Experimental porcine neosporosis

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.

Occurrence of anti-Toxoplasma gondii and anti-Neospora caninum antibodies in pigs in the State of Pará, Brazil

We investigated the occurrence of Toxoplasma gondii and Neospora caninum antibodies in pigs raised in the Northeast of Pará, Brazil. At Study I, convenience sampled 151 pigs at two slaughterhouses, with and without state inspection; and Study II, which assessed 159 pigs with probabilistic sampling from nine pig farms. Serological analysis was performed using indirect fluorescent antibody test for T. gondii and N. caninum with a cutoff of 64 and 50, respectively. Overall, 6.77% pigs were seropositive for T. gondii and 5.16% for N. caninum. In Study I, pigs slaughtered with and without state inspection presented similar occurrence for both coccidia (p>0.05). Study II found an association between N. caninum seropositivity and sludge discarded into the soil, feeding pigs with animal-based protein, subsistence system, and absence of nipple drinkers. No association was found for T. gondii. Pigs from Pará are a potential source of T. gondii infection to humans. To our best knowledge, this is the first study to report anti-N. caninum antibodies in the serum of pigs in Pará State, Brazilian Amazon.

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.

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.

Antibodies anti-Toxoplasma gondii and anti-Neospora caninum in backyard pigs from the state of Mato Grosso, Brazil

To estimate the seroprevalence of Toxoplasma gondii and Neospora caninum, using an indirect immunofluorescent assay (IFA), and identify the risk factors associated, serum samples were collected from 1,070 pigs from 320 backyard pig farming in the of Mato Grosso state. The animal-level seroprevalence of T. gondii and N. caninum was 32.48% and 13.49%, respectively, with a herd seroprevalence of 55.63% for T. gondii and 27.81% for N. caninum. Feeding the animals with leftovers increases the probability of the presence of anti-T. gondii antibodies in pigs by 1.09-fold. Unlike to T. gondii, feeding with leftovers was found to be negatively associated with N. caninum seropositivity in farm-level analysis and in the animal-level model, so decreasing the chances of positivity. Yet, age was considered a risk factor for N. caninum seropositivity. Further studies are necessary to evaluate the impact of T. gondii infection on backyard pig farming production, and its importance as a source of toxoplasmosis infection in humans in the Mato Grosso state, as well as, the role of domestic pigs in the epidemiology of neosporosis.

Seroprevalence of Toxoplasma gondii and Neospora caninum in slaughtered pigs in the Czech Republic

In the Czech Republic, sera from 551 clinically healthy adult slaughtered pigs (females, 6–8 months old) were collected during the first half of June in 2010. Sera were tested for Toxoplasma gondii-specific IgG antibodies by an enzyme-linked immunosorbent assay; samples with more than 50% S/P were considered as positive. The same samples were also analysed for Neospora caninum antibodies using a commercial competitive-inhibition enzyme-linked immunosorbent assay; samples with more than 30% inhibition were considered as positive. Antibodies against T. gondii were found in 198 pigs (36%) in all districts with prevalences ranging from 18% to 75%. Antibodies against N. caninum were found in 16 pigs (3%); positive animals were found in 4 districts with prevalences ranging from 1% to 20%. Indication of mixed infections (concurrent presence of both N. caninum and T. gondii antibodies) was found in 8 (1·5%) pigs. The results of our study indicate that pigs in the Czech Republic have a relatively high seroprevalence for T. gondii, while they have only a low seroprevalence for N. caninum. Therefore, natural infection with T. gondii seems to be very common in Czech pigs. It is the first evidence of N. caninum antibodies in pigs in the Czech Republic. These results complete data about N. caninum infection in pigs in Europe.

