What is the global economic impact of Neospora caninum in cattle - the billion dollar question

Immunogenicity, safety and dual DIVA-like character of a recombinant candidate vaccine against neosporosis in cattle

Neosporosis is the major infectious cause of abortion and reproductive losses in cattle worldwide; however, there are no available vaccines or drugs to control this disease. Recently, a dual (positive and negative) DIVA-like (Differentiation of Infected from Vaccinated Animals) vaccine was evaluated in a pregnant mouse model of neosporosis, showing promising immunogenic and protective results. The current report aimed to study the safety, the dose-dependent immunogenicity and the dual DIVA-like character of a recombinant subunit vaccine composed of the major surface antigen from Neospora caninum (rNcSAG1) and the carrier/adjuvant Heat shock protein 81.2 from Arabidopsis thaliana (rAtHsp81.2) in cattle. Healthy heifers were separated and assigned to experimental groups A-F and subcutaneously immunized with 2 doses of vaccine formulations 30 days apart as follows: A (n = 4): 50 μg rNcSAG1 + 150 μg rAtHsp81.2; B (n = 4): 200 μg rNcSAG1 + 600 μg rAtHsp81.2; C (n = 4): 500 μg rNcSAG1 + 1,500 μg rAtHsp81.2; D (n = 3): 150 μg rAtHsp81.2; E (n = 3):1,500 μg rAtHsp81.2, and F (n = 3) 2 ml of sterile PBS. The immunization of heifers with the different vaccine or adjuvant doses (groups A-E) was demonstrated to be safe and did not modify the mean value of the evaluated serum biomarkers of metabolic function (GOT/ASP, GPT/ALT, UREA, Glucose and total proteins). The kinetics and magnitude of the immune responses were dose-dependent. The higher dose of the vaccine formulation (group C) stimulated a broad and potent humoral and cellular immune response, characterized by an IgG1/IgG2 isotype profile and IFN-γ secretion. In addition, this was the first time that dual DIVA-like character of a vaccine against neosporosis was demonstrated, allowing us to differentiate vaccinated from infected heifers by two different DIVA compliant test approaches. These results encourage us to evaluate its protective efficacy in infected pregnant cattle in the future.

Estimation of economic losses due to leptospirosis in dairy cattle

There are few studies that effectively quantify the economic losses resulting from problems caused by leptospirosis in naturally infected dairy cattle. Given this gap, the objective of this study was to propose and apply a method to quantify the economic losses resulting from productive and reproductive problems in a commercial dairy herd naturally infected by Leptospira spp. For this study, the zootechnical and economic indicators at a property with Jersey cattle were analyzed during the period from 2014 to 2017. The leptospirosis outbreak occurred in 2014, and the therapeutic approach was carried out between 2015 and 2017, with the latter considered the year of control of the outbreak. The adopted integrated control strategy consisted of dividing the herd according to the serological results obtained through the microscopic agglutination test, the treatment of reagents with streptomycin, and vaccination against leptospirosis of non-reagent heifers and cows. The method used to evaluate the economic indicators of the property was the calculation of the gross margin by taking into account the implicit and explicit cost parameters associated with the manifestation of leptospirosis. The prevalence rate of leptospirosis decreased from 49.4 % in 2015 to 21.6 % in 2017. There was a reduction in the abortion rate (from 40.00 % in 2014 to 9.00 % in 2017), in the stillborn rate (from 2.63 % in 2014 to 1.69 % in 2017) and an increase in the calving rate (from 65.00 % in 2014 to 86.00 % in 2017). In addition, there were increases in the number of lactating cows (from 38 in 2014-57 in 2017) and the mean times of lactation duration, which increased from 275 days in 2014-295 days in 2017. As a result, the average annual production of milk increased from 164,655 liters in 2014-248,521 liters in 2017. In 2014, when treatment hadn't yet started, the gross margin per liter of milk sold, considering implicit and explicit costs, was US$0.00. In 2015 and 2016, US$0.27 and US$0.30 were obtained, respectively, for this variable. In 2017, with the disease under control on the property, the gross margin per liter of milk reached US$0.36. The gross margin per liter of milk sold was higher in the period when the disease was controlled, showing losses of up to 84 % of the gross margin during the outbreak. Immediate treatment of positive cows and preventive measures had a significant impact on improving the productive and economic efficiency of the property.

Functional characterization of three novel dense granule proteins in Neospora caninum using the CRISPR-Cas9 system

Neospora caninum is an obligate intracellular parasite that infects a wide range of mammalian species, and particularly causes abortions in cattle and nervous system dysfunction in dogs. Dense granule proteins (GRAs) are thought to play an important role in the mediation of host-parasite interactions and facilitating parasitism. However, a large number of potential GRAs remain uncharacterized, and the functions of most of the identified GRAs have not been elucidated. Previously, we screened a large number GRAs including NcGRA27 and NcGRA61 using the proximity-dependent biotin identification (BioID) technique. Here, we identified a novel GRA protein NcGRA85 and used C-terminal endogenous gene tagging to determine its localization at the parasitophorous vacuole (PV) in the tachyzoite. We successfully disrupted three gra genes (NcGRA27, NcGRA61 and NcGRA85) of N. caninum NC1 strain using CRISPR-Cas9-mediated homologous recombination and phenotyped the single knockout strain. The NcGRA61 and NcGRA85 genes were not essential for parasite replication and growth in vitro and for virulence during infection of mice, as observed by replication assays, plaque assays and in vitro virulence assays in mice. Deletion of the NcGRA27 gene in the NC1 strain reduced the in vitro replication and growth of the parasite, as well as the pathogenicity of the NC1 strain in mice. In summary, our findings provide a basis for in-depth studies of N. caninum pathogenesis and demonstrate the importance of NcGRA27 in parasite growth and virulence, most likely a new virulence factor of N. caninum.

Toxoplasma gondii and Neospora caninum in invasive wild boars (Sus scrofa) and hunting dogs from Brazil

The wild boar, an impactful invasive species in Brazil, is subject to population control activities, which often include the use of hunting dogs. Hunters commonly consume wild boar meat, which is also used to feed their dogs, posing a risk of Toxoplasma gondii infection for humans and both T. gondii and Neospora caninum for dogs. The study aimed to investigate the prevalence of infection in wild boars (n = 127) and hunting dogs (n = 73) from São Paulo, Rio Grande do Sul, and Paraná states. We employed histopathological, serological (indirect fluorescent antibody test), and molecular techniques (endpoint polymerase chain reaction). Histopathology slides of wild boar tissue (central nervous system, heart, skeletal muscle, liver, spleen, kidney, gastrointestinal tract, pancreas, lymph nodes, and thyroid) sections revealed no T. gondii or N. caninum cysts (0/47). Antibodies anti-T. gondii were detected in 35/108 (32.4%) and anti-N. caninum in 45/108 (41.7%) wild boars. Only 2/18 (11.1%) wild boar tissue homogenate samples tested positive for T. gondii on endpoint PCR. Hunting dogs showed antibodies against T. gondii in 62/73 (85%) and against N. caninum in 31/73 (42%). The presence of antibodies against T. gondii and N. caninum in wild boars and hunting dogs, along with T. gondii DNA detection in wild boars, indicates the circulation of these parasites. Educating hunters on preventing these foodborne diseases, including zoonotic risks, is crucial.

Seroprevalence and risk factors for Neospora caninum and Toxoplasma gondii in dairy cattle from São Paulo State, Brazil

Neospora caninum is a major cause of reproductive loss in cattle worldwide as it leads to abortion and animal repositioning. Although Toxoplasma gondii does not cause a reproductive problem in cattle, consuming raw or uncooked beef poses the risk of transmission. This study aimed to evaluate the occurrence of anti-N. caninum and anti-T. gondii antibodies in dairy cattle in the West and Northwest regions of São Paulo State, Brazil. A total of 653 serum samples from dairy cows were analyzed using an indirect immunofluorescence assay (IFA). Epidemiological data from the farms were associated with the serological results of the animals by logistic regression based on the presence of antibodies. The frequencies of the antibodies against N. caninum and T. gondii were 41.6% (272/653) and 11.5% (75/653), respectively. A statistically significant association was observed between: the serum anti-N. caninum antibodies and breed, history of food supplementation for calves, introduction of outside animals that later presented reproductive problems, and history of reproductive problems by the trimester of gestation. The present study highlights the importance of neosporosis in dairy cattle in the study regions and that the inclusion of this parasite in the investigation of animals with reproductive disorders is important.

