The cellular responses in Marisa cornaurietis experimentally infected with Angiostrongylus cantonensis

The cellular responses in the poorly susceptible ampullariid snail Marisa cornaurietis to Angiostrongylus cantonensis, during a period of 40 days, involved focal and generalized proliferative reactions. The focal reactions appeared around all larvae as accumulations of variable numbers of amoebocytes at 24 h after infection in the loose connective tissues and somewhat later in the dense tissues. This cellular infiltration intensified gradually with time leading to the encapsulation of the parasite. At 18 days after infection a central zone formed mainly of hypertrophic, granular, highly acidophilic amoebocytes and a peripheral zone of fibrous appearance were conspicuous in most capsules. The generalized proliferative reaction appeared at about day 4 after infection as leucocytosis in the vascular system of the snail and in the connective tissue. At 25 days after infection many leucocytes which are markedly hypertrophic, highly eosinophilic, and densely granulated were found in the vascular system. These cells were spread in the connective tissues and contributed to the formation of the capsules at 40 days after infection. The sources of amoebocytes appear to be mainly several hyperactive areas in the loose connective tissue and in the lung, some active foci in the body wall at the head region, and also in an amoebocyte-producing organ which lies in the roof of the lung.