Detection of Neospora caninum in semen of bulls

Assessment of Neospora caninum infection in bulls using serological and molecular techniques

Neospora caninum is a significant cause of abortion and economic losses in cattle worldwide. The main aim of the present work was to detect the prevalence of N. caninum infection in bulls in Hamedan (Iran) using serology and molecular techniques. All blood samples (n = 792) were screened for detecting the antibodies to N. caninum using enzyme-linked immunosorbent assay (ELISA). Then seropositive animals were rechecked using the immunofluorescent antibody test (IFAT). Also, blood, epididymis, and spinal cord samples were collected from animals for molecular analysis using nested PCR. In serology, using ELISA, 3.91% of animals were seropositive for N. caninum. Additionally, true prevalence based on the sensitivity and specificity of the ELISA was calculated 1.25% (95% CI: 0.48-2.02%). Neospora-infection in animals, calculated as the number of bulls seropositive and/or one sample positive to nested PCR, was 3.40%; and 19 bulls tested positive by both serology and molecular diagnostic methods. The overlaps between ELISA and molecular results were observed in 74.19% of whole blood samples, 80.64% of the epididymis, and 87.09% of the spinal cord. Using ELISA, the seroprevalence of N. caninum was detected 1.8% in ≤2 and 5.45% in >2 years old group of animals (p = 0.009, PR = 3.1). In addition, the seropositivity in Holstein and native breed animals was calculated 6.57% and 2.93%, respectively (p = 0.019, PR = 2.3). Seven sequences with 94.9-99.3% similarity were detected in multiple alignments of positive PCR products. Our work was the first comprehensive evaluation of Neospora-infection/neosporosis in Iranian bulls. We detected a low prevalence of infection in animals compared to previous reports. The ELISA is a sensitive serological technique for detecting the highest number of positive bulls in the present investigation and, the nested PCR is a reliable technique to identify Neospora-DNA.

Neospora caninum infection in dairy cattle in Egypt: a serosurvey and associated risk factors

Neospora caninum (N. caninum) is one of the causative agents that causing cattle abortion, and severe economic losses. Due to the scarcity of data on N. caninum infection in Egyptian cattle, the purpose of this study was to estimate the seroprevalence and determine the risk factors for parasite infection. In four governorates in northern Egypt, 540 blood samples from cattle were taken, and tested using a commercial ELISA kit. The overall seroprevalence of N. caninum in examined cattle was 28.89%. A multivariate logistic regression model determined that age (OR = 2.63, P < 0.001), manual milking (OR = 1.39, P = 0.14), abortion history (OR = 2.78, P < 0.0001), repetition of estrus (OR = 2.31, P < 0.0001), and contact with dogs (OR = 2.57, P < 0.0001) were significant risk factors. The findings proved that N. caninum infection was one of the factors contributing to abortion and financial losses in dairy cattle in Egypt. Therefore, the application of sanitary security and control programs is very important in dairy farms.

Serodiagnosis and Risk Factors Associated with Infectious Agents of Reproductive Diseases in Bovines of Chiquinquirá, District of Boyacá (Colombia)

The productivity of cattle farms is affected by infectious and noninfectious factors that generate economic losses and cause reproductive failure represented by low conception rates, embryonic mortality, abortions, and fetal mummification. The infectious agents that most impact the reproductive health of the bovine species from conception to birth are bovine herpesvirus type 1 (BoHV-1) causing infectious bovine rhinotracheitis (IBR), bovine viral diarrhea virus (BVDV), bovine parainfluenza virus type 3 (PI3), Neospora caninum and Leptospira spp. The objective of this study was to diagnose the presence of BoHV-1, bovine viral diarrhea (BVD), PI3, Neospora caninum, and Leptospira spp. by serology and identify the risk factors associated with infectious agents of reproductive interest in bovines of Boyacá (Colombia). A descriptive cross-sectional study was developed, with simple random sampling, where a sample size of 601 female cattle of Holstein, Jersey, and Normande breeds of different age groups was determined. Blood samples were taken and processed using the indirect ELISA technique (SYNBIOTICS®, SERELISA® BVD p80 Ab Mono Blocking, Ingezim R.12.NC.K, PRIMACHECK VPI-3®) and the MAT test for the diagnosis of bovine leptospirosis. The data were processed with the statistical program Epi Info™. The highest apparent seroprevalence was established for infectious bovine rhinotracheitis (61.1%), followed by BVD (37.6%), PI3 (40.9%), neosporosis (51.1%), and leptospirosis (14.8%). Variables such as age >4 years and Holstein breed for IBR and >4 years for BVD were established risk factors. Considering our results, we suggest implementing prevention and control plans that include vaccination as a prophylactic measure and biosecurity tools that reduce the probability of contagion and transmission of pathogens.

Molecular detection and phylogenetic analysis of Neospora caninum in various hosts from Iran

Different N. caninum strains with distinct biological characteristics and pathogenicity have been introduced from various areas of the world. This study aimed to detect Neospora-infection in different hosts from Iran using the nested-Polymerase Chain Reaction (PCR) technique and to perform the phylogenetic analysis of N. caninum isolates using the Nc-5 gene. Different species of parasite hosts (cattle, dogs, rodents, cats, and birds) from the dairy farms with history of abortion with intensive breeding systems in Hamedan Province, Iran were included for sampling. The stillbirth fetuses of cattle, sheep, and goats were also collected from the slaughterhouse. The nested-PCR technique was used to identify the Neospora-DNA in the aborted fetal materials. The PCR products of the positive samples were sequenced and compared with other isolates in GenBank. Antibodies to N. caninum was found in 19.1% of dogs. Also, 11.4% of dogs were positive for Neospora-like oocysts using microscopy method. The molecular prevalence of N. caninum was 10.6% in dogs, 13.6% in cattle, 35.4% in the aborted fetuses of cows, 31.9% in rodents, 7.6% in pigeons, 1.9% in sparrows, 5.1% in cats, and 7% in the semen sample of bulls. A sampled coyote was positive while the stillbirth fetuses of sheep and goats were negative. The multiple sequence alignments indicated that 34 sequences of N. caninum bore a 94.9-99.3% similarity to each other. Hence, these sequences were classified into two major clusters (clusters A and B) and seven sub-groups (isolates 1-7). The sequence of coyote had a high similarity to the sequences derived from dogs and cows. Also, root diagram showed the isolates of current study and previous reported from Iran have a similar origin. This study provided a phylogenetic analysis of Neospora-infection in different hosts, and for the first time, explored Neospora-infection in coyotes from Iran. Different isolates were detected in the studied population in the region. Comparison of the sequences showed the farm dogs play an important role in the life cycle and distribution of the parasite; so the relationship of dogs with the herd and their access to aborted materials should be restricted. Also, regular control of rodents' population and culling of seropositive cows with a history of abortion is essential for cutting the chain of transmission.

