الفهرس 
Acknowledgments
Etiology and viral classificationOnly 14 pages are availabe for public view
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Abstract
In Egypt, RHDV is still representing a threat in the rabbit production farms in spite of vaccination programs due to high fatality rates. The epidemiological data concerning of RVHD revealed that the disease start in November and continues till May of the following 2 years. The disease found to decrease during summer and autumn months and observed in different breeds of rabbits aged 2-21 months but infection in rabbits less than 2 months was not observed. Both sexes were affected including pregnant females. The mortality rate was up to 80% in aged less than 6 months and up to100% among adult rabbits.
Clinical signs and post mortem lesions of the examined naturally infected rabbits exhibited the typical signs of RHD as described in previous studies, which indicates that they play a significant role in the identification of the RHD viral infection.
Tissue collected from infected rabbits, was mainly the liver, as it contains the highest concentration of the viral particles.
The first test applied for RHDV diagnosis was the haemagglutination test using human type (O) In the current study, positive HA reaction for 70 which represented (91%) from 77 examined samples were able to haemagglutinate human type (O) RBCs with HA titers ranging from 24 to 27 .
The liver suspensions were serologically identified as RHDV by HI test by using specific antiserum. HI titers were ranged from 1:8 to 1:512.
Regarding to the Pathogenicity of RHDV, the clinical signs of infected rabbits were similar to those observed in natural infection which included pyrexia, anorexia, dyspnea, convulsion, paralysis and epistaxis and also vaginal haemorrhages in some females. Infected rabbits died within 72-96 hours post infection. The mortality rate was higher among 6 month old rabbits (100%), while in 2 month old rabbits was 80%. The post mortem lesions were similar to those observed in natural infection.
Histopathology findings in naturally infected rabbits included congestion of alveolar capillaries and haemorrhage at the alveoli, multiple microthrombi in the pulmonary blood vessels and severe heamorrhage at the alveolar and interstitial tissue. Liver showed multiple microthrombi in the hepatic blood vessels, fibrin thrombus in the central vien and sinusoids associated with necrosis in the hepatocytes, and severe heamorrhage associated with hepatocellular necrosis. Kidneys showed multiple microthrombi at the glomerular tufts associated with necrobiosis at the renal tubular epithelium, severe glomerular heamorrhage, and interstitial heamorrhage at the renal medulla.
In experimentally infected rabbits; Lungs showed multiple pale thrombi at the pulmonary vasculature, and severe heamorrhage at the lung tissue. Liver showed multiple microthrombi in the hepatic blood vessels associated with necrobiosis of the hepatocytes, and focal area of necrosis infiltrated with lymphocytic cells. Kidneys showed multiple microthrombosis at the glomerular tufts, glomerular heamorrhage and interstitial heamorrhage at the renal medulla.
The prepared inactivated vaccine proved to be sterile as no bacterial growth was observed on blood agar, thioglycolate broth even after 14 days of incubation at 37°C. The vaccine was stable for 20 days at 37°C and room temperature; however, at 4°C it remains stable for 4weeks and proved to be safe.
The experimental focus of this proposal is to evaluate the ability of locally prepared RHDV vaccine from the field isolated strain in comparison with imported vaccine to induce better protection against infection in vaccinated rabbits.
Both groups of rabbits receiving prepared and locally tissue derived inactivated RHVD vaccines were 100% protected from morbidity and mortality against virulent RHDV challenge as all rabbits in each of the groups remained normal during the course of the experiment.
High titers of RHDV specific HI antibodies were detected in the sera of vaccinated rabbits from the 2 WPV where the obtained mean geometric titers (MGTs) were 25 HI RHD-antibodies