Seasonal variation in trypanosome parasitological infection rates in small ruminants was studied at the Kaduna Central abattoir, North Central Nigeria. Blood samples were obtained at slaughter from 320 goats and 209 sheep during the dry and rainy seasons and examined using the Haematocrit Centrifugation Technique, Buffy coat method and Giemsa stained blood smears. The packed cell volume of the animals were also obtained. The over all trypanosome infection rate in all small ruminants was 2.10%. Infection rates in sheep and goats were 2.39% and 1.88% respectively. The infection rates were higher in rainy season than the dry season while Trypanosoma vivax was the dominant infecting trypanosome in all the ruminants followed by T.congolense and T. brucei. Infection rates observed here were relatively high and confirmed the resurgence of animal trypanosomosis in the country and its threat to sustainable livestock production.

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Effect of Trypanosoma congolence and T. brucei mixed infection on ability of the bone marrow to respond to anemia was investigated in albino rats. This was with the view of assessing the possible impact on recovery rate from anemia following chemotherapy of African trypanosomosis. The investigation involved descriptive evaluation of packed cell volume and corresponding bone marrow cytological changes associated with single and mixed infection of T. congolense and T. brucei. It involved laboratory based experimental infection of albino rats as research models. A total of 32 adult albino rats of mixed sexes were used for this investigation. The rats were randomly grouped into three groups, A, B, C made up of 8 rats each, and infected with T. congolense, T brucei and mixed infection of these species.. Eight other rats served as the uninfected control group.Parameters measured included weekly packed cell volume (PCV) and differential bone marrow cytology of the different groups of infected and control rats at the end of 21 days post infection (PI). At the end of 21 days PI, the anemia characterized by drop in PCV was most severe in the mixed infection group, and least in T. brucei group with tendency for self-recovery from anemia. The bone marrow responses in the mixed infection group was however weak and inferior to that of T. brucei and T. Congolense groups. Poor erythropoietic response in the mixed infection group despite significant fall (P < 0.05) in PCV level was believed to arise from severe renal and hepatic pathology resulting to subnormal erythropoietin release and severe stem cell injury. This is believed would cause longer time to be taken by mixed infection animals to recover from anemia after chemotherapy. It is concluded that T. congolense and T. brucei mixed infection result to marked incapacitation of the bone marrow and ability for recovery from anemia. This suggests that supportive administration of synthetic erythropoietin may be required in trypanosome specie mixed infection situation due to severe pathological effects on the kidney and liver resulting to impaired erythropoietinbiosynthesis and slow recovery from anemia following chemotherapy in African trypanosomiasis.Keywords: Anemia, bone marrow, mixed infection, rats, trypanosomiasis, erythropoietin. DES REPONSES COMPARATIVES DE LA MOELLE OSSESUSE DE RATS ALBINOS INFECTES EXPERIMENTALEMENT AVEC DES ESPECES UNIQUES ET MIXTES DE

Tsetse fly and trypanosome prevalence in ruminants were estimated in April and August, peak months of the dry and rainy seasons in the Kachia Grazing Reserve (KGR) of Kaduna State, North Central Nigeria. This study was subsequent to reports of seasonal outmigration of semi nomadic Fulani from the grazing reserve due to death of cattle from trypanosomosis. Result of blood samples showed an overall parasitological infection rate of 17.4%. Infection rates in cattle, sheep and goats were, 18.6%, 9.5% and 5.1% respectively. Over all higher infection rate in the rainy season was attributed to abundance of tsetse and other hematophagus flies. Infection rate in younger animals (21.9%) was higher compared to those of older animals (16.5%). Trypanosoma vivax was the dominant infecting trypanosome specie followed by T. congolense and T. brucei.It was concluded that tsetse fly and trypanosomosis constituted dual plagues limiting economic livestock production and settling of the pastoralists in the grazing reserve. This warrants application of sustainable integrated control measures to enhance utilization of abundant fodder at the reserve.