Dipetalonema sprenti is a long white roundworm often found in the abdominal cavity and occasionally in the thoracic cavity of beaver.  Addison (1973) found D. sprenti in 15 of 59 beaver collected in various parts of Ontario.

The female worms are 8-12 centimetres long and about three times larger than male worms.  Mature female worms produce minute wriggling embryos called microfilariae.  These microfilariae are carried into the circulatory system where they continue to live.  During summer months mosquitoes ingest microfilariae from infected beaver when sucking blood.  The microfilariae develop in certain species of mosquitoes for two to three weeks and are then ready to infect beaver.  When infected mosquitoes feed again the larval parasites leave the mouth parts of the mosquito and penetrate back into beaver.  They migrate to the abdominal cavity where they mature and mate.  By November or December of the same year, the new females are producing microfilariae and the life cycle is complete.

The parasite is not a serious pathogen of beaver although on occasion, peritonitis and pericarditis have been associated with the presence of D. sprenti.  Evidence suggests that this parasite will develop only in beaver.  It is highly unlikely that there would be an adverse reaction if humans received larvae of D. sprenti when fed upon by infected mosquitoes.  The presence of worms does not affect the edibility of beaver meat.

Selected Reference:

    Addison, E.M. 1973.  Life cycle of Dipetalonema sprenti Anderson (Nematoda:Filarioidea) of beaver (Castor canadensis).  Can.  J. Zool. 51:403-416.