Animal research in recent times

In scientific terms, animals are multicellular organisms that consume organic material for growth, use oxygen for respiration, and pass the blastula period during embryonic development. Similarity in physical characteristics (phenotypes) and genetic characteristics (genotype) suggests strong evolutionary link between other animals and humans. This similarity is predominantly seen in mammals, which are animals that feed milk to their infants. Thus, research is greatly facilitated if animals are used as model organisms for trials of novel drugs or therapies. However, due to ethical and legal concerns and rapid advancements in biological sciences; the overall use of higher animals for research is likely to decline in the 21^st century.

No responsible researcher wants to harm animals in any way. In 1959, Russel and Burch introduced the 3 R’s of animal research: Replacement, Reduction, and Refinement. These principles were designed to serve as a foundation for the development of future alternatives to the use of animals in research. It was not until the 1980s, however, that legislative bodies across Europe and the United states began to develop committees and laws to govern the use of animals in research, which are largely based upon the three Rs.

The main purpose of animal usage in science is to test the physical or psychological reaction to the introduction of an abnormality; such as a mutant gene, a drug, modified light-dark cycle etc. The simplest animals to be widely used in research were the roundworm Caenorhabditis elegans; and the fruit fly Drosophila melanogaster; both of whom are small and easy to manipulate. These animals gave scientists massive amount of information on animal development, change in gene expression and behavior due to presence of chemicals such as alcohol, nicotine, growth factors, or diseases like insomnia and Alzheimer’s. The animal-genome sequencing procedures were perfected using these organisms. In the last century, to study a particular abnormality, many generations of these animals were needed and in great numbers. But nowadays, due to bioinformatics tools and sophisticated molecular biology techniques, the minimal requirement of number of animals has reduced. However, research on these animals is still done extensively and may continue throughout this century.

As the current century can provide better facilities, research on vertebrates has steadily increased. However, in the US, the Animal Welfare Act (AWA) regulates the treatment of selected animals. This act demands the report on the usage and treatment of cats, dogs, rabbits, nonhuman primates etc. But mice and rats are not under its legal protection. According to some estimates, about 100 million mice and rats are used for biomedical research annually in the US; comprising more than 95 percent of all vertebrates used in the country's laboratory. Being small, easy to maintain, sharing 90 percent of genes with humans and not being covered by the AWA regulations, mice and rats almost always become the initial platform for animal trials. Due to invention of bioinformatics and genetic engineering methods, it is now possible to accurately cut, paste or mutate a particular point in their billion base-pair genomes. Such modern techniques have contributed vastly to speed up research while decreasing the number of animals needed per study.

Since mice don't cough or sneeze; they are not a good model to study the transmission of coronavirus. However, a strain of mice with the name K18-hACE2 was developed that could produce the human version of ACE2 in its lung cells, which is the prerequisite of SARS-CoV-2 infection. Research on this strain gave scientists insight into disease mechanism and usage of steroids in mitigating the effects of COVID-19. 

As humans share about 99% of their genes with the chimpanzees; they and other primates are the most appropriate final candidates before any trial reaches human level. COVID-19 being an emergency situation, researchers around the world have made huge strides for its prevention and cure. Domestic cats, dogs, hamsters were found to be susceptible to coronavirus infection, raising questions regarding vectors of the disease. 

Syrian hamsters were used to study the efficiency of surgical masks. A study was conducted placing those hamsters in cages partitioned by surgical masks. This partition, which could block respiratory or airborne droplets, significantly reduced transmission to 25% and also decreased viral load in the infected hamsters. Although in small numbers, many monkey species such as macaques, marmosets, African green monkeys, moustached tamarins and squirrel monkeys are being used for animal trials of vaccines. After administration of the vaccines and intentional inoculation of SARS-CoV-2, the monkeys were examined for symptoms of infection and pneumonia; followed by inspection through dissection of lung tissues several days later. These tests helped researchers to test the efficacy of the vaccines and their optimum dosage. 

Immergence of novel experimental procedures is gradually reducing the number of animals needed for individual research. But regarding gene expression and metabolism, even the simple bacteria cannot be replicated by a computer yet. A mammal is very far-fetched indeed. Animal research and testing has helped save many human lives and is likely to do so throughout this century, in a humaner way.

 

- Anik Biswas

 

 

References - 

Annual reports of USDA Animal and Plant Health Inspection Service- https://www.nal.usda.gov/awic/animal-welfare-act

 

Animal research and COVID-19 -https://www.understandinganimalresearch.org.uk/news/communications-media/animal-research-and-covid-19/

 

US statistics - https://speakingofresearch.com/facts/statistics/

 

https://pubmed.ncbi.nlm.nih.gov/32472679/

 

Animals and COVID-19 - https://www.cdc.gov/coronavirus/2019-ncov/animals/pets-other-animals.html