New and old risk-factors for Toxoplasma gondii infection: prospective cross-sectional study among military personnel in the Czech Republic

The aims of this study were to evaluate seroprevalence and the importance of various risk-factors for Toxoplasma infection in the Czech Republic. A prospective cross-sectional survey was conducted among military personnel in Prague. Consenting subjects (n = 3250) completed a questionnaire concerning demographics and risk-factors, and blood samples were taken to determine anti-Toxoplasma antibody titres according to complement fixation and ELISA IgG and IgM tests. The seroprevalence of toxoplasmosis was 23%. In multivariate analysis, independent predictors of Toxoplasma seropositivity were age (OR 1.03 / year), consumption of raw meat (OR 1.35), owning a cat (OR 1.25), owning rabbits (OR 1.47), childhood residence in a town with a population of <10 000 inhabitants (OR 1.63) vs. location of the childhood residence in a town with population of >100 000 inhabitants, and blood group type A (OR 1.28), B (OR 1.33) or AB (OR 1.43) vs. O. These results suggested that horizontal toxoplasmosis transmission in the Czech Republic may occur through consumption of raw meat, contact with cat faeces and farming.

Recent transcontinental sweep of Toxoplasma gondii driven by a single monomorphic chromosome

Toxoplasma gondii is a highly prevalent protozoan parasite that infects a wide range of animals and threatens human health by contaminating food and water. A markedly limited number of clonal parasite lineages have been recognized as predominating in North American and European populations, whereas strains from South America are comparatively diverse. Here, we show that strains from North America and Europe share distinct genetic polymorphisms that are mutually exclusive from polymorphisms in strains from the south. A striking exception to this geographic segregation is a monomorphic version of one chromosome (Chr1a) that characterizes virtually all northern and many southern isolates. Using a combination of molecular phylogenetic and phenotypic analyses, we conclude that northern and southern parasite populations diverged from a common ancestor in isolation over a period of approximately 10(6) yr, and that the monomorphic Chr1a has swept each population within the past 10,000 years. Like its definitive feline hosts, T. gondii may have entered South America and diversified there after reestablishment of the Panamanian land bridge. Since then, recombination has been an infrequent but important force in generating new T. gondii genotypes. Genes unique to a monomorphic version of a single parasite chromosome may have facilitated a recent population sweep of a limited number of highly successful T. gondii lineages.

Toxoplasma gondii in an African crested porcupine (Hystrix cristata)

An adult female crested porcupine (Hystrix cristata) was evaluated for acute onset of neurologic signs including head tilt, circling, and ataxia. She was found dead in her holding area 2 days after initially exhibiting clinical signs. Necropsy was unremarkable. Histopathology of brain tissue revealed the presence of protozoal cysts associated with inflammation as the underlying cause of clinical signs and death. Immunohistochemical staining of brain tissue for Toxoplasma gondii was strongly positive. PCR on fresh brain confirmed T. gondii as the causative organism. An adult male in the same enclosure has demonstrated similar neurologic signs over the past 3 years and has failed to respond to various medical treatments. Clinical disease associated with T. gondii has not been previously reported in this porcupine species or any other Old World porcupines, although there are several reports of clinical toxoplasmosis involving New World porcupine species.

Toxoplasma gondii infection in horses. A review

This review updates those written by Dubey and Beattie in 1988 (1988a) and by Tenter et al in 2000, on pathological and epidemiological aspects of Toxoplasma infection in horses. Under natural conditions, seroprevalence may variate from 0% up to 90%. This wide variation may be due to the sensitivity of the serological methods, to the age of animals, to the geographical area, and even to the hygienic condition of the farms and farm management. With few exceptions, horses are considered one of the less sensitive specie to the pathogenic effect of Toxoplasma gondii. In fact, neither under experimental nor under natural condition a genuine pathologic picture related to the toxoplasmic infection has been described. In one occasion the organism has been isolated from an eye condition and in others a connection between a higher frequency of unspecified pathological conditions and a positive response to serological test for Toxoplasma has been speculated. Diaplacental transmission and the following abortion have been only occasionally reported, and at least in one case in a quite trustworthy way, therefore it must be considered possible, though rare. Although infection of humans due to the consumption of horse meat has never been reported, the existence of a possible risk arouses by the demonstration of the presence of parasite stages in either naturally or experimentally infected horses, which resulted to be infective for mice and/or cats.

