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Sirvi Autor "Raaperi, Kerli" järgi

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  • Pisipilt
    Kirje
    Epidemiology, impact on herd health and control of bovine herpesvirus 1 in Estonian dairy cattle herds
    (Eesti Maaülikool, 2012) Raaperi, Kerli; Viltrop, Arvo (advisor); Orro, Toomas (advisor)
    The objective of the present doctoral thesis was to assess the herd-level and within-herd prevalence of bovine herpesvirus 1 (BHV-1) infection in Estonian dairy cattle and estimate the sensitivity and specificity of the ELISA test for bulk tank milk (BTM) testing in detecting infected herds. The aim was to determine the risk factors related to high prevalence of the infection in herds and presence of BHV-1 among youngstock. We also aimed to clarify the role of BHV-1 in the incidence of bovine respiratory disease (BRD) in different age groups and evaluate the association between prevalence of BHV-1 and herd reproduction parameters. The last objectives were to assess the efficacy of vaccination programmes in lowering the seroprevalence of BHV-1 glycoprotein E (gE) within the herd as well as to follow the dynamics of the infection in non-vaccinating herds with uninfected replacement heifers. Prevalence study was accomplished between 2006 to 2008. One hundred and three (64 BHV-1 infected ja 39 uninfected) dairy cattle herds with more than 20 cows and with different size were selected for the study. In each of the selected herds, serum samples from a representative number of cows, and youngstock older than 6 months, were analyzed for BHV-1 antibodies. The source population used to estimate the herd level prevalence of BHV-1 consisted of all 1,205 market-oriented dairy herds. Vaccination programmes with inactivated gE marker vaccines to eradicate BHV-1 were elaborated for seven dairy herds. Five BHV-1-infected dairy herds, which had uninfected heifers (prevalence up to 5 per cent), were selected to monitor the course of the infection without control strategies. To monitor the efficacy of the vaccination, and changes in seroprevalence during the control programme, a longitudinal two year surveillance programme was carried out in those herds. Due to the moderate sensitivity of the BTM ELISA test (76.5%) it should be used with caution when making decisions about the infection status of a herd. Lower cut-off in the ELISA blocking reaction might be justified when using BTM testing in BHV-1 control programmes to be able to discover more infected herds with only a minimal loss in specificity. Twenty two percent of Estonian market-oriented dairy cattle farms are infected with BHV-1. When elaborating control programmes most of the resources should be directed to herds with more than 100 cows as those farms contain the main population infected with BHV-1. As within-herd prevalence of BHV-1 is generally high in larger herds vaccination with gE marker vaccines combined with eradication of gE positive animals is the most appropriate way to eradicate the virus in those herds. Where the within-herd prevalence is low culling of the seropositive animals without vaccination would be most cost-effective. Youngstock tested negative in 36.5% of infected herds. These herds are in more favourable situation when applying an eradication programme because it is possible to raise a BHV-1-free generation from their own herd and vaccinate youngstock just before introduction to the cow house, as long as the farmer can provide isolation facilities. The duration of vaccination programme is shorter when replacement animals are free of infection reducing the cost of eradication. In herds under control programmes it is important to be aware of the important risk factors that are related to spread of the infection within a herd. In BHV-1 positive herds more attention should be paid to possible iatrogenic transmission via the veterinarian and inseminator, and within-herd biosecurity measures should be kept in mind. Infection with bovine viral diarrhea virus (BVDV) may also be a predisposing factor for more effective viral spread. Although several infectious and management-related factors are associated with BRD in dairy calves and heifers, BHV-1 and BVDV had significant impact on the manifestation of clinical respiratory disease. BVDV contributed to the occurrence of respiratory disease signs in older youngstock. Bovine respiratory syncytial virus was related to clinical respiratory disease in adult dairy cattle. The use of control measures for these viruses may reduce the incidence of respiratory disease and improve herd health. In herds with poor reproductive performance, BHV-1 should be considered as one of the infectious risk factors, and the eradication of this virus may improve the reproductive performance of the herd. Vaccination with inactivated marker vaccine is a secure method to stop virus circulation within a herd as long as the vaccination protocol is followed precisely. On the other hand, in some herds the virus circulation may end by itself for longer periods, which may lead to self-clearance of the herd from the virus. However, aiming for eradication in herds with uninfected young-stock leaving animals unvaccinated has an unpredictable outcome – virus circulation may remain retarded or the virus may reactivate and cause an epidemic in the herd.
  • Pisipilt
    Kirje
    Terve loom ja tervislik toit : konverentsi "Terve loom ja tervislik toit 2014" postrid
    (Eesti Maaülikool, 2014) Anton, Dea; Soidla, Riina; Püssa, Tõnu; Ilves-Luht, Aire; Harzai, Hedi; LIng, Katri; Kaart, Tanel; Soomets, Ursel; Kilk, Kalle; Ots, Meelis; Jeremejeva, Julia; Orro, Toomas; Kask, Kalle; Kaldre, Katrin; Haugjärv, Kerli; Liiva, Mari; Gross, Riho; Kass, Marko; Mäesaar, Mihkel; Roasto, Mati; Meremäe, Kadrin; Kramarenko, Toomas; Muutra, Kaisa; Raaperi, Kerli; Viltrop, Arvo; Saar, Tiiu; Põdersoo, Diivi; Golovljova, Irina; Tefanova, Valentina; Soonberg, Maria; Arney, David; Tänavots, Alo; Kaart, Tanel; Kiiman, Heli
    Dea Anton, Riina Soidla, Tõnu Püssa. Analüüsid tomatiga rikastatud lihatoodetes.