The highly prevalent parasite Toxoplasma gondii manipulates its host's behavior. In infected rodents, the behavioral changes increase the likelihood that the parasite will be transmitted back to its ...definitive cat host, an essential step in completion of the parasite's life cycle. The mechanism(s) responsible for behavioral changes in the host is unknown but two lines of published evidence suggest that the parasite alters neurotransmitter signal transduction: the disruption of the parasite-induced behavioral changes with medications used to treat psychiatric disease (specifically dopamine antagonists) and identification of a tyrosine hydroxylase encoded in the parasite genome. In this study, infection of mammalian dopaminergic cells with T. gondii enhanced the levels of K+-induced release of dopamine several-fold, with a direct correlation between the number of infected cells and the quantity of dopamine released. Immunostaining brain sections of infected mice with dopamine antibody showed intense staining of encysted parasites. Based on these analyses, T. gondii orchestrates a significant increase in dopamine metabolism in neural cells. Tyrosine hydroxylase, the rate-limiting enzyme for dopamine synthesis, was also found in intracellular tissue cysts in brain tissue with antibodies specific for the parasite-encoded tyrosine hydroxylase. These observations provide a mechanism for parasite-induced behavioral changes. The observed effects on dopamine metabolism could also be relevant in interpreting reports of psychobehavioral changes in toxoplasmosis-infected humans.
This paper reviews clinical and asymptomatic
Toxoplasma gondii infection in humans and other animals in the USA. Seroprevalence of
T. gondii in humans and pigs is declining. Modes of transmission, ...epidemiology and environmental contamination with oocysts on land and sea are discussed.
Neospora caninum is a protozoan parasite of animals. Until 1988, it was misdiagnosed as Toxoplasma gondii. Since its first recognition in 1984 in dogs and the description of a new genus and species ...Neospora caninum in 1988, neosporosis has emerged as a serious disease of cattle and dogs worldwide. Abortions and neonatal mortality are a major problem in livestock operations and neosporosis is a major cause of abortion in cattle. This review is focused on current status of neosporosis in animals based on papers published in the last five years. Worldwide seroprevalences are tabulated. Strategies for control and prevention are discussed.
Sheep are important to the economy of many countries because they are a source of food for humans Sheep are commonly infected with the protozoan parasite, Toxoplasma gondii. Infection with the ...parasite may cause early embryonic death and resorption, fetal death and mummification, abortion, stillbirth, and neonatal death. Severity of infection is associated with the stage of pregnancy at which the ewe becomes infected, the earlier in gestation, the more severe the consequences. Infected sheep meat is a source of T. gondii infection for humans and carnivorous animals. Most sheep acquire T. gondii infection after birth, and less than 4% of persistently infected sheep transmit the parasite vertically to the next generation. Recent studies by a group of researchers in England reported that repeat ovine transmission of T. gondii may be more common than previously believed but these findings are soley based on PCR data and require additional data using other techniques to verify the findings. Following infection with T. gondii, sheep develop humoral and cell-mediated immune responses against the parasite that provides effective protection against disease in subsequent pregnancies. A commercial vaccine is available, comprising a live, incomplete strain of T. gondii. The vaccine is administered to sheep prior to mating to protect against lamb losses due to toxoplasmosis. In the present paper, information on the prevalence, transmission, and control of ovine toxoplasmosis in the last 20 years is reviewed.
Many eukaryotic microbes have complex life cycles that include both sexual and asexual phases with strict species specificity. Whereas the asexual cycle of the protistan parasite Toxoplasma gondii ...can occur in any warm-blooded mammal, the sexual cycle is restricted to the feline intestine. The molecular determinants that identify cats as the definitive host for T. gondii are unknown. Here, we defined the mechanism of species specificity for T. gondii sexual development and break the species barrier to allow the sexual cycle to occur in mice. We determined that T. gondii sexual development occurs when cultured feline intestinal epithelial cells are supplemented with linoleic acid. Felines are the only mammals that lack delta-6-desaturase activity in their intestines, which is required for linoleic acid metabolism, resulting in systemic excess of linoleic acid. We found that inhibition of murine delta-6-desaturase and supplementation of their diet with linoleic acid allowed T. gondii sexual development in mice. This mechanism of species specificity is the first defined for a parasite sexual cycle. This work highlights how host diet and metabolism shape coevolution with microbes. The key to unlocking the species boundaries for other eukaryotic microbes may also rely on the lipid composition of their environments as we see increasing evidence for the importance of host lipid metabolism during parasitic lifecycles. Pregnant women are advised against handling cat litter, as maternal infection with T. gondii can be transmitted to the fetus with potentially lethal outcomes. Knowing the molecular components that create a conducive environment for T. gondii sexual reproduction will allow for development of therapeutics that prevent shedding of T. gondii parasites. Finally, given the current reliance on companion animals to study T. gondii sexual development, this work will allow the T. gondii field to use of alternative models in future studies.
