Shedding of Neospora caninum oocysts by dogs fed tissues from naturally infected water buffaloes (Bubalus bubalis) from Brazil

Seroprevalence of Neospora caninum and risk factors associated with infection in water buffaloes (Bubalus bubalis) from Maranhão State, Brazil

The aim of this work was to determine the seroprevalence of Neospora caninum in buffaloes (Bubalus bubalis) from Maranhão State, Brazil, and identify risk factors associated with infection. In total, 338 buffaloes of different ages and both sexes from four farms were randomly selected. Information about the study region, animals and management was collected using an epidemiological questionnaire. Sera were subjected to an indirect fluorescent antibody test (IFAT) to detect anti-N caninum antibodies, while N. caninum DNA was detected using the polymerase chain reaction (PCR) assays. The overall seroprevalence of N. caninum in buffaloes was 27.5% (93/338), while DNA was detected in 3.0% (3/101) samples. The proportion of positive animals detected by IFAT and PCR simultaneously was 2.6% (2/77). The risk factors for N. caninum infection were contact with fomites (p = 0.022), management conditions (p = 0.005), calving interval of 20 months (p = 0.010) and deworming management (application 3 times a year in adults and calves, p = 0.020; change of anthelmintic group, p = 0.040). By multivariate analysis, management conditions was a risk factor for N. caninum infection with odds ratio of 2.2 (95% CI 1.0-4.6). This is the first report of the prevalence and risk factors for neosporosis in B. bubalis of Maranhão State, Brazil. Thus, N. caninum is widely distributed in buffalo herds in Maranhão, with management conditions being a risk factor for infection. Further studies should be conducted to elucidate the importance of buffaloes in the epidemiology of neosporosis in Maranhão State.

Serosurveillance and risk factors for Neospora caninum infection in water buffaloes (B. bubalis) from central and southern Mexico

The water buffalo (B. bubalis) is an alternative to cattle ranching in several regions of southern Mexico. Here we report seroprevalence and risk factors associated with the protozoan parasite, Neospora caninum, in water buffaloes in six buffalo production units, in municipalities from central and southern Veracruz, Mexico. Antibodies to N. caninum were assessed in serum samples of 543 buffaloes by a commercial ELISA-kit, and 44.8% (243/543; 95% CI 40.5-49.0) were seropositive. Questionnaires were used to collect epidemiological data and to identify risk factors associated with N. caninum infection. Data analysis indicated that older buffaloes (≥7 year) exhibited the highest seroprevalence for neosporosis 62.3% (38/61; 95% CI 49.7-73.4) (P ≤ 0.05). Buffaloes that were in close contact with cattle had higher seroprevalence 47.6% (168/353; 95% CI 42.3-52.9) (P < 0.01) than those that were not in contact 36.8% (70/190; 95% CI 30.0-44.1). Our findings provide important information to implement preventive measures in the buffalo farms.

A Review of Toxoplasmosis and Neosporosis in Water Buffalo (Bubalus bubalis)

Toxoplasmosis and neosporosis are diseases with worldwide distribution that are associated with reproductive problems in livestock and responsible for economic losses. This review presents an overview of the current knowledge relative to these diseases in water buffalo (Bubalus bubalis). In general, buffalo are considered resistant to clinical toxoplasmosis because there are studies only reporting serological evidence of natural infection in these animals. Studies have described age, poor hygienic status of the farm, and presence of cats as risk factors for the development of Toxoplasma gondii infection in buffalo. It must be highlighted that buffalo meat, which does not receive adequate freezing treatment, could be a potential source for toxoplasmic human infection as well as the importance of raw buffalo milk in the transmission of toxoplasmosis to human beings. Neospora caninum is considered one of the major causes of abortion and responsible for huge economic losses in cattle. Vertical transmission is the main route to infect calves, and is responsible for maintaining the parasite within a herd. In buffalo, vertical transmission is also described; moreover, although there are indications that N. caninum may be associated with abortion in dairy buffalo, the reproductive importance of neosporosis is apparently lower in buffalo relative to cattle. Most studies have identified a higher time of exposition to N. caninum oocysts relative to age. The household system was also described as a risk factor for infection, possibly due to persistent contact between the home-raised buffalo and canids. The fetal immune competence of buffalo is similar to bovine, and buffalo fetus are highly susceptible to infection during the first trimester of pregnancy, indicating that N. caninum may be an abortigenic agent in buffaloes. Alternatively, it is interesting to note there is evidence that the inflammatory response in pregnant buffalo infected with N. caninum is mild enough to avoid abortion in most cases. It is proposed that the possible transmission of toxoplasmosis through unprocessed milk and buffalo meat may occur, which is important in terms of public health. Additionally, there is strong evidence to suggest that N. caninum may be associated with abortion in buffalo.

Evidence of Neospora caninum infection in buffaloes (Bubalus bubalis) from Northwestern Romania

Neospora caninum is a heteroxenous parasitic Apicomplexan protozoan, able to infect a variety of domestic and wild animals, mainly associated with reproductive disorders and abortions in susceptible species. Considering the importance of Romania in the European buffalo industry and the severe economic losses caused by N. caninum infection in livestock, the aim of the present study was to assess the occurrence of neosporosis in buffaloes raised in household and farming systems in northwestern Romania. Overall, 197 serum samples were tested for the presence of N. caninum-specific antibodies by ELISA. Additionally, from 74 slaughtered buffaloes, diaphragm digest, heart, and lymph node samples were tested for the presence of N. caninum DNA. The overall seroprevalence was 68.5%. The seroprevalence was significantly higher in adult animals compared to calves and young ones and in the household system compared to farm. By nPCR, six samples were found to be positive for N. caninum DNA, of which three were serologically negative. The present study reveals a high prevalence of N. caninum-specific antibodies in buffaloes in northwestern Romania and to our best knowledge, it is the first one performed in Romania.

