Evidence that primary infection of Charollais sheep with Toxoplasma gondii may not prevent foetal infection and abortion in subsequent lambings

Biosecurity for Reproductive Disease Prevention in Sheep and Goats

Infectious reproductive diseases pose a significant economic threat to sheep and goat operations. Maintaining records, a defined breeding season, and recognizing deviations from normal are crucial to herd health programs. Signs of suboptimal fertility, such as repeat breeding, unexpected open females, and abnormal gestational distributions, warrant further investigation. Important causes of infectious abortion discussed include chlamydiosis (enzootic abortion), coxiellosis, campylobacteriosis, toxoplasmosis, and brucellosis. Given the potential zoonotic nature of abortion in small ruminants, producer education is imperative. Implementing the sound biosecurity practices is critical for reducing the introduction of reproductive pathogens and enhancing the overall health of flocks and herds.

Detection of Toxoplasma gondii Infection in Small Ruminants: Old Problems, and Current Solutions

Toxoplasmosis is a parasitic zoonosis of veterinary importance, with implications for public health. Toxoplasma gondii infection causes abortion or congenital disease in small ruminants. Moreover, the consumption of infected meat, cured meat products, or unpasteurized milk and dairy products can facilitate zoonotic transmission. Serological studies conducted in various European countries have shown the high seroprevalence of specific anti-T. gondii antibodies in sheep and goats related to the presence of oocysts in the environment, as well as climatic conditions. This article presents the current status of the detection possibilities for T. gondii infection in small ruminants and their milk. Serological testing is considered the most practical method for diagnosing toxoplasmosis; therefore, many studies have shown that recombinant antigens as single proteins, mixtures of various antigens, or chimeric proteins can be successfully used as an alternative to Toxoplasma lysate antigens (TLA). Several assays based on DNA amplification have been developed as alternative diagnostic methods, which are especially useful when serodiagnosis is not possible, e.g., the detection of intrauterine T. gondii infection when the fetus is not immunocompetent. These techniques employ multicopy sequences highly conserved among different strains of T. gondii in conventional, nested, competitive, and quantitative reverse transcriptase-PCR.

A Meta-Analysis of the Prevalence of Toxoplasmosis in Livestock and Poultry Worldwide

Toxoplasma gondii causes toxoplasmosis with a global prevalence in the world. A large proportion of human illness is most frequently associated with consuming raw and undercooked meat or other animal products containing infective parasitic stages of T. gondii. This systematic review and meta-analysis study evaluated the prevalence of toxoplasmosis in cattle, sheep, camels, goats, and poultry worldwide. The search was performed in databases including PubMed, WoS, Scopus, Science Direct, Google Scholar, and ISC from 2000 to 2019 in Persian and English. The main inclusion criteria were the prevalence of toxoplasmosis among livestock and poultry and the prevalence indices by sample size. During these 20 years, the overall prevalence of toxoplasmosis in livestock and poultry was 28.3% (95% confidence interval (CI) 25-31.9%) using the random-effects meta-analysis model. The highest prevalence of T. gondii in livestock and poultry animals was found in Asia in 2014 with 89.8% (95% CI 78.5-95.5%). The lowest prevalence was found in Asia in 2013 with 1.26% (95% CI 0.4-3.8%). A quarter of livestock and poultry were infected with T. gondii. Since livestock products are globally important sources of people's diet, our findings are useful for policymakers to control T. gondii infection in livestock.

Global prevalence of Toxoplasma gondii infection in the aborted fetuses and ruminants that had an abortion: A systematic review and meta-analysis

Toxoplasma gondii (T. gondii) is a zoonotic apicomplexan protozoan that can cause reproductive losses in ruminants across the world. Therefore, a meta-analysis was conducted to estimate the worldwide prevalence of T. gondii infection in the aborted fetuses and stillbirths of sheep, goat, and cattle. Moreover, it attempted to evaluate the prevalence rate of T. gondii infection in ruminants that had abortions using serological methods. Based on the keywords, a systematic search of six databases was conducted to retrieve cross-sectional articles in English-language. Data were synthesized to calculate the overall prevalence of T. gondii infection worldwide using the random-effects model with a 95 % confidence interval (CI). Moreover, the present study includes sensitivity analysis, publication bias test, and quality assessment of the studies. The final analyses included 37, 19, and 8 studies conducted on sheep (4383 aborted fetuses and stillbirths as well as 1940 abortive sheep), goat (248 aborted fetuses and stillbirths and 533 abortive goats), and cattle (460 aborted fetuses and stillbirths and 165 abortive cattle). The overall prevalence rates of T. gondii infection in aborted fetuses and stillbirths globally were 42 % (95 % CI: 17 %-67 %), and 31 % (95 % CI: 11 %-51 %) using molecular methods for sheep and goats, as well as 16 % (95 % CI: 11 %-22 %) and 27 % (95 % CI: 1 %-54 %) using serological tests for sheep and goats, respectively. In addition, the overall prevalence rates of T. gondii infection in sheep and goats that had abortions were 56 % (95 % CI: 35 %-76 %) and 50 % (95 % CI: 6 %-94 %), respectively. These analyses could not be performed in cattle due to the small number of studies and the small number of animals under study. According to the high prevalence of T. gondii infection in sheep and goats that had an abortion, T. gondii could be a potential factor of causing reproductive failures in ruminants worldwide. So, effective control measures and strategies are needed to reduce the rate of abortion in sheep and goats as well as reduce the economic damage to the livestock industry.

