COVID-19 vaccines for humans number 30, while only three vaccines are available for animals, even though many species have been infected.
“Several animal species have been predicted and found to be susceptible to SARS-CoV-2,” says Suresh V. Kuchipudi, interim director of the Animal Diagnostic Laboratory at the Huck Institutes of Life Sciences. But the risk remains unknown for many animals in several parts of the world, he says. “Therefore, there is an urgent need to monitor the SARS-CoV-2 exposure of high-risk animals in different parts of the world.”
In June, India introduced Ancovax, its first COVID-19 vaccine for animals. The development came a year after the nation reported that the virus had infected eight Asiatic lions, with two of them dying. While 30 COVID-19 vaccines for humans have been approved for general or emergency use across the world, Ancovax is only the third such vaccine for animals. The first, named Carnivac-Cov, was registered by Russia in March last year, followed by another vaccine four months later, developed by Zoetis, a U.S. pharmaceutical company.
Christina Lood, a Zoetis spokesperson, says the company has donated over 26,000 doses of its animal vaccine to over 200 zoos – in addition to 20 conservatories, sanctuaries and other animal organizations located in over a dozen countries, including Canada, Chile and the U.S. The vaccine, she adds, has been administered to more than 300 mammalian species so far.
“At least 75 percent of emerging infectious diseases have an animal origin, including COVID-19,” says Lood. “Now more than ever before, we can all see the important connection between animal health and human health."
The Dangers of COVID-19 Infections among Animals
Cases of the virus in animals have been reported in several countries across the world. As of March this year, 29 kinds of animals have been infected. These include pet animals like dogs, cats, ferrets and hamsters; farmed animals like minks; wild animals like the white-tailed deer, mule deer and black-tailed marmoset; and animals in zoos and sanctuaries, including hyenas, hippopotamuses and manatees. Despite the widespread infection, the U.S. Centres for Diseases Control and Prevention (CDC) has noted that “we don’t yet know all of the animals that can get infected,” adding that more studies and surveillance are needed to understand how the virus is spread between humans and animals.
Leyi Wang, a veterinary virologist at the Veterinary Diagnostic Laboratory, University of Illinois, says that captive and pet animals most often get infected by humans. It goes both ways, he says, citing a recent study in Hong Kong that found the virus spread from pet hamsters to people.
Wang’s bigger concern is the possibility that humans or domestic animals could transmit the virus back to wildlife, creating an uncontrollable reservoir of the disease, especially given the difficulty of vaccinating non-captive wild animals. Such spillbacks have happened previously with diseases such as plague, yellow-fever, and rabies.
It’s challenging and expensive to develop and implement animal vaccines, and demand has been lacking as the broader health risk for animals isn’t well known among the public. People tend to think only about their house pets.
In the past, other human respiratory viruses have proven fatal for endangered great apes like chimpanzees and gorillas. Fearing that COVID-19 could have the same effect, primatologists have been working to protect primates throughout the pandemic. Meanwhile, virus reservoirs have already been created among other animals, Wang says. “Deer of over 20 U.S. states were tested SARS-CoV-2 positive,” says Wang, pointing to a study that confirmed human-to-deer transmission as well as deer-to-deer transmission. It remains unclear how many wildlife species may be susceptible to the disease due to interaction with infected deer, says Wang.
In April, the CDC expressed concerns over new coronavirus variants mutating in wildlife, urging health authorities to monitor the spread of the contagion in animals as threats to humans. The WHO has made similar recommendations.
Challenges to Vaccine Development
Zoetis initiated development activities for its COVID-19 vaccine in February 2020 when the first known infection of a dog occurred in Hong Kong. The pharmaceutical giant completed the initial development work and studies on dogs and cats, and shared their findings at the World One Health Congress in the fall of 2020. A few months later, after a troop of eight gorillas contracted the virus at the San Diego Zoo Safari Park, Zoetis donated its experimental vaccine for emergency use in the great ape population.
Zoetis has uniquely formulated its COVID-19 vaccine for animals. It uses the same antigen as human vaccines, but it includes a different type of carrier protein for inducing a strong immune response. “The unique combination of antigen and carrier ensures safety and efficacy for the species in which a vaccine is used,” says Lood.
But it’s challenging and expensive to develop and implement animal vaccines, and demand has been lacking as the broader health risk for animals isn’t well known among the public. People tend to think only about their house pets. “As it became apparent that risk of severe disease for household pets such as cats and dogs was low, demand for those vaccines decreased before they became commercially available,” says William Karesh, executive vice-president for health and policy at EcoHealth Alliance. He adds that in affected commercial mink farms, the utility of a vaccine could justify the cost in some cases.
Although scientists have made tremendous advances in making vaccines for animals, Kuchipudi thinks that the need for COVID-19 vaccines for animals “must be evaluated based on many factors, including the susceptibility of the particular animal species, health implications, and cost.”.
Not every scientist feels the need for animal vaccines. Joel Baines, a professor of virology at Cornell University’s Baker Institute for Animal Health, says that while domestic cats are the most susceptible to COVID-19, they usually suffer mild infections. Big cats in zoos are vulnerable, but they can be isolated or distanced from humans. He says that mink farms are a relatively small industry and, by ensuring that human handlers are COVID negative, such outbreaks can be curtailed.
Baines also suggests that human vaccines could probably work in animals, as they were tested in animals during early clinical trials and induced immune responses. “However, these vaccines should be used in humans as a priority and it would be unethical to use a vaccine meant for humans to vaccinate an animal if vaccine doses are at all limiting,” he says.
William Karesh, president of the World Animal Health Organization Working Group on Wildlife Diseases, says the best way to protect animals is to reduce their exposure to infected people.
