Experimental transmission of Caligus rogercresseyi between two different fish species.

Caligus rogercresseyi is the dominant sea louse parasite affecting the salmon and trout industry in southern Chile. This parasite has a wide range of native and endemic fish hosts. The Patagonian blenny Eleginops maclovinus, which is parasitized mostly by the caligid species Lepeophtheirus spp. and C. rogercresseyi, is presumably responsible for the transmission of C. rogercresseyi to salmonids. The aim of this study was to characterize the transmission of parasites between different fish species and parasite cohort development under laboratory conditions. Parasite abundances and intensities were quantified. Transmission of parasites from Patagonian blenny to Atlantic salmon Salmo salar was lower (~9%, mainly corresponding to C. rogercresseyi) than from salmon to Patagonian blenny (14.7-26.9%, where only C. rogercresseyi were observed). This suggests that the transmission of C. rogercresseyi from salmon individuals is higher than the transmission from a native fish. Parasite cohorts developed successfully on both fish species, but apparently under different developmental rates. Water temperature, oxygen, and juvenile abundances were the variables that better explained cohort development success and variation in C. rogercresseyi adult abundances over time.

[A recent trend in infant mortality statistics]. / Evolución reciente de la tasa de mortalidad infantil.

PIP: Between 1974-79, despite the severe economic recession during 1975-76 and along with the precarious standard of living of the low-income population, the infant mortality rate (IMR) continued to drop at the same pace registered since the mid-1960s. This is the starting point of research on factors which lead to the mitigation or abolition of the adverse effects of socioeconomic condition on health standards of the infant population. The drop in the IMR has recently been attributed to the fall in the birthrate expressed in terms of modifications in the composition of live births; the validity of this hypothesis is evaluated. It is seen that although a change in the composition of births in order of sibship and maternal education are variables which can explain the decreased IMR, their impact was no greater between 1974-79 than between 1969-73. Thus, these factors cannot be labelled as those which perpetuated the adverse effects of socioeconomic condition on the IMR. Empirical support was found for the hypothesis which postulates public health services as the causative factor. Public health services have emphasized the mother-child group as well as nutrition programs, especially those with lactating infants and the undernourished. These appear to be factors which explain that the IMR has not ceased to decline as was expected given the deterioration of the socioeconomic condition. Finally, particular aspects of the situation in Chile which have made these results possible are analyzed. (author's modified)^ieng