If world is going to beat ASF, need to consider social science

The African swine fever epidemic will not be controlled by only considering the biological particularities of the disease.

 

Source: Meristem Land and Science

via National Hog Farmer - Jan 09, 2020

 

Twelve years ago, African swine fever outside of Africa was a so-called exotic disease with minor impact. That has changed drastically. ASF is one of the most imminent threats to the global pig-farming sector with no drugs or vaccines available to cure or prevent the disease.

 

To prevent, control and eradicate ASF is a big job Klaus Depner of the Friedrich-Loeffler-Institute, told attendees at the 2020 Banff Pork Seminar. If we are going to beat this disease the world need to look beyond just biological and include social science, he says.

 

"Knowledge about disease biology, epidemiology and the human-host interactions is needed. But humans are recognized as the main cause of both long-distance transmission and virus introduction into domestic pig farms," says Depner. "By considering only the biological particularities of the disease, contagiosity, tenacity and case fatality rate, but ignoring the human aspects, the epidemic will not be controlled. It is crucial to include social science when planning prevention, control or eradication measures."

 

Tracking ASF origins

 

The ASF epidemic started in Georgia in 2007 and subsequently spread throughout the Caucasus and the Russian Federation. In 2014, ASF reached the European Union and four years later the first outbreaks were reported in Asia. In several European countries the disease has become endemic in the wild boar populations, while it could still be managed in domestic pigs.

 

When ASF reached the EU, it was expected to either spread rapidly within the wild boar population or fade out due to high case fatality rate and the absence of long-term carriers. The current situation, where the disease has become endemic in several countries, shows that none of these predictions held true. The infection survived locally in the wild boar population independently from outbreaks in domestic pigs.

 

In addition to local transmission in wild boars, long distance jumps into disease-free areas occurred. Human activities have been identified as main drivers of disease transmission in the domestic pig epidemiological cycle.

 

The disease and the ASF virus

 

The ASFV strain in the current epidemic is highly virulent. While the disease is asymptomatic in warthogs, domestic pigs and wild boar mostly develop a severe haemorrhagic disease and die within a couple of days. If na´ve pigs come into contact with the diseased animal or its secretions, some will become infected, and meet the same destiny.

 

However, the case fatality rate (proportion of infected individuals that succumb to the disease within a certain time period) is high, often reaching 90-100%. So far, there is no evidence that the few survivors may become carriers playing a significant role in the ASF epidemiology.

 

The ASF virus has been shown to be relatively stable in the environment (high tenacity). It survives the process of putrefaction, and carcasses of infected animals may remain infectious for weeks. In frozen meat, the virus may survive for several years, in dry meat and fat almost one year, in blood, salted meat and offal more than three months, in feces over one week.

 

Given this tenacity data, it is easy to understand why and how contaminated meat and meat products have played a crucial role in ASF transmission and epidemiology.

 

ASF contagiosity ...

 

High risk period ...

 

Persistency triangle ...

 

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