Prenatal infection with Setaria marshalli (Boulenger 1921) in cattle.

A full year's epidemiological study was conducted in Japan on prenatal infection with Setaria marshalli in cattle. A total of 65 bovine fetuses of abattoir origin, both male and female of 2-9 months of age, were examined postmortem. Results showed that S. marshalli adult worms were detected in the peritoneal cavity of six bovine fetuses of 7-9 months of age during the months of October-December, but not in fetuses of any age during the months of January-September. Infection was not detected in any fetuses under the age of 7 months at any given month of the year. This is the first observation to demonstrate prenatal S. marshalli infection in fetuses. Since S. marshalli has not been detected in cattle older than 2 years, it is speculated that prenatal infection is the common type, while postnatal infection is rather uncommon. Considering fetal age and the seasonal factor, a fetus of age 4-5 months would most frequently develop prenatal infection in the June-August period, when mosquitoes are active as vectors. It is concluded, therefore, that S. marshalli prenatal infection develops during the middle stage of fetal life in summer.