Neospora caninum in pastured cattle: determination of climatic, environmental, farm management and individual animal risk factors using remote sensing and geographical information systems

Impact of environmental factors on Neospora caninum and Toxoplasma gondii infection in breeding ewes from western Mexico

In Mexico, Neospora caninum and Toxoplasma gondii are major causes of reproductive problems in sheep. Understanding the environmental factors that influence the spread of these parasites is crucial for developing effective control strategies. The objective of this study was to identify the environmental factors associated with N. caninum and T. gondii infections in sheep in western Mexico. Blood samples were collected from 184 sheep and determine seroprevalence using the ELISA test. Based on the seroprevalence data and information about the climatic regions and geographic characteristics, logistic regression analysis was employed to identify the environmental factors associated with N. caninum and T. gondii infections. Antibodies for N. caninum were found in 27 of the 184 blood samples. The environmental risk factors associated with N. caninum were Köppen climate area Ca(w1) with an OR = 6.55 and rainfall (700-800 mm) with an OR = 3.23. For T. gondii, antibodies were detected in 113 of the 184 sheep sampled. The main risk factors were Köppen climate area Cb(w1) with an OR = 10.5 and rainfall (900-1000 mm) with an OR = 4.6. Identifying these factors is crucial for developing more effective control strategies to reduce the incidence of these infections and improve the reproductive health of sheep flocks in the region.

Epidemiology of Bovine Neosporosis in Relation to Socioeconomic, Demographic, and Transmissibility Factors in Dual-Purpose Production Systems in Colombia

INTRODUCTION

Bovine neosporosis represents a significant threat to reproduction and production in livestock systems worldwide. This disease is caused by the protozoan Neospora caninum, resulting in abortions of cows and neurological signs in newborn calves. This leads to significant economic losses, decreasing meat and milk production, especially in tropical regions. The infection has an endogenous and exogenous cycle of transmission involving dogs that shed the oocysts, with the highest transmission successes in humid areas. Similarly, there is a lack of knowledge about the epidemiological risk factors and management practices involved in the transmission success in tropical humid regions.

METHODS

In this sense, a cross-sectional epidemiological survey was conducted on 150 farms from 24 municipalities of the Huila area. A total of 360 cattle were sampled, and information about the production system was collected using a structured poll with 128 questions.

RESULTS

In these cattle, 53% (191/360) were positive for antibodies against Neospora caninum using ELISA. The logistic regression analysis using the information collected from the poll identified the presence of flooring type, water access, production systems, and feed management as risk factors. Among the protective factors were identified the geographical area, molasses supplementation, and biosecurity practices such as animal separation and access control.

DISCUSSION

This study identified for the first time the epidemiological risk factors associated mainly with the exogenous cycle of neosporosis. The present study contributes to the design of intervention strategies oriented to minimize the impact of parasitism in Colombian herds.

Epidemiological surveillance of Neospora caninum in sheep (Ovis aries) and European mouflon (Ovis aries musimon) in southern Spain

Neospora caninum is a protozoan with a facultative heteroxenous life cycle, with canids as the definitive hosts and other mammals, mainly ruminants, acting as intermediate hosts. This parasite is recognized as one of the major abortifacient pathogens in cattle. Although reproductive disorders have also been reported in other domestic and wild ruminants, epidemiological data on N. caninum in ruminant species other than cattle is still limited. Here, we evaluate the seroprevalence and risk factors associated with N. caninum exposure in sheep (Ovis aries) and European mouflon (Ovis aries musimon) in southern Spain. Serum samples from 390 sheep and 387 free-ranging mouflons were tested for antibodies against N. caninum using in-house time-resolved fluorescence immunoassay based on NcGRA7 as a recombinant antigen. The individual seroprevalence was 26.2 % (95 %CI: 22.0-30.7) in sheep and 5.7 % (95 %CI: 3.8-8.5) in mouflons. At least one seropositive animal was detected in all the 26 sheep farms (100 %) and in eight of the 18 (44.4 %) hunting estates sampled. The presence of dogs on the farm (≥3) and the sheep breed (purebred) were potential risk factors associated with exposure to N. caninum in sheep. Our results indicate a high circulation of N. caninum in sheep farms in southern Spain. Control measures should be implemented to limit the exposure to this protozoan in sheep flocks. Although we have confirmed for the first time the presence of anti- N. caninum antibodies in European mouflon in Spain, and, despite the relatively low seroprevalence found, the impact of this parasite on mouflon populations should be further studied.

