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Classical swine fever (CSF), caused by CSF virus (CSFV), is considered one of the most important infectious diseases with devasting consequences for the pig industry. Recent reports describe the emergence of new CSFV-strains resulting from the action of positive selection pressure, due mainly to the bottleneck effect generated by ineffective vaccination. Even though a decrease in the genetic diversity of the positive selected CSFV-strains has been observed by several research groups, there is little information about the effect of this selective force on the virulence degree, antigenicity and pathogenicity of this type of strains. Hence, the aim of the current study was to determine the effect of the positive selection pressure on these three parameters of CSFV-strains, emerged as result of the bottleneck effects induced by unproper vaccination in a CSF-endemic area. Moreover, the effect of the positive selected strains on the epidemiological surveillance system was assessed. By the combination of in vitro, in vivo and immunoinformatic approaches we revealed that the action of the positive selection pressure induces a decrease in virulence and alteration in pathogenicity and antigenicity. However, we also noted that the evolutionary process of CSFV, especially in segregated microenvironments, could contribute to the gain-fitness event, restoring the highly virulent pattern of the circulating strains. Besides, we denoted that the presence of low virulent strains selected by bottleneck effect after inefficient vaccination can lead to a relevant challenge for the epidemiological surveillance of CSF, contributing to under-reports of the disease, favoring the perpetuation of the virus in the field. In this study B-cell and CTL epitopes on the E2 3D-structure model were also identified. Thus, the current study provides novel and significant insights into variation in virulence, pathogenesis and antigenicity experienced by CSFV strains after the positive selection pressure

Background: Recent studies have hypothesized that circulation of classical swine fever virus (CSFV) variants when the immunity induced by the vaccine is not sterilizing might favour viral persistence. Likewise, in addition to congenital viral persistence, CSFV has also been proven to generate postnatal viral persistence. Under experimental conditions, postnatal persistently infected pigs were unable to elicit a specific immune response to a CSFV live attenuated vaccine via the mechanism known as superinfection exclusion (SIE). Here, we study whether subclinical forms of classical swine fever (CSF) may be present in a conventional farm in an endemic country and evaluate vaccine efficacy under these types of infections in field conditions. Results: Six litters born from CSF-vaccinated gilts were randomly chosen from a commercial Cuban farm at 33 days of age (weaning). At this time, the piglets were vaccinated with a lapinized live attenuated CSFV C-strain vaccine. Virological and immunological analyses were performed before and after vaccination. The piglets were clinically healthy at weaning; however, 82% were viraemic, and the rectal swabs in most of the remaining 18% were positive. Only five piglets from one litter showed a specific antibody response. The tonsils and rectal swabs of five sows were CSFV positive, and only one of the sows showed an antibody response. After vaccination, 98% of the piglets were unable to clear the virus and to seroconvert, and some of the piglets showed polyarthritis and wasting after 36 days post vaccination. The CSFV E2 glycoprotein sequences recovered from one pig per litter were the same. The amino acid positions 72(R), 20(L) and 195(N) of E2 were identified in silico as positions associated with adaptive advantage. Conclusions: Circulation of chronic and persistent CSF infections was demonstrated in field conditions under a vaccination programme. Persistent infection was predominant. Here, we provide evidence that, in field condit

