Seroepidemiological evidence for a relationship between Neospora caninum infections in dogs and cattle

Serosurvey and associated risk factors for Neospora caninum infection in Egyptian water buffaloes (Bubalus bubalis)

Neosporosis is a parasitic disease that causes reproductive disorders in animals, making it a barrier to maximum efficiency. The purpose of this study was to determine the seroprevalence of Neospora caninum (N. caninum) antibodies in water buffaloes from four governorates in northern Egypt. A commercial indirect-ELISA test was used to detect antibodies against N. caninum in the serum of 450 water buffaloes. The total seroprevalence of N. caninum in water buffaloes from Egypt was 31.3%, and the highest prevalence was observed in Gharbia governorate. The identified risk factors for N. caninum infections in water buffaloes were sex (OR = 1.96, 95%CI: 1.22-4.17), buffaloes more than 4 years of age ( OR = 5.80, 95%CI: 2.26-14.86), abortion in second trimester (OR = 16.48, 95%%CI: 2.99-34.03), history of abortion (OR = 3.45, 95%CI: 1.58-7.52) and contact with dogs (OR = 2.55, 95%CI: 1.51-4.32). Thus, more studies are needed to determine the role of buffaloes in the epidemiology of neosporosis in Egypt.

Causes of fetal death in the Flemish cattle herd in Brazil

Background and Aim

Flemish cattle in Brazil are on the brink of extinction and are found only in one herd in Lages, Santa Catarina State. This study aimed to uncover the reasons for the recurring abortions in the Flemish cattle herd.

Materials and Methods

Seventeen Flemish fetuses underwent postmortem examinations, with samples collected for histopathology and microbiology culture tests, polymerase chain reaction (PCR) test for Neospora caninum, and reverse transcription-PCR (RT-PCR) test for bovine viral diarrhea virus (BVDV) from 2015 to 2020.

Results

Of the 17 fetuses, N. caninum was the most common diagnosis and was found in 88% (15/17). One fetus (5.8%) had a coinfection with N. caninum and Citrobacter amalonaticus, leading to fibrinonecrotic pericarditis. All fetuses tested negative for BVDV by RT-PCR. Of the 107 dams tested by indirect immunofluorescence assay, 26 (25.2%) were anti-N. caninum seropositive, with 17 (65.4%) aborting and 5 (19.2%) having estrus repetition. Reverse transcription-PCR results showed that 9 (8.4%) of the serum samples collected from dams tested positive, which tested follow-up test 3 months later, indicating a BVDV transient infection. The factors that contributed to neosporosis included dogs' access to pastures and improper disposal of fetal remains, which made it easier for dogs to consume them.

Conclusion

This study warns the occurrence of N. caninum as a cause of reproductive disorders that can lead to abortion in the studied Flemish cattle herd.

Detection of Anti-Neospora caninum Antibodies on Dairy Cattle Farms in Southern Italy

Neosporosis is recognized as one of the major causes of bovine abortion worldwide. Canids are the main definitive host for this parasite and the presence of dogs in the farm is an important factor for the Neospora caninum infection in bovines. Since, in the province of Lecce, located in the Apulia region of Southern Italy, there are no studies showing the presence of the infection in farm animals, the objective was to perform a serological evaluation for anti-N. caninum antibodiesin serum from 706 dairy cattle and 21 farm dogs located in 40 farms uniformlydistributed over the territory.The presence of N. caninum infection was confirmed in 90.0% (36/40) of the 40 farms examined. The results obtained on all serum samples by an enzyme-linked immunosorbent assay (ID Screen^®Neospora caninum competition ELISA kit) for anti-N. caninum antibodies showed a seropositivity rate of 21.1% (149/706) among dairy cows, with a statistically significant higher percentage of positive subjects in the animals over two years old and a positivity rate of 42.9% (9/21) in tested dogs. The obtained data confirmed the presence of neosporosis even in the Lecce area, where it could therefore represent an important cause of abortion and economic losses.

Serological and molecular detection of Neospora caninum and Toxoplasma gondii in human umbilical cord blood and placental tissue samples

Neosporosis primarily affects cattle and dogs and is not currently considered a zoonotic disease. Toxoplasmosis is a zoonosis with a worldwide distribution that is asymptomatic in most cases, but when acquired during pregnancy, it can have serious consequences. The seropositivity rates determined by the indirect fluorescent antibody test for Neospora caninum (N. caninum) and Toxoplasma gondii (T. gondii) were 24.3% (49 samples) and 26.8% (54 samples), respectively. PCR positivity for N. caninum was observed in two samples of cord blood (1%) using the Nc5 and ITS1 gene, positivity for T. gondii was observed in 16 samples using the primer for the B1 gene (5.5% positivity in cord blood and 2.5% positivity in placental tissue). None of the samples showed structures characteristic of tissue cysts or inflammatory infiltrate on histopathology. Significant associations were observed only between N. caninum seropositivity and the presence of domestic animals (p = 0.039) and presence of dogs (p = 0.038) and between T. gondii seropositivity and basic sanitation (p = 0.04). This study obtained important findings regarding the seroprevalence and molecular detection of N. caninum and T. gondii in pregnant women; however, more studies are necessary to establish a correlation between risk factors and infection.

