Reemergence of old diseases that were thought to be under control (in certain countries), was an unpleasant shock to the health care community. This illustrated an important principle that disease patterns change because of :
I. Organisms change,
II. Human activity change to create new opportunities for organisms to cause disease.
In the mid-20th century, insecticides and other measures eliminated malaria from US and Europe. Many public health workers were optimistic over reducing the global burden of many vector-borne diseases, such as : Malaria, Chagas, Yellow fever, and Dengue fever, by spraying chemicals. With the comeback of these diseases, occurring more widely and more frequently than they have in recent decades, Frank H. Collins of the University of Notre Dame in Indiana, said in retrospect that it was naive of us to think that we could eradicate the mosquito by chemical attack. Many insect populations, especially in the tropics proved too hardy, as evident by the come back of diseases in regions that were considered free of such. Failure to control these vector-borne disease with chemicals, lead scientist to research alternate ways to target the problem.
Molecular Biologist Anthony James of University of California in Irvine has proposed; augmenting conventional measures with genetic engineering and other innovative approaches, to pare down vector population and leave others incapable of spreading disease. While controversial, the Sterile Insect Technique (SIT) has worked against disease vectors and agricultural pests.
Tsetse flies, the vectors of sleeping sickness, were eradicated from Zanzibar, an island of Tanzania.
California citrus groves were cleared of the invasive Mediterranean fruit flies.
Eradication of livestock parasites and flies.
SIT damages the male insects to such an extend that they can not reproduce but still compete with the wild males for mates. Entomologists are setting up research fields to study different ways to genetically modify, either the microbe or the vector insect that carry them.
Entomologist Celia Cordon-Rosales of the Universidad del Valle de Guatemala is targeting disease spreading insects, to genetically alter them or to manipulate organisms living in them. This approach remains controversial, and because the government will be tough on giving permission to release modified insects or micro-organisms in the environment, it is not too early to carry-out this project, because it involves a lot of basic research, and special precaution to ensure that potential problems with releasing the research sample, is properly secured. Cordon-Rosales' major research is with Chagas Disease. This is an insect-borne disease, that is contracted via infection with the single celled protozoa: Trypanosoma cruzi. Several insects are the vector of this disease. The bug is called “kissing” or” assassin “bug. Kissing because it has a tendency to bite people near the mouth. Chagas is prevalent in Latin America to as far North as the United States. 90 million people live in the areas where Chagas disease is endemic, 12-18 million (13-20%) people are infected of which 10-30% develop heart failure or other chronic life threatening symptoms. The mortality is approximately 50,000 people per year.
The basic research set-up is what she refers to as a ghost town, isolated from human life by fine mesh nets through which bugs can not escape. The imitation village would contain huts from straw and clay. It will be occupied by pigs in pens, and free living insects and bacteria. The mock hamlet will be encircled by a ditch, which will collect any runoff water that might permit micro-organisms to leave the site. Rosales hopes that with the results of her research project and that of her collaborators in the United States, that she will also be able to address the problem of the reemergence of Malaria, Sleeping sickness, Dengue fever and Yellow fever as well.
Posted By Ingrid Daly October 19, 2006
No comments:
Post a Comment