Background: Recent studies have hypothesized that circulation of classical swine fever virus (CSFV) variants when the immunity induced by the vaccine is not sterilizing might favour viral persistence. Likewise, in addition to congenital viral persistence, CSFV has also been proven to generate postnatal viral persistence. Under experimental conditions, postnatal persistently infected pigs were unable to elicit a specific immune response to a CSFV live attenuated vaccine via the mechanism known as superinfection exclusion (SIE). Here, we study whether subclinical forms of classical swine fever (CSF) may be present in a conventional farm in an endemic country and evaluate vaccine efficacy under these types of infections in field conditions. Results: Six litters born from CSF-vaccinated gilts were randomly chosen from a commercial Cuban farm at 33 days of age (weaning). At this time, the piglets were vaccinated with a lapinized live attenuated CSFV C-strain vaccine. Virological and immunological analyses were performed before and after vaccination. The piglets were clinically healthy at weaning; however, 82% were viraemic, and the rectal swabs in most of the remaining 18% were positive. Only five piglets from one litter showed a specific antibody response. The tonsils and rectal swabs of five sows were CSFV positive, and only one of the sows showed an antibody response. After vaccination, 98% of the piglets were unable to clear the virus and to seroconvert, and some of the piglets showed polyarthritis and wasting after 36 days post vaccination. The CSFV E2 glycoprotein sequences recovered from one pig per litter were the same. The amino acid positions 72(R), 20(L) and 195(N) of E2 were identified in silico as positions associated with adaptive advantage. Conclusions: Circulation of chronic and persistent CSF infections was demonstrated in field conditions under a vaccination programme. Persistent infection was predominant. Here, we provide evidence that, in field condit

Background: Recent studies have hypothesized that circulation of classical swine fever virus (CSFV) variants when the immunity induced by the vaccine is not sterilizing might favour viral persistence. Likewise, in addition to congenital viral persistence, CSFV has also been proven to generate postnatal viral persistence. Under experimental conditions, postnatal persistently infected pigs were unable to elicit a specific immune response to a CSFV live attenuated vaccine via the mechanism known as superinfection exclusion (SIE). Here, we study whether subclinical forms of classical swine fever (CSF) may be present in a conventional farm in an endemic country and evaluate vaccine efficacy under these types of infections in field conditions. Results: Six litters born from CSF-vaccinated gilts were randomly chosen from a commercial Cuban farm at 33 days of age (weaning). At this time, the piglets were vaccinated with a lapinized live attenuated CSFV C-strain vaccine. Virological and immunological analyses were performed before and after vaccination. The piglets were clinically healthy at weaning; however, 82% were viraemic, and the rectal swabs in most of the remaining 18% were positive. Only five piglets from one litter showed a specific antibody response. The tonsils and rectal swabs of five sows were CSFV positive, and only one of the sows showed an antibody response. After vaccination, 98% of the piglets were unable to clear the virus and to seroconvert, and some of the piglets showed polyarthritis and wasting after 36 days post vaccination. The CSFV E2 glycoprotein sequences recovered from one pig per litter were the same. The amino acid positions 72(R), 20(L) and 195(N) of E2 were identified in silico as positions associated with adaptive advantage. Conclusions: Circulation of chronic and persistent CSF infections was demonstrated in field conditions under a vaccination programme. Persistent infection was predominant. Here, we provide evidence that, in field condit

Classical swine fever (CSF), caused by CSF virus (CSFV), is considered one of the most important infectious diseases with devasting consequences for the pig industry. Recent reports describe the emergence of new CSFV-strains resulting from the action of positive selection pressure, due mainly to the bottleneck effect generated by ineffective vaccination. Even though a decrease in the genetic diversity of the positive selected CSFV-strains has been observed by several research groups, there is little information about the effect of this selective force on the virulence degree, antigenicity and pathogenicity of this type of strains. Hence, the aim of the current study was to determine the effect of the positive selection pressure on these three parameters of CSFV-strains, emerged as result of the bottleneck effects induced by unproper vaccination in a CSF-endemic area. Moreover, the effect of the positive selected strains on the epidemiological surveillance system was assessed. By the combination of in vitro, in vivo and immunoinformatic approaches we revealed that the action of the positive selection pressure induces a decrease in virulence and alteration in pathogenicity and antigenicity. However, we also noted that the evolutionary process of CSFV, especially in segregated microenvironments, could contribute to the gain-fitness event, restoring the highly virulent pattern of the circulating strains. Besides, we denoted that the presence of low virulent strains selected by bottleneck effect after inefficient vaccination can lead to a relevant challenge for the epidemiological surveillance of CSF, contributing to under-reports of the disease, favoring the perpetuation of the virus in the field. In this study B-cell and CTL epitopes on the E2 3D-structure model were also identified. Thus, the current study provides novel and significant insights into variation in virulence, pathogenesis and antigenicity experienced by CSFV strains after the positive selection pressure

