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Coronaviruses in pigs – what do they cause?


The last few months have been a whirlwind, coronavirus disease (Covid-19) having placed most of the world in a lockdown like many have never experienced. Yet coronavirus itself has existed for a long time – the pathogen SARS-CoV-2 is the latest family member. Which coronaviruses are known to affect pigs? And why doesn’t this one affect pigs?


BY DR DAVID TAYLOR, PROFESSOR EMERITUS, FACULTY OF VETERINARY MEDICINE, GLASGOW UNIVERSITY, UK AND VINCENT TER BEEK, EDITOR, PIG PROGRESS


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nfluenza virus perhaps – or the AIDS virus. If, in late 2019, a survey had asked what was the world’s most well- known virus, then one of these might have been the an- swer. Fast forward a couple of months and it’s pretty clear


that the world has a new number one: coronavirus – or more correctly, SARS-CoV-2, the causative agent of Covid-19. Coronaviruses, however, are nothing new. They have been around for a long time and, as viruses do, they tend to mutate to a certain degree and can change host from time to time. Prior to SARS-CoV-2 being around, there already were six coronaviruses known to affect the health of humans, of which the ones causing MERS and regular SARS are the most well


Porcine Respiratory Coronavirus (PRCv)


How does it cause disease? PRCv is a coronavirus very closely related to TGE that causes damage and fused cells in cell cultures. It can be isolated from the lungs of infected pigs. When PRCv is present with an- other virus, lesions in the lung are more severe than with PRCv alone.


Mode of transmission Transmission is by direct contact and aerosol; the disease spreads rapidly within a herd once introduced. Transmission between farms is usually by means of carrier pigs.


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Clinical signs Infection with PRCv may result in the produc- tion of serum antibodies at three to five months of age in some herds in which mater- nal antibody is present, but coughing and in- appetence have been reported in others. In- appetence, reluctance to move, laboured respiration and fever (40°C) have been report- ed one to five days following experimental infection of antibody-free conventional pigs.


Treatment and prevention The only indication for control at present is


▶PIG PROGRESS | Volume 36, No. 4, 2020


that infected pigs are seropositive for TGE and infection therefore interferes with the certification of herd for freedom from TGE. This problem has been approached by founding and maintaining antibody-free herds through rigorous testing and isolation. This experience confirms that it is possible to obtain and maintain herds free from the in- fection, but there is no other commercial reason to do so. Disinfection should happen in a similar way as for TGE. An experimental vaccine has been produced but none are available commercially.


known. They and their cousins often cause respiratory disease to a mild or grave degree. And it’s not only humans that can contract coronaviruses – several of them also affect livestock, causing well-known dis- eases like infectious bronchitis in chickens or bovine corona- virus in calves.


Coronavirus in pigs Pigs are known to be affected by six different strains of coro- navirus. The most well-known of these affect the gastrointes- tinal tract; think for instance of Porcine Epidemic Diar- rhoea virus (PEDv). One similar to PEDv is Transmissible Gastroenteritis virus (TGEv). Another cause of PED is Por- cine Deltacoronavirus. Relatively new – since 2018 – and also affecting the gastrointestinal tract is Swine Acute Diar- rhoea coronavirus (SADS-CoV). Affecting the respiratory tract is Porcine Respiratory Coronavirus. Last, but not least, is Haemagglutinating Encephalitis virus (HEv, a Betacoronavirus) which causes Vomiting and Wasting Dis- ease. The most common ones are discussed in more detail in the side boxes with this article.


Coronaviruses – what are they? Coronaviruses are enveloped, single-stranded positive sense RNA viruses. The envelope or outer coat is vulnerable to


ILLUSTRATION: SHUTTERSTOCK


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