Minimizing PRRS impact through better farm management

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Negligence with PRRS vaccination has led to severe damage at swine farms.

HA THU and the Asian Agribiz team look at the current PRRS situation in the region, as well as new strains of the disease, and strategies to control its spread.

The dangers of other pig diseases are being overshadowed as all the attention is centered on African swine fever (ASF).

The other disease of concern to the pig industry in the region is Porcine Reproductive and Respiratory Syndrome (PRRS).

Although there are PRRS vaccines, the prevention and control of this disease still faces many challenges.

Still raging

PRRS has become a common disease in Vietnam, causing damage mainly in lactating sows and fattening pigs.

There are three common strains in the country: the North America VC-2332, the Chinese JXA1-2007 and SX-2009 strain, and European Lelystad Virus strain.

The disease causes significant damage to pig farms in Vietnam with infection rates ranging from 20-30% of the total herd.

Nguyen Van Minh

“In most cases, PRRS does not cause high mortality directly but causes clinical effects such as reduced productivity and respiratory disorders, which lead to pig deaths, culling, and veterinary costs,” Nguyen Van Minh, Director of Vet24h Animal Health Services told Asian Agribiz.

In Indonesia, PRRS is not a big problem, claimed a pig producer.

However, it continues to cause losses to farmers as it causes reproductive failure in sows and respiratory illness in pigs of all ages, Mikael Darmawan, owner of Cipta Jaya Farm, in East Java, told Asian Agribiz. 

Mikael Darmawan

He observed that many pig farmers imported frozen semen to improve their pig genetics. However, they do not have the semen tested. He suspects that this might be the cause of the infection, apart from illegal PRRS vaccines.

Meanwhile in India and Sri Lanka, PRRS has been disastrous for their pig herds.

The disease led the Sri Lanka’s government to introduce a countrywide vaccination program in January last year to stave off the disease.

Dr Sameera Premaratne

“This was done for the first time in Sri Lanka along with strict biosecurity guidelines,” said Dr Sameera Premaratne from the National Livestock Development Board who studied the outbreak.

Do existing vaccines work?

One of the biggest causes of PPRS still raging despite the availability of vaccines seems due to low injection rates and poor quality of vaccines.

However, at present, the complicated situation of ASF has led to low pork prices. Producers in the region tend to cut costs, including costs for PRRS vaccine in piglets and porkers.

“This is the main risk leading to different levels of PRRS outbreaks in pig farms in Vietnam,” said Mr Minh of Vet24h.

PRRS can cause death in pigs of all ages.

The effectiveness of vaccines against PRRS (PRRSV) has been a huge issue in India because of the genetic heterogeneity of the virus.

“Commercially available vaccines at present may not be effective against all strains. Researchers say they are effective only against the homologous strain,” said Prof Tridib Kumar Rajkhowa of the Department of Veterinary Pathology, College of Veterinary Sciences & Animal Husbandry, Central Agricultural University in Selesih, Aizawl.

Khampee Kortheerakul, an independent swine veterinary consultant, told Asian Agribiz that the NADC30-like PRRSV first occurred in Thailand in 2019.

“Before the NADC30-like PRRSV entered Thailand, the existing vaccine, which works effectively against the old PRRS strains, didn’t seem to prevent it,” he said.

When the NADC30 strain entered pig farms, the mortality rate was about 30%, Dr Khampee said.

New PRRS strains

Last year, in late October and early November, the Swine Disease Reporting System reported a significant increase in PRRSV cases from Minnesota and Iowa classified as RFLP 1-4-4, the restriction length polymorphism, introduced in 1998 to distinguish wild-type PRRSV strains from the vaccine strain, VR2332.

The new variant projects the same clinical symptoms as the previous PRRS virus but is much more potent. The worst impact of PRRSV is when infected pigs move to new areas. Outbreaks can result in mortality rates of 50-80% in the late-nursery period.

The hallmark of this virus is necrosis in the thymus and lymph nodes, in addition to severe lung damage. Both organs are important for the immune response, and the marked dysfunction of immunocompromised tissues makes it easier to develop other diseases, especially in the porker farm environment.

Pigs died from high virulent PRRS Chinese strain.

Dr Ooi Peck Toung, Professor at Universiti Putra Malaysia explained to Asian Agribiz that based on the field report cases, the new PRRS 144 seems virulent and causes great economic losses.

“For the effectiveness of the existing vaccines, I believe we require more field data and figures before we can have any meaningful suggestion. As the current information might not be sufficient,” Dr Ooi said.

Threat to the regional industry

This new strain has not been recorded in any country in the region. However, industry experts emphasized a risk of an outbreak coming from trade activities of pork and live pigs within neighboring countries in the region.

“Every time a new PRRS strain mutates, there is the possibility that it is more virulent than the current. What is happening in the US with PRRS 144 Lineage 1C is an example. Just like the HP-PRRS situation we had some years ago,” Dr Roselle Cudal, Elanco Animal Health’s Technical Consultant for Swine in the Philippines told Asian Agribiz.

Prof Rajkhowa of Central Agricultural University in Selesih said a new outbreak of PRRS would have a huge impact on the Indian pig industry because of high mortality and reproductive problems.

“India is already struggling to cope with the spread of ASF in the northeast. This would only add to its woes,” he added.

Also, industry experts believe that the new strains of PRRS will cause a decline of the region’s pork exports.

Minimizing the impact

There will always be new strains, said Dr Cudal.

In addition to focusing on research and production of vaccines to keep up with the progress of the virus, industry experts believe that there are many other measures that need to be taken to protect the pig herds.

Here are their recommendations:

1. Improve farm management tailored for pigs at different ages.
2. Applying all-in-all-out production model.
3. Implement and control biosecurity.
4. Porker farms should produce their own piglets to control the breed quality and avoid disease infection via semen and pig transportation.
5. Applying vaccination against PRRSV, along with immune system boosters. 

On effective use of vaccines, they have the following advice:

1. Raising awareness among farmers about the importance of vaccines.
2. Educating farmers to use reputed PRRS vaccines that are effective to the circulating PRRS virus strains in the country.
3. Making antibody assessment before and after injection to validate the quality of vaccination.
4. Avoid using more than one PPRS vaccine without having consulted with veterinarians.

On avoiding the use of more than one PPRS vaccine, Mr Minh of Vet24h said in many farms in Vietnam, especially private farms, two types of PRRS vaccine are used in one farm for pigs of different ages.

For example, farmers tend to use North American strain PRRS vaccines (from different companies) for gilts and sows and use highly virulent PRRS Chinese strain for piglets.

“There is a potential risk of an outbreak due to a re-emergence of the virulent vaccine virus, or a mutation, and complicated PRRS epidemiology in the farm and the risk of PRRS and PRDC outbreaks causing persistent damage to the farm,” Mr Minh explained.

Read more:
PRRS pulls down Thailand’s pork supply
Cambodia’s pig sector hit by PRRS
Beyond ASF: Pathogens that should not be ignored