African Swine Fever (ASF) killed more than 33,000 pigs in Mizoram and cost the state losses amounting to over Rs 60 crore in the 2021 outbreak, said Dr K Beichhua, state's Animal Husbandry and Veterinary Services Minister, in the Assembly on February 28, 2022.

The outbreak led to the culling of 10,910 pigs to prevent further spread of the disease and a ban on import of pigs from neighbouring states and countries for about 17 months (August 2020-January 2022).

Mizoram is not the only state to have been affected by this virus. In fact, ASF killed 38,700 pigs in Assam, News 18 reported in July 2021. The virus had also spread to Meghalaya, killing about 300 pigs. Further, cases were also detected in districts of Arunachal Pradesh, Nagaland and Tripura.

There are around 90 lakh pigs in India, which is 1.7% of the total livestock in the country. Of this, nearly half (46.85%) of the pig population is in the north-eastern states, according to a June 2020 report by the Union Ministry of Fisheries, Animal Husbandry and Dairying.

The Food and Agriculture Organization of the United Nations (FAO) has said several cases of ASF have also been reported in other Southeast Asian countries such as China, Bhutan, Myanmar, Thailand, Indonesia, etc since August 2018.

What is African Swine Fever?

ASF is a highly contagious hemorrhagic viral disease affecting domestic and wild pigs and boars with up to 100% case fatality rate, according to the World Organisation for Animal Health (WOAH). The disease does not affect humans (non-zoonotic) or other livestock species.

Some of the main symptoms of the disease are high fever, diarrhoea, vomiting with or without mucus and blood, inappetence and frothy discharge from nose, difficult breathing and red patches of the skin on the ears, abdomen, chest, tail and hind legs which may turn into bluish purple colour at later stages.

African Swine Fever and Classical Swine fever are two different diseases with similar symptoms. "ASF is caused by a virus that is not related to the CSF virus and has a more complex genetic structure. While ASF is caused by the DNA virus, CSF is caused by the RNA virus," Dr Aksay Kesari, district veterinary officer in Assam's Sivasagar, told FactChecker. He added that the mortality rate is higher in ASF than CSF.

This transboundary animal disease (TAD) is identified by the sudden and mass death of pigs. While it can be directly transmitted by live or dead pigs through blood, tissues, secretions and excretions, recovered pigs may also act as a carrier.

It can also spread via contaminated feed and fomites (non-living objects that likely carry infection) such as clothes, shoes, vehicles, knives and other equipment. The virus can remain active up to three years in different contaminated materials. Further, the incubation period ranges from 4-19 days.

ASF was first detected in Kenya in 1921 when European pig breeds were introduced in the East African country. The next case was only detected in 1957 in Portugal. After 10 years, it spread to Italy, Spain, Cuba, France in the 1970s.

It first hit China in August 2018 followed by Southeast Asian countries such as Vietnam, Myanmar, South Korea, etc. India was the 30th country to have been affected by this disease for the first time in May 2020, according to an October 2020 study published in the National Center for Biotechnology Information.

Why Has It Struck North East India?

In Mizoram, the first unusual death of pigs was detected on March 21, 2021 at Lungsen village in Lunglei district and the sample was sent to National Institute of High Security Animal Diseases (NIHSAD) of Indian Council of Agricultural Research, Bhopal where it was tested positive for ASF by RT-PCR on April 15, 2021, Dr Lalhmingthanga, Joint Director (Livestock Health), Department of Animal Husbandry and Veterinary, Mizoram told FactChecker.

He said the source of this virus is believed to be illegal movement of pigs from neighbouring countries. "Mizoram shares its boundaries with Myanmar and Bangladesh and there were reports of illegal movement of pigs from these countries," said Dr Lalhmingthanga.

While the consumption of poultry is rapidly increasing, pork is the most consumed meat globally, according to a 2019 study published in the International Journal of Current Microbiology and Applied Sciences. In India, the highest pig population is in Assam (1.63 million), followed by Uttar Pradesh, (1.33 million), Jharkhand (0.96 million), Bihar (0.65 million) and West Bengal (0.65 million). Whereas, the consumption is concentrated in the northeastern region.

Pig farming is also a source of livelihood for thousands of farmers across all the north eastern states, said Dr Lalhmingthanga. That may be the reason why the ASF virus spreads in the north eastern states, he said.

"The north eastern states share their boundaries with neighbouring countries where ASF was already reported, like Myanmar and China," he explained. Another reason could be unrestricted movement without checking health records of piglets along the borders of Myanmar, Bangladesh and Tibet.

Assam's Sivasagar district alone reported three ASF outbreaks in 2020 and 2021. "Around 2,700 confirmed deaths took place in our district. But there were around 5,000 unconfirmed deaths of pigs too," said Dr Kesari.

No vaccines

Since there are no vaccines available commercially, culling and killing infected pigs is the only way to curb the infection from spreading. The main hurdle in developing the vaccines is the complex nature of the virus coupled with its large number of proteins evading the host-immune system, the 2020 NCBI study says.

The state government notified the outbreak of ASF in Mizoram under the Prevention and Control of Infectious and Contagious Diseases in Animals Act, 2009 and laid out a standard operating procedure for control, containment and eradication of the virus.

This protocol includes declaration of infected premises and surveillance zones, movement restrictions and also banned pig marketing. Professional pig culling teams, constituting one veterinary doctor, one para-veterinarian and armed police, were formed in all districts of Mizoram to cull suspected pigs from infected areas which showed the signs and symptoms of ASF, said Dr Lalhmingthanga.

"Cleaning of infected premises and safe carcass disposal was also carried out by this team following proper protocol wherein deep pits were excavated and culled pigs were properly buried with lime," he explained. "The service of police personnel had been obtained for humane killing with appropriate firearms," he added.

In 2019, India imported $2.87 million in pig meat, becoming the 106th largest importer of pig meat in the world, according to the Observatory of Economic Complexity (OEC), a data visualisation platform. Between 2018 and 2019, India mainly imported from Spain, Belgium and the US while United Arab Emirates, Bhutan and France were the fastest growing export markets for pig meat in the country. However, it is worth noting that India has seen a declining trend in the overall pig population. The 2012 Livestock Census showed that the pig population declined by 7.54% and the latest 20th census showed a further reduction of 12.03%.

Economic Losses

The farmers and the government have faced substantial losses due to the virus. As many as 33,417 pigs have died and 10,910 pigs were culled out till December 31, 2021. In all, the economic loss is estimated to be over 2 billion, said Dr Lalhmingthanga.

"​​The economic loss is calculated considering the cost of animal, feed, veterinary services, medicines, labour, market loss, utility, fuels, electricity, water and expenditure incurred for carcass disposal," the joint director of the animal husbandry department told FactChecker.

The state's Animal Husbandry & Veterinary Services department has proposed to the Centre that Rs 11.68 crore should be given to affected families as compensation. The state has proposed to bear half of the compensation amount with the Centre.

The spread has, however, decreased in Mizoram since December and there have been no fresh cases of ASF. "The decline in death may be due to the several measures implemented like culling of pigs, movement restrictions, ban on import of pork and pig byproducts as well as ban on pork marketing," Dr Lalhmingthanga said. Similarly Dr Kesari also said the last reported case in his district was in September 2021. "In over six months, we have not seen any swine mortality in our district," he concluded.