Seroepidemiological study of Neospora caninum in beef and dairy cattle in La Pampa, Argentina

A first insight into seropositivity of Neospora caninum and associated risk factors in free-roaming dogs from Ecuador

Neosporosis is a worldwide parasitic disease caused by the protozoan Neospora caninum. It can cause economic losses to farmers due to its relationship with abortions and neonatal mortality in cows. Dogs play a key role in its spread as they are considered definitive hosts. In this study, we determined for the first time the seropositivity of N. caninum infection in dogs from Ecuador and evaluated potential risk factors. A total number of 339 free-roaming dogs from the three main regions of Ecuador (Coastal, Andean, and Amazonian regions) were included in the study and classified either as urban or rural dogs. Serum samples were collected from November 2018 to May 2019, and analyzed with a commercial ELISA test. An overall seropositivity of 6.8 % (CI: 95 %, 2.8 % - 11.7 %) was found in N. caninum infection with no statistical differences among regions or urban/rural dogs. This is the first surveillance of N. caninum in Ecuador, confirming a country-wide distribution of this pathogen. Considering the large populations of free-roaming dogs in Ecuador, a One Health approach for surveillance and managing N. caninum in dogs is needed to protect either livestock or wildlife.

Neosporosis in Argentina: Past, present and future perspectives

Neosporosis, caused by the protozoan Neospora caninum, was first diagnosed in Argentinean cattle in the 90's. With a national bovine stock of approximately 53 million head, the cattle industry is socially and economically relevant. Severe economic losses have been estimated at US$ 33 and 12 million annually in dairy and beef cattle, respectively. Approximately 9% of bovine abortions in the Buenos Aires province are caused by N. caninum. In 2001, the first isolation of N. caninum oocysts from feces of a naturally infected dog was performed in Argentina and named as NC-6 Argentina. Further strains were isolated from cattle (NC-Argentina LP1, NC-Argentina LP2) and axis deer (Axis axis, NC-Axis). Epidemiological studies revealed a high distribution of Neospora-infections not only in dairy but also in beef cattle, with seroprevalence rates of 16.6-88.8% and 0-73%, respectively. Several experimental infection studies in cattle have been carried out, as well as attempts to develop effective vaccines to avoid Neospora-abortions and transmission. However, no vaccine has proven successful for its use in daily practice. Reduction of seroprevalence, vertical transmission and Neospora-related abortions have been achieved in dairy farms by the use of selective breeding strategies and embryo transfer. Neospora-infections have been also detected in goats, sheep, deer, water buffaloes (Bubalus bubalis) and gray foxes (Lycalopex griseus). Moreover, Neospora-related reproductive losses were reported in small ruminants and deer species and could be more frequent than previously thought. Even though diagnostic methods have been improved during the last decades, control of neosporosis is still not optimal. The development of new strategies including new antiprotozoal drugs and vaccines is highly needed. This paper reviews the information from the previous 28 years of research of N. caninum in Argentina, including seroprevalence and epidemiological studies, available diagnostic techniques, experimental reproduction, immunization strategies, isolations and control measures in domestic and non-domestic animals from Argentina.

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.

Neospora caninum Infection in Cattle in the Province of Kohgiluyeh and Boyer Ahmad, Southwest of Iran: Seroprevalence and Molecular Assessment

Introduction

Among the protozoa of veterinary importance, Neospora caninum is responsible for large economic and productive losses in cattle herds. Dogs are being considered the definitive hosts of the parasite. Neospora caninum has gained considerable attention through its role in the etiology of bovine abortion. The current study aimed at assessing the status of Neospora infection in cattle in Boyer-Ahmad County in Kohgiluyeh and Boyer-Ahmad province, southwest of Iran.

Methods

In this cross-sectional study, 150 cattle blood samples were collected and samples were screened for N. caninum antibodies using a modified direct agglutination test (MAT). For the same samples, 130 buffy coats were collected and tested, by PCR, for the presence of N. caninum DNA, targeting the Nc-5 gene.

