Involvement of Toxoplasma gondii in reproductive disorders in Swiss pig farms

Molecular survey of Toxoplasma gondii B1 gene in pigs from various localities in Korea

Toxoplasma gondii, a common protozoan parasite, poses significant public health risks due to its potential to cause toxoplasmosis in humans and can be contracted from pigs, which are considered its critical intermediate host. The aim of this study is to evaluate the prevalence of T. gondii in slaughtered pigs for human consumption, emphasizing the zoonotic implications and the need for improved biosecurity and monitoring practices in pig farming. A total of 1,526 pig samples (1,051 whole blood samples and 384 lung tissue samples from the local slaughterhouse and 91 aborted fetus samples from local farms) were collected throughout the whole country of Korea in 2020. Among them, 6 (0.4%) were found to be infected with T. gondii by nested PCR. When compared by sample type, the prevalence of T. gondii was significantly higher in the aborted fetus samples (2.2%, 2/91) than in the blood (0.3%, 3/1,051) and lung tissue samples (0.3%, 1/384). The B1 gene sequence of T. gondii was similar (97.9-99.8%) to that of the other T. gondii isolates. This study represents the first molecular genotyping survey of T. gondii in the lung tissue of fattening pigs and aborted fetuses in Korea. Our findings indicated the importance of adopting preventive measures including the implementation of rigorous farm hygiene protocols and the promotion of public awareness about the risks of consuming undercooked pork. By addressing the gaps in current control strategies and encouraging the One Health approach, this study contributes to the development of more effective strategies to mitigate the transmission of T. gondii from pigs to humans, ultimately safeguarding public health.

Toxoplasma gondii infection in pig intended for human consumption: seroprevalence, risk factors and influence of biosecurity measures

A serologic and epidemiologic study was carried out in order to determinate herd and animal seroprevalence and associated factors for Toxoplasma gondii in commercial pigs from Espírito Santo state, Brazil. Blood samples were collected from 416 pigs from 55 producer farms in 27 municipalities. An indirect immunofluorescent assay (IFA) was performed to estimate the seroprevalence of T. gondii and identify the associated risk factors using a questionnaire. The T. gondii antibody prevalence rate in commercial swine herds was 15.4% (64/416) using a cutoff of 1:64. The seropositivity for T. gondii was related to the presence of cats, water origin and age of swine in the increase of seroprevalence, and the existence of internal isolation fences and use of composting chambers as protective factors. To the best of our knowledge, this is the first study to report anti- T. gondii antibodies in the serum of pigs in the state of Espírito Santo, Brazil. This finding is important to public health because seropositive pigs can harbor tissue cysts in their meat, thereby representing a zoonotic risk for consumers of raw or undercooked porcine meat or its products.

Detection of Toxoplasma gondii-specific antibodies in pigs using an oral fluid-based commercial ELISA: Advantages and limitations

Toxoplasma gondii is a major food-borne parasite and undercooked meat of infected pigs represents an important source of infection for humans. Since infections in pigs are mostly subclinical, adequate diagnostic tests for use at the farm level are pursued. Oral fluid (OF) was shown to be a promising matrix for direct and indirect detection of infections with various pathogens in pigs. The objective of this study was to assess whether T. gondii infections in pigs could be diagnosed using an indirect ELISA kit adapted for OF samples (OF-ELISA). Routine serology and OF-immunoblot (IB) were used as standards for the comparison. For this, serial OF samples from sows (n = 8) and fatteners (n = 3) experimentally inoculated with T. gondii oocysts, individual field samples from potentially exposed sows (n = 9) and pooled OF samples from potentially exposed group-housed fatteners (n = 195 pig groups, including 2,248 animals) were analysed for antibodies against T. gondii by ELISA. For individual animals, OF-ELISA exhibited a relative diagnostic specificity of 97.3% and a relative diagnostic sensitivity of 78.8%. In experimentally infected animals, positive OF-ELISA results were observed from 1.5 weeks post inoculation (pi) until the end of the experimental setup (8 to 30 weeks pi); however, values below the estimated cut-off were occasionally observed in some animals despite constant seropositivity. In potentially exposed individual animals, OF- and serum-ELISA results showed 100% agreement. In group-housed fatteners, antibodies against T. gondii could be reliably detected by OF-ELISA in groups in which at least 25% of the animals were seropositive. This OF-ELISA, based on a commercially available serum-ELISA, may represent an interesting non-invasive screening tool for detecting pig groups with a high exposure to T. gondii at the farm level. The OF-ELISA may need further adjustments to consistently detect individual infected pigs, probably due to variations in OF antibody concentration over time.