Neospora caninum in birds: A review

Neospora caninum is an obligate intracellular protozoan parasite that infects domestic and wild animals. Canids are considered to be definitive hosts since they may shed oocysts into the environment through their feces. The disease is recognized as one of the major causes of bovine abortion worldwide, leading to important economic losses in the dairy and beef cattle industries. Previous studies have reported N. caninum infection in different species of birds; infection in birds has been associated with increased seroprevalence and reproductive problems in dairy cattle. Although the role of birds in the epidemiological cycle of neosporosis is unknown, birds are exposed to infection because they feed on the ground and could thus contribute to parasite dissemination. This review is focused on the current state of knowledge of neosporosis in birds.

Diagnostic accuracy of enzyme-linked immunosorbent assay (ELISA) and immunoblot (IB) for the detection of antibodies against Neospora caninum in milk from dairy cows

The aim of the study was to estimate the sensitivity and specificity of enzyme-linked immunosorbent assay (ELISA) and immunoblot (IB) for detecting antibodies of Neospora caninum in dairy cows, in the absence of a gold standard. The study complies with STRADAS-paratuberculosis guidelines for reporting the accuracy of the test. We tried to apply Bayesian models that do not require conditional independence of the tests under evaluation, but as convergence problems appeared, we used Bayesian methodology, that does not assume conditional dependence of the tests. Informative prior probability distributions were constructed, based on scientific inputs regarding sensitivity and specificity of the IB test and the prevalence of disease in the studied populations. IB sensitivity and specificity were estimated to be 98.8% and 91.3%, respectively, while the respective estimates for ELISA were 60% and 96.7%. A sensitivity analysis, where modified prior probability distributions concerning IB diagnostic accuracy applied, showed a limited effect in posterior assessments. We concluded that ELISA can be used to screen the bulk milk and secondly, IB can be used whenever needed.

All about neosporosis in Brazil

Neospora caninum is protozoan parasite with domestic and wild dogs, coyotes and grey wolves as the definitive hosts and many warm-blooded animals as intermediate hosts. It was cultivated and named in 1988. Neosporosis is a major disease of cattle and has no public health significance. Since 1990's N. caninum has emerged as a major cause of abortion in cattle worldwide, including in Brazil. N. caninum also causes clinical infections in several other animal species. Considerable progress has been made in understanding the biology of N. caninum and there are more than 200 papers on this subject from Brazil. However, most of the reports on neosporosis from Brazil are serological surveys. Overall, little is known of clinical neosporosis in Brazil, particularly cattle. The few reports pertain to sporadic cases of abortion with no information on epidemics or storms of abortion. The objective of the present review is to summarize all reports from Brazil and suggest topic for further research, including prevalence of N. caninum oocysts in soil or in canine feces, and determining if there are additional definitive hosts, other than the domestic dog. There is need for a national survey in cattle using defined parameters. Future researches should focus on molecular characterization of N. caninum strains, possibility of vaccine production and relationship between wildlife and livestock epidemiology.

Development of a loop-mediated isothermal amplification technique and comparison with quantitative real-time PCR for the rapid visual detection of canine neosporosis

Background

Dogs are the definitive hosts of Neospora caninum and play an important role in the transmission of the parasite. Despite the high sensitivity of existing molecular tools such as quantitative real-time PCR (qPCR), these techniques are not suitable for use in many countries because of equipment costs and difficulties in implementing them for field diagnostics. Therefore, we developed a simplified technique, loop-mediated isothermal amplification (LAMP), for the rapid visual detection of N. caninum.

Methods

LAMP specificity was evaluated using a panel containing DNA from a range of different organisms. Sensitivity was evaluated by preparing 10-fold serial dilutions of N. caninum tachyzoites and comparing the results with those obtained using qPCR. Assessment of the LAMP results was determined by recognition of a colour change after amplification. The usefulness of the LAMP assay in the field was tested on 396 blood and 115 faecal samples from dogs, and one placenta from a heifer collected in Lopburi, Nakhon Pathom, Sa Kaeo, and Ratchaburi provinces, Thailand.

Results

Specificity of the LAMP technique was shown by its inability to amplify DNA from non-target pathogens or healthy dogs. The detection limit was the equivalent of one genome for both LAMP and qPCR. LAMP and qPCR detected positive N. caninum infection in 15 of 396 (3.8%) blood samples; LAMP detected 9/115 (7.8%) positive faecal samples, while qPCR detected 5/115 (4.3%) positive faecal samples. The placental tissue was shown to be positive by both techniques. Agreement between LAMP and qPCR was perfect in blood samples (kappa value, 1.00) and substantial in faecal samples (kappa value, 0.697).

Conclusions

This is the first known LAMP assay developed for the amplification of N. caninum. The technique effectively and rapidly detected the parasite with high sensitivity and specificity and was cost-effective. This assay could be used in the field to confirm the diagnosis of canine or bovine neosporosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2330-2) contains supplementary material, which is available to authorized users.

Isolation and biological and molecular characterization of Neospora caninum (NC-SP1) from a naturally infected adult asymptomatic cattle (Bos taurus) in the state of São Paulo, Brazil

The biological and genetic diversity of Neospora caninum is very limited because of availability of only a few viable isolates worldwide. This study describes the isolation and biological and molecular characterization of a new viable isolate of N. caninum (NC-SP1), from a cattle in Brazil. Approximately 400 g of brain from a naturally infected adult male cattle from an abattoir was fed to a 2-month-old dog. Neospora-like oocysts were observed on day 7 post-inoculation (PI) and the duration of oocyst shedding was 14 days. The DNA obtained from oocysts was characterized molecularly and the final sequence was 99% identical to homologous sequences of N. caninum available in GenBank®. For bioassay, gerbils (Meriones unguiculatus) were orally inoculated with 10 100 and 1000 oocysts; all gerbils remained clinically normal but developed N. caninum antibodies 14 days PI. Cell culture isolation was successful using the brain homogenate from one of the gerbils and tachyzoites were observed 24 days PI. Microsatellite genotyping revealed a unique genetic profile for this new reference isolate.

