PATHOGENESIS OF HUMAN STRONGYLOIDIASIS - AUTOPSY AND QUANTITATIVE PARASITOLOGICAL ANALYSIS

The distribution of pathologic lesions and the parasite burden of majo r organs were studied in seven patients with disseminated strongyloidi asis who were autopsied at the University of Texas Medical Branch (Gal veston, TX). All patients were immunosuppressed and had additional bac terial, viral, and fungal infections; six patients had received cortis one therapy and one patient had AIDS. High Strongyloides burdens were noted in untreated patients or in those with a short period of treatme nt. The proximal small intestine and the lungs showed the heaviest par asite burden, with large numbers of filariform larvae found in both lo cations. The lungs showed persistence of larvae in all patients, in th e absence of intestinal or extraintestinal infection; this suggests th at the respiratory cycle may be more resistant to therapy than the int estinal cycle. In the intestines, filariform larvae were seen at all l evels, but higher burdens were seen in the upper as compared to lower small intestine, and larvae were more concentrated in the proximal jej unum than in the duodenum. Autoinfection (i.e., filariform larval pene tration) occurred more prominently in the distal small and proximal la rge intestine than in the distal colon. Most filariform larvae were fo und in the intestinal lymphatics and were highly concentrated in mesen teric and retroperitoneal lymph nodes; conversely, larvae were not fou nd in the spleen and were found in very low density in the liver. Thes e findings, in concert, suggest that during autoinfection in humans, t he Stronglyloides larvae traverse lymphatics to the thoracic duct, the n pursue a lymphohematogenous dissemination to the lungs where they pe netrate the air spaces and ascend through the airways to reach the gut .