Pseudorabies

Last updated
Suid alphaherpesvirus 1
Virus classification OOjs UI icon edit-ltr.svg
(unranked): Virus
Realm: Duplodnaviria
Kingdom: Heunggongvirae
Phylum: Peploviricota
Class: Herviviricetes
Order: Herpesvirales
Family: Herpesviridae
Genus: Varicellovirus
Species:
Suid alphaherpesvirus 1
Synonyms [1]
  • Suid herpesvirus 1
  • Pseudorabies virus

Aujeszky's disease, usually called pseudorabies in the United States, is a viral disease in swine that is endemic in most parts of the world. It is caused by Suid herpesvirus 1 (SuHV-1). Aujeszky's disease is considered to be the most economically important viral disease of swine in areas where classical swine fever (hog cholera) has been eradicated. [2] Other mammals, such as cattle, sheep, goats, cats, dogs, and raccoons, are also susceptible. The disease is usually fatal in these animal species.

Contents

Research on SuHV-1 in pigs has pioneered animal disease control with genetically modified vaccines. SuHV-1 is now used in model studies of basic processes during lytic herpesvirus infection, and for unravelling molecular mechanisms of herpesvirus neurotropism. [3] [4]

History

In 1902, a Hungarian veterinarian, Aladár Aujeszky, demonstrated a new infectious agent in a dog, ox, and cat, and showed it caused the same disease in swine and rabbits. In the following decades the infection was found in several European countries, especially in cattle, where local intense pruritus (itching) is a characteristic symptom. In the United States, a well known disease in cattle called "mad itch" was concluded to be in fact Aujeszky's disease. [5]

Disease overview

Wild pigs seropositive for pseudorabies in the United States

.mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;margin:1px 0;text-align:center;border:1px solid black;background-color:transparent;color:black}.mw-parser-output .legend-text{}
Present

Absent Pseudorabies in Wild Swine, distribution in USA.svg
Wild pigs seropositive for pseudorabies in the United States
  Present
  Absent

The virus is shed in the saliva and nasal secretions of swine infected by the respiratory route. Aerosolization of the virus and transmission by fomites also may occur. The virus may potentially survive for seven hours in humid air, and it may survive on well water for up to seven hours, in green grass, soil, and feces for up to two days, in contaminated feed for up to three days, and in straw bedding for up to four days. [6]

Diagnosis is made mainly by virus isolation in tissue cultures, or through ELISA or PCR tests. Vaccines are available for swine (ATCvet codes: QI09AA01 ( WHO ) inactivated, QI09AD01 ( WHO ) live, plus various combinations). [7] The infection has been eradicated in a number of European countries. In the United States, the domestic swine population in 2004 was declared free of Aujeszky's disease, though the infection still remains in feral pig populations. [8]

Clinical signs

Respiratory infection is usually asymptomatic in pigs more than two months old, but it can cause abortion, high mortality in piglets, and coughing, sneezing, fever, constipation, depression, seizures, ataxia, circling, and excess salivation in piglets and mature pigs. Mortality in piglets less than one month of age is close to 100%, but it is less than 10% in pigs between one and six months of age. Pregnant swine can reabsorb their litters or deliver mummified, stillborn, or weakened piglets. [9] In cattle, symptoms include intense itching followed by neurological signs and death. In dogs, symptoms include intense itching, jaw and pharyngeal paralysis, howling, and death. [2] Any infected secondary host generally only lives two to three days. [6]

Genital infection appears to have been common in a great part of the 20th century in many European countries in swine herds, where boars from boar centres were used for natural service of sows or gilts. This disease manifestation has always been asymptomatic in affected pigs, and presence of the infection on a farm was detected only because of cases in cattle showing pruritus on the hindquarters. [10]

In susceptible animals other than swine, infection is usually fatal, and the affected animals most often show intense pruritus in a skin area. Pruritus in Aujeszky's disease is considered a phantom sensation as virus has never been found at the site of pruritus. [11]