From weaning to breeding age: Presence of antibodies to Toxoplasma gondii in sheep in the state of Espírito Santo, southeastern Brazil

Sheep are intermediate hosts of the protozoon Toxoplasma gondii, a zoonotic parasite that that may cause abortion and reproductive losses in this species. Previous studies have shown that its prevalence is high in sheep herds in Brazil, but no information from the state of Espírito Santo was available. The aim of this study was to improve the epidemiological data in different regions of this state by analyzing occurrences of anti-T. gondii antibodies in young female sheep, before reproductive age, using IFAT (cutoff ≥64). In addition, variables relating to these animals and farm management were investigated for significance of associations. A total of 312 sheep, aged 3 to 12 months, on five farms in five municipalities, were sampled. Among these 312 animals, 135 (43.26%) were reactive, and 70 positive sheep (51.8%) presented high titers (more than three times the cutoff).Eight-month-old sheep presented the lowest occurrence and 7 and 11-month-old sheep, the highest. At least one animal was positive in each municipality, thus confirming the endemic status of toxoplasmosis in sheep in this region. None of the variables analyzed, relating to animals and herds, presented any association with T. gondii occurrence (p > 0.05). The number of females that were close to sexual maturity (12 months) and which were reactive to T. gondii was less than 50%. These ewes would probably be more susceptible to reproductive problems.

Vertical transmission of Toxoplasma gondii in naturally infected ewes in the semiarid region of Brazil

To evaluate transplacental transmission of Toxoplasma gondii in naturally infected ewes, blood samples were collected from 55 pregnant ewes and their offspring, before ingestion of colostrum. From 16 offspring of positive ewes and nine offspring from negative ewes, blood samples were obtained after 48 h and 7, 14, 21, 28, 35, 42, 49 and 56 days after birth. T. gondii antibodies were detected in serum samples using the indirect fluorescence antibody test (IFAT ≥ 64). Four of the 30 positive ewes (13.3 %) had offspring positive for T. gondii before ingesting colostrum (vertical transmission). The colostrum antibody titers decreased every week, and only 20 % (2/10) of the lambs in continued to present detectable antibody titers until day 56 after birth. Therefore, vertical transmission of T. gondii in lambs was indication of occur and is an important route for transferring and maintaining the agent in sheep herds in the Brazilian semiarid region.

Schizophrenia as a pseudogenetic disease: A call for more gene-environmental studies

In recent years schizophrenia has been assumed to be largely a genetic disease with heritability estimates, derived primarily from family and twin studies, of 80%-85%. However, the results of genetic research on schizophrenia have not yielded results consistent with that estimate of heritability. In particular, extensive genetic studies have not led to new methods for diagnosis and treatment. An examination of the twin studies on which heritability is based shows why such studies exaggerate the genetic component of schizophrenia. In addition, the effects of infectious agents such as Toxoplasma gondii and the composition of the microbiome can produce a clinical picture that would also appear to be largely genetic due to familial aggregation and a role for a partial genetic contribution to the immune system. It is concluded that the genetic component of schizophrenia may have been overestimated and an increased focus on gene-environmental interactions is likely to accelerate research progress on this disease.

Congenital Transmission of Toxoplasma gondii After Experimental Reinfection With Brazilian Typical Strains in Chronically Infected Sheep

