Caractérisation des formes matures de dissémination des Protozoaires et Helminthes intestinaux dans le réseau hydrographique de la Mezam (Région du Nord-Ouest, Cameroun) et influence des variables abiotiques

Abstract

The intestinal Protozoa and helminths show various forms of resistances in the water system (cysts and oocysts for Protozoa; eggs and larvae for Helminths). Their presence in the surface water constitutes a public health problem and must have special attention. The comprehension of the abiotic factors in favor of the distribution of these parasites in water together with the control of their maturation stages are necessary to understand the ecology of these parasites and their contribution to the activation, viability and transmission of diseases. This study aimed at evaluating the biodynamic of the environmental forms of enteric Protozoa and Helminths in relation with the physicochemical parameters of water in the Mezam hydrographic network system in Bamenda. More specifically, to evaluate the main hydrological and physicochemical parameters of these water, to characterize the different environmental forms of enteric Protozoa and Helminths in these waters and to evaluate the influence of physicochemical parameters on the distribution and the maturation of enteric pathogens in these aquatic environments. For this study, 13 sampling stations where selected divided into 3 sampling points for each stream (Mufueh, Formuki, Mankon and Ayaba) and 1 sampling station in the Mezam river. In each of these sampling points, 13 sampling campaigns were conducted from january 2017 to january 2018 following the monthly frequency. The hydrological and physicochemical parameters and the heavy metals were analyzed in the field and in the laboratory according to the standard methods. The isolation, identification and enumeration of the parasites were carried out using microscope at 40x and 100x after concentration and coloration of parasites according to the techniques of sedimentation, Kato-Katz, Ritchie and Ziehl-Neelsen. The maturation rates have been done in the species Ascaris lumbricoides, Strongyloides sp., Isospora belli et Cyclospora cayetanensis. Physicochemical analysis show that the Mufueh stream and the Mezam river, which are located on the outskirts of the city with the abundant vegetation on the banks of rivers, showed well oxygenated water (65.57 ± 3.56%), low values of temperature (19.61 ± 1.59 °C), low mineralization (61.94 ± 41.20 μS / cm) and low organic pollution (2.41 ± 1.71 mg / L). The water of these streams are subject to domestic and agricultural pollution. On the other hand, the Formuki, Mankon and Ayaba streams that cross the urban center, are more polluted (2.0 ≤ IPO ≤ 3.6), with high values of temperature (22.05 ± 2.14 °C) and high mineralization (185.37 ± 122.71 μS / cm). This urban water is subject to domestic, municipal and agricultural pollution; and present higher values of metallic ions (16.31 mg / L) and heavy metals (5858 μg / kg) in sediments. Concerning the enteropathogenic Protozoa, biological analysis allowed to identify and to characterize 9 species belonging to 4 classes. The class of Sporozoan dominated with Cryptosporidium spp. (99 Oocysts / L), Cyclospora cayetanensis (94 Oocysts / L), Isospora belli (54 Oocysts / L) and Sarcocystis hominis (31 Oocysts / L). It was followed by the class of Rhizopoda who is represented by Entamoeba coli (71 Cysts / L) and Entamoeba histolytica (63 Cysts / L). The cysts of Giardia sp. (65 cysts / L) and Chilomastix mesnili (7 cysts / L) belonging to the class of Flagellates followed; and finally, the class of Ciliate who is represented by the specie of Balantidium coli (42 Cysts / L). The spatiotemporal distribution of enteropathogenic Protozoan showed high densities in the month of march during the rainy season at the Muf-upstream, Aya-middlestream, Mnk-upstream and Mez-potamon stations; and low densities at Aya-downstream, For-downstream and Muf-middlestream stations. The maturation or sporulation rates of these oocysts are 37.55% and 39.58% respectively for Isospora belli and Cyclospora cayetanensis and are higher in the dry season. Statistical analysis revealed positives correlations between the densities of enteropathogenic Protozoan, sporulated oocysts with suspended solids and dissolved oxygen; and negatives correlations between these parasites and some metallic ions (Ca2+, Mg2+, Cl-, K+, HCO3- and NO3-) (p≤0.05). Concerning the enteropathogenic Helminths, biological analysis allowed the identification and the characterization of 10 species belonging to 3 classes. In descending order of density are the class of Nematoda with Strongyloïdes sp. (141 Larvae / L), Ascaris lumbricoïdes (59 Eggs /L), Enterobius vermicularis (9 Eggs / L), Ancylostoma sp. (2 Eggs / L) and Trichuris trichiura (2 Eggs / L). It was followed by the class of Cestoda with Taenia sp. (30 Eggs / L), Diphyllobothrium latum (25 Eggs / L) and Hymenolepis sp. (11 Eggs / L). The least dominant class is the class of Trematoda represented by Schistosoma haematobium (2 Eggs / L) and Fasciola hepatica (1 Egg /L). The Mnk-downstream, Aya-upstream, Muf-upstream, Muf-middlestream and Mez-potamon stations were the most contaminated with enteropathogenic Helminth eggs and larvae; while Muf-downstream, For-upstream and Mnk-upstream showed low densities of these parasites. The maturation rates are 66.35% for the Ascaris lumbricoïdes specie and 28.48% for Strongyloïdes sp. and are higher during the rainy season, showing the role of humidity in the maturation of Helminths eggs and larvae. The statistical analysis (p≤0.05) show that Helminths eggs and larvae show negatives correlations with temperature, salinity, heavy metals and have great affection with environments which have low or moderate organic pollution and rich in dissolved oxygen. These results show the bioaccumulation effect of heavy metals by intestinal parasites in the water. Respecting basic hygienic rules as well as treating water before use would reduce the risk of contamination of the population.