Pathogenicity and virulence of SuHV-1

The epidemiology of Aujeszky's disease varies with the pathogenicity or virulence of the virus strain involved. This is best illustrated by the development of the severity of the disease in Denmark, where import of swine had been forbidden for decades up to 1972. Before 1964 only genital strains were spread, but then respiratory strains appeared, which subsequently were spread rapidly over the country, mainly by the trade of animals. In the late 1970s more virulent strains developed. The disease in swine became much more severe, outbreaks of respiratory disease in cattle rose dramatically, and the infection was spread airborne to other swine herds. The higher virulence of these virus strains was associated with a certain ability to create syncytia (cell fusion) in tissue cultures (syncytial virus strains). Comprehensive restriction fragment pattern analyses of virus DNA have documented that the more virulent strains had not been introduced from abroad but had developed in two steps from the original Danish strains. The correlation between high virulence of virus strains and syncytium formation in tissue cultures was confirmed by examinations of isolates from other countries. This second step in the severity development of the disease in Denmark caused the decision to eradicate. New outbreaks after the eradication of the indigenous infection by the end of 1985 were all caused by foreign highly virulent, syncytial strains introduced by airborne transmission from Germany. [11]

Briefly, SuHV-1 is spread either genitally or respiratorily. Genital strains have been found to be non-syncytial. Respiratory strains may be of relatively low or of high virulence. In Europe, syncytial strains have been found to be highly virulent.

Epidemiology

Populations of wild boar, or feral hogs (Sus scrofa), in the US commonly contract and spread the virus throughout their range. Mortality is highest in young piglets. Pregnant sows often abort when infected. Otherwise healthy male adults (boars) are typically latent carriers, that is, they harbor and transmit the virus without displaying signs or experiencing disability. [12]

Swine (both domestic and feral) are usual reservoirs for this virus, though it does affect other species. Aujeszky's disease has been reported in other mammals, including brown bears, and black bears, Florida panthers, raccoons, coyotes, and whitetail deer. In most cases, contact with pigs or pig products was either known or suspected. Outbreaks in farm fur species in Europe (mink and foxes) have been associated with feeding contaminated pig products. Many other species can be experimentally infected. Humans are not potential hosts. [13]

Cattle have been found to be infected either by the respiratory or the vaginal route (iatrogenic cases disregarded). Primary infection of mucous membranes of the upper respiratory tract is associated with head pruritus, while lung infection results in chest pruritus. Vaginal infection of bovines, which regularly show pruritus of the hindquarters, has been found to be associated with a concurrent genital infection in swine on the same premises, and investigations have evidenced that the vaginal infection of cattle had been sexually transmitted by man from infected sows.[ citation needed ] Genital infection in swine herds has been closely correlated with the use of boars from boar centres for natural service of sows. [11]

Transmission

Aujeszky's disease is highly contagious. The infection is commonly considered to be transmitted among swine through nose-to-nose contact, because the virus is mostly present in nasal and oral areas. This notion, however, is contradicted by results from epidemiological studies, according to which the decisive spread within herds occurs by air currents over many meters. Correspondingly, the risk of airborne transmission of highly virulent virus strains from acutely infected herds to other swine herds has been found to be very high. The infection has been found transmitted over distances of many kilometers. [11] Otherwise, the infection is most often transmitted into herds by introduction of acutely or latently infected pigs. Concerning transmission to cattle, see section above.

Prevention

Although no specific treatment for acute infection with SuHV-1 is available, vaccination can alleviate clinical signs in pigs of certain ages. Typically, mass vaccination of all pigs on the farm with a modified live virus vaccine is recommended. Intranasal vaccination of sows and neonatal piglets one to seven days old, followed by intramuscular (IM) vaccination of all other swine on the premises, helps reduce viral shedding and improve survival. The modified live virus replicates at the site of injection and in regional lymph nodes. Vaccine virus is shed in such low levels, mucous transmission to other animals is minimal. In gene-deleted vaccines, the thymidine kinase gene has also been deleted; thus, the virus cannot infect and replicate in neurons. Breeding herds are recommended to be vaccinated quarterly, and finisher pigs should be vaccinated after levels of maternal antibody decrease. Regular vaccination results in excellent control of the disease. Concurrent antibiotic therapy via feed and IM injection is recommended for controlling secondary bacterial pathogens. [14]

Applications in neuroscience

SuHV-1 can be used to analyze neural circuits in the central nervous system (CNS). For this purpose the attenuated (less virulent) Bartha SuHV-1 strain is commonly used [15] and is employed as a retrograde [16] and anterograde [17] transneuronal tracer. In the retrograde direction, SuHV-1-Bartha is transported to a neuronal cell body via its axon, where it is replicated and dispersed throughout the cytoplasm and the dendritic tree. SuHV-1-Bartha released at the synapse is able to cross the synapse to infect the axon terminals of synaptically connected neurons, thereby propagating the virus; however, the extent to which non-synaptic transneuronal transport may also occur is uncertain. Using temporal studies and/or genetically engineered strains of SuHV-1-Bartha, second, third, and higher order neurons may be identified in the neural network of interest.

