“…The phenomenon was first described empirically in certain filariavector models (Pichon, Perrault & Laigret, 1974), which later was generalized mathematically (Prod'hon, Pichon & Riviere, 1980). Since then, non-linearities of transmission, whether facilitation or other, have been reported in other vector-parasite models (Mougey & Bain, 1976;Rosenberg, Koontz & Carter, 1982;Jerwood, Lewis & Saporu, 1984;Cabaret, 1984;Kingsolver, 1987). Facilitation itself is of potential epidemiological interest because it may lead to the establishment of three points of transmission equilibrium with different stability.…”