Survey to determine the seroprevalence of Toxoplasma gondii infection in British sheep flocks

Differences in Toxoplasma gondii distribution in different muscle and viscera of naturally infected sheep

Toxoplasma gondii (T. gondii) is a zoonotic parasite that can cause serious pathology in intermediate hosts such as humans and animals. Eating undercooked or raw meat is the most important route of infection by T. gondii. Sheep are an important source of meat worldwide, and they are also susceptible to T. gondii. Mutton infected with T. gondii poses a serious threat to the food safety of consumers. At present, studies have mainly focused on the infection ratio of T. gondii in livestock; however, systematic studies have not been performed on differences in the distribution of this parasite in different muscle and viscera tissues of animals. In this study, the differences in the distribution of T. gondii in naturally infected Small-tailed Han sheep was studied. By amplifying the B1 gene of the parasite via real-time fluorescence quantification PCR (RT‒qPCR), we found that the parasite burden of T. gondii differed among different parts of the sheep, with the highest burden observed in the heart among the viscera and the external ridge among the muscle. The relative expression was ranked from high to low in our study as follows: heart, spleen, external ridge, tenderloin, lung, liver, kidney, neck meat, forelegs, cucumber strips, hind leg, lamb belly, and lamb chops. This study provided important guidance for monitoring the food safety of mutton products.

A Review of Toxoplasma gondii in Animals in Greece: A FoodBorne Pathogen of Public Health Importance

Toxoplasma gondii is a zoonotic protozoon with a complex life cycle and the second most important foodborne pathogen in Europe. Surveillance of toxoplasmosis is based on national considerations since there are no mandatory controls along the food chain in the European Union, and underreporting of meat is still a problem in many countries like Greece. The current review provides an overview of T. gondii prevalence, associated risk factors, and surveillance in animals in Greece, focusing on the transmission role of meat and highlighting the control measures that should be adopted by consumers. Sows, wild boars, hares, equines, and cats had lower, while sheep and goats generally had higher seroprevalence than their respective pooled European and global values. Seroprevalence in chickens was similar between Greece and Europe, while there was high variation in cattle studies, with no data regarding dairy products. Though a comprehensive meat safety assurance system is the most effective approach to control the principal biological hazards associated with meat, such as T. gondii, the prerequisite risk categorisation of farms and abattoirs based on EFSA's proposed harmonised epidemiological indicators has not materialised as yet in Greece. Therefore, comprehensive control strategies are still required to ensure food safety and safeguard public health.

Toxoplasma gondii infection in sheep from Romania

BACKGROUND

Toxoplasmosis is a widespread zoonosis caused by the intracellular protozoan parasite Toxoplasma gondii. Limited epidemiological information is available about the prevalence of T. gondii in sheep in Romania, and a high incidence would have implications for both the economy and public health. To our knowledge, no studies are available about the T. gondii strains circulating in lambs. The objective of this study was to assess the prevalence of T. gondii in sheep (serology), lambs (serology, bioassay, PCR) and sheep abortions (PCR) in Romania. Moreover, the study aimed to perform the genetic characterization of T. gondii isolates from lambs.

METHODS

Serum samples collected from 2650 sheep (2067 adults and 583 lambs) were tested for anti-T. gondii antibodies (IgG) using a commercial ELISA kit. Likewise, 328 pairs of diaphragmatic muscle-serum samples were collected from lambs aged between 2 and 4 months. Lamb serum samples were analyzed using MAT for anti-T. gondii antibody detection. The diaphragm tissue samples from MAT-positive lambs (at a dilution ≥ 1:25) were bioassayed in mice. The T. gondii strains were genotyped using 15 microsatellites markers. Additionally, brain and heart samples from 76 sheep abortions were analyzed for T. gondii DNA by polymerase chain reaction (PCR) targeting the 529-bp repeat region (REP529).