Background: Recent studies have hypothesized that circulation of classical swine fever virus (CSFV) variants when the immunity induced by the vaccine is not sterilizing might favour viral persistence. Likewise, in addition to congenital viral persistence, CSFV has also been proven to generate postnatal viral persistence. Under experimental conditions, postnatal persistently infected pigs were unable to elicit a specific immune response to a CSFV live attenuated vaccine via the mechanism known as superinfection exclusion (SIE). Here, we study whether subclinical forms of classical swine fever (CSF) may be present in a conventional farm in an endemic country and evaluate vaccine efficacy under these types of infections in field conditions. Results: Six litters born from CSF-vaccinated gilts were randomly chosen from a commercial Cuban farm at 33 days of age (weaning). At this time, the piglets were vaccinated with a lapinized live attenuated CSFV C-strain vaccine. Virological and immunological analyses were performed before and after vaccination. The piglets were clinically healthy at weaning; however, 82% were viraemic, and the rectal swabs in most of the remaining 18% were positive. Only five piglets from one litter showed a specific antibody response. The tonsils and rectal swabs of five sows were CSFV positive, and only one of the sows showed an antibody response. After vaccination, 98% of the piglets were unable to clear the virus and to seroconvert, and some of the piglets showed polyarthritis and wasting after 36 days post vaccination. The CSFV E2 glycoprotein sequences recovered from one pig per litter were the same. The amino acid positions 72(R), 20(L) and 195(N) of E2 were identified in silico as positions associated with adaptive advantage. Conclusions: Circulation of chronic and persistent CSF infections was demonstrated in field conditions under a vaccination programme. Persistent infection was predominant. Here, we provide evidence that, in field condit

Background: Recent studies have hypothesized that circulation of classical swine fever virus (CSFV) variants when the immunity induced by the vaccine is not sterilizing might favour viral persistence. Likewise, in addition to congenital viral persistence, CSFV has also been proven to generate postnatal viral persistence. Under experimental conditions, postnatal persistently infected pigs were unable to elicit a specific immune response to a CSFV live attenuated vaccine via the mechanism known as superinfection exclusion (SIE). Here, we study whether subclinical forms of classical swine fever (CSF) may be present in a conventional farm in an endemic country and evaluate vaccine efficacy under these types of infections in field conditions. Results: Six litters born from CSF-vaccinated gilts were randomly chosen from a commercial Cuban farm at 33 days of age (weaning). At this time, the piglets were vaccinated with a lapinized live attenuated CSFV C-strain vaccine. Virological and immunological analyses were performed before and after vaccination. The piglets were clinically healthy at weaning; however, 82% were viraemic, and the rectal swabs in most of the remaining 18% were positive. Only five piglets from one litter showed a specific antibody response. The tonsils and rectal swabs of five sows were CSFV positive, and only one of the sows showed an antibody response. After vaccination, 98% of the piglets were unable to clear the virus and to seroconvert, and some of the piglets showed polyarthritis and wasting after 36 days post vaccination. The CSFV E2 glycoprotein sequences recovered from one pig per litter were the same. The amino acid positions 72(R), 20(L) and 195(N) of E2 were identified in silico as positions associated with adaptive advantage. Conclusions: Circulation of chronic and persistent CSF infections was demonstrated in field conditions under a vaccination programme. Persistent infection was predominant. Here, we provide evidence that, in field condit