Gallus gallus domesticus are resistant to infection with Neospora caninum tachyzoites of the NC-1 strain

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Neospora caninum may have been eliminated by the hens.

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The infected animals from different groups exhibited no changes in weight gain and feed intake.

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The tachyzoite infection does not appear to be appropriate to induce chronic infections in hens.

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The infection susceptibility in birds “in ovo” appears to be distinct in adult animals.

The aim of this study was to experimentally evaluate infection in Gallus gallus domesticus with Neospora caninum tachyzoites of the NC-1 strain. Experimental infection was conducted in 90-day-old chickens, embryonated eggs and bioassays in dogs. In the first experiment, poults were randomly divided into four groups. Groups I and II were provided feed with coccidiostat, whereas groups III and IV received feed without coccidiostat. When the poults from groups I and III reached 90 days of age, they received a subcutaneous inoculation of N. caninum. Once the hens entered their egg-laying period, during the following 30 days, the eggs were collected, identified, weighed and placed in an incubator. On the 70th day after inoculation, all animals, including the chicks, were euthanized. Tissue samples from the adult poultry and chicks were collected for histopathology, immunohistochemistry (IHC) and PCR. Brain tissue and pectoral muscle samples from infected birds were fed to two dogs. Notably, the average weight of the group III eggs was lower than that of the group IV eggs (p < 0.05). No changes consistent with infection in adult poultry or chicks were detected by histopathology or IHC; moreover, no amplified parasite DNA was detected in the birds’ tissues or dogs’ feces. No dog eliminated oocysts. In the second experiment, the embryonated chicken eggs were inoculated with 1 × 10²N. caninum tachyzoites, on the 10th day of incubation, and chicks born from these eggs were housed in boxes suitable for the species and received commercial feed and distilled water ad libitum. On the 30th day after infection (DAI), the poultry were euthanized, and their organs were processed as described in experiment I. The amplification of parasite DNA was observed in the spleen and pectoral muscles of one of the birds. The ingestion of bird tissues by dogs did not result in oocyst elimination. These results indicate that the parasite may have been eliminated by the host and that the use of tachyzoites to induce chronic disease might be a poor source for hens.

Risk factors for Toxoplasma gondii and Neospora caninum seropositivity in buffaloes in Paraiba State, Brazil

Abstract The aims of this survey were to determine the frequency of anti-Toxoplasma gondii and anti-Neospora caninum antibodies and to identify the risk factors associated with seropositivity among buffaloes in the state of Paraíba, Brazil. This survey included 136 buffaloes belonging to 14 herds. To detect anti-T. gondii and anti-N. caninum antibodies, the indirect fluorescent antibody test (IFAT) was used. Among the 136 samples analyzed, 17 (12.5%) were positive for anti-T. gondii antibodies with titers ranging from 64 to 1,024, and 26 (19.1%) for anti-N. caninum with titers from 200 to 1,600. Animals seropositive for both T. gondii and N. caninum were found in 10 of the 14 herds (71.4%). Semi-intensive management systems (odds ratio = 2.99) and presence of pigs (odds ratio = 4.33) were identified as risk factors for T. gondii and N. caninum, respectively. It can be suggested that T. gondii and N. caninum are widespread in buffaloes in Paraíba, and that additional surveys are needed in order to ascertain the importance of these agents for this species and for pigs, and the influence of the farming type on occurrences of seropositive animals.

A review of Neospora caninum in water buffalo (Bubalus bubalis)

A number of countries in the world have reported infections with Neospora caninum in water buffalo (Bubalus bubalis), from Africa to Asia, Europe and South America and recently Australia. In general, clinical manifestations (such as abortion) seem rare, which has raised the prospect that buffalo may be inherently resistant to clinical effects of N. caninum infection. Worldwide, the seroprevalence of N. caninum infection (as a measure of exposure determined by the detection of antibody) in buffalo is high, at approximately 48%. This reported seroprevalence is three or four times higher than that reported from the world's cattle populations, which have collective seroprevalence rates of 16.1% for dairy cattle and 11.5% for beef cattle. However, there is a lack of standardisation in seroprevalence studies and some studies may well under-estimate the true level of infection. Epidemiologic evidence supports post-natal transmission, and in utero transmission has also been demonstrated. The causes for water buffalo to have markedly higher seroprevalence but apparently lower neosporosis abortion rates than cattle warrant further investigation.

Abortion and foetal lesions induced by Neospora caninum in experimentally infected water buffalos (Bubalus bubalis)

The water buffalo (Bubalus bubalis) is an important species in several countries for its milk and meat production, as well as for transport and other agricultural activities. It is, in general, considered more resistant than cattle to different parasitic diseases, also less demanding for forage quality. It has been postulated that buffalo may be resistant to abortion caused by neosporosis, because of high serological prevalences found in buffalo herds from different localities, with no description of Neospora caninum-related abortion. Recent studies have demonstrated the potential impact of neosporosis in pregnant water buffalo cows. In this work, three pregnant buffalo cows were experimentally infected with Nc-1 strain of N. caninum, and abortion was detected 35 days post-infection. Molecular and histopathological results found in post-mortem tissues are described and discussed, confirming the susceptibility of water buffalos to abortion caused by N. caninum.