RESULTS

The results showed that more than half of the tested sheep were T. gondii seropositive (53.5%). The seroprevalence was significantly higher in adults (61.1%) than in lambs (26.4%). The seroprevalence of T. gondii infection in slaughtered lambs, by MAT, was 37.5% (123/328). There were bioassayed in mice 56 diaphragmatic tissues from 123 seropositive lambs. Toxoplasma gondii strains were isolated from 18 (32.1%) lambs intended for human consumption. All T. gondii strains were confirmed by PCR. Six strains were genotyped using 15 microsatellite markers and belonged to genotype II. Toxoplasma gondii DNA was detected in 11.8% (9/76) of sheep abortions.

CONCLUSIONS

The present study showed the presence of T. gondii in sheep in all the regions considered in the study. The high prevalence of T. gondii infection in sheep and lambs, demonstrated by serology, molecular analysis and bioassay, highlighted that there is an important risk of human infection in consuming raw or undercooked sheep/lamb meat.

Seroprevalence of Toxoplasma gondii infection in sheep and goats from different geographical regions of the world: Systematic review and meta-analysis

The Toxoplasma gondii is an obligate intracellular protozoan parasite which significantly impact small ruminant productivity, international animal trade and transboundary movement of animal across the globe. The seroprevalence of T. gondii infection (toxoplasmosis) in sheep and goats is widely studied in many parts of the world and there is a lack of comprehensive information on prevalence estimates considering the global and regional perspectives. The aim of the study was to use systematic review and meta-analysis methods to estimate the global and regional pooled seroprevalence of T. gondii infection in sheep and goats, as well as factors that influence prevalence estimations. Relevant articles reporting the seroprevalence of toxoplasmosis in sheep and/goats were searched in five electronic databases, including PubMed, Web of Science, Scopus, Embase and ProQuest. After the publications were checked to verify they fit the inclusion criteria, a total of 225 articles were included in the systematic review and meta-analysis, reflecting data from 70 countries/regions. The pooled prevalence was estimated using a random effect meta-analysis model. Overall, the seroprevalence of T. gondii infection was 33.86% (95% CI: 30.47-37.25%) in sheep and 31.78% (95% CI: 28.99-34.58%) in goats, with significant variation in prevalence estimates across geographical locations (p < .001). Substantial heterogeneity (I²  > 75%) was observed in most pooled seroprevalence estimates. The T. gondii infection in global sheep and goat population showed uptrend over the period. This information would be useful for epidemiologist, health authorities and farmers in order to plan future T. gondii survey and infection management strategies both locally and internationally.

High prevalence of anti-Toxoplasma gondii antibodies in beef cattle in Midwestern Brazil

The present study aimed to determine the seroprevalence of anti-Toxoplasma gondii antibodies using an indirect immunofluorescence assay (IFA-IgG) in 3,814 cows aged ≥ 24 months belonging to 353 beef farms in the Mato Grosso state. Additionally, we aimed to identify the possible risk factors associated with seropositivity in Mato Grosso, which encompasses three biomes (Amazon, Cerrado, and Pantanal) of Brazil. Analysis of 3,814 samples observed that 1,307 animals were positive for anti-T. gondii antibodies (IFA-IgG ≥ 64), with an animal-level seroprevalence of 34.27%. Herd-level seroprevalence was 92.07%. In the animal-level model, cows raised in the Amazon and Pantanal biomes and breed studies on European and Zebu or hybrid were found to be at risk for T. gondii seropositivity. Prevalence of anti-T. gondii antibodies in cows destined for human consumption was found to be widely distributed throughout the entire study area. Further studies are required to assess the impact of beef in the possible transmission of toxoplasmosis to humans residing in the region and establish additional control measures for this protozoan mainly on beef herds raised in the Amazon and Pantanal biomes, where the highest values of seroprevalence were observed.