Maternal–fetal transmission of Toxoplasma gondii in interferon-γ deficient pregnant mice

Toxoplasma gondii infection is generally asymptomatic in immunocompetent persons but can be life-threatening in immunocompromised persons and for fetuses in the case of maternal-fetal transmission. The effect of interferon (IFN)-gamma, which plays a crucial role in the protective immunity against T. gondii infection, on maternal-fetal transmission of T. gondii was analyzed by quantitative competitive polymerase chain reaction targeting T. gondii-specific SAG1 gene. T. gondii loads were obvious in uterus and placenta of wild type (WT) C57BL/6 (B6, susceptible strain) but not BALB/c (resistant strain) pregnant mice. Higher levels of T. gondii were detected in uterus and placenta of IFN-gamma knock-out (GKO) B6 and BALB/c than in those of WT mice. Furthermore, T. gondii was detected in fetus of GKO B6 but not GKO BALB/c, WT B6, or WT BALB/c mice. Thus, not only IFN-gamma but also genetic susceptibility to T. gondii infection was important for the protective immunity of maternal-fetal transmission of T. gondii to fetus via placenta. T. gondii-infected WT mice displayed a low delivery rate with high IFN-gamma production, whereas infected GKO mice did not. Additionally, mean body weight of neonates from T. gondii-infected GKO BALB/c pregnant mice was significantly lower than that of unaborted neonates from WT BALB/c pregnant mice, suggesting the effects of T. gondii infection on intrauterine growth retardation of fetus in pregnant GKO mice.

Comparison of a Commercial ELISA with the Modified Agglutination Test for the Detection of Toxoplasma gondii Infection in Naturally Exposed Sheep

Surprisingly few commercial ELISAs are available for the detection of Toxoplasma gondii infection in animals, and none for use in sheep have been evaluated. We thus compared the Bommeli Diagnostics ELISA Toxotest for the detection of T. gondii antibodies in ruminants with the reference modified agglutination test (MAT) in a series of 180 sheep sera. ELISA results were analysed at two cut-off levels (30%, comprising both weakly positive and positive results, and 100%, comprising only positive results), and compared with MAT at three cut-off levels (titre of 1 : 25, 1 : 50 and 1 : 100). The results showed a moderate agreement of ELISA at both cut-offs (kappa = 0.46 and 0.51) with MAT at a cut-off titre of 1 : 100. However, the specificity and positive predictive value were above 95% only at an ELISA cut-off of 100%, indicating its potential as a diagnostic test, particularly in areas with a high prevalence of infection. On the other hand, lower sensitivity and negative predictive value limit its value as a screening test. Thus, the ELISA Toxotest may be used for quick diagnosis of T. gondii infection in sheep in the field, i.e. for the differential diagnosis of ovine abortion storms.

Genetic characterization of Toxoplasma gondii isolates in dogs from Vietnam suggests their South American origin

