J. Helminthol. Soc. Wash. 61(2), 1994, pp. 162-168 Cestode Infections of Mammary Glands and Female Reproductive Organs: Potential for Vertical Transmission? DAVID BRUCE CONN Department of Biology, The University of the South, Sewanee, Tennessee 37383-1000 ABSTRACT: A widely studied aberrant strain of tetrathyridia of Mesocestoides vogei infecting laboratory mice is the only cestode for which vertical transmission has been verified experimentally. Vertical transmission has been reported for Taenia saginata in cattle and Echinococcus sp. in humans, but the validity of these cases has proved difficult to verify. However, metacestode stages of Taenia solium, Echinococcus granulosus, Echinococcus multilocularis, Multiceps sp., Diphyllobothrium mansoni, Spirometra erinacei, and Proteocephalus ambloplitis have been reported from the mammary glands, uterus, placenta, and/or ovary of several naturally infected hosts. Such infection foci, particularly the mammary glands, suggest a potential for vertical transmission in these species. Such possibilities warrant further study in these and other cestodes. Field surveys of hosts should be conducted to elucidate the prevalence of cestode localization in female organs in which there is potential for transmission. KEY WORDS: Cestoda, Echinococcus, mammary glands, maternal transmission, Mesocestoides, placenta, pre- natal, sparganosis, Taenia, uterus. In recent years, interest in vertical transmis- sion of parasitic organisms has grown substan- tially. This has resulted in the elucidation of sev- eral fascinating examples of transniammary and intrauterine transmission of parasites as re- viewed by Shoop (1991). Increased research ac- tivity over the past 2 decades has revealed that vertical transmission is common among many nematodes and trematodes. Conversely, the lim- ited data available seem to suggest that vertical transmission is not common among cestodes. However, efforts to identify cases of vertical transmission among cestodes have been fewer than those involving nematodes and trematodes. Many cestodes have been reported to localize in female organs, which suggests the potential for vertical transmission. The present review sum- marizes the published cases of vertical trans- mission and invasion of female organs by ces- todes and suggests directions for future research in this area. The Concept of Vertical Transmission In this review, vertical transmission is denned as the transmission of parasites directly (i.e., without any intervening period either outside a host or in a host of another species) from a living parent (usually a mother) to its viable offspring in which parasite reproduction can occur. This may occur in parasites having either monoxe- nous or heteroxenous life cycles and restricts the concept of vertical transmission to those situa- tions involving specific parental/filial relation- ships. Living parent condition By including only living parents, transmission by cannibalism as proposed by Mead and Olsen (1971) for Ophiotaenia filaroides plerocercoids and by Kroeze and Freeman (1982) for Taenia crassiceps cysticerci can be eliminated. As these authors suggested, cannibalism may have im- portant epizootiological implications. However, cannibalism may occur among siblings and fre- quently involves a parent eating its young rather than vice versa. Thus, it is more accurate to re- gard this as a type of paratenesis that happens to involve intra- rather than interspecific ex- change. Reproduction in offspring condition The inclusion in the preceding definition of only parasites having the potential to reproduce within the filial host ensures that the only cases recognized are those in which transmission re- sults in the establishment of a new source of parasite dissemination. This epizootiologically relevant condition excludes those cases in which microfilariae are transmitted transplacentally to unborn young as has been described for several species of filarial nematodes (Eberhard et al., 1993). Transplacental transmission of microfi- lariae obviously involves a specific parental/filial relationship but does not actually result in per- manent establishment of parasites in the young. The only epizootiological significance of this would be the chance that the total number of reservoirs available to insect vectors would be increased temporarily. However, even this may 162 Copyright ' 2011, The Helminthological Society of Washington