Tesis doctoral de Nilsa Olivia Razao De Deus
The purpose of this thesis was to study different aspects of the hepatitis e virus (hev) natural infection in domestic swine and wild boar, with emphasis on epidemiology and pathogenesis of this viral infection. To achieve these objectives, three studies were performed. In the first study, hev was detected by rt-pcr in serum, bile, liver, mesenteric lymph nodes and/or faeces in 26 out of 69 (37.7%) pigs from 1 to 3 months of age, which were affected by different pathological conditions. Hev detection rate was increased by processing samples that cannot be obtained from live animals, such as bile, which was the most frequently positive sample followed by mesenteric lymph nodes, liver, faeces and serum. More than 50% of the positive pigs in at least one of the tested samples had mild to moderate hepatitis. Hepatitis was related to hev detection in bile and mesenteric lymph nodes. the study of hev infection dynamics in an enzootically infected farm revealed a seroconversion pattern for hev equivalent to that of most viral agents that infect pigs. Igg and iga maternal derived antibodies in the piglets lasted until 9 and 3 weeks of age, respectively. Once maternal antibodies disappeared, animals seroconverted. The seroconversion was characterized by iga and igm appearance at 12 weeks and igg at 15 weeks of age. On individual basis, iga and igm duration varied between 4 to 7 weeks, while igg was detected until the end of the study. Hev rna was detected in serum samples in pigs from 1 to 22 weeks of age, with the highest prevalence at 15 weeks of age. Apart from piglets, hev was also present in serum from the sows, which suggest that the last ones might be source of infection for the first ones. Hev was detected in faeces and lymph nodes for the first time at 9 weeks of age and peaked at 12 and 15 weeks of age. This peak coincided with the occurrence of hepatitis as well as with hev detection in bile, liver, mesenteric lymph nodes and faeces, and also with the highest igg and igm od values at 15 weeks. The genetic characterization of hev detected sequences showed that different strains can circulate in the same farm and that one pig can be infected by different hev strains during its productive life. in the third study, hev prevalence was assessed in a population of 150 wild boars from different ages and affected by different management systems which allow speculating about the hev infection dynamics in this specie. Results obtained showed that more than 40% of the animals were seropositive to hev and 20% positive by rt-pcr. Furthermore, it was observed that wild boars under intensive management and juvenile animals were more frequently viraemics. The pattern of hev infection here described in the wild boars is, apparently, similar to that observed in domestic swine. In general, non-adult wild boars (juveniles plus sub-adults) had a higher probability to get infected by hev than adults, as occurs with domestic pigs. Moreover, optical density mean values of anti-hev igg and igm antibodies from wild boars decreased with age, with the exception of iga, which decreased from juveniles to sub-adults and then increased in adults. the sequences obtained in the three studies were phylogenetically characterized and compared with previously published hev sequences worldwide. Hev strains detected in swine and wild boars were very heterogenic and belonged to the genotype 3, like other european and spanish sequences, and were clustered together. High nucleotide identity between hev sequences from domestic swine and wild boars (76.1-99.4%), and also between wild boars and human (78.5-95.8%) was found. the results from the present thesis showed that hev is highly prevalent in both domestic swine and wild boars. Therefore, zoonotic transmission of hev to human from domestic swine and wild boars should not be neglected.
Datos académicos de la tesis doctoral «Characterization of hepatitis e virus natural infection in domestic swine and wild boars«
- Título de la tesis: Characterization of hepatitis e virus natural infection in domestic swine and wild boars
- Autor: Nilsa Olivia Razao De Deus
- Universidad: Autónoma de barcelona
- Fecha de lectura de la tesis: 02/07/2008
Dirección y tribunal
- Director de la tesis
- Joaquim Segalés I Coma
- Tribunal
- Presidente del tribunal: María no Domingo álvarez
- Juan Carlos Saiz (vocal)
- ignasi Marco (vocal)
- rosina Girones llop (vocal)