Dogs are considered a potential risk for transmission of Toxoplasma gondii to humans because they can mechanically transmit oocysts to people and in certain parts of the world dog meat is consumed by humans. The prevalence of T. gondii in 42 dogs from rural Vietnam was determined. Antibodies to T. gondii were assayed by the modified agglutination test, and found in 21 (50%) of 42 dogs with titers of 1:20 in six, 1:40 in seven, 1:80 in two, 1:160 in two, 1:320 in two, 1:640 in one, and 1:1280 or higher in one. Hearts, tongues and brains of 21 seropositive dogs were bioassayed in cats, mice or both. Tissues from eight seropositive dogs were fed to eight T. gondii-free cats. Feces of cats were examined for oocysts. T. gondii was isolated from eight dogs by bioassay in cats. Genotyping of these eight T. gondii isolates using polymorphisms at 10 nuclear markers including SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and a new SAG2, and an apicoplast marker Apico revealed two genotypes. Both genotypes were previously identified from the dog isolates in Colombia, suggesting their South America origin. However, they are different from the predominant Type I, II and III lineages that are widely spread in North America and Europe. This is the first report of isolation of viable T. gondii from any host in Vietnam.

The role of feral mammals on wildlife infectious disease prevalence in two nature reserves within Mexico City limits

Wild and feral medium-sized mammals were live trapped at two natural protected areas within the Mexico City limits to determine antibody prevalence for the most common infectious diseases (rabies, toxoplasmosis, and canine parvovirus) in dogs and cats. Mammals were trapped during the dry (March-April) and rainy seasons (July-August) of 1996 and 1997. A total of 68 individuals were captured, representing 8 species: opossums (Didelphis virginiana), ringtails (Bassariscus astutus), spotted skunks (Spilogale gracilis), weasels (Mustela frenata), rock squirrels (Spermophilus variegatus), Mexican gray squirrels (Sciurus aureogaster), feral cats (Felis catus), and feral dogs (Canis familiaris). There was marked seroprevalence for parvovirus (86.6%) and lower seroprevalences for both toxoplasma (23.9%) and rabies (17.9%). There were no significant prevalence differences among mammals in both protected areas, which were of contrasting size and isolation (i.e., small and isolated versus large and nonisolated). We suggest that high seroprevalence of these three infectious agents in wild mammals is a result of the high densities of feral dogs and cats in the two areas sampled. Feral dogs are able to maintain the infectious agents in these localities regardless of the protected area size and isolation. However, the native mammals of the small and isolated reserve are more vulnerable to infectious diseases because of small population size and genetic bottlenecks. Our results indicate that natural areas in and around Mexico City are a refugium for latent infectious agents, several of which are zoonotic. These findings suggest that conservation measures, such as eradication of feral mammals and vaccination programs, in the protected areas and surrounding areas could be beneficial.

Toxoplasma gondii strains defective in oral transmission are also defective in developmental stage differentiation

Toxoplasma gondii undergoes differentiation from rapidly growing tachyzoites to slowly growing bradyzoites during its life cycle in the intermediate host, and conversion can be induced in vitro by stress. Representative strains of the three clonal lineages showed equal capacity to differentiate into bradyzoites in vitro, as evidenced by induction of bradyzoite antigen 1, staining with Dolichos biflorus lectin (DBL), pepsin resistance, and oral infectivity in mice. We also examined several recently described exotic strains of T. gondii, which are genetically diverse and have a different ancestry from the clonal lineages. The exotic strain COUG was essentially like the clonal lineages and showed a high capacity to induce bradyzoites in vitro and in vivo, consistent with its ability to be efficiently transmitted by the oral route. In contrast, exotic strains MAS and FOU, which are defective in oral transmission, showed a decreased potential to develop into bradyzoites in vitro. This defect was evident from reduced staining with DBL and the cyst antigen CST1, failure to down-regulate tachyzoite antigens, such as tachyzoite surface antigens 1 and 2A, and decreased resistance to pepsin treatment. Despite normal in vitro differentiation, the exotic strains CAST and GPHT also showed decreased oral transmission, due to formation of smaller cysts and a lower tissue burden during chronic infection, traits also shared by MAS and FOU. Collectively, these findings reveal that the limited oral transmission in some strains of T. gondii is due to inefficient differentiation to the bradyzoite form, leading to defects in the formation of tissue cysts.

