A neonatal BALB/c mouse model of cryptosporidiosis was used to examine the potential passive transfer of immunity via immune colostrum and oral treatment with anticryptosporidial monoclonal antibodies. Neonates suckled by dams that recovered from Cryptosporidium parvum infections were equally susceptible to infection as their control counterparts suckled by naive dams. Parasite loads among the control and immune colostrum-fed mice were indistinguishable. Neonates receiving orally administered antisporozoite monoclonal antibodies were equally susceptible to infections compared with the control and immune colostrum-fed mice. Parasite loads among the mice receiving daily oral treatment with monoclonal antibody mixtures exhibited significantly lower parasite loads compared with the control mice (P < 0.05). Cryptosporidium parvum is a protozoan (coccidian) parasite that infects the intestinal epithelium of a variety of mammals. Infection is often accompanied by symptoms of gastroenteritis and diarrhea (6). In immunocompetent hosts the disease is self-limiting, and resolution is accompanied by antibody production to various life-cycle stages (2, 3, 15, 26, 28, 29). Immunodeficient humans (those with acquired immune deficiency syndrome and hypogammaglobulinemia) and mice (athymic) may exhibit persistent infections (6, 8, 10, 16, 18). Humoral and cell-mediated immune responses are apparently necessary for recovery from cryptosporidiosis.
The prevalence of Sarcocystis in 930 birds of 58 species from western Canada is reported. All birds were examined for macroscopic cysts, and tissue from 916 birds was also examined histologically for microscopic cysts. Different prevalences were obtained for several species, and nine new host records are reported. Histological examination of muscle revealed Sarcocystis in many birds which would have otherwise been reported uninfected because only microscopic cysts were present. The prevalence of Sarcocystis in some anatids in Alberta was significantly different from two other surveys. Different migratory routes and overwintering g rounds in each of the studies are suggested as explanations for these findings. Several unsuccessful attempts to complete the life cycle using dogs, coyotes, mink, ferrets, cats, kittens, and rats are reported. The failure to establish infection in any of these carnivores with the macroscopic cysts from ducks is considered supporting evidence for the hypothesis that this parasite is transmitted by another host in another area.
Two distinct types of cysts of Sarcocystis from the musculature of moose (Alces alces) were compared by electron microscopy. The fusiform Type A cysts differed from the spherical Type B cysts in the appearance and thickness of the primary cyst wall, organization of cyst interior, and the presence of a secondary cyst wall around Type B. The respective merozoites also differed in size as well as in the number of rhoptries and diameter and arrangement of micronemes. Comparison of the ultrastructure of the moose sarcocysts with those described from other ungulates revealed substantial differences. It appears that two hitherto undescribed species of Sarcocystis are present in moose although cross-transmission and additional life cycle studies are necessary for a complete description.
A light microscope study of the cyst wall of some avian Sarcocystis spp. was undertaken to determine if there were morphological differences in cysts found in different bird species. The cyst wall of macrocysts was different in young and old ducks. Five kinds of microcysts were described from birds, two having smooth outer walls, and three having radial spines on their outer surface. Cysts were differentiated on the basis of the thickness of the outer wall, and on the length and proximity of the radial spines to each other. Specific cyst types were found in several different bird species, and given bird species may harbor more than one cyst type, sometimes concurrently. It is hypothesized that the different cyst types represent different species of Sarcocystis.
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