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Artist’s impression of SARS-CoV-2, the causative agent of Coronavirus 2019.


disinfectants and heat and consists of protein spikes that in- teract with receptors on cells of the animal or bird body so that the virus can invade. Single-stranded RNA viruses are simple and, during replication, can take up pieces of RNA


from other viruses or be copied by mistake, losing or altering their RNA by deletion or point mutations. These altered viruses may be unable to reproduce, but some may be able to colonise an individual animal, either wholly or


Haemagglutinating Encephalitis virus (HEv)


How does it cause disease? The coronavirus HEv can cause Vomiting and Wasting Disease when infecting young pig- lets. Just like SARS-CoV-2, this virus is a betacoronavirus. It is widespread, transmitted by the respiratory route to infect the respira- tory tract. After oronasal infection, clinical signs develop within three to five days. Mater- nal antibodies in colostrum prevent the disease for up to 15 weeks.


Mode of transmission Infection spreads throughout the herd in na- sal secretions. The virus circulates in older growers and young finishers in which it does


not cause clinical disease. Clinical disease oc- curs in the piglets of non-immune sows. Infec- tion appears to spread from herd to herd in carrier pigs.


Clinical signs Piglets aged between five days and three weeks are affected. The virus infects nerves and is carried to the brain and gastric nerves to cause the clinical signs. The first signs to be noted are vomiting, huddling of the piglets which may be associated with a rise in tem- perature, depression, inappetence and consti- pation. Some affected animals may show signs of


encephalomyelitis, such as hind leg weakness or difficulties in swallowing. Affected piglets die within 28–36 hours or become progres- sively emaciated. The virus is asymptomatic in older pigs.


Treatment and prevention There is no vaccine, and control in non-infect- ed herds depends on the maintenance of a closed herd or the purchase of stock from herds known to be free from the disease. In infected herds, the only preventative measure is to ensure access to colostrum. Disinfection is possible. This virus is not of public health significance.


▶PIG PROGRESS | Volume 36, No. 4, 2020 7


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