See also

Related Research Articles

Classical swine fever (CSF) or hog cholera is a highly contagious disease of swine. It has been mentioned as a potential bioweapon.

<span class="mw-page-title-main">Swine influenza</span> Infection caused by influenza viruses endemic to pigs

Swine influenza is an infection caused by any of several types of swine influenza viruses. Swine influenza virus (SIV) or swine-origin influenza virus (S-OIV) refers to any strain of the influenza family of viruses that is endemic in pigs. As of 2009, identified SIV strains include influenza C and the subtypes of influenza A known as H1N1, H1N2, H2N1, H3N1, H3N2, and H2N3.

Streptococcus suis is a peanut-shaped, Gram-positive bacterium, and an important pathogen of pigs. Endemic in nearly all countries with an extensive pig industry, S. suis is also a zoonotic disease, capable of transmission to humans from pigs.

Betaarterivirus suid 1, commonly Porcine reproductive and respiratory syndrome virus (PRRSV), is a virus that causes a disease of pigs, called porcine reproductive and respiratory syndrome (PRRS), also known as blue-ear pig disease. This economically important, panzootic disease causes reproductive failure in breeding stock and respiratory tract illness in young pigs.

Porcine parvovirus (PPV), a virus in the species Ungulate protoparvovirus 1 of genus Protoparvovirus in the virus family Parvoviridae, causes reproductive failure of swine characterized by embryonic and fetal infection and death, usually in the absence of outward maternal clinical signs. The disease develops mainly when seronegative dams are exposed oronasally to the virus anytime during about the first half of gestation, and conceptuses are subsequently infected transplacentally before they become immunocompetent. There is no definitive evidence that infection of swine other than during gestation is of any clinical or economic significance. The virus is ubiquitous among swine throughout the world and is enzootic in most herds that have been tested. Diagnostic surveys have indicated that PPV is the major infectious cause of embryonic and fetal death. In addition to its direct causal role in reproductive failure, PPV can potentiate the effects of porcine circovirus type II (PCV2) infection in the clinical course of postweaning multisystemic wasting syndrome (PMWS). Approximately 38 peoples have died of the virus.

Bovine alphaherpesvirus 1 (BoHV-1) is a virus of the family Herpesviridae and the subfamily Alphaherpesvirinae, known to cause several diseases worldwide in cattle, including rhinotracheitis, vaginitis, balanoposthitis, abortion, conjunctivitis, and enteritis. BoHV-1 is also a contributing factor in shipping fever, also known as bovine respiratory disease (BRD). It is spread horizontally through sexual contact, artificial insemination, and aerosol transmission and it may also be transmitted vertically across the placenta. BoHV-1 can cause both clinical and subclinical infections, depending on the virulence of the strain. Although these symptoms are mainly non-life-threatening it is an economically important disease as infection may cause a drop in production and affect trade restrictions. Like other herpesviruses, BoHV-1 causes a lifelong latent infection and sporadic shedding of the virus. The sciatic nerve and trigeminal nerve are the sites of latency. A reactivated latent carrier is normally the source of infection in a herd. The clinical signs displayed are dependent on the virulence of the strain. There is a vaccine available which reduces the severity and incidence of disease. Some countries in Europe have successfully eradicated the disease by applying a strict culling policy.

<i>Feline calicivirus</i> Species of virus

Feline calicivirus (FCV) is a virus of the family Caliciviridae that causes disease in cats. It is one of the two important viral causes of respiratory infection in cats, the other being Felid alphaherpesvirus 1. FCV can be isolated from about 50% of cats with upper respiratory infections. Cheetahs are the other species of the family Felidae known to become infected naturally.

<i>African swine fever virus</i> Species of virus

African swine fever virus (ASFV) is a large, double-stranded DNA virus in the Asfarviridae family. It is the causative agent of African swine fever (ASF). The virus causes a hemorrhagic fever with high mortality rates in domestic pigs; some isolates can cause death of animals as quickly as a week after infection. It persistently infects its natural hosts, warthogs, bushpigs, and soft ticks of the genus Ornithodoros, which likely act as a vector, with no disease signs. It does not cause disease in humans. ASFV is endemic to sub-Saharan Africa and exists in the wild through a cycle of infection between ticks and wild pigs, bushpigs, and warthogs. The disease was first described after European settlers brought pigs into areas endemic with ASFV, and as such, is an example of an emerging infectious disease.

