Does Neospora caninum cause reproductive problems in pigs?

Serological survey of antibodies against Toxoplasma gondii and Neospora caninum in pigs from various regions of Poland

BACKGROUND

Pigs are prone to infections with several protozoa species. Although infection with Toxoplasma gondii rarely results in clinical symptoms in pigs, consuming pork-containing cysts represents a potential threat to human health, especially in immunocompromised individuals, pregnant women, and fetuses. It is estimated that around 2 billion people are infected with Toxoplasma gondii worldwide, making toxoplasmosis one of the most damaging zoonoses. Due to the coincidence of several factors, the meat from infected pigs can, however, frequently reach the consumer. In cattle, infection with Neospora caninum can cause considerable economic losses. The consequences of this infection for pigs remain unclear. However, infection in sows was linked with the development of some clinical signs, and transplacental transmission of the parasite was observed. Therefore, it should be considered a potential threat to pigs' health. Due to the above reasons, the data regarding the epidemiology of the mentioned parasites seems desirable. Since Poland represents one of the major pig producers in the European Union, and pork is the most commonly consumed type of meat, the present study aimed to determine the seroprevalence of Toxoplasma gondii and Neospora caninum in the Polish pig population. 1034 serum samples were collected from 16 commercial farms localised in 9 different provinces (voivodeships) of Poland from pigs belonging to the following age categories: piglets (259), weaners (220), fatteners (243), gilts (70), and sows (242) were subjected to ELISA assay with the use of commercially available kits.

RESULTS

The overall seroprevalence of Toxoplasma gondii was 11.3% (117/1034), and it was significantly higher in sows compared to other age categories (28.1%; p < 0.05). Regarding the province of Poland, the highest proportion of seropositive pigs was found in Kujawsko-Pomorskie and Podlaskie; meanwhile, in Łódzkie, Pomorskie, and Warmińsko-Mazurskie observed seroprevalence was 0%. Among tested samples, only one (1/1034; 0.097%) was positive for Neospora caninum antibodies, and it was collected from gilt maintained on the farm in Zachodniopomorskie.

CONCLUSIONS

This study updates the data on Toxoplasma gondii epidemiology in pigs reared in Poland, showing relative stability in the infection with this parasite. It also provides the first data on Neospora caninum circulation in the Polish pig population.

Global Prevalence of Neospora caninum in Domestic Pigs (Sus domesticus) and Wild Boars (Sus scrofa): A Systematic Review and Meta-Analysis

BACKGROUND

Neospora caninum (Apicomplexa, Sarcocystidae) is a protozoan parasite regarded as a major cause of reproductive failure in cattle. Swine are susceptible to N. caninum infection; however, the role of these animals in the circulation, maintenance, and transmission of N. caninum remains unclear. Therefore, we aimed to estimate the global seroprevalence of N. caninum in domestic pigs (Sus domesticus) and wild boars (Sus scrofa).

METHODS

Online databases including PubMed, Web of Science, Scopus, and Google Scholar were systematically searched to identify relevant studies up to 30 April 2024. A random-effects meta-analysis model was used to estimate the overall and subgroup-pooled prevalence of N. caninum across studies. The Cochrane test (Q) and the I2 index were employed to heterogeneity. Funnel plots and Egger's regression test were used to evaluate publication bias, year of publication, and sample size.

RESULTS

A total of 11,124 animals from 26 eligible studies were included. The pooled seroprevalence of N. caninum in swine was 17% (95% CI: 7%-26%) with a prevalence of 17% in domestic pigs and 16% in wild boars. In the subgroup analysis, the highest prevalence was observed among female animals, with a pooled seroprevalence of 17% (95% CI: 7%-26%). The pooled seroprevalence of N. caninum was nearly equal in adult and sub-adult swine (18% and 14%, respectively). The overall seroprevalence of N. caninum in swine, based on sample size and year of publication, showed no statistically significant correlations.

