In this study the antiplasmodial effect of ethanol extract of eucalyptus citriodora leaves on haematological parameters of Plasmodium bergei-infected mice was investigated. The aim was to determine; the effect of Plasmodium on haematological parameters using Swiss mice, to determine the effect of ethanolic leaf extract of E. citriodora on the haematological parameters of mice infected with P. Bergei and In vivo evaluation of anti-plasmodial activity of ethanolic leaf extract of E. Citriodora on Swiss mice infected with P. bergei. Peters4-day suppressive test was used for animal grouping for infection and treatment. Standard procedures were employed in the acute toxicity test and anti-plasmodia activity test. The experimental animals were acclimatized for 7 days before the commencement of treatment. The mice were treated for 4 consecutive days with the following doses 200mg/kg, 400mg/kg and 600mg/kg of leaf extracts and a standard malarial drug (Chloroquine as positive control) at a dose of 5mg/kg body weight. The body weight and packed cell volume were determined before inoculation and treatment and after inoculation and treatment. The haematological parameters were also analyzed. The leaf
extract did not reveal any toxicity. The leaf extract revealed suppression of plasmodia activity in the significant(P<0.05) increase in body weight of infected groups and prevention of drastic decrease in PCV in infected and extract treated groups compared to untreated group. There was a significant (P<0.05) decrease in the PCV,RBC, Hb and platelet of untreated group compared to the treated groups and significant increase in WBC of untreated group compared to the treated groups. The study revealed that Eucalyptus citriodora leaf extract could be a future antiplasmodia herbal candidate for the treatment of malaria.