Seroprevalence of Neospora caninum Infection in Dog Population Worldwide: A Systematic Review and Meta-analysis

PURPOSE

Neospora caninum is an obligate intracellular apicomplexan protozoan that causes neurological disorders in dogs. This systematic review and meta-analysis targeted at evaluating the worldwide seroprevalence rate of N. caninum in dogs.

METHODS

Five electronic databases, including PubMed, Scopus, Web of Science, Science Direct, and Google Scholar, until December 2018 were thoroughly searched for relevant English language articles. Papers were selected based on inclusion criteria. Data were analyzed in StatsDirect statistical software (version 2.7.9).

RESULTS

The searching process yielded a total number of 156 papers. The total prevalence (95% confidence intervals) of N. caninum infection in dog population worldwide was measured as 17.14% in data analyses (15.25-19.10). In addition, a significant association was also detected between neosporosis infection in dogs and continent, country, year, WHO regions, sample size and diagnostic method (P < 0.001).

CONCLUSION

Dogs are a matter of concern to public health officials as a source of N. caninum infection. Therefore, it is of paramount importance to provide comprehensive data and systematically analyze the prevalence of N. caninum infection in dogs. Accordingly, it is recommended that researchers carry out further studies to prevent and control neosporosis among dog population worldwide.

Epidemiological relevance of dogs for the prevention of Toxoplasma gondii, Neospora caninum and Leptospira spp

This study evaluated the seroprevalence of Toxoplasma gondii, Neospora caninum and Leptospira spp. in dogs from Foz do Iguaçu, Paraná, Brazil. Indirect immunofluorescent antibody test was used to detect antibodies anti-T.gondii and anti-N. caninum. Immunoenzymatic assay and microscopic serum agglutination were used for screening antibodies anti-T.gondii and anti-Leptospira spp., respectively. The results were: 67.02% of the samples reactive for T.gondii and 1.38% for N. caninum, both without statistically significant variables. For Leptospira spp. the results indicated seroprevalence of 23.11%. The analysis of the variables without distinction of serovar showed association for intrinsic characteristics as breed, age, nutritional status and dog category. The extrinsic variables as city region and access to the street presented association (p<0.05). The most prevalent serovars were: Canicola 59.47%; Bratislava 13.07% and Butembo 15.68%. Variables that make up the adjusted multiple analysis model using Leptospira spp. were: age, breed and nutritional status; serovar Canicola, sex, nutritional status and area (p<0.05); serovar Bratislava, lymphadenomegaly and presence of fleas (p<0.05). Given the results obtained, dogs can be used as sentinels for toxoplasmosis and leptospirosis in Foz do Iguaçu and other cities with similar outcomes. In addition, preventive measures should be taken by health authorities because they are zoonoses and humans are also at risk.

INFECÇÃO POR Toxoplasma gondii, Neospora caninum, Leishmania major E Trypanosoma cruzi EM CÃES DO ESTADO DO PARÁ

Resumo Realizou-se inquérito sorológico para Toxoplasma gondii, Neospora caninum, Leishmania spp. e Trypanosoma cruzi em cães dos municípios de Castanhal e Belém, no Estado do Pará, e estudou-se a associação entre os animais sororeagentes e fatores como sexo, idade, acesso a rua e procedência dos animais. Foram utilizados 269 cães de diferentes idades, sadios, provenientes de abrigos de animais, canil comercial, Centro de Controle de Zoonoses e domiciliados. Utilizou-se a reação de imunofluorescência indireta (RIFI), com lâminas sensibilizadas de acordo com os seus respectivos antígenos. Das 263 amostras, 100 foram reagentes, com 38,0% de positividade para Toxoplasma gondii, sendo os títulos prevalentes 16UI e 64UI, 15,97% de sororreagentes para anticorpos anti-N. caninum com maior soroprevalência para os títulos 25UI e 50UI. Na pesquisa de anticorpos anti-L. major, 3,42% foram sororreagentes com o título 40UI, sendo o mais prevalente. A pesquisa de anticorpos anti-T. cruzi revelou negatividade em todas as amostras. As variáveis procedência e faixa etária mostraram ser um fator de risco para os animais. Os animais de Belém apresentaram 2,6 vezes mais chances de infecção do que os animais de Castanhal. Os animais na faixa etária de três a sete anos apresentaram 2,27 vezes mais chances de serem sororreagentes do que os cães com até três anos de idade. Não houve associação estatística para as demais variáveis e protozoários pesquisados.