Cats and goat whey associated with Toxoplasma gondii infection in pigs

In organic livestock production systems, farm-management factors are thought to play an important role in the on-farm prevalence of Toxoplasma gondii. Serological results and the results of an HACCP analysis were combined to determine important risk factors for the prevalence of this protozoan parasite. Mathematical analysis demonstrated that feeding goat whey to pigs and the presence of a high number of cats were positively correlated to T. gondii seroprevalence in pigs. Not covering roughage and the farmers' assumption that pigs can come into contact with cat feces also showed a positive relationship. In order to decrease the risk of T. gondii infecting their pigs, farmers should limit the access and number of cats on their farms and refrain from feeding goat whey to their pigs.

Prevalence of Neospora caninum and Toxoplasma gondii in sheep and dogs from Guarapuava farms, Paraná State, Brazil

Sheep and dog blood samples were collected from nine farms in the county of Guarapuava, Paraná, Brazil. The indirect fluorescent antibody test (IFAT) was used to detect Neospora caninum and Toxoplasma gondii antibodies. Herein, serum samples from 305 sheep were evaluated, being 29 (9.5%) and 157 (51.5%) seropositives to N. caninum and T. gondii, respectively. Seven (29.1%) and five (20.8%) out of 24 dogs were seropositives to N. caninum and T. gondii, respectively. There were no differences among the sheep serology for N. caninum and reproductive problems, management and animal feeding variables, neurological problems and presence of other animals species on the farm (P>or=0.05). The simultaneous frequency of antibodies between N. caninum and T. gondii was 5.2% in the herds. Age, breed, farm size, semi-intensive activity, mineral salt supplementation, water origin, stage of the pregnancy when reproduction problems occurred, neurological problems in lambs, presence of rodents in the food room and pasture cat access were identified as associated factors for the occurrence of toxoplasmosis in sheep (P<0.05). There were no differences among the seropositivity in dogs for N. caninum and T. gondii and breed, age and sex (P>or=0.05). The present work is the first report on serum prevalence of N. caninum in sheep from the state of Paraná, Brazil.

Seroprevalence of Toxoplasma gondii in wild boars (Sus scrofa) in the Slovak Republic

Toxoplasma gondii is a protozoan parasite of great medical and veterinary importance. The aim of this study was to determine the seroprevalence of toxoplasmosis in wild boars hunted in the Slovak Republic in 2003. Examination of 320 wild boars revealed a seroprevalence of 8.1%. The majority of seropositive wild boars came from the north-western and southern regions of Slovakia. This study indicates that T. gondii infection is common in wild boars in the Slovak Republic, underlines its zoonotic potential and the importance of high standards of hygiene during the handling of game.

Susceptibility to vertical transmission of Toxoplasma gondii is temporally dependent on the preconceptional infection in Calomys callosus

Toxoplasma gondii is an obligate intracellular parasite that causes a variety of clinical syndromes, but the infection is more severe in immunocompromised individuals and in cases of congenital toxoplasmosis. This study aimed to verify if the susceptibility to vertical transmission of Toxoplasma gondii is temporally dependent on the preconceptional infection in Calomys callosus. Twelve C. callosus females were infected with 20 cysts of T. gondii ME49 strain and divided into three groups of four animals that were mated after approximately 10 days (group 1), 30 days (group 2), and 50 days (group 3) of infection. The animals were sacrificed from the 17th to 20th day of pregnancy, when placentas and embryos were collected for morphological and immunohistochemical studies, mouse bioassay for evaluating seroconversion and PCR for detecting parasite DNA. Serum samples from C. callosus females and mice used in bioassay were analysed for the detection of IgG antibodies to T. gondii by ELISA. Detection of T. gondii was observed by mouse bioassay and PCR in placentas and embryos from C. callosus females infected around 10 days pre-conception. However, only placentas, but not embryos, from females infected around 30 and 50 days pre-conception showed positivity for parasite DNA and seroconversion by mouse bioassay. In conclusion, this study model shows that vertical transmission of T. gondii may take place when maternal infection occurs within one month before conception, thus demonstrating the time of preconceptional seroconversion that rule out a risk of congenital toxoplasmosis.