Molecular identification of Neospora caninum and co-infection with Toxoplasma gondii in genital apparatus of naturally infected cows in North Tunisia

The aim of this study was to estimate the molecular prevalence of Toxoplasma gondii, Neospora caninum and the co-infection by both Apicomplexan parasites in uterus tissues of cows. PCR was used to detect T. gondii and N. caninum DNA in uterus from 140 uteri of slaughtered cows in the regional slaughterhouse of Béja (Northwest Tunisia). Positive PCR products were sequenced and used for the phylogenetic analysis. The overall molecular prevalence of T. gondii and N. caninum in cows' uterus was 5 and 15.57%, respectively. Co-infection prevalence by the two parasites was estimated to be 2.85%. Risk factors including the age categories significantly affected the molecular prevalence of T. gondii and N. caninum in cows' uterus. The highest molecular prevalence of T. gondii (11.5 ± 3.1) and N. caninum (21.1 ± 11.1; p = 0.038) was observed in cows aged of more than 8 years. There were no differences depicted according to cow's breeds and localities. Comparison of the partial sequences of the ITS1 gene revealed 100% similarity among our N. caninum sequence (MW136256) and those deposited in GenBank. The T. gondii sequence described in this study (MW260335) was 99.4-100% homologous to T. gondii sequences published in the GenBank.To the best of our knowledge, this is the first molecular evidence of N. caninum and T. gondii co-infection in naturally infected cows in North Africa. This information is pertinent in designing control programmes that would reduce economic losses in the livestock industry.

Neosporosis in bulls: potential for venereal transmission, and effect on semen quality and production

Neospora caninum caninum is a protozoan parasite that can cause abortions, birth of congenitally infected calves, and reduced milk production in cattle. Neosporosis in cattle can be transmitted through vertical transplacental transmission from dam to calf, or through horizontal transmission between animals. While it is well established that horizontal transmission from dogs (the definitive host) to cattle (an intermediate host) occurs, it is not clear whether horizontal transmission may occur between cows and bulls during mating. Transmission via infected semen of seropositive bulls was suggested when N. caninum DNA was found in bull semen. The primary objective of this article is to critically evaluate the evidence for venereal transmission of N. caninum between cattle, to determine whether this transmission route is likely to occur. A secondary objective is to review and evaluate published evidence for whether neosporosis in bulls may affect semen quality and production. N. caninum DNA can be detected by PCR in occasional batches of semen straws from bulls that are seropositive for N. caninum. Insemination of heifers with semen experimentally infected with 5 × 10⁴ N. caninum tachyzoites has caused persistent seroconversion in some animals. However, the highest concentration of parasites in the semen of naturally infected bulls was estimated, using quantitative PCR, as 10 tachyzoites. Thus it appears that, whether used for natural or artificial insemination, the semen of bulls naturally infected with N. caninum, does not contain the necessary intrauterine dose of tachyzoites to cause persistent seroconversion in a heifer or cow. Thus, based on the available evidence, the venereal transmission of N. caninum via bull semen is extremely unlikely. Nevertheless, neosporosis in bulls may influence semen quality and production. Epididymal semen concentration, viability, and motility appeared "to be" significantly decreased in N. caninum-seropositive bulls compared to seronegative bulls. Furthermore, semen production could be altered if neosporosis affects the thyroid gland. The thyroid hormones such as triiodothyronine and thyroxine (T4) may affect testicular development. Significantly lower concentrations of T4 were observed in the blood of N. caninum-seropositive, compared with those of seronegative bulls. Longitudinal studies are needed to confirm the long-term effect and significance of neosporosis on semen quality and thyroid hormone concentrations in bulls.

Neosporosis, Toxoplasmosis, and Sarcocystosis in Ruminants: An Update

Neospora caninum, Toxoplasma gondii, and Sarcocystis spp. are related Apicomplexan parasites that have 2 hosts in their life cycles. The definitive hosts excrete unsporulated (Neospora caninum, T gondii) or sporulated (Sarcocystis spp.) oocysts in their feces after ingesting tissue cysts from the tissues of ruminant intermediate hosts. These coccidians can cause abortion and neonatal mortality in ruminants. T gondii and Sarcocystis hominis (from cattle) are zoonotic. This article reviews information on the etiology, life cycle, diagnosis, control and prevention of these parasites and the diseases they cause in ruminants.

Neospora caninum Natural Infection in Tunisian Rams: Serological Study and Molecular Identification of Infection in Semen

PURPOSE

The aim of this study was to estimate the seroprevalence and molecular prevalence and perform a molecular identification of Neospora caninum in semen of Tunisian rams.

METHODS

A total of 92 blood samples were collected from four farms located in four Tunisian governorates (Jendouba, Kairouan, Zaghouan and Ben Arous) and samples were screened with a commercial ELISA kit for N. caninum antibodies. For the same rams, semen samples were collected and tested for the presence of N. caninum ITS1 gene using PCR. Five amplicons were randomly selected for sequencing. A phylogenetic tree was constructed to compare the partial sequences of the ITS1 gene with sequences deposited in GenBank.

