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1.
Toxoplasma gondii, a zoonotic protozoal parasite, is well-known for its global distribution and its ability to infect virtually all warm-blooded vertebrates. Nonetheless, attempts to describe the population structure of T. gondii have been primarily limited to samples isolated from humans and domesticated animals. More recent studies, however, have made efforts to characterize T. gondii isolates from a wider range of host species and geographic locales. These findings have dramatically changed our perception of the extent of genetic diversity in T. gondii and the relative roles of sexual recombination and clonal propagation in the parasite's lifecycle. In particular, identification of novel, disease-causing T. gondii strains in wildlife has raised concerns from both a conservation and public health perspective as to whether distinct domestic and sylvatic parasite gene pools exist. If so, overlap of these cycles may represent regions of high probability of disease emergence. Here, we attempt to answer these key questions by reviewing recent studies of T. gondii infections in wildlife, highlighting those which have advanced our understanding of the genetic diversity and population biology of this important zoonotic pathogen.  相似文献   

2.
The issue of whether market fish can be involved in the transmission of Toxoplasma gondii in the marine environment is highly debated since toxoplasmosis has been diagnosed frequently in cetaceans stranded along the Mediterranean coastlines in recent times. To support the hypothesis that fishes can harbour and effectively transmit the parasite to top‐of‐the‐food‐chain marine organisms and to human consumers of fishery products, a total of 1,293 fishes from 17 species obtained from wholesale and local fish markets were examined for T. gondii DNA. Real‐time PCR was performed in samples obtained by separately pooling intestines, gills and skin/muscles collected from each fish species. Thirty‐two out of 147 pooled samples from 12 different fish species were found contaminated with T. gondii DNA that was detected in 16 samples of skin/muscle and in 11 samples of both intestine and gills. Quantitative analysis of amplified DNA performed by both real‐time PCR and digital PCR (dPCR) confirmed that positive fish samples were contaminated with Toxoplasma genomic DNA to an extent of 6.10 × 10?2 to 2.77 × 104 copies/ml (quantitative PCR) and of 1 to 5.7 × 104 copies/ml (dPCR). Fishes are not considered competent biological hosts for T. gondii; nonetheless, they can be contaminated with T. gondii oocysts flowing via freshwater run‐offs (untreated sewage discharges, soil flooding) into the marine environment, thus acting as mechanical carriers. Although the detection of viable and infective T. gondii oocysts was not the objective of this investigation, the results here reported suggest that fish species sold for human consumption can be accidentally involved in the transmission route of the parasite in the marine environment and that the risk of foodborne transmission of toxoplasmosis to fish consumers should be further investigated.  相似文献   

3.
Toxoplasma gondii is an obligate intracellular parasite with a variety of hosts, responsible for reproductive problems and economic losses in sheep flocks. Neospora caninum was recently identified and its clinical presentation in sheep is similar to that of toxoplasmosis, which can cause repeated abortions, though less frequently in this species. In order to confirm the prevalence of these agents in the city of Mossoró, Rio Grande do Norte, Brazil, 409 serum samples from adult sheep (364 females and 45 males) were tested by the indirect immunofluorescence antibody test, using cut-off point at a dilution of 1:64 and 1:50 for T. gondii and N. caninum, respectively. From the 35 properties examined, 23 (65.7%) had at least one seropositive animal for T. gondii and six (17.1%) for N. caninum. The prevalence of seropositive animals for T. gondii was 20.7% and for N. caninum 1.8%. There was no association between the presence of the agent’s antibody and gender, reports of reproductive problems and presence of dogs and/or cats in the properties. T. gondii is well distributed and N. caninum has low prevalence in sheep and in the properties of the studied region.  相似文献   

4.
Toxoplasma gondii was discovered by scientists working in North Africa and Brazil around 100 years ago. The parasite has since been found to be capable of infecting all warm‐blooded animals including humans making it one of the most successful parasitic organisms worldwide. The pathogenic potential of T. gondii was recognized in the 1920s and 1930s, in congenitally infected children presenting with the classic triad of symptoms, namely hydrocephalus, retinochoroiditis and encephalitis. In addition, around the same time T. gondii parasites were found to be associated with severe intraocular inflammation. In the 1980s, T. gondii emerged as a major cause of death in patients with acquired immunodeficiency syndrome, illustrating the importance of the immune system in controlling T. gondii infection. T. gondii was reported as a major cause of abortion in sheep in New Zealand in the 1950s, which raised questions about potential new transmission routes for the parasite. The discovery of the cat as the definitive host in the 1960s was a very important finding as it helped to complete our understanding of the parasite’s life cycle, and the oocyst stage of T. gondii shed in the faeces of infected cats was found to be an important source of infection for many intermediate hosts and helped to explain infection in herbivorous animals and people with a vegetarian diet. In addition, this stage of the parasite was very robust and could survive in the environment, depending on the climatic conditions, for up to 12–18 months. Knowledge of the parasite’s lifecycle, transmission routes, risk groups and host immune responses has helped in the development of strategies to control the disease, reduce transmission of the parasite and limit environmental contamination.  相似文献   

