Acta Leidensia最新文献

Mice infected with the rodent malaria parasite Plasmodium berghei exhibit ultrastructural changes of the blood-brain barrier during the course of infection. Firm adherence including cellular interdigitation of infected cells or leucocytes and even clusters of cells to the vascular-endothelial lining is repeatedly observed early during infection. Ghosts and membrane remnants can be found engulfed in the surface of the endothelial cells. Frequently leucocytes migrate between endothelial cells and even cause a lift off and degeneration of these cells. In addition, endothelial cells exhibit increased pinocytotic activity, many irregular cytoplasmic extensions and even phagocytic activity. These changes are associated with degenerative changes in the basement membrane. Swelling and deposition of collagen-like fibres and even loss of fragments of basement membrane is observed. In some places fingerlike extensions of pericytes passed through the basement membrane and contacted or even bulged into the cytoplasm of endothelial cells. Ballooning and even coalescence of perivascular astrocytes was observed and contributed to the appearance of a perivascular oedematous space. The observed changes indicate a progressive deterioration of the blood-brain barrier eventually leading to endothelial lesions and hemorrhage.

The present study was carried out between December 1986 and January 1988. A series of 3,048 individuals (46% males and 54% females) were examined in 56 villages; onchocercal dermatitis and lymphadenitis were seen. The crude prevalence of nodules and of microfilariae amounted to 14% and 43%, respectively. The prevalence of nodules was significantly higher at the femoral trochanter than at other anatomical sites. The overall prevalence of nodules, and of microfilariae, was significantly higher in males than in females. The age-adjusted prevalence and the geometric mean microfilarial load were significantly higher in the cohort of males older than 15 years than in their female counterparts. The overall geometric mean microfilarial load was 18 microfilariae per skin snip. The correlation between prevalence and intensity of infection was poor, but was perfect between mean microfilarial density per skin snip and mean microfilarial density per milligram skin. The ratio of mean microfilarial density per skin snip to mean microfilarial density per milligram skin was 1:6. The correlation between prevalence of onchocercomata and microfilarial prevalence or microfilarial density was weak. Both of the latter criteria identified the Rokel/Seli as the river with the highest proportion of hyperendemic villages. The implications of the present findings for the epidemiology of onchocerciasis are discussed.

Yaws (framboesia tropica), caused by Treponema pallidum subspecies pertenue, is a chronic infectious disease, found in tropical rural regions. As a result of mass treatment campaigns conducted in the 1950s and 1960s the prevalence of yaws and the other endemic treponematoses (pinta and endemic syphilis) has decreased greatly. However, in several tropical regions in the world resurgence of yaws was reported in the 1980s. In this article we present the results of a small survey on yaws in six health centres in the Pariaman region in West Sumatra, Indonesia. A general conclusion from this small survey is that yaws is far from being eradicated and that in this region the disease is on the increase again. Some major findings of T. pertenue research are presented here.

Leptospirosis is caused by different leptospiral variants. Analysis by cross agglutination absorption tests (CAAT) led to the definition of entities called serovars to distinguish between leptospires on sub-species level, and to the designation of reference strains representing serovars. For decades CAAT has been used to classify leptospires and now approximately 200 serovars have been recognized. In the last few years, it has become increasingly more clear that the serovar concept is no longer fully satisfactory as it may fail to adequately define epidemiologically important entities. In addition, CAAT is too cumbersome and time-consuming for routine typing. Various methods have been developed based on antigenic or genetic analysis with the purpose to supplement or to replace the CAAT. Most of these methods are still in an experimental state. It is to be expected that a typing method based on genomic analysis will eventually become most important. Such a new method should have considerable advantages in order to be acceptable for the development of a new classification system replacing the system based on serovars, which is widely accepted and in many respects still satisfactory. From the new methods, analysis of leptospiral DNA fragment length after digestion with restriction enzymes (REA) has been widely used and proven to be useful for typing. Pending the development of new typing methods that have clear advantages and may lead to a new classification system, it is suggested that the classification system based on serovars is maintained and that REA is added to each description of a new serovar.

A two-year longitudinal study carried out in five villages in a forest region of Gorama Chiefdom, Kono District, Sierra Leone, revealed that infection with Onchocerca volvulus was hyperendemic, the overall rate of infection being 61.6%. Prevalence rose from 28.6% in the 1-5-year age group, peaking among the 21-30-year age group (82.5%) and then levelling off. The intensity of infection though low, peaked in the 31-40-year-old males and in the 41-50-year-old female cohorts. The iliac crest was more sensitive for microfilarial (mf) recovery than the shoulder and the outer canthus. The majority of the nodules were located in the pelvic region. Microfilariae invasion of the eye was low, with low anterior chamber lesions but high posterior chamber lesions comprising mainly optic atrophy and choroidoretinitis. The rate of blindness was 1.6%, ocular onchocerciasis being the leading cause of blindness followed by cornea opacities.

The rapid divergence of tandemly repeated families among Plasmodium species is in striking contrast with the extraordinary fidelity of the repeat copies present in a given genome. Close examination of the arrays of tandem repeats reveals an unsuspected regularity in the distribution of base substitutions, and clear relations between sets of repeats of different length, often coexisting in the same repeated region. The regular distribution of defects in the linear lattice gives rise to a hierarchy of periodicities. A model is proposed which accounts simultaneously for the rapid and concerted evolution of the repeats, and for the generation of supra-periodicities. The implications of this model with respect to repeated-pattern evolution are discussed.