Neospora caninum serostatus is affected by age and species variables in cohabiting water buffaloes and beef cattle

The aim of this study was to investigate how Neospora caninum serostatus may be affected by variables such as host species (water buffaloes or cattle) and age in animals cohabiting in the same ranch. A convenience cross-sectional study was performed on four ranches in the Northeast of Argentina, where water buffalo are cohabitating with beef cattle. Blood samples were collected from 1350 female water buffaloes (Bubalus bubalis) and 880 female beef cattle (Bos taurus and Bos indicus crossbreeds) from four ranches. Calving and weaning percentages at herd level for each ranch were also recorded. N. caninum antibody levels were measured by an indirect fluorescent antibody test (IFAT) (reciprocal antibody titers ≥ 100). Serological results were classified into 2 categories (0: negative; 1: positive). A logistic regression model was used to describe the relationship between N. caninum serostatus and specie (water buffalo or cattle), age or ranch and their interactions. Likelihood ratio tests were used to assess the significance of the model and their terms. Odds ratios were estimated and 95% profile likelihood (LR) and Wald confidence intervals (CI) obtained. Overall, specific antibody titers were found in 43.3% (584/1350) of water buffaloes and 28.6% (252/880) of cattle. Seropositive water buffaloes and cattle were observed on all ranches. Age was statistically significant (p=0.01) with an overall estimate of logit (log odds) of age of 0.03 for both species. This indicates that for every one year increase in age, the expected change in log odds of being seropositive increased by 0.03. On three of four ranches a water buffalo was 4.48, 1.54 and 2.25 times more likely to be seropositive than cattle for animals of the same age. The N. caninum serostatus was affected by age in the first place, but also by species on at least three of the four ranches. Calving and weaning percentages were higher in water buffaloes than in beef cattle (p<0.05). Even though the low pathogenicity that N. caninum seems to have in water buffaloes, this study reinforces the importance of this specie as maintenance of the disease.

Control options for Neospora caninum--is there anything new or are we going backwards?

Recent work has highlighted and enumerated the economic annual losses due to Neospora caninum abortions worldwide, which should provide strong motivation for the control of bovine neosporosis. However, with the recent withdrawal from sale of the only commercially available vaccine, control options for N. caninum have become more restricted. While researchers continue to work on developing alternative efficacious vaccines, what are the control options presently available for the cattle industries? At the practical level, recommendations for 'Test-and-cull', or 'not breeding from seropositive dams' stand diametrically opposed to alternative options put forward that suggest a primary producer is better advised to keep those cows in the herd that are already seropositive, i.e., assumed to be chronically infected, and indeed those that have already aborted once. Treatment with a coccidiostat has been recommended as the only economically viable option, yet no such treatment has gained official, regulatory approval. Dogs are central to the life cycle of N. caninum and have repeatedly been associated with infection and abortions in cattle by epidemiological studies. Knowledge and understanding of that pivotal role should be able to be put to use in control programmes. The present review canvasses the relevant literature for evidence for control options for N. caninum (some of them proven, many not) and assesses them in the light of the authors' knowledge and experience with control of N. caninum.

Molecular identification of Neospora caninum from calf/foetal brain tissue and among oocysts recovered from faeces of naturally infected dogs in southern Ethiopia

This study sought to confirm and investigate further recently published information regarding the occurrence of Neospora caninum in cattle in Ethiopia and investigate infection in dogs, the canine definitive host, in this region. Faecal samples from 383 dogs in Hawassa, Ethiopia were examined by microscopy for Neospora-like oocysts, and positive samples then analysed by a molecular approach (DNA isolation, PCR and sequencing at the ITS1 gene). Brain tissue samples from four late term aborted foetuses, one congenitally defective calf (hind leg arthrogryposis) and placental tissue from cattle in the same area were also examined by the same molecular approach. All foetal, calf and placental tissue were associated with Neospora seropositive dams. A high prevalence of Neospora-like oocysts (11.5 μm±1.5 μm diameter) was observed in faecal samples from dogs (37 positive samples; 9.7% prevalence), and in 17 of these the identification was confirmed by PCR, giving a prevalence of confirmed infection of 4.4%. N. caninum DNA was also detected in all foetal and calf brain tissue samples. Sequencing revealed only minor differences among all PCR products, whether from oocysts or from brain tissue samples. These data provide molecular evidence of the presence of N. caninum infection in both dog and cattle in this region of Ethiopia. Moreover these findings highlight the role of dogs in maintaining and spreading the infection horizontally in the study area. The high frequency of N. caninum infection in household dogs as well as farm dogs is worthy of further investigation.

Assessment of experimental infection for dogs usingGallus gallus chorioallantoic membranes inoculated withNeospora caninum

The aim of this study was to evaluate parasitism kinetics and tissue lesions in the first week of infection by Neospora caninum in dogs fed Gallus gallus chorioallantoic membranes (CMs) previously infected in ovo. Five two-month-old pups were used. Each dog was given five CMs that were previously infected with N. caninum via the oral route. Four animals were euthanized in the first week of infection. All four dogs had their stools examined one week prior to and up to the day they were euthanized. The stools of the uneuthanized dog were collected for 30 days. After euthanasia, organ sections were utilized for histopathology, immunohistochemistry, indirect immunofluorescent tissue reactions, PCR and real-time PCR to detect parasites. Necropsy revealed that the small and large intestines, spleen, and lungs were affected. No oocysts orN. caninum DNA were identified in the stool samples. Real-time PCR was the most sensitive technique used to detect the protozoa in tissues, which were identified in 41% of the analyzed samples. Our results indicate that an experimental model using previously infected CMs appears to be a useful model for the study of the host-parasite relationship during the infection's acute phase.