5.
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6.
Toxoplasma gondii is a globally distributed parasitic protozoan that infects humans and other warm‐blooded vertebrates. Felids are the only definitive host for T. gondii, and they excrete oocysts in their faeces. The national prevalence in humans is declining in the United States. This zoonotic organism is of particular interest due to its importance in pregnant women, in individuals with altered immune systems, and in reactivated ocular infections. Exposure to the parasite in humans is usually associated with consumption of raw or undercooked meat or by accidental ingestion of oocysts. It was hypothesized that veterinary students would have a greater chance at exposure to the parasite than an average population of undergraduate students due to increased contact with cats who are infected. A commercially available ELISA was used to examine serum samples from 336 students (252 veterinary students and 84 undergraduate students) at Virginia Polytechnic Institute and State University and the Virginia‐Maryland Regional College of Veterinary Medicine for serum IgG antibodies to T. gondii antigen. The prevalence of T. gondii in these subjects was 5.6% in veterinary school students (n = 252) and 2.4% in undergraduates (n = 84). There was no significant difference (P > 0.05) in the prevalence of T. gondii antibodies in veterinary versus undergraduate students. The overall prevalence of 4.8% in all students in this study reflects the continuing decline of antibodies to T. gondii in humans in the United States.  相似文献   

7.
Chagas disease (Trypanosoma cruzi infection) is one of the most important neglected tropical diseases affecting the Americas. The transmission dynamic of this parasite is a complicated process that involves three genera of Triatominae subfamily and over 100 known mammalian reservoirs composed of domestic, peridomestic and wildlife species. Understanding the complex relationship between vector species and mammalian hosts is important for preventing transmission to humans. We performed a historical literature review to assess the disease burden in the Texas wildlife and domestic animal population. Reports of sylvatic transmission in Texas date back to the 1940s. We found that up to 23 species can serve as reservoirs for T. cruzi in the state with wood rats, raccoons, and wild and domestic canine species most frequently reported as positive for the parasite. We finish with a discussion of the current research gaps, implications for high‐risk populations and future directions for research.  相似文献   

8.
Neospora caninum infections in chickens have been recently described by epidemiological and experimental approaches, and these birds may be considered natural intermediate hosts of the parasite. It has been postulated that other bird species might perform this role in wildlife as well. To better understand the sylvatic life cycle of N. caninum, further studies are required. In that sense, this work aimed to observe infection kinetics in pigeons experimentally infected with N. caninum. Experimental infections were conducted in parallel with a related protozoan, Toxoplasma gondii, which has been already described as able to infect pigeons in nature. Our results demonstrated that N. caninum disseminated through various tissues of this host and induced parasite-specific IgG seroconversion. Infection parameters were similar to that observed in the T. gondii infected group, although N. caninum-infected pigeons presented lower IgG titers during acute phase. The results herein described demonstrate that pigeons are a suitable model for N. caninum infection, considering that these data are in agreement with those observed in chickens experimentally infected with this parasite. As pigeons may be revealed as important reservoirs for N. caninum infection in nature, future studies are necessary to determine the real prevalence of this parasite in this and other birds in wildlife.  相似文献   

9.
Two swine production units and their contiguous wildlife populations were used for this study. These herds were located 7 miles apart in the major swine producing area of south central Georgia. Herd A had a Toxoplasma gondii antibody prevalence of 27.6% in all ages of swine sampled, with an increased incidence of 13.6% over a 5-month period. This herd was maintained under a semi-range condition. The swine in Herd B were maintained exclusively in concrete floored, enclosed buildings. This herd had a 0.85% T. gondii prevalence. Rodents and a few other wildlife and domestic species were trapped in or around both herds. These animals were examined for Toxoplasma antibodies using the same test procedure utilized for swine sera, the indirect immunofluorescent (IIF) test. Additionally, rodent tissues were homogenized and suspensions prepared for interperitoneal (I/P) inoculation into CF1 laboratory mice.Rodents and wildlife species examined were: Mus musculus, Peromyscus leucopus, Rattus norvegicus, Sigmodon hispidus, Procyon lotor, and Didelphis marsupalis. Feral and domestic animals other than swine that also were tested for the presence of T. gondii antibodies included two cats, two horses, and a dog. The overall prevalence of T. gondii antibodies in all non-porcine species examined was 67% for those animals in and around the premises of Herd A, and 63% for those in and around Herd B.Toxoplasma infectivity of rodents whose tissues were processed and inoculated into laboratory mice correlated well with the results of the IIF test on the serum of these wild rodents. No tachyzoites of T. gondii were found in the peritoneal exudate of laboratory mice post I/P inoculation with wild rodent tissue, with one exception.While there was no significant difference in Toxoplasma infectivity in non-porcine species on these two premises, management practices appeared to be the determining factor in swine infection with T. gondii. Excluding wildlife precluded infection.  相似文献   

