Histopathologic and morphometric (area, perimeter, major and minor diameters)
analysis of hepatic granulomas isolated from twelve naturally infected
Nectomys squamipes
were compared to four experimentally infected ones and six
C3H/He mice. Liver paraffin sections were stained for cells and extracellular
matrix. Both groups of
N. squamipes presented peculiar granulomas consisting
predominantly of large macrophages, full of schistosome pigment, characterizing
an exudative-macrophage granuloma type, smaller than the equivalent granuloma
type in mouse. Naturally infected animals exhibited granulomas in different stages
of development, including large number of involutional types. Morphometric analysis
showed that all measurements were smaller in naturally infected animals than in
other groups. The results demonstrated that both
N. squamipes groups reproduced,
with small variations, the hepatic granuloma aspects already described in cricetidium
(
Calomys callosus
), showing a genetic tendency to set up
strong macrophage responses and small granulomas. Unexpectedly, natural infection
did not engender distinguished histopathological characteristics distinct from
those derived from experimental single infection, showing changes predominantly
secondary to the duration of infection. It appears that the variability of the
inocula (and the number of infections?) interfere more with the quantity than
with the quality of the pathological changes, denoting some morpho-functional
determinism in the response to schistosomal infection dependent on the animal
species.