Porcine hemagglutinating encephalomyelitis (PHE) virus

Test code: S0133 - Ultrasensitive qualitative detection of porcine hemagglutinating encephalomyelitis (PHE) virus by reverse transcription coupled real time PCR

Coronaviruses are divided into at least three serogroups (I–III) based on serology and nucleotide differences. Porcine hemagglutinating encephalomyelitis virus (PHE) belongs to group II, and it is the etiological agent of hemagglutinating encephalomyelitis. This disease primarily affects pigs <3 weeks of age. Currently only a single strain of the virus is known and is the only known neurotropic coronavirus in pigs.

Affected piglets usually exhibits vomiting, anorexia and depression; hence the disease was known as "vomiting and wasting disease" (VWD) in the past. In severe cases infected piglets will develop encephalomyelitis. The mortality rate in infected piglets under 3 weeks old is nearly 100%, but the incidence of infection is small as most piglets are protected by maternal antibodies. However, the risk of PHE outbreaks has increased due to the use of pathogen-free pigs which have no antibodies to the virus.

PHE has been reported in many countries, including mainland China and Taiwan, since it first appeared in Canada in 1958. The primary sign of disease outbreak is repeated retching and vomiting in piglets, although there may be mild respiratory signs initially. Piglets huddle and are listless, and there may be a transient fever. Young nursing piglets often become severely dehydrated and die. Older nursing or weaned piglets suffer from physical wasting with loss of weight and muscle mass due to inadequate feed intake. They may persist in a wasting state for several weeks before dying. The abdomen may be distended due to gaseous distension of the stomach and intestines.

The virus is transmitted via nasal secretions (Sasseville et al., 2001) and replicates in epithelial cells of the nasal mucosa, tonsils, lungs, and small intestine. After local replication, the virus spreads from the peripheral nervous system to the central nervous system. Virus can be isolated from the tonsils and respiratory tract during the incubation period, which lasts about 5 days. Isolation of virus may be attempted on tonsil, brain, and lung samples from affected piglets. However, culture sensitivity is low unless samples are collected from acute cases within 1 or 2 days of the onset of clinical signs. Serological diagnosis is neither sensitive nor specific enough to quickly identify the virus during the initial outbreak. Molecular detection by reverse transcription coupled real time PCR enables rapid, sensitive and specific detection of the virus and is useful in identifying and isolating infected pigs.

Utilities:

• Confirm the disease causing agent
• Identify PHEV carriers
• Ensure that animal colonies and populations are free of PHEV
• Early prevention of spread of the virus among animals
• Minimize human exposure to the virus
• Safety monitoring of biological products that derive from animals

References:
Sasseville, A.M., Gelinas, A.M., Sawyer, S., Boutin, M. and Dea, S. (2001) Biological and molecular characteristics of an HEV isolate associated with recent acute outbreaks of encephalomyelitis in Quebec pig farms. Adv Exp Med Biol. 494:57-62.

Specimen requirements:  Nasal swab or 0.5 ml fresh or frozen tissue.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative reverse transcription coupled real time PCR

Normal range: Nondetected