Herd-level seroprevalence of fasciolosis in cattle in north central Portugal.

An epidemiological study of Fasciola hepatica in cattle was implemented in the north central region of Portugal. Both an enzyme-linked immunosorbent assay and an egg shedding quantification technique were used in the follow-up of seven herds. Two of these herds were negative and the other five were positive for F. hepatica. A herd cut-off of value of 0.425 optical density was calculated and herd sensitivity (HSe) and herd specificity (HSp) were defined. Three seroprevalence studies were also implemented in the region with stratification by county sub-regions for a period of 18 months. Overall mean herd prevalence in Vagos of 11, 23 and 48% was progressively found for the three studies, respectively.

The use of carbon dioxide insect traps for the collection of Ornithodoros erraticus on African swine fever-infected farms.

The establishment of epidemiological studies of African swine fever involves the collection of large numbers of the soft tick, Ornithodoros erraticus, to assess the maintenance and spread of the disease in the semi-arid southern areas of Portugal. An on-farm monitoring system involving solid carbon dioxide trapping of ticks was used. This capture method proved to be both simple and effective when compared with manual collection. Both adult and stadial ticks were attracted by the traps making this method suitable for epidemiological surveillance studies of any disease which involves the Ornithodoros as a vector.

An electron microscopic study of MDBK cells persistently infected with Newcastle disease virus.

Ultrastructural examination of a line of MDBK cells persistently infected with Newcastle disease virus (MDBKpi cells) revealed the presence of cytoplasmic aggregates of both smooth and granular nucleocapsids. Only granular nucleocapsids aligned under modified areas of plasma membrane and were incorporated into virus particles. On the grounds of morphogenesis, there was no apparent explanation for the persistent, not-cytocidal nature of the infection. Both nuclear and cytoplasmic aggregates of smooth nucleocapsids were present in MDBKpi cells which had been held without subculture for between 40 and 130 days (aged MDBKpi cells). Modified areas of plasma membrane with associated alignment of nucleocapsids were not present in aged MDBKpi cells, and neither budding nor released virus particles were observed, indicating a block in virus maturation. It is suggested that the granular material coating granular nucleocapsids allows them to interact with modified areas of plasma membrane, thereby inducing virus budding. A deficiency of this material, as apparently occurs in aged MDBKpi cells, would therefore cause a block in virus maturation. The nature of this granular material is discussed, and we suggest that it consists of M protein.