Public health hazards among workers along the trans-amazon highway

The colonization of the forested areas intersected by the Trans-Amazon highway was started in mid-1971. The immigrants originated from different areas of the country, but most of them came from the northeast. The colonization has been more intense in the areas of Altamira, Marabá and Itaituba, all in Pará State. Up to the end of 1974 about 28,000 colonists and their families are living in these areas. It was logical to assume that these people would come into contact with certain zoonotic agents such as arboviruses and leishmanias, and that agents and vectors of infectious diseases previously unknown in the Trans-Amazon area, such as schistosomiasis and Chagas’ disease, might be introduced. Investigations commenced in 1972, therefore, with the aim of identifying certain health problems, in different areas of the highway. In November 1972 a permanent surveillance program was initiated in the area of Altamira. Serological studies demonstrated that arbovirus infections have occurred among colonists. Thus, 2.6% of the persons studied, mainly in hospitals and health posts, were infected in the first semester of 1973; 6.5% in the second semester of 1973; and 18.0% in the first semester of 1974. Mayaro, Guaroa, Itaporanga and Oropouche were the commonest arboviruses responsible for the infections. Group B arboviruses were ex cluded from the analysis. A thrombocytopenic purpura, named Hemorrhagic Syn drome of Altamira (HSA), was noticed in the Altamira area from the beginning of 1972. The great majority of cases is restricted to the colonists and about 160 cases have been ob served up to October, 1974. On the basis of clinical and laboratory data, the disease was responsible for three deaths. Epidemiological and serological evidence suggests that the syndrome is associated with the black-fly, Simulium and its bite. Studies on leishmaniasis revealed a high incidence of in fections among wild animals trapped at various sites along the Trans-Amazon highway. Thus, of 166 specimens of the rodent Proechimys studied, 26 were infected with Leishmania mexicana amazonensis (15.7%), and parasites of the Leishmania braziliensis complex have been isolated from Proechimys, and the opossum Didelphys. Skin tests on colonists along the highway have shown a high incidence of positive reactions to leishmanin (up to 60%), but up to now active cases of cutaneous leishmaniasis have been uncommon. It is anticipated that the incidence of the disease will rise sharply in the succeeding, nonimmune generation: cutaneous leishmaniasis may then form a serious problem. We have already established the inevitable presence of dense populations of highly anthropophilic sandfly species at all points studied along the new roads. Some of these species will undoubtedly act as vectors. Between 1971 and 1974, 310 imported cases of schistosomiasis were diagnosed in the Altamira and Marabá areas and all were treated with etrenol. Although three foci of planorbid snails have been discovered, there is no evidence yet of local transmission of the disease. Malaria is a most important problem along the Trans- Amazon highway and thousands of cases have been diagnosed. Most infections are caused by P. falciparum but infections with P. vivax are also common. Leptospira antibodies have been detected among persons already living along the road and also in wild animals. Finally, cases of South American Blastomycose have been detected in the area between Marabá and Altamira; and Histoplasma has been isolated from a number of wild animals.