Public health hazards among workers along the Trans-Amazon highway

Abstract

Since 1971 the IEC and SUCAM have been monitoring malaria, leishmaniasis, schistosomiasis and leptospirosis amongst the workers settled along the Trans-Amazon highway. The possible appearance of new diseases was also taken into consideration. In addition to this, short term ecological studies have been performed in ten different sites along the highways, aiming to identify zoonotic foci of some of the diseases. An investigation of the breeding sites of snails known to serve as intermediaryhosts of schistosomiasis was also carried out. To date, malaria seems to be the most important infectious disease of public health importance along the Trans-Amazon highway. Infections caused by arboviruses and less frequently by leishmania have been diagnosed in the area. No cases of yellow fever, however, were observed among the colonists. The hemorrhagic syndrome of Altamira to date constitutes the only new illness diagnosed in the area. This syndrome is limited to the Altamira area, as to date no cases have been found in other locations where colonists are also exposed to the bites of blackflies. A significant (16.5%) number of a group of 309 inhabitants possessed antibodies to different types of Leptospira, however, no specific diagnosis of clinical cases has yet been made. Also no cases of histoplasmosis or autochthonous cases of schistosomiasis have so far been diagnosed. Zoonotic foci of known human pathogens were identified, such as: arboviruses, leishmanias, leptospiras, Histoptasma. Three foci of Biomphataria straminea have also been found, two in the Altamira area and one near to Santarém. The assessment of the importance of these findings is rather difficult at the moment. Certainly infection of man with some of these agents is already occurring, although its exact rate has not yet been determined. The potentiality of these foci is certainly a matter of concern, despite the fact that the nature of their hazard to the colonists is unpredictable. It will probably depend upon the ecological changes brought about by man. Some of the preventative measures already adopted by the public health authorities are certainly benefiting the population. Thus, yellow fever vaccination given to the colonists before entering into the areas protects them against sylvan yellow fever. Also the diagnosis and treatment of cases of schistosomiasis is a most important step to stop the disease from becoming established in the area. Malaria is still a great threat to the colonists, in spite of the preventative measures used. Apart from the intensification of these measures it is clear that others need to be taken into consideration. Firstly, one should consider that all colonists and their families, as well as workers, should have their blood examined for the presence of malaria parasites, and treatment given to the positive cases. Secondly, elimination by drainage or by chemical treatment of the breeding foci of Anopheles should have special emphasis. In this respect road constructors should be prevented from leaving unfilled excavations along the highways, which will accumulate water and thus serve as breeding sites for the vectors. Advice should also be given to the colonists to avoid storing water in uncovered containers. Thirdly, special emphasis should be given to the epidemiology of the infection as it is possible that extradomiciliar transmission is accounting for a considerable number of cases. If this is so then new approaches have to be adopted: in addition to the screening of infected colonists, the possibility of drug; prophylaxis should also be considered. In view of the-danger of introduction of species of domestic reduvidae bugs from endemic Chagas' areas, insecticide treatment of materials originating from such areas is advisable. Although the present data do not reflect the true incidence of the infectious diseases among the colonists, they do however give useful information regarding some of the present and potential health hazards. A well organized and long term surveillance program for the diseases described here and for others of public health importance should be implemented in this area and also in other areas of colonization.