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Adding to the list of studies (see here, here, & here) that have found evidence of MERS coronavirus infection in dromedary camels across a wide swath of the Middle East (including Oman, Saudi Arabia, the UAE, Jordan, Qatar, Spain, and Egypt) we now have a study conducted on camels from Kenya, a region that exports many animals to the Arabian peninsula and Egypt for slaughter.
The authors tested blood samples taken from farmed or nomadic camels and archived serum samples obtained from the International Livestock and Research Institute (ILRI) (Nairobi, Kenya).
Of 774 dromedaries tested, a total of 228 (29.5%) were rated MERS-CoV positive by the rELISA testing. Younger camels were shown to have the lowest levels of antibodies, and are most likely to carry the live virus.
Given that few camels are exported from the Arabian peninsula to the horn of Africa, the finding of high levels of MERS antibodies in East African dromedaries may suggest local acquisition of the virus. A finding that may lead to a better understanding of the natural ecology and history of the MERS coronavirus.
Victor M. Corman1, Joerg Jores1, Benjamin Meyer1, Mario Younan, Anne Liljander, Mohammed Y. Said, Ilona Gluecks, Erik Lattwein, Berend-Jan Bosch, Jan Felix Drexler, Set Bornstein, Christian Drosten , and Marcel A. Müller
Dromedary camels are a putative source for human infections with Middle East respiratory syndrome coronavirus. We showed that camels sampled in different regions in Kenya during 1992–2013 have antibodies against this virus. High densities of camel populations correlated with increased seropositivity and might be a factor in predicting long-term virus maintenance.
The materials and methods section of the dispatch is lengthy and detailed, and will be of most interest to researchers, so I’ve skipped ahead to their wrap up:
The present study showed that dromedary camels from Kenya have antibodies against MERS-CoV, which complements the current finding that MERS-CoV is a common pathogen in dromedary camel populations (5,6,8,9,13). Our finding of MERS-CoV antibodies in dromedary camels as early as 1992 is consistent with findings of a recent report from Saudi Arabia, which suggested that MERS-CoV has been circulating in dromedary camels for ≥20 years (5).
To project and potentially control virus spread, the public health community must understand factors determining virus maintenance. Our group and others have demonstrated that young dromedary camels have lower seroprevalences and are more likely to carry infectious virus (5,6). Similar observations have been made for coronaviruses in their original chiropteran hosts wherein strong virus amplification occurred soon after the time of parturition (15). Young, immunologically naive animals may thus facilitate virus amplification in dromedary camel populations.
We also demonstrated that dromedary camel population density shows a positive correlation with MERS-CoV seropositivity, which suggests efficient MERS-CoV maintenance or spread if herd density is high. Different types of animal husbandry in the Northeastern and Eastern regions of Kenya might be better predictors of virus transmission among camels. Dromedary camels in this area are often nomadic following rainfall patterns, and are taken across borders into neighboring countries, such as Ethiopia, for trade purposes (13). The observed increase in seropositivity from the Western region to the Northeastern and Eastern regions could be attributed to increased animal-to-animal contact in cross-border dromedary camel metapopulations.
Conversely, dromedary camels that originated in the Northeastern region but had been held in isolation since 1998 were negative for MERS-CoV antibodies, which is consistent with absence of antibodies in dromedary camels bred in isolation in Dubai (6). The combination of nomadic husbandry for a large population and presence of young virus-susceptible animals might facilitate virus maintenance. However, our retrospective study with archived samples could not assess hypotheses for each of the individual variables to determine their relative and absolute degrees of influence on virus circulation.
Because exportation of dromedary camels is largely unidirectional from eastern Africa into the Arabian Peninsula (11), our findings might facilitate the search for more ancestral MERS-CoV variants to clarify the natural history of acquisition of MERS-CoV by dromedary camels and its putative transmission to humans. Our recent finding of a MERS-CoV ancestor in bats from South Africa (3) highlights the need for wider investigations of viral reservoirs. The fact that no human MERS cases have been observed in eastern Africa could indicate less transmissibility of viruses in regional lineages or lack of detection and reporting of cases. Serosurveys of persons handling dromedary camels in this region could help to determine whether silent or unrecognized infections are being maintained in humans.