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Distribution Patterns of Vector Snails and Trematode Cercaria in Their Vectors in Some Selected Areas of Mymensingh

Z. Islam
Department of Parasitology, Bangladesh Agricultural University, Mymensingh

M. Z. Alam
Department of Parasitology, Bangladesh Agricultural University, Mymensingh

S. Akter
Department of Parasitology, Bangladesh Agricultural University, Mymensingh

B. C. Roy
Department of Parasitology, Bangladesh Agricultural University, Mymensingh

M. M. H. Mondal
Department of Parasitology, Bangladesh Agricultural University, Mymensingh

Abstract/ Executive Summary:

Different species of vector snails carry larval stages of different trematodes. Studies were performed to investigate different snail species and parthinate of trematodes carried by them, in some selected areas of Mymensingh Sadar, Mymensingh. Snails were collected by hand picking method and examined after crushing. Among 864 tested snails, it revealed the presence of six species of snails like Lymnaea auricularia 145 (16.8%), Lymnaea luteola 205 (23.7%), Indoplanorbis exustus 273 (31.6%), Vivipara spp. 164 (18.9%), Brotia spp. 35 (4.1%) and Pila spp. 42 (4.8%) in the study areas. Among them 5.8% L. luteola and 6.2% L. auricularia were infected with gymnacephalus cercariae. Again, 1.4% L. auricularia and 1.8% I. exustus were infected with echinostome cercaria. In this study, 1.8% Vivipara spp. and 2.6% I. exustus were positive for furcocercus cercaria. On the other hand, 1.8% Vivipara spp. was positive for xiphidocercus cercariae and 1.8% I. exustus was also positive for amphistome cercariae. One or more species of snails were found to harbor single or mixed types of cercariae such as gymnacepahlus, echinostome and furcocercous. Population densities of different species of snails were determined in per unit time which were statistically significant (p<0.01). More studies are needed to focus on the determination of different vector snails and cercariae carried by them throughout the Bangladesh especially from plain lands, hilly areas, alluvial lands and coastal areas during four conventional seasons.

Keywords: Vector snails, Trematode cercaria, Distribution, Mymensingh

Location: Mymensingh Sadar, Mynensingh.

Start Date: 00-03-2011

End Date: 00-05-2011

Program Area: Animal Health and Management

Commodity: Aquatic animal

Objectives:

To collect and identify the fresh water snails from different pools of water in some selected areas of Mymensingh Sadar for the determination of snail density; and examine the cercariae developing in these snails.

Methodology:

Snails and other related materials e.g. water, soil etc. were collected from snail inhabited areas in some selected areas of Mymensingh Sadar, Mynensingh from March 2011 to May 2011. All laboratory activities were performed at the laboratory of Parasitology Department, Bangladesh Agricultural University, Mymensingh. A total of 864 aquatic snails were collected from different ponds, marshy lands (beels), irrigation channels & rice fields, drain, lake and river (Bhramaputra). The snails were either collected with handpicked method or with the help of scooped-net. After collection, the snails were kept in plastic container with perforated lids, and containing saline, brought to the laboratory and washed in running tap water for 15 minutes. Snails containing different water vegetation and other debrises on the shells were cleansed with soft brush and washed in running tap water. The snails were identified by their characteristic shell characters. The snails were placed individually in test tubes or glass petridishes containing saline and subjected 60 W bulb heats to liberate cercariae slowly. The snails from which cercariae did not emerge were crushed softly with the help of morter and pastle to examine their viscera. The visceral organs of the Lymnaeidae snails were taken out easily by slow and gentle traction with the help of a curved needle. The shells were separated by the needles and the entire alimentary tract and the associated glands were placed in normal saline and dissected for the detection of parthinate. These were dissected and processed for histological examination to detect the presence of parthinate. The examination was first made under stereomicroscope. In the positive cases, living cercariae were drawn with the help of a medicinal dropper and placed on glass slide. The cercariae were examined under high power objective after adding a drop of 1% methylene blue with the motile cercariae. Identification of different types of cercariae was done. The population density of snails in per unit time was determined. This technique involves counting the number of snails that are collected systematically with sieves mounted on handles or handpicked by one or more experienced collectors in a measured and marked area of the habitat for a given interval of time usually per hour. The physical condition of water such as transparency, presence or absence of water current and depth of water of a particular habitat of snail were recorded. For determination the pH of water, at least 60 ml of water from each habitat was carried to the laboratory in plastic or glass bottles. The pH was determined by Glass Electrode pH Meter. The water vegetation available in a particular snail habitat was studied. The special affinity and attachment of snails with the vegetation was recorded. The soil of a particular habitat was studied. At least 100 grams of soil was collected from different parts of a particular habitat, dried up and mixed thoroughly and the nature of the soil was determined. The pH of soil was determined by Glass Electrode pH Meter. The meteorological data were collected from the meteorological station located at the Bangladesh Agricultural University Campus, Mymensingh in every month to correlate the prevalence of snails, cercariae, snail density and snail ecology with the temperature, rainfall and humidity. Statistical analysis of the prevalence of cercariae in snails and the climatic factors were determined by using Pearson Chi-Square test and F test.

Source of Information: J. Environ. Sci. & Natural Resources, 5(2): 37- 46, 2012; ISSN 1999-7361

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The present study provides some basic idea about different snail species with different cercarial infections, snail habitat together with their density in Mymensingh Sadar, Mymensingh; thus creating a basis for further investigation. Detail research work focused on the determination of different vector snails and cercariae carried by them throughout Bangladesh especially from plain lands, hilly areas, alluvial lands and coastal areas in the four conventional seasons such as winter, summer (pre-monsoon), rainy (monsoon) and autumn (post-monsoon) is warranted.

Knowledge Management: Journal