CONCLUSION

The present study showed that domestic swine are suitable intermediate hosts of N. caninum based on serological findings. However, further studies are needed to describe the epidemiology of the N. caninum and to isolate the parasite from swine to confirm this hypothesis.

Seroprevalence of Toxoplasma gondii, Neospora caninum and Trichinella spp. in Pigs from Cairo, Egypt

Pork production is a niche economy in Egypt, and pigs are typically raised as backyard animals with no sanitary control, potentially exposing them to various pathogens. Commercially available ELISAs were used to detect specific antibodies to the food-borne zoonotic parasites Toxoplasma gondii and Trichinella spp., as well as to Neospora caninum, in serum samples of pigs slaughtered at Egypt's only licensed pig abattoir, the El-Bassatin abattoir in Cairo. Among the tested sera (n = 332), seroreactivity for T. gondii was 45.8% (95% confidence interval: 40.4-51.3), N. caninum was 28.0% (95% CI: 23.3-33.2), and Trichinella spp. was 1.2% (95% CI: 0.4-3.3). Mixed infection was only detected for T. gondii and N. caninum (18.7%; 95% CI: 14.7-23.4). The seroprevalence of T. gondii was significantly higher (p = 0.0003) in animals collected from southern Cairo (15 May city slum) than in eastern Cairo (Ezbet El Nakhl slum). Seroprevalence for N. caninum was higher in western (Manshiyat Naser slum; p = 0.0003) and southern Cairo (15 May city slum; p = 0.0003) than in that of eastern Cairo (Ezbet El Nakhl slum; p = 0.0003). Moreover, female pigs exhibited a higher rate of N. caninum antibodies than male ones (p < 0.0001). This study provides the first seroprevalence data for N. caninum in pigs in Egypt, and updates the prevalence of the zoonotic parasites Trichinella spp. and T. gondii.

Optimization of the most widely used serological tests for a harmonized diagnosis of Toxoplasma gondii infection in domestic pigs

The intake of Toxoplasma gondii tissue cysts through raw or undercooked pork meat is one of the main infection sources for humans. Thus, surveillance is recommended to control and prevent infection in domestic pigs. However, the lack of comparative studies hampers the updating of their performance and the comparison of seroprevalence data. Therefore, the aim of this study was to develop and validate three in-house tests and accomplish a comparative analysis of the most widely used serological tests employed in pigs. A panel of sera from pigs experimentally infected with either oocysts or tissue cysts from type II and III isolates (n = 158) was used to develop and validate a tachyzoite-based Western blot assay. Then, this technique was used as a reference to develop and preliminary validate a lyophilized tachyzoite-based enzyme-linked immunosorbent assay and an immunofluorescence antibody test. Next, a comparative study of the three in-house tests and three widely used commercial ELISAs (IDScreen®, PrioCHECK™ and Pigtype®) was accomplished with the abovementioned sera together with an additional serum panel of pigs experimentally infected with oocysts from the type II isolate (n = 44) and a panel of naturally infected pigs (n = 244). The results obtained by the majority of the tests were regarded as reference, and data analyses included TG-ROC calculations and agreement tests. Finally, the kinetics of anti-T. gondii IgGs from experimentally infected pigs was analyzed. Excellent sensitivity (Se) and specificity (Sp) values (≥ 93%) and moderate to near perfect agreement (k = 0.63-0.91) were observed using sera from experimental infections without requiring further readjustment, except for PrioCHECK (100% Se, 73% Sp). However, the Se of IDScreen® (87%) and TgSALUVET WB (71%) and the Sp of PrioCHECK (72%) were slightly or notably reduced when sera from naturally infected animals were analyzed, which also influenced the kappa values (k = 0.30-0.91). Cutoff readjustments increased the Se and Sp values to equal to or above 97% for all tests, except for TgSALUVET WB, which can be used as a reference for initial validation of tests, but it is not recommended for routine diagnosis. Seroconversion was recorded from two weeks post-infection by most of the tests, with significantly higher IgG levels in sera from pigs infected with the T. gondii type III vs. type II isolate. Again, differences regarding the test employed were observed. Differences in the diagnostic performance among tests evidenced the need to harmonize serological techniques to obtain comparable and reliable results.