Role of endogenous transplacental transmission in toxoplasmosis in sheep

To investigate the potential role of endogenous transplacental transmission of Toxoplasma gondii, 31 seropositive ewes presumed to be persistently infected with the parasite and 15 seronegative ewes were mated and monitored throughout pregnancy and lambing. Antibody titres were determined in precolostral sera from the liveborn lambs and in thoracic fluid from the dead lambs. A PCR for the B1 gene of T gondii was applied to the placentas from all the ewes and to the brains of the stillborn lambs. Samples of brain, lung, liver, spleen and heart from the dead lambs were examined by histopathology. No evidence of toxoplasmosis was detected by histopathology or PCR in any of the samples, but low titres of antibody to T gondii were detected in two liveborn, healthy offspring of a seropositive ewe by the immunofluorescent antibody test (3.2 per cent of pregnancies and 4.1 per cent of lambs in the seropositive group). Antibody to specific antigens of T gondii was demonstrated in sera from these two lambs by Western blotting.

Toxoplasmosis in Piglets

Seventeen-day-old piglets in a small holding farm in southern Thailand manifested signs of convulsion, fever, and death. The morbidity and mortality rate were approximately 26.09% (6/23) and 4.35% (1/23), respectively. Impression smear from lungs demonstrated tachyzoite stage of Toxoplasma gondii. Histopathological investigation revealed interstitial pneumonia. Further investigation, blood collection, educating the farmer, and prescribed affected herd with sulfa-trimethoprim were performed soon after Toxoplasma infection was demonstrated. A serological detection of T. gondii infection among affected herds using latex agglutination test was conducted on 14 serum samples. The overall seroprevalence was 71.43% (10/14). The titers were 1:64 in 3 pigs (21.43%), 1:128 in 4 (28.57%), 1:256 in 2 (14.29%), and 1:512 in 1 (7.14%). A cat in this farm showed antibody titer 1:32 while a dog was seronegative. Data derived from this case indicated two possible routes of transmission: transplacental infection and ingested food or water contaminated with oocysts shed by cat in this farm. However, rodents can not exclude as a role of toxoplasmosis transmission. Serological monitoring at slaughter houses combine with good sanitary practices, rodent and cat control in the farm are important measures to prevent toxoplasma infection and improve human health in the future.

Transmission of Toxoplasma gondii in an urban population of domestic cats (Felis catus)

Toxoplasma gondii is a protozoan parasite that infects humans and animal species worldwide. The relative importance of each potential transmission route in the complex life cycle of this coccidia is largely unknown, due to the lack of studies taking into account all routes simultaneously. In this study, we analyzed the transmission of T. gondii in an urban population of stray cats captured between 1993 and 2004. Analyzing prevalence, our aim was to determine which factors influence transmission in this population. Specific anti-T. gondii IgG antibodies were detected using the modified agglutination test. Firstly, we analyzed the kinetics of antibody titers in cats captured several times, using mixed linear models and correspondence analysis. We showed that antibody titers did not vary significantly with time and that titer 40 was the best threshold to separate individuals into two serological groups. Overall, prevalence was only 18.6%, thus transmission of T. gondii is infrequent in this population. As expected, a highly significant association was detected between age and presence of IgG antibodies. Prevalence was lowest in kittens aged 3-4 months, suggesting that newborn kittens may carry maternal antibodies and that vertical transmission is rare. After taking into account the effect of age, logistic regression showed that antibody carriage was related to factors that possibly related to the survival of oocysts: localization in the study site, origin of the cats, maximal temperatures and rain. Our results suggest that in this population, vertical transmission is rare, low predation limits prevalence, and oocyst survival is a determining factor in the risk of infection. We discuss the more general importance of conditions determining oocyst survival in the life cycle of T. gondii.