Background: Recent studies have hypothesized that circulation of classical swine fever virus (CSFV) variants when the immunity induced by the vaccine is not sterilizing might favour viral persistence. Likewise, in addition to congenital viral persistence, CSFV has also been proven to generate postnatal viral persistence. Under experimental conditions, postnatal persistently infected pigs were unable to elicit a specific immune response to a CSFV live attenuated vaccine via the mechanism known as superinfection exclusion (SIE). Here, we study whether subclinical forms of classical swine fever (CSF) may be present in a conventional farm in an endemic country and evaluate vaccine efficacy under these types of infections in field conditions. Results: Six litters born from CSF-vaccinated gilts were randomly chosen from a commercial Cuban farm at 33 days of age (weaning). At this time, the piglets were vaccinated with a lapinized live attenuated CSFV C-strain vaccine. Virological and immunological analyses were performed before and after vaccination. The piglets were clinically healthy at weaning; however, 82% were viraemic, and the rectal swabs in most of the remaining 18% were positive. Only five piglets from one litter showed a specific antibody response. The tonsils and rectal swabs of five sows were CSFV positive, and only one of the sows showed an antibody response. After vaccination, 98% of the piglets were unable to clear the virus and to seroconvert, and some of the piglets showed polyarthritis and wasting after 36 days post vaccination. The CSFV E2 glycoprotein sequences recovered from one pig per litter were the same. The amino acid positions 72(R), 20(L) and 195(N) of E2 were identified in silico as positions associated with adaptive advantage. Conclusions: Circulation of chronic and persistent CSF infections was demonstrated in field conditions under a vaccination programme. Persistent infection was predominant. Here, we provide evidence that, in field condit

In Cuba, Classical Swine Fever (CSF) has become an endemic disease since 1993 with several outbreaks each year despite the compulsory vaccination program implemented. To deepen the disease characterization is essential for improving the CSF control measures and to achieve its eradication. The aim of this study was to describe the epidemiological characteristics of CSF occurrences in Cuba during a seven-year period within the endemic situation. Data on CSF occurrence from January 2010 to December 2016 were analyzed. The seven-year period shows a tendency of the number of affected premises to increase (r=0.31, p=0.005) over time (month). Directional distribution (1SD ellipse) indicated a great dispersion of affected premises by year across the country with a trend to a higher occurrence to the west. It was demonstrated by the negative correlation (r=-0.893, p=0.007) between the longitude of the mean center of the ellipses over the years. The Kernel density indicated that the disease was spatially distributed across the whole country, but four hot spots were found in the western (Pinar del Río and Artemisa) and eastern (Guantánamo and Holguín) regions. The clinical sign most frequently reported in affected premises was fever, followed by loss of appetite, conjunctivitis, and diarrhea. The most frequent observed clinical signs were non-specific, which complicates the disease recognition in the field. The obtained results have a practical importance for improving the efficiency of the CSF control program implemented in the country and contribute to enhance epidemiological surveillance taking into account the risk based principles.

In Cuba, Classical Swine Fever (CSF) has become an endemic disease since 1993 with several outbreaks each year despite the compulsory vaccination program implemented. To deepen the disease characterization is essential for improving the CSF control measures and to achieve its eradication. The aim of this study was to describe the epidemiological characteristics of CSF occurrences in Cuba during a seven-year period within the endemic situation. Data on CSF occurrence from January 2010 to December 2016 were analyzed. The seven-year period shows a tendency of the number of affected premises to increase (r=0.31, p=0.005) over time (month). Directional distribution (1SD ellipse) indicated a great dispersion of affected premises by year across the country with a trend to a higher occurrence to the west. It was demonstrated by the negative correlation (r=-0.893, p=0.007) between the longitude of the mean center of the ellipses over the years. The Kernel density indicated that the disease was spatially distributed across the whole country, but four hot spots were found in the western (Pinar del Río and Artemisa) and eastern (Guantánamo and Holguín) regions. The clinical sign most frequently reported in affected premises was fever, followed by loss of appetite, conjunctivitis, and diarrhea. The most frequent observed clinical signs were non-specific, which complicates the disease recognition in the field. The obtained results have a practical importance for improving the efficiency of the CSF control program implemented in the country and contribute to enhance epidemiological surveillance taking into account the risk based principles.