Effective Nanoparticle-Based Nasal Vaccine Against Latent and Congenital Toxoplasmosis in Sheep

Toxoplasma gondii is a parasitic protozoan of worldwide distribution, able to infect all warm-blooded animals, but particularly sheep. Primary infection in pregnant sheep leads to millions of abortions and significant economic losses for the livestock industry. Moreover, infected animals constitute the main parasitic reservoir for humans. Therefore, the development of a One-health vaccine seems the best prevention strategy. Following earlier work, a vaccine constituted of total extract of Toxoplasma gondii proteins (TE) associated with maltodextrin nanoparticles (DGNP) was developed in rodents. In this study we evaluated the ability of this vaccine candidate to protect against latent and congenital toxoplasmosis in sheep. After two immunizations by either intranasal or intradermal route, DGNP/TE vaccine generated specific Th1-cellular immune response, mediated by APC-secretion of IFN-γ and IL-12. Secretion of IL-10 appeared to regulate this Th1 response for intradermally vaccinated sheep but was absent in intranasally-vaccinated animals. Finally, protection against latent toxoplasmosis and transplacental transmission were explored. Intranasal vaccination led to a marked decrease of brain cysts compared with the non-vaccinated group. This DGNP/TE vaccine administered intranasally conferred a high level of protection against latent toxoplasmosis and its transplacental transmission in sheep, highlighting the potential for development of such a vaccine for studies in other species.

Economic and public health importance of Toxoplasma gondii infections in sheep: 2009-2020

Toxoplasma gondii infections are common in humans and animals worldwide. The present review summarizes worldwide information on the prevalence of clinical and subclinical infections, epidemiology, diagnosis, control, and genetic diversity of T. gondii in sheep in the past decade. There is debate and uncertainty concerning repeat congenital infection as evidenced by finding T. gondii DNA in progeny of chronically infected sheep. However, there is no concrete evidence that T. gondii is the cause of repeated abortions in sheep. Recent data concerning pathogenesis of abortion in acutely infected sheep are reviewed. PCR-RFLP typing of T. gondii DNA derived from viable T. gondii isolates or tissues of infected sheep revealed low genetic diversity in sheep in Europe, Africa, Asia and North America but high diversity in South America. This review will be of interest to biologists, parasitologists, veterinarians, and public health workers.

Using lamb sales data to investigate associations between implementation of disease preventive practices and sheep flock performance

Although the UK is the largest lamb meat producer in Europe, there are limited data available on sheep flock performance and on how sheep farmers manage their flocks. The aims of this study were to gather evidence on the types of disease control practices implemented in sheep flocks, and to explore husbandry factors associated with flock productivity. A questionnaire focusing on farm characteristics, general husbandry and flock health management was carried out in 648 farms located in the UK over summer 2016. Abattoir sales data (lamb sales over 12 months) was compared with the number of breeding ewes on farm to estimate flock productivity (number of lambs sold for meat per 100 ewes per farm per year). Results of a multivariable linear regression model, conducted on 615 farms with complete data, indicated that farms vaccinating ewes against abortion and clostridial agents and administering a group 4/5 anthelmintic to ewes (as recommended by the Sustainable Control of Parasites in Sheep Initiative) during quarantining had a greater flock productivity than farms not implementing these actions (P<0.01 and 0.02, respectively). Flocks with maternal breed types had higher productivity indexes compared with flocks with either pure hill or terminal breeds (P<0.01). Farms weighing lambs during lactation had greater productivity than those not weighing (P<0.01). Importantly, these actions were associated with other disease control practices, for example, treating individual lame ewes with an antibiotic injection, weaning lambs between 13 and 15 weeks of age and carrying out faecal egg counts, suggesting that an increase in productivity may be associated with the combined effect of these factors. This study provides new evidence on the positive relationship between sheep flock performance and disease control measures and demonstrates that lamb sales data can be used as a baseline source of information on flock performance and for farm benchmarking. Further research is needed to explore additional drivers of flock performance.

Toxoplasma gondii infection and toxoplasmosis in farm animals: Risk factors and economic impact