Toxoplasma gondii is a cause of congenital diseases, miscarriages and stillbirths in production animals. In Brazil, non-archetypal genotypes of the parasite may be related to severe disease. Experimental infection with T. gondii was studied in sheep to analyse congenital transmission-related parameters in reinfections with different Brazilian parasite strains. Thirteen T. gondii-seronegative sheep were orally infected with 2 × 10³oocysts for the primary infection: G1 (4 animals) were inoculated with TgCatBr71 strain (Type BrI genotype) and G2 andG3 (5 and 4 animals, respectively) withTgCatBr60 strain (Type BrIII genotype). After chronification of infection, the animals were impregnated. A second infection was performed after 60 days of gestation. TheG1 andG3 animals were inoculated withTgCatBr60BrIII and the G2 animals withTgCatBr71 BrI oocysts. The effects of reinfection were compared with a control group (5 animals) through physical examination, ultrasound imaging and serology. Ovine experimental infections were evaluated using mouse bioassays, molecular analysis, serological tests, histopathology, and immunohistochemistry. No abortions occurred; a seropositive lamb and a mummified fetus from G2-BrIIIxBrI were produced. The vertical transmission rate detected in lambs from chronically infected sheep was 31.6% (6/19). It is demonstrated that reinfection and subsequent congenital transmission occured in one sheep with a primary Brl infection challenged with BrIII genotype of T. gondii. In a twin pregnancy from G2-BrIIIxBrI, congenital transmission from a latent infection was detected in both lambs. Congenital transmission could not be tracked in three lambs. Overall, previous T. gondii infection may fail to protect against congenital transmission from a reinfection and primary infection induced insufficient protection against vertical transmission which must be taken into account in decision-making for the use of seropositive animals as breeders. Similar trials with larger groups and contemplating host cellular immune response studies should be conducted to evaluate the actual impact of T. gondii reinfection involving different strains in sheep.

High frequency of infection of lung cancer patients with the parasite Toxoplasma gondii

BACKGROUND

Toxoplasma gondii is an intracellular protozoan parasite that can cause a wide range of clinical conditions, including miscarriage and pneumonia. The global prevalence is 30% in humans, but varies by locality (e.g. in the UK it is typically 10%). The association between lung cancer and T. gondii infection was investigated by direct detection in lung tissue samples.

METHODS

Lung tissue samples were taken from patients undergoing lung resection surgery (n=72) for suspected lung cancer (infection prevalence 100% (95% CI: 93.9-100%)). All 72 participants were confirmed as having lung cancer following subsequent diagnostic tests. In addition, bronchial biopsy samples were collected from non-lung cancer healthy control subjects (n=10). Samples were tested for T. gondii using PCR amplification of T. gondii specific gene markers and T. gondii specific immunohistochemistry.

RESULTS

All 72 lung cancer patients were infected with T. gondii (prevalence 100% (95% CI: 93.9-100%)). Of which, 95.8% (n=69) of patients showed evidence of active parasite stages. Infection prevalence in the controls (10%) was significantly lower (p<0.0001).

CONCLUSIONS

Clinicians treating lung cancer patients should be aware of the potential presence of the parasite, the potential for induction of symptomatic complications and interference with treatment success.

Ocorrência de anticorpos anti-Toxoplasma gondii e anti-Neospora caninum em ovinos com distúrbios reprodutivos e fatores de risco

RESUMO: Objetivou-se avaliar a ocorrência, sinais clínicos e fatores de risco associados a soropositividade para Toxoplasma gondii e Neospora caninum em ovinos. Foram utilizados 294 animais com histórico de distúrbios reprodutivos de 28 fazendas do estado de São Paulo, Brasil, diagnosticados através da imunofluorescência indireta (1:64 e 1:50). A ocorrência de T. gondii foi de 29,9% (88/294) e de N. caninum 18% (53/294), sendo 3,7% (11/294) dos ovinos soropositivos para ambos. Observou-se com maiores chances à infecção pelo T. gondii: ovinos mestiços (p=0,04), Santa Inês (p=0,006), fornecimento de pastagem (p<0,001) ou associada a concentrado (p<0,001), uso exclusivamente de monta natural (p=0,002, OR=2,28 e IC95%=1,37-3,79) e a presença de aves nas propriedades (p=0,001). Na infecção por N. caninum essa chance aumentou em: fêmeas (p=0,031), propriedades sem aprisco (p<0,001) e sistema de criação semi-intensivo (p<0,001). Em relação ao histórico de problemas reprodutivos, ovelhas infectadas pelo N. caninum e T. gondii apresentaram redução da chance de apresentarem abortamento (p=0,044) e repetição de estro (p=0,025) respectivamente. O T. gondii esteve mais presente sorologicamente que o N. caninum em ovinos com histórico de distúrbios reprodutivos e apesar de suas semelhanças, diferiram epidemiologicamente em aspectos relacionados as características da criação como raça, sexo, sistema de criação, tipo de alimentação e manejo reprodutivo.

