Strain- and dose-dependent reduction of Toxoplasma gondii burden in pigs is associated with interferon-gamma production by CD8+ lymphocytes in a heterologous challenge model

Toxoplasma gondii is a worldwide prevalent parasite of humans and animals. The global infection burden exceeds yearly one million disability-adjusted life years (DALY's) in infected individuals. Therefore, effective preventive measures should be taken to decrease the risk of infection in humans. Although human toxoplasmosis is predominantly foodborne by ingestion of tissue cysts in meat from domestic animals such as pigs, the incidence risk is difficult to estimate due to the lack of screening of animals for infection and insights in location and persistence of the parasite in the tissues. Hence, experimental infections in pigs can provide more information on the risk for zoonosis based on the parasite burden in meat products intended for human consumption and on the immune responses induced by infection. In the present study, homo-and heterologous infection experiments with two distinct T. gondii strains ( IPB-LR and IPB-Gangji) were performed. The humoral and cellular immune responses, the presence of viable parasites and the parasite load in edible meat samples were evaluated. In homologous infection experiments the parasite persistence was clearly strain-dependent and inversely correlated with the infection dose. The results strongly indicate a change in the amount of parasite DNA and viable cysts in porcine tissues over time. Heterologous challenge infections demonstrated that IPB-G strain could considerably reduce the parasite burden in the subsequent IPB-LR infection. A strong, however, not protective humoral response was observed against GRA7 and TLA antigens upon inoculation with both strains. The in vitro IFN-gamma production by TLA-stimulated PBMCs was correlated with the infection dose and predominantly brought about by CD3+ CD4-CD8 alpha bright T-lymphocytes. The described adaptive cellular and humoral immune responses in pigs are in line with the induced or natural infections in mice and humans. Previous studies underscored the heterogeneity of T. gondii strains and the corresponding virulence factors. These findings suggest the potential of the IPB-G strain to elicit a partially protective immune response and to reduce the parasite burden upon a challenge infection. The IPB-G strain could be used as a promising tool in limiting the number of viable parasites in edible tissues and, hence, in lowering the risk for human toxoplasmosis

Epidemiology, impact and control of bovine cysticercosis in Europe : a systematic review

Background: Bovine cysticercosis in Europe has been known for centuries but the data showing the occurrence of this zoonosis are scarce. The aim of this paper is to review and present the current knowledge on bovine cysticercosis in Europe. Methods: We conducted a systematic review of studies published between 1990 and November 2014. Qualitative and quantitative data on prevalence, risk factors, burden and interventions were extracted and analysed. Results: Reports on prevalence were available for 23 European countries, mostly from western and central Europe; for a few of these only data before 1990 were available. Prevalence based on meat inspection was generally low (below 6.2 % in 95 % of the records) and varied between and within countries. Serology and detailed meat inspection provided a higher prevalence range (0.41–14 %). Only few studies analysing risk factors were identified. Reported factors related to access to pastures and risky waters, dairy production and uncontrolled human defecation in the proximity of the farm among others. Only one estimate of the economic impact of the disease could be identified. Recommended interventions were focused on increasing diagnostic tests sensitivity or the application of risk based surveillance strategies. Conclusions: There is a lack of complete and updated data on most countries, especially in eastern Europe. Further risk factor studies might be needed together with estimates on the burden of the disease in all European countries. Risk-based interventions are being encouraged but current data are limited to guide this approach

T. gondii strains and their dosage influence the parasitic load in tissues of experimentally infected pigs

One of the major routes of a Toxoplasma gondii infection in humans is the consumption of raw or undercooked meat. In the present study, we compared the parasitic load induced by 2 different T. gondii strains in the tissues of experimentally infected 6 weeks old pigs. In the first experiment, pigs were orally infected with 3000 tissue cysts of IPB-Gangji strain. The pigs were euthanized 2 and 6 months after infection, and the following samples were tested by bio-assay and qPCR: brain, heart and several skeletal muscles. Two months after infection, all samples tested positive with both tests. Remarkably, after 6 month no cysts were detected in tenderloin and ham, while brain and heart tissue remained infectious. In the second experiment, pigs were infected orally with a low (700 cysts) and a high (6000) dose of T. gondii IPB-Gangji cysts and euthanized after 4 months. The parasitic load was much higher in the low dose group than in the high dose group, as determined by qPCR. In most animals various samples tested negative in both groups, with the exception of the intercostals muscles. Last experiment was repeated with a low and a high dose of the T. gondii IPB-LR strain. Here, all samples remained infectious with no significant difference in parasitic load between both groups. The parasitic load was higher in brain and heart tissue compared to the skeletal muscles. In bio-assay, numerous mice died from the inoculated samples from pigs infected with the IPB-Gangji strain. Ascites and lungs tested T. gondii positive by qPCR. When inoculated with samples from pigs infected with the IPB-LR strain, no mice died from acute T. gondii infection