Seroprevalence and associated risk factors for Neospora caninum infection in dairy cattle in South Africa

Bovine neosporosis is a widespread parasitic disease associated with significant economic losses. Its effects on the reproductive performance of cows have resulted in losses that run into the hundreds of millions of US dollars in dairy industries in various countries (Reichel et al., Int J Parasitol 43:133-142, 2013). Due to outdated and scant information on the occurrence of Neospora caninum infection in South Africa, the study aimed to determine the seroprevalence and risk factors associated with infection in dairy cattle in South Africa. A total of 1401 blood samples were randomly collected from cattle on 48 dairy farms in seven of the nine provinces in South Africa. A close-ended questionnaire was used in a cross-sectional study to obtain farm-level and animal-level data. Serological testing was done using a commercial IDvet Screen® Neospora caninum Indirect ELISA. An overall seroprevalence, adjusted for test sensitivity and specificity, of 2.3% (95% CI, 1.3-4.1) was detected and 48% (23/48) of sampled farms had at least one animal testing positive. The highest seroprevalence of N. caninum was in the KwaZulu-Natal province with 7.5% (95% CI, 3.8-14.3), and the lowest in Western Cape with 0.1% (95% CI, 0-1.2). The highest within-farm seroprevalence of 25% was detected on a farm in the North West Province. In a multivariable logistic regression model, the odds of N. caninum seropositivity were higher in Holstein-Friesian cattle when compared to other breeds. Good hygiene was identified as a protective factor. Cattle left out on pasture had increased odds of testing positive for N. caninum compared to those that were penned. The odds of testing seropositive for N. caninum was higher on farms that practised segregation of cattle into different age groups. The purchase of replacement animals was a significant risk factor, as open herds had increased odds of N. caninum seropositivity. Cattle on farms that did not have a specific calving location were more likely to be seropositive. This is the first such study in South Africa and shows that N. caninum is widely distributed in the country at a low seroprevalence, but it may be a cause of concern on certain farms.

Neospora caninum antibodies in bulk tank milk from dairy cattle herds in Italy in relation to reproductive and productive parameters and spatial analysis

Among the available diagnostic techniques, antibody detection in bulk tank milk (BTM) represents a useful tool to estimate and monitor Neospora caninum herd prevalence. To evaluate the prevalence of N. caninum and the effect of parasite infection on herd performances, BTM samples collected from 586 dairy herds located in one of the largest dairy production areas in Italy (Lombardy) were analyzed by an indirect ELISA to detect anti-N. caninum specific antibodies. Generalized linear models (GLMs) were developed. A purely spatial analysis scanning for clusters with high or low rates for N. caninum using the Bernoulli model was performed. A maximum entropy approach was used to estimate the probability of distribution of the parasite based on occurrence records together with environmental variables. Overall, 180 herds resulted positive for N. caninum antibodies on bulk tank milk (P = 30.7 %). A higher risk of seropositivity was evidenced in the provinces of Milano, Cremona, Brescia, and Bergamo (P = 32-40 %); a lower risk was evidenced in Lodi, Pavia, and Mantova (P = 13-24 %). A higher risk of seropositivity was revealed for small-medium farms (101-300 animals) (O.R.=2.8) and for older animals with more than 4 years (O.R.=4.4). Regarding the effect of N. caninum infection on herd performances, the number of inseminations for conception was higher (> 3 inseminations), and the period from calving to conception was longer (> 150 days) for positive farms (O.R.=2.0 and O.R.=2.3, respectively); besides, lower head daily milk production (<20 kg and 21-25 kg) and mature equivalent milk yield (<11,000), and somatic cell counts higher than 300,000 cells/ml were observed for N. caninum positive herds (O.R.=0.4, O.R.=0.4 and O.R.=1.9 respectively). The geographical distribution of N. caninum positive farms with the highest level of probability covers the central sector of the Po Plain where a significant cluster for high risk of parasite infection was shown by spatial scan statistic and Maximum entropy ecological niche modelling. A further significant cluster of low risk occurred in the southern. The climatic and environmental variables with the highest training gain when used in isolation resulted altitude, land use/land cover, and other variables related to temperature and precipitation. Neosporosis is widely distributed in Italian dairy herds and an impact of the parasite on herd performances could be hypothesized. Even if the role of N. caninum in alterations of reproductive and productive parameters should be further explored, veterinarians and farmers should be aware of neosporosis, and control plans should be adopted.

Herd and animal level prevalences and risk factors for Neospora caninum infection in cattle in the state of Paraíba, northeastern Brazil

Bovine neosporosis is a globally important disease, causing abortions and significant economic losses. In Brazil, studies on neosporosis in cattle are few and based on limited samples and/or from limited areas. We aimed to determine the herd and animal levels seroprevalence and associated factors for Neospora caninum infections in cattle from the state of Paraíba, Northeastern Brazil, using a planned sampling. Herds (n = 434) and cows aged ≥24 months (n = 1891) were randomly selected, and serum samples were tested with the immunofluorescence antibody test (IFAT) using as cut-off point the antibody titer 200. Herd-level and animal-level seroprevalences were 17.8% (95% CI = 14.3%-21.8%) and 18.1% (95% CI = 14.7%-22.1%), respectively. The factors associated with N. caninum infection were farm located in the Sertão mesoregion (Prevalence ratio [PR] = 2.37), mixed production (PR = 1.64), herd size of 34-111 animals (PR = 3.50) and herd size >111 animals (PR = 6.14). The results indicate high N. caninum circulation in the bovine population of the state of Paraíba, semiarid of Brazil, mainly in the Sertão mesoregion, where the highest apparent herd and animal-level prevalences of positive herds were identified. Control strategies should be adopted to mitigate the impact of disease on cattle production, as well as it's suggested the encouragement of conducting surveys in wildlife from Caatinga biome, mainly canids, to provide information on the importance of these animals on the epidemiology of bovine neosporosis.

