دانلود رایگان مقاله خصوصیات ژنتیکی پاکس ویروس در شتر یک کوهانه

Abstract

Camelpox and camel contagious ecthyma are infectious viral diseases of camelids caused by camelpox virus (CMLV) and camel contagious ecthyma virus (CCEV), respectively. Even though, in Ethiopia, pox disease has been creating significant economic losses in camel production, little is known on the responsible pathogens and their genetic diversity. Thus, the present study aimed at isolation, identifi- cation and genetic characterization of the causative viruses. Accordingly, clinical case observations, infectious virus isolation, and molecular and phylogenetic analysis of poxviruses infecting camels in three regions and six districts in the country, Afar (Chifra), Oromia (Arero, Miyu and Yabello) and Somali (Gursum and Jijiga) between 2011 and 2014 were undertaken. The full hemagglutinin (HA) and partial Atype inclusion protein (ATIP) genes of CMLV and full major envelope protein (B2L) gene of CCEV of Ethiopian isolates were sequenced, analyzed and compared among each other and to foreign isolates. The viral isolation confirmed the presence of infectious poxviruses. The preliminary screening by PCR showed 27 CMLVs and 20 CCEVs. The sequence analyses showed that the HA and ATIP gene sequences are highly conserved within the local isolates of CMLVs, and formed a single cluster together with isolates from Somalia and Syria. Unlike CMLVs, the B2L gene analysis of Ethiopian CCEV showed few genetic variations. The phylogenetic analysis revealed three clusters of CCEV in Ethiopia with the isolates clustering according to their geographical origins. To our knowledge, this is the first report indicating the existence of CCEV in Ethiopia where camel contagious ecthyma was misdiagnosed as camelpox. Additionally, this study has also disclosed the existence of co-infections with CMLV and CCEV. A comprehensive characterization of poxviruses affecting camels in Ethiopia and the full genome sequencing of representative isolates are recommended to better understand the dynamics of pox diseases of camels and to assist in the implementation of more efficient control measures.

4. Discussion

We have isolated poxviruses, CMLV and CCEV, affecting camels from outbreak samples originating from three major camel rearing regions of Ethiopia and analyzed their genetic diversity. During our investigations, we have observed pox-like skin lesions with similar severity in both sexes and all age groups; however, for the camel contagious ecthyma suspicions, the disease appeared to be more severe in young camels of less than two years old. Khalafalla et al., 2015b also noticed that young camels were at high risk of CCEV infections. Even though camels were reared together with small ruminants and cattle in the visited areas, pox disease was observed only in camels, confirming a narrow host range for both CMLV (OIE, 2012) and CCEV. We have also noticed that pox disease occurrence in camels was high during the rainy season. Ayelet et al., 2013 and Khalafalla et al., 2015b also recorded highest incidences of CMLV and CCEV infections during rainy season. This could be attributed to an increase in the presence of arthropod vectors during the wet period. Indeed, CMLV was isolated from a camel tick e Hyalomma dromedarii taken from infected camels (OIE, 2012), suggesting a possible role of this insect in CMLV transmission.