Neospora caninum in properties in the west region of Paraná, Brazil: prevalence and risk factors

Abstract Neospora caninum is a heteroxenous protozoa, whose definitive hosts are canids and intermediate hosts are herbivores, and is of great importance in cattle. The objectives of this study were to determine the prevalence of N. caninum in dairy cattle and dogs, to detect the presence of the protozoa at the molecular level in aborted fetuses, and to identify the risk factors associated with infection in properties in the western region of the state of Paraná. For this study, 600 bovine serum samples from 60 properties, 163 canine serum samples from 52 properties and 17 bovine fetuses from nine properties were collected. Data were collected using an epidemiological questionnaire to verify the risk factors. Serum samples were analyzed using the indirect fluorescent antibody test. Fetal tissues were analyzed using polymerase chain reaction and subsequent DNA sequencing. Of the bovine samples, 23.67% were positive for N. caninum. Among the canine samples, 11.66% were positive for N. caninum. Risk factors in cattle were history of abortion, low milk production, extensive breeding, and Jersey breed (p<0.05). Protozoan DNA was detected in 52.94% of the 17 fetuses and the sequencing presented high similarity with N. caninum.

Seroprevalence of Neospora caninum-specific antibodies in German breeding bitches

BACKGROUND

Neospora caninum is an intracellular obligate apicomplexan parasite responsible for multisystemic lesions in dogs. Being definitive hosts and reservoirs, dogs excrete environmentally resistant oocysts. Breeding bitches represent a susceptible dog group and infected bitches may spread this parasite through transplacental transmission.

RESULTS

A total of 218 serum samples of German breeding bitches were collected to determine the presence of N. caninum. Antibodies were detected in 16 (7.33%) bitches using a commercial indirect enzyme-linked immunosorbent assay (ELISA). Immunoblotting analysis confirmed all seropositive samples detected by ELISA, proving that the animals were infected with N. caninum. The owners were interviewed regarding breed, age, environment, type, vaccine status, feeding habits and the presence of reproductive disorders. Seropositive animals were between the ages of two to seven years; three of them were kept in kennels while the others were household dogs, one of which was additionally a hunting dog. Owners of four seropositive bitches reported one gestation, while multiple pregnancies had been recorded for the other twelve bitches. Fourteen bitches were regularly vaccinated and six were fed with fresh raw meat.

CONCLUSIONS

Although the results confirmed a low incidence of N. caninum seropositive German breeding bitches, further epidemiological and surveillance studies are required to complement our findings regarding the current situation of neosporosis in this specific canine population of Germany.

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.

Risk factors for Neospora caninum infection in dairy cattle and their possible cause-effect relation for disease

Neospora caninum causes reproductive problems in cattle such as abortion, premature birth, retention of fetal membranes, and metritis. Therefore, this study aimed to verify possible risk factors for N. caninum infection in dairy cattle and their cause-effect relation to neosporosis. Serum samples of 1518 dairy cows from the West of Santa Catarina State, Southern Brazil were analyzed by indirect immunofluorescence assay (IFA) for N. caninum, where 466 were found to be positives (30.69%-CI_95%; 28.3-33.0). In addition, an epidemiological survey was conducted in order to verify possible risk factors for neosporosis and their relation to the disease. The presence of dogs in the farm was strongly associated with IFA positive results for N. caninum, and lack of history for neosporosis in the farm increased the chances of positivity in 66%. It was found a significant cause-effect relation between the occurrence of reproductive problems and the presence of antibodies against N. caninum (p = 0.05). It is possible to conclude that N. caninum is widely distributed in dairy farms of the Western part of Santa Catarina state, Brazil, and that the occurrence of reproductive problems is directly related to the disease with the presence of dogs as a risk factor for N. caninum infection.

Immune response in bovine neosporosis: Protection or contribution to the pathogenesis of abortion

Neospora caninum is a protozoan parasite with a preference for cattle and dogs as hosts. When N. caninum infection occurs in cattle it induces abortion, bovine neosporosis being a main cause of abortion worldwide. In dairy cattle, the economic burden of neosporosis-associated abortion is so great that it might results in closure of a farm. However, not all infected cows abort and it is not yet understood why this occurs. At present there is no effective treatment or vaccine. This review provides insights on how immune response against the parasite determines protection or contribution to abortion. Aspects on markers of risk of abortion are also discussed. Humoral immune responses are not protective against N. caninum but seropositivity and antibody level can be good markers for a diagnosis of bovine neosporosis and its associated abortion risk. In addition, humoral mechanisms against N. caninum infection and abortion differ in pure-breed and cross-breed pregnant dairy and beef cattle. Concentrations of Pregnancy Associated glycoprotein -2 (PAG-2) can also be used to predict abortion. A partially protective immune response encompasses increased IFN-γ expression, which has to be counterbalanced by other cytokines such as IL-12 and IL-10, especially towards the end of pregnancy. Although IFN-γ is required to limit parasite proliferation a critical threshold of the IFN-γ response is also required to limit adverse effects on pregnancy. In clinical terms, it may be stated that IFN-γ production and cross-breed pregnancy can protect Neospora-infected dairy cows against abortion.

