After PED, what disease threats are lurking on the global horizon?
Sunday, June 7, 2015
A number of diseases are wreaking havoc on swine populations in different parts of the world, with African swine fever looming as the greatest threat. But, as with PCV2 and PRRS, the next invader may be something completely new
by ERNEST SANFORD
In recent years, the pork industry has been hit by PRRS, PCV2 and now PED. As a result, I am frequently asked what is the next disease likely to strike us.
Well, there is no shortage of disease disasters lurking out there to follow in the footsteps of PED and the aforementioned diseases. Below is a short list of diseases creating havoc in different parts of the world right now. Because of globalization and the rapid pace and immediate connectivity of international travel, any of these diseases can strike us in the near or not too distant future.
African swine fever or ASF is currently spreading unchecked in Russia and the former Soviet Republics, now known as the Commonwealth of Independent States (CSIS). ASF recently started penetrating European Union (EU) countries, such as Latvia, Lithuania, Estonia and Poland.
High Pathogenic PRRS is found in China and Southeast Asia. New Neonatal Porcine Diarrhea (NNPD) is present in Denmark and Sweden. Ebola Virus (Reston Ebolavirus) has made its appearance in the Philippines and West Africa. Nipah Virus (NiV) has emerged in Malaysia, Singapore, Bangladesh and India. Schmallenberg-like viruses have affected countries in the European Union.
Here's a brief history of the diseases on this list and why each of them presents a potential threat to our and possible the global swine industry.
African swine fever. ASF is probably the disease that is most poised to strike anywhere pigs are being raised in the world. ASF has been endemic in sub-Saharan Africa for over 100 years and probably for centuries. The first documented outbreaks outside Africa occurred in Portugal in 1957 and a subsequent outbreak, also in Portugal, occurred in 1960. In the 1980s, there have been outbreaks in France, Belgium and other European countries.
The most recent charge of ASF into Europe started in November 2007 in the Caucasus regions, first in Georgia, then in Russia, with subsequent spread to Armenia, Azerbaijan, Iran and Belarus. The outbreak in Georgia occurred when ASF-contaminated pork landed from a ship from Southeast Africa was fed to local pigs.
In August 2012, an outbreak of ASF was reported in Ukraine. In June 2013, another was reported in Belarus. It didn't take long before countries bordering Belarus and Russia began getting outbreaks, at first in their wild boar populations and then subsequently in their commercial herds.
On Jan. 24, 2014, two wild boars tested positive for ASF in Lithuania, an EU country. Three days later, on Jan. 27, 2014, Russia banned importation of pigs and pig products from all 28 EU countries. The Russian reaction seemed harsh at first, but events soon transpired to support the Russian position. On Feb. 17, 2014, one wild boar tested positive for ASF in Poland. Over the next several months, wild boars and commercial herds became infected with ASF in Latvia, Lithuanian and Poland, threatening the entire EU pig population.
Outbreaks have continued in the Baltic States and Poland. More than 160 have been reported in Latvia, more than 50 in Lithuania and 10 in Estonia. Poland has experienced a steady stream of outbreaks among wild boars and commercial herds.
Because of the mounting threat of ASF, Russia banned and ordered destruction of "backyard" pig production in the Caucasus region. The ban, probably not thoroughly enforced, has failed to stop the spread of ASF in Russia. Wild boars continue to spread ASF unabated across Russia and the CIS countries.
The recent spread of ASF into the Baltic states (Latvia, Lithuania and Estonia) and Poland raises concern for its spread into all neighbouring EU countries. Those at greatest immediate risk of infection are Finland, Hungary and Romania. And, with boars and commercial herds infected in southern Poland, Germany, the largest pork-producing country in Europe, becomes a viable target for ASF.
In addition to Russia, an ever-increasing number of countries have banned importation of fresh pork, semen and live pigs from affected EU countries, as well as Albania, Belarus, Canada, China, Ivory Coast, Japan, Kazakhstan, Kyrgyzstan, Korea, Moldova, Singapore, Switzerland, Taiwan and Ukraine.
The EU response. The response of the EU Commission has been varied and uneven so far. Lithuania applied to the Commission for €3.5 million to build a wall at the border with Belarus. The amount was deemed insufficient and Lithuania reapplied for €13.5 million. The EU Commission finally estimated the cost of a wall at €60 million. Instead of a wall, the Commission allocated €1.56 million to Latvia for disinfections at border crossings with Russia and Belarus. Latvia actually needed €6 million to do the job properly.
Why the concern about ASF in far-off Russia? Russia is the largest country in the world and it's a long, long way from us in Canada. Rosselkhoznadzor, the Russian Veterinary Agency, has identified more than 400 outbreaks of ASF in 10 oblasts (provinces) in Russia. More than 30 billion rubles (more than US$1 billion) has been spent to contain the outbreaks with limited success so far.
Rosselkhoznadzor goes on to state that "ASF in Russia is a threat and concern to the entire global swine industry." As of the end of October 2014, there have been 88 documented cases of ASF in Latvia, Lithuanian, Estonia and Poland, mostly in wild boars, but also in at least nine commercial herds.
The spread is primarily by wild boars, which do not recognize national borders. If ASF continues to spread in the EU, the amount of trade and traffic between EU countries and North America, including Canada, makes the threat of ASF landing on our doorsteps a real and imminent possibility.
