Serological evidence of natural exposure of camels (Camelus dromedaries) to foot and mouth disease virus

The World Organization for Animal Health (OIE) Code chapter on FMD includes camelids as being susceptible species to FMD similar to cattle, sheep, goats and pigs. A total of 376 field camel sera, collected from different regions of Riyadh and AlQassim Province in the Kingdom of Saudi Arabia, were screened for the presence of antibodies produced against 3ABC non® structural proteins (NSP) of FMDV using a commercially available kit , PrioCHECK FMDV NS. Sera that tested positive on NSP were screened for serotype-specific antibodies towards the seven serotypes of FMD virus using liquid phase blocking ELISA. Only 24 out of 376 (6.3%) serum samples were positive for antibodies against NSP. All sera that tested positive on NSP and screened for antibodies against all the seven FMDV serotypes (O, A, C, Asia 1, SAT 1, SAT 2 and SAT 3) were found positive for antibodies against serotype O. This


Introduction
described FMD outbreaks in Mongolia in the 1970s, and more recently in 2001 as affecting Bactrian camels Foot-and-mouth disease (FMD) is a highly reared together with diseased cattle, goats and sheep, contagious disease affecting domestic and wild cloven although no samples from camels were tested and the hooved animals (Artiodactyla).It remains the single diagnosis was done only on clinical observation (V.most difficult animal viral disease to control and Kouba 2005, cited in Larska et.al. 2009).Bactrian causes severe economic losses to the livestock camels can relatively easily be infected with FMDV industry (Alexandersen et.al. 2003; Alexandersen and under experimental conditions and develop frank Mowat, 2005).Camelids belong to the suborder clinical disease (Larska et.al. 2009), while Several Tylopoda, order Artiodactyla (Wernery and Kaaden, investigations appear to indicate that dromedaries are 2002).The World Organization for Animal Health of low susceptibility to inoculation with FMD virus (OIE) code chapter on FMD includes the Camelidae as serotype O but that they do not present a risk in susceptible species to FMD, similar to cattle, pigs, transmitting FMD to susceptible animals (Wernery sheep and goats but infection dynamics vary across all and Kaaden, 2004; Alexandersen et.al. 2008).these species (OIE, 2009).
However, Kumar et.al.(1983)described isolation of The Camelidae inhabit countries in North and FMDV serotype O from one of two randomly selected East Africa, Middle and East Asia as well as South dromedaries in India and Moussa et.al.(1987) in America where FMD is endemic (Du et.al. 2009).Egypt have described a strain of type O FMD virus Opinions vary widely whether animals of the was isolated in Giza from a camel with vesicular, Camelidae family are susceptible to FMD or not, or if ulcerative stomatitis and they suggested that they may serve as viral reservoirs.The two closely dromedaries are susceptible to natural FMD.related camel species of Bactrian and dromedary The aetiological agent, foot and-mouth disease camels possess noticeably different susceptibility to virus (FMDV), is classified with the Aphthovirus genus FMD virus (Larska et.al. 2009).Several authors as a member of the Picornaviridae family and exists as many subtypes and variants within seven different serotypes of FMDV.serotypes (A, O, C, Asia1, and South African Territories The PrioCHECK® FMDV NS: Commercial ELISA kit 1, 2, and 3) (Belsham, 2005).FMDV is a small produced by Prioncs Lelystad B.V.The Netherlands nonenveloped virus with an 8.5-kb genome which for detection of antibodies against the non-structural codes for structural as well as nonstructural proteins proteins (NSP) of FMDV that could be used to test (NSPs).The viral capsid is composed of four structural serum samples of cattle, sheep, goats, camel and pigs.proteins, VP1, VP2, VP3 and VP4 (Fry et.al. 2005).
The assay was performed as described by the Antibodies principally to the structural proteins of manufacture.Briefly, test plates of the kit contain FMDV were induced in vaccinated animals, whereas FMDV NSP captured by the coated 3ABC specific infected animals produce antibodies to both the mAb.The test is performed by dispensing the test structural and nonstructural proteins.Therefore, assays samples to the wells of a test plate.After incubation the demonstrating antibodies against non-structural plate is washed and the conjugate [mAb horseradish proteins have potential to differentiate infected peroxidase (mAb-HRPO)] is added.Specific animals from those that have been vaccinated ( sera, they will block the antigen and prevent it from was observed in camels at time of sampling, although binding to the coating antibody.If there are no specific many of them had daily contact with infected antibodies in the test sera then the antigen will be ruminants.Whole blood was collected from the available to be trapped on the plate, this will be jugular vein of each animal randomly selected from detected by a positive colour indicating negative test the herd and the blood was stored at room temperature results.until the serum was separated (3-4 h on average).The serum was collected; then transferred into a sterile Results and Discussion o cryotube and stored at -20 C until tested for the FMDV type O is endemic in all countries of the presence of antibodies produced against NSP of Middle East region (Samuel and Knowles, 2001).FMDV.Sera that tested positive on NSP were screened FMD is endemic in Saudi Arabia with control for serotype-specific antibodies towards the seven strategies focusing on vaccination of cattle and small animals, including Bactrian camels, pigs and cattle, ruminants, while camels are not included in the that are susceptible to FMDV infection.In this study a vaccination campaigns.Camels are frequently moved lower FMD seroprevalence of camel examined sera across the desert due to seasonal variations, obtained was in agreement with Alexandersen et.al.availability of grazing land, fairs etc. may lead to (2008) and Wernery and Kaaden (2004) who found dissemination of various diseases from affected that camels are low susceptibility and do not present a animals to other healthy animals in disease free region.risk in transmitting FMD to susceptible animal species.
Our results in table (1) revealed only 24 out of On the other hand, Farag et.al.(1998) were not 376 (6.3%) serum samples from Riyadh and Al-able to isolate FMDV from 30 probang samples Qassim Province were positive for antibodies against harvested from dromedaries on different farms in NSP.All sera that tested positive on NSP and screened Saudi Arabia where FMD was said to be endemic.for antibodies against all the seven FMDV serotypes Moreover; pathological lesions of suspected FMD (O, A, C, Asia 1, SAT 1, SAT 2 and SAT 3) were found (severe mouth ulceration) were recorded in a camel positive for antibodies against serotype O.These (Fig. 1a-b) at Northern Borders province in Saudi results indicate serological evidence of camel Arabia at Jan 2008, where; no FMDV was detected by exposure to FMD infection that could be attributed to Antigen FMD ELISA in that tested collected samples movement of camels in an area that experienced FMD in the central veterinary diagnostic lab. in Riyadh outbreaks and camels may come in contact with (unpublished data).This negative ELISA result does infected fully susceptible animals such as cattle and not necessarily mean that the sample was truly small ruminants.We could be concluded that: dromedaries appear would lead to much greater viral replication and however as being susceptible to infection with FMDV disease within these species and there is close serotype O, but they are unlikely to play any significant relationships among the integrins of cloven-hoofed role in the natural epidemiology of FMD.
negative as it may contain concentrations of virus The susceptibility of cloven-hoofed livestock insufficient for the ELISA to detect (Ried et.al.2001).was postulated by Du et.al.(2009) who found the Conclusion structures of their integrin receptors were more susceptible to binding with the viral surface, which

Figure :
Figure : Severe mouth ulceration of camel reveals a suspected case of FMD Berger antibodies directed against the NSP, that may be et.al.1990;Rodriguez et.al.1994;De Diego et.al.present in the test sample will bind to the 3ABC 1997; Clavijo et.al.2004).proteinand will block the binding of the mAb-HRPO.Outbreaks of FMD repeatedly occur among After incubation, the plate is washed and the cattle, sheep and goats in various regions of Saudi chromogen (TMB) substrate is dispensed.After Arabia (Hafez et.al.1993).Camels are frequently incubation at room temperature (22±3°C) the color moved across the desert inside Saudi Arabia in an area development is stopped.Color development measured that experienced FMD outbreaks in cattle and smalloptically at a wavelength of 450 nm and results were ruminants so camels may play a possible role in the expressed as a percentage inhibition (PI) of the transmission of FMDV and may carry FMDV over controls and the test sera which calculated according very long distances and across borders.This study to the formula below: aimed to investigate the serological evidence of PI = 100 -(OD test sample/OD Neg.) x 100