A STUDY OF VIRULENCE PARAMETERS FOR TOXOPLASMA-GONDII INFECTIONS IN MICE

With the aim of establishing assessments of the virulence of Toxoplasm a gondii isolates for mice, we investigated weight loss, serum levels of haptoglobin, and serum levels of tumor necrosis factor-alpha (TNF-a lpha) as alternative parameters to mouse mortality. Groups of BALB/c m ice were inoculated i.p. with increasing parasite doses (5 x 10(1), 10 (4), and 10(6)) of isolate 119 and with a low dose (5 x 10(1)) of isol ates GT1 and NED. The inoculation dose was inversely correlated with t he interval to the onset of weight loss (starting at days 9, 7, and 5, respectively) and the onset of increase in serum haptoglobin (startin g at about days 8, 6, and 4, respectively). The GT1 strain (inducing 1 00% mortality at day 9) also gave the fastest response in terms of wei ght loss (onset by day 8) and increase in serum haptoglobin (onset by day 6), which occurred 1-2 days before these parameters were affected in the other low-dose groups. The low-dose NED and 119 inoculations we re distinguished by continued weight loss, which lasted until day 20 i n the former group (max: average weight loss 2.9 g as compared with 0. 4 g).