Archetypal type II and III Toxoplasma gondii oocysts induce different immune responses and clinical outcomes in experimentally infected piglets

Livestock animals, such as swine, are an important source of Toxoplasma gondii in the human population. Currently, there is limited knowledge regarding the potential influence that the T. gondii genotype might exert on establishing infection in swine. Herein, we investigated the role of 2 T. gondii isolates, type II and III, representative of the genotypes circulating in Europe, in the immune responses and infection dynamics in piglets. Recently obtained oocysts (10³) from the T. gondii field isolates TgShSp1 (type II, ToxoDB genotype #3) and TgShSp24 (type III, #2) were used for oral infection. Thirteen 50-day-old female piglets of the Landrace-Large White crossbreed were randomly allocated into three different groups: Group 1 (G1, n=5), inoculated with TgShSp1; Group 2 (G2, n=5), inoculated with TgShSp24; and Group 3 (G3, n=3), a non-infected control group. Clinical signs were monitored daily until 42 days post-infection (dpi) when piglets were euthanized. Blood samples were collected weekly to test the cellular immune response in parasite-stimulated peripheral blood and specific IgG, IgG1 and IgG2, responses in sera. Parasite distribution and burden were evaluated in target tissues using a mouse bioassay and quantitative RT−PCR (qPCR). Apathy and a moderate decrease in feed consumption were observed in G1 and G2 piglets between 5 and 8 dpi, coinciding with fever (>40°C). G2 piglets had higher temperatures for a longer duration. Using mouse bioassay and qPCR, the detection frequency was higher in G2 vs. G1, and the highest parasite burdens in target tissues were also found in G2. Seroconversion was detected at 14 dpi in both infected groups, but higher antibody levels were observed in G2 piglets. Cytokine analyses revealed the production of IL-8, IL-1β and IFN-ɤ from 7 dpi in both infected groups. Moreover, IL-12 was produced from 7 dpi in G1 and from 14 dpi in G2. Levels of IL-8 were higher in G2, but IL-1β, IL-12 and IFN-ɤ were higher in G1 at 14 dpi. This cytokine profile reveals a predominant proinflammatory response that could be involved in limiting T. gondii infection in piglets, although it is more efficient against TgShSp1 type II-driven infection.

Investigation of Toxoplasma infection in zoo animals using multispecies ELISA and GRA7 nested PCR

Background

Toxoplasma is an obligate intracellular protozoan that causes an important zoonotic disease with a worldwide distribution. Felids are the definitive hosts of this parasite, while virtually all warm-blooded animals, including birds, serve as intermediate hosts. Four ring-tailed lemurs (Lemur catta) in the Taipei Zoo died of acute Toxoplasma infection in June 2019. Since then, Toxoplasma has occasionally been identified in this Zoo during necropsy of dead animals and PCR of animal blood samples. Therefore, a general survey of Toxoplasma infection in animals in the Zoo seems to be needed.

Methods and results

An indirect multispecies ELISA was used for the first time to screen for Toxoplasma infection in 326 serum samples collected from 75 species of animals. The infection rate of Toxoplasma was 27% (88/326). A commercial latex agglutination (LAT) assay was used to re-examine the samples with doubtful and uncertain ELISA results (151 samples from 42 species). The infection rate increased to 36.2% (118/326), and the indirect multispecies ELISA appeared to be applicable to 31 of 75 species animals included in this study. Nested PCR assays targeting the dense granule protein 7 (GRA7) gene and B1 gene were also used to detect Toxoplasma in DNA samples extracted from 10 liver or blood specimens from 8 animals. GRA7 gene fragments were amplified from 8 samples from 7 animals, while B1 gene fragments were amplified from only 4 samples from 4 animals. From the B1 nested PCR and the sequence data of GRA7 fragments amplified from infectious specimens, the animals in the Zoo were speculated to have been infected by at least three different Toxoplasma variants.

