ByDebananda S Ningthoujam
Updated 29 Nov 2020, 4:37 pm
The gold standard for Covid-19 testing has been and is still the RT-PCR test. The quicker screening method used widely is the rapid antigen test (RAT). However, an interesting development in Covid diagnosis that's already used in restricted contexts in some countries is the use of man's best friend in the detection of Covid-infected individuals quickly and, surprisingly, very rapidly. Across the globe, canines are being trained to detect the smell of COVID-19 infections. Scientists claim that dogs can detect the novel coronavirus with nearly 100 per cent accuracy and screen hundreds of people per hour in busy settings such as airports or sports stadiums. Needless to say that it is also a much cheaper method than standard methods such as RT-PCR.
According to Holger Volk, the University of Veterinary Medicine in Hanover, Germany, "No one is saying they can replace a PCR machine, but they could be very promising." Why are dogs so good in detecting scents, even peculiar whiffs of diseases tissues? Canine noses have 300 million scent receptors compared to just 5-6 million in humans. Sniffer dogs have been used for quite some time at airports to detect firearms, explosives, and drugs. Scientists have been successful in training dogs to detect malaria and some types of cancers.
How do sniffer dogs detect the peculiar COVID-19 smell?
How do sniffer dogs detect the peculiar COVID-19 smell? No one seems to know for sure yet but many suspect that Covid-infected people secrete sweat or other bodily secretions that contain a unique mix of volatile organic compounds (VOCs) that's the signature of Covid infections. Two sniffer dogs (among 10 trained dogs)-Valo, Kosii, Miina and ET-have been extensively used at the Helsinki airport, Finland to detect infected individuals with nearly 100% accuracy (HT online, Nov. 25, 2020). Subsequently, trained canines have screened 1,680 passengers at Beirut airport, Lebanon and detected 158 Covid-19 cases. The animals could identify negative results with 100% accuracy and detected 92% of positive cases (Nature, 26 November 2020). Similar projects are being pursued in many other countries including Australia, Britain, Chile, Dubai, France, and Germany.
Can we then use canines on a large scale around the world?
Can we then use canines on a large scale around the world? Not yet. First, the sample size studied so far is too small. Second, more reviewed results need to be shared with the global scientific community, so far only one exists, that of Folk's group in Germany [Jendrny, P. et al. BMC Infect. Dis. 20, 536 (2020)]. With more peer-reviewed studies with larger sample sizes, it's quite possible that, in the future, canines could be deployed not only at airports but also at border crossings, hospitals, care centres, and sporting & cultural events.
Denmark is one of the few countries famous for mink industry, rearing millions of mink (mink, a small mammal related to others, weasels, and ferrets) to produce mink fur to make the famous mink coats and other luxury wear. When the government found out in September that more than 200 mink-related coronavirus-infections, it decided to impose lockdown and cull 17 million-strong mink population. It's said that there has been spillover between humans and minks, first minks getting infected from farmworkers, then the virus got mutated in mink's body and then got reverse-jumped into humans again. SARS-CoV-2 coronavirus is supposed to be a zoonotic virus originating in a Chinese bat, then jumping into an intermediate host, and then spilling over into humans causing the COVID-19 pandemic. The initial spillover occurred due to the wanton destruction of wild habitats and livestock trade by greedy humans. And, now innocent animals like minks suffer from the impacts of adverse anthropogenic activities.
Scientists are particularly worried about one mink-associated mutation (Y453F) that affects the spike protein of the coronavirus and may impact the SARS-Cov-2 vaccines currently under development, as most of these vaccines target the spike protein. However, Astrid Iversen, virologist, University of Oxford says that there is no cause for alarm so far, as there is little evidence that the mutations would allow the virus to be more transmissible, or deadly, or jeopardize therapeutic agents and vaccines. Iversen says "The mink-associated mutations we know of are not associated with rapid spread, nor with any changes in morbidity or mortality (Nature, 19 November 2020)."
Nonetheless, we must be forewarned that we need to lessen our environmentally destructive activities such as habitat destruction, unhygienic and overcrowded domestic farms, wildlife trade, and live animal markets. Otherwise, deadly pandemics such as COVID-19 will soon emerge again due to spillover events of zoonotic viruses or other zoonotic pathogens.
