Toxoplasma gondii: from animals to humans.

Institut für Parasitologie, Tierärztliche Hochschule Hannover, Bünteweg 17, D-30559, Hannover, Germany.
International Journal for Parasitology (Impact Factor: 3.4). 11/2000; 30(12-13):1217-58. DOI: 10.1016/S0020-7519(00)00124-7
Source: PubMed

ABSTRACT Toxoplasmosis is one of the more common parasitic zoonoses world-wide. Its causative agent, Toxoplasma gondii, is a facultatively heteroxenous, polyxenous protozoon that has developed several potential routes of transmission within and between different host species. If first contracted during pregnancy, T. gondii may be transmitted vertically by tachyzoites that are passed to the foetus via the placenta. Horizontal transmission of T. gondii may involve three life-cycle stages, i.e. ingesting infectious oocysts from the environment or ingesting tissue cysts or tachyzoites which are contained in meat or primary offal (viscera) of many different animals. Transmission may also occur via tachyzoites contained in blood products, tissue transplants, or unpasteurised milk. However, it is not known which of these routes is more important epidemiologically. In the past, the consumption of raw or undercooked meat, in particular of pigs and sheep, has been regarded as a major route of transmission to humans. However, recent studies showed that the prevalence of T. gondii in meat-producing animals decreased considerably over the past 20 years in areas with intensive farm management. For example, in several countries of the European Union prevalences of T. gondii in fattening pigs are now <1%. Considering these data it is unlikely that pork is still a major source of infection for humans in these countries. However, it is likely that the major routes of transmission are different in human populations with differences in culture and eating habits. In the Americas, recent outbreaks of acute toxoplasmosis in humans have been associated with oocyst contamination of the environment. Therefore, future epidemiological studies on T. gondii infections should consider the role of oocysts as potential sources of infection for humans, and methods to monitor these are currently being developed. This review presents recent epidemiological data on T. gondii, hypotheses on the major routes of transmission to humans in different populations, and preventive measures that may reduce the risk of contracting a primary infection during pregnancy.

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    ABSTRACT: Summary: This study aimed to investigate serum total sialic acid (TSA) and ceruloplasmin (CP) levels and their possible correlation in Toxoplasma gondii seropositive dogs. The study was conducted on the dogs that had been kept in doghouses located in the province of Istanbul. Based upon indirect fluorescence antibody test (IFAT) results, 15 T. gondii seronegative dogs and 25 seropositive infected dogs were included in the study. Blood samples were collected from each dog and serums were obtained. Subsequently, TSA and CP concentrations were measured. For serum TSA concentration, no significant difference was found between control (17.20±0.55 mg/dl) and infected dogs (15.97±0.55 mg/dl) (p>0.05). On the other hand, serum CP concentration was significantly higher in seropositive dogs (16.49±1.11 mg/dl) compared to control dogs (10.28 ±1.63 mg/dl) (p<0.01). No correlation was found between serum TSA and serum CP. Absence of a significant difference between groups for serum TSA might be related to the fact that the disease was in chronic stage, and the severity of cellular damage might have been decreased. Elevation of serum CP in T. gondii infected dogs is most likely related to cellular damage as a consequence of infection. We suggest that serum CP can be used as an additional prognostic parameter in toxoplasmosis in support to other serologic parameters.
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    ABSTRACT: Background: Toxoplasma gondii is a ubiquitous protozoan parasite capable of infecting all warm-blooded animals including livestock. In these animals, the parasite forms cysts in the tissues which may pose a risk to public health if infected meat is consumed undercooked or raw. The aim of this study was to determine the exposure of livestock to T. gondii in St. Kitts and Nevis. Methods: Sera and/or heart tissue and meat juice were collected from pigs (n = 124), sheep (n = 116) and goats (n = 66) at the St. Kitts Abattoir. Sera and meat juice were screened for reactive antibodies to T. gondii using an in-house ELISA. Heart tissue was screened for T. gondii DNA using quantitative PCR and positive samples were genotyped using RFLP. Results: Antibodies to T. gondii were detected in sera from 48% of pigs, 26% of sheep and 34% of goats tested. Antibodies were also detected in the meat juice from 55% of pig hearts, 22% of sheep hearts and 31% of goat hearts tested. There was a significant positive correlation between serology and meat juice results. T. gondii DNA was detected in heart tissue of 21% of pigs, 16% of sheep and 23% of goats tested. Preliminary PCR-RFLP analysis identified a predominance of the Type III genotype of T. gondii. Conclusions: These results suggest widespread environmental contamination with T. gondii oocysts and that livestock could be a potentially important source of T. gondii infection if their infected meat is consumed (or handled) undercooked.
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    ABSTRACT: Infectious protozoan parasites are transmitted to humans through several routes, including contaminated food and water, inadequately treated sewage/sewage products, and livestock and domestic pet handling. Several enteric protozoa cause severe morbidity and mortality in both humans and animals worldwide. In developed settings, enteric protozoa are often ignored as a cause of diarrheal illness due to better hygiene conditions, and as such, very little effort is used toward laboratory diagnosis. Although these protozoa contribute to the high burden of infectious diseases, estimates of their true prevalence are sometimes affected by the lack of sensitive diagnostic techniques to detect them in clinical and environmental specimens. Despite recent advances in the epidemiology, molecular biology, and treatment of protozoan illnesses, gaps in knowledge still exist, requiring further research. There is evidence that climate-related changes will contribute to their burden due to displacement of ecosystems and human and animal populations, increases in atmospheric temperature, flooding and other environmental conditions suitable for transmission, and the need for the reuse of alternative water sources to meet growing population needs. This review discusses the common enteric protozoa from a public health perspective, highlighting their epidemiology, modes of transmission, prevention and control and epidemiological pictures in Ethiopia. It also discusses the potential impact of climate changes on their epidemiology and the issues surrounding waterborne transmission and suggests a multidisciplinary approach to their prevention and control.


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