Antibodies to Neospora caninum in sheep from slaughterhouses in the state of São Paulo, Brazil

Neosporosis is an emergent disease responsible for considerable economic impact due to reproductive losses. Its zoonotic potential remains unknown. This study involved a survey of antibodies to Neospora caninum in slaughtered sheep and their association with epidemiological variables. Serum samples from 596 sheep from the states of São Paulo and Rio Grande do Sul, Brazil, were collected in two slaughterhouses located in São Paulo and evaluated by indirect fluorescence antibody test (IFAT), using cut-off titers of 25. Among these samples, 353/596 (59.23%; 95%CI 55.23-63.10) were positive and 263/353 (74.50%; 95%CI 69.71-78.77%) were from Rio Grande do Sul. Statistical associations were determined in the univariate analysis between the serological results and sex, breed and municipality of origin. Sheep that came from extensive breeding system showed higher chance (OR=2.09) of presenting antibodies to N. caninum in relation to those from semi-intensive system. Higher chance was also observed for the different studied breeds, except Bergamácia, in relation to Hampshire Down. The results revealed the presence of infection by N. caninum in sheep from slaughterhouses.

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.

Canine neosporosis: perspectives on pathogenesis and management

Canine neosporosis is a worldwide disease caused by the obligate intracellular parasite protozoan Neospora caninum, manifesting mainly neurological symptoms. N. caninum has a heteroxenous life cycle and affects a wide range of warm-blooded animals. The domestic and wild canids are the definitive host of the parasite. They shed oocysts after ingestion of tissue cysts from infected intermediate hosts (ovine, equine, bovine, canine, and many other species), containing bradyzoites, or oocyst-contaminated water and food. The presence of dogs in farms is considered a risk factor for production animals. A wide range of diagnostic methods are currently available, but the most used is serology, ie, indirect fluorescent antibody test specific to the antibody detection in blood serum samples. No vaccine is available, but control strategies should be focused on the vertical and horizontal transmission of the parasite, ie, avoid feeding dogs with raw or undercooked meat, and taking care with water for human and animal consumption. No medicines to control the transplacental transmission are available yet.

Neospora caninum seropositivity and reproductive risk factors in dogs

Despite the importance of Neospora caninum in veterinary medicine, knowledge of distribution of neosporosis in dog populations in some countries is still poor. The aims of the present study were to determine the occurrence of anti-N. caninum antibodies in one-hundred dogs living in cattle farms or dog breedings in central Italy and to evaluate the risk factors associated with seropositivity. The incidence of reproductive system disorders (e.g. infertility after first pregnancy) was also evaluated. Serum from breeding and farm dogs was tested to an indirect immunofluorescent antibody test (IFAT) to assess the occurrence of seropositivity. Management and individual data were collected and analysed both by linear and logistic multiple-regression models to find reliable predictors of seroprevalence and anti-N. caninum antibody level. The seropositivity for N. caninum was 32%. Dogs reared for breeding and presence of cattle on the farm were associated with seropositivity for N. caninum. Dogs living in the cattle farms showed a higher seropositivity for N. caninum (46%) compared with those living in dogs breeding (18%) (P < 0.05). The high presence of seropositive dogs in cattle farms of the study region demonstrates the potential risk of horizontal transmission of N. caninum between dogs and cattle, regardless the occurrence of reproductive system disorders or with infectious bovine tissues contact. Although the Neospora seropositivity in dog breedings may appear relatively low if compared with that found in dogs living with livestock, this infection, apparently underestimated, should be considered as a potential serious problem in canine medicine.

Relation between Neospora caninum and abortion in dairy cows: Risk factors and pathogenesis of disease

Neosporosis is a parasitic disease cause by Neospora caninum, a parasite of great importance in livestock. This study aimed to evaluate the presence of antibody against N. caninum in dairy cattle with history of abortion, as well as to identify associated risk factors for neosporosis. Animals suspected of neosporosis (n = 130) after clinical examination were randomly selected. Sera samples from 29 farms were submitted to indirect immunofluorescence technique (IFA) in order to detect antibodies against N. caninum, and animals were considered positive if ≥ IFA 1:200. An epidemiological questionnaire was used to verify probable risk factors for neosporosis and their cause-effect relation. Serological results showed that 43.8% of the animals were seropositives for N. caninum. The univariate statistical analysis found a significant relation between neoporosis and age. The number of pregnancies and the number of years that the farms had been producing milk were found as associated risk factors for the disease either by univariate or by multivariate analyses. The cause-effect model found a possible relation between reproductive problems and positive serology for neosporosis (P = 0.06). Therefore, it was concluded that approximately 44% of dairy cows with history of abortion were seropositives for N. caninum and that age and the number of years that the farms had been producing milk are risk factors for parasite infection in dairy cattle.

Use of ELISA based on NcSRS2 of Neospora caninumexpressed in Pichia pastoris for diagnosing neosporosis in sheep and dogs

Neosporosis is a disease caused by the protozoon Neospora caninum that leads to significant economic losses in many countries. In the present study, we report on use of the recombinant protein NcSRS2 of N. caninum expressed in Pichia pastoris in an indirect immunoenzymatic assay (ELISA) for diagnosing neosporosis infection in sheep and dogs. We observed that the ELISA test yielded specificity of 94.5% and sensitivity of 100% for sheep and specificity of 93.3% and sensitivity of 100% for dogs. We observed that the sensitivity was higher than shown by the indirect fluorescent antibody test, and this was confirmed by means of Western blot. The results from this study suggest that the recombinant protein expressed in P. pastoris is a suitable antigen for use in immunodiagnosis to detect N. caninum in two important species exposed to this parasitosis.

