DISEASES

DISEASES

I . Introduction

Pathology is the scientific study of disease (pathos means suffering logos means science . Pathology is first concerned with the cause , or etiology , of disease . Second , it deals with pathogenesis , the manner in which a disease develops . Third , pathology is concerned with the structural and functional changes brought by disease and with its final effects on the body

Although the terms infection and disease are sometimes used interchangeably , they differ somewhat in meaning . Infection is the invasion or colonization of the body by pathogenic microorganisms . A disease

occurs when an infection results in any change from a state of health . Disease is an abnormal state in which part or all of the body is not properly adjusted or is not capable of carrying on its normal functions . An infection may exist in the absence of detectable disease For example , the body may be infected with the virus that causes Epidemic Typhus , but there may be no symptoms of the disease

The presence of a particular type of microorganism in a part of the body where it is not normally found is also called an infection - and may lead to disease . For example , although large numbers of E . coli are normally present in the healthy intestine , their infection of the urinary tract usually results in disease . Few microorganisms are pathogenic . In fact , the presence of some microorganisms can even benefit the host

This intent to scrutinize the four dreadful diseases such as Chagas Disease , Malaria , Bubonic , and Epidemic Typhus

II . Discussions

A . Chagas Disease

American Trypanosomiasis (Chagas ' disease ) is a protozoan disease of the cardiovascular system . The causative agent is Trypanosoma cruzi (tri-pa-no-so ' ma kruz e , a flagellated protozoan . The disease occurs in the extreme southern United States , Mexico , Central America , and into South America . Only a few cases have been reported in the United States but the disease infects 40 to 50 of the population in some rural areas of South America (see Chagas Disease . Grolier Encyclopedia of Knowledge , pp . 365-371

The reservoir for T . cruzi includes a wide variety of wild animals including rodents , opossums , and armadillos . The arthropod vector is the reduviid bug , called the kissing bug ' because it often bites persons near the lips . The insects live in the cracks and crevices of mud or stone huts with thatched roofs . The trypanosomes , which grow in the gut of the bug , are passed on if the bug defecates while feeding . The bitten human or animal often rubs the feces into the bite wound or other skin abrasions by scratching or into the eye by rubbing . A bizarre means of transmission occasionally occurs in remote areas in Mexico , where reduviid bugs are eaten as an aphrodisiac (see Chagas Disease Grolier Encyclopedia of Knowledge , pp . 365-371

At the site of inoculation , the trypanosomes reproduce and pass through various stages of their life cycle . A swollen lesion develops at the inoculation site (often near the eye . The parasites are carried by the blood to many organs of the...