Studies on the parasitaemia, plasma volumes, leucocyte and bone marrow cell counts, and the moribund state in Trypanosoma brucei infection of splenectomised and intact mice

Toxicity study and anti-trypanosomal activities of aqueous and methanol whole plant extracts of Brillantaisia owariensis on Trypanosoma brucei-induced infection in BALB/c mice

Background

The problem of drug resistance and toxicity in trypanosomiasis is ever-increasing, thereby creating a need to search for efficacious and safer alternatives that are of plant origin. We designed the present study to assess the oral acute toxicity, and anti-trypanosomal activity of Brillantaisia owariensis in mice.

Methods

Fifty-eight BALB/c mice were used for this study. For toxicity assessment, eighteen mice were divided into two groups of nine mice each, and acute single oral administration of the aqueous and methanol whole plant extracts of B. owariensis was assessed for each group as per Lorke’s method. Mice were observed for signs of toxicity of liver and kidney organs after two weeks of oral administration. For the anti-trypanosomal activity, forty mice were divided into eight groups of five mice. Mouse in each group was inoculated with 0.1 mL containing106T. brucei /mL. Following patency of 3 days, mice were treated at different dosages of methanol and aqueous extracts. Pre-infection, post-infection, and post-treatment data for rectal temperature, body weight, parasiteamia level, packed cell volume, and daily survival were monitored.

Results

The acute oral toxicity studies (LD50) for methanol and aqueous plant extracts in this study were calculated as 3535 mg/kg/body weight, and are non-toxic. No obvious histopathologic observation in the liver and kidney tissues. The mean daily rectal temperature and mean weights of all the treated mice were restored to normal values and significant (P, 0.05) in comparison to the positive control.

Parasitaemia clearance by both extracts was suppressive. The mean PCV values were significantly increased following treatment, and there was prolonged survival especially in mice treated with methanol extracts.

Conclusion

The study concludes that the extracts of B. owariensis are relatively non-toxic with a good safety margin when administered to mice orally. Crude methanol extract exhibited better suppressive and haematinic antitrypanosomal activities than the aqueous extract, and it has a promising effect by its ability to reduce anaemia in mice challenged with T. brucei brucei, and prolonged survival.

A Light and Electron Microscopic Study of Changes in Blood and Bone Marrow in Acute Hemorrhagic Trypanosoma vivax Infection in Calves

Eleven 6-month-old calves were tsetse fly challenged with a stock of Trypanosoma vivax (IL 2337) that causes hemorrhagic infection. The calves were randomly euthanatized every 4 to 6 days; two other calves served as controls. Peripheral blood changes included anemia, thrombocytopenia, and an initial leukopenia. Later in the course of infection, leukocytosis associated with lymphocytosis and neutropenia developed. Moderate reticulocytosis (highest mean count 3.6 ± 3.7%, maximum count 9.4%) accompanied the first wave of parasitemia, but poor response (highest mean 0.4 ± 0.0%) occurred during the second wave, despite the persistence of severe anemia. Light microscopic examination of bone marrow samples showed a drop in the myeloid: erythroid ratio with a decrease in granulocytes, particularly metamyelocytes, bands, and segmenters. Increase in lymphocyte counts corresponded with the appearance of lymphoid nodules within the marrow. Megakaryocyte volume increased significantly in infected animals, and some megakaryocytes showed emperipolesis of red cells, neutrophils, and lymphocytes. Transmission electron microscopic examination of the bone marrow revealed that trypanosomes had crossed the sinusoidal endothelium into the hematopoietic compartment as early as the second day of parasitemia. Macrophages proliferated in the bone marrow; and from the second day of parasitemia until the end of the experimental infection, on day 46, the macrophages had phagocytosed normoblasts, eosinophil and neutrophil myelocytes, metamyelocytes, bands, and segmenters, as well as reticulocytes, erythrocytes, and thrombocytes. Therefore, dyserythropoiesis and dysgranulocytopoiesis were responsible, in part, for the observed anemia and granulocytopenia, respectively.

Experimental Trypanosoma evansi infection in the goat. II. Pathology

Infection of male goats aged 8-10 months with 5000 or 50 000 organisms of a Mindanao strain of Trypanosoma evansi was observed over a period of 90 days. The infection induced clinical disease which was lethal, especially at the higher dose rate. Lesions were more acute in goats that received the higher dose. Gross and microscopical changes were not pathognomonic, except in the presence of demonstrable trypanosomes. At necropsy, a combination of lymphadenopathy, splenomegaly, hepatomegaly, testicular enlargement, anaemic signs and consolidation of the anterior lobes of the lungs was suggestive of surra. Testicular changes, especially aspermia, indicated probable infertility. The cytopathology of the lungs, liver, intestine, kidneys, testes, bone marrow, brain and other organs was immunological in nature, characterized by mononuclear infiltration of interstitial tissues, with minor cellular damage and the presence of trypanosomes. B- and T- cell responses were observed in the lymphatic system, but the findings indicated immunosuppression in the lymph nodes, spleen and bone marrow during the third month after infection. Exudative inflammatory changes were mild. It is suggested that the cytopathology of most haemophilic trypanosomal infections is predominantly an immunological process.

The effect of trypanocidal drug treatment on the haematological changes in Trypanosoma brucei brucei infected splenectomised dogs

Twenty adult mongrel dogs of both sexes were used. Ten of the dogs were splenectomised and the remaining dogs were left intact. Five dogs each from the splenectomised and non-splenectomised (intact) animals were infected intravenously with Trypanosoma brucei brucei while the rest served as uninfected controls. All the infected dogs developed trypanosomosis between Days 4 and 8 postinfection. The packed cell volume, haemoglobin concentration, total red blood cell count and white blood cell count decreased progressively indicating anaemia and leucopenia. The absolute reticulocyte counts were increased. Splenectomy enhanced fever, reticulocytosis and parasitaemia but delayed the onset of anaemia and leucopenia. It also shortened the prepatent period of the infection. The treatment of the infected dogs with diminazene aceturate (Berenil at the dose rate of 7.0 mg kg-1 body weight on Day 21 postinfection cleared the parasites in blood within 24 h and resulted in complete reversal of all the haematological aberrations observed. Splenectomy did not enhance or inhibit the recovery rate in the animals after treatment.

Pathogenesis of Trypanosoma brucei infection in deer mice (Peromyscus maniculatus). V. Macrophage ultrastructure and function

Macrophage numbers increased in the spleen, liver, testes, heart, and kidney of deer mice infected for seven to ten weeks with Trypanosoma brucei EATRO 110. The macrophages were activated as indicated by their increased size and significant increases in numbers of cell organelles including profiles of rough endoplasmic reticulum (which also increased in length), mitochondria, primary and secondary lysosomes, bundles of Golgi's apparatus, and free lysosomes compared to macrophages from control mice. Some macrophages representing epithelioid cells have even greater numbers of organelles than the activated macrophages and had interdigitation in some locations, such as the heart, but with minimal phagocytic activity. These epithelioid cells were present in the kidney, testes, and particularly in the heart of infected mice. Few cardiac macrophages had finely granular deposits on their nuclear membrane. The activated macrophages had enhanced phagocytosis of trypanosomes, red blood cells, neutrophils, eosinophils, lymphocytes, and plasma cells. In addition to phagocytosis, another probable consequence of macrophage activation may be depression of lymphocyte function. Phagocytosis of trypanosomes by neutrophils also was encountered occasionally.