Investigation into the genetic diversity in toll-like receptors 2 and 4 in the European badger Meles meles

The Toll-like receptor (TLR) genes are a conserved family of genes central to the innate immune response to pathogen infection. They encode receptor proteins, recognise pathogen associated molecular patterns (PAMPs) and trigger initial immune responses. In some host-pathogen systems, it is reported that genetic differences, such as single nucleotide polymorphisms (SNPs), associate with disease resistance or susceptibility. Little is known about TLR gene diversity in the European badger (Meles meles). We collected DNA from UK badgers, carried out PCR amplification of the badger TLR2 gene and exon 3 of TLR4 and determined DNA sequences for individual badgers for TLR2 (n = 61) and TLR4 exon 3 (n = 59). No polymorphism was observed in TLR4. Three TLR2 amino acid haplotype variants were found. Ninety five percent of badgers were homozygous for one common haplotype (H1), the remaining three badgers had genotypes H1/H3, H1/H2 and H2/H2. By broad comparison with other species, diversity in TLR genes in badgers seems low. This could be due to a relatively localised sampling or inherent low genetic diversity. Further studies are required to assess the generality of the low observed diversity and the relevance to the immunological status of badgers.

Congenital Toxoplasmosis in Chronically Infected and Subsequently Challenged Ewes

This experiment studied congenital transmission in sheep experimentally infected with oocysts of Toxoplasma gondii and reinfected at one of three stages of pregnancy. Twenty ewes were experimentally infected with T. gondii strain ME49 (day 0). After the T. gondii infection became chronic (IFAT≤512), the ewes were allocated with rams for coverage. After the diagnosis of pregnancy, these ewes were allocated into four experimental groups (n = 5): I-reinfected with T. gondii on the 40^th day of gestation (DG); II-reinfected on DG 80; III-reinfected on DG 120; and IV-saline solution on DG 120 (not reinfected). Five ewes (IFAT<64) were kept as negative controls (uninfected, group V), therefore in groups I-III were infected prior to pregnancy and re-infected during pregnancy, group IV was only infected prior to pregnancy, and group V was not infected. Parasitism by T. gondii was investigated (histopathology, immunohistochemistry, mouse bioassay and PCR) in mothers and lambs tissue. All ewes produced lambs serologically positive for T. gondii. The results of the mouse bioassay, immunohistochemistry and PCR assays revealed the presence of T. gondii in all 20 sheep and their lambs. The congenital transmission of T. gondii was associated with fetal loss and abnormalities in persistently infected sheep and in ewes infected and subsequently reinfected by this protozoan. Therefore, congenital T. gondii infection was common when ewes were chronically infected prior to pregnancy, with or without reinfection during at various stages of gestation.

Role of vertical transmission of Toxoplasma gondii in prevalence of infection

The parasite, Toxoplasma gondii, is a highly successful pathogen that infects around 30% of the global human population. Additionally, it is able to infect all warm blooded animals with high prevalence. This is surprising as it is a parasite of the cat and can only complete its full sexual cycle in that host. This review examines the important key routes of transmission: infective oocysts from the cat, ingestion of raw infected tissue and vertical transmission. The latter route of transmission has traditionally been thought to be rare. In this review, this assumption is examined and discussed in the light of the current literature. The available evidence points to the possibility that vertical transmission occurs frequently in natural populations of mice however the evidence in sheep is currently ambivalent and controversial. In humans, the situation appears as though vertical transmission may be rare although there is still much that is unexplained.

Spread and genotype of Toxoplasma gondii in naturally infected alpine chamois (Rupicapra r. rupicapra)

The complex life cycle of Toxoplasma gondii involves many animal species, raising zoonotic, economic, and conservation issues. This complexity is reflected in the molecular structure of T. gondii, whose different genotypes differ in pathogenicity. Among the intermediate hosts of T. gondii, wild ungulates may be a source of human infection. Despite intense hunting activity and the consumption of raw or undercooked meat, little information is available on the spread of T. gondii and the distribution of its genotypes in these species, including the alpine chamois (Rupicapra r. rupicapra). Ninety-three sera and 50 brain tissues from chamois were sampled (1) to investigate the spread of T. gondii with serological and molecular analyses, and (2) to genotype the strains with a restriction fragment length polymorphism analysis of the SAG2 locus. The prevalence of T. gondii was low on both serological (3.2 %) and molecular (2 %) analyses, and infections were concentrated in individuals >1 year old. These findings demonstrate the sporadic presence of the protozoan in this species on consistent diagnostic tests. Horizontal transmission seems to be the main route of infection, and cats are the only definitive host in the study area. This prevalence suggests that the environment of the chamois is less contaminated with oocysts than environments close to human settlements. The SAG2 type II genotype was detected in this species for the first time. Although this genotype is predominant in human toxoplasmosis, these results suggest that the chamois is a minor source of human infection.

