Unlikely. That would be inconsistent with the heritability, for one thing, for which no genetic correlations with immune-related things have ever been reported that I've seen, and with the best attempts at finding a physical cause landing on things like under-reactive amygdalas and other things one might describe as general brain damage (like toxo) rather than any kind of cunning plan to spread a particular virus/parasite. (How would psychopathy spread a virus? It'd have to be an STD, I guess, except symptoms of psychopathy often show up in childhood and long before individuals have ever had sex, which is also problematic.) Psychopaths do seem fairly fertile, though, which is why theories sometimes invoke an evolutionary life-history explanation: it's a hawk-dove kind of strategy (adaptive if there are enough suckers around, and weak enough social constraints on psychopathic behavior, which would explain why it seems rarer in traditional rural environments and more common in modern urban environments).