are believed to originate from a bat host. Earlier this summer Dr. Ian Mackay looked at the latest research into this connection in Evidence that Reston ebolavirus resides in live bats in the Philippines...
In late 2008 Ebola Reston made another high profile appearance when it was reported for the first time in pigs, again from the Philippines. This from the FAO.
FAO/OIE/WHO offer assistance to the Philippines
Manila/Roma, 23 December 2008 - Following the detection of the Ebola-Reston virus in pigs in the Philippines, FAO, the World Organization for Animal Health (OIE) and the World Health Organization (WHO) announced today that the government of the Philippines has requested the three agencies send an expert mission to work with human and animal health experts in the Philippines to further investigate the situation.
An increase in pig mortality on swine farms in the provinces of Nueva Ecija and Bulacan in 2007 and 2008 prompted the Government of the Philippines to initiate laboratory investigations. Samples taken from ill pigs in May, June and September 2008 were sent to international reference laboratories which confirmed in late October that the pigs were infected with a highly virulent strain of Porcine reproductive and respiratory syndrome (PRRS) as well as the Ebola-Reston virus.
Roughly a month later, we learned that several farm workers in contact with infected pigs tested positive for antibodies to the Ebola-Reston virus. None displayed any signs of illness.
3 February 2009 - On 23 January 2009, the Government of the Philippines announced that a person thought to have come in contact with sick pigs had tested positive for Ebola Reston Virus (ERV) antibodies (IgG). On 30 January 2009 the Government announced that a further four individuals had been found positive for ERV antibodies: two farm workers in Bulacan and one farm worker in Pangasinan - the two farms currently under quarantine in northern Luzon because of ERV infection was found in pigs - and one butcher from a slaughterhouse in Pangasinan. The person announced on 23 January to have tested positive for ERV antibodies is reported to be a backyard pig farmer from Valenzuela City - a neighbourhood within Metro Manila.
In 2011 researchers showed that pigs were also highly susceptible to Ebola-Zaire, which can be up to 90% fatal in humans (see Replication, Pathogenicity, Shedding, and Transmission of Zaire ebolavirus in Pigs). Exactly how pigs fit into the ecology of Ebola – either in Africa or the Philippines – is uncertain.
Hopefully we’ll get more information on this latest lab outbreak in the days and weeks ahead, and that it leads to a better understanding of the risks (or lack, thereof) of infection from this virus.