The life cycle of Toxocara vitulorum in Asian buffalo (Bubalus bubalis).

A procedure for labelling hatched Toxocara vitulorum larvae with 75 selenium is described. Labelled larvae are infective when administered into the small intestine and portal vein of buffalo of all ages. Only very young calves are infected after oral administration. The labelled larvae are used with an enhanced fluorographic autoradiographic procedure to study the dynamics of the infection in non-pregnant and pregnant buffalo. Larvae penetrate the wall of the small intestine between 2 and 8 h after administration. Most larvae go straight to the liver via the portal vein but a few enter the mesenteric lymph nodes. Over the next 90 h some larvae migrate to the lung and a few to muscle, brain, kidney and peripheral lymph nodes. Most remain in the liver. Over the next 3-7 weeks the larvae grow by about 10% and no moulting is observed. In a pregnant host larvae grow to 500-600 microns in liver and lung 1-8 days before parturition and migrate to the mammary gland around the time of parturition. In the mammary gland they grow to about 1200 microns and pass into the milk during the 7 days after parturition.