Seroprevalence and risk factors of Toxoplasma gondii and Neospora caninum infection in black goats in Yunnan Province, Southwestern China

Toxoplasma gondii and Neospora caninum are two obligate intracellular protozoan parasites that can cause reproductive failure and production losses. To date, there is no data of T. gondii and N. caninum seroprevalence in black goats in Yunnan Province, southwestern China. In the present study, a total of 734 serum samples were collected from black goats in four different counties of Yunnan Province. 734 and 590 serum samples were examined for antibodies against T. gondii and N. caninum by using MAT and indirect ELISA, respectively. A total of 123 and 76 samples were T. gondii-positive and N. caninum-positive, respectively. The overall seroprevalence of T. gondii in black goats was 16.76% (123/734, 95% CI: 14.06-19.46) with the titer ranged from 1:25 to 1:3200. The seroprevalence of N. caninum was 12.88% (76/590, 95% CI: 10.18-15.58). There was significant difference in seroprevalence of N. caninum in different regions (P < 0.01, χ² = 30.63) and age groups (P < 0.05, χ² = 11.85). Significant differences in seroprevalence of T. gondii were observed in different regions (P < 0.05, χ² = 9.21) and different gender groups (P < 0.01, χ² = 12.29). Results of seroprevalence of T. gondii and N. caninum indicated that T. gondii and N. caninum were prevalent parasites in black goats in Yunnan Province. This is the first report of seroprevalence of T. gondii and N. caninum in black goats in Yunnan Province. The results of this study indicated that some measures should be taken to control these two parasites and to reduce economic losses to the livestock industry in Yunnan Province.

The Utility of Serological Analysis for Neospora caninum Infection in Dairy Cattle Farms Management: Serological Investigation and Evaluation of the Effects on Reproductive and Productive Performances in Two Study Herds in Northern Italy

Simple Summary

Among infectious agents triggering reproductive disorders in cattle, Neospora caninum, an obligate intracellular protozoan parasite, is a major cause of abortion in cows worldwide. A serosurvey was designed in two cattle herds, both located in northern Italy and with similar reproductive management features, recruited as a case study. The clinical outcome and the effects on herd performances were evaluated in association with the seropositivity to N. caninum. This study showed that the integration of serological analysis results for N. caninum, the reproductive and productive parameters, and the information on herd performances, could give indications for the application of control strategies.

Abstract

Neospora caninum is recognized as a major cause of abortion in cattle, determining economic losses, particularly in dairy industries. To evaluate the impact of neosporosis on herd efficiency, and to understand how the serological analysis for N. caninum is explicative of the farm picture, an epidemiological study was designed in two dairy farms recruited as a case study. Blood samples were collected from 540 animals, including cows and heifers over 12 months, and analyzed by an indirect immunofluorescent antibody test with subsequent antibody titration. Overall, 94 animals (17.4%) were identified as positive to N. caninum antibodies (15.5% and 18.5% in Farm 1 and Farm 2), with differences between the farms concerning the antibody titers (Chi-square, p-value = 0.04), particularly in cows (Chi-square, p-value = 0.018). Consequently, a different pattern of abortion episodes was depicted in the two investigated farms. Considering reproductive and productive performances, the number of inseminations necessary to make an animal pregnant was higher in seropositive cows (2.4 and 2.9 in Farm 1 and 2, respectively) than in seronegative ones (2.1 and 2.4 in Farm 1 and 2, respectively). Similarly, particularly in Farm 1, the number of days in milk of not-pregnant cows was higher in seropositive (167.7) than seronegative animals (133.4). Moreover, although the association between N. caninum infection and milk production is still unclear, both the daily milk production and the 305-mature equivalent milk yield were lower in seropositive (31.02 and 11,838.94) than seronegative cows (33.59 and 12,274.88) in Farm 1; an opposite pattern was otherwise depicted in Farm 2. The study showed that even if N. caninum circulated equally in the two herds, the dynamics of the parasite infection and its outcome may be different, also depending on the specific situation of the farm. In this way, the integration of serological analysis for N. caninum, the reproductive and productive parameters, and the information on herd performances, could give specific indications for the application of control strategies.

