Age-dependent reduction of schistosome fecundity in Schistosoma haematobium but not Schistosoma mansoni infections in humans.

Understanding the dynamics of schistosome infections is problematic because direct measurements of worm burden are not possible. Hitherto, the relative intensity of infection has been estimated by the number of parasite eggs excreted. Egg excretion is assumed to have a consistent relationship with worm burden with duration of infection. We have tested this assumption in Schistosoma mansoni- and S. haematobium-infected populations by looking at the relationships between a circulating parasite antigen, egg excretion level, host age, and parasite density. The study was carried out in two populations because experimental models suggested that S. haematobium but not S. mansoni suffers immune-mediated reduction of fecundity. The results were consistent with this observation, showing that S. mansoni egg output remains stable irrespective of host age or infection intensity while S. haematobium has a substantially reduced egg production with host age. This information is fundamental to understanding the immunology and epidemiology of human schistosomiasis and thus practical approaches to disease control.

Evolutionary, regulatory and mediation aspects of T.b. rhodesiense and its endemicity in Lambwe Valley, Kenya.

The transmission of the human African trypanosomiasis (HAT) infection, also known as human sleeping sickness, depends on environmental factors operating at the mega-, macro-, and micro-scale levels. However, at the latter level T.b. rhodesiense parasite undergoes metacyclic development processes, controlled by its evolution, regulatory and mediation factors. Selective pressures acting on host-parasite interactions are thought to influence the genetics of the parasite and its hosts. In retrospect, the phenotypic difference responsible for the change in fitness of the parasite is complicated, since natural variation in a phenotype may be maintained by frequency-dependent selection, with species-specific fitness dynamics. Although little evidence exists on aspects of mutualism o f trypanosomes, it is possible that synergistic interactions among pathogens may be involved in the complex of phenotype variations. This paper considers the underlying dynamics with reference to the endemicity of the infection in Lambwe Valley ecosystem.

Indirect assessment of eosinophiluria in urinary schistosomiasis using eosinophil cationic protein (ECP) and eosinophil protein X (EPX).

The pre- and post-treatment level of eosinophiluria, as measured indirectly by the amount of free or cell bound eosinophil cationic protein (ECP) and eosinophil protein X (EPX) in urine from Schistosoma haematobium-infected Kenyan school children, were measured and compared with intensity of infection (eggs/10 ml of urine), albuminuria and pathological changes as detected by ultrasonography. ECP and EPX were determined by means of specific ELISA methods and levels were determined in both urine supernatants and extracted urine deposits (cells and cell debris). The level of ECP was significantly raised in urine supernatants from infected children compared to controls, whereas high amounts of EPX were found in urine supernatants from infected children as well as from controls. However, the amounts of cell bound ECP and EPX were significantly raised in infected children. In pre-treatment observations significant correlations were demonstrated between egg counts, albuminuria and eosinophiluria as measured by the amount of cell bound ECP and EPX, or ECP in urine supernatants. No such correlations were demonstrated with the amount of EPX in the urine supernatants. Comparable amounts of ECP and EPX could be extracted from the urine deposits from infected children, but due to the high amounts of EPX in urine deposit extracts from controls, extracted ECP gave the best discrimination between infected and non-infected children. While albuminuria disappeared in most children at the 6 week post-treatment follow-up, eosinophiluria persisted in a significant proportion of the treated children indicating continued eosinophil activity in the bladder wall. Detection and quantification of early acute inflammatory reactions using ECP/eosinophils in combination with detection of later stages of bladder pathology using ultrasound may allow for a dynamic evaluation of the pathological process, the morbidity development and post treatment pathological changes in S. haematobium infections.