10.
Acquisition of Toxoplasma gondii infections is mainly through ingestion of parasite-contaminated food. T. gondii oocyst distribution in the living environment of human and livestock is directly linked to the prevalence of the parasite infection in humans and domestic animals. In this study, we investigated the sero-prevalence of T. gondii infection in free-range as well as caged chicken in northeast China. The purpose of this study was to investigate the potential prevalence of T. gondii oocysts in the environments. Sera of 308 free-range chickens and 210 caged chickens collected in three areas in northeast China were tested for anti-T. gondii antibodies with ELISA assays. The infection rates of free-range and caged chickens were 34.7% and 2.8% respectively, indicating that the parasite is widely distributed in the environment and poses threatens to the health of people living in those areas.  相似文献   

11.
In the present study, the antibodies to Toxoplasma gondii in 191 farm‐bred and 83 house‐bred geese (Anser domestica) were assessed for the prevalence of T. gondii infection in southern China with the modified agglutination test. Antibodies to T. gondii (MAT ≥ 1 : 5) were found in 27 (14.14%) of farm‐bred geese and 14 (16.87%) of house‐bred geese. Geese infected with T. gondii may be a source of T. gondii infection for humans and cats.  相似文献   

12.
Chickens are considered one of the most important hosts in the epidemiology of Toxoplasma gondii infection because they are an efficient source of infection for cats that excrete the environmentally resistant oocysts and because humans may become infected with this parasite after eating undercooked infected chicken meat. The objective of this study is to review worldwide prevalence of T. gondii infection in chickens and to assess the role of infected chickens in the epidemiology of toxoplasmosis in humans. A very high prevalence of the parasite was found in chickens raised in backyards (up to 100%) and free‐range organic (30–50%) establishments.  相似文献   

13.
Urbanization of natural areas can change abiotic factors, providing artificial sources of humidity in summer and decreasing variation of temperatures in winter. Our study aimed at document risk factors of infection in mammal reservoirs of pathogenic Leptospira in the human/wildlife interface of a large metropolitan area. We hypothesize that survival of Leptospira and thus their prevalence in animal reservoirs should be higher in residential areas than in natural habitats, especially after the hot, dry Mediterranean summers. We established the prevalence of Leptospira spp. and identified the serovars in 353 urine samples from micromammals (chiefly the wood mouse Apodemus sylvaticus, n = 266) using direct immunofluorescence and PCR. Animals were captured in spring and autumn, 2011–2012, in two natural parks and two adjacent residential areas in periurban Barcelona (NE Spain). Overall observed prevalence of infection was 11%, ranking between 8% and 13% in the better represented host species. We observed marked differences between seasons; the probability of finding a micromammal infected in spring was three times greater than in autumn (almost four times for wood mouse). Prevalence was not related with type of habitat, micromammal relative abundance or sex of the animal. Three Leptospira species were confirmed: Leptospira interrogans (47% of cases), Leptospira borgpetersenii (41%) and Leptospira kirschneri (12%). The serovars most commonly detected were those typically hosted by rodents, and serovars Ballum and Icterohemorrhagiae were the only ones found in autumn. People living in periurban Barcelona and those visiting the natural areas of the metropolitan area face hazard of infection with rodent‐borne Leptospira, especially during spring.  相似文献   

14.
Background

Toxoplasma gondii is a common protozoan parasite among all mammals, in particular small ruminants, worldwide. Traditional husbandry can be a major risk factor for infection of sheep and goats with this parasite.

Objectives

The present study aimed to determine the current status of the prevalence for T. gondii in livestock of Qazvin Province.

Methods

In this cross-sectional study, the sera of 455 sheep and 375 goats were examined to detect anti-Toxoplasma IgG antibodies by using in-house indirect ELISA.

