الفهرس 
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Abstract
Neonatal diarrhea is an important worldwide problem. The disease results in major economic losses in many dairy and beef cattle herds that result from treatment costs and calf deaths.This study deals with 3 viral agents (BVDV, Rotavirus and Coronavirus) correlated with diarrhea in newborn calves (from 1 day to 6 months). Diagnosis of BVDV, Rotavirus and Coronavirus depends on serological identification of viral antigens and molecular identification of nucleic acids using RT-PCR. Therefore the current study aims to conduct identification of the 3 viruses in calves at different governorates including kalubia, Sharkia, Gharbia and Menofeia, all over the four seasons of the year 2012 and 2013. 250 serum samples were collected from clinically suspected unvaccinated cattle and buffaloe calves showing sings of diarrhea for detection of BVDV antigen using antigen –capture ELISA then detection of the virus using RT-PCR. 250 fecal samples were collected from clinically suspected calves showing signs of diarrhea. It was used for the detection of both Rota virus and coronavirus using sandwich ELISA then detection of the virus using RT-PCR The Applied tests have shown the following: By using antigen capture ELISA test for detection of BVDV antigen in calves’ serum samples, it was found that the total positive samples were 8.4% from 250 total examined samples. In correlation to species, 8.3% cattle calves and 8.4% buffalo calves were positive for BVDV antigen. In correlation to age, BVDV antigen was highly distributed among bovine calves within 6th month old reached 18%. While bovine calves with one and 3 months olds showed BVDV antigen in their sera by 6.3% and 10.6% respectively. Sera from 2 months olds bovine calves were free. These indicate higher susceptibility of bovine calves among 6th month to BVDV infection. Examined serum samples all over the four seasons of the year 2012 and 2013 indicates prevalence of BVDV infection by 12.3% during winter, 4% during summer, 3.6% during spring and 5.1% during autumn . This indicates higher susceptibility to BVDV infection in winter. By using antigen sandwich ELISA test for detection of Rotavirus antigen in calves’ fecal samples; it was found that the total positive samples were 30% from 250 total examined samples. In correlation to species, 32.9% cattle calves and 26.2 % buffalo calves were positive for Rotavirus antigen. This indicates higher susceptibility of cow calves to BVDV infection.In correlation to age, Rotavirus antigen was highly distributed among bovine calves within one month old reached 38.4%. While bovine calves with 2, 3 and 6 months olds showed Rotavirus antigen in their feces by 31.7%, 17% and 22% respectively. Regarding the distribution of Rotavirus infection in diarrheic bovine calves up to one month of age, Bovine calves within one week old showed higher antigen detection 46.6% while bovine calves with 2, 3 and 4 weeks old showed Rotavirus antigen in their feces by 41.4%, 17.6% and 12.5%. Examined fecal samples all over the four seasons of the year 2012 and 2013 indicates prevalence of rotavirus infection by 43.1% during winter, 20% during summer, 21.4% during spring and 5.1% during autumn. This indicates higher susceptibility to Bovine Rotavirus infection in winter. By using antigen sandwich ELISA test for detection of Coronavirus antigen in calves’ fecal samples; it was found that the total positive samples were 7.6% from 250 total examined samples. In correlation to species, 8.4% cattle calves and 6.5 % buffalo calves were positive for Coronavirus antigen. This indicates higher susceptibility of cow calves to Coronavirus infection. In correlation to age, Coronavirus antigen was highly distributed among bovine calves within one month old reached 11.6% while bovine calves with 2, 3 and 6 months olds showed Coronavirus antigen in their feces by 4.9%, 2.1% and 6% respectively.Regarding the distribution of Coronavirus infection in diarrheic bovine calves up to one month of age, Bovine calves within two and three week old showed higher antigen detection 31.3% and 23.5% respectively. Coronavirus antigen was not detected in bovine calves within one and 4 weeks old. Examined fecal samples all over the four seasons of the year 2012 and 2013 indicates prevalence of Coronavirus infection by 10% during winter, 7.1% during spring and 5.1% during autumn. Coronavirus antigen was not detected during summer months. This indicates higher susceptibility to Bovine coronavirus infection in winter. By using antigen sandwich ELISA for detection of Rota and Corona viruses’ antigens in calves’ fecal samples; it was found that 3.2% of samples were positive. In correlation to species, 3.5% cattle calves and 2.8 % buffalo calves were positive for both Rota and Corona viruses’ antigens. In correlation to age, Rota and Corona viruses’ antigens were highly distributed among bovine calves within one and two month old reached 5.4% and 4.9% respectively. Examined fecal samples all over the four seasons of the year 2012 and 2013 indicates prevalence of mixed infection with Rota and Corona viruses by 4.6% during winter and 8% during summer. Mixed infection was not detected during autumn and spring months. Molecular identification of BVDV by using RT-PCR, revealed the presence of specific PCR product at the correct expected size of the BVDV type I (190 bp). Molecular identification of rotavirus by using RT-PCR, revealed positive for amplification of bands at the predicted molecular size (1356 bp of VP6 genes).Molecular identification of coronavirus by using RT-PCR revealed the presenceof specific PCR product at the correct expected size of coronavirus (Mebus strain) (407 bp). Both ELISA and RT-PCR detected BVDV in sera and Rotavirus and Coronavirus in feces of diarrheic bovine calves. RT-PCR detected further 3 positive samples for BVDV (2 for cattle calves and one for buffalo calves), 2 positive samples for Coronavirus (one for cattle calves and one for buffalo calves) and one positive sample for Rotavirus in cattle calves. This indicates sensitivity for both ELISA and RT-PCR with superiority of RT-PCR.