Possible animal reservoirs for MERS-CoV need further exploration

ECDC comment

​​In the study by Perera, Wang et al. [1] 1 343 human and 625 animal sera samples originating from either Egypt or Hong Kong were analysed using two different serological tests for the presence of neutralising antibodies against MERS-CoV. Of 110 dromedary camels from Egypt, either 93.6% or 98.2% – depending on the test used –  returned positive test results for neutralising activity against MERS-CoV. In contrast, there was no detection of neutralising antibodies in any of the 815 human samples from Egypt or the 528 human samples from Hong Kong. Samples from Egyptian goats (13), sheep (5), water buffalos (8) or cows (25) were also negative for MERS-CoV antibodies, as were animal samples from Hong Kong (260 swine and 204 wild birds).

Comment, 10 September 2013:

The topic of possible animal reservoirs of MERS-CoV has been covered in a number of recent articles [1,2,3]. The very high percentage of dromedary camels found positive for MERS-CoV neutralising antibodies is in line with previous findings of high titres in dromedary camels from Oman [2].

These independent findings, which apply different methods for the detection of MERS-CoV neutralising antibodies, lead to the assumption that dromedary camels can be infected with a MERS-CoV-like virus that is likely to be constantly circulating at high levels among this animal population in Northern Africa and the Arabian Peninsula. The serological evidence is clear, but we have yet to see any direct detection or genetic characterisation of the responsible virus in the dromedaries.
 
The data on human serology is based on 815 samples from Egypt retrieved from a “community-based seroepidemiological study on influenza virus among healthy subjects in Cairo and the Nile Delta”. No neutralising or cross-reacting antibodies were found in the sampled human population. No information on risk factors, e.g. close contact with or handling of dromedaries, co-morbidities etc. within the sampled population, was provided. Further studies are urgently needed to characterise the strain of Coronavirus that is infecting dromedaries in order to determine whether it is MERS-CoV or a close relation. More research is also needed to determine if dromedaries are a source of MERS-CoV in the human population or are incidentally infected.

    References

    1. Perera, R.A., et al., Seroepidemiology for MERS coronavirus using microneutralisation and pseudoparticle virus neutralisation assays reveal a high prevalence of antibody in dromedary camels in Egypt, June 2013. Euro Surveill, 2013. 18(36). http://www.eurosurveillance.org/ViewArticle.aspxArticleId=20574
    2. Reusken, C.B., et al., Middle East respiratory syndrome coronavirus neutralising serum antibodies in dromedary camels: a comparative serological study. Lancet Infect Dis, 2013. http://www.thelancet.com/journals/laninf/article/PIIS1473-3099(13)70164-6/abstract
    3. Memish, Z.A., et al, Middle East respiratory syndrome coronavirus in bats, Saudi Arabia, Dispatch, Vol 19, No. 11, Nov 2013, http://wwwnc.cdc.gov/eid/article/19/11/13-1172_article.htm