Monday, June 09, 2014

SECD: Another Emerging Coronavirus Threat

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Photo Credit CDC EID Journal

 

# 8722

 

A little over a year ago a new and deadly (to swine, at least) coronavirus made its first appearance in North America, and since then has swept across 30 states, killing more than 7 million pigs.  We looked at this emerging threat last October in mBio: PEDV - Porcine Epidemic Diarrhea Virus - An Emerging Coronavirus.

 


While distantly related to SARS and MERS (both are betacoronaviruses),  PEDV is an alphacoronavirus. We’ve seen no evidence of human infection due to PEDV coronavirus, so PEDV is not currently considered a zoonotic disease.

 

Two other genera also exist; Gammacoronaviruses & Deltacoronaviruses.  The first two (alpha & beta) are believed to originate in bats (but are found in many other species), with the second two (Gamma & Delta) are believed to have an avian origin.


In February of this year, the Ohio Department of Agriculture officially announced that a never-before-seen porcine deltacoronavirus (PDCoV) had been identified in the United States (see New, non-PED Coronavirus detected in pigs with diarrhea). From the announcement:

 

Sequence analysis of the new coronavirus shows that it is a deltacoronavirus, distinct from PED and TGE viruses.  The new virus has been designated as Swine DeltaCoronavirus (SDCV). This virus is closely related to a coronavirus which was detected in Hong Kong in 2012. The virus cannot spread to humans or other species and poses no risk to food safety. Further study is needed to confirm whether or not this virus is the cause of diarrheal disease in affected pigs.  

 

With a plethora of porcine pathogens to deal with , the USDA has lumped them together in the general category of SECD – or Swine Enteric Coronavirus Diseases.   After talking about doing so since last April, last week the USDA announced the mandatory reporting of SECDs by all farmers, veterinarians, and diagnostic labs. 

 

Swine Enteric Coronavirus Diseases (SECD), including Porcine Epidemic Diarrhea virus (PEDv)

Last Modified: Jun 5, 2014  

Since its appearance in the United States in April 2013, porcine epidemic diarrhea virus (PEDv) has spread within the swine industry.  In recent months, an additional related virus, porcine delta coronavirus (PDCoV), has appeared in this country.  Infections with these novel swine enteric coronavirus diseases (SECD) can cause significant morbidity and mortality, particularly in young piglets.

What is USDA doing about SECD?


In response to the significant impact swine enteric coronavirus diseases (SECD), including Porcine Epidemic Diarrhea virus (PEDv) and Porcine deltacoronavirus (PDCoV), are having on the U.S. pork industry, USDA issued a Federal Order on June 5, 2014.  USDA, States, herd veterinarians and producers will collaborate to manage the diseases in a manner that supports business continuity for commercial pork producers and maintains a plentiful supply of pork for consumers.

There are two basic requirements of the Federal Order.  First, producers, veterinarians, and diagnostic laboratories are now required to report all cases of new SECD, including PEDv and PDCoV, to USDA or State animal health officials.  Second, operations reporting these viruses must work with a veterinarian – either their herd veterinarian, or USDA or State animal health officials – to develop and implement a reasonable management plan to address the detected virus and prevent its spread.

To learn more about USDA’s SECD program, read our Q&A.

 

The pork industry is understandably sensitive to any negative publicity after the drubbing they took from the 2009 H1N1 pandemic, and is (rightfully) quick to point out that these viruses do not affect humans


What is left unsaid is that viruses – particularly RNA viruses like coronaviruses – tend to evolve over time. And what can be said about a particular virus today may not always hold true tomorrow. 

 

A topic well addressed by Dr. Linda J. Saif in her recent presentation CORONAVIRUSES: Lessons for. SARS and MERS Human Coronaviruses.

image 

 

Until it mutated, and gained the ability to jump species, the SARS coronavirus remained hidden and unnoticed in a bat reservoir.   And we have serological evidence going back at least 20 years that a MERS-like coronavirus has existed –apparently fairly benignly - in Middle Eastern dromedaries for at least two decades before becoming a `human’ problem. 

 

As the following slide from Dr. Saif’s presentation illustrates, while some coronaviruses are have a narrow host range, others have shown a propensity to expand their horizons. 

 

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None of this means that these emerging SECDs will ever pose a direct threat to human health, but it is hard to completely discount the possibility. 

 

A notion discussed today in an article in the Perdue Exponent Online - which starts off as an interesting overview of recent MERS Vaccine research at the University - but ends with a discussion of the potential of seeing new zoonotic coronaviruses evolve.

 

Coronavirus masking mechanism disabled by Purdue team

Posted: Monday, June 9, 2014 10:00 am

BY REED SELLERS Summer Reporter

Purdue researchers have taken a giant leap toward a vaccine for a lethal and under-recognized category of diseases that are killing humans and thousands of pigs.

Andrew Mesecar, Purdue’s Walther Professor of Cancer Structural Biology and professor of biological sciences and chemistry, recently published his findings on the masking function of coronaviruses including the Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS). According to Mesecar, there are currently no cures or vaccines for coronaviruses.

<SNIP>

This breakthrough is game-changing for researchers in the field of coronaviruses, but there is still no vaccine. The largest concern is the mutation of other coronaviruses from other species to humans.

SARS is believed to have mutated from infecting bats to cats to humans and MERS is believed to have mutated from infecting bats to camels to humans.

”The prediction with the SARS virus is that it took two amino acid mutations — two nucleotide mutations to make it infectious,” Mesecar said.

Two nucleotide mutations is a very low number of mutations and is concerning. A recent coronavirus is affecting the pig population in Indiana having killed around 600,000 pigs last fall and more during the winter. Mesecar said it is possible that the virus could mutate as MERS or SARS did which would pose another threat to health in the U.S.

 


More evidence  that human health and animal health are inexorably linked, and further validates the importance of promoting the `One Health Concept’, where human, animal, and environmental health are all interconnected. We know that most of the infectious diseases that afflict mankind began in other species:

 

Measles probably evolved from canine distemper and/or the Rinderpest virus of cattle. Tuberculosis, which now infects 1/3rd of humanity, likely jumped from domesticated goats and cattle, and influenza’s all seem to have an origin in waterfowl. The list is long, and still growing.

 

History continues to show that we ignore animal diseases – even those without an apparent affinity for infecting humans – at our own peril.  Otherwise, we are apt to get blindsided again, by a pathogen we should have seen coming.

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