The protozoan parasite Toxoplasma gondii is a zoonotic parasite that can be transmitted from animals to humans. Felids, including domestic cats, are definitive hosts that can shed oocysts with their feces. In addition to infections that occur by accidental oral uptake of food or water contaminated with oocysts, it is assumed that a large proportion of affected humans may have become infected by consuming meat or other animal products that contained infective parasitic stages of T. gondii. Since farm animals represent a direct source of infection for humans, but also a possible reservoir for the parasite, it is important to control T. gondii infections in livestock. Moreover, T. gondii may also be pathogenic to livestock where it could be responsible for considerable economic losses in some regions and particular farming systems, e.g. in areas where the small ruminant industry is relevant. This review aims to summarize actual knowledge on the prevalence and effects of infections with T. gondii in the most important livestock species and on the effects of toxoplasmosis on livestock. It also provides an overview on potential risk factors favoring infections of livestock with T. gondii. Knowledge on potential risk factors is prerequisite to implement effective biosecurity measures on farms to prevent T. gondii infections. Risk factors identified by many studies are cat-related, but also those associated with a potential contamination of fodder or water, and with access to a potentially contaminated environment. Published information on the costs T. gondii infections cause in livestock production, is scarce. The most recent peer reviewed reports from Great Britain and Uruguay suggest annual cost of about 5-15 million US $ per country. Since these estimates are outdated, future studies are needed to estimate the present costs due to toxoplasmosis in livestock. Further, the fact that T. gondii infections in livestock may affect human health needs to be considered and the respective costs should also be estimated, but this is beyond the scope of this article.

Large-Scale Epidemiological Study on Toxoplasma gondii Seroprevalence and Risk Factors in Sheep in Estonia: Age, Farm Location, and Breed Associated with Seropositivity

Toxoplasma gondii is a zoonotic parasite of major veterinary and public health importance. The parasite is common in many host species in Estonia, however, information about the seroprevalence in the local sheep population is lacking. We estimated T. gondii seroprevalence and evaluated a limited selection of possible risk factors for T. gondii seropositivity in sheep raised in Estonia. Sera from 1599 sheep from 122 flocks, collected during 2012-2013, were diluted to 1:40 and screened for the presence of anti-T. gondii immunoglobulin G antibodies using a commercial direct agglutination test. The cutoff titer for seropositivity was 40. A total of 667 of the 1599 sheep were T. gondii seropositive, yielding an apparent seroprevalence estimate of 41.71% (95% confidence interval 39.31-44.14). At least one seropositive sheep was detected on the majority (88.53%) of the farms. T. gondii seroprevalence was significantly lower in lambs (age <12 months) than in adults (age ≥12 months) (11.11% and 42.16%, respectively). The seroprevalence increased steeply with age in the first years of life. A multivariable random-effects logistic regression model identified being an adult (odds ratio [OR] 9.55) and being from a farm located on the islands (OR 2.51) as risk factors for T. gondii seropositivity, while being of Texel breed appeared as a protective factor (OR 0.34) when compared with the Estonian Blackhead breed. Exposure to T. gondii was widespread among the investigated sheep. Undercooked meat and unpasteurized milk from sheep from Estonia should be considered possible sources of T. gondii infections to other hosts, including humans.

A first estimate of the structure and density of the populations of pet cats and dogs across Great Britain

Policy development, implementation, and effective contingency response rely on a strong evidence base to ensure success and cost-effectiveness. Where this includes preventing the establishment or spread of zoonotic or veterinary diseases infecting companion cats and dogs, descriptions of the structure and density of the populations of these pets are useful. Similarly, such descriptions may help in supporting diverse fields of study such as; evidence-based veterinary practice, veterinary epidemiology, public health and ecology. As well as maps of where pets are, estimates of how many may rarely, or never, be seen by veterinarians and might not be appropriately managed in the event of a disease outbreak are also important. Unfortunately both sources of evidence are absent from the scientific and regulatory literatures. We make this first estimate of the structure and density of pet populations by using the most recent national population estimates of cats and dogs across Great Britain and subdividing these spatially, and categorically across ownership classes. For the spatial model we used the location and size of veterinary practises across GB to predict the local density of pets, using client travel time to define catchments around practises, and combined this with residential address data to estimate the rate of ownership. For the estimates of pets which may provoke problems in managing a veterinary or zoonotic disease we reviewed the literature and defined a comprehensive suite of ownership classes for cats and dogs, collated estimates of the sub-populations for each ownership class as well as their rates of interaction and produced a coherent scaled description of the structure of the national population. The predicted density of pets varied substantially, with the lowest densities in rural areas, and the highest in the centres of large cities where each species could exceed 2500 animals.km^-2. Conversely, the number of pets per household showed the opposite relationship. Both qualitative and quantitative validation support key assumptions in the model structure and suggest the model is useful at predicting the populations of cats at geographical scales important for decision-making, although it also indicates where further research may improve model performance. In the event of an animal health crisis, it appears that almost all dogs could be brought under control rapidly. For cats, a substantial and unknown number might never be bought under control and would be less likely to receive veterinary support to facilitate surveillance and disease management; we estimate this to be at least 1.5 million cats. In addition, the lack of spare capacity to care for unowned cats in welfare organisations suggests that any increase in their rate of acquisition of cats, or any decrease in the rate of re-homing might provoke problems during a period of crisis.