A review of neosporosis and pathologic findings of Neospora caninum infection in wildlife

Neospora caninum is an apicomplexan parasite that is the etiologic agent of neosporosis, a devastating infectious disease regarded as a major cause of reproductive loss in cattle and neuromuscular disease in dogs worldwide. This protozoan pathogen is maintained in the environment by a heteroxenous life cycle that involves a definitive canid host and a wide range of intermediate hosts. In recent years, a number of wildlife species have been investigated for their possible involvement in the N. caninum life cycle and many have been implicated as intermediate hosts. However, in many instances these studies have utilized serological and molecular techniques to detect infection in clinically normal animals, and investigation of possible associated morbidity, mortality, and pathology has been neglected. As such, the occurrence and importance of Neospora-associated disease in wildlife species are unknown. In order to improve our understanding of the significance of N. caninum infection in nondomestic species, the present review provides an up-to-date summary of clinical neosporosis and N. caninum-associated pathologic lesions in naturally and experimentally infected wildlife species. We provide a list of all free-ranging and captive wildlife species identified with N. caninum infection to date using currently available diagnostic tools. The advantages and disadvantages of diagnostic methods in wildlife are addressed in order to recommend optimal diagnosis of confirming N. caninum infection and neosporosis in nondomestic species. Although current data would suggest that N. caninum infection does not adversely impact wildlife populations, there is a need for greater international uniformity in the diagnosis of N. caninum infection and neosporosis in nondomestic species in order to assess the true consequences of parasite infection.

Toxoplasmosis seroprevalence in wild small rodents, potentially preys of ocelots in north-eastern Mexico

The aim of this study was to assess the prevalence of Toxoplasma gondii infection in rodents that coexist with ocelots in north-eastern Mexico. Eighty rodents of five genera were captured and their serum samples tested for specific IgG antibodies to T. gondii by in-house indirect ELISA using three different conjugates. Prevalences of 7% (3/44) and 33% (4/12) were found in Sigmodon hispidus and Liomys irroratus, respectively, and were significantly different. All Baiomys taylori and Oligoryzomys fulvescens were negative for the presence of anti-T. gondii IgG antibodies. The samples from Peromyscus spp. could not be analyzed because none of the three conjugates tested recognized their immunoglobulins. Infection was confirmed in one single specimen of L. irroratus by qPCR, which generated an estimate of 146 parasites per mg of muscle tissue. The results strongly support the notion of active T. gondii transmission between rodents and felines in this zone of Mexico and an important role of some rodent species in the sylvatic cycle of T. gondii.

Neospora caninum exposure in overlapping populations of coyotes (Canis latrans) and feral swine (Sus scrofa)

Limited information exists on Neospora caninum transmission dynamics in wildlife. This coccidian parasite, whose presence can lead to substantial economic losses in cattle operations, requires a canid definitive host for reproduction. We examined exposure in a definitive host, coyotes (Canis latrans), and in overlapping populations of feral swine (Sus scrofa) to determine if spatial proximity between a definitive and incidental host influences the likelihood of parasite exposure. Eighteen percent of coyotes (95% confidence interval [CI] = 14.2-21.8) and 15.8% of feral swine (95% CI = 12.5-19.2) had been exposed to N. caninum, and this is the first report of exposure in US feral swine populations. Analyses suggest that the parasite is present throughout the environment and that exposure is not temporally or spatially linked to antibody-positive coyotes. Antibody-positive feral swine were found in an area where the only definitive host is domestic dogs (Canis familiaris), indicating that wild canids are not required to maintain the parasite in the environment.

Neospora caninum prevalence in dogs raised under different living conditions

Neospora caninum is an important cause of abortion in dairy cattle worldwide. Dogs are important in the epidemiology of N. caninum because they act as definitive hosts shedding oocysts in the environment. Vertical transmission of the parasite is well recognized as an important aspect of the epidemiology of the parasite but the importance of horizontal transmission has been less studied. A N. caninum competitive ELISA was used to examine serum samples from 600 dogs that were raised under 4 different living conditions. Samples from 138 dogs living on 24 dairies with a prevalence (0-70%) of anti-N. caninum antibodies in the cattle, 294 pet dogs without neurological signs, 76 from pet dogs exhibiting neurological signs, and 92 stray dogs were examined. The overall seroprevalence of N. caninum was 23.5% (95% CI = ± 2.99) in the 600 dogs. Significant (P < 0.05) differences were observed between the 4 different populations of dogs. The number of N. caninum positive samples were: 51 (36.9%, 95% CI = ± 3.09) of 138 dogs from dairies, 31 (10.5%, 95% CI = ± 6.38) of 294 pet dogs without neurological signs, disorders, 22 (28.9%, 95% CI = ± 6.70) of 76 pet dogs with neurological signs, and 37 (40.2%, 95% CI = ± 2.83) of 92 stray dogs. Seropositivity to N. caninum in dogs from dairies was associated with a high prevalence of N. caninum antibodies in the cattle. At the 3 dairies where no dogs were present, the seroprevalence to N. caninum in the cattle was significantly lower (P < 0.05) than in the 21 dairies where dogs were present. Seroprevalence was significantly higher (P < 0.05) in male dogs (97 of 366; 26.5%, 95% CI = ± 3.40) than in female dogs (44 of 234; 18.8%, 95% CI = ± 5.65). Seroprevalence in dogs increased with age suggesting postnatal exposure to N. caninum infection however, this increase was not significant (P > 0.05). The prevalence of N. caninum antibodies was not significantly (P>0.05) different in dogs based on breed. These findings suggest a relationship between N. caninum infection of dogs from dairies and cattle on these dairies. However, further research is required to determine what is the most important way dogs acquire infection and how to prevent dogs from shedding oocysts.