TaqMan-quantitative PCR assays applied in Neospora caninum knock-outs generated through CRISPR-Cas9 allow to determine the copy numbers of integrated dihydrofolate reductase-thymidylate synthase drug selectable markers

As for many other organisms, CRISPR-Cas9 mediated genetic modification has gained increasing importance for the identification of vaccine candidates and drug targets in Neospora caninum, an apicomplexan parasite causing abortion in cattle and neuromuscular disease in dogs. A widely used approach for generating knock-out (KO) strains devoid of virulence factors is the integration of a drug selectable marker such as mutated dihydrofolate reductase-thymidylate synthase (mdhfr-ts) into the target gene, thus preventing the synthesis of respective protein and mediating resistance to pyrimethamine. However, CRISPR-Cas9 mutagenesis is not free of off-target effects, which can lead to integration of multiple mdhfr-ts copies into other sites of the genome. To determine the number of integrated mdhfr-ts in N. caninum, a duplex quantitative TaqMan PCR was developed. For this purpose, primers were designed that amplifies a 106 bp fragment from wild-type (WT) parasites corresponding to the single copy wtdhfrs-ts gene, as well as the mutated mdhfrs-ts present in KO parasites that confers resistance and were used simultaneously with primers amplifying the diagnostic NC5 gene. Thus, the dhfr-ts to NC5 ratio should be approximately 1 in WT parasites, while in KO parasites with a single integrated mdhrf-ts gene this ratio is doubled, and in case of multiple integration events even higher. This approach was applied to the Neospora KO strains NcΔGRA7 and NcΔROP40. For NcΔGRA7, the number of tachyzoites determined by dhfr-ts quantification was twice the number of tachyzoites determined by NC5 quantification, thus indicating that only one mdhfr-ts copy was integrated. The results obtained with the NcΔROP40 strain, however, showed that the number of dhfr-ts copies per genome was substantially higher, indicating that at least three copies of the selectable mdhfr-ts marker were integrated into the genomic DNA during gene editing by CRISPR-Cas9. This duplex TaqMan-qPCR provides a reliable and easy-to-use tool for assessing CRISPR-Cas9 mediated mutagenesis in WT N. caninum strains.

The role of genetic variability of the host on the resistance to Neospora caninum infection in cattle

Neospora caninum is one of the most frequently diagnosed abortifacient pathogens in cattle. There is abundant genomic information about the parasite itself, but very little is known about the genetic variability of resistance in the most common intermediate host. The aim of this review was to compile all the available information about the genetic variability associated with the resistance to N. caninum both between and within cattle breeds. We systematically searched for published studies that investigated the influence of genetics of the host on the prevalence of N. caninum and risk of abortion. Beyond the potential confounding effects of feeding systems, management and animal density, some lines of evidence suggest that Holstein, the most popular breed for milk production, has a comparatively higher risk of abortion due to infections by N. caninum, whereas some beef breeds from Continental Europe seem to be more resistant. It is still not clear if different genetic mechanisms of resistance are involved in the two known routes of infection: postnatal ingestion of oocysts or transplacental transmission from the infected dam to the fetus. Genomic information associated with susceptibility to infection and risk of abortion in different cattle breeds is still scarce. The information reported here could be useful to identify new research alternatives and to define novel strategies to deal with this major problem of animal production.

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-level prevalence of bovine leukemia virus, Salmonella Dublin and Neospora caninum in Alberta, Canada, dairy herds using ELISA on bulk tank milk samples

Endemic infectious diseases remain a major challenge for dairy producers worldwide. For effective disease control programs, up-to-date prevalence estimates are of utmost importance. The objective of this study was to estimate the herd-level prevalence of bovine leukemia virus (BLV), Salmonella Dublin, and Neospora caninum in dairy herds in Alberta, Canada using a serial cross-sectional study design. Bulk tank milk samples from all Alberta dairy farms were collected 4 times, in December 2021 (n = 489), April 2022 (n = 487), July 2022 (n = 487), and October 2022 (n = 480), and tested for antibodies against BLV, S. Dublin, and N. caninum using ELISAs. Herd-level apparent prevalence was calculated as positive samples divided by total tested samples at each time point. A mixed effect modified Poisson regression model was employed to assess the association of prevalence with region, herd size, herd type, and type of milking system. Apparent prevalence of BLV was 89.4, 88.7, 86.9 and 86.9% in December, April, July, and October, respectively, whereas for S. Dublin apparent prevalence was 11.2, 6.6, 8.6, and 8.5%, and for N. caninum apparent prevalence was 18.2, 7.4, 7.8, and 15.0%. For BLV, S. Dublin and N. caninum, a total of 91.7, 15.6, and 28.1% of herds, respectively, were positive at least once, whereas 82.5, 3.6, and 3.0% of herds were ELISA-positive at all 4 times. Compared with the north region, central Alberta had a high prevalence (prevalence ratio (PR) = 1.13) of BLV-antibody positive herds, whereas south Alberta had a high prevalence (PR = 2.56) of herds positive for S. Dublin antibodies. Furthermore, central (PR = 0.52) and south regions (PR = 0.46) had low prevalence of N. caninum-positive herds compared with the north. Hutterite colony herds were more frequently BLV-positive (PR = 1.13) but less frequently N. caninum-positive (PR = 0.47). Large herds (>7,200 L/day milk delivered ∼ > 250 cows) were 1.1 times more often BLV-positive, whereas small herds (≤3,600 L/day milk delivered ∼ ≤ 125 cows) were 3.2 times more often N. caninum-positive. For S. Dublin, Hutterite-colony herds were less frequently (PR = 0.07) positive than non-colony herds only in medium and large stratum but not in small stratum. Moreover, larger herds were more frequently (PR = 2.20) S. Dublin-positive than smaller herds only in non-colony stratum but not in colony stratum. Moreover, N. caninum prevalence was 1.6 times higher on farms with conventional milking systems compared with farms with an automated milking system. These results provide up-to-date information of the prevalence of these infections that will inform investigations of within-herd prevalence of these infections and help in devising evidence-based disease control strategies.

Global losses due to dairy cattle diseases: A comorbidity-adjusted economic analysis

An economic simulation was carried out over 183 milk-producing countries to estimate the global economic impacts of 12 dairy cattle diseases and health conditions: mastitis (subclinical and clinical), lameness, paratuberculosis (Johne's disease), displaced abomasum, dystocia, metritis, milk fever, ovarian cysts, retained placenta, and ketosis (subclinical and clinical). Estimates of disease impacts on milk yield, fertility, and culling were collected from the literature, standardized, meta-analyzed using a variety of methods ranging from simple averaging to random-effects models, and adjusted for comorbidities to prevent overestimation. These comorbidity-adjusted disease impacts were then combined with a set of country-level lactational incidence and/or prevalence estimates, herd characteristics, and price estimates within a series of Monte Carlo simulations that estimated and valued the economic losses due to these diseases. It was estimated that total annual global losses are USD 65 billion (B). Subclinical ketosis, clinical mastitis, and subclinical mastitis were the costliest diseases modeled, resulting in mean annual global losses of approximately USD 18B, USD 13B, and USD 9B, respectively. Estimated global annual losses due to clinical ketosis, displaced abomasum, dystocia, lameness, metritis, milk fever, ovarian cysts, paratuberculosis, and retained placenta were estimated to be USD 0.2B, 0.6B, 0.6B, 6B, 5B, 0.6B, 4B, 4B, and 3B, respectively. Without adjustment for comorbidities, when statistical associations between diseases were disregarded, mean aggregate global losses would have been overestimated by 45%. Although annual losses were greatest in India (USD 12B), the USA (USD 8B), and China (USD 5B), depending on the measure of losses used (losses as a percent of GDP, losses per capita, losses as a percent of gross milk revenue), the relative economic burden of these dairy cattle diseases across countries varied markedly.