RESULTS

The seroprevalence of N. caninum infection was 25% (23/92) and PCR revealed that the molecular infection prevalence in semen was 11.95% (11/92). Kappa test showed an average agreement between seroprevalence and parasite prevalence in semen (κ = 0.44). The highest molecular prevalence was for rams that accomplished more than two mating seasons (21.0 ± 12.1%) compared to those performed less than two mating seasons and yearling individuals (4.0 ± 5.5%) (P = 0.01). There were no differences in N. caninum molecular prevalence according to either breed or locality. Comparison of the partial sequences of the ITS1 gene revealed 99-100% similarity with those deposited in GenBank.

CONCLUSION

To the best of our knowledge, this is the first detection and molecular identification of N. caninum in semen from rams in North Africa. Our findings indicate that N. caninum infection rate was high in rams.

Neospora caninum infection in dairy farms with history of abortion in West of Iran

Neospora caninum is a major cause of abortion and economic losses among dairy farms in Iran and other countries. The main goal of current investigation was to evaluate the presence of antibodies against N. caninum and associated risk factors in dairy herds with history of abortion in Hamedan province of West Iran. A total numbers of 476 and 185 blood samples of pregnant cattle and farm dogs from 10 dairy farms with history of abortion were randomly collected. Bulk milk sample was taken from each farm. All samples were subjected for detection of IgG antibody against N. caninum using ELISA technique. Of all examined animals, 24.8% of cattle and 8.65% of dogs were seropositive to N. caninum. The seroprevalence had significant differences with abortion, stillbirth, metritis, breed, close contact to dogs, wild carnivores, rodents, poultry, and pregnancy using artificial insemination method. There were no significant differences among seroprevalence and different age groups, number and stage of gestation, and herd population. In all investigated farms, bulk milk examination was positive. In examined dogs, there was significant difference between seroprevalence and sex. It was concluded that N. caninum infection may be responsible for abortion and economic losses in dairy farms of the region. This was also the first comprehensive report on associated risk factors to N. caninum infection in dairy farms in the region.

Sperm quality and hormonal levels in C57BL/6 mice infected with Neospora caninum

Neospora caninum is a major pathogen of cattle and dogs, and neosporosis is widespread in five continents. In this study effect of experimental neosporosis on sperm quality of C57BL/6 mice in different days was investigated. Based on the results sperm concentration was not changed in infected groups but neosporosis induced a significant decrease in epididymis sperm motility at 60 days post infection. A significant increase in the number of abnormal sperms at five, 15, 30 and 60 days post infection was found. At days 15, 30 and 60 post infection testosterone concentrations were significantly low in infected groups and FSH level was significantly high in infected groups at five and 30 days post infection. LH level was decreased in infected groups, but the difference was significant at five, 15 and 30 days post infection. Comparison of TSH and T4 levels between groups revealed a significant decrease in infected groups at five, 15, 30 and 60 days post infection. Except 15 days post infection T3 levels decreased significantly in infected groups. GPX activity, MDA and TAC level was significantly increased in infected mice at five days post infection. In this study neosporosis is associated with hypogonadotrophic gonadal insufficiency in infected C57BL/6 male mice.

Seroprevalence and factors associated with Toxoplasma gondii-, Neospora caninum- and Coxiella burnetii-infections in dairy goat flocks from Costa Rica

A total of 391 goats from 13 dairy flocks from all Costa Rican regions were analyzed for Toxoplasma gondii-, Neospora caninum- and Coxiella burnetii-related seroprevalence by enzyme-linked immunosorbent assays (ELISA). Additionally, a risk factor analysis for these parasitic infections was performed based on a questionnaire considering several environmental and housing/management factors. A total of 62.1% (243/391) of individual serum samples revealed seropositive for T. gondii, 7.9% (31/391) for N. caninum, and 1.8% (7/391) for C. burnetii. At herd level, the overall seroprevalence for T. gondii was 100%, for N. caninum 69.2% and for C. burnetii 7.7%. However, no clinical signs related to toxoplasmosis, neosporosis or Q fever were apparent in these flocks. T. gondii-related risk factors were the contact with cats (OR = 3.44; CI 95%; 2.0-5.91), dogs (OR = 5.75; CI 95%; 2.84-11.66), and white-tailed deer (Odocoileus virginianus) (OR = 0.15; CI 95%; 0.08-0.26) within or around the farms. The presence of reproductive males in each flock (OR = 0.32; CI 95%; 0.14-0.74) and the coexistence of sheep (OR = 0.46; CI 95%; 0.2-1.08) and cattle (OR = 5.94; CI 95%; 1.70-20.78) revealed as protective and risk factors respectively for N. caninum infections. This study determined for the first time the seroprevalences of N. caninum, T. gondii and C. burnetii in Costa Rican goat flocks. Particularly, the high within-herd seroprevalences determined for T. gondii requires further surveillance to complement these findings.

Effect of natural neosporosis on bull sperm quality

Neospora is one of the protozoans that can infect the male and female's reproduction system. Despite the existence of N. caninum in the genitalia, its effect on sperm characteristics was not studied yet. Therefore, the aim of this study was to investigate the influence of natural neosporosis on the sperm parameters of bulls. Using 30 bulls with neosporosis diagnosed by modified agglutination test and enzyme-linked immunosorbent assay (ELISA) and 15 healthy bulls, some sperm parameters such as sperm concentration, viability, motility, and morphology were studied and compared. Also, the activity of super oxide dismutase (SOD), glutathione peroxidase (GPX), and malondialdehyde (MDA) level as the biomarker of lipid peroxidation was investigated. Results showed that sperm concentration, viability, and motility were significantly lower in bulls with neosporosis in the present study. There were no significant differences in activities of SOD and MDA level but GPX activity was significantly increased in infected bulls.

Moving past serology: Diagnostic options without serum

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Traditional serology has moved beyond blood as a test medium.

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A number of different samples and tissues are now frequently used in veterinary diagnosis.

