Pseudorabies: Is your mini pig at risk?
Pseudorabies (PRV) is a major viral disease manifested in swine by signs and lesions that vary among different age groups.
NOT TO BE CONFUSED WITH RABIES. These are two separate and completely different diseases. Never "vaccinate" your pig for pseudorabies, when blood work is needed and a pseudorabies test is done, your pig will test positive and that can lead to your pig being quarantined or euthanized in some states.
The disease is characterized by three overlapping syndromes that reflect lesions in the central nervous system (CNS), respiratory system or reproductive system. There are several states that have been deemed pseudorabies free and they require negative blood test results be included with the health certificate (CVI or health certificates discussed in another section) in order to bring a pig in a state that has eradicated pseudorabies. Pseudorabies is an acute, frequently fatal disease with a worldwide distribution that affects swine primarily and other domestic and wild animals incidentally. The pseudorabies virus has emerged as a significant pathogen in the USA since the 1960s, probably because of the increase in confinement swine housing or perhaps because of the emergence of more virulent strains. Clinical signs in nonporcine animals are similar to those of rabies, hence the name “mad itch” (pigs do not display this sign). Pseudorabies is a reportable disease and has been successfully eradicated from the vast majority of the USA. Reportable means the USDA will be notified if there is a suspected case and will also run their own investigation. This is one of the reasons why CVI (certificate of veterinarian inspection) or health certificates need to be in place prior to transporting of pigs across state lines. Many US states have been deemed "pseudorabies free" and this is just one of the reasons why they require blood testing upon entry to the states that require it.
Among domestic animals, swine are the only natural host of pseudorabies virus (PRV). All age groups not previously exposed or vaccinated are susceptible. The disease was eradicated from the US commercial pig industry in 2004 but remains in some localized feral swine populations. The disease remains common in many other major swine-raising countries. Most domestic animals (cattle, sheep, dogs, cats, and goats but not horses) and many wild animals (rats, mice, raccoons, opossums, rabbits, and several fur-bearing mammals) are susceptible to the virus but transmission only occurs when these species are kept in close contact with acutely infected swine; death is the usual outcome in these aberrant hosts. Pseudorabies occurs with some frequency in both cattle and sheep, especially those in close contact with swine. There is no evidence that PRV is a health threat to humans.
Pseudorabies virus (PRV) is a DNA herpesvirus. Isolates vary in virulence and pathogenicity. Like many other herpesviruses, PRV often persists in a latent state in recovered animals. The virus is only moderately resistant outside the host, survival depending largely on environmental factors. Except during cold weather, virus probably does not survive more than two weeks outside the pig. Under exceptional conditions it may survive longer in infected fetuses, dried tissue, and buildings
Pseudorabies virus is spread and persists by several mechanisms. Swine that recover from PRV excrete large amounts of virus in saliva and nasal secretions, and perhaps in urine and feces, for up to two weeks. Virus can persist in the tonsils of carrier swine for at least several weeks. Latent virus can persist in the CNS for many months. Recrudescence and shedding of virus often occur after stress. Inapparent shedders frequently are the means of introduction of virus into susceptible herds. Once introduced, the virus spreads by nose-to-nose contact, through feed and water contaminated by oral secretions and by aerosols coughed into the air. Circumstantial evidence suggests that an infectious aerosol can spread several miles. In a farrowing house, aborted fetuses or infected piglets born alive or incubating the disease soon contaminate the house. Virus may survive long enough to infect piglets of the next farrowing. Feral swine remain a possible source of infection to domestic swine. Other PRV-infected animals (e.g. rats, mice, dogs, cats, raccoons, opossums) are considered “dead-end” hosts and will shed PRV only a short time. They may, however, visit swine facilities and either shed virus that contaminates the facility or they may die and be eaten by swine. The possible role of flies or birds in transmission is dubious.