Conclusions

According to the serological investigation, we speculated that over one-third (36.2%) of animals in Taipei Zoo presented the infection of Toxoplasma, and the indirect multispecies ELISA we used can be applied to detect Toxoplasma infection in 31 animal species included in this study. Sequence analysis revealed that at least three Toxoplasma variants were infecting the animals of Taipei Zoo.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03425-y.

Risk factors associated with Toxoplasma gondii seroprevalence in domestic pig farms in Argentina

Toxoplasmosis is a worldwide parasitic zoonosis caused by Toxoplasma gondii. Pigs can become infected by consuming water or food contaminated with sporulated oocysts, or by carnivorism (like the consumption of infected rodents). In pigs most infections are asymptomatic. In certain countries, pig meat containing tissue cysts is a major source of infection for human beings. The aims of this study were to estimate the seroprevalence of toxoplasmosis and to identify which factors were related with the increase of the risk of infection in Argentina. The seroprevalence of T. gondii was determined in 240 pigs from 27 farms in the central-western area of Buenos Aires province, Argentina. Serum samples were analyzed using indirect fluorescent antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA) techniques. Prevalence determined was 53.33% and 32.08% by IFAT and ELISA, respectively. Results showed that 81.5% (22/27) of the farms were seropositive to T. gondii. Seropositivity for T. gondii was related with the following risk factors (p value ≤0.05): presence of felids and rodents in the farms, feeding with waste of human food and storage of food outdoors with free access to felids and to the reservoirs when applying both serological techniques. Our results strongly suggest that the risk of infection with T. gondii in pigs is related to the outdoor/extensive type of production system with low infrastructure conditions, which allows both felids and rodents to have free access to pigs and stored food. Also, the high seroprevalence detected in the present study could indicate a potential role of pork in human infections in the region.

Unifying Virulence Evaluation in Toxoplasma gondii: A Timely Task

Toxoplasma gondii, a major zoonotic pathogen, possess a significant genetic and phenotypic diversity that have been proposed to be responsible for the variation in clinical outcomes, mainly related to reproductive failure and ocular and neurological signs. Different T. gondii haplogroups showed strong phenotypic differences in laboratory mouse infections, which provide a suitable model for mimicking acute and chronic infections. In addition, it has been observed that degrees of virulence might be related to the physiological status of the host and its genetic background. Currently, mortality rate (lethality) in outbred laboratory mice is the most significant phenotypic marker, which has been well defined for the three archetypal clonal types (I, II and III) of T. gondii; nevertheless, such a trait seems to be insufficient to discriminate between different degrees of virulence of field isolates. Many other non-lethal parameters, observed both in in vivo and in vitro experimental models, have been suggested as highly informative, yielding promising discriminatory power. Although intra-genotype variations have been observed in phenotypic characteristics, there is no clear picture of the phenotypes circulating worldwide; therefore, a global overview of T. gondii strain mortality in mice is presented here. Molecular characterization has been normalized to some extent, but this is not the case for the phenotypic characterization and definition of virulence. The present paper proposes a baseline (minimum required information) for the phenotypic characterization of T. gondii virulence and intends to highlight the needs for consistent methods when a panel of T. gondii isolates is evaluated for virulence.