ASF in the Americas? Unlike PED, which had never been in the Americas prior to its appearance in the United States in spring of 2013, ASF has visited the Americas in the past. In 1971, outbreaks of ASF occurred in Cuba, followed by Haiti in 1978. The outbreak in Haiti also spilled over into the Dominican Republic.
USAID, in co-operation with the U.S. Department of Agriculture, organized the eradication of ASF from Haiti. They shot 380,000 pigs with compensation supposedly to be paid to the farmers who owned them. It is pertinent to note that 1978 was the height of the movement of the so-called "Haitian boat people," who were coming over to Miami in rickety vessels to escape harsh economic and political repression by "Papa Doc" in Haiti. Any of these tens of thousands of boat people who made it to the shores of Florida could have brought in pork from ASF-diseased pigs and opened the doors for ASF in the United States.
The point is that ASF in North America is not too far-fetched a notion, even though the active infections are geographically far away.
High Pathogenic PRRS Virus (HP-PRRSV). In 2006, a severe epidemic swept through the Chinese pig population, killing more than 100 million pigs and causing an immediate rise in pork imports for the 2008 Olympic Games in Beijing. HP-PRRSV, a highly pathogenic strain of PRRSV, along with several possible secondary diseases, such as PCV2, classical swine fever (hog cholera) and foot-and-mouth disease was identified as the cause of the epidemic.
The disease soon spread to most neighbouring countries in Southeast Asia, including Vietnam, Thailand, Cambodia, Laos, Philippines, Malaysia, Singapore, Myanmar and Bhutan with similar reports of high mortality. Outbreaks have since continued throughout Southeast Asia.
New Neonatal Porcine Diarrhea (NNPD). This disease was first reported in Denmark and France in 2009, causing mortality rates of up to 40 per cent in newborn pigs. All known infectious agents causing neonatal diarrheas, including enterotoxigenic E. coli, Clostridium perfringens types A and C, C. difficile, rotavirus, coronaviruses, Cryptosporidium suis, Strongyloides ransomi, Giardia spp. and Cryptosporidium spp. have been ruled out by investigators. The disease appeared in Sweden in 2010.
Nipah Virus (NiV). First erupting in Malaysia (September 1998 to April 1999) and Singapore (March 1999) where it caused encephalitis and respiratory disease in pigs and people, NiV eventually affected nearly 300 people, killing 105. In addition, more than one million pigs were euthanized to stop the outbreak. The outbreak was located near the Malaysian village of Kampung Sungai Nipah, thus giving rise to the name "Nipah virus."
There have been no additional cases of NiV in either Malaysia or Singapore since the 1998-1999 outbreak. Outbreaks have, however, occurred almost yearly in Bangladesh and India since 2001. More than 200 human cases of NiV have been reported, with 161 deaths in Bangladesh and more than 100 cases and 57 deaths in India starting in 2001.
Ebola Virus (Reston Ebolavirus). Ebola disease has been in the headlines over the last year because of unchecked outbreaks in humans in several West African countries. The Ebola disease in humans is caused by the Zaire strain of the Ebola virus (Zaire ebolavirus), named after the Ebola tributary of the Congo River in the former Belgian Congo colony of Zaire, now the Democratic Republic of the Congo.
Another strain of Ebolavirus, Reston Ebolavirus (RESTV), infects pigs and humans. Humans are asymptomatic carriers of ReBoV, which is deadly to pigs. In 1989, the first outbreak of Reston Ebolavirus occurred in cynomologous macaques (monkeys) used for research in the Hazleton Laboratories in Reston, Va. The macaques had been imported from the Philippines.
In December 2008, pigs on a farm north of Manila tested positive for ReBoV and one month later a worker on the same pig farm tested positive. The worker remained asymptomatic.
Schmallenberg Virus (SV). In November 2011, stillbirths and congenital deformities in newborn calves, lambs, kid goats and cria (baby alpaca) erupted in Schmallenberg, Germany. Similar outbreaks soon followed in the Netherlands, France, Belgium, Luxembourg, Italy, Spain, Switzerland, the United Kingdom, Ireland, Finland, Denmark, Sweden, Austria, Norway, Poland and Estonia.
Midges acted as a vector for the transmission of Schmallenberg virus, fostering widespread distribution of the disease over most of western Europe in a very short period of time during the fall and winter of 2011-2012. Fortunately, the disease proved short-lived and has not recurred since 2012.
As can be seen from this array of potential threats, any number of diseases are waiting and poised to become the next nemesis to our pig population. ASF is by far the most prominently identifiable disease agent that is ready to invade anywhere in the world.
The next invader, however, might not be any of the above. The last two major devastating diseases to hit us, PCV2 (first appeared 10 years ago) and PRRS (first appeared nearly 30 years ago) were brand-new diseases that appeared spontaneously on the scene. So we have to maintain surveillance for all of the above known diseases as well as being prepared to identify a possible, previously unknown disease if one presents itself.
We need to remain vigilant with our biosecurity to keep this and any other potential invaders off our shores. BP
S. Ernest Sanford, DVM, Dip Path, Diplomate ACVP, is a swine veterinary consultant.