Clinical and physiological responses in sporozoite-induced B strain Plasmodium cynomolgi and Plasmodium vivax infections in normal volunteers

Abstract
Five inmate volunteers were experimentally infected by sporozoite inoculation with the B strain of P. cynomolgi. The course of their infection was contrasted with that of two volunteers infected with the Venezuelan strain of P. vivax. The group of patients infected with the B strain of P. cynomolgi demonstrated a prepatent period of 9–15 days, an incubation period of 10–17 days, with the duration of their febrile illness lasting 8–12 days. The maximum parasite density in this group was 1100 parasites/c.mm. The patients infected with P. vivax demonstrated a prepatent period of 14 days, with an incubation period of 15 days. The duration of their febrile illness was 19 days, with the maximum parasite density controlled to 16,770/c.mm. Both groups of patients exhibited tertian fever patterns, but with the fever rising higher and lasting longer in the P. vivax infected patients. Headache, abdominal pain, and hepatosplenomegaly were prominent in the B strain P. cynomolgi infections. Generalized malaise, anorexia, weight loss, and shaking chills were pronounced in the P. vivax infected volunteers. Significant laboratory findings in both groups of patients were anaemia, leucopenia, thrombocytopenia, an elevated erythrocyte sedimentation rate, and shortened survival time of labelled red blood cells. The group infected with P. vivax demonstrated a moderately severe anaemia with a depressed reticulocyte response in comparison to the group infected with the B strain of P. cynomolgi. Other positive findings were hypoalbuminaemia and hyperglobulinaemia in both infections and a fall in the excretion of 17-hydroxycorticosteroid excretion in three of the five volunteers infected with the B strain of P. cynomolgi.
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