Migration of Strongyloides venezuelensis in Rats after Oral Inoculation of Free-Living Infective Larvae

Abstract

Strongyloides venezuelensis (SVZ) infection was chronologically monitored in 85 Sprague-Dawley rats (SDR), which were orally inoculated with approximately 1,000 infective larvae. In order to describe the characteristics of migrating larvae (MLS) in various visceral organs (the liver, lung, cardiac blood, and small intestine), 5 SDR were sacrified at 20 min, 45 min, 1 hr, 2 hr, 3 hr, 4 hr, 8 hr, 12 hr, 16 hr, 48 hr, 72 hr, 96 hr, 120 hr, 144 hr, 168 hr and 192 hr post inoculation (PI). MLS were recovered from the liver and blood 20 and 45 min PI and measured 788 ± 26 μm and 846 ± 40 μm in length, respectively. MLS were first observed in the lung tissue 45 min PI and measured 925 ± 38 μm on the average. In the trachea, MLS measuring 849 ± 75 μm appeared 3 to 96 hrs PI. Adult worms (AWS) measuring 1,926 ± 521 μm to 2,956 ± 159 μm in length were observed in the small intestine from 120 hr PI. The worms appeared to mature more than 168 hr PI and attained the average maximum length of 2,420 ± 532 μm. At 3 hr PI focal hyperemic and necrotic lesions were evidently observed in the liver and lung, together with eosinophilic infiltration in the stomach, liver, and lung. The parasites were histologically detectable in the lung tissues but were very difficult to find in the liver and the epithelial layer of small intestine. These data demonstrate that SVZ parasites take 20 min to reach the liver via the stomach and only three hours to reach the trachea through the same route. The development from eggs to adults takes 168 hr in the SDR model.