Clinical signs vary, depending largely on the immune status of the dam and the age of the pigs affected. But typically, the gross lesions are undectable. In general, younger pigs are more severely affected but become more resistant as they age. Neonatal pigs born to naïve sows are highly susceptible to infection and piglets become ill two to four days after exposure. Very young neonates may die without signs even having been noticed. Nursing pigs usually show signs of neurologic involvement. Signs may include high fever, depression, anorexia, tremors, incoordination, dog-sitting position, vomiting, foaming at the mouth, blindness, paddling, coma and convulsions. Death often occurs within one to three days. Morbidity and mortality may approach 100% in neonates, especially in naïve herds. Piglets nursing recovered or vaccinated dams are well protected from clinical signs and infection with the virus. Weaned pigs (three to nine weeks of age) have similar signs but mortality is usually much lower. Respiratory signs often occur in the older pigs of this age group. They include sneezing, nasal discharge, sometimes coughing and labored breathing. Most of the pigs survive, provided they do not succumb to secondary infections, especially bacterial pneumonia. In susceptible, grow/finish swine (ten weeks of age to market weight), respiratory signs predominate and morbidity is high. Signs include a febrile response, depression, anorexia, sneezing, coughing and nasal discharge. CNS signs occur in occasional pigs and vary in severity from tremors to convulsions. Most pigs recover in about seven to ten days. In breeding herds, clinical signs may not be apparent except during the period of initial infection. These signs are primarily respiratory and most animals will recover. In pregnant sows or gilts, reproductive failure sometimes occurs. Dams infected in the first trimester may absorb their fetuses and return to estrus. Those in the second or third trimester may abort or have mummified, stillborn or weak pigs. Those infected close to term may deliver infected piglets that die within a few days. Reproductive failure usually has a modest incidence of < 20%.
Diagnosis often can be made on the basis of prevalence of the disease in the area, history, signs, gross and microscopic lesions or serologic testing. Serologic tests available include serum neutralization (SN), latex agglutination (LA), and enzyme-linked immunosorbent assay (ELISA). SN is the standard regulatory test but the LA and ELISA tests are widely used as screening tests. Serologic testing is widely used for herd diagnosis. Accurate serologic tests that can differentiate vaccination antibody from wild type are widely available and are commonly used as part of national disease control programs.
There are a lot of states deemed "pseudorabies free" and those are the states that require a negative blood test listed on the CVI or health inspection to be sure no pigs are entering the state that haven't been tested for this prior to them coming into the state.
I pulled one state code to highlight the importance of this disease to the USDA and the consequences after a positive diagnosis is made,
http://codes.ohio.gov/oac/901%3A1-11
This is a link from the USDA discussing the diseases that they find most threatening that are reportable to that agency
http://www.aphis.usda.gov/wps/wcm/connect/APHIS_Content_Library/SA_Our_Focus/SA_Animal_Health/SA_Animal_Disease_Information/SA_Swine_Health
And finally, a USDA link regarding the feral pig population and the dangers associated with them
http://www.aphis.usda.gov/publications/wildlife_damage/content/printable_version/feral%20pigs.pdf
Sources:
Merckmanuals.com, Thepigsite.com, 9site.org, Diseases of Swine 10th edition
NOT TO BE CONFUSED WITH RABIES. These are two separate and completely different diseases. Never "vaccinate" your pig for pseudorabies, when blood work is needed and a pseudorabies test is done, your pig will test positive and that can lead to your pig being quarantined or euthanized in some states.
The disease is characterized by three overlapping syndromes that reflect lesions in the central nervous system (CNS), respiratory system or reproductive system. There are several states that have been deemed pseudorabies free and they require negative blood test results be included with the health certificate (CVI or health certificates discussed in another section) in order to bring a pig in a state that has eradicated pseudorabies. Pseudorabies is an acute, frequently fatal disease with a worldwide distribution that affects swine primarily and other domestic and wild animals incidentally. The pseudorabies virus has emerged as a significant pathogen in the USA since the 1960s, probably because of the increase in confinement swine housing or perhaps because of the emergence of more virulent strains. Clinical signs in nonporcine animals are similar to those of rabies, hence the name “mad itch” (pigs do not display this sign). Pseudorabies is a reportable disease and has been successfully eradicated from the vast majority of the USA. Reportable means the USDA will be notified if there is a suspected case and will also run their own investigation. This is one of the reasons why CVI (certificate of veterinarian inspection) or health certificates need to be in place prior to transporting of pigs across state lines. Many US states have been deemed "pseudorabies free" and this is just one of the reasons why they require blood testing upon entry to the states that require it.
Among domestic animals, swine are the only natural host of pseudorabies virus (PRV). All age groups not previously exposed or vaccinated are susceptible. The disease was eradicated from the US commercial pig industry in 2004 but remains in some localized feral swine populations. The disease remains common in many other major swine-raising countries. Most domestic animals (cattle, sheep, dogs, cats, and goats but not horses) and many wild animals (rats, mice, raccoons, opossums, rabbits, and several fur-bearing mammals) are susceptible to the virus but transmission only occurs when these species are kept in close contact with acutely infected swine; death is the usual outcome in these aberrant hosts. Pseudorabies occurs with some frequency in both cattle and sheep, especially those in close contact with swine. There is no evidence that PRV is a health threat to humans.