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

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

Seroprevalence of Neospora caninum and Toxoplasma gondii IgG and IgM antibodies among buffaloes and cattle from Menoufia Province, Egypt

The main reasons behind performing the current study were the high distribution of the water buffaloes Bubalus bubalis and cattle in Menoufia province, the veterinary importance of Neospora caninum and Toxoplasma gondii and the limited information on the seropositivity of these parasites in Menoufia province, Egypt. Therefore, the current study was conducted to estimate the distribution of anti-N. caninum and anti-T. gondii antibodies (IgM and IgG) in water buffaloes and cattle from Menoufia province. ELISA methods based on the surface antigen 1 of N. caninum (NcSAG1t) and the surface antigen 2 of T. gondii (TgSAG2t) were utilized to detect both specific IgM and IgG for these parasites. The overall seroprevalence of N. caninum and T. gondii in cattle of Menoufia Province were (12.21% and 1.91% for IgM) and (14.89% and 3.05% for IgG), respectively. In water buffaloes, seroprevalences of N. caninum and T. gondii were (6.97% and 9.02% for IgM) and (13.52% and 8.2% for IgG), respectively. The mixed infection rate was 1.5% in cattle and 4.92% in buffaloes. No significant differences were detected regarding age or gender. Statistically significant changes in the prevalence of both parasites were demonstrated in relation to a period of the year. In conclusion, seroprevalence of neosporosis was more than toxoplasmosis in cattle and buffaloes in Menoufia Province, Egypt.

Seroprevalences of Toxoplasma gondii and Neospora caninum infections in Jordanian women who had a recent spontaneous abortion

This cross-sectional study investigates Toxoplasma gondii and Neospora caninum among 445 recently spontaneously aborted (RSA) Jordanian women using ELISA and indirect fluorescent antibody (at a cut-off value of 1/200) tests, respectively. The type of hospital, age, cat and dog contacts, raw and barbecued meat and wild plant consumption, number of abortions, and stillbirths were tested as independent variables using univariate and multivariate logistic regression analyses. The true seroprevalences were 22.1% for T. gondii-IgG, 22.7% for N. caninum-IgG, 2.6% for T. gondii-IgM, 10.6% for N. caninum-IgM, 0% for T. gondii-IgG and IgM, 6.7% for N. caninum-IgG and IgM, and 4.6% and 0% for both parasite IgG and IgM, respectively. T. gondii-IgM-seropositivity was associated with the number of abortions with odds ratios (OR) of 2.4 and eating barbecued meat (OR = 0.12). N. caninum-IgG-seropositivity was associated with having a dog in the house (OR = 2.6), and with stillbirth (OR = 0.1). N. caninum-IgM was associated with visiting a private-hospital (OR = 2.7). RSA Jordanian women are equally exposed to both parasites with significantly (p < 0.05) higher seroprevalence of N. caninum-IgM compared to T. gondii-IgM suggestive of active infections among RSA women in Jordan.

Age, gender and climate associations with the seroprevalence of Neospora species infection in horses in Jordan

A cross-sectional study was carried out on a sample of 379 horses to determine the seroprevalence of Neospora spp. in Jordan using the indirect fluorescent antibody test. Five variables, namely locality (n=10), climatic zone (n=4), age group (n=3), gender, and breed were tested as risk factors for Neospora-immunoglobulin (Ig)G seropositivity at four cutoff titers (1:50, 1:200, 1:400, and 1:800) using univariate and multivariate logistic regression analyses. A total of 122 (32%; 95% CI: 28, 37) sera samples had anti-Neospora-IgG at a cutoff titer of 1:50. Increased Neospora-IgG seropositivity was found in horses in three localities (Madaba, Zarka, and Petra) and was associated with the following variables: cool temperate climate; age >14 years; and female gender. Seropositivity was found among horses from Madaba at all cutoff titers, Zarka at titers >1:200, and Petra at titers <1:200. Cool temperate climate was associated with titers <1:400. Horses aged >14 years were found to be associated with seropositivity at titers ≥1:200. Female gender was associated with high seropositivity at >1:800.

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.

Spatial Analysis of Infections by Toxoplasma gondii and Neospora caninum (Protozoa: Apicomplexa) in Small Ruminants in Northern Italy

The objectives of this study were: (i) To investigate possible geographical or environmental factors influencing the infections by Toxoplasma gondii and Neospora caninum in sheep and goats in northern Italy; (ii) to identify areas at risk of infection to set up preventive measures. Forty-three sheep and goat farms were included. Their locations were plotted and associated with T. gondii and N. caninum seroprevalence, then the distribution of farms' prevalence was evaluated by spatial analysis. Significant clusters for both low and high prevalence were obtained, and a generalized linear model with ordinal logistic regression was implemented to verify if spatial clustering could be due to climate factors (temperature, rainfall, and their interaction). Clusters of high (80.0%) and low prevalence (28.12%) resulted for T. gondii seroprevalence in sheep farms. No significant clusters resulted for goat farms. Clusters of high (38.68%) and low prevalence (21.23%) resulted for N. caninum seroprevalence in sheep farms. One high-prevalence cluster (15.62%) resulted for goat farms. For goats, spatial analysis and analysis on climatic data showed the absence of environmental significant risk factors associated with T. gondii or N. caninum infection. On the contrary, for sheep, annual temperature, rainfall, and their association affected the risk of T. gondii and N. caninum infection. Particularly, high temperatures and abundant rainfalls were related to T. gondii seroprevalence, while low temperatures and scarce rainfalls were related to N. caninum seroprevalence.

