n the search to discover the agents that cause mad cow disease, scrapie in sheep, and CJD and kuru in humans, diseased brain tis
sues were passed through a fine filter to remove bacteria. The filtrate was still infectious, indicating that something smaller than bacteria, either viruses or organic molecules, must be the causative agent. If a virus was responsible for these brain diseases, then the infectious agent would contain either RNA or DNA. Other possibilities were that the agent was a carbohydrate, fat, or protein. Tissue filtrates were treated with agents that destroyed just one of these chemicals and then injected into a healthy animal, with the results as follows. What is the infectious agent? •Amylase digests carbohydrates; tissue filtrate still infects healthy test animal. •Lipase digests fats; tissue filtrate still infects healthy test animal. •Formaldehyde and/or heat denatures DNA and RNA; tissue filtrate still infects healthy test animal. •Trypsin digests protein; tissue filtrate does not infect healthy test animal.
Pathogens may be defined as the disease causing organism and capable of inducing immune response in the organisms. The organisms that can acts as pathogen are virus, bacteria and nematodes.
Different experiments have been performed to find the infectious agent. The digestion of trypsin protect the animals from the disease. This means the infectious agent must be protein as the protein digestion disrupts the pathogenicity of the organism.
C The decrease in native birds will be due to the increased competition for food. They may adapt to different foods; however, the initial and most prominent effect will be that of the native birds' population declines.
