Laboratory Observations on the Compatibility of Schistosoma Mansoni and Schistosoma Haematobium to their Intermediate Hosts from Different Parts of Sudan

Abstract

This investigation was conducted to provide some aspects of parasite aggregation, cercarial productivity and dynamics as well as snails\\\\\\\' sensitivity and compatibility. The selected study areas are: Khartoum, Gezira, Gunaid, New Halfa and Nuba Mountains, where intermediate-host snails (Biomphalaria pfeifferi and Bulinus truncatus) and parasites (Schistosoma mansoni and Schistosoma haematobium) were obtained. The compatibility of snails-schistosomes local strains and crosses infections on snails\\\\\\\' survival and the time needed for cercarial emission were assessed. The cercarial rhythmicity and production from each snail\\\\\\\'s schistosomes\\\\\\\' local strains and cross infections were determined, to elucidate cercarial peaks. In addition, the innate rhythm of cercariae and production from naturally infected snails was monitored to identify the most risky time for man to acquire infection. Lastly, the influence of chemotherapy repeations in hatchability of schistosomes\\\\\\\' eggs was assessed. The findings suggested that Khartoum, Gezira and Gunaid strains of Biomphalaria pfeifferi and Bulinus truncatus were highly susceptible to their local strains of miracidial attack and intra-molluscan development. The obtained figures stress that New Halfa strain of Schistosoma mansoni was very fatal to Biomphalaria pfeifferi, expressed in the highly significant snails\\\\\\\' mortality. Gunaid complex compatibility is significant compared to Khartoum and Gezira, expressed in more survival rates of snails that exposed to the same miracidial dosage. In addition, there is a significant early commencement of cercarial shedding in Gunaid, compared to Khartoum and Gezira, 28 days compared to 52 and 39 days, respectively. The number of snails shedding cercariae increased with increasing miracidial dosage, although there was no consistent relationship between the number of cercariae shed and number of infecting miracidia. Concerning the moist risky time for man to acquire infection, it appears from the manipulated averages of Khartoum and Gezira that schistosomes cercariae increased to peak at (09 - 03 PM), thenafter gradually declined to very few liberating individuals around sunset (05 - 07 PM). The cercarial fluctuation in Gunaid strain showed different general trend and apex, commenced with broad range and peaked at 01 – 03 PM, then suddenly decline around sun set. The relative incompatibility of the cross infections, compared to the local strains, was confirmed in monitoring the less frequencies in snails\\\\\\\' survival and the extended time for cercarial shedding. In all miracidial dosage, the numbers of the survived infected snails from Khartoum-Gezira cross infection were significantly less than those of the local Khartoum and Gezira strains, while the time needed for cercarial shedding was extended. The cercarial daily production of Khartoum-Gezira cross strain less than those of Khartoum local strain with three-folds, and than those of local Gezira with four-folds. This observation was also monitored in other complexes: Gezira-Khartoum, Khartoum-Gunaid, Gunaid-Khartoum, Gezira-Gunaid, Gunaid-Gezira, and New Halfa-Gezira cross infections. The obtained findings were discussed considering the extensive population movement to and from study areas coupled with the complete absence of national control programme for Bilharzia. For knocking down the transmission pressure of Bilharzia in the investigated schemes an array of practical recommendations were highly advocated to the Ministry of Health, Federal and State