Seroprevalence of Neospora caninum in non-carnivorous wildlife from Spain

Serum samples from 1034 non-carnivorous wildlife from Spain were tested for antibodies to Neospora caninum by competitive screening enzyme linked immunosorbent assay (ELISA) and confirmed by an indirect fluorescent antibody test (IFAT). High agreement was observed between results in both techniques (kappa value higher than 0.9). Prevalences of N. caninum antibodies positive by both techniques were 11.8% of 237 red deer (Cervus elaphus), 7.7% of 13 barbary sheep (Ammotragus lervia), 6.1% of 33 roe deer (Capreolus capreolus) and 0.3% of 298 wild boar (Sus scrofa). In one of 53 hares (Lepus granatensis), antibodies were found in the ELISA but could not be confirmed by IFAT due to lack of sample. Antibodies to N. caninum were not found in any of 251 wild rabbits (Oryctolagus cuniculus), 79 fallow deer (Dama dama), 27 mouflon (Ovis ammon), 40 chamois (Rupicapra pyrenaica) and three Spanish ibex (Capra pyrenaica). Statistically significant differences were observed between N. caninum seroprevalence in red deer and management of hunting estates (open versus fenced) with higher prevalence in fenced estates, and among sampling sites. Seroprevalence was particularly high in some areas (MO estate in South-Central Spain or some estates of Catalonia, North-East Spain), while no contact with N. caninum was observed in others. Results indicate that in certain areas of Spain, N. caninum is present in wildlife, especially in red deer. These results have important implications in both sylvatic cycles and may influence the prevalence of infection in cattle farms in those areas. To our knowledge, this is the first report of antibodies to N. caninum in wildlife from Spain and the first report of N. caninum antibodies in barbary sheep and wild boar.

Cross-sectional survey in pig breeding farms in Hesse, Germany: seroprevalence and risk factors of infections with Toxoplasma gondii, Sarcocystis spp. and Neospora caninum in sows

A cross-sectional survey was performed to estimate the prevalences of antibodies to Toxoplasma gondii (ELISA, IFAT), Sarcocystis spp. (ELISA, using S. miescheriana as antigen) and Neospora caninum (ELISA, immunoblotting) in sows from breeding farms in southern Hesse, Germany. A total of 2041 plasma samples of sows from 94 randomly selected farms was examined. Data on farm profiles, husbandry management and sows were collected by a questionnaire and exploratively analysed. For T. gondii the ELISA results agreed well with the results obtained by IFAT (kappa=0.71). Antibodies to T. gondii were detected by ELISA in 19% of the sows. Sixty-nine percent of the farms had at least one seropositive sow, and a within-farm seroprevalence of >or=50% was observed in 14% of all farms. The prevalence of anti-T. gondii antibodies was positively correlated with the age of sows. The within-herd seroprevalence was significantly higher in farms with reproductive disorders than in those without such problems. On the farm level, the farm type 'piglet production' (versus 'pedigree breeding' or 'farrow-to-finish') was the only risk factor associated with the presence of T. gondii-seropositive sows. Antibodies to Sarcocystis spp. were found in 29% of the sows. Seventy-two percent of the farms harboured at least one seropositive sow, and a within-farm seroprevalence of >or=50% was detected in 23% of all farms. The seroprevalence increased significantly with the age of sows. On the farm level, only the farm type 'piglet production' (versus 'pedigree breeding') and the replacement of sows by purchasing (versus raising on the own farm) were identified as risk factors for seropositivity. Antibodies to N. caninum were detected in one sow using both the screening ELISA and the confirmatory immunoblotting technique. This may indicate the first natural N. caninum infection in pigs.

The comparative pathogenesis of neosporosis

Since its first description in dogs in 1984, the protozoan parasite Neospora caninum has been found to infect a wide range of animals, worldwide. In cattle, N. caninum has particular significance as a cause of abortion in which persistence of infection in the mother, recrudescence of the parasite during pregnancy, and the vulnerability of the placenta and foetus to invasion are important features. This article discusses how Neospora invades cells, how it infects and causes disease in several animal species, and particularly how it has evolved a special niche in cattle and dogs that ensures its survival.

Serological investigation of aborted sheep and pigs for infection by Neospora caninum

Serology for Neospora caninum was undertaken using direct ELISAs on sera from 660 aborted sheep and 454 breeding sows, which had aborted or were considered infertile. All ovine sera were further tested by indirect fluorescent antibody test (IFAT) for N. caninum, and a latex agglutination test (LAT) for Toxoplasma gondii was performed on 423 of the samples, including all those positive by ELISA. ELISA-positive porcine sera were tested by IFAT and an inhibition ELISA for antibodies to N. caninum and by LAT for T. gondii. Only 3 (0.45%) of the ovine sera were seropositive for N. caninum by both ELISA and IFAT whereas although 40 porcine sera were seropositive by ELISA all were negative by IFAT. The results suggest that environmental exposure to N. caninum occurs rarely in sheep and pigs.

