Thursday, 22 August 2013

MERS-CoV genetic sequences found in Taphozous perforatus bat

Profs Ziad Memish and Ian Lipkin, and a team of collaborators including researchers from the EcoHelath Alliance, have published, in Emerging Infectious Diseases, their discovery of viral sequences in the faecal pellet of an Egyptian tomb bat.
Taphozous perforatus bat
Photo courtesy of Dr Jonathan H. Epstein.

MERS-CoV was only found in 1 of 29 Taphozous perforatus (Egyptian tomb bat, see some more detail on these in my next post) animals. These and 67 other bats captured in mist nets for this study, were observed nesting in abandoned ruins.

Samples from Bisha, Unaizah and Riyadh (Kingdom of Saudi Arabia) were snap-frozen on site, collected during October 2012 and April 2013. The October shipment was opened and thawed by US customs. Samples included wing biopsy, blood, throat swab, rectal swab and faecal pellets were collected for testing. Apart from RNA virus testing  bats were speciated by DNA analysis (cytochrome B gene). The T. perforatus bat identity could not be confirmed genetically because there was no reference sequence on GenBank - but it was similar to another member of the genus.


Helicase, RNA-dependent RNA polymerase (RdRp) and nucleocapsid or envelope regions were targeted for amplification and sequencing. 227/1003  samples (22.6%) were positive for an alpha or beta-CoV. 

The find, represented by a phylogenetic tree using on a 181nt RNA sequence fragment from the RNA-dependent RNA polymerase gene (100% identical to a sequence from the index case in Bisha, betaCoV 2c EMC/2012 over this region), secures bats as the/a primary animal source. So long as there was no contamination at customs or that the sequence actually came from a food source. Not too likely for either of those. 

Obviously more work will need to be done to find more instances, complete the genome (or at least sequence larger genetic fragments to make everyone happy) and isolate infectious virus - but this finding is a significant step in confirming a starting point for understanding how humans get infected by the MERS-CoV.

It's a shame this new fragment of the RdRp does not overlap with that sequence from the recent South African "nearest match" to MERS-CoV. In adjacent regions of the RdRp though, the South African virus does seems more genetically distant than this T. perforatus find.

  Perhaps we can re-visit the transmission chain issue with a view to how bats might infect a (probable) secondary host - say the camel for now - I'd suggest that palm trees might have a role in this as well as a possible role in direct human infections if sap/dates/drinks were consumed by the most at risk groups; elderly men with underlying conditions. Perhaps this consumption even has a role in them developing a chronic kidney-related disease? I previously wrote a little about this 19th June and on risk in a post 28th July.