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.

Prevalence of antibodies against Toxoplasma gondii and Neospora caninum in dogs

Toxoplasmosis and neosporosis are parasitic diseases of global importance. The present study had the objective to determine the influence of age, sex and breed in the prevalence of antibodies against both diseases in dogs from Brotas city, São Paulo State, Brazil. Blood samples of 342 dogs were collected, and the age, sex and breed of each animal were recorded. The serological diagnosis for toxoplasmosis and neosporosis were performed using the immunofluorescent antibody test (IFAT). The Fischer's test was used to calculate the association probability of the variables, with α = 5%. For toxoplasmosis the prevalence of antibodies was 26.9% (CI 95% 22.4-31.8%), and for neosporosis 4.97% (CI 95% 3.1-7.8%). The statistical analysis revealed a higher risk of infection for T. gondii in dogs with more than five years.

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.

Neospora caninum infection dynamics in dairy cattle

Neospora caninum is considered in many countries as one of the key abortion agents in cattle. This study aims to investigate the parasite behavior in dairy cattle in the municipality of Avaré, SP, Brazil, where abortions frequently occur. An ELISA was performed to compare two samplings on a total of 615 animals; tests were performed in the same herds with a gap of 3 years. An increase in the percentage of reactive animals was observed, ranging from 21.6% at the first sampling to 38.9% at the second sampling. Of the 176 animals tested at both samplings, 61.93% retained a non-reactive status, 15.9% retained a reactive status, 19.88% switched from non-reactive to reactive and 2.27% switched from reactive to non-reactive. Of the 100 animals with reproductive disturbances, 50% presented anti-Neospora antibodies, thereby indicating the presence of the protozoa. When comparing cows and their respective female offspring, a predominance of horizontal infection was observed. Moreover, considering the significant percentage of animals that switched from non-reactive to reactive and the abundant presence of dogs among the herds, the N. caninum transmission may be attributed to presence of carnivores.

Risk factors of Neospora caninum infection in dogs and cats in dairy farms in Western Thailand

The objectives of this study were to investigate the risk factors of Neospora caninum infection in dogs and cats found in dairy herds in western Thailand. A case-control study was conducted in dairy herds in three western provinces including Nakhon Pathom, Ratchaburi and Kanchanaburi. Blood samples of pets from 14 positive dairy herds and 26 herds from negative neighbouring farms which were randomly selected, in total blood samples from dogs and cats from 40 herds were collected and examined for antibodies against N. caninum infections using competitive ELISA and indirect fluorescent antibody test (IFAT). No seropositive cats were found. Of the 38 positive dogs, four (10.5%) were seropositive to N. caninum, which was higher than the proportion of seropositive in the negative herd population (one of 76, 1.3%). The higher proportion of seropositive farm dogs as compared with neighbouring dogs tended to be significant (P = 0.055).

Factors associated with infection by Neospora caninum in dogs in Brazil

From August 2006 to 2008, 411 dogs in northeastern Brazil were evaluated for seropositivity to Neospora caninum. The dogs were clinically examined, and their owners were interviewed about the conditions in which the animals were maintained in order to assess the factors associated with infection by this parasite. A serum sample was taken from each dog for serological examination in an indirect fluorescent antibody test for N. caninum. The Yates' Chi-square test or Fisher's exact test was used to select the variables for the multivariate logistic regression model. Seropositivity was detected in 9.26% of dogs. The seropositivity rates of dogs from different environments were 2.6% (4/156) in urban areas, 13.1% (28/214) in peri-urban areas, and 14.6% (6/41) in rural areas. Factors associated with seropositivity for N. caninum were the following: contact with other dogs, access to food outside the home and residing in the peri-urban or rural environments (p<0.05). Results of this study confirm that dogs in urban, rural and peri-urban areas of northeastern Brazil are exposed to N. caninum. Control measures to prevent infection of dogs in the studied region should be focused primarily on preventing access to potential sources of infection, which include environments with other dogs, bovines, and other small intermediate hosts, such as birds and rodents.