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Testing can be robust and accurate and opens up the field to a variety of new opportunities.

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Molecular testing allows direct testing for the agent on a variety of tissues and samples, and pools.

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Pooling of samples can allow for more efficient and cost-effective testing.

Detecting antibodies formed in serum in response to infection is the traditional function of serology. Diagnostic modalities have included complement fixation tests, agar gel immune-diffusion, radioimmunoassay, ELISA and immunofluorescence. More recent technology now allows for the direct detection of pathogens by PCR. This review details the options for diagnostic testing using specimen types other than serum, identifying the advantages and disadvantages of these options and providing evidence for more widespread use of these techniques and specimen types.

Experimental ruminant models for bovine neosporosis: what is known and what is needed

At present, bovine neosporosis is an important worldwide concern because of its wide geographic distribution and economic impact. Abortion is the main clinical sign of bovine neosporosis in both dairy and beef cattle. Ruminant challenge models are critical to evaluate potential vaccine candidates to help tackle bovine neosporosis and to study pathogenesis and host responses to infection. Several research groups have developed ruminant models of Neospora caninum infection independently of others, resulting in a high degree of variability due to the use of different species of animals, breeds, strains/isolates of N. caninum, doses, routes and times of inoculation. Standardization is greatly needed to advance research in a more collaborative, timely and efficient manner. In the absence of widely accepted international guidelines, this manuscript serves to summarize and discuss the different models and parameters currently in use. Parameters essential for the development of non-pregnant and pregnant ruminant models are outlined and the main knowledge gaps are identified. This information could act as the basis to develop a consensus for international standard guidelines for ruminant models of neosporosis that would be helpful for researchers in this field worldwide.

No detection of Besnoitia besnoiti DNA in the semen of chronically infected bulls

Bovine besnoitiosis is a chronic and debilitating disease observed in many European countries that may cause important economic losses in cattle. The recent widespread of the parasite in Europe had led the European Food Safety Authority to declare bovine besnoitiosis as a re-emerging disease in Europe. Many aspects of the epidemiology of bovine besnoitiosis such as the main routes of transmission are still unclear and need to be further studied. Among the different hypotheses, a sexual transmission has not yet been investigated. Therefore, the aim of this study was to evaluate the presence of Besnoitia besnoiti DNA in the semen of naturally infected bulls by using a highly sensitive method (real-time qPCR). Both pre-sperm and sperm fractions of 40 bulls, including seronegative (n = 11), seropositive subclinically (n = 17), and seropositive clinically (n = 12) infected animals, were collected by electroejaculation and analyzed by real-time qPCR. No B. besnoiti DNA was detected in 27 pre-sperm and 28 sperm fractions of the 40 examined bulls, suggesting that the transmission of B. besnoiti infection by the semen of chronically infected bulls is very unlikely.

Neospora caninum and Wildlife

Bovine neosporosis caused by Neospora caninum is among the main causes of abortion in cattle nowadays. At present there is no effective treatment or vaccine. Serological evidence in domestic, wild, and zoo animals indicates that many species have been exposed to this parasite. However, many aspects of the life cycle of N. caninum are unknown and the role of wildlife in the life cycle of N. caninum is still not completely elucidated. In North America, there are data consistent with a sylvatic cycle involving white tailed-deer and canids and in Australia a plausible sylvatic cycle could be occurring between wild dogs and their macropod preys. In Europe, a similar sylvatic cycle has not been established but is very likely. The present review is a comprehensive and up to date summary of the current knowledge on the sylvatic cycle of N. caninum, species affected and their geographical distribution. These findings could have important implications in both sylvatic and domestic cycles since infected wildlife may influence the prevalence of infection in cattle farms in the same areas. Wildlife will need to be taken into account in the control measures to reduce the economical losses associated with this important disease in cattle farms.

Bovine neosporosis: clinical and practical aspects

Neospora caninum is a protozoan parasite with a wide host range but with a preference for cattle and dogs. Since the description of N. caninum as a new genus and species in 1988, bovine neosporosis has become a disease of international concern as it is among the main causes of abortion in cattle. At present there is no effective treatment or vaccine. This review focuses on the epidemiology of the disease and on prospects for its control in cattle. Finally, based on the implications of clinical findings reported to date, a set of recommendations is provided for veterinarians and cattle farmers.

Detection ofNeospora caninumin aborted bovine fetuses and dam blood samples by nested PCR and ELISA and seroprevalence in Beijing and Tianjin, China

Neospora caninuminfection is a significant cause of abortion in cattle. We investigated the tissue distribution ofN. caninumin aborted bovine fetuses and dam blood samples by a nested PCR assay, and compared the nested PCR with ELISA in the diagnosis ofN. caninuminfection. In total, 26 aborted fetuses and 813 blood samples were collected from 8 dairy herds in Beijing (n=212) and Tianjin (n=601), China. Fifteen fetuses (57·7%) were testedN. caninum-positive by the nested PCR.N. caninumDNA was detected from the brain of 52%, kidneys of 22%, skeletal muscle of 18%, and heart of 4% of the aborted fetuses. The PCR-positive cases (55%, 11/20) were higher than seropositive cows (40%, 8/20) in a subset of 20 fetuses, but the PCR results of blood samples of the 20 cows were all negative. The seroprevalence of the 813 samples was 15·5% (43·4% of samples from Beijing, 5·7% of samples from Tianjin), compared to the PCR-positive blood samples of 0·9%. Our study showed that the nested PCR is a valuable diagnostic tool for the primary diagnosis ofN. caninumin aborted fetuses, while ELISA is the preferred assay for testing blood samples collected from cows. The two assays are complementary in determining whether abortions are associated withN. caninuminfection in cattle.