<span class="mw-page-title-main">Bovine malignant catarrhal fever</span> Species of virus

Bovine malignant catarrhal fever (BMCF) is a fatal lymphoproliferative disease caused by a group of ruminant gamma herpes viruses including Alcelaphine gammaherpesvirus 1 (AlHV-1) and Ovine gammaherpesvirus 2 (OvHV-2) These viruses cause unapparent infection in their reservoir hosts, but are usually fatal in cattle and other ungulates such as deer, antelope, and buffalo. In Southern Africa the disease is known as snotsiekte, from the Afrikaans.

<span class="mw-page-title-main">Bovine viral diarrhea</span> Significant economic disease of cattle caused by two species of Pestivirus

Bovine viral diarrhea (BVD), bovine viral diarrhoea or mucosal disease, previously referred to as bovine virus diarrhea (BVD), is an economically significant disease of cattle that is found in the majority of countries throughout the world. Worldwide reviews of the economically assessed production losses and intervention programs incurred by BVD infection have been published. The causative agent, bovine viral diarrhea virus (BVDV), is a member of the genus Pestivirus of the family Flaviviridae.

<i>Pasteurella multocida</i> Species of bacterium

Pasteurella multocida is a Gram-negative, nonmotile, penicillin-sensitive coccobacillus of the family Pasteurellaceae. Strains of the species are currently classified into five serogroups based on capsular composition and 16 somatic serovars (1–16). P. multocida is the cause of a range of diseases in mammals and birds, including fowl cholera in poultry, atrophic rhinitis in pigs, and bovine hemorrhagic septicemia in cattle and buffalo. It can also cause a zoonotic infection in humans, which typically is a result of bites or scratches from domestic pets. Many mammals and birds harbor it as part of their normal respiratory microbiota.

<span class="mw-page-title-main">Veterinary virology</span> Study of viruses affecting animals

Veterinary virology is the study of viruses in non-human animals. It is an important branch of veterinary medicine.

A marker vaccine is a vaccine which allows for immunological differentiation of infected from vaccinated animals, and is also referred to as a DIVA vaccine [Differentiation of infected from vaccinated animals] in veterinary medicine. In practical terms, this is most often achieved by omitting an immunogenic antigen present in the pathogen being vaccinated against, thus creating a negative marker of vaccination. In contrast, vaccination with traditional vaccines containing the complete pathogen, either attenuated or inactivated, precludes the use of serology in epidemiological surveys in vaccinated populations.

<span class="mw-page-title-main">Influenza</span> Infectious disease, often just "the flu"

Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin from one to four days after exposure to the virus and last for about 2–8 days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia, which can be caused by the virus or by a subsequent bacterial infection. Other complications of infection include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.

<span class="mw-page-title-main">Foot-and-mouth disease</span> Medical condition

Foot-and-mouth disease (FMD) or hoof-and-mouth disease (HMD) is an infectious and sometimes fatal viral disease that affects cloven-hoofed animals, including domestic and wild bovids. The virus causes a high fever lasting two to six days, followed by blisters inside the mouth and near the hoof that may rupture and cause lameness.

A serious outbreak of foot-and-mouth disease occurred in South Korea in 2010–2011, leading to the culling of hundreds of thousands of pigs in an effort to contain it. The outbreak began in November 2010 in pig farms in Andong, Gyeongsangbuk-do, and has since spread in the country rapidly. More than 100 cases of foot-and-mouth disease have been confirmed in the country so far, and South Korean officials have started a mass cull of approximately 12 percent of the entire domestic pig population and 107,000 of three million cattle of the country to halt the outbreak.

<i>Staphylococcus hyicus</i> Species of bacterium

Staphylococcus hyicus is a Gram-positive, facultatively anaerobic bacterium in the genus Staphylococcus. It consists of clustered cocci and forms white circular colonies when grown on blood agar. S. hyicus is a known animal pathogen. It causes disease in poultry, cattle, horses, and pigs. Most notably, it is the agent that causes porcine exudative epidermitis, also known as greasy pig disease, in piglets. S. hyicus is generally considered to not be zoonotic, however it has been shown to be able to cause bacteremia and sepsis in humans.

