Cystoisospora belli: in vitro multiplication in mammalian cells.

Intracellular development of Cystoisospora belli was demonstrated in 4 different mammalian cell lines. Human ileocecal adenocarcinoma (HCT-8), epithelial carcinoma of lung (A549), Madin-Darby bovine kidney (MDBK), and African green monkey kidney (VERO) were exposed in vitro to C. belli sporozoites, which had been isolated from the feces of HIV-AIDS patients. Parasites invaded all the cellular types between 4 and 12h after exposure and multiplication was demonstrated after 24 h. Grater number of merozoites formed in VERO cells, followed by HCT-8. In the MDBK and HCT-8 cells, the parasitophorous vacuole was less evident and immobile merozoites were observed in the cytoplasm. In VERO cells, one or several parasitophorous vacuoles contained up to 16 mobile sporozoites. No oocysts were found in any of the cell types used. VERO cells may be suitable for studies of the interaction between parasite and host cells.

Immunological comparison of 124 isolates of Toxoplasma gondii.

We tested 124 isolates of Toxoplasma gondii, as determined morphologically and by their ability to elicit antibodies in the dye test with the RH strain of Toxoplasma in mice. They were compared for their capacity to immunize CF-1 mice against isolate T-1, and T-1 immune mice for their capacity to resist each of the 123 other isolates. Of the 125 isolates, 52 had been isolated in the continental USA, 33 in Central America, 15 in Europe, 9 in Hawaii, five in Japan, two in Taiwan, five in Australia, one in Indonesia, one in Tunisia, and one was of unknown origin. Complete cross-immunity was found. This suggests that only one immunotype of Toxoplasma is prevalent in the United States, and perhaps all over the earth. Vaccines are likely to immunize against most or all Toxoplasma isolates.

Determination of the genera of cyst-forming coccidia.

The following heteroxenous and cyst-forming coccidian genera, Besnoitia, Cystoisospora, Frenkelia, Hammondia, Neospora, Sarcocystis and Toxoplasma have been compared biologically, and a key to determine their tissue cysts is provided.

The taxonomic importance of obligate heteroxeny: distinction of Hammondia hammondi from Toxoplasma gondii--another opinion.

We enumerate identical and divergent findings concerning the obligate heteroxenous Hammondia hammondi and the facultatively homoxenous or heteroxenous Toxoplasma gondii. Differences exist in life-cycles, transmission, and host range, especially transmissibility to birds and mammals other than rodents, in ultrastructural morphology, immunity and serology in cats and to lesser degree in rodents, in DNA sequences and in isoenzymes. Because the recognition of obligate heteroxeny is essential to study these organisms and to recognize them as taxa, it is advantageous to give heteroxeny a generic rather than a specific value. Characterization of organisms with the life-cycle patterns of Hammondia, Sarcocystis, Frenkelia, and Toxoplasma is best achieved by means of the genera presently used.

Infection and immunity with the RH strain of Toxoplasma gondii in rats and mice.

Infection and immunity to toxoplasmosis induced by the RH strain of Toxoplasma gondii was compared in Sprague-Dawley (SD) and Wistar rats and in outbred Swiss Webster mice. All rats injected with up to 1,000,000 RH-strain tachyzoites remained clinically normal, whereas mice injected with only 1 live tachyzoite died of acute toxoplasmosis. Rats could be infected with 1 tachyzoite of the RH strain as shown by antibody development and by bioassay in mice. However, after 8 days, RH-strain organisms were recovered only inconsistently from SD and Wistar rat brains. Contrary to a report of sterile immunity to T. gondii infection in rats after immunization with live RH tachyzoites, we found infection immunity after challenge with the VEG strain. Toxoplasma gondii tissue cysts of the VEG strain could be recovered from most SD and Wistar rats, first injected with live RH-strain tachyzoites and then challenged with oocysts of the VEG strain. Our RH strain, and probably many others, passed for 50+ yr as tachyzoites has lost not only the capacity to form oocysts, but also shows a marked reduction or absence of tissue cyst (bradyzoites) formation.

Toxoplasmosis of rats: a review, with considerations of their value as an animal model and their possible role in epidemiology.