Toxoplasma gondii Infection in Alpine Red Deer (Cervus elaphus): Its Spread and Effects on Fertility [corrected]

In contrast to the depth of knowledge on the pathological effects of parasitism in domestic animals, the impact of the vast majority of parasites on wildlife hosts is poorly understood and, besides, information from domestics is rarely usable to disclose the parasites' impact on free-ranging populations' dynamics. Here we use Toxoplasmosis as a study model since, until now, the infection process and the protozoan's effects in natural conditions has received little attention. We analysed 81 sera from red deer (Cervus elaphus) sampled in Italian Alps and through generalized linear models we evaluated (1) the epidemiological factors influencing T. gondii infection dynamics; (2) its impact on female fertility [corrected]. High seroprevalence of T. gondii infection was recorded in yearling (1 year-old; prevalence = 52.4%) and adult (>2 year-old; prevalence = 51.3%) red deer, while calves (<1 year-old) did not contract the infection suggesting horizontal transmission as the main route of infection. The stable prevalence between yearlings and adults and the higher serological titres of younger individuals lead to two alternative infection processes suggesting a difference between age classes or in acquiring the infection or in responding to the pathogen. No associations between T. gondii serological titres and pregnancy status was observed indicating no direct effect on the probability of being pregnant; nevertheless a relation between females' higher serological titres and lower foetal development emerged, suggesting potential effects of the parasite infection on deer reproduction. The results demonstrate high seroprevalence of T. gondii infection in free-ranging red deer and, furthermore, the effect on foetal development suggests the potential impact of the parasite on red deer fertility and thus on its population dynamics.

Secreted effectors in Toxoplasma gondii and related species: determinants of host range and pathogenesis?

Recent years have witnessed the discovery of a number of secreted proteins in Toxoplasma gondii that play important roles in host-pathogen interactions and parasite virulence, particularly in the mouse model. However, the role that these proteins play in driving the unique features of T. gondii compared to some of its nearest apicomplexan relatives (Hammondia hammondi and Neospora caninum) is unknown. These unique features include distinct dissemination characteristics in vivo and a vast host range. In this review we comprehensively survey what is known about disease outcome, the host response and host range for T. gondii, H. hammondi, and N. caninum. We then review what is presently known about recently identified secreted virulence effectors in these three genetically related, but phenotypically distinct, species. Finally we exploit the existence of genome sequences for these three organisms and discuss what is known about the presence, and functionality, of key T. gondii effectors in these three species.

Parasite distribution and associated immune response during the acute phase of Toxoplasma gondii infection in sheep

BACKGROUND

In many countries, Toxoplasma gondii (T. gondii) is a major cause of reproductive disorders and abortions in the sheep industry, and therefore responsible for important financial and economic losses. In addition, undercooked infected lamb is an important risk factor for human toxoplasmosis. In the present study, the initial phase of the infection was investigated: the parasite's entry site, the subsequent distribution of the parasite and the host-immune response.

RESULTS

Parasite DNA was already detected in the cranial small intestinal mucosa the first days after oral infection with T. gondii tissue cysts. Simultaneously, high IFN-gamma and IL-12 responses were induced mainly in the mesenteric lymph nodes. The emergence of IgG1 (at 8dpi), and IgG2 (at 11 dpi) was accompanied by a decrease or even disappearance of the IFN-gamma and IL-12 response in the Peyers' patches (PP), PBMC's and popliteal LN's. Meanwhile the parasite DNA could be recovered from most mucosal and systemic tissues to become undetectable in the small intestine, popliteal LN, PBMC and spleen 3 weeks pi.

CONCLUSIONS

Our results indicate that parasites enter the cranial small intestine the first days after infection and that after an increase the first two weeks after infection, the parasite DNA levels in the intestine drop below the detection limit three weeks after infection. This coincides with an increase in parastic-specific serum IgG1 and IgG2 and a decrease of the antigen-specific IFN-gamma response in PP, PBMC and popliteal LN. We suggest a role for IFN-gamma and IL-12 in controlling the infection.

Prevalence ofToxoplasma gondiiin localized populations ofApodemus sylvaticusis linked to population genotype not to population location

Toxoplasma gondiiis a globally distributed parasite infecting humans and warm-blooded animals. Although many surveys have been conducted forT. gondiiinfection in mammals, little is known about the detailed distribution in localized natural populations. In this study, host genotype and spatial location were investigated in relation toT. gondiiinfection. Wood mice (Apodemus sylvaticus) were collected from 4 sampling sites within a localized peri-aquatic woodland ecosystem. Mice were genotyped using standardA. sylvaticusmicrosatellite markers andT. gondiiwas detected using 4 specific PCR-based markers: SAG1, SAG2, SAG3 and GRA6 directly from infected tissue. Of 126 wood mice collected, 44 samples were positive giving an infection rate of 34·92% (95% CI: 27·14–43·59%). Juvenile, young adults and adults were infected at a similar prevalence, respectively, 7/17 (41·18%), 27/65 (41·54%) and 10/44 (22·72%) with no significant age-prevalence effect (P = 0·23). Results of genetic analysis of the mice showed that the collection consists of 4 genetically distinct populations. There was a significant difference inT. gondiiprevalence in the different genotypically derived mouse populations (P = 0·035) but not between geographically defined populations (P = 0·29). These data point to either a host genetic/family influence on parasite infection or to parasite vertical transmission.