Neospora spp. antibodies in horses from two geographical regions of the state of Santa Catarina, Brazil

The aims of this study were to determine occurrences ofNeospora spp. IgG antibodies in horses from two geographical regions of the state of Santa Catarina, southern Brazil, and identify risk factors for infection. Analyses were performed on 615 samples using the immunofluorescent antibody test (IFAT ≥ 1:50). Out of the 615 samples, 25 (4.1%) were positive for Neospora spp. The titers for Neospora spp. were distributed as follows: 1:50 (13), 1:100 (eight), 1:200 (three) and 1:400 (one). Out of the 311 samples taken in the mountain region, eight were positive (2.6%). Among the samples from the coastal region (304), 17 had Neospora spp. antibodies, thus indicating occurrence of 5.6%. Although no statistically significant difference was observed (P = 0.06704), the prevalence among animals of the coast was 2.2 times higher than that of the mountain region. Contact with dogs and/or cattle (P = 0.007596) were identified as risk factor forNeospora spp. infection.

Clinical outcome and vertical transmission variability among canine Neospora caninum isolates in a pregnant mouse model of infection

We compared the clinical outcome and vertical transmission of six canine Neospora caninum isolates using a pregnant BALB/c model. Four of the isolates were obtained from oocysts of naturally infected dogs (Nc-Ger2, Nc-Ger3, Nc-Ger6 and Nc-6Arg) and two were from diseased dogs with neurological signs (Nc-Bahia and Nc-Liv). The dams were inoculated with 2×106 tachyzoites of each isolate at day 7 of pregnancy. Morbidity, mortality and the antibody responses were evaluated in both the dams and the offspring, as was parasite transmission to the progeny. The mortality rates varied from 100% in Nc-Bahia and Nc-Liv-infected pups to 19% or less for those infected with the isolates from oocysts. The vertical transmission rates varied from 9 to 53% for N. caninum from oocysts, compared with 100% for the Nc-Liv and Nc-Bahia isolates. All dams showed specific IgG responses against tachyzoite and rNc-GRA7 antigens, confirming Neospora infection. The highest IgG levels were detected in mice inoculated with the Nc-Liv and Nc-Bahia isolates. These results demonstrate marked differences in virulence between the N. caninum isolates obtained from oocysts and neurologically affected dogs. This variability could help us to explain the differences in the outcome of the infection in definitive and intermediate hosts.

Prevalence and risk factors associated with Neospora caninum infection in dairy herds in Jordan

A cross-sectional study was carried out to determine the seroprevalence and to identify risk factors associated with Neospora caninum infection in 62 dairy herds (n = 671 cows) in Jordan between January and June 2007. Information regarding herd management was recorded through personal interviews with farmers. Antibodies against N. caninum were detected using an indirect ELISA test. Chi-square analysis and multivariable logistic regression model were used to identify risk factors associated with N. caninum seropositivity. The true prevalence of antibodies against N. caninum in individual cows and cattle herds was 35 and 66.5 %, respectively. There was no significant difference in the percentage of seropositive animals between different age groups. Multivariable logistic regression model revealed workers frequently visiting nearby farms as a risk factor for seropositivity to N. caninum, while presence of a calving pen was suggested as a protective factor. Amman, Balqa, and Mafrak governorates had significantly lower seroprevalence to N. caninum compared to other Jordanian governorates. Results of this study indicated that N. caninum infection may be widespread in Jordan.

Experimental inoculation of Neospora caninum in pregnant water buffalo

The aim of this study was to characterize the pathogenesis of Neospora caninum in experimentally inoculated pregnant water buffalo (Bubalus bubalis). Twelve Mediterranean female water buffaloes ranging in age from 4 to 14 years old and seronegative to N. caninum by indirect fluorescent antibody test (IFAT) were involved. Ten females were intravenously inoculated with 10(8) tachyzoites of NC-1 strain at 70 (n=3) or 90 (n=7) days of pregnancy (dp). Two control animals were inoculated with placebo at 70 and 90 dp, respectively. Serum samples were obtained weekly following inoculation to the end of the experiment. Three animals inoculated at 70 dp were slaughtered at 28 days post inoculation (dpi), three animals inoculated at 90 dp were slaughtered at 28 dpi and the remaining four animals inoculated at 90 dp were slaughtered at 42 dpi. Fetal fluids from cavities and tissue samples were recovered for IFAT and histopathology, immunohistochemistry and PCR, respectively. Genomic DNA from fetal tissues was used for parasite DNA detection and microsatellite genotyping in order to confirm the NC-1 specific-infection. Dams developed specific antibodies one week after the inoculation and serological titers did not decrease significantly to the end of the experiment. No abortions were recorded during the experimental time; however, one fetus from a dam inoculated at 70 dp was not viable at necropsy. Specific antibodies were detected in only two fetuses from dams inoculated at 90 dp that were slaughtered at 42 dpi. No macroscopic changes in the placentas and organs of viable fetuses were observed. Nonsuppurative placentitis was a common microscopic observation in Neospora-inoculated specimens. Microscopic fetal lesions included nonsuppurative peribronchiolar interstitial pneumonia, epicarditis and myocarditis, interstitial nephritis, myositis and periportal hepatitis. Positive IHC results were obtained in two fetuses from dams inoculated at 70 dp and slaughtered at 28 dpi. N. caninum DNA was detected in placentas and fetuses from all inoculated animals. The pattern of amplified microsatellites from placental and fetal tissues resembled the NC-1 strain. Water buffaloes, like cattle, are susceptible to experimental inoculation with N. caninum at early pregnancy.