Actinobacillus pleuropneumoniae, is a Gram-negative, facultative anaerobic, respiratory pathogen found in pigs. It was first reported in 1957, and was formally declared to be the causative agent of porcine pleuropneumonia in 1964. It was reclassified in 1983 after DNA studies showed it was more closely related to A. lignieresii.

<i>Porcine epidemic diarrhea virus</i> Species of virus

Porcine epidemic diarrhea virus is a coronavirus that infects the cells lining the small intestine of a pig, causing porcine epidemic diarrhoea, a condition of severe diarrhea and dehydration. Older hogs mostly get sick and lose weight after being infected, whereas newborn piglets usually die within five days of contracting the virus. PEDV cannot be transmitted to humans, nor contaminate the human food supply.

<span class="mw-page-title-main">James E. Collins</span> American veterinary physician and academic

James E. Collins is an American veterinary physician and academic. He is the professor of medicine at the University of Minnesota and its Director of the veterinary diagnostic laboratory.

References

  1. "ICTV Taxonomy history: Suid alphaherpesvirus 1". International Committee on Taxonomy of Viruses (ICTV). Retrieved 9 January 2019.
  2. 1 2 Fenner, Frank J.; Gibbs, E. Paul J.; Murphy, Frederick A.; Rott, Rudolph; Studdert, Michael J.; White, David O. (1993). Veterinary Virology (2nd ed.). Academic Press, Inc. ISBN   978-0-12-253056-2.
  3. Mettenleiter (2008). "Molecular Biology of Animal Herpesviruses". Animal Viruses: Molecular Biology. Caister Academic Press. ISBN   978-1-904455-22-6.
  4. Sandri-Goldin, RM, ed. (2006). Alpha Herpesviruses: Molecular and Cellular Biology. Caister Academic Press. ISBN   978-1-904455-09-7.
  5. Pomeranz L, Reynolds A, Hengartner C (2005). "Molecular Biology of Pseudorabies Virus: Impact on Neurovirology and Veterinary Medicine". Microbiol Mol Biol Rev. 69 (3): 462–500. doi:10.1128/MMBR.69.3.462-500.2005. PMC   1197806 . PMID   16148307.
  6. 1 2 "Pseudorabies: Introduction". The Merck Veterinary Manual. 2006. Retrieved 2007-03-31.
  7. Pensaert M, Labarque G, Favoreel H, Nauwynck H (2004). "Aujeszky's disease vaccination and differentiation of vaccinated from infected pigs". Dev Biol (Basel). 119: 243–54. PMID   15742635.
  8. Amass, S.F. (2006). "Exotic Diseases: Are you Prepared? Are you Ready?". Proceedings of the North American Veterinary Conference. Retrieved 2007-03-31.
  9. Carter, G.R.; Flores, E.F.; Wise, D.J. (2006). "Herpesviridae" . A Concise Review of Veterinary Virology. Retrieved 2006-06-04.
  10. Bitsch, Viggo (2015). Principal Epidemiological Features of Aujeszky's Disease in Swine and Cattle . ISBN   978-87-994685-1-5.
  11. 1 2 3 4 Bitsch, Viggo (2015)
  12. Berryman Institute: Managing Wild Pigs Archived 2011-09-05 at the Wayback Machine
  13. Finnish Food Safety Authority Evira: Aujeszkyn tauti (AD, pseudorabies) Archived 2011-07-17 at the Wayback Machine  (in Finnish)
  14. "Merck Veterinary Manual".
  15. Bartha A (1961). "Experimental reduction of virulence of Aujesky's disease virus". Magyar Allatorvosok Lapja. 16: 42–45.
  16. Koyuncu OO, Perlman DH, Enquist LW (Jan 16, 2013). "Efficient retrograde transport of pseudorabies virus within neurons requires local protein synthesis in axons". Cell Host Microbe. 13 (1): 54–66. doi:10.1016/j.chom.2012.10.021. PMC   3552305 . PMID   23332155.
  17. Kratchmarov R, Taylor MP, Enquist LW (2013). "Role of us9 phosphorylation in axonal sorting and anterograde transport of pseudorabies virus". PLOS ONE. 8 (3): e58776. Bibcode:2013PLoSO...858776K. doi: 10.1371/journal.pone.0058776 . PMC   3602541 . PMID   23527020.