Toxoplasma gondii Infection in Swine: Implications for Public Health

Toxoplasmosis, due to Toxoplasma gondii, is a parasitic disease with global importance. Among livestock, chronic T. gondii infection has been reported in higher rates in pigs and small ruminants, but with subclinical infections in case commonly encountered in pigs. Seroprevalence in the global pig population ranges according to the age or species of pigs, geographical distribution, production programs, and systems. Generally, T. gondii infections are noticed in low prevalence rates in conventional pig farms with high hygiene standards. In contrast, higher prevalence is common on free-ranging farms, outdoor or backyard small pig fams, as well as in farmed or hunted wild boars. The T. gondii average worldwide seroprevalence in pigs is reported to be 13% in Europe, 21% in Africa, 25% in North America, 21% in Asia, and 23% in South America. Human toxoplasmosis outbreaks have been correlated with the consumption of raw or undercooked meat, especially from infected pigs or wild boars, as well as of contaminated drinking water. The risk of infection in processed pork products is lower compared with fresh pork, as meat processing can reduce or inactivate T. gondii tissue cysts. Hence, the prevalence of T. gondii in the pig population may be a useful indicator of the risk of human toxoplasmosis associated with the consumption of pork products. The lack of obligatory screening methods at farm level for the detection of antibodies in farmed animals or the viable T. gondii in carcasses at slaughterhouse level increases the risk of contaminated pork or meat products. For this reason, the application of biosecurity and surveillance programs at farm level is very important to prevent a T. gondii infection.

A longitudinal study of Toxoplasma gondii seroconversion on four large Danish sow farms

Serological tests are routinely used to detect Toxoplasma gondii specific IgG antibodies in serum. Serological surveys of T. gondii show a medium to high prevalence in Danish indoor sows at the time of slaughter. However, little is known about when sows acquire T. gondii, and for how long they remain seropositive. Our focus was on quantifying the incidence rates in different age-cohorts and on investigating the T. gondii IgG antibody dynamics in sows. Four large Danish sow farms were longitudinally surveyed for 1 year. A total of 320 animals from 6, 12, 18, and 24-months age-cohorts were sampled at 5-week intervals. In total, 2989 plasma samples were tested using commercial enzyme linked immunosorbent assay (ELISA). The incidence rate in each of the four age-cohorts was calculated, and a time-to-event analysis was applied to the interval censored data to investigate the relationship between age and probability of T. gondii seroconversion. In the initial ELISA testing, eight sows tested positive for T. gondii at first survey, of which seven remained seropositive throughout the follow-up period. Additionally, 16 sows seroconverted, but only five of these remained seropositive. Weekly incidence rates in the 6, 12, 18, and 24-month age-cohorts were 0.0017 (95% CI = 0.0008 - 0.0037), 0.0009 (95% CI = 0.0003 - 0.0027), 0.0003 (95% CI = 0.0000 - 0.0018), and 0.0023 (95% CI = 0.0010 - 0.0051), respectively. Time-to-event analysis suggested that the incidence rate increased with age but could not conclude this definitively. The retesting of a subsample of the sows (n = 200) with the same ELISA and with modified direct agglutination test (MAT), and western blot (WB) assays suggested that 12 out of the 24 initial ELISA seropositive sows may have been false positive. These 12 sows also showed fluctuating antibody dynamics in ELISA. Hence, the unstable antibody dynamics in ELISA may pose a challenge for serological surveys of T. gondii in sows.

All about Toxoplasma gondii infections in pigs: 2009-2020

Toxoplasma gondii infections are common in humans and animals worldwide. Toxoplasma gondii infection in pigs continues to be of public health concern. Pigs are important for the economy of many countries, particularly, USA, China, and European countries. Among the many food animals, pigs are considered the most important for T. gondii transmission in USA and China because viable parasites have rarely been isolated from beef or indoor raised chickens. Besides public health issues, T. gondii causes outbreaks of clinical toxoplasmosis in pigs in China, associated with a unique genotype of T. gondii (ToxoDB genotype #9 or Chinese 1), rarely found in other countries. The safety of ready to eat pork products with respect to T. gondii infection is a matter of recent debate. Here, we review in detail seroprevalence, prevalence of viable and nonviable T. gondii, epidemiology, risk assessment, diagnosis, and curing of pork products containing T. gondii for the past decade. This review will be of interest to biologists, parasitologists, veterinarians, and public health workers.