Detection and semi-quantification of Strongylus vulgaris DNA in equine faeces by real-time quantitative PCR

Strongylus vulgaris is an important strongyle nematode with high pathogenic potential infecting horses world-wide. Several decades of intensive anthelmintic use has virtually eliminated clinical disease caused by S. vulgaris, but has also caused high levels of anthelmintic resistance in equine small strongyle (cyathostomin) nematodes. Recommendations aimed at limiting the development of anthelmintic resistance by reducing treatment intensity raises a simultaneous demand for reliable and accurate diagnostic tools for detecting important parasitic pathogens. Presently, the only means available to differentiate among strongyle species in a faecal sample is by identifying individual L3 larvae following a two week coproculture procedure. The aim of the present study is to overcome this diagnostic obstacle by developing a fluorescence-based quantitative PCR assay capable of identifying S. vulgaris eggs in faecal samples from horses. Species-specific primers and a TaqMan probe were designed by alignment of published ribosomal DNA sequences of the second internal transcribed spacer of cyathostomin and Strongylus spp. nematodes. The assay was tested for specificity and optimized using genomic DNA extracted from identified male worms of Strongylus and cyathostomin species. In addition, eggs were collected from adult female worms and used to evaluate the quantitative potential of the assay. Statistically significant linear relationships were found between egg numbers and cycle of threshold (Ct) values. PCR results were unaffected by the presence of cyathostomin DNA in the sample and there was no indication of PCR inhibition by faecal sources. A field evaluation on faecal samples obtained from four Danish horse farms revealed a good agreement with the traditional larval culture (kappa-value=0.78), but with a significantly higher performance of the PCR assay. An association between Ct values and S. vulgaris larval counts was statistically significant. The present assay can reliably and semi-quantitatively detect minute quantities of S. vulgaris eggs in faecal samples.

Possibility of Neospora caninum infection by venereal transmission in CB-17 scid mice

CB-17 scid and BALB/c male mice were inoculated intraperitoneally with Neospora caninum to examine the possibility of its venereal transmission. Some of these mice were killed on days 7 and 20 post-inoculation to examine the genital organs for presence of the parasite. The remaining scid male mice were housed with non-infected female mice from day 7 p.i. and kept with them for 14 days. These scid mice died between days 28 and 35 p.i. N. caninum DNA was detected in the testis of mice on days 7 and 20 p.i. by PCR and tachyzoite viability was determined by bioassay conducted by means of mouse inoculation. Microscopically, fewer tachyzoites were detected in the testis obtained on day 20 p.i., than in other organs. The inoculated BALB/c male mice survived until the end of the experiment with no clinical signs and N. caninum DNA was detected in the testis on day 7 p.i. but not on day 14 p.i. Five of eight female scid mice housed with infected males became pregnant. Tachyzoites were detected in three of these mice and their neonates (n=3, 5 and 13, respectively). In three non-pregnant mice, no parasite was detected. Two of the four female BALB/c mice housed with infected male scid mice became pregnant but the parasite was not detected in them or in the neonates (n=3 and 13, respectively). These results indicate that the tachyzoites were present in the genital organs of the immunodeficient mice from day 7 p.i. and suggest that transmission may occur through mating with male mice.

Experimental neosporosis in bulls: Parasite detection in semen and blood and specific antibody and interferon-gamma responses

AIM

To investigate the presence of Neospora caninum in semen and blood, and the development of specific antibody and interferon-gamma (IFN-gamma) responses in experimentally infected bulls.

METHODS

Eight bulls were intravenously infected with 10(8) live N. caninum tachyzoites of NC-1 isolate. The presence of N. caninum in semen and blood was assessed using a nested-PCR procedure. PCR-positive semen samples were bioassayed using a BALB/c nu/nu mouse model. Specific anti-N. caninum antibody and IFN-gamma responses were also examined. In parallel, eight seronegative bulls were studied as non-infected controls. All bulls were monitored for 26 weeks.

RESULTS

All eight experimentally infected bulls showed N. caninum DNA in their semen and/or blood samples at some time during the course of the study. Parasite load in semen ranged from 0.1 to 14.5 parasites/ml (mean 6.0). N. caninum could not be detected in BALB/c nu/nu mice inoculated with PCR-positive semen samples. A significant increase in mean serum specific IgM antibody response to N. caninum was detected between 10 and 28 days post-infection (p.i.). Serum specific IgG, IgG1, and IgG2 antibody levels in experimentally infected bulls were significantly different after 21, 10, and 14 days p.i. as compared to controls, respectively. Specific anti-N. caninum IgG were detected in seminal plasma from infected bulls and values obtained were different from controls after 25 days p.i. Mean specific IFN-gamma responses in experimentally infected bulls were significantly higher than controls 3 days p.i.

CONCLUSIONS

This is the first study to report the presence of N. caninum DNA in the semen and blood of experimentally infected bulls. Our observations indicate an intermittent presence of N. caninum in low numbers in semen and associated with chronic stage of the infection. This study is also the first to report the detection of anti-N. caninum IgG in seminal plasma of experimentally infected bulls.

Epidemiology and control of neosporosis and Neospora caninum

Neospora caninum is a protozoan parasite of animals. Until 1988, it was misidentified as Toxoplasma gondii. Since its first recognition in dogs in 1984 and the description of the new genus and species Neospora caninum in 1988, neosporosis has emerged as a serious disease of cattle and dogs worldwide. Abortions and neonatal mortality are a major problem in livestock operations, and neosporosis is a major cause of abortion in cattle. Although antibodies to N. caninum have been reported, the parasite has not been detected in human tissues. Thus, the zoonotic potential is uncertain. This review is focused mainly on the epidemiology and control of neosporosis in cattle, but worldwide seroprevalences of N. caninum in animals and humans are tabulated. The role of wildlife in the life cycle of N. caninum and strategies for the control of neosporosis in cattle are discussed.

Intrauterine Neospora caninum inoculation of heifers and cows using contaminated semen with different numbers of tachyzoites

OBJECTIVE

To investigate the potential of different Neospora caninum tachyzoite doses to infect heifers (experiment 1) and cows (experiment 2) when administered in utero by artificial insemination via contaminated semen.

