A Culex univittatus under magnification, one of the arbovirus vectors in South Africa.

Loki Snyman, Durban Natural Science Museum

Finally, after a long waiting period, punctuated by administrative rushing, the NSFC-sponsored -80˚C ultra-low freezer arrived at the Durban Natural Science Museum (DNSM) Research Centre. You may have heard of ultra-low freezers in the news lately as they keep vaccines very cool. At the DNSM it is not vaccines that will fill the freezer, but mosquitoes. It is also not the mosquitoes that requires preservation, but another smaller foe hiding within the mosquitoes – viruses…

The entomology department of DNSM started a mosquito surveillance programme in Durban and has been steadily collecting mosquitoes in parks and reserves throughout the metro. The surveillance programme is a multi-institutional collaboration looking at the diversity of mosquitoes in various habitats and the pathogens they might be transmitting to unsuspecting animals and humans. Since August last year we have identified close to 3000 mosquitoes and at least 130 specimens comprising 25 species, all with subsamples for molecular work, have been formally incorporated into the DNSM collection. There are some additional specimens awaiting identification confirmation from experts elsewhere in South Africa which will be incorporated in due time.

Durban is situated in the eastern tropical corridor of South Africa, meaning that it not only has wonderful beach days, but a rich diversity of bloodsucking arthropods, and with them comes an array of tropical diseases, including parasites, worms and viruses. For this reason, mosquitoes are not really loved by humans and mosquito specific traps, especially when using dry ice as lures, ensures the collection of more mosquitoes than needed for museum collections. The rest can then be used to look for the pathogens they might harbour. While detecting some of these pathogens might require only a microscope and a needle or two, other pathogens require a cold chain and very secure laboratories.

Detection of viruses requires exactly that. To increase the chances of the detection and subsequent identification of arthropod-borne viruses, or arboviruses for short, the mosquitoes need to be freeze-killed then identified and sorted on ice-blocks – these are also kept super cool – then stored at -80˚C until shipment (with appropriate Section 20 permits in place of course…) to a facility with laboratories capable of processing the mosquitoes. The ultra-low freezer has thus enabled DNSM to collaborate with Professor Felicity Burt at University of the Free State, who specialises in looking for such arboviruses. Thanks NSCF!