PRESENCE OF ANTI-NEOSPORA CANINUM ANTIBODIES IN TEMAZATE DEER (MAZAMA TEMAMA) AND WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS) FROM THE CENTRAL REGION OF VERACRUZ, MEXICO

This study documents the presence of anti-Neospora caninum antibodies and their association with certain risk factors in 2 deer species from the central region of Veracruz State, Mexico. A total of 90 blood samples, 20 from temazate deer (Mazama temama) and 70 from white-tailed deer (Odocoileus virginianus), were taken from 3 farms, and serum samples were subjected to ELISA indirect test to detect N. caninum antibodies; the association between the serological status and the possible risk factors was then estimated. The overall presence of anti-N. caninum antibodies was 57.7% (52/90; 95% CI 46.9-67.9), with positive animals identified on all farms; in white-tailed deer it was 57% and in temazate deer 60%. Prevalence was higher in females than males. Adult animals had a higher prevalence than young ones. The risk analysis identified the age in the adult animal category (odds ratio 5.8) as being associated with the presence of anti-N. caninum antibodies. These results provide evidence of the significant contamination of oocysts in the environment and allow us to estimate the contribution of deer to the sylvatic cycle.

Cytokine production by bovine adipose tissue stromal vascular fraction cells upon Neospora caninum stimulation

In bovines few studies addressed the contribution of adipose tissue to the host immune response to infection. Here we evaluated the in vitro response of bovine adipose tissue stromal vascular fraction (SVF) cells to the protozoan parasite Neospora caninum, using live and freeze-killed tachyzoites. Live N. caninum induced the production of IL-6, IL-1β and IL-10 by SVF cells isolated from subcutaneous adipose tissue (SAT), while in mesenteric adipose tissue (MAT) SVF cell cultures only IL-1β and IL-10 production was increased, showing slight distinct responses between adipose tissue depots. Whereas a clear IL-8 increase was detected in peripheral blood leucocytes (PBL) culture supernatants in response to live N. caninum, no such increase was observed in SAT or MAT SVF cell cultures. Nevertheless, in response to LPS, increased IL-8 levels were detected in all cell cultures. IL-10 levels were always increased in response to stimulation (live, freeze-killed N. caninum and LPS). Overall, our results show that bovine adipose tissue SVF cells produce cytokines in response to N. caninum and can therefore be putative contributors to the host immune response against this parasite.

Neospora caninum peroxiredoxin 1 is an essential virulence effector with antioxidant function

Neospora caninum, an obligate intracellular parasitic protozoan discovered by Dubey in 1988, is the pathogen of neosporosis, which causes neurological symptoms in dogs and abortions in cows. Since there is no effective drug or vaccine against N. caninum, a deeper understanding of the molecules critical to parasite survival inside host cells is necessary. This study aimed to determine the role of N. caninum peroxiredoxin 1 (NcPrx1) in maintaining redox homeostasis and virulence of N. caninum. By determining the localization of NcPrx1 protein and establishing NcPrx1 gene knockout strain (ΔNcPrx1), the roles of NcPrx1 in N. caninum for invasion, replication, growth, oxidative stress, as well as pathogenicity were investigated. Our results showed that a predicted Alkyl Hydroperoxide1 (AHP1) domain was found in the amino acid sequence of NcPrx1, which displayed a high degree of similarity to homologs of several protozoa. Immunofluorescence assay (IFA) indicated that NcPrx1 was a cytoplasmic protein in N. caninum tachyzoites. Compared to wild type (WT) strain, ΔNcPrx1 strain showed reduced plaque area, invasion and egress rates. Reactive oxygen species (ROS) and malondialdehyde (MDA) were accumulated, and total antioxidant capacity (T-AOC) was attenuated in ΔNcPrx1 tachyzoites, which indicated that ΔNcPrx1 strain was more sensitive to oxidative stress. Furthermore, ΔNcPrx1 strain-infected C57BL/6 mice showed improved survival rate, reduced parasite burden, alleviated pathological changes in tissues, and decreased secretions of IL-6, IL-12, TNF-α, and IFN-γ in serum compared to the WT strain group. These findings suggested that NcPrx1 was a virulence factor of N. caninum which played an important role in maintaining the redox homeostasis of the parasite.

Macrophage migration inhibitory factor favors Neospora caninum infection in mice

Neospora caninum is a protozoan parasite with worldwide incidence, acting as a major cause of reproductive failures in ruminants and neuromuscular symptoms in dogs. Macrophage Migration Inhibitory Factor (MIF) is produced by several cell types and exhibits a central role in immune responses against intracellular pathogens. The present study aimed to comprehend the role of MIF in the relationship between N. caninum and its host. We used in vivo, in vitro and ex vivo experiments in a model of infection based on genetically deficient mice to analyze the infection kinetics and inflammatory markers. MIF production was measured in response to N. caninum during the acute and chronic phases of the infection. While Mif-/- mice survived lethal doses of NcLiv tachyzoites, sublethal infections in these mice showed that parasite burden was controlled in target tissues, alongside with reduced inflammatory infiltrates detected in lung and brain sections. TNF was increased at the initial site of the infection in genetically deficient mice and the MIF-dependent reduction was confirmed in vitro with macrophages and ex vivo with primed spleen cells. In sum, MIF negatively regulated host immunity against N. caninum, favoring disease progression.

Establishment of an ultrasensitive and visual detection platform for Neospora caninum based-on the RPA-CRISPR/Cas12a system

Neospora caninum is a protozoan parasite that causes neosporosis in cattle, and leads to a high rate of abortion and severe financial losses. Rapid and accurate detection is particularly important for preventing and controlling neosporosis. In our research, a highly effective diagnostic technique based on the RPA-CRISPR/Cas system was created to successfully identify N. caninum against the Nc5 gene, fluorescent reporter system and the lateral flow strip (LFS) biosensor were exploited to display results. The specificity and sensitivity of the PRA-CRISPR/Cas12a assay were evaluated. We discovered that it was highly specific and did not react with any other pathogens. The limit of detection (LOD) for this technology was as low as one parasite per milliliter when employing the fluorescent reporter system, and was approximately ten parasites per milliliter based on the LFS biosensor and under blue or UV light. Meanwhile, the placental tissue samples were detected by our RPA-CRISPR/Cas12a detection platform were completely consistent with that of the nested PCR assay (59.4 %, 19/32). The canine feces were detected by our RPA-CRISPR/Cas12a detection platform were completely consistent with that of the nested PCR assay (8.6 %, 6/70). The RPA-CRISPR/Cas12a detection procedure was successfully finished in within 90 min and offers advantages of high sensitivity and specificity, speed and low cost. The technique was better suitable for extensive neosporosis screening in non-laboratory and resource-constrained locations. This study provided a new strategy for more rapid and portable identification of N. caninum.

Protective effect of Inonotus obliquus polysaccharide on mice infected with Neospora caninum

The study aimed to explore the protective effects of Inonotus obliquus polysaccharide (IOP) on Neospora caninum (N. caninum) infection. Our data showed that the survival rate of the mice was the highest and the survival time was the longest when the IOP was 2 mg/10 g. In agreement with these observations, IOP alleviated the pathological damage in the various organs and tissues of the mice. Compared with that in the Neosporidium infection model group, the content of N. caninum in the heart, liver, spleen, lung, kidney and brain, determined through HE staining, was significantly lower. In addition, IOP inhibited the levels of immunoglobulin G1 (IgG1) and immunoglobulin G2 (IgG2a) from the 21st to 42nd day of the administration group, whereas the levels of interleukin-12 (IL-12) and serum tumor necrosis factor alpha (TNF-α) were down-regulated at 7 d - 42 d. The production of CD4+ T lymphocytes was promoted, the number of CD8+ T lymphocytes were significantly lower and the CD4+/CD8+ ratio was significantly elevated. Furthermore, IOP effectively balanced the levels of hormones including gonadotropin-releasing hormone (GnRH), luteotropic hormone (LH) and testosterone (T) in male mice, and progesterone (PROG), estradiol (E2) and prolactin (PRL) in female mice. These findings demonstrate that IOP exerts protective effects against pathological damage caused by N. caninum infection in mice, and improve the immune function of the organism and regulate the secretion balance of sex hormones.

