How best can we detect the hidden splenic parasite biomass in human Plasmodium infection? Part 1: peripheral blood

In our first cohort of 22 patients undergoing splenectomy in malaria-endemic Timika in Papua, Indonesia, a hidden biomass of non-phagocytosed malaria parasites was found in the spleen at densities up to 3600 times greater than in peripheral blood in P. vivax infection (Pv, n=7) and up to 300 times greater than in peripheral blood in P. falciparum infection (Pf, n=13). These unpublished findings (presented at the 2019 Paris ICPVR7 and GRC conferences) suggest that the spleen is not solely an organ for parasite destruction and clearance, and may be a site for localized asexual life cycles due to the abundance of immature reticulocytes that are targeted for invasion, especially for Pv. Further, in this cohort, all infected individuals were asymptomatic, with spleen-only infections not detectable by peripheral blood microscopy in 12 individuals, 3 of whom were also negative by peripheral blood PCR, and with only 1 individual detectable by conventional RDT.

This indicates that a substantial proportion of the Timika population may have hidden infections in the spleen that are not detectable by normal peripheral blood screening, and likely represent a large malaria transmission reservoir that is not being targeted in current elimination strategies. This project will help to better understand the hidden parasite biomass in the spleen.

Diagnostics

Nov 2019 — Oct 2023

$15,000

Indonesia

Australian Centre for Research Excellence in Malaria Elimination (ACREME)