الفهرس 
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Abstract
Healthy calf is a cornerstone of animal breeding for beef and/or milk production. Calf enteritis is a common syndrome causing colossal economic losses in term of morbidity, dwindle growth rate, costs of therapeutic and control measures, and deaths. Rotavirus is major pathogen of calf diarrhea. Clinical and epidemiological aspects of calves’ enteritis associated with Rotavirus in Assiut Governorate, Upper Egypt were aimed in the current study.
During the period of investigation (23 consecutive months), a total number of 175 neonatal calves were subsequently inspected, carefully investigated and thereafter subjected to serological and molecular diagnosis for subsistence of Rotavirus infection.
Comprehensively, the infection rate of Rotavirus of the examined calves was 9.14 % (16/175). The main clinical findings in Rotavirus varied from mild, moderate to severe diarrhea. Feces were mucoid yellowish with and/or without flakes of clotted blood. The diseased calves showed weakness, unable to stand, arched back with straining during defecation, anorexia, variable degree of dehydration. Body temperature, respiratory rate and heart rate were high in some cases or were low and normal in others.
The serological diagnosis by using LAT and ICA indicated that positive samples of Rotavirus infection were 9.68% (9/93) and 8.54% (7/82), respectively, referring to sensitivity and feasibility of LAT and ICA in diagnosing of calf’s diarrhea associated with Rotavirus infection.
The molecular diagnosis of Rotavirus infection by using RT-PCR indicated that positive samples by VP7 and VP4 genes were 100% (16/16) and 81.25% (13/16), respectively; referring to VP4 RT-PCR was less sensitive than VP7 RT-PCR.
The molecular typing of Rotavirus with G and P genotyping was performed by using semi-nested multiplex PCR. 93.75% (15/16) samples were positive for G-Genotyping and 81.25% (13/16) samples were positive for P-Genotyping. G6 was detected in 10 (62.50%) out of 16 samples and G10 was diagnosed in 5 (31.25%) out of 16 samples and one (6.25%) sample did not react with any G primer used. G6 was the most common genotype of BRV in diagnosed fecal samples of enteric calves. P5 was detected in 9 (56.25%) out of 16 samples, P11 was diagnosed in 3 (18.75%) out of 16 samples, mixed infection with P5+P11 was observed in 1 (6.25%) out of 16 samples and 3 (18.75%) samples did not react with any P primer used. P5 was the most common genotype of BRV in diagnosed fecal samples of enteric calves. The present study revealed the absence of G8 and P1 genotypes among BRVA in Assiut governorate.
G and P genotypes combination in the present study revealed that G6P5, G6P11, G10P5 and G10P11 were circulating genotypes in bovine population in Assiut governorate. G6P5 strain was the most common of all strain diagnosed in other fecal samples. The presence of various combinations of G and P genotypes among field isolates of BRV suggests that genetic reassortment frequently occurred between viral strains with genes encoding different G and P genotypes.
DNA sequencing and phylogenetic analysis of BRVA were performed in our study. 5 different field genotypes (2 G6P5, 1 G10P5, G10P? and 1 G10P11) were subjected to DNA sequencing. We observed that at nucleotide level, G10P5 and G10P? sequences were 100 % identical with each other, two G6P5 sequences were 100% identical with each other and there was no significance similarity between sequence of G10P11 with sequences of G6P5, G10P5 and G10P?.
The phylogenetic analysis of G10P5 and G10P? isolates showed close cluster with G10 isolates of Sharkia governorate, Egypt, phylogenetic analysis of two G6P5 and one G10P11 isolates showed close cluster with VP4 gene of Rotavirus isolates of Dakahlia governorate, Egypt.
Molecular comparison between detected and typed Rotaviruses’ genotypes with other genotypes of common vaccines indicated that there was genetically close or distance between field and vaccinal Rotavirus strains.
Epidemiologically, for studying the relationship between rate of Rotavirus infection and ages of calves, the investigated calves (n= 175) were grouped into 4 age groups (3 days-2week, >2-4, >4-6 and >6 weeks-2months). It was found that there was no significance variation between age of examined enteric calves and Rotavirus infection although the higher percentage of Rotavirus infection in age group >2-4weeks and lower infection rate in other age groups. The infection rate was gradually declined by increasing of age of the calves. The rate of Rotavirus infection decreased due to immune system of calves is not fully matured to handle Rotavirus infection.
In regard to the effect of sex difference in rate of infection with Rotavirus, the present work revealed that sex of enteric calves had no role in rate of infection statistically.
Effect of locality in percentage of infection with Rotavirus was epidemiologically investigated and found that there was no significant difference between rate of infection with Rotavirus in the individual cases that admitted to Veterinary Teaching Hospital, Assiut University in comparison with enteric calves on farms (Faculty of Agriculture farm, Maser El-Khear farm and Aldibat farm).
Effect of species and breed susceptibilities of examined enteric calves to Rotavirus infection were monitored in the present study and concluded that there were no significance difference in breed susceptibility of calves (Native and Mixed) to infection, all were infected. Moreover the susceptibility rate of examined enteric cattle and buffaloes’ calves were statistically parallel.
Climatologically, the most positive cases of Rotavirus infection were reported in cold months (The second half of November, December, January and February) of Assiut Governorate. Conversely the lower infection rate of Rotavirus was recorded in hot months. Such variations was interpreted and discussed.