Martin HenryMALARIA WAS declared eradicated from Jamaica in 1963, 41 years ago. The eradication of the disease is one of the triumphs of our public health drive against infectious diseases from colonial times and carried over into Independence. But much of the rest of the world is not so lucky. The World Health Organisation (WHO) reckons that some 300 million people are infected, with about 1.5 million deaths each year. The disease cuts a vast swathe through Africa, Asia and Latin America. There are nearly 100 countries on the WHO malaria list. Eighty per cent of cases occur in tropical Africa.
Haiti and 20 other countries of the Western Hemisphere have endemic malaria. One of the expressed fears overshadowing the acceptance of Haitian refugees here is the fear of the re-introduction of a disease that has been eradicated and kept at bay from our shores for four decades. Some of the refugees apparently have malaria. But transmission here is not likely, the Health Ministry says.
STAGNANT WATERS
The faith of the guardians of our health is based reasonably on how malaria is transmitted. The very name of the disease 'malaria' (known as marsh fever for centuries) means bad air in Italian. And for thousands of years malaria was linked to swamps, the bad air from swamps being thought to be the cause of the disease. The association with stagnant waters led the Romans to carry out drainage programmes, the first known public health intervention against malaria. The discovery of the agent of malaria and how the disease is transmitted is a fascinating detective story of science, and Alma Mockyen and I once did a programme on it in our radio series 'Science Serving U.S.', which is still carried by Radio Mona Fridays at 2:00 p.m.
It had been observed under the microscope that the blood of malaria sufferers had black pigments deposited. A French doctor, Alphonse Laveran, working with the French legionnaires in Algeria, wanted to find out what these pigments were and how they figured in the disease. He discovered more than he bargained for. Dr. Laveran, using rather primitive microscopy, fresh unstained blood, under basic field hospital conditions found, in 1880, the parasite which was causing the disease. It wasn't a bacterium; it was a protozoan somewhat like its cousin Amoeba. Laveran showed that the parasites, during their development in the red blood cells, destroy the cells; and the red haemoglobin pigment in the blood cells is changed into the melanin particles observed.
PROTOZOAN PARASITE
The protozoan parasite was called Plasmodium; but how did it get from one person to another? The solution to that problem came from another army surgeon, the Indian-born British Ronald Ross. Dr. Laveran had unsuccessfully examined the water, soil and air of marshlands to locate the parasite outside the human body. He ended up suspecting mosquitoes. Another famous researcher, Patrick Manson, a Briton, studying elephantiasis in China found that that disease was caused by a small parasitic worm transmitted by mosquitoes. Manson thought it quite possible that malaria had a similar mosquito transmission and he suggested this to Ross when they both met in London in 1894.
Ross went back to India to check it out, with no training in microbiology or microscopy beyond medical basics, little knowledge of the malaria literature, and no biological knowledge of mosquitoes. He examined, under the microscope, the innards of hundreds of mosquitoes which had bitten malaria patients but found nothing. Exhausted, frustrated, with his one microscope rusted and the eyepiece cracked, and about to give up, he examined the stomach of yet another mosquito. There were no malaria parasites, but Dr. Ross noticed 12 little dark circles which when examined under high power contained black grains like the black grains known in the malaria parasite from humans. Ross fell into an exhausted sleep for an hour and woke up to give the world the life-cycle of the malaria parasite which took different forms in humans and mosquitoes.
The clincher came when Sir Patrick Manson had infected mosquitoes sent to him from Italy and his son and a friend volunteered to be bitten to see if they would contract malaria. They did!
PLANT JUICES
So the Romans were right, after all. Drain the swamps. Get rid of the breeding ground of the mosquito. In the case of malaria transmission, specifically the anopheles type, and more specifically the female. Males drink only plant juices. Females need a blood meal to develop eggs.
The middle 20th century provided a potent tool for dealing with the malaria vector mosquito insecticides. DDT in particular was heavily used to kill the beasts. Our own eradication programme, long before DDT was banned, relied heavily on spraying with that insecticide. The search for a malaria vaccine is on, and the Bill and Melinda Gates Foundation last September pumped another US$100 million into the Malaria Vaccine Initiative which the Foundation had established in 1999.
Our MOH is reasonably assured of non-transmission of malaria from any Haitian cases arriving here because of the control of the vector anopheles mosquito. But, of course, we can never relax the control programme.
Martin Henry is a communication specialist.
