Some aspects pertaining to the ecology of the dimorphic fungus, Paracoccidioides brasiliensis, are reviewed. The available facts concerning the interactions among the only known host (man), the environment (limited to certain Latin-American countries) and the parasite (with an unknown habitat), are analysed. Efforts are made to detect clue circumstances which may lead to discovery of the fungus micro-niche. An analysis of P. brasiliensis mycelial form reveals that such a form has the required capabilities to be the natural infectious form. Its requirements for a moist environment in vitro as well as the high relative humidity predominating in the heart of the endemic areas point towards the possibility of an aquatic---or at least, an extremely humid--habitat for P. brasiliensis.The last decade has seen important developments in our knowledge concerning various aspects of paracoccidioidomycosis, its etiologic agent, Paracoccidioides brasiliensis, and host-parasite interactions in the infection [18]. Nonetheless, the relationship between the fungus and its environment has escaped scientific analysis in spite of its sporadic isolation from soils [2, 43] and its presumed occurrence in a squirrel monkey [26]. So scanty are the new findings since the subject was masterfully reviewed by Borelli in 1972 [10], that it might appear premature to discuss the ecology of the fungus once more. However, a critical review of the current status of available information was considered worth undertaking. Such a review would serve to bring together widely scattered data, critically analyse the present findings and point to unexplored, promising areas for research.The consensus prevails that the habitat of P. brasiliensis is neither man nor the animals that surround him, but rather the soil of the endemic areas [33,34]. In contrast to what is known about other fungal pathogens such as Histoplasma capsulaturn and Coccidioides immitis [1], data concerning the microenvironment of P. brasiliensis are limited. This is rather peculiar since circumstances such as the restricted geographic distribution of the disease, and the apparent connection with only one host, man, should furnish clues to the problem. This is even more so when one

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Work in flower production, irregular relationship, illness and tobacco exposure would be associated with impaired fecundability.

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The possible relationship between erythrocyte antigens and the presence of malaria infection by P. vivax and P. falciparurn was sought in four different ethnic groups of two departments of Colombia. Malaria infection by P. falciparum was found in 91.4% of malaria infected blacks. No significant differences were found between the presence of malaria infection and ABO antigens. In the other blood groups, it was observed that groups MNSs conferred black people a greater Rr for malaria by both species of Plasmodium and that Duffy-negative blacks and indians appeared to be resistant to P. vivax infection. A predominance of P. vivax infection was observed in Katio indians while P.falciparum was predominant in Kuna indians; the reason for this finding still needs to be explored.

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