Meta-analysis of the prevalence and risk factors associated with bovine neosporosis

Neospora caninum is one of the main infectious agents that cause reproductive disorders in cattle. However, knowledge about the prevalence and causal factors of bovine neosporosis is needed in order to establish control measures. The purpose of this study was to estimate the pooled prevalence and determine the risk factors of bovine neosporosis using meta-analytic methods. Searches for data on N. caninum seroprevalence and potential risk factors were conducted in the PubMed, LILACS, and SciElo databases. The random effects model was used for the meta-analysis of the included studies. The pooled prevalence of N. caninum in cattle was 24% (95% confidence interval (CI), 19-29) in North and Central America, 24% (95% CI, 20-28) in South America, 18% (95% CI, 14-21) in Asia, 15% (95% CI, 12-18) in Europe, 13% (95% CI, 11-16) in Africa, and 8% (95% CI, 4-14) in Oceania. A significant correlation was found between N. caninum infection and abortion in cows (odds ratio (OR) = 2.66, 95% CI, 1.97-3.59). The following risk factors were signicantly associated with N. caninum seroprevalence: presence of dogs on the farm (OR = 2.84; 95% CI, 1.40-5.80) and the type of cattle production system, with dairy cattle being more susceptible to bovine neosporosis (OR = 1.60; 95% CI, 1.16-2.19) than beef cattle. The adoption of measures to prevent the dissemination of N. caninum in cattle herds is suggested, aiming to reduce the economic losses incurred to the dairy and beef industry.

Evaluation of abortions spontaneously induced by Neospora caninum and risk factors in dairy cattle from Lima, Peru

Our objective was to identify the direct and indirect presence of Neospora caninum in dairy cattle and their aborted fetuses from Lima, Peru. A total 219 blood samples obtained from dairy cattle with records of spontaneous abortion were collected to detect antibodies against N. caninum in serum with indirect ELISA and search for risk-factor associations. 68 fetal aborted tissue samples of these cows were analyzed by PCR, indirect ELISA and histopathology assay to detect N. caninum presence. The prevalence ratio (PR) and 95% confidence intervals (CI) were estimated. Univariate analysis was performed using the chi-squared test. Among the 68 aborted fetuses collected, 10 (15%) were positive in at least two diagnostic tests. Among 219 serum samples, 46.6% (95% CI: 40.0%-53.3%) were positive. Cows with 4 years or older (PR: 7.10; 95% CI: 4.89-10.67) and multiparous (PR: 1.76; 95% CI: 1.11-2.80) were found to be more likely to possess N. caninum antibodies. This study detects presence of N. caninum in dairy cattle and their aborted fetus from Lima valley, suggesting biosecurity management improve to neosporosis control.

Seroprevalence, spatial analysis and risk factors of infection with Neospora caninum in cattle in Brazil's northern Pantanal wetland

Neosporosis is caused by an obligate intracellular protozoan, Neospora caninum . It is considered one of the most widespread and frequent causes of abortion in cattle worldwide. To evaluate the prevalence of anti-N. caninum antibodies and associated risk factors, serum samples were collected from 2,452 bovines at 262 farms in the northern Pantanal, state of Mato Grosso, Brazil. Each farmer was asked to fill out a questionnaire for subsequent epidemiological data analysis. Anti-N. caninum antibodies were detected by means of the indirect immunofluorescent assay (IFA), using a cut-off dilution of 1:100. The overall anti-N. caninum antibodies prevalence was 25.44% (Confidence Interval - CI 95%; 20.10%; 30.78%), and the anti-N. caninum antibodies prevalence per herd was 76.72% (CI 95%; 71.60%; 81.84%). The presence of dogs, occurrence of abortion in cows, and sale of cattle for breeding were statistically associated with seropositivity in herds, while the risk of females being seropositive for N. caninum was higher in animals ≤ 6-years-old and in the presence of dogs. A spatial analysis indicated that the relative risk of the disease is spatially constant and that the farms with the highest prevalence of anti-N. caninum antibodies are located south of the region under study.

