Although it certainly seems longer, it has been just over a year since we saw the first real evidence linking camels to the MERS-CoV virus (see Lancet: Camels Found With Antibodies To MERS-CoV-Like Virus). Since then, as testing procedures have matured and been deployed, we’ve seen a steady stream of studies showing that many Middle Eastern dromedaries either carry the live virus, or antibodies indicating prior infection.
While bats are still a prime suspect as the reservoir host for this emerging coronavirus, camels increasingly are viewed as an important intermediate host, and possible bridge to infecting humans (see WHO Update On MERS-CoV Transmission Risks From Animals To Humans & FAO: `Stepped Up’ Investigations Into Role Of Camels In MERS-CoV).
While human cases have only originated on the Arabian peninsula, that region imports tens of thousands of camels each year from the Horn of Africa, leading some to suspect the actual `source’ of the MERS coronavirus might come from the East African nations of Somalia, Kenya, or Sudan.
Last May, in EID Journal: MERS Antibodies In Camels – Kenya 1992-2013, we saw a study using archived camel blood samples going back 20 years that found MERS antibodies were circulating in Kenya as early as 1992. Today, we’ve a new study that pushes back the clock at least another 10 years.
Volume 20, Number 12—December 2014
Marcel A. Müller1 , Victor Max Corman1, Joerg Jores, Benjamin Meyer, Mario Younan, Anne Liljander, Berend-Jan Bosch, Erik Lattwein, Mosaad Hilali, Bakri E. Musa, Set Bornstein, and Christian Drosten
To analyze the distribution of Middle East respiratory syndrome coronavirus (MERS-CoV)–seropositive dromedary camels in eastern Africa, we tested 189 archived serum samples accumulated during the past 30 years. We identified MERS-CoV neutralizing antibodies in 81.0% of samples from the main camel-exporting countries, Sudan and Somalia, suggesting long-term virus circulation in these animals.
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You’ll want to read the entire paper for methods, materials, and their detailed findings. In the conclusion, the authors write:
MERS-CoV sequences from camels in Saudi Arabia and Qatar were closely related to sequences found in humans and did not show major genetic variability that would support long-term evolution of MERS-CoV in camels (10,11). The MERS-CoV sequence from a camel in Egypt was phylogenetically most distantly related to all other known camel-associated MERS-CoVs but closely related to the early human MERS-CoV isolates (10). An urgent task would be to characterize the diversity of MERS-related CoV in other camels in Africa to elucidate whether the current epidemic MERS-CoV strains have evolved toward more efficient human transmissibility.
The existence of unrecognized human infections in African or Arabian countries in the past cannot be ruled out. Resource-limited African countries that have been exposed to civil unrest, such as Somalia and Sudan, are not likely to diagnose and report diagnostically challenging infections resembling other diseases. The lack of MERS-CoV antibodies in a small cohort serosurvey in Saudi Arabia did not suggest the long-term circulation of MERS-CoV in humans on the Arabian Peninsula (15).
Large serosurveys in countries where camels are bred and traded, especially in eastern Africa, are needed to explore the general MERS-CoV seroprevalence in camels and humans, particularly humans who have close contact with camels. Such serosurveys could provide the data needed to ascertain whether MERS-CoV has been introduced into, but unrecognized in, the human population on the African continent.