Malaria Closes Brazilian Ports

On March 30, 1905, the Santos Dock Company of Santos, near Sao Paulo, Brazil, hired Carlos Chagas to combat malaria. Its workers were so weakened by fever that they could not complete the port of Santos, the most important in Brazil. Carlos Chagas accepted the challenge to do fieldwork (“trabalhar no campo ”) and to observe firsthand malaria within its natural and social environment. Chagas used his first paycheck to buy a microscope; he then had the only tool needed to examine the microcosm.

Carlos Chagas’ earlier studies of malaria and later studies of Chagas’ disease stimulated new concepts of these diseases that incorporated parasitology, entomology, and human physiology while studying relationships of parasites, vectors, and hosts. Vectors are carriers, usually arthropods or insects, that transmit causative organisms of disease, parasites, from infected to noninfected individuals. A parasite usually goes through one or more stages in its life cycle within the vector. The host is the organism in which parasites obtain nourishment and reproduce. Knowledge of the parasitic cycles enhances our understanding of tropical diseases and their relationship to the environment.

Carlos Chagas disagreed with the then‑current practices of pouring toxic substances on lakes, reservoirs, and stagnant water to eliminate malaria. Doctors had used this method in Panama and Cuba under the assumptions of marasmus theory that attributed malaria to vapors. Chagas recognized that the use of smoke, toxic substances, and the drainage of swamps were ineffective remedies because they destroyed only the larvae of the mosquito. He also objected that such methods destroyed fish and reptiles and could never be applied to all the ponds, lakes, and waterholes in the tropics.

Because mosquito larvae are not infected with parasites, Carlos Chagas’ strategy against malaria in 1905 was to attack the adult vectors by preventing uninfected (also sometimes called sterile) mosquitos from coming into contact with infected humans and infected mosquitos from coming into contact with healthy humans (Chagas 1935). Chagas observed that after mosquito vectors acquire their fill of blood, they lose the ability to take off in flight and can hardly fly over the walls and furniture of a house to begin digestion of the ingested blood (Chagas Filho 1993:78). He advocated closing off houses with doors and screens and disinfecting houses by burning pyrethrum from chrysanthemum flowers, which kills mosquitos in flight.

Realizing the futility of trying to destroy mosquitos, Chagas devised ways to prevent mosquitos from coming into contact with malaria patients. He found that mosquitos ingest most parasites during the erythrocytic cycle, when merozoites abundantly attack the red blood cells. The erythrocytic cycle corresponds to parasitemia, characterized by high fever, which naturally attracts mosquitos. He advocated that these patients be quarantined in closed‑off areas with walls, screens, ceilings, and caulked joints, as distant as possible from mosquitos. Moreover, Chagas treated patients with quinine to reduce fever and destroy parasites. Quinine is an Andean medicinal remedy for malarial fever from the bark of the Chinchona calasaya tree. Kallawaya herbalists have used it for centuries and brought it to workers of the Panama Canal (see Bastien 1987a).

Chagas devised a threefold program in Santos which became a protocol for malaria campaigns in other regions of Brazil by 1917. The approach consisted of 1) administration of quinine in dosages of 50 centigrams every three days, 2) isolation of patients from mosquitos in infirmaries with fine metal screens and continual treatment with quinine of other malarial patients in the region, and 3) periodic and systematic disinfecting of domiciles with pyrethrum. Chagas further contributed to malariology by describing the edematous form of Quartan fever (attacks occurring every fourth day), the bone‑marrow lesions of malaria, and the description of the disease as a domiciliary infection, rarely contracted outdoors (Lewinsohn 1981:452).

Carlos Chagas succeeded against malaria primarily because he did fieldwork, observed the disease in its environment, and addressed the problem in a scientific and therapeutic way. He also worked with patients, parasites, and insects in epidemic settings to get an enlarged perspective of the disease. On returning to Rio from Santos, Chagas went to work on malaria control for the Xerem River dam and had similar success. In 1906 he became an associate of the Oswaldo Cruz Institute in Rio de Janeiro.