Prevalence, Genetic Diversity, Tissue Distribution, and Risk Factors Contributing to T. gondii Burden in Domestic Pigs

Toxoplasma gondii is an obligatory intracellular parasite of mammals, including humans and domestic animals. The infection with this parasite has severe clinical consequences, as it causes abortion or fetal abnormalities, encephalitis in immunocompromised humans, ocular toxoplasmosis with chorioretinitis, and it may contribute to Alzheimer disease. Therefore, an efficient control of T. gondii by prevention of the transmission to humans is strongly recommended. Pork is considered as an important source of toxoplasmosis, due to the frequent consumption of the raw or undercooked porcine meat products, a high susceptibility of pigs to the infection, and because of the numerous risk factors, contributing to the prevalence of toxoplasmosis in the pig population. The cellular and humoral immune responses, such as IgM, IgG, IFN‐gamma, and interleukin‐10 or ‐12 production, associated with the acute and chronic infection in pigs, do not prevent development of the tissue cysts, which persist lifelong within the intermediate host. Therefore, the prevalence of T. gondii in the pig population might be an useful indication of the risk associated with the consumption of the porcine meat

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

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

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

Idiopathische eosinofiele bronchopneumonie bij een cavalier king charles spaniël: een casereport en differentiaaldiagnose met Pneumocystis carinii infectie

The present case describes a dog with eosinophilic bronchopneumonia. The dog was presented with a history of coughing and dyspnea at the Department of Small Animal Medicine, Faculty of Veterinary Medicine, Ghent University. A presumptive diagnosis of Pneumocystic carinii was made based on signalment, history, clinical examination, blood work and medical imaging, and the dog was treated with trimethoprim-sulfadiazine. Because of lack of improvement, a bronchoalveolar lavage was performed and the serum IgG and IgM concentrations were determined. Cytology of bronchoalveolar lavage showed an excessive amount of eosinophils. The IgG was within normal limits and the IgM was increased. These findings excluded pneumocystosis as a possible cause, and the definitive diagnosis of eosinophilic bronchopneumonia was made. Prednisolone was added to the treatment. The dog was sent home with a treatment of trimethoprim-sulfadiazine and prednisolone gradually diminished. On control, six weeks later, the dog only coughed occasionally, and another three months later it was free of coughing

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

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

Toxoplasma gondiiis an obligate intracellular parasite, able to infect all homeothermicanimals mostly through ingestion of (oo)cysts contaminated food or water. Recently,we observed aT. gondiistrain-specific clearance from tissues upon infection in pigs:while the swine-adapted LR strain persisted in porcine tissues, a subsequent infectionwith the human-isolated Gangji strain cleared parasites from several tissues. Wehypothesized that intestinal immune responses shortly after infection might play a rolein this strain-specific clearance. To assess this possibility, the parasite load in smallintestinal lymph node cells and blood immune cells as well asthe IFNγsecretion bythese cells were evaluated at 2, 4, 8, 14, and 28 days post oralinoculation of pigs withtissue cysts of both strains. Interestingly, at day 4 post inoculation with the LR strainthe parasite was detected by qPCR only in the duodenal lymph node cells, while in thejejunal and ileal lymph node cells and PBMCs the parasite wasdetected from day 8post inoculation onwards. Although we observed a similar profile upon inoculation withthe Gangji strain, the parasite load in the examined cells was much lower. This wasreflected in a significantly higherT. gondii-specific serum IgG response in LR comparedto Gangji infected pigs at day 28 post inoculation. Unexpectedly, this was not reflected inthe IFNγsecretion upon re-stimulation of the cells where almost equal IFNγsecretion wasobserved in both groups. In conclusion, our results show thatT. gondiifirst enters thehost at the duodenum and then probably disseminates from this site to the other tissues.How the early immune response influences the clearance of parasite from tissues needsfurther study