Shedding of Neospora caninum oocysts by dogs fed different tissues from naturally infected cattle

Neospora caninum is one of the most important causes of abortion in dairy cattle worldwide. The distribution of N. caninum in tissues of adult cattle is unknown and the parasite has not been demonstrated histologically in tissues of cows. In the present study the distribution of N. caninum in different tissues of adult cattle was evaluated by bioassays in dogs. Seventeen dogs (2–3 month-old) were fed different tissues of 4 naturally exposed adult cattle (indirect fluorescent antibody test N. caninum titer ≥400): 5 were fed with masseter; 5 with heart, 3 with liver, 4 with brain, and 3 pups were used as non-infected control. Two dogs fed masseter, 2 fed heart, 1 fed liver, and 3 fed brain shed oocysts, and all dogs presented no seroconvertion to N. caninum during the observation period of 4 weeks. The oocysts were confirmed as N. caninum based on the detection of N. caninum-specific DNA by PCR and sequencing. The results indicate that dogs can be infected by N. caninum with different tissues of infected cattle.

Experimental infection of dogs (Canis familiaris) with sporulated oocysts of Neospora caninum

Neospora caninum is widely distributed in the world and this parasite is one of the major causes of abortion in cattle. Dogs and coyotes are definitive hosts of N. caninum and several species of domestic and wild animals are intermediate hosts. Dogs can become infected by the ingestion of tissues containing cysts and then excrete oocysts. It is not yet known whether sporulated oocysts are able to induce a patent infection in dogs, i.e. a shedding of N. caninum oocysts in feces. The objective of this study was to experimentally examine the infection of dogs by sporulated oocysts. The oocysts used in the experiment were obtained by feeding dogs with brain of buffaloes (Bubalus bubalis) positive for anti-N. caninum antibodies by indirect fluorescent antibody test (IFAT ≥200). Oocysts shed by these dogs were confirmed to be N. caninum by molecular methods and by bioassay in gerbils, and sporulated N. caninum oocysts were used for the oral infection of four dogs. The dogs were 8 weeks old and negative for antibodies to N. caninum and Toxoplasma gondii. Dogs 1 and 4 received an inoculum of 10,000 sporulated oocysts each; dog 2 an inoculum of 5000 sporulated oocysts and dog 3 received 1000 sporulated oocysts of N. caninum. The total feces excreted by these dogs were collected and examined daily for a period of 30 days. No oocysts were found in their feces. The dogs were monitored monthly for a 6-month period to observe a possible seroconversion and when this occurred the animals were eliminated from the experiment. Dogs 1 and 4 seroconverted 1 month after the infection with titer, in the IFAT, of 1600 and 800, respectively; the other two dogs presented no seroconvertion during the 6-month period. Dogs 1 and 2 were euthanized 180 days after infection and were examined for the detection of N. caninum in tissues (brain, muscle, lymph node, liver, lung, heart and bone marrow) by immunohistochemistry and PCR with negative results in both techniques. Bioassay in gerbils with brain of these dogs was also performed and again the results were negative. In conclusion, dogs infected with sporulated oocysts of N. caninum were not able to shed oocysts in feces. However, a higher dose of infection stimulated the production of antibodies against N. caninum in the dogs.

Anticorpos IgG anti-Neospora caninum e Toxoplasma gondii em búfalas (Bubalus bubalis) criadas no estado do Pará

Para determinar a ocorrência de anticorpos IgG anti-Neospora caninum e Toxoplasma gondii em 14 unidades produtivas de búfalos, situadas em 13 municípios no estado do Pará, foram coletadas amostras de soro sanguíneo de 374 fêmeas adultas. Os soros foram submetidos à reação de imunofluorescência indireta (RIFI), utilizando-se os títulos 200 e 64, respectivamente como ponto de corte para N. caninum e T. gondii. Obteve-se 153 (40,9%) de animais soropositivos para N. caninum com 100% das propriedades com focos da infecção, enquanto que quatro búfalas (1,1%) foram soropositivas em quatro fazendas para T. gondii e uma búfala (0,27%) foi soropositiva para ambos parasitos. A presença de anticorpos é um indicativo da circulação desses protozoários em búfalos das propriedades estudadas, representando uma fonte de infecção para outros animais, assim como o possível envolvimento em distúrbios reprodutivos nessa espécie.

OCORRÊNCIA DE ANTICORPOS ANTI-NEOSPORA CANINUM EM FÊMEAS BUBALINAS DA REGIÃO OESTE DO ESTADO DE SÃO PAULO

RESUMO Foram testadas 404 amostras de soro de fêmeas bubalinas (Bubalus bubalis) para se verificar a ocorrência de anticorpos anti-Neospora caninum em rebanhos oriundos de cinco municípios da região oeste do Estado de São Paulo. Empregou-se a técnica da Reação de Imunofluorescência Indireta (RIFI), na diluição inicial de 1:100. Foram observados anticorpos antiNeospora caninum em 38,1% (154/404) dos soros testados, com títulos de anticorpos variando de 100 a 12.800. A frequência de animais sororeagentes observada entre os municípios variaram de 16,2 a 61,4% (P < 0,05). A faixa etária dos animais soropositivos apresentou diferença significativa no Município de Lucélia, onde as vacas com idade superior a 5 anos apresentaram maior frequência de infecção (P < 0,05). Esses resultados alertam para a presença da infecção em bubalinos da região Oeste do Estado de São Paulo.

