Yellow fever. Development of vaccine Research Paper

Yellow fever. Development of vaccine - Research Paper Example Yellow fever has been a cause of life threatening epidemics throughout the last few hundreds of years of human civilization. It is believed to have originated in Africa and transported to the western hemisphere through the slave trade with the first reported outbreak being in Yucatan in 1648.The ensuing years reported a number of outbreaks in the Americas and Europe. 2 The disease remained an enigma though Cuban Carlos Finlay suggested the mosquito Culex cubensis which is now called Aedes aegypti to be responsible for the spread of the disease. 3 His multiple attempts however could not prove the theory and it was not until the end of the 19th century that the mystery surrounding the enigmatic disease was unlocked by Surgeon Walter Reed of the United States Army. The work done by Reed and his colleagues found that the mosquito Aedes aegypti was critical in the dissemination of the disease and a filterable agent found in the patients' blood was the cause of the disease. A rapid eradica tion campaign against the mosquito vector followed the discovery and in 1918 a Yellow Fever Commission funded by the Rockfeller foundation was established for the purpose. The eradication drive though effective in curbing the disease in most part could not eradicate the disease completely the possible explanation for which did not come until the 1930s when new techniques were used to study the yellow fever virus. It then became known that the disease was a zoonosis with the natural reservoir of the virus being non-human primates and jungle dwelling sylvatic mosquito species. The disease transmission follows a pattern where a range of vectors transmit the virus from infected monkeys to humans resulting in sporadic cases of the disease. These cases when comes in contact with larger human populations in urban dwellings where it is transmitted by A. aegypti from man to man results in the possibility of an epidemic. 2 Yellow fever is an infectious disease which causes damage of many organs due to severe bleeding. One of the clinical symptoms that give the disease its name is jaundice. The acute phase symptoms that develop following the incubation of the virus in the body for three to six days include fever, nausea, muscle pain with headache, backache, loss of appetite and shivers. Following initial remission some patients enter a severe toxic phase with the return of high fever. Various organs including the kidney and liver are affected. Bleeding occur from nose, mouth, eyes and stomach which also appears in vomit and faeces. 5 There is no treatment specified for yellow fever except for supportive care for fever and dehydration and antibiotics for associated bacterial infections. Vaccines Development of vaccine An important breakthrough that identified Reed's filterable agent to be a virus came from the work done by Adrain Stokes and his collaborators in 1927 which showed monkeys could be infected with materials from yellow fever patients. The isolated virus was called the Asibi strain after the patient who provided the blood sample. 6 Yellow fever virus was identified to be a relatively small virus which readily lost infectivity but stabilized with proteins. 7 Yellow fever in the present classification is grouped under flavivirus (flavus in Latin meaning yellow) group along with more than 80 viruses seen in arthropod vectors. 8 Max Theiler in 1930 discovered a more convenient way of propagating the virus in mouse brain and developed a test for measuring protective antibodies in them. This led to the development of an important tool for epidemiological and diagnostic studies. 9 Theiler and his collaborators discovered the 17D variant when passaging the Asibi strain of the virus in cell cultures. 10 This would eventually become the basis for the first ever yellow fever vaccine responsible for saving innumerable lives and Nobel Prize for Theiler in 1951. Another live attenuated vaccine called the French Neurotropic Vaccine was developed from a different strain of virus isolated in 1927 in