METHODS

In experiment 1, five groups of 5, 7, 8, 9, and 5 cyclic heifers were hormonally synchronized and artificially inseminated with semen containing 0 (A, controls), 10(2) (B), 5 x 10(3) (C), 5 x 10(4) (D), and 5 x 10(5) (E) live N. caninum NC-1 isolate-tachyzoites, respectively. Experimental infection was followed for 100 days. Parasitaemia and specific serum IgG, and interferon-gamma (IFN-gamma) responses were studied. In experiment 2, four groups of 9, 10, 9, and 9 adult multiparous cows with confirmed infertility problems of diverse aethiology were hormonally synchronized and artificially inseminated with semen containing 0 (a, controls), 10(2) (b), 5 x 10(3) (c), and 5 x 10(5) (d) live N. caninum NC-1 isolate-tachyzoites, respectively. Experimental infection was followed for 63 days. Parasitaemia and specific serum IgG responses were studied.

RESULTS

In experiment 1, parasitaemia was detected in 1, 2, and 3 heifers from groups B, C, and D, respectively, between 9 and 23 days after insemination. Persistent specific serum antibody responses were detected in 2 and 3 heifers from groups D and E, respectively. Transient specific serum antibody responses were detected in 2, 1 and 1 heifers from groups C, D, and E, respectively. In addition, 1 heifer from group B showed a serum-specific antibody level higher than cut off value at 21 days post-insemination. Heifers seroconverted between 23 and 47 days after insemination. Specific IFN-gamma levels were detected in 1, 4, 6, and 3 heifers from groups B, C, D, and E, respectively, between 9 and 55 days after insemination. Pregnancy rate in the control group (60%) was higher than those observed in inoculated heifers (0-42.9%). Pregnancy rates in inoculated heifers were lower when the tachyzoite dose was increased (B 42.9%, C 12.5%, D 11.1%, and E 0%). In experiment 2, no Neospora DNA in blood nor specific serum IgG to N. caninum were detected in any of the cows studied, except in one cow inoculated with 5 x 10(5) tachyzoites (group d) which showed a relative index x100 (RIPC) values of 9.4, 18.9, and 18.1 at 42, 56, and 63 days after insemination, respectively.

CONCLUSIONS

This study provides evidence that the intrauterine infection via contaminated semen using 5 x 10(4) and 5 x 10(5) tachyzoites caused persistent serum-specific antibody responses in some heifers. On the basis of serological data, a dose-response effect was also observed. In addition, N. caninum would be a probable cause of early foetal death in inoculated heifers. In contrast, results obtained in a similar experiment with cows showing confirmed infertility indicate that higher doses, such as of 5 x 10(5) tachyzoites, were necessary to induce seroconversion in at least one animal.

Multimammate rat (Mastomys natalensis), Tristram's jird (Meriones tristrami) and Wagner's gerbil (Gerbillus dasyurus) as laboratory models of acute neosporosis

To test the different sensitivity of rodents of the subfamily Murinae and Gerbillinae, Wagner's gerbils (Gerbillus dasyurus), Tristram's jirds (Meriones tristrami) and multimammate rats (Mastomys natalensis) were inoculated with Neospora caninum tachyzoites. Clinical signs of neosporosis appeared in all inoculated animals. Histopathological examination confirmed the presence of tachyzoites in brains, lungs, skeletal muscle, myocardium, liver, in serosa of stomach and intestines, and in vesicular accessory genital glands. An examination of brains by PCR revealed presence of N. caninum DNA in all experimentally N. caninum infected rodents. The susceptibility of Wagner's gerbils and Tristram's jirds further proved the high sensitivity of gerbiline rodents to the N. caninum infection. The finding of N. caninum tachyzoites in the vesicular accessory genital glands of the infected gerbils suggests the usefulness of the rodent model for demonstration of N. caninum in the male reproductive system. Moreover, the multimammate rat was a susceptible experimental host to be the first immunocompetent rodent of the subfamily Murinae.

Neosporosis, Toxoplasmosis, and Sarcocystosis in Ruminants

Neospora caninum, Sarcocystis spp, and Toxoplasma gondii are related coccidian parasites that can cause abortion and neonatal mortality in animals. In addition, T gondii and certain species of Sarcocystis are zoonotic. This article reviews information on the etiology, diagnosis, control, and prevention of these diseases.

Simulating the impact of four control strategies on the population dynamics of Neospora caninum infection in Swiss dairy cattle

A dynamic deterministic simulation model was developed to assess the impact of different putative control strategies on the seroprevalence of Neospora caninum in female Swiss dairy cattle. The model structure comprised compartments of "susceptible" and "infected" animals (SI-model) and the cattle population was divided into 12 age classes. A reference model (Model 1) was developed to simulate the current (status quo) situation (present seroprevalence in Switzerland 12%), taking into account available demographic and seroprevalence data of Switzerland. Model 1 was modified to represent four putative control strategies: testing and culling of seropositive animals (Model 2), discontinued breeding with offspring from seropositive cows (Model 3), chemotherapeutic treatment of calves from seropositive cows (Model 4), and vaccination of susceptible and infected animals (Model 5). Models 2-4 considered different sub-scenarios with regard to the frequency of diagnostic testing. Multivariable Monte Carlo sensitivity analysis was used to assess the impact of uncertainty in input parameters. A policy of annual testing and culling of all seropositive cattle in the population reduced the seroprevalence effectively and rapidly from 12% to <1% in the first year of simulation. The control strategies with discontinued breeding with offspring from all seropositive cows, chemotherapy of calves and vaccination of all cattle reduced the prevalence more slowly than culling but were still very effective (reduction of prevalence below 2% within 11, 23 and 3 years of simulation, respectively). However, sensitivity analyses revealed that the effectiveness of these strategies depended strongly on the quality of the input parameters used, such as the horizontal and vertical transmission factors, the sensitivity of the diagnostic test and the efficacy of medication and vaccination. Finally, all models confirmed that it was not possible to completely eradicate N. caninum as long as the horizontal transmission process was not interrupted.