Outbreak of ovine congenital toxoplasmosis in Iran, confirmed by different diagnostic methods

Toxoplasma gondii is a zoonotic obligatory intracellular protozoan parasite with the capability to infect all warm-blooded animals. One of the great concerns is that it can lead to ovine abortion in sheep growing industry. Different diagnostic methods such as serology, pathology, immunohistochemistry, bioassay and molecular detection have been used in order to detect ovine abortion associated with T. gondii. In this case, an outbreak of congenital toxoplasmosis based on serological, macroscopic, pathological detection and isolation of T. gondii by bioassay is described and emphasized on the importance of this route of transmission that caused lamb losses and an increase in possible sources of infection for human and environment.

Toxoplasma gondii: prevalence in species and genotypes of British bats (Pipistrellus pipistrellus and P. pygmaeus)

Few studies have investigated Toxoplasma gondii infections in bat populations and none have reported its presence in protected British bat species. Using a collection of dead/euthanased bats collected from Lancashire, UK, two species of bats (Pipistrellus pipistrellus and Pipistrellus pygmaeus) were tested using a highly sensitive SAG1-PCR method specific for detection of T. gondii DNA (n=77; 71 P. pipistrellus and 6 P. pygmaeus). Whilst some potential bias may exist in the sampling strategy, an overall prevalence of 10.39% (±6.06%; 95%CI) was detected. All P. pipistrellus, were also genotyped using eleven polymorphic microsatellite loci to determine their local population structure. The programme STRUCTURE revealed that the majority of individuals (83%) were derived from one interbreeding population, and the remaining individuals (17%) had mixed genetic origins. There was no significant difference in the frequency of T. gondii infection or geographical distribution between subclusters. As all British bats are insectivorous, the routes of infection with T. gondii remain elusive. However, the locally large and panmictic gene pool suggests that intraspecies transmission could be applicable.

Toxoplasma gondii abortion storm in sheep on a Texas farm and isolation of mouse virulent atypical genotype T. gondii from an aborted lamb from a chronically infected ewe

Sheep are commonly infected with the protozoan parasite, Toxoplasma gondii. Infection may cause early embryonic death and resorption, fetal death and mummification, abortion, stillbirth, and neonatal death. Most sheep acquire T. gondii infection after birth. Recent studies reported that congenital ovine transmission of T. gondii may be more common than previously believed, but these findings are solely based on PCR data and require confirmation using other techniques to verify the findings. In the present study, during the lambing season of 2005 a toxoplasmosis abortion storm occurred in a flock of purebred Suffolk ewes on a farm in Texas. Only 14 healthy lambs were born, and 38 abortuses, mummies and weak or stillborn lambs were delivered. Another 15 fetuses identified by ultrasound were presumably resorbed or were aborted undetected. Antibodies to T. gondii were found in 37 (94.8%) of the 39 ewes and 30 of them had high titers (1:3200 or higher) when tested in the modified agglutination test (MAT). In the 2006 lambing season, two (both with MAT titers of ≥ 3200 in 2005) of 26 ewes delivered T. gondii infected lambs. T. gondii tissue cysts were found histologically in lesions of encephalitis in a lamb from one ewe and viable T. gondii (designated TgShUs55) was isolated from the brain and heart of a lamb from the second ewe. TheTgShUs55 had an atypical genotype using 10 PCR-RFLP markers, and was 100% lethal for Swiss Webster mice, irrespective of the dose or the stage of the parasite inoculated. In subsequent seasons, the ewes lambed normally. The results of the present study support the hypothesis that most sheep that have aborted due to T. gondii develop protection against future toxoplasmosis induced abortion, but the protection is not absolute.

