Detection, identification, and differentiation of sheep pox virus and goat pox virus from clinical cases in Giza Governorate, Egypt

Abstract

Aim: To isolate, identify, and differentiate Capripoxviruses (CaPV) (sheep pox virus and goat pox virus) infections by egg inoculation, transmission electron microscopy (TEM), and 30 kDa RNA polymerase subunit gene-based polymerase chain reaction (PCR) (RPO30) in clinically affected animals in Hawamdia township of Giza Governorate, Egypt. Materials and Methods: A total of 37 scab samples were collected from clinically suspected field cases of sheep pox and goat pox. These samples were collected during (2014-2015) during different outbreaks of sheep pox and goat pox from Hawamdia township of Giza Governorate, Egypt. The samples were subjected to egg inoculation, TEM, and (RPO30) gene-based PCR. By using the egg inoculation: Previously prepared 37 scab samples (n=23 sheep and n=14 goats) were inoculated on the chorioallantoic membrane of specific pathogen free (SPF) embryonated chicken eggs (12 days old age). In the presence of the suitable percentage of humidity and candling, the inoculated eggs were incubated at 37°C. By using the TEM: Samples showed positive pock lesions on the chorioallantoic membranes, were fixed in glutaraldehyde, then processed and sectioned for TEM. Using the (RPO30) gene-based PCR assay, 30 of positive samples after egg inoculation (n=19 sheep and n=11 goats) were screened. Results: Using the egg inoculation, a characteristic pock lesions for poxviruses were seen in 30/37 (n=19 sheep and n=11 goats) (81.08%). Using the TEM, examination of the positive samples after egg inoculation revealed positive result in 23/30 (n=15 sheep and n=8 goats) (76.66%). The positive results represented by the presence of negatively stained oval-shape virus particles. Using the (RPO30) gene-based PCR assay, out of 30 total of positive samples after egg inoculation (n=19 sheep and n=11 goats) were screened, 27 (90%) samples (n=17 sheep and n=10 goats) were positive. The given band sizes of sheep and goats were 172 and 152 bp, respectively. Conclusion: PCR assay depended on RPO30 gene can be used lonely for the detection, identification, and differentiation of CaPVs. RPO30 gene-based PCR assay in combination with gene sequencing helps in molecular epidemiological studies of CaPV infection.