Results

Overall, 33.62% (153/455) of sheep and 36.41% (130/375) of goats were positive for anti-Toxoplasma IgG antibodies with no statistically significant difference. The prevalence rate of T. gondii among the sheep of Qazvin County was significantly higher than in Abyek and Abhar counties (p < 0.001).

Conclusions

The results of the present study indicate that the prevalence of T. gondii in sheep and goats of the study area is high. Therefore, the meat of the animals reared in this area can be a potential source of human infections by this parasite.

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15.
Toxoplasma gondii is among the most studied parasites worldwide but there is not much information about it published in Ireland. The objectives of this study were to determine the seroprevalence of T. gondii in sheep, pigs, deer and chickens and the molecular detection of T. gondii DNA in muscle tissue. Serum samples were collected from these species at the time of slaughter at Irish abattoirs during 2007 and tested for anti‐T. gondii antibodies using a commercial semi‐quantitative latex agglutination test. Antibodies (titre ≥1 : 64) were found in 36% (105/292) sheep, 4.7% (15/317) pigs and 6.6% (23/348) deer. In chickens, 18% (65/364) had antibody titres, ranging between 1 : 5 and 1 : 1024. Significant (P ≤ 0.05) age‐related differences in seroprevalence were found in adult sheep (58.1%) and pigs (23.1%). Significant gender differences in seroprevalence was also found in sheep with more females (43%) than males (22.4%) being positive. However, when adjusted for age through logistic regression gender was no longer significant. Seroprevalence was also evaluated on farm locations grouped to NUTS level 3, but the prevalence was too low to draw any statistical conclusions. Using a nested PCR, the presence of T. gondii DNA was detected in diaphragm samples from 3.6% (3/83) sheep, 13.0% (3/23) pig and 4.2% (3/71) deer. Meat digestion liquids from a Trichinella spp. survey in pigs were also used for the first time to detect T. gondii. Toxoplasma gondii DNA was detected in 50% (10/20) of pooled samples. This is the first in depth study of T. gondii seroprevalence in animals in Ireland and a novel method, using digestion liquid from pooled diaphragm samples, for PCR detection in pigs is described.  相似文献   

16.
Toxoplasma gondii is an intracellular coccidian parasite found worldwide and is known to infect virtually all warm-blooded animals. It requires a cat (family Felidae) to complete its full life cycle. Despite the absence of wild felids on the Arctic archipelago of Svalbard, T. gondii has been found in resident predators such as the arctic fox and polar bear. It has therefore been suggested that T. gondii may enter this ecosystem via migratory birds. The objective of this study was to identify locations where goose populations may become infected with T. gondii, and to investigate the dynamics of T. gondii specific antibodies. Single blood samples of both adults and juveniles were collected from selected goose species (Anser anser, A. brachyrhynchus, Branta canadensis, B. leucopsis) at Arctic brood-rearing areas in Russia and on Svalbard, and temperate wintering grounds in the Netherlands and Denmark (migratory populations) as well as temperate brood-rearing grounds (the Netherlands, non-migratory populations). A modified agglutination test was used on serum, for detection of antibodies against T. gondii. Occasional repeated annual sampling of individual adults was performed to determine the antibody dynamics. Adults were found seropositive at all locations (Arctic and temperate, brood-rearing and wintering grounds) with low seroprevalence in brood-rearing birds on temperate grounds. As no juvenile geese were found seropositive at any brood-rearing location, but nine month old geese were found seropositive during spring migration we conclude that geese, irrespective of species and migration, encounter T. gondii infection in wintering areas. In re-sampled birds on Svalbard significant seroreversion was observed, with 42% of seropositive adults showing no detectable antibodies after 12 months, while the proportion of seroconversion was only 3%. Modelled variation of seroprevalence with field data on antibody longevity and parasite transmission suggests seroprevalence of a population within a range of 5.2–19.9%, in line with measured values. The high occurrence of seroreversion compared to the low occurrence of seroconversion hampers analysis of species- or site-specific patterns, but explains the absence of an increase in seroprevalence with age and the observed variation in antibody titre. These findings imply that even though infection rate is low, adults introduce T. gondii to the high Arctic ecosystem following infection in temperate regions.  相似文献   