Pseudorabies virus (PRV) is a DNA herpesvirus. Isolates vary in virulence and pathogenicity. Like many other herpesviruses, PRV often persists in a latent state in recovered animals. The virus is only moderately resistant outside the host, survival depending largely on environmental factors. Except during cold weather, virus probably does not survive more than two weeks outside the pig. Under exceptional conditions it may survive longer in infected fetuses, dried tissue, and buildings
Pseudorabies virus is spread and persists by several mechanisms. Swine that recover from PRV excrete large amounts of virus in saliva and nasal secretions, and perhaps in urine and feces, for up to two weeks. Virus can persist in the tonsils of carrier swine for at least several weeks. Latent virus can persist in the CNS for many months. Recrudescence and shedding of virus often occur after stress. Inapparent shedders frequently are the means of introduction of virus into susceptible herds. Once introduced, the virus spreads by nose-to-nose contact, through feed and water contaminated by oral secretions and by aerosols coughed into the air. Circumstantial evidence suggests that an infectious aerosol can spread several miles. In a farrowing house, aborted fetuses or infected piglets born alive or incubating the disease soon contaminate the house. Virus may survive long enough to infect piglets of the next farrowing. Feral swine remain a possible source of infection to domestic swine. Other PRV-infected animals (e.g. rats, mice, dogs, cats, raccoons, opossums) are considered “dead-end” hosts and will shed PRV only a short time. They may, however, visit swine facilities and either shed virus that contaminates the facility or they may die and be eaten by swine. The possible role of flies or birds in transmission is dubious.
Clinical signs vary, depending largely on the immune status of the dam and the age of the pigs affected. But typically, the gross lesions are undectable. In general, younger pigs are more severely affected but become more resistant as they age. Neonatal pigs born to naïve sows are highly susceptible to infection and piglets become ill two to four days after exposure. Very young neonates may die without signs even having been noticed. Nursing pigs usually show signs of neurologic involvement. Signs may include high fever, depression, anorexia, tremors, incoordination, dog-sitting position, vomiting, foaming at the mouth, blindness, paddling, coma and convulsions. Death often occurs within one to three days. Morbidity and mortality may approach 100% in neonates, especially in naïve herds. Piglets nursing recovered or vaccinated dams are well protected from clinical signs and infection with the virus. Weaned pigs (three to nine weeks of age) have similar signs but mortality is usually much lower. Respiratory signs often occur in the older pigs of this age group. They include sneezing, nasal discharge, sometimes coughing and labored breathing. Most of the pigs survive, provided they do not succumb to secondary infections, especially bacterial pneumonia. In susceptible, grow/finish swine (ten weeks of age to market weight), respiratory signs predominate and morbidity is high. Signs include a febrile response, depression, anorexia, sneezing, coughing and nasal discharge. CNS signs occur in occasional pigs and vary in severity from tremors to convulsions. Most pigs recover in about seven to ten days. In breeding herds, clinical signs may not be apparent except during the period of initial infection. These signs are primarily respiratory and most animals will recover. In pregnant sows or gilts, reproductive failure sometimes occurs. Dams infected in the first trimester may absorb their fetuses and return to estrus. Those in the second or third trimester may abort or have mummified, stillborn or weak pigs. Those infected close to term may deliver infected piglets that die within a few days. Reproductive failure usually has a modest incidence of < 20%.
Diagnosis often can be made on the basis of prevalence of the disease in the area, history, signs, gross and microscopic lesions or serologic testing. Serologic tests available include serum neutralization (SN), latex agglutination (LA), and enzyme-linked immunosorbent assay (ELISA). SN is the standard regulatory test but the LA and ELISA tests are widely used as screening tests. Serologic testing is widely used for herd diagnosis. Accurate serologic tests that can differentiate vaccination antibody from wild type are widely available and are commonly used as part of national disease control programs.
There are a lot of states deemed "pseudorabies free" and those are the states that require a negative blood test listed on the CVI or health inspection to be sure no pigs are entering the state that haven't been tested for this prior to them coming into the state.
I pulled one state code to highlight the importance of this disease to the USDA and the consequences after a positive diagnosis is made,
http://codes.ohio.gov/oac/901%3A1-11
This is a link from the USDA discussing the diseases that they find most threatening that are reportable to that agency
http://www.aphis.usda.gov/wps/wcm/connect/APHIS_Content_Library/SA_Our_Focus/SA_Animal_Health/SA_Animal_Disease_Information/SA_Swine_Health
And finally, a USDA link regarding the feral pig population and the dangers associated with them
http://www.aphis.usda.gov/publications/wildlife_damage/content/printable_version/feral%20pigs.pdf
Sources:
Merckmanuals.com, Thepigsite.com, 9site.org, Diseases of Swine 10th edition