Detection of antibodies to Toxoplasma gondii in oral fluid from pigs

Toxoplasma gondii-infected pigs play a major role as a source of infection for humans and detection of high-risk herds is essential to implement control measures at the farm level. The aim of this study was to determine whether oral fluid (OF) could be used as a matrix to detect antibodies against T. gondii in infected pigs by immunoblot (IB). For this, OF from experimentally inoculated sows (n = 8) (serial samples) and naturally exposed group-housed fatteners (n = 42 groups, one sample/group) were analysed for IgG and IgA against T. gondii-SAG1 antigen by IB. Simultaneously, each animal was serologically tested for anti-T. gondii IgG by ELISA. Specific IgG was detected in the sera of all inoculated sows from 2 to 3 weeks post inoculation (pi) and in 3.4 to 92% of the pigs in 13 out of 42 groups. Experimentally inoculated sows showed positive OF-IB results for IgA (100%) and IgG (87.5%) at 1.5 weeks pi and continued yielding positive results for IgA (87.5-75%) and IgG (50%) until 4 weeks pi; however, from 8 weeks pi the frequency of detection of both isotypes was lower, despite constantly positive IgG values in serum-ELISA. Interestingly, consecutive daily samplings for 4 days at 13 and 30 weeks pi showed inconsistent results for some sows, showing that the antibody concentration in OF is prone to timely variations. Pooled OF from groups with 91 and 92% of seropositive pigs yielded positive IB results for IgG and IgA. Fattener groups with ≤13% of seropositive pigs gave negative IB results to both isotypes. Our results showed that antibodies to T. gondii can be detected in OF from infected pigs, and that IgA seems to be a more adequate target than IgG. Although OF does not seem to be a robust matrix to assess the serological status for T. gondii in individual animals, this diagnostic approach represents an interesting non-invasive, low-cost and animal welfare friendly option as a screening method at the farm level to determine high exposure to T. gondii in the herd.

Does Neospora caninum cause reproductive problems in pigs?

Neospora caninum is known to cause reproductive disturbances in several animal species, such as cattle, sheep, and goats. However, research on the effects of N. caninum on reproduction in pigs is limited. The objective of this study was to verify the transplacental transmission of N. caninum in pigs during several gestational stages. Twelve healthy Toxoplasma gondii and N. caninum seronegative female pigs were selected and separated into four groups of three animals each. Group A was maintained as a control group. Groups B, C, and D were inoculated intravenously with 2.9 × 10⁷ tachyzoites of the N. caninum strain Nc1, 30 days before conception and at 45 and 90 days of gestation, respectively. Blood samples were collected from females periodically through IFAT for IgG and IgM screening to confirm the infection. At birth, after blood samples were collected from the piglets, they were then euthanized for the collection of the brain, heart, lung, liver, and diaphragm, which were then subjected to PCR. All inoculated gilts seroconverted (IgG) from the seventh day after inoculation. Nine of the 12 females expelled 24 mummified fetuses at the time of delivery, two in group A (eight), two in group B (four), three in group C (nine), and two in group D (three). Of the 24 mummified fetuses, nine were positive for N. caninum (one (25%) fetus of group B, seven (77.8%) of group C, and one (33.3%) of group D). A total of 126 live piglets were born. When the organs of the piglets from the inoculated females were analyzed by PCR for N. caninum, 88 (93.61%) were positive. All gilts inoculated produced at least one positive piglet. This demonstrates that there is transplacental transmission of N. caninum in all phases of gestation, regardless of the time of infection.

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.

An updated literature review on maternal-fetal and reproductive disorders of Toxoplasma gondii infection

BACKGROUND

Toxoplasma gondii infection is one of the most prevalent infectious disease with worldwide distribution. Congenital toxoplasmosis is annually responsible for 1.20 million disability-adjusted life years around the world, but often it is overlooked many countries.

METHODS

We performed an updated review to summarize the current researches on fetal, neonatal and maternal consequences of T. gondii infection and also adverse effects of toxoplasmosis on women reproductive organs.