Investigation of Neospora caninum, Hammondia sp., and Toxoplasma gondii in tissues from slaughtered beef cattle in Bahia, Brazil

Neospora caninum, Hammondia sp., and Toxoplasma gondii are parasites with morphological and genetic similarities. N. caninum and T. gondii are important abortive agents of cattle and sheep, respectively, and may infect numerous animal species. Hammondia sp. is not known to induce disease in animals, but may cause confusion in the identification of closely related coccidia. The aim of this study was to investigate infection rates caused by N. caninum, Hammondia sp., and T. gondii in beef cattle using a nested PCR for Toxoplasmatinae rDNA, followed by sequencing of the PCR products. Antibodies to N. caninum and T. gondii were also investigated in the tested animals. Brains and hearts were obtained from 100 beef cattle in a slaughterhouse in Bahia. Seven samples from brain tested positive for Toxoplasmatinae DNA. No positive reactions were found in heart tissues. After sequencing of the PCR products from all positive tissues, five sequences matched with N. caninum and two matched with T. gondii. Antibodies to N. caninum and T. gondii were found in 20% and 26% of the animals, respectively. The confirmation of N. caninum and the absence of Hammondia heydorni in the tested animals is suggestive that cattle are not efficient intermediate hosts of H. heydorni; however further studies need to be performed using a greater variety of tissues and a higher sample size. The detection of T. gondii DNA in bovine tissues reinforces the potential risk of transmission of this parasite to humans and other animals through the consumption of bovine meat.

Loss of infectivity of Neospora caninum oocysts maintained for a prolonged time

The purpose of this study was to investigate whether sporulated Neospora caninum oocysts, which had been stored for 46 mo in a 2% sulfuric acid solution at 4 degrees C, remain morphologically viable and infective to gerbils (Meriones unguiculatus). Six gerbils were orally inoculated with doses of 400 or 1,200 oocysts. Two mo after inoculation, the animals did not show any clinical signs, had no histological lesions, and were seronegative for N. caninum at 1: 50 in an immunofluorescent antibody test. PCR using the brain from each gerbil did not reveal N. caninum specific DNA. We conclude that oocysts preserved for 46 mo are not infective, despite being morphologically intact.

Prevalence of anti-Neospora caninum antibodies in cattle from the state of Mato Grosso do Sul, Brazil

Neospora caninum is an obligate intracellular parasite that can infect domestic and wild canids, as well as ruminants and equines. It was described in 1988 and has been known as a major cause of abortion in bovines and neuromuscular alterations and death in dogs. To estimate the prevalence of bovine neosporosis in the 22 municipalities of the so-called Estrato 1 subregion of the Brazilian state of Mato Grosso do Sul, blood samples were collected from cows aged 24 months and older, from December 2003 to March 2004. During sample collection, a questionnaire was used to gather data of epidemiological interest. The samples were subjected to serological diagnosis (indirect fluorescence antibody test - IFAT). Prevalences of 14.9% (449/2488) and 69.8% (143/205) were found for the animals and herds sampled, respectively. The variable found to be associated with seropositivity to N. caninum was abortion (OR 2.52; CI 1.25-5.06). The results revealed the presence of infection by N. caninum in the herds investigated, drawing attention to its role as a potential cause of abortion in cattle in Mato Grosso do Sul.

Molecular characterisation of BSR4, a novel bradyzoite-specific gene from Neospora caninum

Here we present the identification and cloning of the NcBSR4 gene, the putative Neospora caninum orthologue to the Toxoplasma gondii TgBSR4 gene. To isolate NcBSR4, genome walking PCR was performed on N. caninum genomic DNA using the expressed sequence tag NcEST3c28h02.y1 sequence, which shares a 44% identity with the TgBSR4 gene, as a framework. Nucleotide sequencing of amplified DNA fragments revealed a single uninterrupted 1227 bp open reading frame that encodes a protein of 408 amino acids with 66% similarity to the TgBSR4 antigen. A putative 39-residue signal peptide was found at the NH2-terminus, followed by a hydrophilic region. At the COOH-terminus, a potential site for a glycosylphosphatidylinositol anchor was identified at amino acid 379. A polyclonal serum against recombinant NcBSR4 protein was raised in rabbits, and immunolabelling demonstrated stage-specific expression of the NcBSR4 antigen in N. caninum bradyzoites produced in vitro and in vivo. Furthermore, RT-PCR analysis showed a slight increase of NcBSR4 transcripts in bradyzoites generated during in vitro tachyzoite-to-bradyzoite stage-conversion, suggesting that this gene is specifically expressed at the bradyzoite stage and that its transcription relies on the switch to this stage.

Detection of Toxoplasma gondii in water by an immunomagnetic separation method targeting the sporocysts

An immunomagnetic separation (IMS) method was developed to detect Toxoplasma gondii in fresh waters by using the monoclonal antibody 4B6 targeting the sporocyst wall of T. gondii, Hammondia hammondi, Hammondia heydorni, and Neospora caninum. Water concentrates obtained by filtering 10- to 20-l samples samples were spiked with Toxoplasma oocysts, sonicated to release the sporocysts, and analyzed by IMS-4B6. Mean sporocyst recoveries were 74.5 +/- 5.3% in drinking water, 30.6 +/- 2.4 and 37.1 +/- 3.2% in surface waters, and 81.6 +/- 2.1% in IMS buffer. Then, this IMS method was integrated in a multistep procedure (i.e., filtration, IMS, immunofluorescence and autofluorescence) to detect Toxoplasma in unspiked and spiked water samples (10-30 l) of various qualities. Sporocyst recoveries ranged from 14.4 to 44.7% in drinking water samples spiked with 1-10 oocysts/l, and from 17.8 to 32.5% in surface water samples spiked with 10 oocysts/l. Sporocysts were not detected in 25 unspiked water samples. A sporocyst-like structure was seen in one of these unspiked samples, but its coccidian nature could not be proved by three polymerase chain reaction (PCR) methods targeting sequences of coccidian small and large subunit rRNA genes and Toxoplasma repetitive elements. In conclusion, IMS-4B6 is relevant for the detection of Toxoplasma in water generating small concentrates (<1 ml). Due to 4B6 cross-reactions, a PCR would be useful to further characterize coccidian sporocysts found microscopically.