Prevalence and diversity of Arcobacter spp. isolated from the internal organs of spontaneous porcine abortions in Denmark

A study was conducted to determine the prevalence and possible significance of campylobacteria in pig abortions in Denmark. Surface-cauterised liver and kidney samples from 55 aborted pig fetuses submitted to the Danish Veterinary Laboratory were taken and a sensitive isolation procedure used to examine pooled tissue samples for Campylobacter, Arcobacter and Helicobacter spp. Routine microbiological, immunological, and histopathological examinations were also performed to identify concurrent infections or histopathological changes. The abortions tested negative for established abortifacient pathogens (Brucella, Leptospira, PPV, PRRSV), but Arcobacter spp. were recovered from 23/55 abortions. Co-infections with Streptococcus suis, Escherichia coli, and haemolytic streptococci were observed in 7/23 Arcobacter-positive fetuses, and in 4/32 Arcobacter-negative fetuses. Histopathological analyses identified placentitis, pneumonia, hepatitis and encephalitis among the study group. However, no obvious pathologic features were solely associated with Arcobacter-positive cases, nor were Arcobacter-like bacteria observed in tissue samples. Protein profile analyses of the 27 Arcobacter isolates identified 11 as A. cryaerophilus and 10 as A. skirrowii. Six strains could not be classified into any existing species and were phenotypically distinct, thus, potentially representing at least one new species. The identification results showed that multiple taxa could be found in a single fetus, and in distinct aborted fetuses from a single sow. The high prevalence of arcobacters in Danish pig abortions may account for at least some of the >90% of cases in which no established abortifacient agent is detected, but further studies are needed to define the role of each species, especially where co-infections with other bacteria are present.

Vaccine development against Neospora caninum infection

Neospora caninum is a recognized protozoan parasite of a wide range of mammalian hosts, and was reported for the first time in 1988. The isolation of its oocysts in dog's faeces in 1998 led to its establishment as a parasitic species undergoing typical coccidian life cycle. Infection with N. caninum causes paralysis and death in young livestock and companion animals, and is associated with abortions and stillbirth in cattle, and neurologic disease in calves. Considering the economic and agricultural importance of neosporosis, there is the urgent need to develop biological control measures aimed at preventing its transmission, infection, as well as reducing severity of the disease. In this paper, we have reviewed the progress made to date on the parasite-host immunology and on vaccine development including its prospects, and discussed possible strategies in the formulation of vaccine(s) against neosporosis.

Transplacental transmission of Toxoplasma gondii in minipigs infected with strains of different virulence

Infections with the zoonotic protozoan Toxoplasma gondii during pregnancy can result in severe fetal infections. To investigate the use of pigs as animal models for congenital toxoplasmosis, tachyzoites of 5 T. gondii strains, with low to intermediate virulence in mice, were intravenously inoculated into pregnant minipig gilts. Two strains caused abortions of uninfected fetuses following severe disease of the mothers. One strain caused no disease in the gilts but slightly elevated anti-T. gondii antibodies in 2 of 9 fetuses. One strain produced clinical disease with 4 mummified fetuses and 2 full-term, congenitally infected piglets in 1 gilt and no clinical disease but elevated specific fetal antibodies in both piglets of the other gilt. Infection with the fifth strain (SVS-O14), which was considered apathogenic to both pigs and mice based on the clinical course of this and previous experiments, resulted in significant numbers of congenitally infected piglets, as indicated by production of anti-T. gondii antibodies in all 12 fetuses; the parasite was identified in 3 of these fetuses. This pattern of infection indicates that pigs infected with SVS-O14 (or a similar strain) are relevant animal models for studies of transplacental transmission and pathogenesis of congenital toxoplasmosis.

Detection of antibodies to Toxoplasma gondii in stillborn piglets in Argentina

Fetal fluids of 738 stillborn piglets from three swine farms in Argentina were examined for antibodies to Toxoplasma gondii. Antibodies were detected in 15 samples at a 1:20 dilution in the indirect fluorescent antibody test and 10 samples were positive in the modified agglutination test (MAT) at a dilution of 1:25; four of these samples had a MAT titer of > or = 1:100. This survey indicates a low rate of congenital T. gondii infection in stillborn pigs in Argentina.