Seroprevalence of Coxiella burnetii, Leptospira interrogans serovar hardjo, and Brucella species and associated reproductive disorders in cattle in southwest Ethiopia

In Ethiopia, Coxiella burnetii, Leptospira Hardjo, and Brucella spp are recognized as the primary factors contributing to cattle reproductive issues. A cross-sectional study was conducted in southwest Ethiopia from October 2020 to October 2021 to assess the risk of reproductive disorders associated with L. Hardjo, Coxiella burnetii, and Brucella spp. Moreover, the study aimed to identify the factors associated with reproductive disorders. Using an indirect ELISA, antibodies against these pathogens were observed in serum samples collected from 461 cattle. We employed multivariable random effect logistic regression analysis to identify potential risk factors associated with reproductive disorders in cattle. The study areas showed a prevalence of 25.16 % (95 % CI: 21.20-29.12) for cattle reproductive disorders. The presence of Leptospira Hardjo (OR = 2.9, 95 % CI: 1.17-4.02) and Coxiella burnetii (OR = 3.0, 1.49-5.94) antibodies was associated to the occurrence of cattle reproductive disorders. Seropositivity to pathogens B. abortus, C. burnetii, and L. Hardjo, along with co-infection of all three, showed association with cattle abortion. The presence of L. Hardjo seropositivity and co-infection with C. burnetii were related to dystocia in cattle. Cattle with retained fetal membranes were associated with co-infection seropositivity to these pathogens. Additionally, B. abortus seropositivity was linked to cases of repeated breeding in cattle. Age, breeding practices, and dog access to cattle showed associations with reproductive disorders, with odds ratios of 2.3 (95 % CI: 2.03-4.69), 2.9 (95 % CI: 1.83-4.82), and 6.5 (95 % CI: 1.04-2.53) respectively. This research indicates that Brucella abortus, Coxiella burnetii, and Leptospira Hardjo, which are responsible for severe zoonotic diseases, have a substantial negative impact on cattle production by causing reproductive disorders. To address the transmission of these diseases, it is essential to implement effective mitigation strategies and enhance public awareness. Additional investigation is necessary to identify and understand the factors contributing to cattle reproductive disorders in the specified area.

Evaluation of Immunodiagnostic Performances of Neospora caninum Peroxiredoxin 2 (NcPrx2), Microneme 4 (NcMIC4), and Surface Antigen 1 (NcSAG1) Recombinant Proteins for Bovine Neosporosis

Bovine neosporosis is among the main causes of abortion in cattle worldwide, causing serious economic losses in the beef and dairy industries. A highly sensitive and specific diagnostic method for the assessment of the epidemiology of the disease, as well as it surveillance and management, is imperative, due to the absence of an effective treatment or vaccine against neosporosis. In the present study, the immunodiagnostic performance of Neospora caninum peroxiredoxin 2 (NcPrx2), microneme 4 (NcMIC4), and surface antigen 1 (NcSAG1) to detect IgG antibodies against N. caninum in cattle were evaluated and compared with that of the indirect fluorescent antibody test (IFAT). The results revealed that NcSAG1 had the highest sensitivity and specificity, with values of 88.4% and 80.7%, respectively, followed by NcPrx2, with a high sensitivity of 87.0% but a low specificity of 67.0%, whereas NcMIC4 showed sensitivity and specificity of 84.1% and 78.9%, respectively, when compared with IFAT. A high degree of agreement was observed for NcSAG1 (k = 0.713) recombinant protein, showing the highest diagnostic capability, followed by NcMIC4 (k = 0.64) and NcPrx2 (k = 0.558). The present study demonstrates that NcSAG1 is helpful as an antigen marker and also demonstrates the potential immunodiagnostic capabilities of NcPrx2 and NcMIC4, which could serve as alternative diagnostic markers for detecting N. caninum infection in cattle. These markers may find utility in future treatment management, surveillance, and risk assessment of neosporosis in livestock or other animal host species. Further research should be directed toward understanding the in vivo immune response differences resulting from immunization with both recombinant proteins.

Working towards the development of vaccines and chemotherapeutics against neosporosis-With all of its ups and downs-Looking ahead

Neospora caninum is an apicomplexan and obligatory intracellular parasite, which is the leading cause of reproductive failure in cattle and affects other farm and domestic animals, but also induces neuromuscular disease in dogs of all ages. In cattle, neosporosis is an important health problem, and has a considerable economic impact. To date there is no protective vaccine or chemotherapeutic treatment on the market. Immuno-prophylaxis has long been considered as the best control measure. Proteins involved in host cell interaction and invasion, as well as antigens mediating inflammatory responses have been the most frequently assessed vaccine targets. However, despite considerable efforts no effective vaccine has been introduced to the market to date. The development of effective compounds to limit the effects of vertical transmission of N. caninum tachyzoites has emerged as an alternative or addition to vaccination, provided suitable targets and safe and efficacious drugs can be identified. Additionally, the combination of both treatment strategies might be interesting to further increase protectivity against N. caninum infections and to decrease the duration of treatment and the risk of potential drug resistance. Well-established and standardized animal infection models are key factors for the evaluation of promising vaccine and compound candidates. The vast majority of experimental animal experiments concerning neosporosis have been performed in mice, although in recent years the numbers of experimental studies in cattle and sheep have increased. In this review, we discuss the recent findings concerning the progress in drug and vaccine development against N. caninum infections in mice and ruminants.

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.

Immunisation with Neospora caninum subunits rsNcSAG4 and rsNcGRA1 (NcSAG4 and NcGRA1 epitopes construct) in BALB/c mice: the profile of the immune response and controlling the vertical transmission

Neospora caninum is an apicomplexan protozoan that causes neosporosis, which has a high economic impact on cattle herds with no available vaccine. During infection, the secretion of dense granules and the expression of surface antigens play an important role in hosting immunomodulation. However, some epitopes of those antigens are immunogenic, and using these fractions could improve the subunit antigens in vaccine design. This study evaluates the recombinant peptides rsNcGRA1 and rsNcSAG4 derived from NcGRA1 and NcSAG4 native antigens as vaccine candidates produced by a fermentative process in the yeast culture system of Komagataella phaffii strain Km71, confirmed by colony PCR, SDS-PAGE, and western blotting. The assay was conducted in BALB/c mice using the peptides at low (25 μg) and standard (50 μg) dosages in monovalent and combined administrations at three time points with saponin as an adjuvant assessing the immunogenicity by antibodies response and cytokine production. We challenge the females after pregnancy confirmation using 2 × 105 NC-1 tachyzoites previously propagated in Vero cells. We assessed the chronic infection in dams and vertical transmission in the offspring by PCR and histopathology. Mice, especially those immunised with combined peptides and monovalent rsNcGRA1 at a standard dose, controlling the chronic infection in dams with the absence of clinical manifestations, showed an immune response with induction of IgG1, a proper balance between Th1/Th2 cytokines and reduced vertical transmission in the pups. In contrast, dams inoculated with a placebo vaccine showed clinical signs, low-scored brain lesions, augmented chronic infection with 80% positivity, 31% mortality in pups, and 81% vertical transmission. These findings indicate that rsNcGRA1 peptides in monovalent and combined with rsNCSAG4 at standard dose are potential vaccine candidates and improve the protective immune response against neosporosis in mice.

Parasitism in viviparous vertebrates: an overview

The reproductive mode of viviparity has independently evolved in various animal taxa. It refers to the condition in which the embryos or young develop inside the female's body during gestation, providing advantages such as protection, nutrition, and improved survival chances. However, parasites and diseases can be an evolutionary force that limit the host's resources, leading to physiological, morphological, and behavioral changes that impose additional costs on both the pregnant female and her offspring. This review integrates the primary literature published between 1980 and 2021 on the parasitism of viviparous hosts. We describe aspects such as reproductive investment in females, offspring sex ratios, lactation investment in mammals, alterations in birth intervals, current reproductive investment, variations between environments, immune system activity in response to immunological challenges, and other factors that can influence the interaction between viviparous females and parasites. Maintaining pregnancy incurs costs in managing the mother's resources and regulating the immune system's responses to the offspring, while simultaneously maintaining an adequate defense against parasites and pathogens. Parasites can significantly influence this reproductive mode: parasitized females adjust their investment in survival and reproduction based on their life history, environmental factors, and the diversity of encountered parasites.

Neospora caninum seroprevalence in water buffaloes in Guangxi, China

Neospora caninum is an important obligate intracellular apicomplexan parasite that causes spontaneous abortions in cattle and leads to huge economic losses to the farming industry. Although a high prevalence of N. caninum infection has been reported in Asia, data on the prevalence of water buffaloes in China remain unclear. To understand the seroprevalence of N. caninum infection in water buffaloes and its definitive host dogs in China, a total of 987 water buffalo sera from Guangxi Province were tested using an indirect enzyme-linked immunosorbent assay. We obtained an overall seroprevalence of 50.9% (502/987) for water buffalo samples. And the positive rate was higher in border cities (56.8%, 425/748) than in central cities (32.3%, 77/239). We further tested 240 serum samples from dogs in Guangxi and found an overall prevalence of 57.9% (139/240). The high prevalence of N. caninum infection in both dogs and water buffaloes was first reported in southern China, and these data will surely contribute to the prevention and control of the disease.