A prevalence study ofSalmonellaspp.,Yersiniaspp.,Toxoplasma gondiiand porcine reproductive and respiratory syndrome virus in UK pigs at slaughter

An abattoir-based study was undertaken between January and May 2013 to estimate the prevalence ofSalmonellaspp. andYersiniaspp. carriage and seroprevalence of antibodies toToxoplasma gondii andporcine reproductive and respiratory syndrome virus (PRRSv) in UK pigs at slaughter. In total, 626 pigs were sampled at 14 abattoirs that together process 80% of the annual UK pig slaughter throughput. Sampling was weighted by abattoir throughput and sampling dates and pig carcasses were randomly selected. Rectal swabs, blood samples, carcass swabs and the whole caecum, tonsils, heart and tongue were collected.Salmonellaspp. was isolated from 30·5% [95% confidence interval (CI) 26·5–34·6] of caecal content samples but only 9·6% (95% CI 7·3–11·9) of carcass swabs, which was significantly lower than in a UK survey in 2006–2007.S.Typhimurium andS.4,[5],12:i:- were the most commonly isolated serovars, followed byS.Derby andS.Bovismorbificans. The prevalence ofYersinia enterocoliticacarriage in tonsils was 28·7% (95% CI 24·8–32·7) whereas carcass contamination was much lower at 1·8% (95% CI 0·7–2·8). The seroprevalence of antibodies toToxoplasma gondiiand PRRSv was 7·4% (95% CI 5·3–9·5) and 58·3% (95% CI 53·1–63·4), respectively. This study provides a comparison to previous abattoir-based prevalence surveys forSalmonellaandYersinia, and the first UK-wide seroprevalence estimates for antibodies toToxoplasmaand PRRSv in pigs at slaughter.

Prevalence and risk factors for Toxoplasma gondii infection in meat animals and meat products destined for human consumption

Toxoplasma gondii is a protozoan parasite that is responsible for approximately 24% of all estimated deaths attributed to foodborne pathogens in the United States. Human infection results from accidental ingestion of oocysts from the environment, in water, or on insufficiently washed produce or from consumption of raw or undercooked meat products that contain T. gondii tissue cysts. This review focused on studies of T. gondii in meat because many human T. gondii infections are acquired through consumption of raw or undercooked meat. Prevalence of T. gondii is higher in conventionally reared pigs, sheep, and poultry than in cattle and is greater in meat products from organic than from conventionally reared meat animals because of outdoor access, which poses substantially greater opportunities for exposure to infected rodents, wildlife, and oocyst-contaminated feed, water, or environmental surfaces. Risk factors related to T. gondii exposure for livestock include farm type, feed source, presence of cats, methods of rodent and bird control, methods of carcass handling, and water quality. This review serves as a useful resource and information repository for informing quantitative risk assessment studies for T. gondii infection in humans through meat consumption.

Interferon-gamma expression and infectivity of Toxoplasma infected tissues in experimentally infected sheep in comparison with pigs

