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The genus Capripoxvirus within the subfamily Chordopoxvirinae, family Poxiviridae comprises three closely related viruses, namely lumpy skin disease (LSD), sheeppox (SP) and goatpox (GP) viruses. This nomenclature is based on the animal species from which the virus was first isolated, respectively, cattle, sheep and goat. These viruses are the etiological agents of economically important diseases which collectively constitute the most serious poxvirus diseases of production animals [14]. Lumpy skin disease is an acute, subacute or inapparent viral disease of cattle characterized by pyrexia, generalized skin and internal pox lesions, and generalized lymphadenopathy [10, 23, 28]. The disease is endemic in Central and southern Africa.The first report of LSD outside Africa was from Kuwait in 1986-1988 [1], followed by Israel in 1989 [30]. In Egypt, the LSD was first appeared in the Suez Governorate after cattle were imported from Somalia followed by the Ismailyia Governorate in 1988 [18] and two disease outbreaks were reported in 2005 and 2006 [26, 36]. There were 2 outbreaks of LSD in Israel during 2006 and 2007 and it is believedbe transmitted by yet an unconfirmed insect vector from Egypt [31].
The LSDV genome is a linear dsDNA molecule of 151 kb that consists of a central coding region bounded by identical 2.4 inverted terminal repeats and contains 156 putative genes [32]. Capripoxviruses are antigenically indistinguishable from each other and able to induce heterologous cross protection and the complete nucleotide sequences of the capripoxvirus genomes are 97% similar [5, 9, 10, 33]. Although capripoxviruses are generally considered to be host specific, because disease outbreaks occur in one host species [14], it is known that SPV and GPV strains can naturally or experimentally cross-infect and cause disease in both host species [20, 21]. However, while LSDV can experimentally infect sheep and goats [4, 22], natural infection of sheep and goats with LSDV has not been described previously.
There have been reports of the occurrence of LSD outbreaks in Egypt and Israel and the presence of LSDV circulate in some farms although animals were vaccinated with sheep pox vaccine [2, 3] as well as the appearance of sheep pox cases in areas that are affected by LSD. Therefore we studied the antigenic correlationship between field skin isolates of LSDV, tissue culture adapted LSDV/Ismailyia88 strains, field skin isolates of SPV and the SPV/Kenyan vaccinal strain. We also compared the nucleotide sequence of the attachment gene offield skin isolates of LSDV, tissue culture adapted LSDV/Ismailyia88 strain, field skin isolates of SPV and SPV /Kenyan vaccinal strain to gain new insights into the biology and aid the development of new method of effective control of this disease.
Sequence Analysis of Attachment Gene of Lumpy Skin Disease and Sheep Poxviruses
- Received Date: 21 May 2010
- Accepted Date: 29 September 2010
Abstract: Egypt, protection of cattle against lumpy skin disease (LSD) was carried out using a sheep poxvirus (Kenyan strain) vaccination strategy. In the present study 15 skin nodules from LSD suspected cows and 5 scab samples from sheep pox (SP) suspected sheep were collected. Hyperimmune rabbit sera to Lumpy skin disease virus (LSDV)/Ismailyia88 strain and sheep pox virus (SPV)/ Kenyan vaccinal strain were prepared. The causative agent in the collected samples was identified using immunoflourescence (IF) and immunoperoxidase techniques. Of the 15 skin nodules suspected of LSD, 10 showed a positive reaction and 3 out of 5 skin scabs suspected of sheeppox were found to be positive. An antigenic correlation between field skin isolate of LSDV, tissue culture adapted LSDV/Ismailyia88 strain, field skin isolate of SPV and SPV/Kenyan vaccinal strain was studied using prepared hyperimmune sera. Also, nucleotide sequence of the PCR amplified attachment gene fragments of field skin isolate of LSDV, tissue culture adapted LSDV/Ismailyia88 strain, field skin isolate of SPV and SPV /Kenyan vaccinal strain were compared. The results revealed that the four used viruses were antigenically identical. Sequence analysis indicated that field skin LSDV isolate is more related to tissue culture adapted LSDV/Ismailyia88 strain than to vaccinal SPV/ Kenyan strain and the skin isolate of SPV is more closely related to field skin isolate of LSDV than to SPV/Kenyan vaccinal strain. Thus, further study should be applied on the advantage of a LSD vaccine prepared from LSDV in protection of cattle against LSD compared to the commonly used sheep pox vaccine.