William Karesh
In the absence of enough vaccines, Karesh says that the best way to protect animals is the same as protecting unvaccinated humans - reduce their exposure to infected people by isolating them when necessary. “People working with or spending time with wild animals should follow available guidelines, which includes testing themselves and wearing PPE to avoid accidentally infecting wildlife,” he says.
The Link between Animal and Human Health
Although there is a need for animal vaccines in response to virus outbreaks, the best approach is to try to prevent the outbreaks in the first place, explains K. Srinath Reddy, president of the Public Health Foundation of India. He says that the incidence of zoonotic diseases has increased in the past six decades because human actions like increased deforestation, wildlife trade and animal meat consumption have opened an ecological window for disease transmission between humans and animals. Such actions chip away at the natural barriers between humans and forest-dwelling viruses, while building conveyor belts for the transmission of zoonotic diseases like COVID-19.
Many studies suggest that the source of COVID-19 was infected live animals sold at a wet market in China’s Wuhan. The market sold live dogs, rats, porcupines, badgers, hares, foxes, hedgehogs, marmots and Chinese muntjac (small deer) and, according to a study published in July, the virus was found on the market’s stalls, animal cages, carts and water drains.
This research strongly suggests that COVID-19 is a zoonotic disease, one that jumps from animals to humans due to our close relationship with them in agriculture, as companions and in the natural environment. Half of the infectious diseases that affect people come from animals, but the study of zoonotic diseases has been historically underfunded, even as they can reduce the likelihood and cost of future pandemics.
“We need to invest in vaccines,” says Reddy, “but that cannot be a substitute for an ecologically sensible approach to curtailing zoonotic diseases.”
Silkworm silk is fragile, which limits its uses, but a few extra genes can help.
Today, biomimetics is everywhere. Shark-inspired swimming trunks, gecko-inspired adhesives, and lotus-inspired water-repellents are all taken from observing the natural world. After millions of years of evolution, nature has quite a few tricks up its sleeve. They are tricks we can learn from. And now, thanks to some spider DNA and clever genetic engineering, we have another one to add to the list.
The elusive spider silk
We’ve known for a long time that spider silk is remarkable, in ways that synthetic fibers can’t emulate. Nylon is incredibly strong (it can support a lot of force), and Kevlar is incredibly tough (it can absorb a lot of force). But neither is both strong and tough. In all artificial polymeric fibers, strength and toughness are mutually exclusive, and so we pick the material best for the job and make do.
Spider silk, a natural polymeric fiber, breaks this rule. It is somehow both strong and tough. No surprise, then, that spider silk is a source of much study.The problem, though, is that spiders are incredibly hard to cultivate — let alone farm. If you put them together, they will attack and kill each other until only one or a few survive. If you put 100 spiders in an enclosed space, they will go about an aggressive, arachnocidal Hunger Games. You need to give each its own space and boundaries, and a spider hotel is hard and costly. Silkworms, on the other hand, are peaceful and productive. They’ll hang around all day to make the silk that has been used in textiles for centuries. But silkworm silk is fragile. It has very limited use.
The elusive – and lucrative – trick, then, would be to genetically engineer a silkworm to produce spider-quality silk. So far, efforts have been fruitless. That is, until now.
We can have silkworms creating silk six times as tough as Kevlar and ten times as strong as nylon.
Spider-silkworms
Junpeng Mi and his colleagues working at Donghua University, China, used CRISPR gene-editing technology to recode the silk-creating properties of a silkworm. First, they took genes from Araneus ventricosus, an East Asian orb-weaving spider known for its strong silk. Then they placed these complex genes – genes that involve more than 100 amino acids – into silkworm egg cells. (This description fails to capture how time-consuming, technical, and laborious this was; it’s a procedure that requires hundreds of thousands of microinjections.)
This had all been done before, and this had failed before. Where Mi and his team succeeded was using a concept called “localization.” Localization involves narrowing in on a very specific location in a genome. For this experiment, the team from Donghua University developed a “minimal basic structure model” of silkworm silk, which guided the genetic modifications. They wanted to make sure they had the exactly right transgenic spider silk proteins. Mi said that combining localization with this basic structure model “represents a significant departure from previous research.” And, judging only from the results, he might be right. Their “fibers exhibited impressive tensile strength (1,299 MPa) and toughness (319 MJ/m3), surpassing Kevlar’s toughness 6-fold.”
A world of super-materials
Mi’s research represents the bursting of a barrier. It opens up hugely important avenues for future biomimetic materials. As Mi puts it, “This groundbreaking achievement effectively resolves the scientific, technical, and engineering challenges that have hindered the commercialization of spider silk, positioning it as a viable alternative to commercially synthesized fibers like nylon and contributing to the advancement of ecological civilization.”
Around 60 percent of our clothing is made from synthetic fibers like nylon, polyester, and acrylic. These plastics are useful, but often bad for the environment. They shed into our waterways and sometimes damage wildlife. The production of these fibers is a source of greenhouse gas emissions. Now, we have a “sustainable, eco-friendly high-strength and ultra-tough alternative.” We can have silkworms creating silk six times as tough as Kevlar and ten times as strong as nylon.
We shouldn’t get carried away. This isn’t going to transform the textiles industry overnight. Gene-edited silkworms are still only going to produce a comparatively small amount of silk – even if farmed in the millions. But, as Mi himself concedes, this is only the beginning. If Mi’s localization and structure-model techniques are as remarkable as they seem, then this opens up the door to a great many supermaterials.
Nature continues to inspire. We had the bird, the gecko, and the shark. Now we have the spider-silkworm. What new secrets will we unravel in the future? And in what exciting ways will it change the world?
This article originally appeared on Freethink, home of the brightest minds and biggest ideas of all time.