Diagnosis of bovine neosporosis

The protozoan parasite Neospora caninum is a major cause of abortion in cattle. The diagnosis of neosporosis-associated mortality and abortion in cattle is difficult. In the present paper we review histologic, serologic, immunohistochemical, and molecular methods for dignosis of bovine neosporosis. Although not a routine method of diagnosis, methods to isolate viable N. caninum from bovine tissues are also reviewed.

Pathogenesis of bovine neosporosis

The protozoan parasite Neospora caninum is a major pathogen of cattle and dogs, being a significant cause of abortion in cattle in many countries. It is one of the most efficiently transmitted parasites, with up to 90% of cattle infected in some herds. The pathogenesis of abortion due to Neospora is complex and only partially understood. Losses occur after a primary infection during pregnancy but more commonly as the result of recrudescence of a persistent infection during pregnancy. Parasitaemia is followed by invasion of the placenta and fetus. It is suggested that abortion occurs when primary parasite-induced placental damage jeopardises fetal survival directly or causes release of maternal prostaglandins that in turn cause luteolysis and abortion. Fetal damage may also occur due to primary tissue damage caused by the multiplication of N. caninum in the fetus or due to insufficient oxygen/nutrition, secondary to placental damage. In addition, maternal immune expulsion of the fetus may occur associated with maternal placental inflammation and the release of maternal pro-inflammatory cytokines in the placenta. Thus N. caninum is a primary pathogen capable of causing abortion either through maternal placental inflammation, maternal and fetal placental necrosis, fetal damage, or a combination of all three. The question of how N. caninum kills the fetus exposes the complex and finely balanced biological processes that have evolved to permit bovine and other mammalian pregnancies to occur. Defining these immunological mechanisms will shed light on potential methods of control of bovine neosporosis and enrich our understanding of the continuity of mammalian and protozoal survival.

Artificial insemination of cows with semen in vitro contaminated with Neospora caninum tachyzoites failed to induce neosporosis

Neosporosis is a major cause of abortion in cattle all over the world. Congenital transmission as well as horizontal transmission by ingestion of oocysts has been described. The detection of Neospora caninum DNA in bull semen warrants the investigation of possible transmission through the use of contaminated semen. In this experiment four cows were artificially inseminated with frozen-thawed semen contaminated in vitro with viable N. caninum tachyzoites (group A) and four control cows were inseminated with tachyzoites-free frozen-thawed semen, from the same bull (group B). Serum samples were collected 15 days before the artificial insemination (AI) and at days 10, 14, 21, 28, 45, 60 and 75 post-insemination. All sera samples were tested for neosporosis by direct agglutination test (DAT). Three of the cows from group A had negative DAT titers (< or =1:20) in all of the samples, while the fourth cow from this group had a low titer of antibodies (1:80) at day 10, and became negative at day 45, suggesting a stimulation of the immune system by the tachyzoites placed in uterus, rather than the induction of an infection. All of the cows from group B had negative DAT titers (< or =1:20) in all of the samples. These results suggest that transmission of neosporosis by artificial insemination with frozen-thawed semen is an unlikely event.

Diagnosis of bovine neosporosis: Recent advances and perspectives

Neospora caninum is considered a major cause of abortion in cattle. Appropriate techniques for diagnosis of bovine neosporosis, both in vivo and in aborted foetuses, have been developed in the last ten years and some of them are commercially available. For diagnosis in live animals, detection of antibodies in serum or milk has been shown to be the best option both at the herd and the individual level. These techniques are excellent tools to examine N. caninum-associated abortion problems and to adopt some basic herd-control measures. Concerning foetal diagnosis, detection of compatible lesions by histological examination and parasites by PCR in brain (as well as heart and liver) are the best choices. Diagnostic criteria to distinguish foetal infection and Neospora-associated abortion are based not only on the demonstration of the parasite in the foetus but also on the extent and severity of the lesions in the foetus, foetal age and the assessment of neosporosis at the herd level. In the near future, new tools to diagnose infection should help to detect animals with parasite reactivation by testing the immune response to stage-specific antigens and lead to the development of molecular typing methods to characterise different parasite isolates. Finally, uniform diagnostic procedures need to be established between laboratories and countries in order to standardise result interpretation. The role of National or Regional Reference Laboratories is essential in countries or regions where control programmes for the disease are being developed.

Intrauterine Neospora caninum inoculation of heifers

Here, we studied the potential of Neospora caninum tachyzoites to infect heifers when administered in utero by artificial insemination via contaminated semen. Eighteen primiparous cyclic heifers were hormonally synchronized and artificially inseminated. Nine of them, which were inseminated with semen containing 10(7) live N. caninum NC-1 isolate-tachyzoites, reacted with seroconversion and a specific IFN-gamma response. Moreover, N. caninum DNA was demonstrated by a nested-PCR in the blood of all nine heifers and in brain, lungs, liver and uterine horn of several of them. In contrast, nine heifers inseminated with tachyzoite-free semen developed no antibody or IFN-gamma responses, and no parasite DNA was detected in blood or organs. At necropsy, viable embryos were detected in one and six of the infected and non-infected heifers, respectively. No specific Neospora DNA was detected in any of the embryos. This study provides evidence that intrauterine inoculation via contaminated semen cause N. caninum infection in cattle.