Host species heterogeneity in the epidemiology of Nesopora caninum

Pathogen transmission across species drives disease emergence; however, mechanisms by which multi-host pathogens cross species boundaries are not well identified. This knowledge gap prevents integrated and targeted control in an epidemiologically continuous ecosystem. Our goal is to describe the impact of host species heterogeneity on the epidemiology of Neospora caninum circulating between livestock and wildlife in southeastern Ohio. We collected biological samples from Père David’s deer (Elaphurus davidianus) located at an outdoor wildlife conservation center; from cattle raised at farms adjacent to the center; and from wild white-tailed deer that roamed across farm and center boundaries. We designed nested infectious disease models of competing hypotheses about transmission and used collected data to fit the models, thereby estimating important immunological and transmission quantities which describe the species-specific contribution to the persistence of this pathogen in the community. We applied these data and models to suggest appropriate species-specific disease control methods. Results show that immunity in cattle and Pére David’s deer wanes over time, while in white-tailed deer immunity appears to be lifelong. Transmission quantities for cattle were estimated at values below the threshold for an outbreak (R_t < 1), meaning that chains of transmission are not maintained within this population and infections must occur due to reintroduction from an outside source. Pére David’s deer and white-tailed deer both could maintain continuous chains of transmission within their group (R_t > 1). Therefore, we propose that control of contact with outside sources will be useful for disease control in cattle; boosting immunity with vaccines might be an avenue to prevent infection in cattle and Père David’s deer. White-tailed deer are a potential maintenance host for infection and require further study to determine optimal control methods. Community-level investigations like this allow us to better evaluate heterogeneities in transmission processes that ultimately guide targeted control.

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.

Vaccines against neosporosis: what can we learn from the past studies?

Neospora caninum is an intracellular apicomplexan parasite, which is a leading cause of abortion in cattle; thus neosporosis represents an important veterinary health problem and is of high economic significance. The parasite can infect cattle via trans-placental transmission from an infected cow to its fetus (vertical transmission), or through the oral route via ingestion of food or water contaminated with oocysts that were previously shed with the feces of a canid definitive host (horizontal transmission). Although vaccination was considered a rational strategy to prevent bovine neosporosis, the only commercialized vaccine (Neoguard®) produced ambiguous results with relatively low efficacy, and was recently removed from the market. Therefore, there is a need to develop an efficient vaccine capable of preventing both, the horizontal transmission through infected food or water to a naïve animal as well as the vertical transmission from infected but clinically asymptomatic dams to the fetus. Different vaccine strategies have been investigated, including the use of live attenuated vaccines, killed parasite lysates, total antigens or antigen fractions from killed parasites, and subunit vaccines. The vast majority of experimental studies were performed in mice, and to a certain extent in gerbils, but there is also a large number of investigations that were conducted in cattle and sheep. However, it is difficult to directly compare these studies due to the high variability of the parameters employed. In this review, we will summarize the recent advances made in vaccine development against N. caninum in cattle and in mice and highlight the most important factors, which are likely to influence the degree of protection mediated by vaccination.

Neospora caninum antibodies in dairy cows and domestic dogs from Vojvodina, Serbia

Neospora caninum, the causative agent of neosporosis, is a protozoan parasite responsible for high rate of abortion in cattle worldwide. In dogs, consequences of infection vary from severe neuromuscular disorders to asymptomatic infection and shedding of environmentally resistant oocysts. In this study, we determined the occurrence of N. caninum antibodies in dairy cattle and dogs in Vojvodina (Northern Province of Serbia) and possible risk factors. N. caninum antibodies were found in 15.4% (55/356, CI 95%:12.0–19.6) of cows and 17.2% (17/99, CI 95%: 10.8–26.2) of dogs. Cows from smallholdings showed significantly greater odds (OR = 5.28, CI 95%: 2.0–13.6, p = 0.0006) of being seropositive in comparison to the farm cows. Epidemiological importance of results is discussed.

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.

A review of the infection, genetics, and evolution of Neospora caninum: from the past to the present

This paper is a review of current knowledge on Neospora caninum in the context of other apicomplexan parasites and with an emphasis on: life cycle, disease, epidemiology, immunity, control and treatment, evolution, genomes, and biological databases and web resources. N. caninum is an obligate, intracellular, coccidian, protozoan parasite of the phylum Apicomplexa. Infection can cause the clinical disease neosporosis, which most notably is associated with abortion in cattle. These abortions are a major root cause of economic loss to both the dairy and beef industries worldwide. N. caninum has been detected in every country in which a study has been specifically conducted to detect this parasite in cattle. The major mode of transmission in cattle is transplacental (or vertical) transmission and several elements of the N. caninum life cycle are yet to be studied in detail. The outcome of an infection is inextricably linked to the precise timing of the infection coupled with the status of the immune system of the dam and foetus. There is no community consensus as to whether it is the dam's pro-inflammatory cytotoxic response to tachyzoites that kills the foetus or the tachyzoites themselves. From economic analysis the most cost-effective approach to control neosporosis is a vaccine. The perfect vaccine would protect against both infection and the clinical disease, and this implies a vaccine is needed that can induce a non-foetopathic cell mediated immunity response. Researchers are beginning to capitalise on the vast potential of -omics data (e.g. genomes, transcriptomes, and proteomes) to further our understanding of pathogens but especially to identify vaccine and drug targets. The recent publication of a genome for N. caninum offers vast opportunities in these areas.

