Virus High seroprevalence of bluetongue virus antibodies in sheep, th taxonomy, VIII report of the ICTV, Elsevier/Academic goats, cattle and camel in different districts of Saudi

Aim: To estimate the prevalence and distribution of serum antibodies to BTV in different domesticated animals in different localities of Saudi Arabia. 
 
Materials and Methods: A total of 4845 field sera collected from different animal species within 10 districts in the Kingdom of Saudi Arabia were screened for the presence of group-specific BTV antibodies by competitive ELISA (c ELISA). 
 
Results: The overall BTV antibody prevalence was 54.1%, 53.3%, 44.8% and 25.7% in sheep, goat, cattle and camel respectively (at 95% confidence level). The Jizan and Eastern Province districts were the regions with the highest prevalence resulting 65.8% of sheep, 68.2% of goats, 49.3% of cattle, 44% of camel in Jizan and 65.8% of sheep, 62.5% of goats, 53.4% of cattle, 28.5% of camel in Eastern Province positive to c-ELISA. The second highest rate was in Najran district where the seropositivity for Bluetongue was found to be 60% of sheep, 57.9% of goats, 47.2% of cattle and 29.3% of camel. Our results recorded positive animals in all examined districts which indicate serological evidence of exposure to infection was widely distributed all over the country. 
 
Conclusions: These results demonstrate the high occurrence of the BTV that emphasize the necessity to a well-defined control strategy for preventing and controlling the BTV in Saudi Arabia.


Introduction
subclinical infections or mild disease, to acute or even fatal disease [8].In contrast, cattle, while commonly Bluetongue virus (BTV) is an arbovirus infected in endemic and epizootic areas, rarely (arthropod borne virus) that belong to the genus develop clinical disease [9].However; the strain of Orbivirus within the family Reoviridae [1] BTV is a BTV serotype 8 that has invaded northern Europe is small (80 nm in diameter) icosahedral virus of a unusual because a large number of infected cattle also double-layered protein coat with a ten-segmented, developed clinical signs [10].So, cattle are important double-stranded RNA genome that encode four nonin transmission and acting as reservoirs for the BTV structural (NS1, 2, 3 and 3A) and seven structural [11].Camelids have also been reported to be (VP1-VP7) proteins [2,3,4].There are 24 immunosusceptible to experimental BTV infection and logically distinct BTV serotypes (BTV1 to BTV24) induced antibodies against BTV but coursed currently recognized worldwide, and recently described asymptomatically in llamas (Llama glama) (BTV-10) th Toggenburg virus is proposed to be a 25 serotype [5].[12] and in dromedary camels (BTV-1) [13].however; BTV is the causative agent of bluetongue a severe clinical form with lethal BTV-1 infection was disease, which can infect all ruminants although the reported in naturally infected llamas [14].The disease disease is normally most evident in sheep [6].It is is not contagious from animal to animal but is spread capable of inducing a severe haemorrhagic disease by biting midges of the Culicoides genus which are the with high mortality rate especially in naive domestic natural biological vectors of the BTV [15,16].The sheep [7].Sheep and some wild ruminants display a incidence of bluetongue disease is therefore closely variety of clinical manifestations, ranging from related to the distribution of the various Culicoides species which are normally associated with warm or district field veterinarians from most of districts of the hot climatic conditions [17].The area where BTV and Kingdom of Saudi Arabia (Table-1).In general, at its vectors are present has been limited to latitudes least 30 samples were collected from each herd/flock o o based on the estimated seroprevalence of 10% and a between 40 N and 35 S. Exceptions include regions of confidence limit of 95% to detect at least one positive Asia and western North America, where BTV animal [34].If the population size in a herd/flock was infection of ruminants occurs as far as 50 N [17,18].less than 30, as many animals as possible were sampled.

The presence and distribution of Culicoides in Saudi
All the sera were transported on ice and submitted to Arabia has been reported [19][20][21][22].Due to its ability to the Central Veterinary Diagnostic Laboratory in spread rapidly under suitable circumstances, BT is Riyadh where stored at -20°C until tested.classified by the World Organization of Animal Health [23] as a notifiable disease (former List A).During Competitive Enzyme linked Immunosorbant outbreaks, affected countries are banned from trading Assay(c-ELISA): The Bluetongue Competitive in livestock and livestock products triggering serious ELISA Kit: (BDSL; Biological Diagnostic Supplies socio-economic effects [24].The recent detection of Ltd., Surrey, UK) were used.The test is based on the eight additional BTV serotypes in the USA strongly detection of antibodies specific to the highly suggests that the changes in BT distribution first conserved segment 7 (VP7) of BTV.It is therefore detected in Europe may be a worldwide phenomenon, designed to detect infection by any type of BTV and/or perhaps as a consequence of climate change [25].
vaccination by any vaccine presenting the VP7 antigen.The epidemiology of BTV infection is poorly The test was carried out as described in the protocol defined in much of the world, including extensive supplied by the manufacturers, and the percentage portions of Asia and the Middle East, the species and inhibition (PI) values were calculated as described by serotypes of BTV that occur within the Middle East Afshar et.al.[35].Samples with PIs equal to or greater are poorly defined [26].A wave of abortions, stillbirths than 50% were considered to be positive, and those and deformities in sheep at Al-Ahsa in the eastern with PIs of less than 50% were taken as negative.region of Saudi Arabia due to BTV in the second half of 1999 [27].BTV has been reported in several Middle Results Eastern countries (Egypt, Jordan, Syria, Turkey, The distribution of samples and antibody Cyprus, Iraq, Iran, Oman, Qatar, Yemen and Saudi prevalence by region are shown in (Table 1).Positive Arabia) since 1951 [28][29][30][31].Abu Elzein et.al.[32] animals were found in all examined districts.The recorded the exposure of sentinel ruminants to BT overall BTV antibody prevalence was 54.1%, 53.3%, virus serotypes 10, 12, 15 and 20.Also, a novel BTV 44.8% and 25.7% in sheep, goat, cattle and camel serotype has been identified in Kuwait in 2010 [33].