Occurrence of anti-Neospora caninum and anti-Toxoplasma gondii antibodies in dogs with visceral leishmaniasis

Uninfected dogs and those naturally infected with Leishmania chagasi exhibiting different clinical forms of disease were evaluated for the presence of anti-Neospora caninum and anti-Toxoplasma gondii antibodies. Blood samples were collected from 110 mongrel dogs. Sera were tested using the indirect fluorescent antibody test (IFAT), and the animals with visceral leishmaniasis (VL) (n=60) were classified clinically. Out of the 110 sera investigated, 5 (4.5%) were positive for N. caninum (IFAT>50) and 36 (32.7%) for T. gondii (IFAT>16). Anti-L. chagasi antibody titers in asymptomatic dogs (n=10) were found to be significantly lower (P<0.05) than those in oligosymptomatic ones (n=22), which were in turn significantly lower (P<0.05) than those in symptomatic ones (n=28). No association between Leishmania and N. caninum infections was observed. Among dogs infected with L. chagasi, a tendency (P=0.053) towards an association between the infection with T. gondii and the appearance of VL symptoms was observed, suggesting that the clinical manifestation of VL in dogs may enhance their susceptibility to T. gondii. The possible influence of the immunosuppressive status of canine leishmaniasis in the different clinical forms of the disease is discussed.

Tunicamycins, a class of nucleoside antibiotics similar to corynetoxins of the Rathayibacter toxicus, increase susceptibility of mice to Neospora caninum

Neosporosis is the leading cause of abortion in cattle. Neospora caninum-associated abortion may exhibit both endemic and epidemic patterns. It was reported that the epidemic outbreaks took place in the form of "abortion storms" and were not significantly correlated with seasonal changes or consumption of any particular feeds; and thus, the mechanisms by which the epidemic "abortion storms" are triggered remain unclear. Annual ryegrass toxicity (ARGT) is a severe or fatal neurological disorder of livestock of Australia and South Africa. This disorder is caused by the ingestion of several plant genera (Lolium, Polypogon, and Agrostis) colonized by a nematode (Anguina sp.) and a bacterium, Rathayibacter toxicus. Corynetoxins (CTs) produced by R. toxicus contaminate plants which are in turn ingested by sheep and cattle, causing severe or often fatal hepatocerebral disorders in affected animals. We hypothesize that N. caninum-associated fetal deaths and abortions in cattle may be potentiated by pre-exposure of sublethal levels of CT-contaminated plants prior to N. caninum infection or reactivation of a latent infection. The exposure of sublethal CTs may not cause clinical diseases, but may increase susceptibility to pathogens such as N. caninum. Indeed, CT poisoning surviving pregnant sheep can have up to 10% abortions. The present study investigated whether animals pre-exposed to tunicamycins (TMs), a functional substitute for CTs, had a lowered resistance to sublethal experimental infection by N. caninum tachyzoites in mice. The results showed that sublethal doses of TMs or N. caninum alone did not cause significant deaths. Sublethal doses of N. caninum induced high mortality in TM-treated mice in a dose dependent manner. When mice were treated with a low dose of TMs (5 μg/mouse), as few as 2.5 × 10(6) tachyzoites were needed to induce more than 30% of mortality which is equivalent to the mortality rate caused by 40 × 10(6) tachyzoites. Spleen cells of mice treated with TMs had reduced (p<0.05) Neospora antigen-induced interferon-gamma (IFN-g) production and Con A-stimulated proliferation. The results suggest that CT contaminated plants, when exposed to animals under natural conditions, may contribute to lowered host resistance and increased N. caninum-associated fetal morbidity and mortality in affected animals.

Risk factors associated with Neospora caninum seropositivity in randomly sampled Canadian dairy cows and herds

Our objective was to determine cow- and herd-level risk factors associated with seropositivity for Neospora caninum in a large number of randomly selected Canadian dairy herds, controlling for important confounding variables and co-infections with bovine leukemia virus (BLV), bovine viral diarrhea virus (BVDV) and Mycobacterium avium subspecies paratuberculosis (MAP). Serum samples were obtained from 30 randomly selected cows, where available, in 240 herds using monthly milk testing, within 6 of 10 provinces, and these samples were tested for antibodies against BLV, MAP and N. caninum using commercially available ELISA test kits. Five unvaccinated cattle >6 months old from each herd were tested for antibodies to BVDV using virus neutralization. Most herd-level predictors were obtained through personal interviews with questionnaires administrated to each farm manager. A mixed logistic-regression model was built using N. caninum serostatus at the cow-level as the outcome variable, with herd as a random effect and province as a fixed effect. A BLV seropositive cow was 1.50 times more likely to be seropositive for N. caninum than a BLV-seronegative cow, and this was the only cow-level variable to remain in the final model. Regarding herd-level variables, with "no on-farm dogs" as the baseline, "presence of dogs but not known to eat placentas and/or fetuses" increased the odds of seropositivity for N. caninum by a factor of 1.66. For "presence of dogs known to eat placentas and/or fetuses", the odds ratio (OR) was 2.75, demonstrating a dose-response relationship. "Using embryo transfer" (OR=0.69), "asking for a BVDV-negative test before introducing an animal" (OR=0.30), "using monensin in dry cows" (OR=0.71), and "heifers having nose-to-nose contact with calves" (OR=0.73) were all dichotomous variables negatively associated with seropositivity for N. caninum. "Number of milk cows on the farm" (OR=0.99), and "area (acres) used for forage production" (OR=0.99) were continuous variables negatively associated with N. caninum seropositivity.

