Vet on call: Hope at last for vaccine in war on swine fever

I have persistently been on the case of the dreaded African swine fever (ASF) for the past few months. The main reason is that I have continued to get readers’ queries on the disease and reports from many farmers of a disease fitting the ASF case definition.

In addition, ASF has since 2018 relentlessly devastated the pork industry in China, south-east Asia and some eastern European countries. China alone is estimated to have lost about half of its total pig population.

It is the largest world pig producer and consumer with a population of over 500 million pigs. The pig numbers make the Kenyan population of about 400,000 insignificant.

One farmer from Ruiru has continually bombarded me with questions on ASF since November last year after he lost all his animals.

He wonders why, with all the scientific information available on the disease and the impact of ASF on trade and swine welfare, no country has found a cure or vaccine for the disease. He has also asked me whether there is any research work going on in Kenya towards finding a cure for the disease.

Well, it is now refreshing to know that scientists in China and the United States could soon provide a lasting solution to the disease.

Two premier animal disease research institutes in the countries have published reports that they have independently developed two vaccines with great promise to immunise pigs against ASF.

The Harbin Veterinary Research Institute of China says their vaccine has proved highly effective against the strain of ASF that has devastated the Chinese pig industry. The disease has also spread to other south-east Asian and eastern Europe countries since its outbreak in 2018.

REGULATORY PROTOCAL

On the other hand, the United States Plum Island Animal Disease Centre has reported in the reputed Journal of Virology that it has developed an ASF vaccine that is 100 per cent effective in protecting pigs against the virus strain that caused the Chinese outbreak.

They are very optimistic about their innovation because the current strain is known to be more virulent than previously isolated ones. This means it has a very high capacity to infect and kill pigs.

The reports are credible because they come from two government institutions of high scientific repute. However, scientists in both facilities have cautioned that farmers will still have to wait for some time before the vaccines can be available for commercial use.

The results they published were laboratory test findings. Regulatory protocol globally requires medical products to be tested thoroughly before they can be licensed for commercial use locally and internationally. The good news is that there is credible hope of viable vaccines from highly reputable sources.

So, what took the world so long in coming up with what is medically called viable vaccine candidates for ASF? The farmer from Ruiru has consistently insisted that scientists are lazy and do not want to think beyond the obvious. In my view, that is a very harsh judgment from a frustrated farmer. When challenged, scientists do not rest until they get a solution to a problem.

A lot of work has actually been done on ASF vaccine research. Scientists, however, found out that the earlier methods of vaccine development were unsuitable for the ASF virus.

There were initially two main ways of making vaccines, that is, using inactivated viruses and using viruses that had been stripped of their disease-causing ability by being grown many times in a series of different growth media. Such virus vaccines are called killed and attenuated vaccines respectively.

NEW VACCINES

The new vaccines reported by the two research institutes are now possible because of high-tech development of molecular microbiology. This is the study of the components that make disease-causing organisms.

The new promising vaccines reported were developed using a molecular microbiology technique known as gene deletion. In this process, scientists use advanced scientific equipment. They predict the parts of the virus particles that are responsible for causing disease and the genes that produce them.

They then cut off the genes from the virus particles and the virus loses its ability to cause disease. In other words, it becomes an attenuated virus but retains the ability to stimulate the animal’s body to produce immunity chemicals called antibodies.

The antibodies kill the virus every time there is an infection and, therefore, prevent development of the full-blown disease.

Before the 2018 Chinese ASF outbreak, the disease was restricted to a few countries with low pig populations and very little trade in pigs and pig products.

The current outbreak in China has turned the tables just like the West African Ebola outbreak of 2014. It left the global science and political leaders with the realisation that ASF was a big threat to world swine production, trade and food security.

The realisation jump-started concerted efforts in development of viable vaccines. Fortunately, the research activities were boosted by the existence of novel vaccine development technologies.

Similar research is also ongoing in Kenya at the International Livestock Research Institute and in Canada.