EVALUATION OF MOLLUSCICIDAL ACTIVITIES OF CRUDE AND ALKALOIDAL FRACTION OF ANOGEISSUS LEIOCARPUS (AFRICAN BITCH) AND PSEUDOCEDRELA KOTSCHYI (DRY ZONE CEDAR) ON VECTOR OF SCHISTOSOMIASIS

ABSTRACT

Over the years, the use of plant-based molluscicides has received substantial consideration in the satisfaction for cost-effective alternatives to chemotherapy and synthetic molluscicides in schistosomiasis control. This study was aimed at evaluating the molluscicidal potentials of crude and Alkaloidal fractions of Anogeissus leiocarpus and Pseudocedrela kostchyi against vector of schistosomiasis. Both aqueous and methanol crude extracts of the plants were tested for the presence of bioactive metabolites. Ten snails each was exposed to different concentrations (10 mg/L, 20 mg/L, 40 mg/L, 80 mg/L, 160 mg/L, 200 mg/L and 300 mg/L) of aqueous, methanol and alkaloid extracts of Anogeissus leiocarpus and Pseudocedrela kostchyi for the interval of 40 minutes, 24 hours and 72 hours respectively. Fifty other snails were also exposed to 200 mL of distilled water for 24 hours as control. The results indicated the presence of phytochemicals such as flavonoid, Tannis, Saponins, Alkaloids and terpenoids  in  both  aqueous  and  methanol  extract  of  both  plants.  Steroid  was  only present in methanol extract. Cardia glycoside was absent in aqueous extract of the extracts. The results showed dose dependent activities with highest dose having a significant (P<0.05) highest snail mortality. The two plants extracts showed appreciable molluscicidal efficacies against the two exposed snail species with LC50  of 157.29, 88.56, and 240.03mg/L for aqueous, methanol and Alkaloidal fraction of A. leiocarpus against B. pfeifferi and LC50 of 128.73, 78.07 and 344.02mg/L for P. koschyi respectively. There was a significant decrease in the level of Alamine transaminase (ALT) and Aspartate triaminase (AST) in the tissue of the exposed snail compared to the control. Based on the findings of this study, there is need to examine the Histoachitecture of the exposed snail in other to ascertain the observed mechanism of action found in the alteration of the tissue enzymes.

CHAPTER ONE

1.0      INTRODUCTION

1.1       Background to the Study

Schistosomiasis (also known as Bilharzia) is a debilitating disease caused by species of parasitic worms or helminths of the genus Schistosoma, which are also known as blood flukes (Kimeu et al., 2015). Globally, Schistosomiasis is the second most prevalent parasitic disease in Africa ranked only after malaria regarding the number of infected people and those at risk (Grimes et al., 2014). Bilharzia is of great public health and social economic importance in the developing world. WHO, (2015) reports estimate that 500-600 million people in 74 tropical and sub-tropical countries are at risk of Schistosomiasis.  Over 200  million  people  in  these  countries  are  infected,  85%  of whom  live in sub-Saharan  Africa where S. haematobium, S. intercalatum S. and S. mansoni are endemic. Nigeria is said to be highly prevalence with an estimated 101 million at risk and 26 million people infected (WHO, 2015).

Schistosomiasis  is  caused  by  digenetic  trematodes  belonging  to  phylum Platyhelminthes, super family Schistosomatoida, and genus Schistosoma. It is usually attributed to three species, subdivided into intestinal Schistosoma mansoni and Schistosoma japonicum or urinary Schistosoma haematobium types, according to the site preferred by the adult worms. In Nigeria, the two main species of Schistosomiasis reported are Schistosoma mansoni and S. haematobium whose intermediate hosts are fresh water snails, Biomphalaria pffeiferi, and Bulinus trancatus respectively. Two host have been attributed to the life cycle of schistosome, namely; a definitive host (man) where parasite undergoes sexual reproduction, with a single intermediate snail host, where there are number of asexual reproduction stage risk (Grimes et al., 2014). In humans, these blood flukes reside in the mesenteric and vesicle venules. They have a life span of many years and produce large numbers of eggs daily, which must traverse the gut and bladder tissues on their way to the lumens of the excretory organs. Many of the eggs remain in the host tissues, inducing immunologically mediated granulomatous inflammation and fibrosis. Heavy worm burdens may produce hepatosplenic disease in Schistosoma mansoni and S. japonica and urinary tract disease in S. haematobia. Since both the schistosomes and the eggs utilize host metabolites, and because the host responses to the parasite are affected by its nutritional status, malnutrition strongly affects both the parasite and the complex host-parasite relationship (Victor, 2014).

At least four approaches to controlling infection have been tried at the community level. These are control of snails, public health education, sanitation, and community-based chemotherapy  employing  praziquantel.  Selective  molluscicide  treatment  in  snail- infested bodies of water at main human contact points is the preferred way to approach controlling snail populations (Mwonga et al., 2015). Three drugs have been used for schistosomiasis treatment. These are Praziquantel (effective in the treatment of all forms of schistosomiasis, with hardly any side effects), Oxamniquine (used to treat intestinal schistosomiasis), and Metrifonate (effective for the treatment of urinary schistosomiasis (CDC,2011). Praziquantel has been found to be more effective in treating S. haematobium infections compared to metrifonate and more effective in treating S. mansoni when compared with oxamniquine because it is effective when treating advanced hepatosplenic schistosomiasis, with few side effects. Praziquantel is currently the drug of choice for treatment of any kind of schistosomiasis. The main limitation is the cost which restricts its use in many developing countries. Unfortunately, the long- term worldwide application of Praziquantel coupled with the recent discovery of Praziquantel-tolerant  schistosomes  has  generated  concern  over  the  development  of drugs-resistant Schistosoma strains. A large number of plant products, which possess molluscicidal activity, have been identified and  used for treatment of schistosomes (Mwonga et al., 2015).

