Investigation on Infection of Trematodal Larvae in Snails in Taunggyi and Ayetharyar Areas, Myanmar

| During the study period, a total 1,632 snails belonging to eight species which act as intermediate host(s) of trematodes were collected by hand picking using the time-collection method from near watering points. Among them, 13.2% (216/1,632) snail samples were found to be infected with trematode larvae. Abundance of infected snails was higher in rainy season showing significant relationship with monthly temperature and monthly rainfall. Abundance of infected snails was higher in Taunggyi Township than in Ayetharyar Township.

larval stages within the snails is provided when rainfall exceeds transpiration and saturation is attained (Urquhart et al., 1996).In animals, the high prevalence of fluke infestation might be due to heavy contamination of snail habitats and ingestion of metacercariae as a result of high stocking density and local overcrowding around watering points (Keyyu et al., 2005;Kaur et al., 2013).
Numerous studies have been conducted regarding the investigation on the abundance and species of snails bearing trematodes larvae all over the world.However, in Myanmar, reports on the abundance of snails have not yet reported so far.Therefore, it is believed that the information on intermediate host snails in Taunggyi area could assist in the development of trematode infection control program in livestock production.Hence the present study was envisaged on the investigation on infection of trematodal larvae in snails in Taunggyi and Ayetharyar Areas, Myanmar.

STudy area and STudy Period
Snail sample collections were carried out from April 2012 to July 2012 in Taunggyi and Ayetharyar Townships, Southern Shan State. .

SaMPLe CoLLeCTion
Snail were collected from areas of snail habitat that were likely to be regularly contaminated with cattle faeces, for example, near paths emanating gateways, near watering points and favoured lying-up area (Figure 1).The snails were collected as per Gray and Parr (2000) through hand picking using the time-collection method that is, counting of total number of any snails collected during 30 -40 min at collection site.Collected snails were placed alive in plas-tic containers and labeled separately by location and date.
The examination and identification of larval stages of parasites (miracidium, sporocyst, rediae and cercariae) was performed as per the method of Claxton et al. (1997).All the snails were taken to the laboratory and each was crushed in a motor by using a pestle and crushed pieces were transferred onto a glass slide.A few drops of normal saline was put onto the slide and covered with a cover slip and examined under a stereo microscope (×100) for the presence of developmental stages of larval trematodes.

SPeCieS idenTifiCaTion of SnaiL
Species identification of snail was based on morphology as described in wikepedia (https://en.wikipedia.org) and Mackie and Claudi (2010).rainy seasons and Simple Linear Regression analysis was done to find out the relationship between the meteorological data and abundance of infected snails.All the analyses were performed at the significance level of 0.05.

rESultS
Based on the morphology of snail, ten different snail species could be identified.Among them, only 8 species were intermediate hosts of trematodes.Therefore, total number of collected intermediate host snails was 1,632 (Figure 2).
Among the observed intermediate host snail species, only 5 species (Figure 3), Lymnaea truncatula, L. luteola, Viviparus species, Melanoides tuberculata and Biomphalaria glabrata, were found to be infected with larval stages of trematodes (Figure 4).Physella acuta, Planorbis species and L. auricularia were free from any trematodal larval infection (Figure 5).Number of infected snails species in Taunggyi and Ayetharyar Townships was described in Figure 6.
The number of infected snails was significantly different among the months of study period.The number of infected snails was highest in July (98/612) and the followed by May (58/428), June (48/416) and lowest in April (12/176).
There was not significant difference in infected snails between May and June, and between June and April (Figure 7).The percentage of infected snails was significantly higher in rainy season (146/1,028) than that of summer season (70/604) (Figure 8).
According to Simple Linear Regression analysis, abun dance      Biomphalaria glabrata and Viviparus species were observed harbouring trematodes' larval infection as 10.5 % and 13 %, respectively.Biomphalaria glabrata is a vector of schistosomiasis .Viviparus species is host of many parasites in its native including cercaria, metacercaria, ciliated protozoans, annelids and chironomid larvae .Thus, it should be considered in the context of other concurrent trematode infections although trematodes of medical and veterinary importance, like the mammalian schistosomes do not occur in this study.
According to the findings of this study, the prevalence of infected snails was lower in the summer season (11.6%) than that of rainy season (14.1%).It was comparable with the finding of Rondelaud (1994) who stated that the number of released cercariae is low or none during summer; however, after rains, cercarial shedding immediately increase.As suggested by Rangel (1999) high temperature may cause a reduction in humidity, facilitating the dehydration of the snails and the desiccation of the green algae that are the main food source for the snails.The duration of the snails' viability is directly related to relative humidity and inversely to temperature and exposure to sunlight (Spithill et al., 1999).
In the present study, the abundance of infected snails had negative relationship with monthly temperature positive relationship with monthly rainfall.The high rainfall favours the development and survival of both the intermediate host snail and the developmental stages of the parasites (Torgerson and Claxton, 1999).The abundance of infected snails was higher in Taunggyi Township (74.4%) than that of Ayetharyar Township (25.6%).It can be explained that different abundance of infected snails in two townships may be due to locating at different altitudes.Taunggyi Township has more availability of suitable habitat for the snail vectors due to different altitude and rainfall.Therefore, it is clear that trematode infection in snail is spreading in this study area.The specific strains of trematodes larvae found in snails should be investigated by advanced molecular techniques for further studies.

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Figure 1 :
Figure 1: Collection site for snail; A) near dam; B) near lake

Figure 2 :
Figure 2: Number of intermediate host snails from different 8 species collected in study areaSTaTiSTiCaL anaLySiSANOVA 'F' was used to test the significance of monthly abundance of infected snail among the study months.Independent sample 't' test was used to compare the mean number of infected snail samples between summer and