17.
Serum samples from 408 sheep from different regions of Chile and 447 alpacas (Llama pacos) from the north of the country were tested for Toxoplasma gondii antibodies. The indirect haemagglutination test (IHAT) was used in both species and the indirect immunofluorescence test (IIFT) was also used on the sheep samples in order to compare the performance of the tests in that species. In both tests, titers ≥1:16 were considered diagnostically significant. Sera from 49 sheep (12%) were positive to T. gondii antibodies by the IHAT. When using the IIFT, 114 sheep sera (28%) were positive. The different results obtained in sheep sera between the tests were significant (p<0.0001). No differences were observed between geographical locations or sex of the sampled sheep regarding serological detection of T. gondii antibodies in sheep. As expected, adult sheep showed higher T. gondii reactivity than young sheep (p=0.0008). The corrected prevalence of toxoplasmosis in alpaca was 16.3% (32 positive out of 447). The rather low prevalence in alpacas may be associated with their extensive management as well as the extreme climatic conditions of The Andes which apparently would not be favorable for the transmission of the parasite.  相似文献   

18.
Practising veterinary medicine has an inherent risk of exposure to zoonotic agents, including the protozoan parasite Toxoplasma gondii. We screened sera of veterinarians authorized to work in Finland for the presence of specific immunoglobulin G antibodies against T. gondii with an enzyme‐linked fluorescent assay, and evaluated potential risk factors for T. gondii seropositivity from extensive questionnaire data with almost 1,300 quantitative variables. We used a causal diagram approach to address the complexity of the life cycle of the parasite and its numerous possible transmission routes, and built a multivariable binomial logistic regression model to identify risk factors that are particularly relevant for veterinarians. The samples and questionnaire data were collected in 2009. Altogether, 294 veterinarians, almost 15% of the Finnish veterinary profession, were included in the study. The median age was 39 years, and the majority, 86%, were women. Altogether, 43 (14.6%; 95% confidence interval: 10.9–19.0) of the 294 veterinarians tested seropositive for T. gondii. According to the final model, veterinarians who were at least 40 years old had 2.4 times higher odds to be seropositive than younger veterinarians; veterinarians who lived in the countryside had 4.0 times higher odds to be seropositive than veterinarians who lived in towns; female veterinarians who tasted beef during cooking had 2.6 times higher odds to be seropositive than male veterinarians who did not taste beef during cooking; and veterinarians who did not do small animal practice had 2.3 times higher odds to be seropositive than those who did. The results illustrate the numerous transmission routes of T. gondii.  相似文献   

19.
Toxoplasma gondii is a widely distributed zoonotic protozoan parasite, which can affect most warm-blooded species. Some species of non-human primates (NHPs) are highly susceptible to T. gondii infection. The aim of the study was to determine the seroprevalence and risk factors associated with T. gondii infection in NHPs housed in zoos in Spain. Sera from 189 NHPs belonging to 33 species were collected in eight zoos. Additionally, 10 of the 189 animals were longitudinally sampled. Anti-T. gondii antibodies were detected in 48 NHPs (25.4%; confidence interval of 95% (CI95%): 19.2–31.6) using a modified agglutination test (MAT; cut-off = 25). Seropositive animals had titers of 25 (6.3%), 50 (8.3%), 100 (8.3%) and ≥500 (68.8%). Seropositivity was detected in 15 of the 33 species (45.5%). Of the 10 NHPs sampled more than once, two animals (one Barbary macaque [Macaca sylvanus] and one common chimpanzee [Pan toglodytes]) seroconverted along the study period, while one seropositive chimpanzee increased antibody titers over time. The Hominidae family (OR = 5.9; CI95%: 2.7–12.8) and sex (females) (OR = 2.1; CI95%: 1.1–4.1) were risk factors potentially associated with seropositivity to T. gondii. Our results evince a widespread circulation of T. gondii in NHPs in zoos in Spain, which may be of conservation concern. Control measures should be implemented to minimize the risk of exposure of these species to T. gondii.  相似文献   

20.
Toxoplasma gondii, a ubiquitous parasitic protozoan, is emerging as an aquatic biological pollutant. Infections can result from drinking water contaminated with environmentally resistant oocysts. However, recommendations regarding water treatment for oocyst inactivation have not been established. In this study, the physical method of radiofrequency (RF) power was evaluated for its ability to inactivate T. gondii oocysts in water. Oocysts were exposed to various RF energy levels to induce 50, 55, 60, 70 and 80°C temperatures maintained for 1 min. Post‐treatment oocyst viability was determined by mouse bioassay with serology, immunohistochemistry and in vitro parasite isolation to confirm T. gondii infections in mice. None of the mice inoculated with oocysts treated with RF‐induced temperatures of ≥60°C in an initial experiment became infected; however, there was incomplete oocyst activation in subsequent experiments conducted under similar conditions. These results indicate that T. gondii oocysts may not always be inactivated when exposed to a minimum of 60°C for 1 min. The impact of factors such as water heating time, cooling time and the volume of water treated must be considered when evaluating the efficacy of RF power for oocyst inactivation.  相似文献   

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