Effect of the change in energy reserves on the entomopathogenic nematode efficacy

The free-living infective juveniles of the entomopathogenic nematodes are non-feeding, so the stored energy reserves in these juveniles are of great importance. The relationship between the energy reserves and the efficacy of the entomopathogenic nematodes of genera Heterorhabditis and Steinernema was studied. New progenies of S. riobrave and H. bacteriophora [ISK-2 strains], were obtained using the continuous culturing method of nematode juveniles [IJ[s], for the several cycles under the optimum condition of the temperature [25°C] and nematode density [20 IJs/ larva], inside the host Galleria mellonella. Thus, the nematode efficacy was maximized with a high conservation of energy reserves. The results showed that there was an increase in the penetration rate and the virulence through the new progenies of S. riobrave and H. bacteriophora than in the original progenies, with an increase in the energy reserves

Biological and morphological changes in worms in mixed infection of Schistosoma mansoni and Schistosoma in hamsters

Hamsters infected with Schistosoma mansoni and S. Haematobium either simultaneously or after the maturation of an initial infection with either schistosome species were examined to estimate the biological and morphological changes under mixed infection conditions. The results indicated a high level of acquired resistance. The degree of immunity was evidenced by the significant reduction in the worm load as well as in the size of mature worms. Some disturbance was observed in the worm distribution. The results were important for epidemiological and immunological uses as well as in the development of a vaccine from one species that might be effective against both species

Cellular response to Schistosoma mansoni infection in Biomphalaria alexandria strains selected for susceptibility and resistance

Exposure of juvenile and adult Biomphalaria alexandrina to Schistosoma mansoni miracidia resulted, typically, in three susceptibility patterns: a]non-infected snails b] normal infections, and c] retarded infections. Under laboratory conditions, a vigorous resistant-type cellular response to invading miracidia was seen in the histological sections of non-susceptible snails. Accordingly, they were classified as resistant snails. Data pertaining to the influence of host size on suceptibility to S. mansoni indicates that adult snails [i.e.10-20 mm shell diameter] were significantly less likely to harbour sporocysts than juvenile ones [i.e. 5-10 mm shell diameter]. Cellular reaction to the infection varied with sporocysts location and length of infection. At 2 days post exposure [DPE], most sporocysts were viable. Approximately 8-12% of the sporocysts had elongated shaped transverse constriction and were categorized "normal", while those showing no elongation were categorized "retarded". All remaining sporocysts at 4 DPE were categorized "dead" while at 30 DPE most sporocysts were "amorphous" with eosinophilic masses. Although encapsulation of sporocysts never occurred in susceptible snails, haemocyte aggregations could sometimes be observed in the proximity of well developed sporocysts. In resistant snails, this cellular response continued to increase and resulted in the encapsulation of the sporocysts. In susceptible snails, the nucleus of secretory cells of the albumen cytoplasm were different in susceptible and resistant snails