Globalization and the population structure of Toxoplasma gondii

Toxoplasma gondii is a protozoan parasite that infects nearly all mammal and bird species worldwide. Usually asymptomatic, toxoplasmosis can be severe and even fatal to many hosts, including people. Elucidating the contribution of genetic variation among parasites to patterns of disease transmission and manifestations has been the goal of many studies. Focusing on the geographic component of this variation, we show that most genotypes are locale-specific, but some are found across continents and are closely related to each other, indicating a recent radiation of a pandemic genotype. Furthermore, we show that the geographic structure of T. gondii is extraordinary in having one population that is found in all continents except South America, whereas other populations are generally confined to South America, and yet another population is found worldwide. Our evidence suggests that South American and Eurasian populations have evolved separately until recently, when ships populated by rats, mice, and cats provided T. gondii with unprecedented migration opportunities, probably during the transatlantic slave trade. Our results explain several enigmatic features of the population structure of T. gondii and demonstrate how pervasive, prompt, and elusive the impact of human globalization is on nature.

Prevalence of Toxoplasma gondii antibodies in rabbits (Oryctolagus cuniculus) from Mexico

Antibodies to Toxoplasma gondii were determined by indirect enzyme-linked immunosorbent assay in serum samples from domestic rabbits from 3 rabbit farms in Mexico. Antibodies to T. gondii were found in 77 (26.9%) of 286 animals. On the farm with the higher rearing standards, the seroprevalence was 18.7%, whereas on the farm with medium standards and another managed by a family, seroprevalence was 39.7 and 33.3%, respectively. This report is the first report concerning the prevalence of antibodies to T. gondii in rabbits from Mexico. Although the prevalence found in the present study is within the range reported for other countries, 2 of the farms revealed a relatively high prevalence, which was probably associated with the presence of cats inside rabbit houses.

Study on the transmission of Toxoplasma gondii by semen in rabbits

OBJECTIVE

To confirm the transmission of Toxoplasma gondii by semen and to investigate the impact of vaginal status on the transmission of T. gondii in female rabbits.

METHODS

Sixteen male rabbits were infected with T. gondii by intraperitoneal injection each with 1 x 10(5) RH tachyzoites. Eight rabbits died in 8-14 d after infection. unde Artificial vagina was used to collect semen from male rabbits weekly before and after infection for 8 weeks. If more than 2 portions of semen from 8 survived male rabbits were collected after infection, the collected semen was mixed weekly for later use. Twenty-seven female rabbits were divided into 4 groups: group 1 with normal vagina (7 rabbits), group 2 with wounded vagina (7), group 3 with trichomonas vaginitis (7) and group 4 with colpomycosis infection (6). Tachyzoites were found in mixed semen digested by trypsinate, and were used for endovaginal artificial insemination to female rabbits by uterine cavity tube once a week for 8 consecutive weeks. 2-3 d after every insemination, 2 ml blood was collected from helix vein of each rabbit, and stored at -40 degrees C for use. Anti-T. gondii antibody was examined by ELISA and the B1 gene of T. gondii was detected by PCR.

RESULTS

Anti-T. gondii antibody was detected in some rabbits be (2, 3, 1, and 1 rabbits from each of the groups respectively) on the 16th day after the first insemination. The positive rate of ELISA was 25.9%. The amplification of B1 gene (200 bp) by PCR appeared positive from the blood samples on the 3rd day after the first insemination and the last positive one was proved on the 51th day after the first insemination. Number of positive samples was 2, 1, 3 and 1 in the 4 groups respectively, with an overall PCR positive rate of 18.5%. Only 3 of the 27 rabbits were positive by both ELISA and PCR.

