STRONGYLOIDES-STERCORALIS - AN INITIAL AUTOINFECTIVE BURST AMPLIFIES PRIMARY INFECTION

Compartmental analysis of Strongyloides stercoralis burdens in experim entally infected, serially necropsied dogs was used to test an autoinf ective burst hypothesis. The hypothesis states that in well-establishe d, active infections and in chronic infections as well, the rate of la rval development is down-regulated so that most larvae do not attain i nfectivity internally. The majority pass in the feces as preinfective, rhabditiform larvae, but a few (those with the most rapid development al rate) attain infectivity internally, and therefore are positioned f or autoinfectivity. In contrast, in immunologically naive hosts, larva l development proceeds without host hindrance and many larvae, proceed ing at the most rapid rate of a spectrum of normal intrinsic developme ntal rates, attain infectivity internally. For a brief period, hyperin fection occurs, during which the adult worm population increases sharp ly. Gut-level resistance soon occurs, larval development is retarded, and an increasing proportion of larvae are discharged as preinfective rhabditiform larvae. With fewer larvae developing to infectivity inter nally, recruitment into the adult population decreases, with an attend ant increase in the mean age and a gradual decrease in the size of the adult population. The data and the attendant model strongly support t his autoinfective burst hypothesis.