Serological Prevalence of Toxoplasma gondii, Neospora caninum, and Sarcoptes scabiei var. suis in Wild Boars (Sus scrofa) Hunted in a Highly Anthropized Area in Italy

Due to the increasing expansion into urban and rural areas, wild boars represent a potential source of infection with zoonotic and animal-specific parasites for both humans and animals. Therefore, the aim of this study was to investigate the serological prevalence to Toxoplasma gondii, Neospora caninum, and Sarcoptes scabiei var. suis in blood samples from wild boars (Sus scrofa) hunted in an anthropized area in Italy. Enzyme-linked immunosorbent assay (ELISA) tests were used to detect antibodies anti-T. gondii and anti-S. scabiei and an immunofluorescence antibody test (IFAT) for antibodies anti-N. caninum. 81 out of 128 wild boars (P = 63.3%) resulted positive for at least one of the three parasites. 68 of them were seropositive to T. gondii (P = 53.1%) and 14 to N. caninum (P = 10.9%). 9 wild boars resulted seropositive to S. scabiei var. suis (P = 7.0%). Sampling season was the only significant risk factor related to S. scabiei var. suis seroprevalence (OR = 7.8). The high occurrence of T. gondii supports the role of this species as a source of infection for other animals and humans. Furthermore, the serological prevalence of N. caninum and S. scabiei var. suis in wild boars from the study area characterized by the presence of numerous dairy cattle and pig farms is relevant to demonstrate its suitability for the circulation of these parasites both in domestic and wild species.

Prevalence of Neospora caninum antibodies in fattening pigs and sows from intensive farms in northern Italy

Neospora caninum (Apicomplexa, Sarcocystidae) is a major cause of reproductive failure in cattle. In pigs, only a few studies investigated the effects of this parasite on reproductive efficiency. Considering the relevance of swine farms in northern Italian regions, an epidemiological survey was designed to investigate the spread of N. caninum infection. Three hundred seventy fattening pigs and sows from 23 intensive farms in Lombardy were sampled. Sera were analyzed by a commercial immunofluorescence antibody test. Statistical analysis through univariate and multivariate generalized linear models was conducted to detect farm management practices enhancing the risk of infection. At the farm level, 52.1% (12/23) of the selected farms, 72.7% housing sows and 40% fattening pigs, scored positive. At the individual level, 25 animals (25/370, P = 6.7%) were positive to N. caninum antibodies: one fattening pig and two sows showed an antibody titer of 1:100, and in two sows, an antibody titer of 1:400 and 1:6400 was evidenced. A higher seroprevalence was detected in sows (17/151, P = 11.2%) if compared to fattening pigs (8/219, P = 3.6%) (OR = 1.19, P value = 0.000 in sows). Moreover, a higher seroprevalence was recorded in farms with low and moderate sanitary score (P = 100% and P = 64.2%, respectively) if compared to farms with high sanitary score (P = 22.2%) (OR = 1.24, P value = 0.007 in score = 1 and OR = 1.10, P value = 0.050 in score = 2). This study provides the first data on the circulation of N. caninum in intensive swine farms in Italy, demonstrating the spread of the parasite in fattening pigs and sows in Lombardy region.

Detection of anti-Neospora caninum antibodies in sheep's full-cream milk by a time-resolved fluorescence immunoassay