CONCLUSIONS

T. gondii can be transmitted by semen and the health status of vagina shows no impact on it.

Seroprevalence of Toxoplasma gondii in pregnant women and cats in Grenada, West Indies

Prevalence of antibodies against Toxoplasma gondii was studied in 534 pregnant women and 40 domestic cats in Grenada, West Indies. Antibodies (IgG) for T. gondii were sought in human sera by an enzyme-linked immunosorbent assay and in cat sera by using the modified agglutination test (MAT). Antibodies were found in 57 % of pregnant women. Seroprevalence increased with age; 51% of 15- to 19-yr-old women (100 total) had antibodies versus 60% of 20- to 24-yr-old women (127 total). Antibodies to T. gondii (MAT, 1:25 serum dilution) were found in 35% of cats; titers were 1:25 in 7 cats, 1:50 in 4 cats, and 1:500 in 3 cats. Epidemiological data suggested that the ingestion of food or water contaminated with oocysts was an important mode of transmission of T. gondii to women.

Zoonotic protozoa--food for thought

Outbreaks of water- and foodborne diseases caused by Cryptosporidium, Giardia and Toxoplasma are well documented. Three features of these zoonotic protozoa ensure a high level of environmental contamination and enhance the likelihood of waterborne transmission. Firstly, they are responsible for disease in a broad range of hosts including man, have a low infectious dose enhancing the possibility of zoonotic transmission, secondly, their transmissive stages are small in size and environmentally robust and thirdly are insensitive to the disinfectants commonly used in the water industry. In addition, there is growing evidence for the role that water and food can play in the transmission of the microsporidia, Balantidium and Blastocystis to humans.

Transmission of Toxoplasma: clues from the study of sea otters as sentinels of Toxoplasma gondii flow into the marine environment

Toxoplasma gondii affects a wide variety of hosts including threatened southern sea otters (Enhydra lutris nereis) which serve as sentinels for the detection of the parasite's transmission into marine ecosystems. Toxoplasmosis is a major cause of mortality and contributor to the slow rate of population recovery for southern sea otters in California. An updated seroprevalence analysis showed that 52% of 305 freshly dead, beachcast sea otters and 38% of 257 live sea otters sampled along the California coast from 1998 to 2004 were infected with T. gondii. Areas with high T. gondii exposure were predominantly sandy bays near urban centres with freshwater runoff. Genotypic characterisation of 15 new T. gondii isolates obtained from otters in 2004 identified only X alleles at B1 and SAG1. A total of 38/50 or 72% of all otter isolates so far examined have been infected with a Type X strain. Type X isolates were also obtained from a Pacific harbor seal (Phoca vitulina) and California sea lion (Zalophus californianus). Molecular analysis using the C8 RAPD marker showed that the X isolates were more genetically heterogeneous than archetypal Type I, II and III genotypes of T. gondii. The origin and transmission of the Type X T. gondii genotype are not yet clear. Sea otters do not prey on known intermediate hosts for T. gondii and vertical transmission appears to play a minor role in maintaining infection in the populations. Therefore, the most likely source of infection is by infectious, environmentally resistant oocysts that are shed in the feces of felids and transported via freshwater runoff into the marine ecosystem. As nearshore predators, otters serve as sentinels of protozoal pathogen flow into the marine environment since they share the same environment and consume some of the same foods as humans. Investigation into the processes promoting T. gondii infections in sea otters will provide a better understanding of terrestrial parasite flow and the emergence of disease at the interface between wildlife, domestic animals and humans.

Toxoplasmosis: beyond animals to humans

The parasitic zoonosis toxoplasmosis, which was poorly understood before the advent of the HIV epidemic, has become a major clinical problem worldwide. Humans acquire toxoplasmosis from cats, from consuming raw or undercooked meat and from vertical transmission to the foetus through the placenta during pregnancy. Studies of the unique environmental factors in various communities indicate the important roles that eating habits and culture have on the transmission of this infection. The socioepidemiological aspects of toxoplasmosis are thought to be important contributing factors for the spread of this disease. Preventative measures should consider the cultures and beliefs of people in various communities more than solving poverty and giving orthodox health education.