It has been 100 years since the discovery of
Toxoplasma gondii in 1908. Its full life cycle was not discovered until 1970 when it was found that it is a coccidian parasite of cats with all non-feline ...warm blooded animals (including humans) as intermediate hosts. The discovery of the environmentally resistant stage of the parasite, the oocyst, made it possible to explain its worldwide prevalence. In the present paper, events associated with the discovery of its life cycle are recalled.
Neospora caninum is a protozoan parasite of animals. Until 1988, it was misidentified as Toxoplasma gondii. Since its first recognition in dogs in 1984 and the description of the new genus and ...species Neospora caninum in 1988, neosporosis has emerged as a serious disease of cattle and dogs worldwide. Abortions and neonatal mortality are a major problem in livestock operations, and neosporosis is a major cause of abortion in cattle. Although antibodies to N. caninum have been reported, the parasite has not been detected in human tissues. Thus, the zoonotic potential is uncertain. This review is focused mainly on the epidemiology and control of neosporosis in cattle, but worldwide seroprevalences of N. caninum in animals and humans are tabulated. The role of wildlife in the life cycle of N. caninum and strategies for the control of neosporosis in cattle are discussed.
Pigs are important to the economy of many countries because they are a source of food for humans. Infected pig meat is a source of
Toxoplasma gondii infection for humans and animals in many ...countries. This parasite also causes mortality in pigs, especially neonatal pigs. Most pigs acquire
T. gondii infection postnatally by ingestion of oocysts from contaminated environment or ingestion of infected tissues of animals. Few pigs become infected prenatally by transplacental transmission of the parasite. Raising pigs indoors in confinement has greatly reduced
T. gondii infection in pigs but the recent trend of organic farming is likely to increase
T. gondii infection in pigs. Recently, feeding goat whey to pigs was found to be a risk factor for
T. gondii infection in organically raised pigs. Currently used molecular and histopathological methods are insensitive for the detection of
T. gondii in pork because of the low concentration of the parasite in meat destined for human consumption. There is no vaccine to prevent
T. gondii infection in pigs but efforts are being continued to develop a non-viable vaccine. In the present paper, information on prevalence, transmission, diagnosis, and control of porcine toxoplasmosis in the last 20 years (since 1988 when last reviewed by this author) is reviewed. Worldwide reports of clinical and asymptomatic infections in pigs are reviewed. Methods to detect
T. gondii in pigs are compared. Recent studies on genetic typing of
T. gondii strains prevalent in pigs are discussed with respect to epidemiology. Because wild pigs are hunted for food for human consumption prevalence in wild pigs is summarized.
Foodborne Toxoplasmosis Jones, Jeffrey L.; Dubey, J. P.
Clinical infectious diseases,
09/2012, Letnik:
55, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Toxoplasmosis can be due to congenital infection or acquired infection after birth and is one of the leading illnesses associated with foodborne hospitalizations and deaths. Undercooked meat, ...especially pork, lamb, and wild game meat, and soil contaminated with cat feces on raw fruits and vegetables are the major sources of foodborne transmission for humans. The new trend in the production of free-range organically raised meat could increase the risk of Toxoplasma gondii contamination of meat. Foodborne transmission can be prevented by production practices that reduce T. gondii in meat, adequate cooking of meat, washing of raw fruits and vegetables, prevention of cross contamination in the kitchen, and measures that decrease spread of viable oocysts into the environment.
Camelids (llamas, alpacas, vicuñas, guanacos) are important for the economy of South America and
Eimeria
infections are important as cause of mortality in camelids. Of the five most prevalent species ...of
Eimeria
in South American camelids,
Eimeria macusaniensis
,
Eimeria lamae
,
Eimeria alpacae
,
Eimeria punoensis
, and
Eimeria ivitaensis, E. macusaniensis
is considered the most pathogenic. There is considerable confusion concerning the endogenous developmental stages of
Eimeria
spp. in camelids. Many papers on camelid coccidiosis were published in local Peruvian journals, not easily accessible to wider audience. The objective of the present paper is to summarize information on history, validity of
Eimeria
species, life cycle, pathogenicity, prevalence, epidemiology, diagnosis, and control of coccidiosis in camelids.
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