Evaluation of Some Natural and Synthetic Products against African Trypanosomiasis

Evaluation of Some Natural and Synthetic Products against African Trypanosomiasis.

ABSTRACT

The chemotherapy of African trypanosomiasis, a fatal protozoal disease of man and animals is beset with many problems including a limited repertoire of expensive compounds, drug toxicity and resistance and protracted treatment protocols. In order to improve chemotherapy, some natural and synthetic products were evaluated against African trypanosomiasis using in vitro and in vivo assays.

Honey, extracts of Brassica oleracea and of frog and snakes (viper and cobra) skins were assessed. Cymelarsan was evaluated in Trypanosoma brucei brucei and Trypanosoma evansi infections of albino rats and rabbits; and verapamil in the reversal of T. Evansi resistance to cymelarsan, using parasitaemia and antigen and antibody enzyme linked immunosorbent assay.

Five products were assessed for tsetse fly repellent activity. Oral combination administration of difluoromethylornithine (300 mg/kg), chloroquine (50 mg/kg) and honey (50 mg/kg) was evaluated in trypanosome infected albino rats. Topical application of melarsoprol, ethidium bromide and diminazene aceturate singly and combined with cattle butter (ghee) and shea butter was evaluated in infected mice and rats.

Three groups of sleeping sickness patients were diagnosed and treated at Ethiope East, Delta State, Nigeria as follows: first group (pentamidine i.m. 4 mg/kg body weight for 10 days). Second group (melarsoprol i.v. 1.8 – 3.6 mg/kg for 3 weeks plus prednisolone orally 1.0, 0.7 and 0.5 mg/kg daily for the first, second and third weeks respectively; third group (a single i.m.

Injection of 4mg/kg pentamidine plus melarsoprol and prednisolone as in second group). Questionnaires were used to assess the social, economic, cultural and behavioural factors which adversely affect treatment. The honey sample PBMH1 exhibited bactericidal and antitrypanosomal activities in vitro and transient in vivo antitrypanosomal activity. Brassica oleracea aqueous extract exhibited in vitro antitrypanosomal activity.

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INTRODUCTION

Trypanosomes, trypanosomiasis, the vectors and transmission

Trypanosomes belong to the genus Trypanosoma which are motile flagellate protozoan parasites transmitted mainly by the tsetse fly in tropical countries to man and animals. A typical trypanosome is a colourless serpentine spindle shaped organism having more or less rounded posterior and a sharp pointed anterior end (Plates 1 – 6). Trypanosomes cause a disease complex called trypanosomiasis.

Trypanosomiasis consists of a group of important human and animal diseases caused by the parasite protozoa of the genus Trypanosoma (Barrett et al., 2003). These diseases occur in tropical Africa and South America. Depending on the mode of transmission by the insect vector, the genus Trypanosoma (order kinetoplastida) is generally sub-divided into two main groups, the stercoraria (faecal transmission) and the salivaria (salivary transmission).

The stercorarian parasite, Trypanosoma cruzi (Plate 5) causes Chagas’ disease, a major public health problem in South America (Britto et al., 1995; Chimelli & Scaravilli, 1997). Young children are particularly likely to die in the acute febrile stage, whereas adults tend to survive to the chronic stage of the disease, in which parasite damage to the heart muscle and autonomic nervous tissue causes congestive heart failure and dilatation of the oesophagus and colon respectively.

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