VILNIUS, Lithuania––The European Food Safety Authority on March 17, 2014 reported that a Lithuanian government plan to fight African swine fever by killing wild boars has little or no chance of success.
“No evidence was found in scientific literature proving that wild boar populations can be drastically reduced by hunting or trapping in Europe,” the European Food Safety Authority said, citing “the adaptive behaviour of wild boar, compensatory growth of the population, and the possible influx of wild boar from adjacent areas. Thus,” the report emphasisized, “drastic hunting is not a tool to reduce the risk for introduction and spread of African swine fever virus in wild boar populations.”
Lithuanian interior minister Daylis Alfonsas Barakauskas on January 27, 2014 announced a strategy to combat the discovery of African swine fever in two wild boars by trying to kill 90% of the Lithuania wild boar population––about 54,000 wild boars––before June.
Barakauskas’ response was the most aggressive yet to outbreaks of African swine fever that have plagued eastern Europe since spreading from Georgia to Russia in November 2007. Caused by a virus, African swine fever is believed to have been spread both by wild boars and by commerce in live domestic pigs and pork.
No vaccine available yet
African swine fever does not affect humans, but often kills pigs. But culling to try to stop the spread of African swine fever often kills pigs in even greater numbers. Since no vaccine exists yet to either prevent or treat African swine fever, killing animals who may have been exposed to it remains the only recognized prophylactic measure against it.
As many as half a million domestic pigs have been culled since 2007 in response to more than 600 outbreaks of African swine fever in Russia, Ukraine, Belarus, Lithuania, and Poland, with little hint so far of containing it. As of January 2013 there had been 193 known outbreaks in wild boars and more than 350 on farms within the Russian Federation alone. About 20.5 million domestic pigs in Russia, 17 million in Poland, and several million in each of the other affected nations are believed to be potentially at risk.
The two infected wild boars were found in Alytus county, Lithuania, three months after hunters in November 2013 reported finding as many as 40 dead boars in more than half a dozen wooded areas, with external symptoms resembling those of African swine fever. Lithuania agricultural officials initially denied that the boars could have been African swine fever victims.
Boar-proof fence proposal knocked down
As well as proposing to kill wild boars in unprecedented numbers, Barakauskas applied for European Commission funding to build a boar-proof fence along the Lithuanian border with Belarus. This was a downsized version of a notion floated in August 2013 by Maris Balodis, director general of the Latvian Food & Veterinary Service. Balodis proposed building a boar-proof fence along all of the borders of Poland, Lithuania, Latvia, Estonia, Russia and Belarus.
Meeting in Brussels on February 6, 2014, the European Commission Standing Committee on the Food Chain & Animal Health responded that the fencing scheme appears “questionable from a cost/benefits perspective.”
The committee did not offer an opinion on the viability of the wild boar extermination plan at that time, but Program for Monitoring Emerging Diseases participants did, after unidentified Lithuanian “state veterinary officials” alleged to media that culling wild boars is necessary because “Come spring, the virus will spread faster as warm weather brings back birds and the mites they bear.”
Responded Mary-Louise Penrith of the Department of Veterinary Tropical Diseases at the University of Pretoria in South Africa, “The advent in spring of ‘birds and their mites’ is certainly not going to spread the African swine fever virus. A large selection of arthropods have been investigated as potential vectors of the ASF virus. Argasid ticks of the genus Ornithodoros are competent biological vectors of the virus and need not necessarily have evolved with it. Pig mites proved unable to maintain or transmit the virus. Control efforts will certainly not be assisted by the circulation of urban legends about how the virus spreads,” whereas “a strong focus on the biosecurity of pig farms will go a very long way.”
Offered David Thomson, general manager of operations at the National Agricultural Quarantine Inspection Authority in Papua New Guinea, “Reduction or removal of susceptible feral or wild animal populations for disease control purposes is never, ever, as simple as it appears on paper.”
Thomson warned of the risk that trying to cull wild boars might “foster spread of disease as animals respond to the pressures via movement.”
There is no documented instance of any agency anywhere ever succeeding in even temporarily eradicating 90% of any sort of wild or feral pig population from a mainland habitat. Many U.S. states have attempted feral pig eradication for decades, yet no state with feral pigs has achieved a net reduction.
Further, since pigs and wild boars are cannibalistic, they are often their own most significant natural predator. Adult male boars frequently kill piglets if finding them unguarded by their mothers. Killing adult boars during the spring birthing season is, accordingly, more likely to ensure that more piglets survive to maturity than to lastingly reduce the population.
History of the disease
“African swine fever spread from Africa to Portugal in 1957 as a result of waste from airline flights being fed to pigs near Lisbon,” recalled ProMed infectious diseases moderator Arnon Shimshony. “Although this incursion of the disease was eradicated, a further outbreak occurred in 1960 in Lisbon, and African swine fever remained endemic on the Iberian peninsula until the mid-1990s.”
Further outbreaks hit France, Italy, Malta, Belgium, and the Netherlands. “The disease was eradicated from each of these countries,” Shimshony said, “but in Sardinia it has remained endemic since in 1982.”
African swine fever jumped to Brazil in 1978, but was eradicated by culling after 224 reported outbreaks.