Asexual Multiplication of Mesocestoides Tetrathyridia in Laboratory Animals

Abstract

Tetrathyridia from the liver and body cavity of the lizard Sceloporus occidentalis biseriatus (Hallowell, 1854), when injected intraperitoneally or fed by stomach tube to white mice, multiplied asexually in the body cavity and liver. Multiplication was by longitudinal binary or multiple fission beginning at the scolex, or by lateral budding posterior to the scolex. Tetrathyridia fed to mice penetrated the small intestine into the body cavity and the liver. No worms were found passing through the bile duct. Tetrathyridia retained their infectivity and reproductive capacity in white mice after having been maintained axenically in vitro for 4.5 months. Multiplication rates in mice were studied by injection of single organisms and examination of mice at weekly or biweekly intervals. Adult Mesocestoides, obtained by feeding mouse livers with tetrathyridia to domestic cats, were identified as Mesocestoides corti Hoeppli, 1925. The presence of tetrathyridia in the body cavity and liver of various reptiles and mammals has been noted by many workers. In California reptiles tetrathyridia have been found by Voge (1953), and by Telford (1964); a histologic description of tetrathyridia was published by Voge and Bemtzen (1963). Unfortunately, the complete life history is not known for any New World species of Mesocestoides. It has been established repeatedly that tetrathyridia, when fed to carnivores, will either develop into the intestinal strobilate phase of Mesocestoides or reach the coelom and remain there as tetrathyridia. Our observation that tetrathyridia from fence lizards survive, as well as multiply asexually, in laboratory mice prompted the studies reported here. The manner and rate of asexual reproduction of tetrathyridia and their infectivity to and maintenance in some laboratory animals was studied. Also reported are preliminary observations on their maintenance in vitro. Specific identification of these tetrathyridia as Mesocestoides corti Hoeppli, 1925 was established as described below. MATERIALS AND METHODS