First Molecular Detection of Neospora caninum in Feces of Grey Wolf (Canis lupus) and Golden Jackal (Canis aureus) Populations in Slovenia

Neospora caninum is an obligate intracellular parasite that causes reproductive disorders and major economic losses in cattle, and induces neuromuscular disorders in canids. Exogenous infections are becoming increasingly important due to disease outbreaks. The sylvatic life cycle of N. caninum interferes with the domestic dog-ruminant life cycle, but understanding of it is scarce. The population of wild canids may play an important role in parasite dispersion. Feces from 42 grey wolves (Canis lupus) and 39 golden jackals (Canis aureus) were analyzed for the N. caninum Nc5 gene using a novel real-time PCR (qPCR) with a detection limit of 5 targets/µL in clinical samples. Three wolves (3/42; 7.1%) and one golden jackal (1/39; 2.6%) tested positive, which is the first detection of N. caninum in the population of grey wolves in Slovenia and the first detection of N. caninum DNA in the feces of a golden jackal. In addition to the grey wolf, we propose the golden jackal as a potential definitive host with hypothetical epidemiological importance for the sylvatic-domestic life cycle of N. caninum, due to its proximity to human habitats and its rapid expansion throughout Europe.

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

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

Evidence of Australian wild deer exposure to N. caninum infection and potential implications for the maintenance of N. caninum sylvatic cycle

Infections with the coccidian parasite Neospora caninum affect domestic and wild animals worldwide. In Australia, N. caninum infections cause considerable losses to the cattle industry with seroprevalence of 8.7% in beef and 10.9% in dairy cattle. Conversely, the role of wild animals, in maintaining the parasite cycle is also unclear. It is possible that native or introduced herbivorous species could be reservoir hosts of N. caninum in Australia, but to date, this has not been investigated. We report here the first large-scale screening of N. caninum antibodies in Australian wild deer, spanning three species (fallow, red and sambar deer). Consequently, we also assessed two commercial cELISA tests validated for detecting N. caninum in cattle for their ability to detect N. caninum antibodies in serum samples of wild deer. N. caninum antibodies were detected in 3.7% (7/189, 95% CI 1.8 - 7.45) of the wild deer serum samples collected in south-eastern Australia (n = 189), including 97 fallow deer (Dama dama), 14 red deer (Cervus elaphus), and 78 sambar deer (Rusa unicolor). Overall, our study provides the first detection of N. caninum antibodies in wild deer and quantifies deer's potential role in the sylvatic cycle of N. caninum.

Seroprevalence of Neospora caninum antibodies in dogs, cows, and humans in Assiut province, Egypt: a pilot study

Neospora caninum is an intracellular coccidian parasite infecting a broad range of hosts globally. Despite the existence of several epidemiological studies on neosporosis, there is a limited knowledge regarding the prevalence of N. caninum infection among dogs, cows, and humans in Egypt. To address this knowledge gap, we conducted an epidemiological investigation in the Assiut province of Egypt to determine the seropositivity of N. caninum infection among cows, dogs, and pregnant women, as well as the associated risk factors. By employing an indirect enzyme linked immunosorbent assay, we found specific N. caninum IgG antibodies in 6% (6 of 100) and 2.33% (1 of 43) of cows and dogs' sera, respectively. However, we are unable to detect antibodies in the 48 tested human sera. Moreover, no statistical significance was observed among the analyzed risk factors associated with seropositive cows and dogs. Our study highlights the presence of N. caninum in cows and dogs in the Assiut province, Egypt. Further, it underscores the need for improved comprehensive surveillance of N. caninum infection in a large population of cattle across various locations to obtain a better understanding of the economic burden associated with the disease.

Graphical abstract

New insights into phenotype and genotype relationships in Neospora caninum

The successful isolation of four new Neospora caninum strains from different regions and with different backgrounds (obtained from an abortion storm or congenitally infected and asymptomatic calves) allowed us previously to characterize natural isolates, finding differences in phenotype and microsatellites. Given the variability observed, we wondered in this work whether these differences had consequences in virulence, invasion and vertical transmission using cell cultures and murine neosporosis models. In addition, we performed the genomic analysis and SNP comparative studies of the NcURU isolates. The results obtained in this work allowed us to establish that NcURU isolates are of low virulence and have unique phenotypic characteristics. Likewise, sequencing their genomes has allowed us to delve into the genetic singularities underlying these phenotypes, as well as the common mutated genes. This work opens a new perspective for diagnostic purposes and formulating possible vaccines based on attenuated strains.

Characterization of Neospora caninum virulence factors NcGRA7 and NcROP40 in bovine target cells

Bovine neosporosis is one of the major causes of reproductive failure in cattle worldwide, and differences in virulence between isolates have been widely shown. However, the molecular basis and mechanisms underlying virulence in Neospora caninum are mostly unknown. Recently, we demonstrated the involvement of NcGRA7 and NcROP40 in the virulence of N. caninum in a pregnant murine model using single knockout mutants in these genes generated by CRISR/Cas9 technology. In this study, the role of these proteins was investigated in two in vitro models using bovine target cells: trophoblast (F3 cell line) and monocyte-derived macrophages (BoMØ). The proliferation capacity of the single knockout mutant parasites was compared to the wild-type strain, the Nc-Spain7 isolate, using both cell populations. For the bovine trophoblast, no differences were observed in the growth of the defective parasites compared to the wild-type strain, neither in the proliferation kinetics nor in the competition assay. However, in naïve BoMØ, a significant decrease in the proliferation capacity of the mutant parasites was observed from 48 h pi onwards. Stimulation of BoMØ with IFN-γ showed a similar inhibition of tachyzoite growth in defective and wild-type strains in a dose-dependent manner. Finally, BoMØ infected with knockout parasites showed higher expression levels of TLR3, which is involved in pathogen recognition. These results suggest that NcGRA7 and NcROP40 may be involved in the manipulation of innate immune defense mechanisms against neosporosis and confirm the usefulness of the BoMØ model for the evaluation of N. caninum virulence mechanisms. However, the specific functions of these proteins remain unknown, opening the way for future research.

Whole-transcriptome analysis reveals virulence-specific pathogen-host interactions at the placenta in bovine neosporosis

Research on bovine neosporosis has achieved relevant milestones, but the mechanisms underlying the occurrence of foetal death or protection against foetal death remain unclear. In a recent study, placentas from heifers challenged with the high-virulence isolate Nc-Spain7 exhibited focal necrosis and inflammatory infiltrates as soon as 10 days post-infection (dpi), although parasite detection was minimal. These lesions were more frequent at 20 dpi, coinciding with higher rates of parasite detection and the occurrence of foetal death in some animals. In contrast, such lesions were not observed in placentas from animals infected with the low-virulence isolate Nc-Spain1H, where the parasite was detected only in placenta from one animal at 20 dpi. This work aimed to study which mechanisms are triggered in the placentas (caruncles and cotyledons) of these pregnant heifers at early stages of infection (10 and 20 dpi) through whole-transcriptome analysis. In caruncles, infection with the high-virulence isolate provoked a strong proinflammatory response at 10 dpi. This effect was not observed in heifers infected with the low-virulence isolate, where IL-6/JAK/STAT3 signalling and TNF-alpha signalling via NF-κB pathways were down-regulated. Interestingly, the expression of E2F target genes, related to restraining the inflammatory response, was higher in these animals. At 20 dpi, more pronounced proinflammatory gene signatures were detectable in heifers infected with the high-virulence isolate, being more intense in heifers carrying dead fetuses. However, the low-virulence isolate continued without activating the proinflammatory response. In cotyledons, the response to infection with the high-virulence isolate was similar to that observed in caruncles; however, the low-virulence isolate induced mild proinflammatory signals at 20 dpi. Finally, a deconvolutional analysis of gene signatures from both placentome tissues revealed a markedly higher fraction of activated natural killers, M1 macrophages and CD8+ T cells for the high-virulence isolate. Therefore, our transcriptomic analysis supports the hypothesis that an intense immune response probably triggered by parasite multiplication could be a key contributor to abortion. Further studies are required to determine the parasite effectors that govern the distinct interactions of high- and low-virulence isolates with the host, which could help elucidate the molecular processes underlying the pathogenesis of neosporosis in cattle.