We critically review and summarize information on the prevalence of Toxoplasma gondii infections in rats, mainly Rattus norvegicus, and their possible role as a source of infection for larger carnivores and omnivores. We also review information on immunology and natural resistance, contributing to the model value of rats in the analysis of human infection. Rats can be successfully infected with oocysts (sporozoites), tissue cysts (bradyzoites), and tachyzoites. Even adult rats, that are resistant to clinical toxoplasmosis, can be infected orally with a few oocysts or tissue cysts. Infections with tachyzoites of the RH strain are highly variable. Congenital transmission of T. gondii occurs at a high rate when rats are infected during pregnancy. Congenitally infected rats can harbor viable T. gondii in the absence of detectable antibodies to T. gondii and rats with low antibody titers may harbor few or no organisms. The isolation of viable T. gondii by bioassay is the only reliable means to determine persistence of chronic T. gondii infection in feral rats. No evidence was found for maintenance of T. gondii in rats by vertical transmission in the absence of cats.

[Toxoplasmic and chagasic meningoencephalitis in patients with human immunodeficiency virus infection: anatomopathologic and tomographic differential diagnosis]. / Meningoencefalites toxoplásmica e chagásica em pacientes com infecção pelo vírus da imunodeficiência humana: diagnóstico diferencial anatomopatológico e tomográfico.

Twenty-two HIV+ patients with encephalitis were studied. Of these, 7 had meningoencephalitis due to Toxoplasma gondii (MT) and 15 due to Trypanosoma cruzi (MC). Pathologic and computerized axial tomography (CAT) changes were compared. We found that focal necrotizing encephalitis due to Toxoplasma involved the cerebral cortex and the basal ganglia, whereas lesions due to Trypanosoma cruzi were centered in the white matter, sometimes extending into the cortex. Hemorrhages, myelin lesions and organisms were more pronounced in chagasic than in toxoplasmic encephalitis. These findings are consistent with the literature reviewed.

Meningoencefalites toxoplásmica e chagásica em pacientes com infecção pelo vírus da imunodeficiência humana: diagnóstico diferencial anatomopatológico e tomográfico / Toxoplasmic and chagasic meningoencephalitis in patients with human immunodeficiency virus infection: anatomopathologic and tomographic differential diagnosis

Em 22 pacientes com sorologia positiva para o vírus da imunodeficiência humana, com ou sem síndrome da imunodeficiência adquirida, dos quais 7 com meningoencefalite toxoplásmica e 15 com meningoencefalite chagásica associadas, procuraram-se dados diferenciais, entre as duas encefalopatias, tanto à anatomia patológica quanto à tomografia computadorizada do crânio. Os resultados observados e os dados da literatura nos permitiram concluir que enquanto na meningoencefalite necrosante focal por Toxoplasma gondii o acometimento dos núcleos da base é freqüente, na meningoencefalite necrosante focal causada pelo Trypanosoma cruzi, lesões dessas estruturas parecem não ocorrer ou ser excepcionais. De outro lado, o acometimento da substância branca parece nitidamente maior na meningoencefalite chagásica que na meningoencefalite toxoplásmica, ao passo que o parasitismo e a hemorragia do tecido nervoso, bem como as lesões das bainhas de mielina são mais freqüentes e intensos na meningoencefalite causada pelo Trypanosoma cruzi que naquela por Toxoplasma.

Twenty-two HIV+ patients with encephalitis were studied. Of these, 7 had meningoencephalitis due to Toxoplasma gondii (MT) and 15 due to Trypanosoma cruzi (MC). Pathologic and computerized axial tomography (CAT) changes were compared. We found that focal necrotizing encephalitis due to Toxoplasma involved the cerebral cortex and the basal ganglia, whereas lesions due to Trypanosoma cruzi were centered in the white matter, sometimes extending into the cortex. Hemorrhages, myelin lesions and organisms were more pronounced in chagasic than in toxoplasmic encephalitis. These findings are consistent with the literature reviewed.

Genomic drift of Toxoplasma gondii.

We review herein studies concerning the genomic polymorphism of Toxoplasma gondii including 3 clones (1 linked with mouse pathogenicity), 5 zymodemes, and 13 schizodemes. Because mutations occur with some frequency and several allelic configurations are present in isolates grown in the same environment, we conclude that many of the mutations may not be affected by selection pressure. However, the gametocyte-forming ability is under selection pressure from the hose and depends on the development of bradyzoites in tissue cysts. After prolonged multiplication exclusively in the tachyzoite stage in mice and, possibly, in patients the gametocyte-forming ability may be lost. To avoid this genomic change, isolates should be passed in the laboratory, permitting bradyzoite and tissue-cyst formation. Mouse pathogenicity is selected for during mouse passage. We find no major genomic instability justifying species or subspecies distinctions.