Livestock animals are a potential risk for transmission of toxoplasmosis to humans. Sheep and pigs still remain an important source because their meat is often eaten undercooked which has been regarded as a major route of infection in many countries. Moreover, porcine tissues are processed in many food products. In the current study, the IFN-gamma (T-helper 1 cells), IL-4 (Th2 cells) and IL-10 mRNA (Treg cells) expression by blood mononuclear cells, and the serum antibody response against Toxoplasma gondii total lysate antigen, recombinant T. gondii GRA1, rGRA7, rMIC3 and rEC2, a chimeric antigen composed of MIC2, MIC3 and SAG1, was studied in sheep the first two months after a T. gondii infection and compared with these responses in pigs. At the end of this period, the parasite distribution in heart, brain and two skeletal muscles in sheep was compared with this in pigs. Whereas the parasite distribution was similar in sheep and pigs, the antibody response differed considerably. In sheep, antibodies appeared against all tested T. gondii antigens, but mainly against rGRA7, rMIC3234307 and TLA whereas in pigs only rGRA7-specific antibodies could be demonstrated. Also, the cytokine response differed. Both in sheep and pigs an IFN-gamma response occurred which seemed to be a slightly more pronounced in sheep. In sheep, also IL-10 and IL-4 mRNA expression showed an increase, but later than IFN-gamma and with more variation. However, in pigs no such increase was seen. As concerning diagnosis, results indicate that serum antibodies against GRA7 in live sheep and pigs and heart tissue for bioassay and qPCR in slaughtered animals are the best targets to demonstrate presence of T. gondii infection.

Toxoplasma gondii in Cattle, Camels and Sheep in Isfahan and Chaharmahal va Bakhtiary Provinces, Iran

BACKGROUND

Toxoplasma gondii is a zoonotic parasite, which is assumed to have cosmopolitan distribution.

OBJECTIVES

Adopting a cross-sectional study design the current research aimed to determine the occurrence of the parasite in cattle, camels and sheep in Isfahan and Chaharmahal va Bakhtiary provinces of Iran.

MATERIALS AND METHODS

Animals in the field and those brought for slaughter at abattoirs were included. Blood samples were randomly collected from animals and investigated by polymerase chain reaction (PCR).

RESULTS

T. gondii infections were detected in 0.00%, 6.60% and 17.9% of the sample cattle (n = 155), camels (n = 122) and sheep (n = 95) respectively. Sheep were more frequently affected in Chaharmahal va Bakhtiary (33.33%) compared to Isfahan (8.47%) (P = 0.005, 95%; CI = 6.88-43.35). No statistically significant difference was observed in infection prevalence between camels and sheep; and between the different sex categories in both camels and sheep.

CONCLUSIONS

Evidence of T. gondii occurrence in sheep and camels was provided in the provinces under study. There is a need to investigate the potential risk factors of zoonotic infections. Furthermore, animal health and production losses caused by the parasite; and associated zoonotic implications in the area under study need to be explored.

Seroprevalence and risk factors for Toxoplasma gondii in sheep in Grosseto district, Tuscany, Italy

Background

Serum samples from 630 milk sheep, in 33 dairy flocks representative of the southern area of the Tuscany region, were tested for the presence of antibodies to Toxoplasma gondii using an indirect immunofluorescence antibody test (IFAT). Questionnaires exploring the management system were completed by the veterinarian in charge of the flocks.

Results

At least one seropositive animal was found in 32 of the 33 flocks tested (97.0%; 95% CI: 84.2%, 99.9%). In the positive flocks, median seroprevalence was 29.4% (interquartile range: 15.9%-46.1%). Overall animal-level seroprevalence, adjusted for sampling weights and test sensitivity and specificity, was 33.3% (95% CI: 24.8%, 42.7%). In a multivariable negative binomial regression model the number of seropositive animals in a flock decreased with increasing flock size (for >400 vs. <300 animals: count ratio (CR) = 0.62; 95% CI: 0.41, 0.95; P = 0.028) and was greater on farms where stray cats had access to animals’ water (CR = 1.54; 95% CI: 1.05, 2.26; P = 0.027).

Conclusions

Small flock size and access of cats to water are potential risk factors for Toxoplasma infection in sheep in the Grosseto district in Tuscany, Italy. Sheep could be an important source of T. gondii infection in humans, since we estimate that between 25% and 43% of sheep in the district were seropositive. Toxoplasmosis is also likely to be an important cause of abortion in sheep in the district. Control and prophylactic measures must be adopted to improve the rearing system and the implementation of health promoting programmes in a joint effort between sheep farmers, farmers’ associations and veterinarians to inform about the means of transmission of the infection and for a better understanding of the disease.