 Infection is more common and has a higher microfilarial dose with age, though studies have found microfilarial dose not to be correlated with symptoms.In parts of rural South America, men have been found more susceptible than women, possibly due to more outdoors work by males as children, and possibly due to cooking fires serving as deterrents to vectors for women who perform more domestic duties.One study in central Africa found "M. perstans" to be a much more common cause of filariasis symptoms compared to Loa loa and Wuchereria bancrofti.