Pathogenicity and host specificity of entomopathogenic nematodes

The mechanisms of infection and pathogenicity of Steinernematidae and Heterorhabditidae in insect hosts are discussed as factors influencing the host specificity of these nematodes. The invasion and evasion of host defences are important steps in the pathogenic process. The ability of the nematode to penetrate into the insect haemocoel, achieved by the release of proteolytic enzymes, is one specific factor. Another specific factor in the nematode-insect relationship is the ability of the nematode to evade defences through failure to be recognized and/or by destruction of insect antibacterial factors. Toxins and extracellular enzymes are important virulence factors released by these nematodes, apparently exhibiting a specific activity against certain insect hosts.