Detection of Neospora caninum in the semen and blood of naturally infected bulls

A prospective study was designed to investigate the presence of Neospora caninum in semen and blood of eight bulls seropositive to N. caninum using nested-PCR procedures. Positive semen and blood samples were bioassayed in a BALB/c nu/nu mouse model. Specific anti-N. caninum serological and interferon-gamma (IFN-gamma) responses were also studied. In parallel, five seronegative bulls acted as non-infected controls. All bulls were located in a collaborating AI centre and monitored for 22 weeks. Six of eight seropositive bulls showed N. caninum DNA in their semen and/or blood samples at some time during the course of the study. In all positive semen samples, we consistently found Neospora-DNA in the cell fraction and not in seminal plasma. Parasite load, as determined by a real-time PCR in nested-PCR positive semen samples, ranged from 1 to 10 parasites/ml. We found no association between the presence of N. caninum DNA in semen and blood. N. caninum could not be detected in the BALB/c nu/nu mice inoculated with PCR-positive semen or blood samples. Specific IgG antibody levels in seropositive bulls fluctuated over time, at times falling below cut-off level. The response was predominantly IgG2, with significant differences compared to control bulls (P < 0.05). The overall mean specific IFN-gamma response in seropositive bulls was also higher than those observed in the control group (P < 0.05), although extensive variation in individual responses was observed among bulls and over time. No significant association was found between bulls showing Neospora DNA in semen, blood, or both, and specific IgG, IgG1, IgG2, IgM and IgA levels or IFN-gamma response. This study is the first to report the presence of Neospora DNA in semen and blood of naturally-infected bulls. Our observations indicate intermittent presence of N. caninum in blood and semen and shedding in semen in low numbers.

Occasional detection of Neospora caninum DNA in frozen extended semen from naturally infected bulls

Recently, the presence of Neospora caninum DNA in semen from naturally infected bulls was reported. In the present work, the presence and quantification of N. caninum by PCR techniques in frozen extended semen straws from naturally infected bulls was investigated. A total of 20 seropositive and five seronegative bulls raised for reproductive purposes in an AI centre were used. Ten extended semen straws from each bull obtained at different time-points during the previous 2 years were selected for Neospora testing. Eight of the seropositive bulls (40%) studied showed at least one positive straw to N. caninum DNA and 14 of their 180 semen straws examined (7.8%) were found to be positive. In all positive samples, N. caninum DNA was consistently detected in the cell fraction and not in the seminal plasma. However, the parasite number in each positive straw was under the detection level of real-time PCR. In parallel, 10 semen straws from each of the five seronegative bulls were also analyzed by the nested-PCR and no N. caninum DNA products were obtained. In order to check the consistent presence of N. caninum in a positive semen batch, three additional semen straws from the same batch of each positive straw from three seropositive bulls were analyzed but N. caninum DNA was only detected in one straw from one bull. In conclusion, we report the sporadic detection of N. caninum DNA in semen straws of naturally infected bulls but the low frequency of contaminated semen straws and the low parasite load observed indicate a minor chance of bovine neosporosis transmission by AI.

Neospora caninum: Quantification of DNA in the blood of naturally infected aborted and pregnant cows using real-time PCR

This study quantified Neospora caninum DNA in the blood and brain of pregnant and aborted heifers by monitoring PCR product formation in real-time using SYBR Green I, a double-stranded DNA-binding dye. Primers were designed to amplify a 188 bp product specific to N. caninum from the Nc-5 gene fragment of N. caninum. Similarly, a 71 bp product was amplified from the 28S rRNA gene of bovine genomic DNA that served as a control. Agarose gel electrophoresis and analysis of the melting curve for PCR products showed that both primer pairs were specific to their targets. Standard curves were generated for both bovine and N. caninum genomic DNA, and were used to compute the relative concentration of parasite to bovine DNA in the test samples. The concentration of N. caninum DNA in 1 ng of bovine genomic DNA obtained from blood ranged between 0.097 ng at the 1st week of the observation and 0 ng at the 15th week in aborted cows. In pregnant cows, the values ranged between 0.080 ng at the 1st week and 0.155 ng at the 15th week of observation. There was a sustained decrease of DNA concentration in the aborted group after abortion and an increase in DNA concentration in the pregnant group. Comparison of parasite DNA in blood and brain of infected heifers showed a higher DNA concentration in brain than in blood. This study shows that N. caninum DNA can be quantified to obtain the relative concentration of parasite DNA to host genomic DNA in blood. This technique allows testing of a large number of samples at one time and can be done without the need for slaughter of tested animals.

Neospora caninum infection in breeder bulls: seroprevalence and comparison of serological methods used for diagnosis

AIMS

To investigate the seroprevalence of Neospora caninum infection in breeder bulls. In addition, the level of agreement of serological methods used was evaluated.

METHODS

A total of 285 bulls of different ages and breeds raised for reproductive purposes in Spain were sampled for serum antibody activity to N. caninum. Sera were tested using three validated assays: the indirect fluorescent antibody test (IFAT) and two commercially available enzyme-linked immunosorbent assays (ELISA).

RESULTS

Antibodies to N. caninum were found in 13.7% of bulls sampled by at least one of the three validated serological assays. The seroprevalence of neosporosis oscillated between 11.2 and 13.3% depending on the serological technique used. No significant associations (P > 0.05) were observed between N. caninum infection and bull breed or age. The serum antibody levels were predominantly low and close to threshold levels in all positive samples. A very good agreement was found among the serological methods used.

CONCLUSIONS

This is the first seroprevalence study of bovine neosporosis in breeder bulls and results showed a moderate presence of N. caninum chronic infections.

The use of PCR to detect Neospora caninum DNA in the blood of naturally infected cows

Twelve 2-year old heifers in their fifth month of gestation when pregnancy tested were used in this study. Six heifers aborted at approximately 4 months of gestation and had blood samples drawn less than 6 weeks after the abortions were identified. Blood samples were also drawn from three sero-positive pregnant and three sero-negative pregnant heifers. DNA was isolated from the samples and a 350 bp fragment of the Nc-5 gene was PCR amplified using primer pair Np21+ and Np6+. Also, the Internal Transcribed Spacer 1 (ITS1) was PCR amplified using Tim 3 and Tim 11 primer pair. The Nc-5 gene fragment was cloned, sequenced and the sequence BLAST-tested. Similarly, the ITS1 product was sequenced and BLAST-tested. The BLAST test results revealed that Neospora caninum DNA was present in these blood samples indicating that polymerase chain reaction can be used in the detection of N. caninum DNA in the blood of sero-positive cows.