COMPARATIVE EFFICACY STUDY OF DIMINAZENE ACETURATE, KAEMPFEROL AND THEIR COMBINATION ON EXPERIMENTAL Trypanosoma brucei bruceiINFECTION IN MICE

Abstract

In this study, the comparative efficacy study of kaempferol, diminazene aceturate and their combination against experimental Trypanosoma brucei brucei infection in mice was determined. Thirty six adult swiss albino mice both sexes weighing between 18 and 22 grams were randomly divided into six groups (I, II, III, IV, V and VI) of six mice each. Mice in group I were neither treated nor infected (un-infected, normal control). Mice in group II were pre-treated prophylactically with kaempferol (1 mg/kg per os) for 14 consecutive days prior to infection. Mice in groups II to VI each were inoculated with blood containing Trypanosoma brucei brucei (106 trypanosomes/ml of blood/animal) intraperitoneally (I.P). Following detection of parasitaemia, mice in group III were treated once with diminazene aceturate (3.5 mg/kg) I.P only. Mice in group IV were treated with diminazene aceturate (3.5 mg/kg) once I.P, and then continued with kaempferol (1 mg/kg per os) for nine consecutive days. Mice in group V were treated with kaempferol (1 mg/kg per os) only for nine consecutive days. Mice in group VI were given normal saline (5 ml/kg per os) only for nine consecutive days. Nine days post-infection, all mice were sacrificed by severing their jugular veins, blood samples were collected for haematological and biochemical analyses, while tissue samples were collected for histopathological examination. The results obtained showed significant differences between the levels of parasitaemia and survival rate of mice in groups II and VI. Following infection with Trypanosoma brucei brucei mean packed cell volume, haemoglobin concentration and red blood cell count significantly (P < 0.05) decreased in groups II and VI when compared to groups III, IV and V. Similarly, Mean corpuscular volume and mean corpuscular haemoglobin concentration significantly (P < 0.05) decreased in groups II and VI when compared to groups III, IV and V. The percentage of red blood cell haemolysis at 0.5%, 0.7% and 0.9% NaCl concentrations was significantly (P < 0.05) higher in groups II and VI when compared to groups III, IV and V.

Total leucocyte count significantly (P < 0.05) decreased in groups II and VI when compared to groups III, IV and V. The mean lymphocytes and neutrophil count reduced significantly (P < 0.05) in groups II and VI when compared to groups III, IV and V. There were significant (P < 0.05) increases in the mean alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase in groups II and VI when compared to groups III, IV and V. Antioxidant enzymes; superoxide dismutase, catalase and glutathione peroxidase increased significantly (P < 0.05) in groups III, IV and V when compared to groups II and VI. Serum level of malondialdehyde significantly (P < 0.05) increased in groups II and VI when compared to groups III, IV and V. In conclusion, kaempferol possesses antitrypanosomal activity and probably stimulate host immunity to control the proliferation of the parasite in the blood.

CHAPTER ONE

1.0 INTRODUCTION

1.1 Background of the Study

Trypanosomosis is a disease caused by the protozoan parasite from genus Trypanosoma and transmitted by the tse- tse fly (Glossina species) and other biting flies (Masocha et al., 2012), making the incidence of the disease to be of great concern in the tropics (Anosa et al., 1983). The trypanosomes which affect both man and animals have been subdivided into two, namely the haematic groups (Trypanosoma congolense and T. vivax) which always remain in the plasma of the host‘s blood and the tissue invading group (T.brucei, T.evansi, T.rhodesiense, T.gambiense and T. equiperdum) which are found extravascularly and intravascularly (Anosa et al., 1977).

African animal trypanosomosis or nagana is a disease caused by T. congolense, T. vivax and T. brucei spp. In wild animals, these parasites cause relatively mild infections while in domestic animals they cause a severe, often fatal disease (Molyneux et al., 1996). All domestic animals can be affected by nagana and the symptoms are fever, listlessness, emaciation, hair loss, discharge from the eyes, oedema, anaemia, and paralysis (Masocha et al., 2012). As the illness progresses the animals become progressively weak and eventually become unfit for work, hence the name of the disease “N’gana” which is a Zulu word that means “powerless/useless” (Molyneux et al., 1996). Because of nagana, stock farming is very difficult within the tsetse belt. The available means of control involves tsetse control, chemoprophylaxis, chemotherapy and use of trypanotolerant livestock. At present, control of trypanosomosis is chiefly done by chemotherapy and chemoprophylaxis using the following drugs: Diminazine, Homidium, and Isometamidium (Leach and Roberts, 1981; ILRAD Reports, 1990). Diminazene aceturate is probably the most commonly used therapeutic agent for trypanosomosis in livestock in Sub-Saharan Africa (Geerts and Holmes, 1998), even in Nigeria. However, complete dependence on drugs in many situations of trypanosomosis has been hampered in many areas by their toxic effects, high cost and frequent development of resistance to these drugs by the parasites. This is considered a very serious problem in trypanosomosis control in Africa (Geerts and Holmes, 1998). This results from the fact that the drugs effectively eliminate the parasites from the blood stream and the animal appears recovered, and then undergoes relapse infection which may be characterized by severe neurological infection leading to the death of the affected animal. In Nigeria, the occurrence of drug resistance to available trypanocides has been attributed to the presence of fake drugs, abuse of the existing drugs and inadequate dosing of the drugs in trypanosomosis therapy (Ezeokonkwo et al., 2010). Therefore, the current challenge to the majority of African pastoralists is to optimize the use of the relatively old existing drugs (Ezeokonkwo et al., 2010). In view of this, the use of drug combinations, new therapeutic regimens and the use of Slow Release Devices (SRD) of existing trypanocides have been suggested (Geerts and Holmes, 1998).

Secondary metabolites in plants including flavonoids are responsible for a variety of pharmacological activities (Mahomoodally et al., 2005; Pandey, 2007), recent interest in these substances has been stimulated by the potential health benefits arising from the antioxidant activities of these polyphenolic compounds (Pandey, 2007). The beneficial health effects of flavonoids have also been related to their antioxidant, anti-inflammatory, antiestrogenic, cardioprotective, cancer chemopreventive, neuroprotective, antidepressant and anxiolytic effects (Butterweck et al., 2000).

Kaempferol is a natural flavonol, a type of flavonoid, found in a variety of plants and plant-derived foods. Kaempferol acts as an antioxidant by reducing oxidative stress. Many studies suggest that kaempferol may reduce the risk of various cancers, and it is currently been studied for possible treatment of cancer (Leopoldini et al., 2006).