Epidemiological evaluation of Neospora caninum in dairy animals

The purpose of the study is to explore the epidemiological information concerning the spread of neosporosis in the Moscow region (Russian Federation) and Almaty region (Republic of Kazakhstan). The study is conducted in 2019 in the Moscow region (Russian Federation) and Almaty region (Republic of Kazakhstan). The study sample includes 800 cows (400 animals at each of the two locations), 100 at each of the 4 cattle farms in the Moscow region and 100 at each of the 4 cattle farms in the Almaty region. There were more seropositive cows on the rest of farms as compared to farm No. 1: 1.9 times more on farm No. 2 (p ≤ 0.01), 2.4 times more on farm No. 3 (p ≤ 0.001), and almost 4 times more on farm No. 4 (p ≤ 0.0001). In terms of the abortion rates, the maximum difference between the farms was 5-fold in the Moscow region (p ≤ 0.0001) and 3-fold in the Almaty region (p ≤ 0.001). Positive correlations exist between all the studied parameters (the proportion of seropositive animals, the proportion of seroprevalent animals, the abortion rate, and the stillbirth rate). The results of the study are mainly extremely valuable for the global economy, because the Republic of Kazakhstan and the Russian Federation occupy an important place in the export of meat and dairy products.

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.

Review: Bovine foetal mortality - risk factors, causes, immune responses and immuno-prophylaxis

This review of bovine foetal mortality (>42 d gestation) concluded that while the majority of risk factors associated with sporadic loss operate at animal-level, e.g. foetal plurality, those that operate at herd-level, e.g. some foetopathogenic infections, are more likely to result in abortion outbreaks. While the causes of foetal mortality have traditionally been classified as infectious and non-infectious, in fact, the latter category is a diagnosis of exclusion, generally without determination of the non-infectious cause. This review has also established that the traditional dichotomisation of infectious agents into primary and secondary pathogens is based on a flawed premise and these terms should be discontinued. The delicate balance of the maternal gestational immune system between not rejecting the allograft (conceptus) but rejecting (attacking) foetopathogens is stage-of-pregnancy-dependent thus the timing of infection determines the clinical outcome which may result in persistent infection or foetal mortality. Utilisation of our knowledge of the materno-foetal immune responses to foetopathogenic infection has resulted in the development of numerous mono- and polyvalent vaccines for metaphylactic or prophylactic control of bovine foetal mortality. While some of these have been shown to significantly contribute to reducing the risk of both infection and foetal mortality, others have insufficient, or conflicting evidence, on efficacy. However, recent developments in vaccinology, in particular the development of subunit vaccines and those that stimulate local genital tract immunity, show greater promise.

Seroprevalence and associated risk factors of bovine neosporosis in the Khomas region of Namibia

Neospora caninum is a coccidian parasite that occurs worldwide and is one of the most important causes of abortion, especially in cattle. However, no studies have been performed in Namibia to determine the N. caninum status in livestock. Therefore, this study aimed to determine the seroprevalence of N. caninum in cattle and the associated risk factors in the Khomas region of Namibia. A total of 736 sera were collected from cows in 32 farming establishments. These comprised 698 beef and 38 dairy cattle sera and were tested using a commercial enzyme-linked immunosorbent assay (ELISA) kit. Questionnaires were concurrently administered to determine possible risk factors associated with N. caninum seropositivity. A total of 42 sera were positive (all beef), giving an animal-level seroprevalence rate of 5.7%. Eight of the 32 establishments had at least one positive animal, giving a herd-level seroprevalence of 25%. There was no significant association between seropositivity and the presence of dogs, jackals, history of abortions, farm size, number of cattle or average annual rainfall. The establishments with moderate to high numbers of Feliformia were 9.8 times more likely to be seropositive to N. caninum than those with none to low levels of the former (p = 0.0245). The authors concluded that the seroprevalence level of N. caninum in the Khomas region was relatively low compared with other parts of the world and that the role of Feliformia in the epidemiology of bovine neosporosis needed to be further investigated.Contribution: Serological evidence of bovine neosporosis and the associated risk factors are reported in Namibia for the first time. This study contributes to the scientific body of knowledge on N. caninum in Africa, which is currently limited.

Seroprevalence and Factors Associated with Toxoplasma gondii, Neospora caninum, and Besnoitia besnoiti Infections in Cattle and Goats in Selangor, Malaysia

Apicomplexan parasites such as Toxoplasma gondii, Neospora caninum, and Besnoitia besnoiti are widely recognized as causes of production diseases in ruminants. This study aimed to investigate the serological occurrence of T. gondii, N. caninum, and B. besnoiti in cattle and goats from smallholder farms in Selangor, Malaysia. A cross-sectional study was conducted on 19 farms by collecting 404 bovine (n = 225) and caprine (n = 179) serum samples, which were then essayed for T. gondii, N. caninum, and B. besnoiti antibodies using commercially available ELISA test kits. Farm data and animal characteristics were documented, and the data were analyzed using descriptive statistics and logistic regression models. The seroprevalence of T. gondii at animal and farm levels in cattle was 5.3% (95% CI 1.2-7.4%) and 36.8% (95% CI 22.4-58.0%), respectively. Animal-level seropositivity for N. caninum was 2.7% (95% CI 0.4-4.2%) and 5.7% for B. besnoiti (95% CI 1.3-9.4%) with corresponding farm-level seropositivity of 21.0% and 31.5%, respectively. For the goat samples, a high animal- (69.8%; 95% CI 34.1-82.0%) and farm-level (92.3%) seropositivity was recorded for T. gondii, but was relatively lower for N. caninum antibodies, at 3.9% (95% CI 1.5-6.2%) and 38.4% (5/13). The factors associated with T. gondii seropositivity were older animals (above 12 months) (OR = 5.3; 95% CI 1.7-16.6), semi-intensive farms (OR = 2.2; 95% CI 1.3-6.2), the presence of either dogs or cats (OR = 3.6; 95% CI 1.1-12.3), a large herd size (>100 animals) (OR = 3.7; 95% CI 1.4-10.0), and a single source of replacement animals (OR = 3.9; 95% CI 1.6-9.6). These findings are vital in developing effective control measures against these parasites in ruminant farms in Selangor, Malaysia. More national epidemiological research is required to elucidate the spatial distribution of these infections and their potential impact on Malaysia's livestock industry.

Seroprevalence and risk factors analysis of Neospora caninum and Toxoplasma gondii in cattle of Beheira, Egypt

Introduction

Neospora caninum and Toxoplasma gondii are closely related obligate intracellular protozoan parasites. They are considered to be the major causes of infectious abortions and congenital abnormalities in livestock worldwide resulting in huge economic losses. Currently, there are no reports on the prevalence of neosporosis or toxoplasmosis in cattle in Beheira, Egypt's most important region for cattle industry.

Methods

The current study investigated the presence of anti-N. caninum and anti-T. gondii antibodies in apparent healthy cattle from eight localities representing the whole area of Beheira. A total of 358 plasma samples were randomly collected from 6 dairy and 10 beef farms and analyzed by commercially available ELISAs. Production type (dairy versus beef), sex (female vs male), age (< 3 years, 3-5, and > 5 years old), breed (mixed vs Holstein vs Colombian Zebu), and location (various locations) were assessed as risk factors for N. caninum and T. gondii infections.

Results and discussion

Of the samples, 88 (24.6%) and 19 (5.3%) were positive for anti-N. caninum and anti-T. gondii antibodies, respectively, and mixed infection was detected in 7. Of the 16 herds, 6 dairy and 7 beef herds were positive for antibodies to N. caninum. Antibodies to T. gondii were detected in 4, and 5 of dairy and beef herds, respectively. Production type (dairy) and, therewith, sex (female), age (aged over 5 years), and location were considered as risk factors for N. caninum infection. No factors statistically associated with T. gondii infection were identified. Overall, this study provided the first serological detection of N. caninum and T. gondii infections in cattle from Beheira, demonstrating the endemicity of both parasites in the main cattle rearing region of Egypt. This study also confirmed earlier reports of N. caninum being more present in dairy cattle than in beef cattle. Routine monitoring of N. caninum and T. gondii infections and the implementation of control strategies are urgently needed.

Congenital transmission of Neospora caninum in wild ungulates and foxes

Introduction

Neospora caninum is one of the main causes of abortion in cattle. In wildlife, the occurrence and relevance of vertical infection have not been yet clearly evaluated. The aim of this study was to verify the possibility of vertical transmission of N. caninum in three wild species extensively distributed in Europe, namely roe deer Capreolus capreolus, wild boar Sus scrofa and red fox Vulpes vulpes.

