Diseases of humans and other mammals are often studied in model organisms such as rats and mice. Rats and mice have been used because they grow and reproduce relatively rapidly for mammals and are less expensive to maintain than other mammals. However, rats and mice are not cheap to maintain and their care and use has come under increasing regulation. The use of insect models as alternatives has become more attractive as we learn more about insect physiology and the relationship between insect and mammalian genes and physiology.
The Madagascar Hissing Cockroach, Gromphadorhina portentosa, has emerged as an alternative model system for the study of infectious bacteria. Hissing cockroaches are large enough to collect adequate tissue and blood samples. They are not as mobile and easier to manipulate than faster moving cockroaches such as the American Cockroach. They are relatively inexpensive to grow and maintain. They reproduce rapidly and can be maintained in large colonies.Madagascar cockroaches can live up to 5 years and are known to have well developed immune systems. The Toll receptors of cockroaches (that recognize foreign bacteria and other invaders) are similar to receptors in mammals. Cockroaches have hemocytes that are similar to mammalian neutrophils. These cell types can engulf invading bacteria and destroy them. However some bacteria, such as some Burkholderia species, are not destroyed inside these phagocytic cells but have the ability to reproduce. Can these bacteria infest Madagascar cockroaches cells? If so, Madagascar cockroaches could be a useful model for studying these bacteria.
Madagascar cockroach hemocytes can indeed serve as hosts for Burkholderia species of bacteria as reported in BMC Microbiology*. Burkholderia pseudomallei, B. mallei and B. thailandensis, bacteria that replicate inside mammalian phagocytic cells, are capable of invading and replicating in phagocytic cells of hissing cockroaches. Many of the same factors that lead to virulence in mammals are used by bacteria to successfully colonize insect cells. Studying these factors in Madagascar Cockroaches could lead to more rapid identification of the genes and molecular factors that make these bacteria virulent and provide a model system to study agents and strategies that can prevent or limit infection.
* The Madagascar hissing cockroach as a novel surrogate host for Burkholderia pseudomallei, B. mallei and B. thailandensis. BMC Microbiology 2012, 12:117