Recent advances in Neospora and neosporosis

Neospora caninum has emerged as a major cause of abortion in cattle in many countries. This paper reviews recent advances in the life cycle and biology of Neospora with the emphasis on bovine neosporosis. The role of the recently discovered oocyst stage of N. caninum in the epidemiology of neosporosis is discussed. Progress made in serologic diagnosis of N. caninum infection is discussed. There is no vaccine for preventing Neospora-induced abortions in cattle or to prevent oocyst shedding in dogs.

The antigenic composition of Neospora caninum

Neospora caninum is an apicomplexan parasite which causes neosporosis, namely stillbirth and abortion in cattle, and neuromuscular disease in dogs. Although N. caninum is phylogenetically and biologically closely related to Toxoplasma gondii, it is antigenically clearly distinct. In analogy to T. gondii, three stages have been identified. These are: (i) asexually proliferating tachyzoites; (ii) tissue cysts harbouring slowly dividing bradyzoites; and (iii) oocysts containing sporozoites. The sexually produced stage of this parasite has only recently been identified, and has been shown to be shed with the faeces from dogs orally infected with N. caninum tissue cysts. Thus dogs are definitive hosts of N. caninum. Tachyzoites can be cultivated in vitro using similar techniques as previously described for T. gondii. Methods for generating tissue cysts containing N. caninum bradyzoites in mice, and purification of these cysts, have been developed. A number of studies have been undertaken to identify and characterise at the molecular level specific antigenic components of N. caninum in order to improve serological diagnosis and to enhance the current view on the many open questions concerning the cell biology of this parasite and its interactions with the host on the immunological and cellular level. The aim of this paper is to provide an overview on the approaches used for detection of antigens in N. caninum. The studies discussed here have had a great impact in the elucidation of the immunological and pathogenetic events during infection, as well as the development of potential new immunotherapeutic tools for future vaccination against N. caninum infection.

Comparison of the IFAT and Iscom-ELISA response in bovine foetuses with Neospora caninum infection

The study was carried out to evaluate the efficacy of foetal serology in the diagnosis of Neospora-associated bovine abortions. Fluids from 14 foetuses of cows with confirmed neosporosis (Group A), seven foetuses with confirmed bovine viral diarrhoea virus (BVD infection) (Group B) and 11 aborted foetuses without demonstrable infection (Group C) were examined. The age of the foetuses ranged from 4.5 months to 9 months. Albumin concentration (measured by Rocket Immunoelectrophoresis) was not significantly different in Group A compared with that in both Groups B and C, while that in Group B was significantly lower than in Group C. Levels of total IgG ranged from 0.01 to 1.78 (mg IgG) ml(-1) measured by single radial immunodiffusion technique. A measurable level of total IgG was found in all foetuses from Groups A and B, with no significant difference between levels in the two groups. Only one foetus in Group C had a detectable level of IgG. All foetuses in Group A had a specific IgG response (titre> or = 20) against Neospora caninum using the IFAT, while no positive responses in IFAT were found in Groups B and C. Measurement of specific IgG1 and IgG2 by Iscom-ELISA showed one and three false-negative results, respectively, in Group A. The IgG1 and IgG2 response in Group A was correlated according to the Spearman test (r = 0.66). Increasing age of the foetuses correlated significantly with the foetal IgG concentration, the specific IgG and IgG1 + IgG2. On the basis of the results obtained, it was concluded that the IFAT with a cut-off titre of 1:20, was a specific method for diagnosis of neosporosis in foetuses older than 4.5 months. The Iscom-ELISA also showed promising results as a method for screening specific antibodies against N. caninum in foetal fluid.

Neospora caninum infection and repeated abortions in humans

To determine whether Neospora caninum, a parasite known to cause repeated abortions and stillbirths in cattle, also causes repeated abortions in humans, we retrospectively examined serum samples of 76 women with a history of abortions for evidence of N. caninum infection. No antibodies to the parasite were detected by enzyme-linked immunosorbent assay, immunofluorescence assay, or Western blot.