STRONGYLOIDES-STERCORALIS - HISTOPATHOLOGY OF UNCOMPLICATED AND HYPERINFECTIVE STRONGYLOIDIASIS IN THE MONGOLIAN GERBIL, A RODENT MODEL FORHUMAN STRONGYLIODIASIS

Tissues from corticosteroid-treated gerbils hyperinfected with Strongy loides stercoralis were compared grossly and microscopically to simila r tissues from animals with uncomplicated strongyloidiasis. Gerbils wi th hyperinfection developed severe pulmonary alveolar haemorrhage with a variable degree of subacute eosinophilic interstitial pneumonia ass ociated with numerous alveolar, vascular and interstitial larvae. Hype rinfection induced by corticosteroids, given either before inoculation of S. stercoralis larvae or after a chronic Strongyloides infection w as established, produced similar lesions, In contrast, lungs from gerb ils with uncomplicated Strongyloides infection had severe eosinophilic perivasculitis and vasculitis with very little haemorrhage, no pneumo nia and no larvae, Sections of adult worms were present in the proxima l part of the intestinal tract, lodged in spaces between mucosal epith elial cells. Adult worms were not associated with inflammation and wer e more common in the corticosteroid-treated gerbils. In corticosteroid -treated gerbils only, there were numerous larvae in the distal intest inal tract, throughout the intestinal wall and adjacent mesentery, wit hin interstitial tissues and in lymphatic vessels. Significant inflamm ation with associated larvae was only present In the caecum and mesent eric lymph nodes, suggesting that the caecum was the main site for ini tiation of parenteral migration with subsequent invasion of the lympha tic system and lungs. The lesions in these gerbils were similar to tho se found in humans. Infection of gerbils with S. stercoralis is the be st rodent model of human strongyloidiasis.