Untold Mysterious Story of World's Most Serious Infectious Diseases

credit: third party image reference

No other single infectious disease has had the impact on humans that malaria has had. The first references to its periodic fever and chills can be found in early Chaldean, Chinese, and Hindu writings. In the late fifth century BCE, Hippocrates described certain aspects of malaria. In the fourth century BCE, the Greeks noted an association between individuals exposed to swamp environments and the subsequent development of periodic fever and enlargement of the spleen (splenomegaly). In the seventeenth century, the Italians named the disease mal' aria (bad air) because of its association with ill-smelling vapors from swamps near Rome. At about the same time, the bark of the quinaquina (also known as cinchona in below picture ) tree of South America was used to treat the intermittent fevers, although it was not until the midnineteenth century that quinine was identified as the active alkaloid.

credit: third party image reference

The major epidemiological breakthrough came in 1880, when French army surgeon Charles Louis Alphonse Laveran observed gametocytes in fresh blood. Five years later, the Italian histologist Camillo Golgi observed the multiplication of the asexual blood forms. In the late 1890s, Patrick Manson postulated that malaria was transmitted by mosquitoes (Anopheles).

credit: third party image reference

Sir Ronald Ross (In below Picture), a British army surgeon in the Indian Medical Service, subsequently observed developing plasmodia in the intestine of mosquitoes, supporting Manson's theory. Using birds as experimental models, Ross definitively established the major features of the life cycle of plasmodia and received the Nobel Prize in 1902. credit: third party image reference

Human malaria is known to have contributed to the fall of the ancient Greek and Roman empires. Troops in both the U.S. Civil War and the Spanish-American War also were severely incapacitated by the disease. More than 25% of all hospital admissions during these wars were malaria patients. During World War II, malaria epidemics severely threatened erythrocytes lyse and the gametes fuse to form a diploid zygote called the ookinete. The ookinete migrates to the mosquito's gut wall, penetrates, and forms an oocyst. In a process called sporogony, the oocyst undergoes meiosis and forms sporozoites, which migrate to the salivary glands of the mosquito. The cycle is now complete, and when the mosquito bites another human host, the cycle begins anew. The pathological changes caused by malaria involve not only the erythrocytes but also the spleen and other organs. Classic symptoms first develop with the synchronized release of merozoites and erythrocyte debris into the bloodstream, resulting in the malarial paroxysms-shaking chills, then burning fever followed by sweating.credit: third party image reference

It may be that the fever and chills are caused both the Japanese and Allied forces in the Pacific. The same can be said for the military conflicts in Korea and Vietnam. In the twentieth century, efforts were directed toward understanding the biochemistry and physiology of malaria, controlling the mosquito vector, and developing antimalarial drugs. In the 1960s it was demonstrated that resistance to P. falciparum among West Africans was associated with the presence of hemoglobin-S (Hb-S) in their erythrocytes. Hb-S differs from normal hemoglobin-A by a single amino acid, valine, in each half of the Hb molecule. Consequently these erythrocytes-responsible for sickle cell disease-have a low binding capacity for oxygen. Because the malarial parasite has a very active aerobic metabolism, it cannot grow and reproduce within these erythrocytes.credit: third party image reference

In 1955 the World Health Organization began a worldwide malarial eradication program that finally collapsed by 1976. Among the major reasons for failure were the development of resistance to theinsecticide DDT by mosquitoes and the development of resistance to chloroquine by strains of Plasmodium. credit: third party image reference

Scientists are exploring new approaches, such as the development of vaccines and more potent drugs. In 2002 the complete DNA sequences of P. falciparum and Anopheles gambiae (the mosquito that most efficiently transmits this parasite to humans in Africa) were determined. Together with the human genome sequence, researchers now have in hand the genetic blueprints for the parasite, its vector, and its victim. This has made possible a holistic approach to understanding how the parasite interacts with the human host, leading to new antimalarial strategies, including vaccine design.credit: third party image reference

Overall, no greater achievement for microbiology could be imagined than the control of malaria-a disease that has caused untold misery throughout the world since antiquity and remains one of the world's most serious infectious diseases.