Discussion
possibility of windborne carriage of infected Culicoides from distant endemic areas [47].According to FAO Bluetongue affects both domestic and wild reports, Sudan and Somalia are the two countries in the ruminants, and its origin is probably African.It was Horn of Africa with largest volume of ruminants, first identified in South Africain Merino sheep in the while Saudi Arabia is the biggest market for livestock late 18th century [36].Various techniques have been exports from the Horn of Africa and animals trade is used to detect antibodies against BTV.These include highest between Somalia and Ethiopia to the gulf area.agar gel immunodiffusion (AGID),haemagglutination-These trades from the Horn of Africa (Ethiopia, inhibition, complement fixation and ELISA, which are Somalia, Eritrea and Djibouti) into Yemen and gulf serogroup specific and serum neutralization, which is area are likely to increase mixing of animals and serotype specific.Only AGID and competitive-ELISA therefore new emerging diseases [48].Furthermore, are recommended as prescribed tests for international there is an unrestricted flow of livestock into Jizan and trade in the OIE Manual of Standards for Diagnostic Najran districts from the neighboring south borders Tests and Vaccines [23].Protein VP7 is one of the (from Yemen) where bluetongue virus (BTV) is endemic.major inner capsid proteins [37] on which several serogroup specific diagnostic assays are based to Conclusions differentiate antibodies to BTV from those to other The obtained results showed that a high orbiviruses, such as epizootic hemorrhagic disease incidence of BT antibodies has been detected among virus [38][39][40].There is no well-defined control sheep, goats cattle, and camels in the Kingdom of strategy for BTV and no vaccine is currently available Saudi Arabia that indicate serological evidence of for the strains of blue tongue in Saudi Arabia (F.exposure to infection was widely distributed all over Bayoumi, personal communication, Oct. 2010).The the country.There are no restrictions on the movement diagnosis of BT includes early recognition and of animals from one region to another within the country.notification of a suspect clinical situation by the field Thus, outbreaks may also occur due to transportation veterinarians, and/or clinical inspection by veterinary of animals.Consequently, a well-defined control inspectors of the veterinary authorities and laboratory strategy for preventing and controlling the BTV may tests on blood to detect the specific antibodies.
be based not only on vaccination plans and vector As per our Knowledge, this is the first study that eradication but also restriction on the movement of estimates the prevalence and distribution of antibodies animals from one region to another within the country.to BTV in different domesticated animals in most Further studies are being undertaken to determine the localities of Saudi Arabia.Our results revealed high BTV serotypes that are circulating in Saudi Arabia.seroprevalence (47.3%) of BTV infection which was comparable to that has been described amongst ruminants Acknowledgements in regions of Iran (34.7% seroprevalence) [26], Turkey The authors would like to thank the district field (29.5% seroprevalence) [41], India (up to 45.7% seroveterinarians and all the staff in the Animal Resources prevalence) [42] and Pakistan (48.8% seroprevalence) Administration who were involved for collecting [43].Also, seroprevalence of BTV infection was blood samples from animals.We are also thankful to reported in 73% of camels in Chad and 17.8% in Niger the Central Veterinary Diagnostic Lab for providing by agar gel diffusion test [43] and in two camel-rearing necessary facilities to carry out this work.Special regions of Somaliland (13.96%) [45].
thanks for Dr Mohamed Al-Julaifi, the Director Due to the large number of circulating BTV General of Veterinary Laboratories and Dr Yassin serotypes, it is generally impossible to predict the Ramadan for their assistance.The work was supported serotype for a specific season or area.Furthermore, financially by the Ministry of Agriculture, Kingdom of several serotypes tend to circulate simultaneously [6].Saudi Arabia grant no.(32/1/0/185/00/00/4).The highest proportion of seropositives in different livestock in Jizan, Najran and Eastern Province Competing interests districts could be attributed to climatic factors that Authors declare that they have no competing interests.favour the maintenance and recirculation of the BTV in its vertebrate and non-vertebrate hosts in addition to References the nearness of Jizan and Najran districts to the Horn 1.
Mertens P. P. C., Maan S., Samuel A., Attoui H. (2004) of Africa (Ethiopia, Somalia, Eritrea and Djibouti), Orbivirus, Reoviridae.In Virus Taxonomy, VIII Report where the enzootic nature of BTV in large regions of of the International Committee on Taxonomy of the African continent is reported [46] and there were Viruses (ICTV) (C.M. fauquet, M. A. Mayo, J.