Inherent Suffering:

Non-Human ‘Models’ of Human Diseases and Conditions

By Crystal Miller-Spiegel

These days, it seems that researchers will attempt to induce into nonhuman animals virtually any conceivable human disease that exists, many of which do not even naturally occur in the species of animals being used. Animals are manipulated to cause or mimic diseases through genetic tinkering (i.e., inserting, deleting, or otherwise inactivating the function of genes, etc.) or physical, chemical, and/or biological means. In other cases, naturally affected animals are bred to produce more animals with a specific disease or trait. Researchers try to use these animals, or so-called ‘models,’ to learn about the dynamics of diseases, lifestyle or environmental effects on the disease, or treatment methods, and hope that the findings will relate in some way to people. Because the onset of the disease is intentional, and researchers want to understand its process, the animals are not usually treated as human patients would be. Their suffering is often part of study protocols.

Many researchers, companies, and academic institutions have also sought patents on not just the methods used to make animals suffer from a disease but also the animals themselves. Patents on actual animals can be very lucrative if they become in demand for biomedical and testing laboratories. For example, the first patent issued on an animal came in 1988 and was granted to Harvard University for “Transgenic non-human mammals” (US Patent Number 4,736,866), involving mice genetically manipulated to develop cancers mimicking human diseases. These mice have been trademarked as the “Oncomouse” and marketed widely by DuPont, which funded the Harvard research and, hence, owns rights to the patent. DuPont has also worked with Charles River Laboratories, one of the world’s largest breeders and dealers of animals for research and testing, to continue developing the Oncomouse and other cancer-prone mice.

Indeed, such animals have proven to be big business for companies like Charles River, which has an online “research models” catalog from which researchers can order a variety of animals under such headings as, “Disease Models” and “Immunodeficient Models.” Charles River’s Disease Models Program offers 11 types of animals who can have one or more health problems related to their cardiovascular systems, metabolism, renal function, or oncology (i.e., development of cancer). Animals are labeled as “Diet Induced Obesity [DIO] Rats,” “Spontaneously Hypertensive Heart Failure [SHHF] Rats” and “Stroke Prone Rats,” to name a few. As with the Oncomouse, many animals sold by Charles River and other companies have resulted from experiments done at universities, government institutions, and private companies.

Another large dealer, The Jackson Laboratory, states on its website, “Each year, the Laboratory supplies approximately 2 million JAX® Mice to the global research community from more than 2,700 varieties, 97% of which are available only from The Jackson Laboratory.” The Jackson Laboratory maintains an extensive website database of mice who are available for purchase or are “under development.” The disclaimer to those ordering animals states, “…[W]e cannot guarantee a strain's phenotype will meet all expectations…. …[W]e suggest ordering and performing tests on a small number of mice to determine suitability for your particular project.”

Other major companies that sell ‘animal models’ to laboratories include Taconic and Harlan. Taconic sells over 50 lines of transgenic animals and also sells surgically-modified rats and mice, including animals whose glands or organs have been removed or whose brains have been injected with a neurotoxin to cause damage in order to study the neurodegenerative disease process related to Parkinson’s Disease. According to its website, Harlan “offers over 200 stocks and strains of mice, rats, hamsters, guinea pigs, gerbils, rabbits, cats, and dogs.”

Animals have been altered in countless ways in attempts to learn more about human diseases and conditions, and such studies are commonly funded by the U.S. government.: Searches for rabbit, non-human primate, and mice ‘models’ using the National Institutes of Health’s Computer Retrieval of Information on Scientific Projects (CRISP) database of federally-funded research for the year 2005 produced studies of wide-ranging topics.

For example, a search under the phrase “rabbit model” yielded 72 research projects (a search under “rabbit” resulted in 1521 hits). Rabbits are used in studies to model human syphilis, carpal tunnel syndrome, intoxication of ricin and Shiga toxin, Lyme Disease, tuberculosis infection, periodontal disease and diabetes, liver cancer, heart failure, and genetic heart disorders, among others.

“Primate model” yielded 137 hits (searching for a particular species, such as Macaca mullata resulted in 573 hits, “monkey model” returned 35 projects, and “primate” yielded 693). The “primate model” search demonstrated that monkeys are used in government-funded experiments as ‘models’ for AIDS and tuberculosis (both as separate and combined diseases), cocaine addiction, genital ulcers, brain damage, fetal alcohol syndrome, and the list goes on and on.