Top vaccine candidates
Three are so far 4 frontrunner vaccine candidates: Pfizer, Moderna, Sputnik V, and AstraZeneca/Oxford vaccines. Of these Pfizer (with a German partner, BioNTech), and Moderna vaccines are based on the novel mRNA-based platforms and the Russian and British vaccines are based on the more well-established adenovirus vector-based platforms.
We are not taking into consideration the 4-5 Chinese vaccine candidates. Of these top vaccine candidates, only two have received licensure (approval)-Gamaleya (Sputnik-V) and Sinovac (CoronaVac)-without completing proper phase-3 trials.
Indian vaccine scenario
Both Pfizer and Moderna vaccines have purportedly shown efficacy rates of over 90%. Russia announced that its vaccine has 92% efficacy. These efficacies are indeed more than what's needed to get approval. US FDA sets the limit for approval as low as just 50%. But one is still not sure about the sample size of late-stage trials of some of these vaccines or the likelihood of rare adverse events that may be manifested in larger vaccinated populations. Moreover, we cannot still predict how the vaccine will perform in very elderly and very young individuals, and in pregnant women or small ethnic populations.
As of now, it seems that the Oxford vaccine may be most suited to the Indian scenario due to various reasons. First, both Moderna and Pfizer are unlikely to seek emergency use approval (EUA) before generating safety data for 50% of people they have recruited (this may take about 2 months). Second, there's vaccine nationalism: about 70-80% of Pfizer and Moderna vaccines have been pre-ordered by a few rich countries. Third, both these vaccines need ultra-cold storage facilities-Pfizer (-700C), Moderna (-200C), but the AstraZeneca vaccine can be stored, transported, and handled at normal refrigeration conditions (2-80C). Fourth, Serum Institute of India (SII), which is developing the Oxford vaccine in India, plans to sell it at $3-4 per dose, while for private organizations, the price for two doses may work out to around Rs. 500-600. SII says that the maximum price tag for 2 doses for the public will be only Rs. 1,000.
On the other hand, Pfizer and Moderna vaccines may cost around $20 and $25-40 respectively, which is quite high for most low-income nations. SII is hoping for phase-3 data by late December. The first doses of SII's CoviShield may be available for healthcare workers and the elderly by February 2021.
However, the general public may not have access to the vaccine till much later. As Gagandeep Kang (vaccine pioneer and the only Indian woman FRS) says there may be multiple waves of vaccination in India spread over a long time. This process may last 24 months or more to let 60-70 per cent of the Indian population to get 2 vaccine shots, separated by a gap of 3-4 weeks (India Today Web Desk, Nov. 17, 2020).
Meanwhile, we must not let our guards down and we must still strictly observe the non-pharmaceutical interventions such as the major SOPs of the use of face masks, physical distancing, and hand hygiene and avoidance of 3 Cs: crowded places, close-contact settings, and closed spaces (with poor ventilation).
The silver bullet for Covid-19 is an efficacious, safe, and affordable vaccine and/or drug. But we don't have it yet. But as Derek Thompson writes in The Atlantic magazine (Oct. 12, 2020), there are "bronze bullets abound." The 3 Ws (watch your distance, wear a mask, and wash your hands regularly) and 3 Cs (avoidance of crowded places, closed contact settings, and closed spaces) are some of these bronze bullets. At this critical point of the pandemic, it's we-hoi polloi, common people-who with our (in)appropriate behaviour will determine the trajectory of Covid-19 in Manipur. Once again I humbly appeal to fellow citizens to abide by the 3 Ws and 3 Cs guidelines strictly!
In addition, the public health authorities may consider a few things, if feasible: localized, focused lockdowns in specific areas, mass testing at containment zones and hotspots of infections, rapid contact tracing and isolation/quarantining of potentially infected cases/sick patients, weekly publications of Covid graphs with categories of infected people and mortalities, strengthening of healthcare facilities, timely palliative/supportive care and treatment of serious Covid (and non-Covid) cases, and clear and accurate messaging from a designated public health official (just one designated person) on a regular basis (say weekly, if not daily).
(The views expressed are the writer's own)
First published:29 Nov 2020, 7:31 am
mink mutationsniffer dogsCOVID-19 update
Debananda S Ningthoujam
The author teaches and studies microbial biochemistry and biotechnology at Manipur University