In Cuba, Classical Swine Fever (CSF) has become an endemic disease since 1993 with several outbreaks each year despite the compulsory vaccination program implemented. To deepen the disease characterization is essential for improving the CSF control measures and to achieve its eradication. The aim of this study was to describe the epidemiological characteristics of CSF occurrences in Cuba during a seven-year period within the endemic situation. Data on CSF occurrence from January 2010 to December 2016 were analyzed. The seven-year period shows a tendency of the number of affected premises to increase (r=0.31, p=0.005) over time (month). Directional distribution (1SD ellipse) indicated a great dispersion of affected premises by year across the country with a trend to a higher occurrence to the west. It was demonstrated by the negative correlation (r=-0.893, p=0.007) between the longitude of the mean center of the ellipses over the years. The Kernel density indicated that the disease was spatially distributed across the whole country, but four hot spots were found in the western (Pinar del Río and Artemisa) and eastern (Guantánamo and Holguín) regions. The clinical sign most frequently reported in affected premises was fever, followed by loss of appetite, conjunctivitis, and diarrhea. The most frequent observed clinical signs were non-specific, which complicates the disease recognition in the field. The obtained results have a practical importance for improving the efficiency of the CSF control program implemented in the country and contribute to enhance epidemiological surveillance taking into account the risk based principles.

In Cuba, Classical Swine Fever (CSF) has become an endemic disease since 1993 with several outbreaks each year despite the compulsory vaccination program implemented. To deepen the disease characterization is essential for improving the CSF control measures and to achieve its eradication. The aim of this study was to describe the epidemiological characteristics of CSF occurrences in Cuba during a seven-year period within the endemic situation. Data on CSF occurrence from January 2010 to December 2016 were analyzed. The seven-year period shows a tendency of the number of affected premises to increase (r=0.31, p=0.005) over time (month). Directional distribution (1SD ellipse) indicated a great dispersion of affected premises by year across the country with a trend to a higher occurrence to the west. It was demonstrated by the negative correlation (r=-0.893, p=0.007) between the longitude of the mean center of the ellipses over the years. The Kernel density indicated that the disease was spatially distributed across the whole country, but four hot spots were found in the western (Pinar del Río and Artemisa) and eastern (Guantánamo and Holguín) regions. The clinical sign most frequently reported in affected premises was fever, followed by loss of appetite, conjunctivitis, and diarrhea. The most frequent observed clinical signs were non-specific, which complicates the disease recognition in the field. The obtained results have a practical importance for improving the efficiency of the CSF control program implemented in the country and contribute to enhance epidemiological surveillance taking into account the risk based principles.

In Cuba, Classical Swine Fever (CSF) has become an endemic disease since 1993 with several outbreaks each year despite the compulsory vaccination program implemented. To deepen the disease characterization is essential for improving the CSF control measures and to achieve its eradication. The aim of this study was to describe the epidemiological characteristics of CSF occurrences in Cuba during a seven-year period within the endemic situation. Data on CSF occurrence from January 2010 to December 2016 were analyzed. The seven-year period shows a tendency of the number of affected premises to increase (r=0.31, p=0.005) over time (month). Directional distribution (1SD ellipse) indicated a great dispersion of affected premises by year across the country with a trend to a higher occurrence to the west. It was demonstrated by the negative correlation (r=-0.893, p=0.007) between the longitude of the mean center of the ellipses over the years. The Kernel density indicated that the disease was spatially distributed across the whole country, but four hot spots were found in the western (Pinar del Río and Artemisa) and eastern (Guantánamo and Holguín) regions. The clinical sign most frequently reported in affected premises was fever, followed by loss of appetite, conjunctivitis, and diarrhea. The most frequent observed clinical signs were non-specific, which complicates the disease recognition in the field. The obtained results have a practical importance for improving the efficiency of the CSF control program implemented in the country and contribute to enhance epidemiological surveillance taking into account the risk based principles.