RESULTS

T. gondii infection could be cause of several abnormalities from hydrocephalus, microcephaly, deafness, abortion and still birth in fetal to psychomotor retardation, intellectual disability, hearing loss, slower postnatal motor development during the first year of life; and chorioretinitis, cryptogenic epilepsy and autism spectrum disorders in newborns. Moreover, this infection is related with neuropsychiatric disorders such as anxiety, schizophrenia spectrum disorders, depression, decreased weight, autoimmune thyroid diseases, self-directed violence, violent suicide attempts in mothers. This literature review emphasized that toxoplasmosis could be an important neglected factor endometritis, ovarian dysfunction, impaired folliculogenesis, ovarian and uterine atrophy, decrease in reproductive organs weight and reproductive performance in women. We reviewed role of the immunological profile such as pro-infiammatory cytokines and hormonal changes as main potential mechanisms related to this infection and development of maternal-fetal and reproductive disorders.

CONCLUSION

T. gondii is associated with several brain related disorders in both mothers and newborns, and also it is cause of several abnormalities in reproductive organs. Early diagnosis and treatment of the infection could be effective to significantly improve the clinical outcome.

Detection of Toxoplasma gondii in cat's internal organs by immunohistochemistry methods labeled with-[strept] avidin-biotin

AIM

The aims of the study are to detect the presence of Toxoplasma gondii antigen and to determine its distribution location in several organs of domestic cat using immunohistochemistry (IHC) method with Labeled-[Strept] Avidin-Biotin (LAB-SA).

MATERIAL AND METHODS

Four domestic cats aged 1-2 years were used as sample in this research. The sample divided into two groups with two cats each. Cats in Group I were positive Toxoplasma based on serologically screening test, while cats in Group II were orally infected with 1×106Toxoplasmaoocyst. All samples then necropsied, and the organs including brain, liver, kidney, duodenum, jejunum, ileum, lungs, and spleen were collected for IHC method with LAB-SA.

RESULT

The result showed that Toxoplasma antigens were detected in ileum of both serologically positive domestic cat and the experimentally infected cats. Toxoplasma was also observed in kidney of serologically positive domestic cat. In the serologically positive domestic cat, necrotic lesions were found on ileum, kidney, and liver, whereas in experimentally infected cat, the lesion was only found on ileum.

CONCLUSION

The presence of Toxoplasma antigen is successfully detected in several organs of domestic cat using IHC method with the LAB-SA.

Experimental Toxoplasma gondii infections in pigs: Humoral immune response, estimation of specific IgG avidity and the challenges of reproducing vertical transmission in sows

Ten pregnant sows were experimentally inoculated per os with T. gondii in order to investigate vertical and galactogenic transmission of the parasite and the evolution and maturation of the specific IgG humoral response in the sows and piglets. Five seronegative sows received 10⁴T. gondii (CZ isolate clone H3) sporulated oocysts during late-pregnancy (Exp. 1), three sows received 10⁴ oocysts during mid-pregnancy (Exp. 2) and three sows from Exp. 1 (and two seronegative sows) were re-inoculated with 10⁵ oocysts during a further pregnancy (late-pregnancy) (Exp. 3). Besides, six 4.5 week-old piglets inoculated per os with 5×10³ oocysts were also included in the serological investigations. All animals seroconverted (PrioCHECK Toxoplasma Ab porcine ELISA, Prionics, Switzerland) by 2-3 weeks post inoculation (wpi) and remained seropositive for at least 38 weeks or until euthanasia. Four chronically infected sows from Exp. 1 and 2 were serologically monitored during a further pregnancy and no reactivation, but a decrease of the antibody levels was observed at farrowing (Exp. 4). In all experiments, the specific IgG-avidity was initially low, increased during the course of infection and after re-inoculations. An avidity index (AI) ≥40% could be used to rule out recent infections (<8 weeks) in most (15 of 16) animals. In some piglets (18.6% of 70) delivered by inoculated sows (Exp. 1 and 2), maternal antibodies were still detectable at 2 months (but not by 3 months) of age, with constant high avidity values, comparable to those of the dams at farrowing. In all experiments, the sows remained asymptomatic and delivered non-infected offspring at term. A total of 208 normal and 5 stillborn piglets delivered by the inoculated sows (Exp. 1-4) tested serologically negative before colostrum uptake. Placentas (n=88) from all sows and tissues (brain, liver, lung, heart, and masseter muscle) from 56 delivered piglets were analysed histopathologically and by real-time PCR for T. gondii with negative results. Colostrum and milk samples from all sows were negative by real-time PCR for T. gondii DNA. In addition, no seroconversion was observed in 16 piglets from seronegative dams that were transferred to infected dams one day after birth to detect a possible infection through colostrum or milk during the suckling period. Although vertical transmission of T. gondii was demonstrated in naturally infected pigs, many factors involved in the outcome of vertical transmission and congenital toxoplasmosis in pigs are still unknown.