Molecular phylogenetic analysis inHammondia-like organisms based on partial Hsp70 coding sequences

The 70 kDa heat-shock protein (Hsp70) sequences are considered one of the most conserved proteins in all domains of life from Archaea to eukaryotes.Hammondia heydorni,H. hammondi,Toxoplasma gondii,Neospora hughesiandN. caninum(Hammondia-like organisms) are closely related tissue cyst-forming coccidians that belong to the subfamily Toxoplasmatinae. The phylogenetic reconstruction using cytoplasmic Hsp70 coding genes ofHammondia-like organisms revealed the genetic sequences ofT. gondii,Neosporaspp. andH. heydornito possess similar levels of evolutionary distance. In addition, at least 2 distinct genetic groups could be recognized among theH. heydorniisolates. Such results are in agreement with those obtained with internal transcribed spacer-1 rDNA (ITS-1) sequences. In order to compare the nucleotide diversity among different taxonomic levels within Apicomplexa, Hsp70 coding sequences of the following apicomplexan organisms were included in this study:Cryptosporidium,Theileria,Babesia,PlasmodiumandCyclospora. Such analysis revealed theHammondia-like organism to be the lowest divergent group when compared to other groups within the phylum Apicomplexa. In conclusion, the Hsp70 coding sequences proved to be a valuable genetic marker for phylogenetic reconstruction and may constitute a good candidate to be used with other genes for species phylogeny within this group of organisms.

Isolation and molecular detection of Neospora caninum from naturally infected sheep from Brazil

Neospora caninum was isolated from a naturally infected sheep from Brazil by bioassay in dogs. Approximately 70g of brain from each of two 4-month-old sheep with indirect fluorescent antibodies (>or=1:50) to N. caninum was offered to a different IFAT negative dog (Sheep n. 302, IFAT 1:400-Dog 1 and Sheep n. 342, IFAT 1:50-Dog 2). Parasite DNA was detected in both sheep brains using a PCR targeting the Nc-5 gene of N. caninum. Shedding of Neospora-like oocysts was noticed only in Dog 1, from 10 days post-inoculation (PI) to 25 days PI (a total of approximately 27,600 oocysts). Seventy days after infection, Dog 1 was euthanized and brain/cerebellum and medulla were collected and submitted to molecular methods, as were the oocysts, to confirm the identity of the isolate. Serum samples collected weekly from both dogs from the infection to the end of the experimental period had no antibodies anti-N. caninum by IFAT (<1:50). Oocysts, brain/cerebellum and medulla specimens of Dog 1 proved positive by a PCR assay targeting the Nc-5 gene of N. caninum. In addition, the oocysts have the DNA amplified by a PCR based on primers directed to the common toxoplasmatiid ITS1 sequence. The PCR products of ITS1 were sequenced, confirming again the isolate as N. caninum. Oocysts were also orally inoculated in two Swiss white mice two Mongolian gerbils (Meriones ungulatus) and two large vesper mice (Calomys callosus) (10(3)oocysts/animal). The rodents were sacrificed 2 months PI, and fresh preparations of brains showed Neospora thick-walled cysts in gerbil brains, but molecular detection using the Nc-5 PCR assay revealed DNA parasite in gerbil and also C. callosus brains. This is the first report of isolation and sequencing of N. caninum from a Brazilian sheep and the first report of molecular detection of N. caninum from C. callosus.

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.

Seroepidemiology of Neospora caninum and Toxoplasma gondii in cattle and water buffaloes (Bubalus bubalis) in the People's Republic of China

A seroepidemiological survey of Neospora caninum and Toxoplasma gondii in cattle and water buffaloes was carried out in the People's Republic of China. Serum samples were obtained from dairy (n=262, 9 herds in 9 provinces) and beef cattle (n=10, 1 herd) and water buffaloes (n=40) in China. All sera were tested for antibodies to N. caninum and T. gondii by an enzyme-linked immunosorbent assay (ELISA) and an indirect agglutination test (IAT), respectively. The overall seroprevalence of N. caninum in dairy cattle was 17.2% (45/262), and the herds seroprevalence of N. caninum was 88.9% (8/9), and antibodies to T. gondii were present in 6 cows (2.3%). None of the cows had antibodies against both T. gondii and N. caninum. Antibodies to T. gondii or N. caninum were not found in beef cattle or water buffaloes. The seroprevalence of N. caninum in aborting cows (20.2%) was higher than that in non-aborting cows (16.6%) with an odds ratio of 1.26 (95% CI, 0.54-2.95), but the difference was not statistically significant (P>0.05). There was no apparent association of N. caninum seropositivity with age or number of pregnancies. This is the first report on the seroprevalence of N. caninum in cattle and water buffaloes in China.

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.

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.

Occurrence of anti-Neospora caninum antibodies in water buffaloes (Bubalus bubalis) from the Northern region of Brazil

Anti-Neospora caninum antibodies were determined in sera of 196 water buffaloes (Bubalus bubalis) from three farms of the northern region of Brazil, using an indirect fluorescent antibody test. Antibody titers were found in 139 (70.9%) buffaloes with dilution values ranging from > or =25 to <200 in 41 animals, > or =200 to <800 in 35 animals, and > or =800 in 63 animals. The number of animals presenting titers > or =800 was statistically higher (p<0.05). All farms presented positive animals, however, the occurrence was higher (p<0.05) in farm 1 (87.2%) when compared with farm 2 (65.7%) and farm 3 (65.8%). The occurrence by age groups presented no differences (p>0.05). Results indicate a high exposure of water buffaloes to N. caninum in the Northern region of Brazil.