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Swedish University of Agricultural Sciences (2017)

Prevalence and risk factors for BVDV in goats and cattle in and around Gaborone, Botswana

Lysholm, Sara

Titre : Prevalence and risk factors for BVDV in goats and cattle in and around Gaborone, Botswana.

Auteur : Lysholm, Sara

Université de soutenance : Swedish University of Agricultural Sciences

Grade : Master Second cycle, A2E 2017

Résumé
Bovine Viral Diarrhoea Virus (BVDV) is a cause of severe deterioration in animal health as well as grave economic losses globally. Infection is often inapparent but the virus can also cause respiratory signs, diarrhoea, pyrexia, decreased production, immunosuppression and reproductive problems such as increased calving intervals and abortions. Also, when naive dams in early pregnancy are infected, before the development of fetal immune competence, the fetus is at risk of developing persistent infection. These persistently infected individuals (PI) are of particular epidemiologic interest since they shed virus in large concentrations in all their bodily secretions throughout their life. Risk factors for disease transmission include, but are not limited to, herd size, animal trade and grazing on communal pastures. For goats, contact with cattle is a significant risk factor. Several prevalence studies have been conducted on the African continent, but in the country of Botswana, the occurrence is largely unknown. Because of this, blood samples were obtained from 100 goats owned by 11 smallholder farmers, in three different villages just outside of Gaborone. Besides this, 361 blood samples from cattle collected as part of another study were analysed. The detected antibody prevalence was 0% in goats and 53.5% in cattle. In dairy cattle, the seroprevalence was 49.7% and in beef cattle 56.7%, but this difference was not statistically significant. The prevalence of virus in cattle was 0.27% on Ag-ELISA and PCR performed in Botswana, and 0.83% on PCR performed in Sweden. The viraemic animals all originated in the two herds with the highest prevalences (88.1% and 97.9% respectively). Finally, PCR analysis was performed and a short sequence of the genome of two of the detected viruses were sequenced, and found to belong to the BVDV-1a genotype. The goat farmers were also subjected to a short interview regarding risk factors for BVDV transmission, as well as the general health status in their herd. All farmers allowed their animals to graze on communal pastures, and 64% reported to also keep cattle in close proximity to their goats. Also, 18% answered that they keep sheep and goats together in the same kraal (i.e. enclosure) during the night. Approximately 55% responded that they occasionally saw wildlife ruminants in the area where their goats were kept. However, only 18% purchased goats from other farmers as the majority relied solely on raising their own kidlings. The most common health problem described was abortion, which 91% occasionally struggled with. Besides this, 64% also reported problems with diarrhoea, 36% with coughing and 18% with ocular and nasal discharge. Last but not least, all farmers stated that they depend on their goats for food and cash income and that it would affect them greatly if their animals would fall sick or die in large numbers.

Mots Clés  : BVDV, Bovine Viral Diarrhoea Virus, seroprevalence, risk factors, Botswana, goats, cattle, livestock

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