Evaluation of natural transmission of bovine leukaemia virus within dairy herds of Argentina.
Epidemiol Infect
; 135(2): 228-37, 2007 Feb.
Article
em En
| MEDLINE
| ID: mdl-16780609
The purpose of this study was to describe patterns of seroconversion to bovine leukaemia virus and to estimate the main parameters needed for future model building. A longitudinal study was carried out between February 1999 and November 2001 in seven commercial dairy farms in Argentina using 1535 lactating cows. Time-interval parameters were analysed using a parametric survival model with shared frailty, time until infection was analysed using a Bayesian interval-censoring survival model and the infection transmission parameter (beta) was estimated by a generalized linear model. The reproduction ratio (R0) was calculated. In total, 1000 cows tested positive and 494 tested negative. The predicted median age at infection was 4.6 years for seroconverted cows. For infected herds, the proportion of positive calves was as high as for infected cows and showed a large proportion of infected breeding heifers. Peaks in the overall average incidence per season-year were observed during autumn and spring. Results reveal that the period around parturition is a high-risk period. Moreover, heavily infected herds seem to have an increased proportion of young stock infected. The overall beta was estimated as 2.9/year (95% CI 1.9-3.7) and combined with a relatively long infectious period it resulted in a high reproductive ratio (R0=8.9). Therefore, a high effectiveness of control measures needs to be achieved to eradicate the disease.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Surtos de Doenças
/
Leucose Enzoótica Bovina
/
Transmissão de Doença Infecciosa
Tipo de estudo:
Observational_studies
/
Prognostic_studies
/
Risk_factors_studies
Limite:
Animals
País/Região como assunto:
America do sul
/
Argentina
Idioma:
En
Revista:
Epidemiol Infect
Assunto da revista:
DOENCAS TRANSMISSIVEIS
/
EPIDEMIOLOGIA
Ano de publicação:
2007
Tipo de documento:
Article
País de afiliação:
Holanda
País de publicação:
Reino Unido