Results

Anti-N. caninum antibodies were detected in the sera of 49 out of 150 cattle which is corresponding to a seroprevalence rate of 32.7%. Neospora DNA was detected in buffy coats of 26 out of 127 (20.47%) cattle. Even though Neospora infection was more common in females and in five-year-old cattle by serology and molecular methods, yet there was no statistically significant difference between age, sex, and Neospora infection in both molecular and serological methods (p > 0.05).

Conclusion

Findings of the current study indicate a high rate of N. caninum infection in cattle of Boyer-Ahmad region in the southwest of Iran. This issue should be further investigated and the prevention and control of this parasite in livestock, due to the high financial burden of this parasite in the livestock industry, should be considered.

Seroprevalence of Seven Reproductive Diseases in Beef and Dairy Cows from Three Provinces in Indonesia

Bovine reproductive diseases are endemic in Indonesia, but comprehensive information about their infectious causes is not available. Therefore, our aim for this study was to detect several infectious agents that cause reproductive diseases in Indonesian beef and dairy cows. A total of 152 cow serum samples collected by Faculty of Veterinary Medicine of Brawijaya University and Veterinary Disease Investigation Centre as a part of the mandatory and regularly surveillance system from three provinces during 2019–2020 were used. The samples were then sent to Indonesian Research Centre for Veterinary Science (IRCVS) for further detection of seven reproductive diseases by enzyme-linked immunosorbent assay (ELISA). Seven reproductive diseases to be tested in parallel are neosporosis, chlamydiosis, brucellosis, Q fever, bovine viral diarrhea (BVD), infectious bovine rhinotracheitis (IBR), and BHV-4 infection. The dominant reproductive diseases in Indonesian cows were BVD (45.69%), chlamydiosis (31.58%), IBR (20.53%), neosporosis (11.84%), and BHV-4 infection (10.53%). The seroprevalence of IBR, BHV-4 infection, neosporosis, and brucellosis varied significantly (P < 0.05) between dairy and beef cattle. The most dominant reproductive diseases in aborted cows were chlamydiosis (45%), BVD (41%), and neosporosis (10%). The conclusion drawn from this study is that the dominant reproductive diseases in Indonesian cows are BVD, chlamydiosis, IBR, neosporosis, and BHV-4 infection. Chlamydiosis, BVD, and neosporosis are common among aborted cow. Chlamydiosis, neosporosis, and BHV-4 infection should be included in the national priority list in Indonesia. Control and preventive measures should be focused on high-risk areas and animals like stray cat and dog.

Seroprevalence of Neospora caninum infection in cattle from Pereira, Colombia ⋆

There are over 25.6 million cattle heads in Colombia being the fourth-highest herd in Latin America. This study aimed to describe the seroprevalence of Neospora caninum in cattle from 25 rural farms at Pereira municipality, Risaralda Department, which has a total bovine population of 43,508 animals. A cross-sectional observational study was performed in beef and dairy herds during 2017-2018. A total of 325 animals in 25 herds, with 13 animals per herd, were sampled. A commercial competitive ELISA (cELISA) kit was used to detect N. caninum antibodies. Associated risk factors were analyzed in two different levels: individual animals and herds. For all the independent variables, chi-square (χ²) and Fisher tests were used to assess associations and significance. The overall estimated seropositivity was 20.6% (95%CI 16.2%-25.0%). The seroprevalence by herds was 92.0% ranging from 0.0% to 46.2%. Noteworthy, beef herds had significantly (p = 0.0107) higher seropositivity (50% of them above 35% of seropositivity) compared with those for milk purposes (4.8%) (OR = 20.0; 95%CI 1.2-331.0). Other risk factors were not significantly (p ≥ 0.05) associated with N. caninum seropositivity. Bovine neosporosis may be associated with abortions in both beef and dairy Colombian farms. More studies about the epidemiology, associated factors and consequences, as well as on tools for better diagnosis of bovine abortion, including histopathology and other ancillary tests, should be performed.