Geographical distribution modelling for Neospora caninum and Coxiella burnetii infections in dairy cattle farms in northeastern Spain

Maximum entropy ecological niche modelling and spatial scan statistic were utilized to predict the geographical range and to investigate clusters of infections for Neospora caninum and Coxiella burnetii in dairy cattle farms in Catalonia, northeastern Spain, using the Maxent and SaTScan programs, respectively. The geographical distribution of Neospora and Coxiella with the highest level of probability (P > 0·60) covers central Catalonia and spreads towards northeastern Catalonia which contains a high concentration of dairy cattle farms. The most important environmental factor that contributed to the ecological niche modelling was precipitation of driest month followed by elevation. Significant clusters (P < 0·001) were detected for Neospora and Coxiella infections in the western and eastern regions of Catalonia, respectively.

Study of the risk factors associated with Neospora caninum seroprevalence in Algerian cattle populations

Bovine abortions due to Neospora caninum infection were reported worldwide. The situation in Algeria was unknown. For the evaluation of the prevalence of N. caninum and its associated risk factors, 799 cattle belonging to 87 farms of the north and northeast of Algeria were analyzed. The cattle were divided into imported cattle, local cattle and improved cattle corresponding to breeding between imported and local cattle. Sera were examined for the presence of N. caninum antibodies by indirect fluorescence antibody test. The overall seroprevalence for the 87 farms was 52.87% (41.28-62.71%). The overall animal seroprevalence was 19.64% (16.82-22.45%). The seroprevalence of N. caninum in local cattle (34.28%) was significantly higher (p<0.05) than in modern (16.04%) and improved (18.64%) cattle. The risk factors analysis indicated that cattle population, geographical location, dog presence, season, global farm hygiene or the presence of abortion were significantly associated with seroprevalence.

Covariate selection in multivariate spatial analysis of ovine parasitic infection

Gastrointestinal (GI) strongyle and fluke infections remain one of the main constraints on health and productivity in sheep dairy production. A cross-sectional survey was conducted in 2004-2005 on ovine farms in the Campania region of southern Italy in order to evaluate the prevalence of Haemonchus contortus, Fasciola hepatica, Dicrocoelium dendriticum and Calicophoron daubneyi from among other parasitic infections. In the present work, we focused on the role of the ecological characteristics of the pasture environment while accounting for the underlying long range geographical risk pattern. Bayesian multivariate spatial statistical analysis was used. A systematic grid (10 km×10 km) sampling approach was used. Laboratory procedures were based on the FLOTAC technique to detect and count eggs of helminths. A Geographical Information System (GIS) was constructed by using environmental data layers. Data on each of these layers were then extracted for pasturing areas that were previously digitalized aerial images of the ovine farms. Bayesian multivariate statistical analyses, including improper multivariate conditional autoregressive models, were used to select covariates on a multivariate spatially structured risk surface. Out of the 121 tested farms, 109 were positive for H. contortus, 81 for D. dendriticum, 17 for C. daubneyi and 15 for F. hepatica. The statistical analysis highlighted a north-south long range spatially structured pattern. This geographical pattern is treated here as a confounder, because the main interest was in the causal role of ecological covariates at the level of each pasturing area. A high percentage of pasture and impermeable soil were strong predictors of F. hepatica risk and a high percentage of wood was a strong predictor of C. daubneyi. A high percentage of wood, rocks and arable soil with sparse trees explained the spatial distribution of D. dendriticum. Sparse vegetation, river, mixed soil and permeable soil explained the spatial distribution of the H. contortus. Bayesian multivariate spatial analysis of parasitic infections with covariates from remote sensing at a very small geographical level allowed us to identify relevant risk predictors. All the covariates selected are consistent with the life cycles of the helminths investigated. This research showed the utility of appropriate GIS-driven surveillance systems. Moreover, spatial features can be used to tailor sampling design where the sampling fraction can be a function of remote sensing covariables.

EpiScanGIS: an online geographic surveillance system for meningococcal disease

Background

Surveillance of infectious diseases increasingly relies on Geographic Information Systems (GIS). The integration of pathogen fine typing data in dynamic systems and visualization of spatio-temporal clusters are a technical challenge for system development.

Results

An online geographic information system (EpiScanGIS) based on open source components has been launched in Germany in May 2006 for real time provision of meningococcal typing data in conjunction with demographic information (age, incidence, population density). Spatio-temporal clusters of disease detected by computer assisted cluster analysis (SaTScan™) are visualized on maps. EpiScanGIS enables dynamic generation of animated maps. The system is based on open source components; its architecture is open for other infectious agents and geographic regions. EpiScanGIS is available at , and currently has 80 registered users, mostly from the public health service in Germany. At present more than 2,900 cases of invasive meningococcal disease are stored in the database (data as of June 3, 2008).

Conclusion

EpiScanGIS exemplifies GIS applications and early-warning systems in laboratory surveillance of infectious diseases.