Members of the kingdom Plantae are used medicinally in different countries and are sources of many potent and powerful drugs. Among several factors contributing towards the potential use of phyto-medicine are safety, lack of adverse reactions and minimal side effects which have been mostly found to particularly influence the use of such medicines  in  developed  countries  (Renckens  and  Dorlo,  2013)  as  most  of  the developing countries have adopted traditional medical practice as integral part of their culture. Similarly, herbal preparations represent one of the most important traditional medicine therapies and are still the backbone of majority of the world populations, mainly in the developing countries, for primary health care (Mukhtar et al., 2017).

In Nigeria, traditional herbal medicine, being a vital element in the cultural inheritance, remains the main source for a huge majority of people in treating various diseases and ailments. Anogeissus leiocarpus is a tree widely distributed in northern Nigeria. The bark and seed of the tree is used for the treatment and prevention of worm infestation in equine  species  (Ahmad,  2014).  Pseudocedrela  kotschyi  commonly  called  dry-zone cedar belongs to the family Meliaceae which grows in the savannah zone in tropical Africa from Nigeria. The bark decoction or macerations of the plant are applied externally to ulcers, sores, rheumatism, leprosy and itches. Internally they are used to treat fever, stomach-ache, diarrhea and dysentery and it is reported to possess anthelmintic effects on Ascaris suum. It is against this background that this study was designed to elucidate the bioactivities of the extract of Anogeissus leiocarpus and Psedocedrela kostchyi against vector and parasite of Schistosomiasis.

1.2          Statement of the Research Problem

In order to achieve effective Schistosomiasis control, there is need for intervention programs that are effective, reliable and sustainable. In addition, the control method(s) should have minimal environmental impact. Currently, control of Schistosomiasis relies heavily on diagnosis and mass chemotherapy principally using the drug, praziquantel (PZQ) (Doenhoff, et al., 2009). However, the prospect of relying on a single drug for a disease affecting 200 million people is an alarming situation (CDC, 2011). There is a lot of concern due to loss of Praziquantel efficacy and its inaccessibility and high cost requiring hard currency which set back helminthes control efforts. In addition, use of molluscicides in the control of Intermediate host snails is important in integrated Schistosomiasis control. Despite the great deal of attention directed to the control of aquatic molluscs using saponins- containing materials, no investigation is known to previously have been made to use these compounds to control Biomphalaria sp. This is so despite the significant problems posed by the snails in Schistosomiasis transmission. Synthetic  molluscicides  have  shown  a  number  of  drawbacks  including  high  cost, altering of the structure of the environment by acting as biocides and destroying flora and fauna of the ecosystem (Mwonga et al., 2015).

The near exclusive use of praziquantel (PZQ) for treatment of human Schistosomiasis has  raised  concerns  about  the  possible  emergence  of  drug-resistant  schistosomes. Further, some molluscicides like copper sulphate and sodium pentachlorophenate are general biocides and have been shown’ to destroy most aquatic organisms. They have high mammalian toxicity, and the durability of copper may result in a build-up of copper salts in the water after prolonged treatment. Also, Sodium pentachlorophenate is highly irritating (Grimes et al., 2014) and inhalation of the powder produces acute symptoms.  Sprayers  continually  using  this  substance  suffer  from  lacrimation  and chronic  coughs.  Therefore,  this  research  is  aimed  at  evaluating  native  plants  for potential active substances against vector and the parasite.

1.3       Justification of the Study

Schistosomiasis is a debilitating disease with 500-600 million people in 74 tropical and subtropical countries being at risk. Development of antischistosomal resistance in helminthes reported in a number of countries (WHO, 2015) gives a clear indication  that control programs based exclusively on their use are not sustainable. The molluscicidal and antischistosomal agents used conventionally to  control this disease have many setbacks besides being very expensive. Many plants have been investigated for molluscicidal and antischistosomal activities and have been found to exhibit some activity. Herbal medicines are cheap, more readily available to people and are less toxic, although a lot still needs to be done to confirm this (Mukhtar et al., 2017).

Continuous research for new drugs with high activity and reduced adverse effects is very important, especially considering that in Nigeria parasitic diseases still constitute a serious  public  health  problem,  in  spite  of  the  aggressive  control  over  the  years. Screening the biodiversity of the Nigerian plants can reveal new phyto-therapeutic drugs.   The biodiversity existing in the Nigeria flora is a potential source of many new bioactive molecules.

1.4       Aim of the Study

This study is aimed at evaluating the molluscicidal potentials of crude and Alkaloidal fractions of Anogeissus leiocarpus and Pseudocedrela kostchyi against Biomphalaria pfeifferi and Bulinus globossus as the vectors of schistosomiasis.

1.5      Objectives of the Study

The objectives of the study are to determine the:

i.         phytochemical constituents of the crude methanol extract of crude and

Alkaloidal fraction of Anogeissus leiocarpus and Psedocedrela kostchyi.

ii.         molluscicidal   activities   of   the   crude   extract   and   Alkaloidal   fraction   of

Anogeissus

leiocarpus and Psedocedrela kostchyi.

iii.         medial (LC50) and upper (LC90) lethal concentrations of the extraction host of

Schistosomiasisiv.  effect of the extracts on biochemical variables host of Schistosomiasis

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