Why latrines are not used : communities' perceptions and practices regarding latrines in a Taenia solium endemic rural area in Eastern Zambia

Taenia solium cysticercosis is a neglected parasitic zoonosis occurring in many developing countries. Socio-cultural determinants related to its control remain unclear. Studies in Africa have shown that the underuse of sanitary facilities and the widespread occurrence of free-roaming pigs are the major risk factors for porcine cysticercosis. The study objective was to assess the communities' perceptions, practices and knowledge regarding latrines in a T. solium endemic rural area in Eastern Zambia inhabited by the Nsenga ethno-linguistic group, and to identify possible barriers to their construction and use. A total of 21 focus group discussions on latrine use were organized separately with men, women and children, in seven villages of the Petauke district. The themes covered were related to perceived latrine availability (absence-presence, building obstacles) and perceived latrine use (defecation practices, latrine management, socio-cultural constraints). The findings reveal that latrines were not constructed in every household because of the convenient use of existing latrines in the neighborhood. Latrines were perceived to contribute to good hygiene mainly because they prevent pigs from eating human feces. Men expressed reluctance to abandon the open-air defecation practice mainly because of toilet-associated taboos with in-laws and grown-up children of the opposite gender. When reviewing conceptual frameworks of people's approach to sanitation, we found that seeking privacy and taboos hindering latrine use and construction were mainly explained in our study area by the fact that the Nsenga observe a traditionally matrilineal descent. These findings indicate that in this local context latrine promotion messages should not only focus on health benefits in general. Since only men were responsible for building latrines and mostly men preferred open defecation, sanitation programs should also be directed to men and address related sanitary taboos in order to be effective

Taenia solium human cysticercosis : a systematic review of sero-epidemiological data from endemic zones around the world

Background: Taenia solium cysticercosis is a zoonotic neglected disease responsible for severe health disorders such as seizures and death. Understanding the epidemiology of human cysticercosis (HCC) in endemic regions will help to expose critical information about the transmission of the disease, which could be used to design efficient control programs. This review gathered serological data on apparent prevalence of T. solium circulating antigens and/or seroprevalence of T. solium antibodies, apparent prevalence of human taeniasis and risk factors for HCC from endemic communities in order to understand the differences in exposure to the parasite and active infections with T. solium metacestodes in endemic areas around the world. Methods: Three databases were used to search sero-epidemiological data from community-based studies conducted between 1989 and 2014 in cysticercosis endemic communities worldwide. The search focused on data obtained from T. solium circulating antigen detection by monoclonal antibody-based sandwich ELISA and/or T. solium antibody seroprevalence determined by Enzyme-linked Immunoelectrotransfer Blot (EITB). A meta-analysis was performed per continent. Principal Findings: A total of 39,271 participants from 19 countries, described in 37 articles were studied. The estimates for the prevalence of circulating T. solium antigens for Africa, Latin America and Asia were: 7.30% (95% CI [4.23–12.31]), 4.08% (95% CI [2.77–5.95]) and 3.98% (95% CI [2.81–5.61]), respectively. Seroprevalence estimates of T. solium antibodies were 17.37% (95% CI [3.33–56.20]), 13.03% (95% CI [9.95–16.88]) and 15.68% (95% CI [10.25–23.24]) respectively. Taeniasis reported prevalences ranged from 0 (95% CI [0.00–1.62]) to 17.25% (95% CI [14.55–20.23]). Significance: A significant variation in the sero-epidemiological data was observed within each continent, with African countries reporting the highest apparent prevalences of active infections. Intrinsic factors in the human host such as age and immunity were main determinants for the occurrence of infections, while exposure was mostly related to environmental factors which varied from community to community

