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The persistence of African swine fever virus in field-infected Ornithodoros erraticus during the ASF endemic period in Portugal.

Boinas FS, Wilson AJ, Hutchings GH, Martins C, Dixon LJ - PLoS ONE (2011)

Bottom Line: African swine fever (ASF) is an important disease of pigs and outbreaks of ASF have occurred in Europe on multiple occasions.Experimental transmission to pigs was demonstrated in batches tested up to 380 days after an outbreak.These results clarify the epidemiological role of O. erraticus ticks in the persistence of ASFV in the field, provide additional evidence to support its role in the re-emergence of a sporadic outbreak of ASF in Portugal in 1999 and suggest that the current quarantine legislation and restocking advice when these ticks are present on the pig farm premises is appropriate.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigação Interdisciplinar em Medicina Veterinária, Faculdade de Medicina Veterinária da Universidade Técnica de Lisboa, Lisboa, Portugal. fboinas@fmv.utl.pt

ABSTRACT
African swine fever (ASF) is an important disease of pigs and outbreaks of ASF have occurred in Europe on multiple occasions. To explore the period for which the European soft tick species Ornithodoros erraticus (Acari: Argasidae) is able to act as a reservoir of African swine fever virus (ASFV) after infected hosts are removed, we collected specimens from farms in the provinces of Alentejo and Algarve in Portugal during the endemic period and tested them subsequently using cell culture and experimental infection. We show that ticks from previously infected farms may contain infectious virus for at least five years and three months after the removal of infectious hosts. Furthermore, in two cases infectious virus was successfully isolated from ticks on restocked farms that had not yet suffered a re-emergence of disease. Experimental transmission to pigs was demonstrated in batches tested up to 380 days after an outbreak. These results clarify the epidemiological role of O. erraticus ticks in the persistence of ASFV in the field, provide additional evidence to support its role in the re-emergence of a sporadic outbreak of ASF in Portugal in 1999 and suggest that the current quarantine legislation and restocking advice when these ticks are present on the pig farm premises is appropriate.

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O. erraticus collection sites and evidence of ASFV infection.
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pone-0020383-g001: O. erraticus collection sites and evidence of ASFV infection.

Mentions: All surviving O. erraticus (3,282 individuals) were tested for replicating ASFV using cell culture. ASFV was detected in four adult ticks via cell culture alone and from six adult ticks via a combination of cell culture and either DIF or PCR. Virus was detected in batches from three of the 34 farms on which collections were made (farms #103, #106 and #108), i.e. 8.8% of the tested farms. These farms were visited three, seven and 11 times respectively, over a period of nearly five years from 1988 to 1993. All three of these farms were in the province of Alentejo (Figure 1). The maximum period between the end of the ASFV outbreak on a farm and the successful isolation of ASFV from collected ticks by cell culture ranged from 937 to 1920 days (Table 1). ). All tick batches resulting in virus transmission to pigs were fully tested and isolation was achieved in two batches within 845/852 days after feeding while no isolation was achieved on batches tested 672 and 816 days after infecting pigs.


The persistence of African swine fever virus in field-infected Ornithodoros erraticus during the ASF endemic period in Portugal.

Boinas FS, Wilson AJ, Hutchings GH, Martins C, Dixon LJ - PLoS ONE (2011)

O. erraticus collection sites and evidence of ASFV infection.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105027&req=5

pone-0020383-g001: O. erraticus collection sites and evidence of ASFV infection.
Mentions: All surviving O. erraticus (3,282 individuals) were tested for replicating ASFV using cell culture. ASFV was detected in four adult ticks via cell culture alone and from six adult ticks via a combination of cell culture and either DIF or PCR. Virus was detected in batches from three of the 34 farms on which collections were made (farms #103, #106 and #108), i.e. 8.8% of the tested farms. These farms were visited three, seven and 11 times respectively, over a period of nearly five years from 1988 to 1993. All three of these farms were in the province of Alentejo (Figure 1). The maximum period between the end of the ASFV outbreak on a farm and the successful isolation of ASFV from collected ticks by cell culture ranged from 937 to 1920 days (Table 1). ). All tick batches resulting in virus transmission to pigs were fully tested and isolation was achieved in two batches within 845/852 days after feeding while no isolation was achieved on batches tested 672 and 816 days after infecting pigs.

Bottom Line: African swine fever (ASF) is an important disease of pigs and outbreaks of ASF have occurred in Europe on multiple occasions.Experimental transmission to pigs was demonstrated in batches tested up to 380 days after an outbreak.These results clarify the epidemiological role of O. erraticus ticks in the persistence of ASFV in the field, provide additional evidence to support its role in the re-emergence of a sporadic outbreak of ASF in Portugal in 1999 and suggest that the current quarantine legislation and restocking advice when these ticks are present on the pig farm premises is appropriate.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigação Interdisciplinar em Medicina Veterinária, Faculdade de Medicina Veterinária da Universidade Técnica de Lisboa, Lisboa, Portugal. fboinas@fmv.utl.pt

ABSTRACT
African swine fever (ASF) is an important disease of pigs and outbreaks of ASF have occurred in Europe on multiple occasions. To explore the period for which the European soft tick species Ornithodoros erraticus (Acari: Argasidae) is able to act as a reservoir of African swine fever virus (ASFV) after infected hosts are removed, we collected specimens from farms in the provinces of Alentejo and Algarve in Portugal during the endemic period and tested them subsequently using cell culture and experimental infection. We show that ticks from previously infected farms may contain infectious virus for at least five years and three months after the removal of infectious hosts. Furthermore, in two cases infectious virus was successfully isolated from ticks on restocked farms that had not yet suffered a re-emergence of disease. Experimental transmission to pigs was demonstrated in batches tested up to 380 days after an outbreak. These results clarify the epidemiological role of O. erraticus ticks in the persistence of ASFV in the field, provide additional evidence to support its role in the re-emergence of a sporadic outbreak of ASF in Portugal in 1999 and suggest that the current quarantine legislation and restocking advice when these ticks are present on the pig farm premises is appropriate.

Show MeSH
Related in: MedlinePlus