Methods

A total of 190 fetuses (72 wild boars, 67 foxes and 51 roe deer) from 61 females were included in the study. All animals, which were either found dead or culled within selective control plans in North-western Italy, were tested, in parallel by PCR on central nervous system, skeletal muscle and kidney.

Results and discussion

The efficiency of vertical transmission in the three target species was of 87.5% (95% CI 69.00-95.66).

Temporal transcriptomic changes in microRNAs involved in the host immune response and metabolism during Neospora caninum infection

BACKGROUND

Neospora caninum infection is a major cause of abortion in cattle, which results in serious economic losses to the cattle industry. However, there are no effective drugs or vaccines for the control of N. caninum infections. There is increasing evidence that microRNAs (miRNAs) are involved in many physiological and pathological processes, and dysregulated expression of host miRNAs and the biological implications of this have been reported for infections by various protozoan parasites. However, to our knowledge, there is presently no published information on host miRNA expression during N. caninum infection.

METHODS

The expression profiles of miRNAs were investigated by RNA sequencing (RNA-seq) in caprine endometrial epithelial cells (EECs) infected with N. caninum at 24 h post infection (pi) and 48 hpi, and the functions of differentially expressed (DE) miRNAs were predicted by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. The transcriptome data were validated by using quantitative real-time polymerase chain reaction. One of the upregulated DEmiRNAs, namely chi-miR-146a, was selected to study the effect of DEmiRNAs on the propagation of N. caninum tachyzoites in caprine EECs.

RESULTS

RNA-seq showed 18 (17 up- and one downregulated) and 79 (54 up- and 25 downregulated) DEmiRNAs at 24 hpi and 48 hpi, respectively. Quantitative real-time polymerase chain reaction analysis of 13 randomly selected DEmiRNAs (10 up- and three downregulated miRNAs) confirmed the validity of the RNA-seq data. A total of 7835 messenger RNAs were predicted to be potential targets for 66 DEmiRNAs, and GO and KEGG enrichment analysis of these predicted targets revealed that DEmiRNAs altered by N. caninum infection may be involved in host immune responses (e.g. Fc gamma R-mediated phagocytosis, Toll-like receptor signaling pathway, tumor necrosis factor signaling pathway, transforming growth factor-β signaling pathway, mitogen-activated protein kinase signaling pathway) and metabolic pathways (e.g. lysine degradation, insulin signaling pathway, AMP-activated protein kinase signaling pathway, Rap1 signaling pathway, calcium signaling pathway). Upregulated chi-miR-146a was found to promote N. caninum propagation in caprine EECs.

CONCLUSIONS

This is, to our knowledge, the first report on the expression profiles of host miRNAs during infection with N. caninum, and shows that chi-miR-146a may promote N. caninum propagation in host cells. The novel findings of the present study should help to elucidate the interactions between host cells and N. caninum.

Immunization with a Multivalent Listeria monocytogenes Vaccine Leads to a Strong Reduction in Vertical Transmission and Cerebral Parasite Burden in Pregnant and Non-Pregnant Mice Infected with Neospora caninum

Neospora caninum is an apicomplexan parasite that causes abortion and stillbirth in cattle. We employed the pregnant neosporosis mouse model to investigate the efficacy of a modified version of the attenuated Listeria monocytogenes vaccine vector Lm3Dx_NcSAG1, which expresses the major N. caninum surface antigen SAG1. Multivalent vaccines were generated by the insertion of gra7 and/or rop2 genes into Lm3Dx_NcSAG1, resulting in the double mutants, Lm3Dx_NcSAG1_NcGRA7 and Lm3Dx_NcSAG1_NcROP2, and the triple mutant, Lm3Dx_NcSAG1_NcGRA7_NcROP2. Six experimental groups of female BALB/c mice were inoculated intramuscularly three times at two-week intervals with 1 × 10⁷ CFU of the respective vaccine strains. Seven days post-mating, mice were challenged by the subcutaneous injection of 1 × 10⁵N. caninum NcSpain-7 tachyzoites. Non-pregnant mice, dams and their offspring were observed daily until day 25 post-partum. Immunization with Lm3Dx_NcSAG1 and Lm3Dx_NcSAG1_NcGRA7_NcROP2 resulted in 70% postnatal pup survival, whereas only 50% and 58% of pups survived in the double mutant-vaccinated groups. Almost all pups had died at the end of the experiment in the infection control. The triple mutant was the most promising vaccine candidate, providing the highest rate of protection against vertical transmission (65%) and CNS infection. Overall, integrating multiple antigens into Lm3Dx_SAG1 resulted in lower vertical transmission and enhanced protection against cerebral infection in dams and in non-pregnant mice.

Immunoproteomics to identify species-specific antigens in Neospora caninum recognised by infected bovine sera

Bovine neosporosis is a disease of concern due to its global distribution and significant economic impact through massive losses in the dairy and meat industries. To date, there is no effective chemotherapeutic drug or vaccine to prevent neosporosis. Control of this disease is therefore dependent on efficient detection tests that may affect treatment management strategies. This study was conducted to identify the specific immunoreactive proteins of Neospora caninum tachyzoites recognised by sera from cattle infected with N. caninum, Toxoplasma gondii, Cryptosporidium parvum, Babesia bovis and B. bigemina, and by sera from uninfected cattle using two-DE dimensional gel electrophoresis (2-DE) combined with immunoblot and mass spectrometry (LC-MS/MS). Among 70 protein spots that reacted with all infected sera, 20 specific antigenic spots corresponding to 14 different antigenic proteins were recognised by N. caninum-positive sera. Of these immunoreactive antigens, proteins involved in cell proliferation and invasion process were highly immunogenic, including HSP90-like protein, putative microneme 4 (MIC4), actin, elongation factor 1-alpha and armadillo/beta-catenin-like repeat-containing protein. Interestingly, we discovered an unnamed protein product, rhoptry protein (ROP1), possessing strong immunoreactivity against N. caninum but with no data on function available. Moreover, we identified cross-reactive antigens among these apicomplexan parasites, especially N. caninum, T. gondii and C. parvum. Neospora caninum-specific immunodominant proteins were identified for immunodiagnosis and vaccine development. The cross-reactive antigens could be evaluated as potential common vaccine candidates or drug targets to control the diseases caused by these apicomplexan protozoan parasites.

Evaluation of knowledge, attitudes and practices regarding neosporosis and toxoplasmosis among farmers and animal health practitioners in Namibia

This study assessed the knowledge, attitudes and practices of livestock farmers in Namibia's Khomas region and animal health practitioners (veterinarians and animal health technicians) in the whole country concerning neosporosis and toxoplasmosis. Structured questionnaires were used, and a total of 63 farmers and 51 animal health practitioners responded out of an estimated 560 farmers in the Khomas region and 300 veterinarians and veterinary technicians in the country. Only 15.9% of the livestock farmers (n = 63) had heard about neosporosis or toxoplasmosis or knew how animals get infected (p < 0.0001). Only 5% of the farmers knew the risks associated with keeping dogs and cats concerning neosporosis and toxoplasmosis, respectively (p < 0.0001). None of the 51 animal health practitioners routinely requested Neospora caninum or Toxoplasma gondii laboratory tests in cases of cattle, sheep or goat abortions. Although all animal health practitioners indicated they routinely interacted with livestock farmers, none regularly discussed neosporosis or toxoplasmosis. Only 3.9% of animal health practitioners (n = 51) indicated that they had ever discussed either neosporosis or toxoplasmosis at a farmers' gathering (p < 0.0001), and only 21.6% had talked to at least one cat owner about toxoplasmosis in the previous 12 months (p < 0.0001). The authors concluded that farmers in the Khomas region were generally unaware of neosporosis and toxoplasmosis but could change their attitudes and practices if educated. The animal health practitioners lacked a deeper understanding and appreciation of the two diseases, which is required to cultivate enough confidence to educate farmers. Sharing this research and other relevant information on the two diseases at farmers' meetings, veterinary congresses, journals and newsletters could help educate farmers and animal health practitioners. Such platforms are likely to succeed because both these groups use these forums to get new information.