T. gondii strains and their dosage influence the parasitic load in tissues of experimentally infected pigs

One of the major routes of a Toxoplasma gondii infection in humans is the consumption of raw or undercooked meat. In the present study, we compared the parasitic load induced by 2 different T. gondii strains in the tissues of experimentally infected 6 weeks old pigs. In the first experiment, pigs were orally infected with 3000 tissue cysts of IPB-Gangji strain. The pigs were euthanized 2 and 6 months after infection, and the following samples were tested by bio-assay and qPCR: brain, heart and several skeletal muscles. Two months after infection, all samples tested positive with both tests. Remarkably, after 6 month no cysts were detected in tenderloin and ham, while brain and heart tissue remained infectious. In the second experiment, pigs were infected orally with a low (700 cysts) and a high (6000) dose of T. gondii IPB-Gangji cysts and euthanized after 4 months. The parasitic load was much higher in the low dose group than in the high dose group, as determined by qPCR. In most animals various samples tested negative in both groups, with the exception of the intercostals muscles. Last experiment was repeated with a low and a high dose of the T. gondii IPB-LR strain. Here, all samples remained infectious with no significant difference in parasitic load between both groups. The parasitic load was higher in brain and heart tissue compared to the skeletal muscles. In bio-assay, numerous mice died from the inoculated samples from pigs infected with the IPB-Gangji strain. Ascites and lungs tested T. gondii positive by qPCR. When inoculated with samples from pigs infected with the IPB-LR strain, no mice died from acute T. gondii infection

Early intestinal infection kinetics and immune responses to Toxoplasma gondii in pigs

Toxoplasma gondii is an obligate intracellular parasite, able to infect all homeothermic animals mostly through ingestion of food or drinks contaminated with tissue cysts or oocysts. Recently, we showed a T. gondii strain-specific clearance from tissues upon infection in pigs. While the swine-adapted LR strain persisted in muscle tissues, the human-adapted Gangji strain was cleared from these tissues. We hypothesized that intestinal immune responses short after infection might play a role in this strain-specific clearance. To assess this possibility, the parasite load in duodenal, jejunal and ileal lymph node cells and blood immune cells (PBMCs) as well as the IFNγ secretion by these cells were evaluated at 2, 4, 8, 14 and 28 days post oral inoculation of pigs with both strains. Interestingly, at day 4 post inoculation with the LR strain the parasite was only detected by qPCR in the duodenal lymph node cells, while in the jejunal and ileal lymph node cells and PBMCs the parasite was detected from day 8 post inoculation onwards. Although we observed a similar profile upon inoculation with the Gangji strain, the parasite load in the examined cells was much lower. This was reflected in a significantly higher T. gondii-specific serum IgG response in LR than Gangji infected pigs at day 28 post inoculation. Unexpectedly, this was not reflected in the IFNγ secretion upon re-stimulation of the cells. However, the recall test most likely does not pick up the IFNγ production by innate immune cells, which might have been more important for clearance. In conclusion, our results show that T. gondii first enters the host at the duodenum and then probably disseminates from this site to the other host tissues

QuilA-adjuvanted T. gondii lysate antigens trigger robust antibody and IFNγ+ T cell responses in pigs leading to reduction in parasite DNA in tissues upon challenge infection

Toxoplasma gondii is an intracellular parasite of all mammals and birds, responsible for toxoplasmosis. In healthy individuals T. gondii infections mostly remain asymptomatic, however this parasite causes severe morbidity and mortality in immunocompromised patients and congenital toxoplasmosis in pregnant women. The consumption of raw or undercooked pork is considered as an important risk factor to develop toxoplasmosis in humans. Since effective therapeutic interventions to treat toxoplasmosis are scarce, vaccination of meat producing animals may prevent T. gondii transmission to humans. Here, we evaluated the elicited immune responses and the efficacy of a potential vaccine candidate, generated by size fractionation of T. gondii lysate proteins, to reduce the parasite burden in tissues from experimentally T. gondii infected pigs as compared to vaccination with total lysate antigens (TLA). Our results show that both the vaccine candidate and the TLA immunization elicited strong serum IgG responses and elevated percentages of CD4+CD8+IFNγ+ T cells in T. gondii infected pigs. However, the TLA vaccine induced the strongest immune response and reduced the parasite DNA load below the detection limit in brain and skeletal muscle tissue in most animals. These findings might inform the development of novel vaccines to prevent T. gondii infections in livestock species and humans