Ovine neosporosis, caused by the Apicomplexan parasite Neospora caninum, leads to reproductive failure worldwide. Nowadays, there is a trend to develop diagnostic techniques using non-invasive samples, such as milk, in order to reduce animal stress, sample collection effort, and costs. The objective of this study was to develop and validate a highly sensitive and specific serological technique, based on a time resolved-fluorescence immunoassay using a N. caninum GRA7 antigen (GRA7-TRFIA), for the detection of anti-N. caninum immunoglobulins G on sheep' full-cream milk samples. An analytical validation was performed, including intra- and inter-assay precision, analytical sensitivity and accuracy. The diagnostic performance of the assay was evaluated by studying the positive-negative discrimination by Mann Whitney U tests. In additon optimal cut-offs, diagnostic sensitivity and specificity, and areas under the curve were calculated by three Receiver Operating Curve (ROC) analyses, using GRA7-TRFIA and a N. caninum tachyzoite soluble extract-based ELISA (NcSALUVET-ELISA) in blood sera, and the coinciding results of both techniques, as reference techniques. Moreover, Spearman's correlation of GRA7-TRFIA in milk with the techniques in sera and agreement (kappa values) were also estimated. GRA7-TRFIA for milk samples showed an adequate precision, with high analytical sensitivity and accuracy. Regarding ROC analyses, at the optimal cut-offs, the diagnostic sensitivity and specificity were more than 90 % in all cases. In addition, GRA7-TRFIA values in milk were more positively correlated to GRA7-TRFIA values in blood sera than in the case of values obtained with NcSALUVET-ELISA. GRA7-TRFIA in milk showed an almost perfect agreement with GRA7-TRFIA in blood sera (kappa = 0.98) and with the coinciding results of GRA7-TRFIA and NcSALUVET in blood sera (kappa = 1.00), while it has a substantial agreement with NcSALUVET-ELISA (kappa = 0.69). In the light of these results, GRA7-TRFIA in full-cream milk samples is a highly sensitive technique that could be used for screening anti-N. caninum antibodies in sheep flocks.

Experimental infection of tachyzoites of the NC1 strain of Neosporacaninum in female swine

Neospora caninum is a protozoan that can cause reproductive problems in several animal species. Although N. caninum infection has been reported in swine, the pathogenesis and clinical signs are not fully known in this species. The objective of this work was to evaluate the effect of experimental infection with tachyzoites of the N. caninum strain Nc1 in swine matrices at different stages of gestation. For that purpose, 12 gilts, seronegative for N. caninum and T. gondii, were selected and allocated into four groups of three animals each. Animals in group A were not inoculated (control) and animals in groups B, C, and D were inoculated intravenously with of 2.9 × 10⁷ tachyzoites, 30 days before conception, and at 45 and 90 days of gestation, respectively. Temperature, heart rate, blood, saliva, and vaginal mucus samples from the animals were collected periodically until the time of delivery for the investigation of IgG and IgM antibodies against N. caninum using IFAT and PCR to detect the parasite DNA. All gilts sero-converted from 5 and 7 DPI (days postinoculation) to IgM and IgG, respectively. Two gilts showed hypothermia on the 5th and 7th DPI, and five inoculated animals had leukocytosis on the 7th DPI. It was possible to detect DNA of N. caninum in samples of saliva (33/84), vaginal mucus (17/84), and blood (2/84). Based on serology (IgM) and PCR, three animals in group B showed evidence of reappearance of the infection during pregnancy. It is concluded that N. caninum can cause clinical signs in infected swine females, in addition to indicating saliva as a suitable diagnostic biological material for the detection of N. caninum DNA in this animal species.

SPDB: a specialized database and web-based analysis platform for swine pathogens

The rapid and accurate diagnosis of swine diseases is indispensable for reducing their negative impacts on the pork industry. Next-generation sequencing (NGS) is a promising diagnostic tool for swine diseases. To support the application of NGS in the diagnosis of swine disease, we established the Swine Pathogen Database (SPDB). The SPDB represents the first comprehensive and highly specialized database and analysis platform for swine pathogens. The current version features an online genome search tool, which now contains 26 148 genomes of swine, swine pathogens and phylogenetically related species. This database offers a comprehensive bioinformatics analysis pipeline for the identification of 4403 swine pathogens and their related species in clinical samples, based on targeted 16S rRNA gene sequencing and metagenomic NGS data. The SPDB provides a powerful and user-friendly service for veterinarians and researchers to support the applications of NGS in swine disease research. Database URL: http://spdatabase.com:2080/.