Increased Toxoplasma gondii positivity relative to age in 125 Scottish sheep flocks; evidence of frequent acquired infection

Toxoplasma gondii seroprevalence was determined in 3333 sheep sera from 125 distinct sheep flocks in Scotland, with the majority of flocks being represented by 27 samples, which were collected between July 2006 and August 2008. The selected farms give a representative sample of 14,400 sheep holdings identified in the Scottish Government census data from 2004. Overall T. gondii seroprevalence, at individual sheep level, was determined to be 56.6%; each flock tested, had at least a single positive animal and in four flocks all ewes tested positive. The seroprevalence of sheep increased from 37.7% in one year old stock to 73.8% in ewes that were older than six years, showing that acquired infections during the life of the animals is frequent and that environmental contamination by T. gondii oocysts must be significant. The median within-flock seroprevalence varied significantly across Scotland, with the lowest seroprevalence of 42.3% in the South and the highest seroprevalence of 69.2% in the far North of Scotland and the Scottish Islands, while the central part of Scotland had a seroprevalence of 57.7%. This distribution disequilibrium may be due to the spread and survival of oocysts on pasture and lambing areas. A questionnaire accompanying sampling of flocks identified farms that used Toxovax®, a commercial vaccine that protects sheep from abortion due to T. gondii infection. Only 24.7% of farmers used the vaccine and the vaccine did not significantly affect the within flock seroprevalence for T. gondii. The implications for food safety and human infection are discussed.

Prevalence and co-infection of Toxoplasma gondii and Neospora caninum in Apodemus sylvaticus in an area relatively free of cats

The protozoan parasite Toxoplasma gondii is prevalent worldwide and can infect a remarkably wide range of hosts despite felids being the only definitive host. As cats play a major role in transmission to secondary mammalian hosts, the interaction between cats and these hosts should be a major factor determining final prevalence in the secondary host. This study investigates the prevalence of T. gondii in a natural population of Apodemus sylvaticus collected from an area with low cat density (<2·5 cats/km2). A surprisingly high prevalence of 40·78% (95% CI: 34·07%-47·79%) was observed despite this. A comparable level of prevalence was observed in a previously published study using the same approaches where a prevalence of 59% (95% CI: 50·13%-67·87%) was observed in a natural population of Mus domesticus from an area with high cat density (>500 cats/km2). Detection of infected foetuses from pregnant dams in both populations suggests that congenital transmission may enable persistence of infection in the absence of cats. The prevalences of the related parasite, Neospora caninum were found to be low in both populations (A. sylvaticus: 3·39% (95% CI: 0·12%-6·66%); M. domesticus: 3·08% (95% CI: 0·11%-6·05%)). These results suggest that cat density may have a lower than expected effect on final prevalence in these ecosystems.

Study on ovine abortion associated withToxoplasma gondiiin affected herds of Khorasan Razavi Province, Iran based on PCR detection of fetal brains and maternal serology

Toxoplasma gondii, an obligatory intracellular protozoan parasite, is one of the causative agents of ovine abortion, as reported in many countries. Different techniques are being used to detect this pathogen in infected ovine fetuses. One of the most sensitive and specific diagnostic techniques is Nested-PCR amplification of the B1 target gene of the organism. In total, 200 brain samples of aborted ovine fetuses and maternal sera submitted from different parts of Khorasan Razavi province, Iran were investigated to track the role ofToxoplasma gondiiin ovine abortion by a slightly modified Nested-PCR and IFAT assays, respectively. Among all samples, 27 (13·5%) were PCR-positive and 31 (15·5%) were IFAT-positive and theToxoplasma-induced abortion prevalence calculated was 8·8% to18·2% with 95% confidence interval. Results show that high levels of congenital transmission may occur in 27/31(87%) of pregnancies with an excellent logical agreement (ĸ=0·9) between 2 different tests. According to the results of this study, the Nested-PCR employed in this investigation could be recommended as an applied routine test for the routine examination and confirmation ofToxoplasma gondii-induced ovine abortion.

Evaluation of Toxoplasma gondii and Neospora caninum infections in sheep from Uberlândia, Minas Gerais State, Brazil, by different serological methods

Toxoplasmosis and neosporosis have been recognized as economically important diseases with considerable impact on the livestock industry. Considering the scarce information on the occurrence of Toxoplasma gondii and Neospora caninum infections in sheep from Uberlândia, Minas Gerais State, Brazil, this study aimed to investigate the frequency of antibodies against these parasites in sheep sera from this region by using different serological methods. A total of 155 sheep serum samples were analyzed by the indirect fluorescence antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA) for the detection of IgG against T. gondii and N. caninum. Seroreactivity by IFAT showed 80% of samples with titers between 512 and 2048 for T. gondii (cutoff ≥ 64) and 78% presenting titers between 50 and 200 for N. caninum (cutoff ≥ 50). Seroreactivity by ELISA showed 75% of samples with ELISA index (EI) between 2.0 and 3.0 for T. gondii (cutoff ≥ 1.3) and 54% presenting EI between 1.3 and 2.0 for N. caninum (cut off ≥ 1.3). Discordant results by both tests were analyzed by immunoblot, resulting in a total seropositivity of 61% for T. gondii and 23% for N. caninum, with 41% to T. gondii only, 3% to N. caninum only, and 20% to both parasites. There was a significant positive association between seropositivity to T. gondii and age over one year (P<0.001), but such association was not found for N. caninum infection. In conclusion, as T. gondii and N. caninum infections are simultaneously present in sheep flocks of this region, it should be emphasized the importance to carry out a regular monitoring of Toxoplasma infection due to its high prevalence, its zoonotic potential and induction of reproductive disorders leading to economic losses. For neosporosis, sheep farmers should be instructed about the presence of the parasite in the flock, its risk factors and potential abortifacient role in sheep. Differential flock management could be valuable tool to establish the association of serological positivity and reproductive disease induced by N. caninum in sheep.