Recombinant actin-depolymerizing factor of the apicomplexan Neospora caninum (NcADF) is susceptible to oxidation

Neospora caninum is a member of Apicomplexa Phylum and the causative agent of neosporosis, a disease responsible for abortions in cattle. Apicomplexan parasites have a limited set of actin-binding proteins conducting the regulation of the dynamics of nonconventional actin. The parasite actin-based motility is implicated in the parasite invasion process in the host cell. Once no commercial strategy for the neosporosis control is available, the interference in the parasite actin function may result in novel drug targets. Actin-depolymerization factor (ADF) is a member of the ADF/cofilin family, primarily known for its function in actin severing and depolymerization. ADF/cofilins are versatile proteins modulated by different mechanisms, including reduction and oxidation. In apicomplexan parasites, the mechanisms involved in the modulation of ADF function are barely explored and the effects of oxidation in the protein are unknown so far. In this study, we used the oxidants N-chlorotaurine (NCT) and H₂O₂ to investigate the susceptibility of the recombinant N. caninum ADF (NcADF) to oxidation. After exposing the protein to either NCT or H₂O₂, the dimerization status and cysteine residue oxidation were determined. Also, the interference of NcADF oxidation in the interaction with actin was assessed. The treatment of the recombinant protein with oxidants reversibly induced the production of dimers, indicating that disulfide bonds between NcADF cysteine residues were formed. In addition, the exposure of NcADF to NCT resulted in more efficient oxidation of the cysteine residues compared to H₂O₂. Finally, the oxidation of NcADF by NCT reduced the ability of actin-binding and altered the function of NcADF in actin polymerization. Altogether, our results clearly show that recombinant NcADF is sensitive to redox conditions, indicating that the function of this protein in cellular processes involving actin dynamics may be modulated by oxidation.

Seroprevalence of Neospora caninum infection and associated risk factors in cattle in Shanxi Province, north China

Neospora caninum is an obligate intracellular parasitic protozoan that can cause abortions in cattle and pose considerable economic losses to the cattle industry. As a major livestock province, little is known of N. caninum infection in cattle in Shanxi Province, north China. In order to investigate the seroprevalence of N. caninum in cattle in Shanxi Province, 978 cattle serum samples were collected from 11 cities in three representative geographical locations in Shanxi Province, and the N. caninum-specific IgG antibodies were examined using an indirect enzyme linked immunosorbent assay (ELISA) kit commercially available. The results showed that 133 of the 978 examined cattle serum samples (13.60%, 95% CI = 11.45-15.75) were positive for N. caninum antibodies, and the seroprevalence in different cities ranged from 0 to 78.89%. The geographical location and management mode were the risk factors associated with N. caninum infection in cattle herds in Shanxi Province. Cattle in Northern and Central Shanxi Province as well as cattle whose management mode is that of large-scale cattle farming companies are more susceptible to N. caninum infection. This was the first large-scale survey of N. caninum seroprevalence and assessment of associated risk factors in cattle in Shanxi Province, which provided baseline information for the prevention and control of N. caninum infection in cattle in Shanxi Province, north China.

Investigation of the outbreaks of abortions and orchitis in livestock in Namibia during 2016-2018

This study investigated outbreaks of seemingly related abortions and orchitis which occurred in the Khomas, Omaheke and Otjozondjupa regions of Namibia from 2016 to 2018, affecting cattle, sheep and goats. Fifty-nine questionnaires were administered, and 48 were completed giving an 81.4% return. The outbreaks were limited to Namibia's east and central regions, mainly on farms rearing cattle, sheep and goats and on farms with a mixture of these species. There was no significant difference between Khomas and other regions on abortion reporting at the farm level [X2 (1, N = 48) = 0.0002, p = 0.987851]. However, there was a significant difference in the abortions at the animal level among the three regions [X2 (2, N = 6246) = 239.8339, p = .00001]. In addition, the proportions of abortions calculated at the animal level at each farm were significantly different when the Khomas region was compared to the other regions. Seventeen cattle sera, 35 sheep sera, 52 caprine sera, 18 bovine liver samples, one caprine liver, five aborted cattle foetuses, two cattle placentas, 18 testes (one bull, eight bucks and nine rams) and ten bull sheath scrapings were collected and tested. Histopathology, microbiology, serology, immunohistochemistry, real-time PCR and mineral analytical techniques were used to establish the aetiology of the abortion and orchitis outbreaks. The gross and histopathological findings on the 18 testicles were characteristic of chronic orchitis. In aborted foetuses, significant histopathological findings included meconium aspiration, funisitis and cardiomyopathy. Placentitis and endometritis were the primary pathologies observed in cows. The bacteria isolated from microbiological samples included Enterococcus spp. (65.5% [19/29]), Enterobacter spp. (6.9% [2/29]) and Streptococcus spp. (10.3% [3/29]), Trueperella pyogenes (3.4% [1/29]), Stenotrophomonas maltophilia (3.4% [1/29]), Staphylococcus epidermidis (3.4% [1/29]), Providencia rettgeri (3.4% [1/29]) and Acinetobacter lwoffii (3.4% [1/29]), mostly opportunistic bacteria. On mineral analysis, 28%, 33%, 83%, 33% and 17% (n = 18) of cattle livers were low in copper, zinc, manganese, selenium and iron, respectively. Twenty-three percent (12/52) of the caprine sera were positive for Brucella melitensis on the Rose Bengal and complement fixation tests. Thirty-five ovine sera were tested for B. melitensis, B. ovis and Coxiella burnetii, and the prevalence for each was 2.9% (1/35). PCR tests on foetuses were all negative for Brucella spp., Coxiella burnetii, Chlamydia spp., Listeria monocytogenes, Salmonella spp., Campylobacter fetus spp., Leptospira pathogenic strains, bovine viral diarrhoea virus, Rift Valley fever virus, Anaplasma phagocytophilum and bovine herpes virus 4 Campylobacter fetus spp. and Trichomonas foetus spp. The authors concluded that Brucella spp., Enterococcus spp., Escherichia coli, Streptococcus spp., Trueperella pyogenes and Coxiella burnetii could have contributed to this outbreak. Micronutrient imbalances and pathogenic abiotic nanoparticles were also identified as possible contributors to the abortion outbreaks.

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.

Role of TLR2/MyD88 in the production of specific IgM and IgG antibodies during the immunization of mice against Neospora caninum

Neospora caninum is a parasite relevant to the veterinary field. Innate and adaptive responses against N. caninum induce effector mechanisms that limit parasite replication, but little is known about their role in humoral response. Our work aimed to verify whether key molecules in the TLR2/MyD88-mediated response would impact the production of specific IgM and IgG antibodies in mice during immunization with soluble antigens of N. caninum. We observed that lack of IFN-gamma did not negatively affect the production of specific antibodies. However, mice genetically deficient in Toll-like receptor 2, Myeloid differentiation factor 88, Interleukin 12 and inducible nitric oxide synthase presented significant decrease in antibody levels against N. caninum antigens, which also reflected in the diversity of the antigen recognized by their serum. In that sense, we show here that molecules within this innate recognition pathway may present a direct impact in the induction of an antibody response against N. caninum.

Extracellular H2O2, peroxiredoxin, and glutathione reductase alter Neospora caninum invasion and proliferation in Vero cells

Neospora caninum is a protozoan member of the Apicomplexa phylum and is closely connected with abortion in cattle. The development of the parasite in host cells is characterized by the active secretion of proteins, allied to the tight control of the redox status. In this sense, elucidating the mechanisms related to the role of the redox agents and enzymes during the invasion and proliferation of N. caninum may contribute to developing novel forms of neosporosis control. In this study we verified the effects of the recombinant forms of N. caninum glutathione reductase (rNcGR) and thioredoxin-dependent peroxide reductase (rNcPrx), as well as H₂O₂ in the tachyzoite invasion and proliferation. rNcPrx interfered in the N. caninum invasion in a redox state manner. Oxidized rNcPrx inhibited the N. caninum invasion and proliferation with no toxic effects observed in Vero cells. In contrast, lower concentrations of H₂O₂ (10 μM) stimulated the N. caninum invasion, which was reverted in higher doses (>100 μM). H₂O₂ inhibited the parasite proliferation in lower concentrations than cytotoxicity in host cells, resulting in a positive selectivity index (1.8). Besides, rNcPrx (reduced and non-reduced) and rNcGR inhibited the parasite proliferation without affecting the host cell. Our results indicate the connection between the N. caninum development and the redox state, contributing to the elucidation of parasite propagation and control mechanisms.