1.1 Introduction
Trematode infections pose serious risk to the health of their vertebrate host, including humans and livestock, and could adversely affect both agriculture and economy (Yakhchali et al., 2005). Digenetic trematodes have a complicated life cycle, which gets initiated in their first intermediate hosts such as freshwater snails, which are widespread in water resources of most geographical regions; the larval stages such as sporocysts, rediae, and cercariae develop within snails (Curtis et al., 2007; Skála et al., 2014). Snails can be found in a very wide range of environments, including ditches, deserts, and the abyssal depths of the sea. Although land snails may be more familiar to laymen, marine snails constitute the majority of snail species, and have much greater diversity and a greater biomass (Wikipedia, 2021).
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Research hypothesis and questions, Limitations of the Study and Definition of technical terms.
1.2 Background of Study
Snails share intimate relationship with parasitic trematodes because they serve as resource for development and vehicle for transmission to its next definite host. A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name snail is also used for most of the members of the molluscan class Gastropoda that have a coiled shell that is large enough for the animal to retract completely into. When the word "snail" is used in this most general sense, it includes not just land snails but also numerous species of sea snails and freshwater snails. Gastropods that naturally lack a shell, or have only an internal shell, are mostly called slugs, and land snails that have only a very small shell (that they cannot retract into) are often called semi-slugs (Wikipedia, 2021).
Snails are rarely studied despite its niche and abundance in the ecosystem with many research to date limited to its focal bio-geographical distribution, biodiversity, and inventory (Gelen et al., 2015) also with few studies on snail identification using varied conchological parameters and molecular methods, little or less data on snail host parasite interaction have been recorded about this neglected tropical diseases (NTDs). Snails convey a variety of diseases, including schistosomiasis, paragonimiasis, dicrocoeliasis, fascioliasis, faciolopsis, etc which affects millions of people and are endemic to Africa, Latin America, Southeast Asia (W.H.O, 2010). In Nigeria, schistosomiasis is endemic with estimated 11million people infected and 101.28million people at risk (W.H.O, 2010). Since snails are obligatory hosts for the larval stages of schistosomes their examination provides important information on active transmission foci therefore both the parasite and the vector must be targeted in order to break the cycle of transmission.
Therefore, in Nigeria where the research was carried out, the activities that was conducted is to examine the Cercariae Shedding of Trematodes and their Associated Snails Intermediate Host.
1.3 Statement of Problems
Investigation revealed that snails, as first intermediate hosts of trematodes, can cause health hazards in animals and humans. Recently, WHO has included Iran among six countries known to have a serious problem with fascioliasis. In addition, Cercarial dermatitis is a job related disease that is seen often in paddy workers and swimmers. In our country, many studies have been conducted to survey larval trematodes in freshwater snails. However, to the best of our knowledge, there are no comprehensive data regarding the infection of gastropods. It difficult to detect when and where transmission actually occurs without undertaking snail surveillance. Since snails are obligatory hosts for the larval stages of schistosomes their examination provides important information on active transmission foci therefore both the parasite and the vector must be targeted in order to break the cycle of transmission.
1.4 Aim and Objectives of Study
The aim of the study is to scrutinize the Cercariae Shedding of Trematodes and their Associated Snails Intermediate Host. In achieving this aim, the following specific objectives were laid out as follows:
- To evaluate trematode cercariae infection of snails in Delta State,
- To estimate the types and prevalence of cercarial infection in snails,
- To determine the distribution of snails of possible medical and veterinary importance and the cercarial release pattern in Delta State.
1.5 Research Questions
The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:
- Does Trematode cercariae infection affect snails in Delta State?
- What are the types and prevalence of cercarial infection in snails?
- What is the distribution of snails of possible medical and veterinary importance and the cercarial release pattern in Delta State?
1.6 Significance of Study
This study will be of immense benefit to researchers who intend to know more on this study and can also be used by non-researchers to build more on their research work. This study contributes to knowledge and could serve as a guide for other study.
1.7 Scope of Study
The scope of the research is focused on the Study of Cercariae Shedding of Trematodes and their Associated Snails Intermediate Host in Delta State.
1.8 Limitations of the Study
During the course of this study, many things militated against its completion, some of which are:
- Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
- Research material: availability of research material is a major setback to the scope of the study.
- Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
- Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet, questionnaire and interview).
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