Biological Control of Lymnea natalensis snails using a Molluscicidal Indigenous Plant Pulicaria crispa (Frosk) Oliv. Compositae

Abstract

This study was conducted to investigate molluscicidal potency of the indigenous herb Pulicaria crispa (Eltagar) against Lymnea natalensis snails, the intermediate host of Fasciola gigantica as possible means of control of animal fascioliasis in the Sudan. A study of epidemiology of fascioliasis was done in northern part of Gazira Scheme and Khartoum State (Soba, EI Bagair, EL Hafear and Kab EL gidad area). The snails were collected from the minor canals and ponds. The seasonal fluctuation of Lymnea spp. population and their transmission pattern was recorded. The results revealed that the average population of Lymnea spp. was not similar in the four sites.The number of snails increased during summer and rainy season and decreased during winter. The snail infection rate varied between 17% and 29% and the highest rate of infection was during May and the lowest during December. Thirty per cent of cattle examined in the area were found infected with fascioliasis. Field evaluation of the molluscicidal activity of P. crispa whole plant was carried out against L. natalensis. The plant was collected from Soba area. It was air dried under shade. The Canal used was at the irrigated land in the premises of the Central Veterinary Research Laboratories Centre, Soba. The canal was divided into five equal sections where equal numbers (100) of L. natalensis were put in separate cages and exposed to different doses of the aqueous extract of P. crispa. The results were analyzed using probit analysis. The assessment of the plant activity was based on calculating the lethal dose for 50% and 95% of the snails (LD50 and LD95). The aqueous extracts of P. crispa showed a high molluscicidal potency against L. natalensis without toxic effects to non target organisms. Toxicology screening of P. crispa was carried out by studying clinical, biochemical and pathological effects of orally dosing 20 Nubian goats with the aqueous extract of P. crispa. The goats were divided into four groups. Each group was given a different dose. Blood samples were collected for haematological and biochemical investigations. The results showed that there are no deviations from the normal health of the animals. The red blood cells white blood cells, packed cell volume and haemoglobin concentration were not affected and there were no significant changes in the normal levels of the total protein albumin, creatinine and urea. No histopathological changes were observed. The ability of P. crispa in changing chemical and/or physical properties of canal's water was tested. Water samples analysis showed that chemical and physical properties of water appeared within the normal level and not exceeding the maximum allowable concentrations according to Sudanese standards (1989).

PREVENTIVE MEDICINE AND VETERINARY PUBLIC HEALTH