1.1 BACKGROUND OF STUDY
Most of traditional medicines are of plant origins. Nature has gifted us with so many medicines infused in the roots, leaves, stocks and barks of plants. Biological active principles isolated from different parts of plants are involved or employed in therapeutic measure of many pathological diseases and many more. Compounds belonging to natural products are the phytochemicals (such as flavonoids, saponin, triterpenes, alkaloids etc.) which are able to inhibit the growth of trypanosomes in humans and livestock animals are employed (plant extracts).
Trypanosomiasis is any tropical disease caused by trypanosomes and typically transmitted by biting insect especially sleeping sickness and chagas disease. It is an important infection that greatly affects humans and livestock in Africa; African trypanosomiasis also known as “sleeping sickness” in humans or “nagana” in animals (Atawodi, 2005; Welburn et al., 2009). It is one of the neglected parasitic diseases that affects human health and also largely accounts for the low livestock productivity of the African continent (Welburn et al., 2006). The disease is caused by extracellular parasites called trypanosome and the important species include Trypanosomabrucei, Trypanosomaevansi, Tryanosomacongolenseand Trypanosomavivax (Mbaya et al., 2009). The clinical signs of infection include; Anemia, intermittent fever, Jaundice, progressive emaciation, loss of production, weakness, and death ultimately. (Mercuria and Gadisa, 2011).
Fortunately, the continent is endowed with tremendous medicinal plant resources that are traditionally utilized for the treatment of the disease. However, in the context of the efforts to improve the therapy of these diseases, natural products could be a source of new drugs with high activity and low toxicity. Plants have been traditionally used for treatment of disease of different aethiology. Especially in the last decade, phytotherapy has received considerable attention in the search for alternatives to chemotherapy in parasitic disease control. Interestingly, scientific investigations have confirmed the efficacy of many of these African medicinal plants as antitrypanosomal agents under in vitro and/or in vivo conditions.
1.2 STATEMENT OF RESEARCH PROBLEM
Combating trypanosomiasis or sleeping sickness is still a major health challenge in sub-Saharan Africa (Ogbunugafor et al., 2008). Trypanosomiasis caused by flagellated protozoa parasites-trypanosomes; infects both humans and liverstock and is a reemerging disease (WHO, 2000; Scovil et al., 2001; Minshina et al., 2007). Animal trypanosomiasis causes an estimated economic loss of US$4.5 billion each year (TDR, 2005). African trypanosomiasis is responsible for 3 million livestock death and the death of about 55 000 people annually (Abenga et al., 2002; Mulumba, 2003). Annual loses have been estimated to amount to over 500 million US dollars in meat, milk, lost in traction power, control programme and in annual administration of about 35 million doses of trypanocidal drugs in Africa (Geerts, 2001). Food and Agriculture Organization of the United Nations (FAO) report indicates that trypanosome-induced annual losses in cattle production alone were estimated in the range of 1.0-1.2 billion US dollars in sub-Saharan Africa (FAO, 2002). The research for vaccine remains elusive and the prospects of prophylactic immunization are poor since the parasites change their surface coat to evade the host immune system in the process known as antigenic variation (Burchmore et al., 2002). Existing trypanosides are faced with drug resistance, toxicity and a lack of guaranteed supply (Burchmore et al., 2002; De Koning, 2001). Drugs remain the principal means of intervention. The infection contributes to poverty more through its effect on livestock than through its effects on humans. This makes it expedient for scientist to intensify the search for leads from medicinal plants used in ethno medicine for the treatment of trypanosomiasis. Finding trypanocides from medicinal plants offers a real hope for the control and management of this disease, within the context of the economies of the countries to which this disease is endemic.
Traditional medicine practitioners in Africa particularly Nigeria, use many plants for the treatment of sleeping sickness (Ogbunugafor et al., 2008). Plants such as Khaya senegalensis, Annona senegalensis, Azadirachta indica, Allium sativum need to be exploit for new and effective medicines that are less expensive and affordable to the poor and affected population. A number of these plants have been reported in literatures to exhibit trypanocidal activity (Wurochekke and Nok, 2004; Atawodi, 2005) but no much work have been done to evaluate for their various biochemical effects of all their plant parts (plant extracts) especially their roots. For these reasons however, this present research sort to fill in the gap by using these plants extracts (methanolic extract) to test for their antitrypanosomal effect which will help prevent loss in livestock production and will safeguard the lives of both the cattle, cattle rearers and the community at large.
A lot of work has been done and literatures presented on anti-trypanosomal activity revealing the promising ameliorating potentials. Atawodi et al, (2003) reported the in vitro anti-trypanosomal activity of methanolic extract of the bark of Khaya senegalensis and found that it was strongly active against both Trypanosoma congolense and Trypanosoma brucei gambiense at a dose of 4mg/mL. Adeiza et al, (2010) also reported an in vitro antiTrypanosoma evansi activity of the stem bark aqueous and methanolic extracts at a relatively high concentration of 20mg/mL.
Mbaya et al., (2010) administered 400mg/kg of stem bark ethanolic extract of Azadirachta indica, increase the pack cell volume and the survival period of trypanosome-infected animals.
Diallyl-disulfide (DAD) from the pulp of Allium sativum, was proven to be responsible for the in vitro and in vivo antitrypanosomal properties of the plant through disruption of membrane lipid synthesis in parasites (Nok et al., 1996).
The in vitro antitrypanosomal activities were reported for both petroleum ether and dichloromethane root extracts of Annona senegalensis with an MIC (Minimum Inhibitory Concentration) value of 50ug/mL (Ibrahim et al., 2014).
As a matter of confirmation to the above research, we sort to explore several parts to test for their antitrypanosomal activities and the natural products derived from these plants will offer novel possibilities to obtain new drugs that are active against trypanosomes (Hoet et al., 2004).More so, the discovery of these potent antitrypanosomal extracts from these plants will increase the great potentials of these plant to provide lead compounds for the development of new natural drugs and possible combine therapy for effective treatment of sleeping sickness (Mann et al., 2011) that will be of low toxicity, cheaper to poor communities and help prevent loss in livestock production and also protect the lives of both the cattle, cattle rearers and to a large extend, the community.
1.4 AIM AND OBJECTIVE
To determine the effect of some Africa medicinal plants extracts with antitrypanosomal activity.
To evaluate in vitro effect of methanolic extracts of some selected plant parts against Trypanosoma brucei brucei