This 6th note relates some new observations on Oryzomys?
leishmaniasis and presents studies of the Phlebotomus from Utinga
forest. Finally, some comments on probable meaning of Oryzomys?
leishmaniasis are made.
From August 1963 to Apri1 1964, from 121 Oryzomys
examined, 24 (19.8%) were found positive. From May 1964 to February 1966, from 213 (Oryzomys examined, only ten (4.7%) were found
infected. So, the prevalence has falled more than four times.
The reasons of this fact are probably the following: First,
the removal from the focus of 13 infected Oryzomys (accidental death,
histopathological studies and the beginning of laboratory breeding).
Indeed, that represents the elimination of more than a half of the
reservoirs met till April 1964. In a second place, the removal of thousands
of Phlebotomus from the area by systematic captures. On the other hand,
it is possible that some light lesions of Oryzomys? tail escaped at
inspection.
However, it is possible too, that the above mentioned
reasons are not so significative as we intend to understand them, since
from December 1965 to February 1966 we have found three infected
Oryzomys.
As we have mentioned, captures of Phlebotomus were
made periodically. From 1068 Phlebotomus, captured in 1963 and 1964,
belonging to 15 species, 68.6% were P. antunezi e P. damascenoi. In
1965, from May to December systematic mouthy captures were made,
with a mean of 18 captures by month. From a total of 4736 specimens,
belonging to 24 species, 38.1% were P. rorotaensis, 21.7% were P.
antunezi and 16.2% were P. damascenoi.
The Oryzomys? infection conditions in Utinga forest shows
very clearly its zoonotic character. Probably, other rodents integrate
this wild cycle in other areas of Amazonia and in other forest regions
of the country. Naturally, according to infected region different species
of Cricetidae reservoirs and Phlebotomus transmitters are integrated
in that wild cycle. Man ? so sensitive to leishmaniasis ? became
infected when penetrates in zoonotic area interfering in that wild cycle.
After the forest overthrown to settlement and,
consequently, the wild animals escape, the rural leishmaniotic foci were
established and later suburban and urban foci too. In these foci, with
domiciliary and peri-domiciliary Phlebotomus transmitters, the dog and, probably, also man appear as secondary reservoirs. So, in the leishmaniasis
epidemiology we have two cycles: The wild or zoonotic and the rural or
anthroponotic.
The latter can be controlled by domiciliary and peridomiciliary
expurgation with residual-acting insecticides. But obviously,
it is impossible to control the zoonotic foci. It is a permanent menace to
those who are obliged to visit the forests. Individual protection measures
must be employed. The development of better techniques for disposal
of efficient vaccines must be promoted.
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