First epidemiological study on exposure to Neospora caninum in different canine populations in the Algiers District (Algeria)

Neospora caninum is an important cause of abortion in cattle worldwide. Dogs act as final hosts shedding oocysts in the environment. They can also harbour the extraintestinal stage of the parasite and this may be associated with a fairly rare neuromuscular condition. The sera of 781 dogs from the Algiers District were screened by IFAT for the presence of anti-N. caninum antibodies. These dogs were distributed into four populations: local stray dogs, police dogs, dogs from breeding kennels and farm dogs. The overall seroprevalence was 21.90%. Significant differences were observed between the different populations, the highest prevalence being observed in farm (44.44%) and stray dogs (22.55%). Additionally, the highest titres were observed in farm dogs. Among studied epidemiological parameters, breed, dog origin, season and vaccination status were significantly associated with IFAT results. Additionally, a recently described real time PCR was used on the blood of 100 pound dogs and the results were compared with the serological data. A higher proportion of dogs was found to be positive by PCR when compared to the IFAT results. There was only a fairly low agreement between PCR and IFAT results which suggests that these techniques measured different aspects of the host-parasite relationship. This study indicates that the level of exposure of the canine population of Algiers area to N. caninum is very high. This would indicate a potentially high risk for N. caninum induced abortion in cattle in this region and in Algeria.

Neospora caninum--how close are we to development of an efficacious vaccine that prevents abortion in cattle?

Neospora caninum is a protozoan parasite that causes abortion in cattle around the world. Although the clinical signs of disease in both dogs and cattle have now been recognised for over 20years, treatment and control options are still limited, despite the availability of a commercial vaccine in some countries of the world. The case for an efficacious vaccine has not been convincingly waged by farmers, veterinarians and other members of the agricultural and rural communities. In recent times, however, economic modelling has been used to estimate the industry losses due to Neospora-associated abortion, providing, in turn, the business case for forms of control for this parasite, including the development of vaccines. In this review, we document progress in all areas of the vaccine development pipeline, including live, killed and recombinant forms and the animal models available for vaccine evaluation. In addition, we summarise the main outcomes on the economics of Neospora control and suggest that the current boom in the global dairy industry increases the specific need for a vaccine against N. caninum-associated abortion.

Neospora caninum seropositivity in cattle breeds in the South Fluminense Paraíba Valley, state of Rio de Janeiro

The infection by Neospora caninum of different cattle breeds in dairy properties in two municipalities of the South Fluminense Paraíba Valley, state of Rio de Janeiro, was evaluated. Considering a sampling universe of 2,491 cows, blood samples were collected from 563 dairy cows in 57 farms, which were randomically selected in proportion to the number of animals, using a random stratified sampling system. For each property the number of selected cows was proportional to the herd size. Abortion or other reproductive disorders were not considered as criteria for selecting the animals, and seropositivity was determined by indirect enzyme-linked immunosorbent assay (ELISA). A high association (p=0.006) between seropositivity and racial patterns was found. The analysis revealed that in comparison of pure black-and-white Holstein cows versus Zebu (p=0.0028), Holstein cows showed 2.65 times greater odds for seropositivity. In the same way, by comparing black-and-white Holstein versus Zebu + crossbreed Zebu/Holstein (p=0.01), it was noted that there is 2.23 times more chance for seropositivity in Holstein cattle. There were no significant differences concerning the comparison of Holstein cattle versus crossbreed Zebu/Holstein (p=0.08) or Zebu versus crossbreed Zebu/Holstein (p=0.11). This study supports the hypothesis that there is a close association between cattle breeds and the frequency of infection by N. caninum.

Frequency of antibodies against Neospora caninum in stray and domiciled dogs from urban, periurban and rural areas from Paraná State, Southern Brazil

Antibodies to Neospora caninum were analyzed by an indirect fluorescent antibody test (IFAT), in stray and domiciled dogs from urban, periurban and rural areas from Curitiba, Paraná State, Brazil. Of the total of 556 dogs, 18.17% (101) were positive for N. caninum (titer 50). Frequency of antibody was 12.71 in urban, 15.73 in periurban, and 25.38% in rural dogs. Rural dogs had a significantly higher frequency of antibodies than urban dogs (P< 0.05). There were no significant differences between the frequencies of antibodies in urban and periurban dogs (P>0.05), and between dogs from periurban and rural areas (P>0.05). Antibodies to N. caninum were detected in 34 of 233 domiciled dogs (14.59%) and in 17 of 126 stray dogs (13.49%). No statistical differences were observed considering life-style and geographic location of origin (P>0.05). Neospora caninum is widespread among dogs from urban, periurban and rural areas of the municipal district of Curitiba, Paraná, Brazil.