الفهرس 
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Abstract
Two studies were conducted to study some of the epidemiological aspects of canine parvovirus enteritis in dogs in some localities in the Giza Governorate, Egypt during the years 2019 and 2020. The first study aimed to characterize canine parvovirus type 2 (CPV-2) strains, circulating in the Giza Governorate, Egypt. A total of 22 rectal swabs collected from dogs with clinical signs suggestive of canine parvovirus enteritis were tested for the presence of CPV-2 using field (CPV-2 Ag rapid kits) and molecular (conventional PCR) techniques; further molecular investigation (sequencing) was conducted for the characterization of 16 samples. Results revealed that 20 samples were positive by the rapid kits, whereas 22 were positive by conventional PCR. CPV-2a was the predominant variant (12/16, 75%) followed by CPV-2c (3/12, 18.75%) and CPV-2b (1/16, 6.25%). The majority of samples (16/22) were obtained from non-vaccinated rather than vaccinated dogs. Therefore, it could be concluded that commercial vaccine strains (original strain or CPV-2b) might protect puppies against field strains; however, it is recommended to confirm this conclusion by further challenge studies. The second study aimed to investigate the association between some selected risk factors (the early finish of the primary puppy vaccination series and the antigenic variations) and the occurrence of CPV-2 vaccination failure in fully vaccinated puppies. The study included 58 CPV-2 clinically suspected cases, including 17 non-vaccinated and 41 vaccinated puppies with finished primary vaccination series. According to the minimum puppy’s age recommended by the international canine vaccination guidelines for the administration of the primary puppy vaccination series’ last dose, vaccinated puppies were recruited into either the recommended (≥16 weeks) or the early (<16 weeks) finish age groups. Conventional PCR was performed to confirm the clinical diagnosis and all CPV-2 positive samples were molecularly characterised. The differences between the early and recommended age groups regarding the frequency of CPV-2 positive cases, and the differences between the vaccinated and non-vaccinated puppies regarding the frequency of each of the CPV-2 variants were analysed for their statistical significance. Forty-one puppies, including 13 non-vaccinated and 28 vaccinated were positive for CPV-2 field strains. All vaccinated, CPV-2 positive puppies belonged to the early finish age group; this early finish was identified as a risk factor for CPV-2 vaccination failure (P < 0.00001). Six puppies were recently vaccinated within a few days before the illness; except for vaccination in veterinary clinics, these puppies have never been taken outdoors, indicating that they were exposed to CPV-2 field strains in contaminated clinics during these vaccination visits, resulting in vaccination failure. The difference between vaccinated and non-vaccinated groups was statistically non-significant (P = 0.16038), indicating that there was no particular variant specifically infects vaccinated puppies; therefore, the antigenic variation might not cause vaccination failure. These findings emphasise the need for practitioners to follow the international canine vaccination guidelines and to apply strict CPV-2 preventive measures in veterinary clinics.