Animal Model - Disease Models

Disease Models

Animal models serving in research may have an existing, inbred or induced disease or injury that is similar to a human condition. These test conditions are often termed as animal models of disease. The use of animal models allows researchers to investigate disease states in ways which would be inaccessible in a human patient, performing procedures on the non-human animal that imply a level of harm that would not be considered ethical to inflict on a human.

To serve as a useful model, a modeled disease must be similar in etiology (mechanism of cause) and function to the human equivalent. Animal models are used to learn more about a disease, its diagnosis and its treatment. For instance, behavioral analogues of anxiety or pain in laboratory animals can be used to screen and test new drugs for the treatment of these conditions in humans. A 2000 study found that animal models concorded (coincided on true positives and false negatives) with human toxicity in 71% of cases, with 63% for nonrodents alone and 43% for rodents alone.

Animal models of disease can be spontaneous (naturally occurring in animals), or be induced by physical, chemical or biological means. For example,

• The use of metrazol (pentylenetetrazol) as an animal model of epilepsy
• Immunisation with an auto-antigen to induce an immune response to model autoimmune diseases such as Experimental autoimmune encephalomyelitis
• Occlusion of the middle cerebral artery as an animal model of ischemic stroke
• Injection of blood in the basal ganglia of mice as a model for hemorrhagic stroke
• Infecting animals with pathogens to reproduce human infectious diseases
• Injecting animals with agonists or antagonists of various neurotransmitters to reproduce human mental disorders
• Using ionizing radiation to cause tumors
• Implanting animals with tumors to test and develop treatments using ionizing radiation
• Genetically selected (such as in diabetic mice also known as NOD mice)
• Various animal models for screening of drugs for the treatment of glaucoma
• The use of the ovariectomized rat in osteoporosis research
• Use of Plasmodium yoelii as a model of human malaria

The increase in knowledge of the genomes of non-human primates and other mammals that are genetically close to humans is allowing the production of genetically engineered animal tissues, organs and even animal species which express human diseases, providing a more robust model of human diseases in an animal model.