Risk factors associated with the different categories of piglet perinatal mortality in French farms

We aimed to identify mortality patterns and to establish risk factors associated with different categories of piglet perinatal mortality in French farms. At farm level, the analyses were performed on data from 146 farms that experienced perinatal mortality problems. At piglet level, the analyses were performed on data from 155 farms (7761 piglets). All data were collected over a period of 10 years (2004-14) by a consulting company, using a non-probability sampling at farm level and a random sampling at sow level. Six main categories of mortality, determined by standardised necropsy procedure, represented 84.5% of all the perinatal deaths recorded. These six categories were, in order of significance: Death during farrowing, Non- viable, Early sepsis, Mummified, Crushing and Starvation. At farm level, the percentage of deaths due to starvation was positively correlated to the percentage of deaths due to crushing and the percentage of deaths during farrowing (r>0.30, P<0.05) .The percentage of deaths due to crushing was negatively correlated to the percentage of deaths due to early sepsis (r<-0.30, P<0.05) and positively correlated to the deaths due to acute disease (r>0.30, P<0.05). Patterns of perinatal mortality at farm level were identified using a principal component analysis. Based on these, the farms could be classified, using ascending hierarchical classification, into three different clusters, highlighting issues that underlie farm differences. Risk factors were compared at piglet level for the different categories of death. Compared to other categories of death, deaths during farrowing were significantly fewer during the night than during the day. Compared to other categories of death, the likelihood of non-viable piglets tended to be higher in summer than other seasons. A smaller number of deaths in the litter was also identified for the piglets classified as non-viable or mummified. For the six main categories of perinatal mortality, the piglets which died from a specific category tended to have more littermates which died from the same category. Parity and litter size also had more significant effects on certain categories of death compared to others. The study provides novel information on the risk factors associated with specific categories of piglet perinatal mortality. The classification of farms into the 3 different clusters could lead to a more targeted management of perinatal mortality on individual farms.

Toxoplasma gondii: Pig seroprevalence, associated risk factors and viability in fresh pork meat

This study was conducted on 161 fattening pig farms located in Aragón (Northeast Spain). Serum samples from 1200 pigs were tested for antibodies against T. gondii by indirect immunofluorescence assay (IFA). Antibodies to T. gondii (≥1:20) were detected in 301 pigs (24.52%). The seroprevalence observed in the present study indicates a widespread exposure to T. gondii, as seropositive pigs were found in 96.67% of the farms studied although low pig titers were determined. Risk factors associated with T. gondii seroprevalence were presence of cats in or around the farms, presence of dogs around the facilities, low number of animals in the farms, poor hygiene and bad maintenance of the farms. Finally, it was observed that where rodent baits were used, Toxoplasma prevalence was lower. Risk management measures including control of cats and rodents on the farms, among others, could help to reduce the observed prevalence levels. By mouse bioassay, T. gondii was detected in 73.7% and isolated from 42.1% of seropositive pigs and a significant relation between the titers of pigs and the presence and viability of T. gondii in the tissues was found. The detection of T. gondii is not possible by currently practiced meat inspection. Nevertheless, the increased probability of detecting viable forms of T. gondii in tissues of pigs with titers ≥1: 80 could be used as the cutoff for discriminating higher risk animals, and could be used as an effective control tool for the industry of cured meat products. In practical terms, we propose that this value could be used as a critical limit in the HACCP system.