The stage-conversion time of Toxoplasma gondii: interpretation of chemical-biologic data out of parasitologic or host context.

Several published biologic times for the stage conversion of Toxoplasma gondii from tachyzoite to bradyzoite in mice are critically examined. There are several reports of 3 days and many of longer times. Possible errors, related to delay from dissemination of the infection, are pointed out. The time to the appearance of the 36-kDa surface antigen, sometimes used for the diagnosis of bradyzoites, should be compared with the biologic attribute of bradyzoites, inducing the short prepatent period in cats. It is recalled that the development of acid pepsin resistance is not exclusively correlated with the biologic definition of bradyzoites. Reactivation of toxoplasmosis in mice does not necessarily follow the administration of a corticosteroid. The daily dose, the type of corticosteroid, its solubility, whether alcohol or ester, the route of administration, the host, and, probably, other factors are important in giving rise to sufficient immunosuppression for reactivation to occur. The plea is made to examine biologic measurements in the context of parasitologic and host factors.

Human Toxoplasma infection in Kuna and Embera children in the Bayano and San Blas, eastern Panama.

We conducted a survey of 760 Amerindian children 2-12 years of age in the Bayano and San Blas areas of Panama in 1991 to determine the prevalence of serum antibodies to Toxoplasma gondii and the importance of hypothesized risk factors in human-induced native and sylvatic conditions, which have had few environmental changes, as opposed to rural and urban areas in Panama previously studied. The overall prevalence of infection ranged between 0% and 42.5%. No age curve was detected, indicative of nonconstant transmission. Only two hypothesized risk factors, floor type and having cats inside the house, were significantly associated with the presence of antibodies in some of the communities. Antibody prevalence appeared to be associated more with the community of residence than with any specific behavior. The risk factor of importance may be the level of oocyst contamination, since infection by tissue cysts in meat was excluded. On three of the nine islands studied, no antibody was detected in the children or the cats. It would appear that T. gondii is not present on these islands. Although the data did not support the importance of many of the hypothesized risk factors, the study is consistent with the theory of transmission by oocysts and the importance of cats in transmission.

Transmission of Toxoplasma gondii in Panama City, Panama: a five-year prospective cohort study of children, cats, rodents, birds, and soil.

A cohort of more than 500 children from Panama City, Panama was studied prospectively over five years for acquisition of antibody to Toxoplasma gondii. The direct agglutination test showed that 72 of 571 children seroconverted between one and six years of age, for a cumulative incidence of 12.6%. Children were examined by pediatricians quarterly, and illnesses that had occurred in the interval and their activities were noted on questionnaires. Thirty-eight variables were examined for their role as risk factors for seroconversion. There was a higher correlation between children's seroconversion and contact with dogs than with cats. Combinations of significant predictors without dogs explained only 67% of the seroconversions, but the same factors with dogs explained 90%. On the other hand, ingestion of raw or rare meat or eggs appeared to play no role in transmission. Cats were examined and 110 (45.6%) of 241 had Toxoplasma antibody on the first bleeding. Only two (0.5%) of 383 cat fecal specimens, when tested in mice, resulted in seroconversion. Ten (1.1%) of 924 soil samples resulted in seroconversion in mice that had been injected. Antibody to Toxoplasma was found in 52 (23.3%) of 226 rats (Rattus norvegicus) and two (0.035%) of 571 mice (Mus musculus). Two hundred sixteen birds of 16 different species were bled. Antibody to Toxoplasma was found in 13.4% of these birds, mostly in grackles, blue-gray tanagers, and doves. The rate of isolation of Toxoplasma was low: one of 23 in rats and three of 201 in birds. High relative risks (RRs) of transmission to children were predicted by contact histories with nursing dogs (RR = 5.8), weaned dogs (RR = 4.7), many flies (RR = 3.6), 6-12-month-old dogs (RR = 3.4), weaned cats (RR = 3.0), 6-12-month-old cats (RR = 2.7), nursing cats (RR = 2.5), much garbage (RR = 2.4), and many roaches (RR = 2.2). The high statistical correlation of dog contact with seroconversion in children suggests the possibility that dogs, by eating and rolling in cat feces, are instrumental in mechanically transmitting Toxoplasma infection. In addition, flies, and to a lesser extent, cockroaches, may have practically important roles in transmission.

