الفهرس 
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Abstract
During the period of investigation (12 consecutive months), a total number of 120 cow calves of different ages, sex, regions were clinically carefully examined and thereafter subjected to serological diagnosis for the subsistence of PI3 and BRS viruses’ infection.
The infection rate of Parainfleunza 3 Virus and Respiratory Syncytial Virus infection of the examined cow calves was 18.2 % (8/44) and 84.1 % (37/44), respectively. The diseased cow calves with BRS virus were suffering from Pneumonia which can vary considerably, ranging from asymptomatic to severe respiratory illness. In most cases is implicated in disease, usual clinical signs include cough, fever, nasal and ocular discharge.
The serological diagnosis by using ELISA indicated that positive samples of BRS virus infection were 84.1 % (37/44) and BPI3 virus infection were 18.2% (8/44) .
Epidemiologically, for studying the relationship between rate of BPI3 virus infection and ages of cow calves, the examined cow calves (n= 120) were grouped into 5 age groups (1 days-1month, >1m-3m, >3m-6m, >6m-9m, >9m-12m). It was found that there was no significant variation between the age of examined cow calves and BPI3 and BRS viruses´ infection.
In regard to the effect of sex difference in rate of infection with PI-3 and BRS viruses, the present work revealed that sex of calves had no role in rate of infection statistically.
Effect of locality in percent of infection with BPI3 and BRS viruses was epidemiologically investigated and found that there was no significant difference in percent of BPI3 and BRS viruses’ infection in examined cow calves of individual cases and the 2 farms in Assiut Governorate.
Climatologically, the most positive cases of BPI3 virus and BRS virus infection were reported in cold months (The second half of October, November, December, January and February) of Assiut Governorate.
At the end, BRS virus and BPI3 virus play a role in causing pneumonia in cow calves in Assiut governorate especially BRSV . Our attention should be directed toward these viruses in any control programs put to overcome pneumonia in cow calves in Assiut.