Epidemiological aspects of border disease virus infection in Pyrenean chamois (Rupicapra p. pyrenaica): influence of the viral strain, non-artiodactyl hosts and sheep transhumance /
- Autores: Andreu Colom Cadena
- Directores de la Tesis: Ignasi Marco Sánchez (dir. tes.), Oscar Cabezón Ponsoda (codir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2017
- Idioma: español
- Tribunal Calificador de la Tesis: Joaquim Segalés Coma (presid.), Joan Pujols Romeu (secret.), Emmanuelle Gilot Fromont (voc.)
- Programa de doctorado: Programa de Doctorado en Medicina y Sanidad Animales por la Universidad Autónoma de Barcelona
- Materias:
- Enlaces
- Resumen
Pestiviruses (Family Flaviviridae) cause diseases with important economic and health impact on livestock. One of these pestivirus species, the Border Disease Virus (BDV) is also of importance in wildlife conservation since 2001 when it was associated with high mortality outbreaks in Pyrenean chamois (Rupicapra pyrenaica pyrenaica). After 16 years of research, different epidemiological scenarios of BDV infection in chamois populations have been described. The main objective of the present thesis was to analyse the role of three factors that may explain this epidemiological diversity: viral strains, sympatric wild non-artiodactyl hosts and sheep transhumance.
Study I was designed to confirm the presence of BDV strains of a high and low virulence in free-ranging chamois populations from Pyrenees and to understand the implications of these findings to the diverse epidemiological scenarios. An experimental infection of Pyrenean chamois with a high-virulence (Cadí-6) and low-virulence (Freser-5) BDV strains was performed. Pregnant and non-pregnant animals with and without antibodies were included in each group. Cadí-6 BDV strain was confirmed to be of high virulence for adults and foetuses. Three chamois died before the end of the experiment with haemorrhagic diathesis. All but one antibody negative animals presented long viraemia, high nasal and rectal viral shedding and wide viral distribution in tissues. Foetuses infected with Cadí-6 died before the end of the experiment presenting high viral RNA loads. The antibody negative chamois infected with Freser-5 BDV strain presented less viral distribution and RNA load in tissues than Cadí-6 group, and cleared the virus from the serum. However, foetuses died before the end of the experiment and RNA virus was detected in sera and tissues although with lower RNA load than the Cadí-6 group. Chamois from both groups presented lesions in brain but the ones infected with the low-virulence Freser-5 BDV strain were mild and most likely transient. In both groups, in pregnant females with antibodies and all but one of their foetuses did not present viraemia or viral RNA in tissues. These results demonstrate that viral strains diversity is a significant factor in the heterogeneity of epidemiological scenarios in Pyrenean chamois populations.
Since free-ranging common rabbit (Oryctolagus cuniculus) and Bennett’s wallaby (Macropus rufogriseus) were found susceptible to pestivirus infections, chamois sympatric non-artiodactyl species became of interest as potential hosts in pestivirus epidemiology. Study II focused on the susceptibility to pestivirus infection of two of these species: European hare (Lepus europaeus) and Alpine marmot (Marmota marmota). None of the marmots presented pestivirus and antibodies in the analyzed sera samples. Although no pestivirus was detected, 36.2% of hares had neutralizing antibodies. Thus, the European hare is the third wild non-artiodactyl with documented susceptibility to pestivirus infection.
The anthropogenic influence in the diversity of epidemiological scenarios in chamois BDV infection was assessed in Study III and focused on transhumant sheep flocks. Five sheep flocks grazing in two alpine areas in the Pyrenees with two different BDV epidemiological scenarios in chamois populations were studied. Sheep were sampled before and after transhumance. Only one farm presented persistent BDV circulation in the flock. In that farm, joining feed lots in alpine meadows was demonstrated as the main factor for viral transmission. Moreover, the titration of neutralizing antibodies in that farm showed that most of the infections may be the result of contact with BDV strains of domestic origin. The only BDV sequenced (5’UTR region) in this farm was found genetically close related to previous BDV strains from chamois origin. This fact, together with the evidence that in another studied farm sheep antibodies seems to be originated by a chamois-like BDV strain, indicate that occasional transmission between sheep and chamois occurs.