For mice, a search under “murine model” produced 434 studies (“mouse model” found 1652, and “mouse” yielded a whopping 15,144 studies, though some of them did not involve live animals but utilized cells, tissues, or other samples). A quick glance at the list of funded projects show that mice are used as ‘models’ for monkey B virus infections, HIV, hepatitis C, asthma, Chlamydia and arthritis (combined), pancreatic and prostate cancer , squamous cell carcinoma (with human tumors transplanted into mice), West Nile virus, Escherichia coli infection, peanut allergies, and many, many more.

Scientists in laboratories continually overstep the boundaries of nature. The creation of chimeras—non-human animals who are comprised of two or more cells or tissues of different genetic composition (i.e., of different species)—has only recently gotten attention from the media but has in fact been happening for years. In the April 2005 National Academy of Sciences report, Guidelines for Human Embryonic Stem Cell Research, “interspecies mixing,” or the transfer of human stem cells into animals, is discussed, and it appears that, for the authors of the report, the more ‘human’ the animal, the more cause for concern. Some examples of chimeras include: mice with human brain cells, pigs with human blood, and the transplantation of human fetal organ tissue derived from aborted human fetuses into young, immunocompromised mice.

In analyzing attempts to model human diseases and conditions by using non-human animals, some scientists do admit the difficulty in applying results from animals in laboratories to everyday people. As author Timothy A. Cudd of Texas A&M University stated in the June 2005 issue of Experimental Biology and Medicine, “Because prenatal alcohol exposure causes damage by multiple mechanisms, depending on dose, pattern, and timing of exposure, and because no species of animal is the same as the human, the choice of which animal model to use is complicated.”

In a carefully titled review paper, “Why Do Animal Models (Sometimes) Fail to Mimic Human Sepsis?” in the journal Critical Care Medicine published in 2004 (Vol. 32, No. 5), Charles T. Esmon stated, “…[S]ome of the differences between animal models and humans preclude direct extrapolation from the animal studies to the [human] patient….” He also cited several factors related to this, in his words, “failure”: the use of different infective agents, age differences (i.e., young adult animals are used in experiments, but many human patients are either neonates or older adults), secondary health problems in the human patient that are not present in the animals (e.g. high blood pressure, cancer, diabetes, immune suppression), treatment timing, dosage differences, organ infection vs. blood infection, “different dose-dependent efficacies,” “differences in the use and effectiveness of antibiotics,” and “lack of intensive care in the animal studies” (emphasis added.) Esmon also notes confounding environmental conditions in laboratories that are not present in human hospitals: “…[R]odents and baboons are housed in feces-contaminated environments. Many of the animals used for studies of sepsis are coprophagous (i.e, ingest their own feces), potentially allowing the development of resistance [to induced infections]….”

Researchers from the Vanderbilt University Medical Center also describe problems with animal ‘models’ in their aptly but not concisely titled article, “The Use of Animal Models in the Study of Complex Disease: All Else is Never Equal or Why Do So Many Human Studies Fail to Replicate Animal Findings?” published in the journal Bioessays in 2004 (Vol. 26, No. 2). Though they support the use of animal ‘models,’ the authors cite the following problems: “…[T]he design of animal studies automatically controls many variables that can confound human studies”; “…[I]n human studies, it is impossible to control for many intrinsic (i.e., genetic) and extrinsic (i.e., environmental) factors”; “…[T]he phenotypes studied in animals are not truly identical to human disease but are limited representations of them”; “…[G]enetic manipulations in animal models are often extreme—gene titration or knockouts may be more severe than one would see in most human populations”; and “In most cases, animal studies do not assess the role of naturally occurring variation and its effects on phenotypes.”

Though researchers acknowledge that humans are truly the gold standard when it comes to studying human diseases, there are variations within the human species as well. Fortunately, most people are protected from being used in invasive and harmful research, but animals obviously are not. Researchers view the use of non-human animals as a primary means of learning about human disease, but this can also lead them down the wrong path, resulting in more harm to people and other animals.

Miller-Spiegel, Crystal. (Summer 2005). AV Magazine. Page 6-7.

Print View

Web ViewText Size: