key: cord-304057-d2r92nji authors: Harrath, Rafik; Abu Duhier, Faisel M. title: Sero‐prevalence of Middle East respiratory syndrome coronavirus (MERS‐CoV) specific antibodies in dromedary camels in Tabuk, Saudi Arabia date: 2018-04-26 journal: J Med Virol DOI: 10.1002/jmv.25186 sha: doc_id: 304057 cord_uid: d2r92nji The Middle East Respiratory Syndrome Coronavirus (MERS‐CoV) is a novel Coronavirus which was responsible of the first case of human acute respiratory syndrome in the Kingdom of Saudi Arabia (KSA), 2012. Dromedary camels are considered as potential reservoirs for the virus and seem to be the only animal host which may transmit the infection to human. Further studies are required to better understand the animal sources of zoonotic transmission route and the risks of this infection. A primary sero‐prevalence study of MERS‐CoV preexisting neutralizing antibodies in Dromedary camel serum was conducted in Tabuk, western north region of KSA, in order to assess the seopositivity of these animals and to explain their possible role in the transmission of the infection to Human. One hundred seventy one (171) serum samples were collected from healthy dromedary camels with different ages and genders in Tabuk city and tested for specific serum IgG by ELISA using the receptor‐binding S1 subunits of spike proteins of MERS‐CoV. 144 (84,21%) of the total camel sera shown the presence of protein‐specific antibodies against MERS‐CoV. These results may provide evidence that MERS‐CoV has previously infected dromedary camels in Tabuk and may support the possible role of camels in the human infection. Blood sera were separated, diluted at 1:100 and analyzed for MERS-CoV specific antibodies using the anti-MERS-CoV ELISA Camel (IgG) kit manufactured by EUROIMMUN AG (Lübeck, Germany). This test is based on the recombinant MERS-CoV spike protein subunit-1 and has successfully been used by other authors evaluating MERS-CoV in camels. 16 Optical Density (OD) was measured at 450 nm using a MINDRAY MR-96 ELISA reader. Statistical analysis was performed on SPSS v. 22.0 software (SPSS Inc., Chicago, IL). Data were expressed as percentage for continuous variables, which were normally distributed, or as percentages of total for categorical variables. Pearson χ 2 test was used to assess intergroup significance. This research was ethically approved by the research ethic committee at the University of Tabuk. One hundred seventy one serum samples were collected from three areas in Tabuk A primary study was conducted in Tabuk instructions. This test has been successfully used and evaluated by many authors for MERS-CoV detection in camels. 11, 16, 17 Results have shown that a high number (85%) of dromedary camels from the different farms of Tabuk Riyadh and screened by ELISA test showed that 74% of the animals were found to have antibodies to MERS-CoV. 7 In the same study, 264 archived serum samples collected from dromedary camels from 1992 to 2010 in Riyadh and Kharj were also analyzed by ELISA and showed a high seroprevalence (92%) of MERS-CoV neutralizing antibodies. 7 Our data agree also with previous studies reporting wide antibody prevalence in camels in many countries, including Egypt and Oman. 12, 19 In another study conducted in Oman, all serum samples from 50 dromedary camels were positive for MERS-CoV specific antibodies. 12 Similar results were also reached from a larger study conducted in United Arab Emirates (UAE), where 500 dromedary camels' sera screened in 2013 revealed 96% seropositivity. 18 In Africa, an outbreak investigating serum samples for MERS-CoV assessment in camels has also shown similar results in Nigeria (94%), Tunisia (48.5%), and Ethiopia (96.3%). 20 Likewise, in a study conducted on 189 archived camel sera samples collected in 1997 from Egypt and between 1983 and 1984 from Sudan and Somalia, 81% were found to have neutralizing antibodies to MERS-CoV. 16 Similar results were also obtained in a study from Kenya. 17 While camels in the Middle East and Africa were highly exposed to MERS-CoV infection, camels from Europe and Australia which are geographically isolated were not exposed to the virus. 12 However, serum samples collected from 105 dromedary camels living in the archipelago of Canary Islands, between 2012 and 2013 showed that 14% have antibodies against MERS-CoV. 12 In another study carried out in the same islands, 170 dromedary camel sera were analyzed and only 4.1% were seropositive for MERS-CoV. Data showed that all the seropositive dromedary camels for MERS-CoV were all imported from Africa. In addition, 307 dromedary camels' sera collected from different regions between 2013 and 2014 in the Islands were all tested negative for specific MERS-CoV antibodies. 21 All these findings indicate that active MERS-CoV infection did not occur in the Canary Islands. 22 The same author explained the increase of the seropositivity in adult camels by the age range of the animals which were exposed for long time to the virus infection. 24 For young camels, specific MERS-CoV antibodies could be acquired from their mothers as it was reported by Kamber 25 who suggests that maternal IgG antibodies in camels are acquired through the colostrum intake during the first 24 h post-parturition and not via the trans-placental route. After 24 h, antibody levels in the dam's milk decrease rapidly, and IgG levels in serum cease to rise. 25 We also suggest that maternal antibodies might not have been sufficient to mediate protective immunity for them. Animals would then be exposed to new MERS-CoV infection and specific antibodies would consequently increase in 1-2 years after, which can explain the higher seroprevalence in juveniles then in adults. The predominance of viral antibodies in young camels could also be explained by animal exposure to the virus few times postparturition and not by mother immunity, which will stimulate antibody secretion in the blood. In the two last possibilities, young camels could contract viral infection after 2012, period of epidemic MERS circulation in KSA, and production of specific antibodies would consequently increase in some months after birth. Respiratory specimens, as nasal swabs, and rectal swabs will be required for analysis to know whether anti-MERS antibodies are issued from recent viral infection. In relation to sex, our results have shown a high seropositivity in both males (82,8%) and females (85.9%) without a significant difference between the two genders. This information was not reported in previous studies and indicates that the sex cannot be a limiting factor in camel's infection by the virus. In conclusion, our findings in Dromedary camel's sera, even if limited to serology, constitute a strong argument suggesting that MERS-CoV has previously infected dromedary camels in Tabuk region. We speculate that Dromedary camels may support the role of these animals as potential reservoirs for human infection but we cannot confirm this relationship from the current data alone. Further studies including more animals and respiratory samples are needed for a larger evaluation of camel population in this region. In addition, a whole genome sequencing of camel MERS-CoV is required to confirm its incrimination in human infection. 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Seroprevalence of Middle East respiratory syndrome coronavirus (MERS-CoV) specific antibodies in dromedary camels in