A spectrum in the pathology of toxoplasmosis in patients with acquired immunodeficiency syndrome.

We describe a variety of toxoplasmic lesions in seven patients with the acquired immunodeficiency syndrome. The first patient had multiple small-intestinal ulcers associated with Toxoplasma tachyzoites and high antibody titers; he died of disseminated histoplasmosis. The second patient, who died of tuberculosis, also had an inactive chronic Toxoplasma infection, with tissue cysts in the brain that were associated with glial nodules. A third patient died of Toxoplasma encephalitis, manifested by multiple foci of necrosis associated with Toxoplasma tachyzoites, cysts, and hypertrophic arteritis. A fourth patient had been treated for toxoplasmic encephalitis with co-trimoxozol (trimethoprim-sulfamethoxazole combination) for 3 to 4 days and showed degenerating tachyzoites associated with necrotic areas. A fifth patient, treated for toxoplasmic encephalitis with co-trimoxazol for 14 days, had necrotic lesions associated with Toxoplasma antigen and a few cysts. A sixth patient with encephalitis and Toxoplasma tachyzoites and young cysts in the biopsy showed healed brain lesions after 22 days of treatment. A seventh patient, diagnosed radiologically and serologically with Toxoplasma encephalitis, was treated for 7 months; his ring-enhancing lesions subsided, and he died of a central nervous system lymphoma. Toxoplasma could not be isolated from the brain, although toxoplasmic DNA was detected in the brain and heart by polymerase chain reaction. The pathogenesis of the range of these lesions, their diagnosis, and the possibility of terminating Toxoplasma infection by prolonged chemotherapy are discussed.

Prevalence of antibodies to Toxoplasma gondii in wild mammals of Missouri and east central Kansas: biologic and ecologic considerations of transmission.

Sera from 273 wild mammals from Missouri and Kansas (USA), collected between December 1974 and December 1987, were tested for the presence of antibodies to Toxoplasma gondii using the Sabin-Feldman dye test. Sixty-five (24%) had antibodies at titers of > or = 1:8, including 38 (66%) of 58 carnivores, 14 (15%) of 94 omnivores, 13 (11%) of 117 herbivores, and none of four insectivores. The prevalence of antibodies in mice (Mus musculus and Peromyscus spp.) and rats (Rattus norvegicus and Sigmodon hispidus) was low (3%), while medium sized herbivores such as squirrels (Sciurus spp.), rabbits (Sylvilagus floridanus), and muskrats (Ondatra zibethicus) had prevalences of about 18%. Red foxes (Vulpes fulva) and mink (Mustela vison) had the highest prevalence of antibodies with frequencies of 90 and 66%, respectively. In 32 attempts to isolate Toxoplasma gondii from wild mammals with positive (> or = 1:4) titers, only six (19%) were successful: a gray squirrel (Sciurus carolinensis), a beaver (Castor canadensis), an opossum (Didelphis marsupialis), a red fox and two mink. These findings are consistent with the hypothesis that the probability of infection with Toxoplasma gondii, and therefore prevalence of antibodies in wildlife, is greatest in carnivores.

Sarcocystis falcatula of opossums: transmission by cockroaches with fatal pulmonary disease in psittacine birds.

Old World psittacines experienced an acute fatal illness in outdoor breeding collections in South Florida. Toxoplasma-like organisms were found histologically in pulmonary capillaries and elsewhere. Because the organisms underwent schizogony and could not be transmitted to mice, we looked for a cause other than Toxoplasma gondii. An opossum was trapped on the premises of 1 facility and was found to be shedding sporocysts similar to Sarcocystis falcatula in its feces. Cockroaches were prevalent and suspected as transport hosts. Cockroaches that had ingested opossum feces and subsequently were fed to cockatoos induced an identical fatal illness. Obstruction of pulmonary capillaries by developing schizonts and pulmonary edema were the most important pathologic findings. The epidemic was stopped by biological insect control employing flightless chickens to reduce cockroach populations and by an electric fence restricting access of opossums to these outdoor psittacine breeding facilities.