Mic1-3 Knockout Toxoplasma gondii is a good candidate for a vaccine against T. gondii-induced abortion in sheep

This study assessed the effectiveness of a mutant strain of Toxoplasma gondii (RH strain) lacking the mic1 and mic3 genes (Mic1-3KO) against Toxoplasma abortion in sheep. Ewes were inoculated subcutaneously with 10⁵ Mic1-3KO tachyzoïtes in three independent experiments. Following vaccination, Mic1-3KO induced a mild febrile response and serum IgG antibodies, which persisted throughout the experiments. Tissue cysts formed in the sheep, but were not, under our experimental conditions, infectious when given orally. Ewes were mated two months after vaccination and were orally challenged with the PRU strain of T. gondii at mid-gestation (400 oocysts in Experiments 1 and 2; 100 oocysts in Experiment 3). Challenge of vaccinated pregnant ewes resulted in a slight febrile response, whereas unvaccinated ewes developed a more severe, characteristic febrile response of longer duration. After challenge, all unvaccinated ewes aborted whereas 62%, 91% and 64% (Experiments 1, 2 and 3 respectively) of the lambs from vaccinated ewes were viable, with no clinical signs of infection. Mic1-3KO was as effective as S48, the strain used as a live vaccine for sheep (Toxovax^®). A dose of 10⁵ Mic1-3KO tachyzoites was sufficient to induce protection (versus a dose of 2 × 10⁶). Both subcutaneous and intraperitoneal injections were effective. Moreover, preliminary results showed the potential of Mic1-3KO to reduce the development of tissue cysts in lambs born to vaccinated ewes. This study demonstrates that Mic1-3KO is a potent vaccine candidate.

Ovine toxoplasmosis

Congenital infection with Toxoplasma gondii is an important cause of abortion in sheep worldwide. The cat is the definitive host of the parasite, and infected cats may shed millions of oocysts in their faeces resulting in extensive environmental contamination and an important source of infection for grazing herbivorous animals. Studies looking at development of specific antibodies in sheep, as an indicator of exposure to T. gondii, have shown that there is an increase in seroprevalence associated with age indicating that most infections in sheep occur following birth. The stage of gestation when transplacental transmission of T. gondii to the developing foetus occurs is critical in determining the clinical outcome. The importance of endogenous transplacental transmission in persistently infected ewes and its clinical importance is a subject of current debate. Ewes infected prior to mating develop immune responses that help protect against disease in a subsequent pregnancy and also against experimental challenge administered during pregnancy. Both innate and adaptive immune responses are activated following T. gondii infection and experiments involving the chronic cannulation of peripheral lymph nodes in sheep have allowed the dynamics of the immune responses to be analysed in real time. A live vaccine, Toxovax® is the only commercially available vaccine worldwide to protect against congenital toxoplasmosis.

Evidence for high levels of vertical transmission in Toxoplasma gondii

Toxoplasma gondii is a highly ubiquitous and prevalent parasite. Despite the cat being the only definitive host, it is found in almost all geographical areas and warm blooded animals. Three routes of transmission are recognised: ingestion of oocysts shed by the cat, carnivory and congenital transmission. In natural populations, it is difficult to establish the relative importance of these routes. This paper reviews recent work in our laboratory which suggests that congenital transmission may be much more important than previously thought. Using PCR detection of the parasite, studies in sheep show that congenital transmission may occur in as many as 66% of pregnancies. Furthermore, in families of sheep on the same farm, exposed to the same sources of oocysts, significant divergent prevalences of Toxoplasma infection and abortion are found between different families. The data suggest that breeding from infected ewes increases the risk of subsequent abortion and infection in lambs. Congenital transmission rates in a natural population of mice were found to be 75%. Interestingly, congenital transmission rates in humans were measured at 19.8%. The results presented in these studies differ from those of other published studies and suggest that vertical transmission may be much more important than previously thought.