Serological evidence of Neospora caninum infection in mithun (Bos frontalis) from India

Studies conducted on mithuns maintained at National Research Centre on mithun, Indian Council of Agricultural Research (ICAR), Nagaland, India and mithuns found in free-ranging condition of Nagaland revealed that the overall prevalence of antibodies to Neospora caninum in mithun was 10% (95% CI=5-15) when detected by a commercially available competitive enzyme-linked immunosorbent assay test. Highest (prevalence rate=16, 95% CI=8-24) seroprevalence was found in mithuns above 3 years of age and lowest (prevalence rate=2, 95% CI=0-6) in mithuns of 2-12 months old. No statistically significant difference was observed between male (prevalence rate=7, 95% CI=0-14) and female (prevalence rate=12, 95% CI=6-18) seroprevalences. The seroprevalence was found to be higher (prevalence rate=20, 95% CI=9-31) in mithuns found in free-ranging condition in comparison to mithuns kept in semi-intensive system (prevalence rate=5, 95% CI=1-9). This is probably the first report on serological evidence of N. caninum infection in mithun. The possible role of sylvatic fauna in the epidemiology of N. caninum infection mithun is also discussed in brief.

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.

Survey of Neospora caninum and bovine herpes virus 1 coinfection in cattle

A seroprevalence survey of Neospora caninum and bovine herpesvirus 1 (BHV-1) was conducted in cattle pasturing in an area of the southern Italian Apennines to investigate the coinfection of these two pathogens. Blood samples were collected from 948 pastured cattle raised on 81 farms. Sera were tested for antibodies to N. caninum and to BHV-1 using an ELISA assay and a neutralization test, respectively. Out of the 81 farms sampled, 63 (77.8%) were positive for N. caninum and 80 (98.8%) for BHV-1. Coinfection was found in 62 (76.5%) farms. Out of the 948 bovine sera samples, 303 (32.0%) had antibodies to N. caninum and 735 (77.5%) to BHV-1. The copresence of antibodies to N. caninum and BHV-1 was found in 256 (27.0%) cattle. The logistic regression results indicated that seropositivity for BHV-1 was a risk factor for N. caninum seropositivity and seropositivity for N. caninum was a risk factor for BHV-1 seropositivity.

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.

Supranational comparison of Neospora caninum seroprevalences in cattle in Germany, The Netherlands, Spain and Sweden

Herd, within-herd and animal prevalences for Neospora caninum in beef and dairy cattle were compared between four countries. In randomly selected herds from regions of Germany, The Netherlands, Spain and Sweden that were representative for the cattle production of these countries, all animals > or = 2 years were examined serologically by enzyme-linked immunosorbent assays (ELISAs) with high test specificity (> 98.0%). In a previous study, the ELISAs had been validated against each other. Single reacting animals within a herd were confirmed by immunobloting. At the time of sampling, animal (age, breed, herdtype, sex, lactation stage) and herd data (region) were collected. Considerable differences in N. caninum herd, within-herd, and overall animal prevalence estimations were observed between countries, regions, herdtype, age categories and breeds. Herd prevalences, based on confirmation of single reactors, for dairy herds were estimated to be 16% (95%CI: 10-24%) in Sweden, 49% (95%CI: 39-59%) in Germany, 63% (95%CI: 57-69%) in Spain and 76% (95%CI: 67-84%) in The Netherlands and for beef herds 41% (95%CI: 31-50%) in Germany, 46% (95%CI: 41-51%) in Spain and 61% (95%CI: 50-72%) in The Netherlands. No beef herds were examined in Sweden. The lowest animal true prevalence was estimated in dairy cattle in Sweden (0.5% (95%CI: 0.1-0.8%)) while the highest animal true prevalence was estimated for dairy cattle in Spain (16.2% (95%CI: 14.9-17.5%)). Within-herd prevalences varied greatly, with very few farms in Sweden having more than 10% seropositive animals while in Spain more than 10% of the herds had within-herd prevalences between 50 and 100%. Seropositivity was significantly associated with herdtype (beef versus dairy), age, breed and region within countries. The results of this supranational comparative study showed that the importance of N. caninum infection varied greatly within in Europe. Estimates of prevalence can be used to calculate the economic impact of N. caninum infection as well as to evaluate the effect of prevention and control strategies over time.

Low seroprevalence of antibodies to Neospora caninum in wild canids in Israel

The role of domestic dogs in the epidemiology of Neospora caninum as well as the relationship between N. caninum infection of farm dogs and cattle were demonstrated, however, evidence is scarce regarding the role of wild canids in domestic animal neosporosis. The present study was undertaken to evaluate the role of wild canids in the epidemiology of bovine neosporosis in Israel by analyzing the prevalence of antibodies to N. caninum in wild canids. Sera samples were collected from 114 free ranging wild golden jackals (Canis aureus), 24 red foxes (Vulpes vulpes) and nine wolves (Canis lupus), which were collected in Israel during the years 1999-2004. Of a total of 147 wild canids tested antibodies to N. caninum were only found in two golden jackals with IFAT titers of 1:50, and in one red fox and one wolf with IFAT titer of 1:400. The low seroprevalence found in this study (2.7%) indicated that wild canids probably do not have an important role in the epidemiology of N. caninum in Israel. However, since the diet of different species of wild canids and even diverse populations of the same canid species vary, it is possible that other results might be obtained from specific wild canids populations, which scavenge in the vicinity of infected bovines.