[Seroprevalence and risk factors associated with Neospora caninum in dairy farms from the Province of Salta, Argentina]

The objective of this work was to determine the seroprevalence of Neospora caninum in cattle in Valle de Lerma, province of Salta, Argentina, and the risk factors associated with the disease. Serum samples were taken from 40 cows in each dairy herd, which were analyzed by indirect ELISA to detect antibodies against N. caninum. Chronic and acute infections were discriminated by measuring the avidity of these antibodies. All the herds exhibited at least one seropositive animal, the mean being 35.3 ± 14.9% of positive animals. Specific antibodies were also detected in dogs present in 9of the herds, which showed a seropositivity value of 71.7% ± 19.9%. Among the seropositive animals, 56.3% showed acute infections. A negative association was found between seroprevalence and the avidity index of specific antibodies, indicating that the presence of animals with acute infections is associated with higher seroprevalence. Fields with grazing showed more recent infections. These results show for the first time the importance of this parasite in this particular region and the need to promote the development of control programs considering the different risk factors that affect the epidemiological situation of the disease.

Isolation of Neospora caninum from a beef cattle fetus from Argentina: Immunopathological and molecular studies

Neospora caninum is an important abortifacient agent affecting mainly cattle worldwide. The aim of the present work was to describe the histopathological findings in a naturally infected beef cow and its midterm fetus caused by a genetically defined N. caninum isolate in Argentina. A N. caninum seropositive multiparous Aberdeen Angus pregnant cow and its fetus in the sixth month of gestation were submitted for histopathological, immunohistochemical, serological, and molecular studies and parasite isolation. The cow belonged to a beef herd under extensive management, with a N. caninum seroprevalence of 11%, and low level of annual abortion rate (≤ 5%). The dam had mild lymphocytic infiltrate in CNS, heart and uterus and no parasites were detected by Immunohistochemistry (IHC). No parasitic DNA was detected in the dam's brain, and gamma interferon knockout mice inoculated with brain material did not become infected. Clusters of tachyzoites and parasitic DNA were detected in the placenta by IHC and PCR, respectively. However, isolation from the placenta was unsuccessful. The fetus developed specific antibodies and an inflammatory response was detected in multiple organs. Furthermore, in vitro and in vivo isolation was achieved from gamma interferon knockout mice inoculated with CNS from the fetus. Multilocus-microsatellite typing revealed a genetically defined N. caninum isolate similar to the previously reported as MLG 72. We report the first N. caninum isolate from beef cattle in Argentina.

Evaluation of a competitive inhibition ELISA based on the recombinant protein tSAG1 to detect anti-Neospora caninum antibodies in cattle

Neospora caninum is a protozoan parasite that causes abortion and important economic losses in cattle worldwide. There are no treatments or vaccines available; disease control is based on diagnosis and herd management strategies. We developed, validated, and evaluated under field conditions a competitive inhibition ELISA based on the truncated SAG1 protein (tSAG1), expressed in Escherichia coli, and the RafNeo5 monoclonal antibody (ciELISA_tSAG1). A criterion based on the 3-y sequential serologic analysis of 230 dairy cows by IFAT was used as the gold standard. The assay was validated using 860 serum samples from cows that were consistently positive or negative by IFAT throughout the study period. ciELISA_tSAG1 was then used to evaluate the prevalence of neosporosis in 16 beef cow herds (22 samples per herd, 352 total samples). The results were compared with those from IFAT and a commercial cELISA (cELISA_VMRD). The ciELISA_tSAG1 cutoff was ≥ 29%I, with a diagnostic sensitivity of 98.7% (95% CI = 96.8-99.7%) and a diagnostic specificity of 97.9% (95% CI = 96.4-99.0%). Concordance among IFAT, cELISA_VMRD, and ciELISA_tSAG1 was 90.3%. The agreement (κ) between ciELISA_tSAG1 and the other 2 tests was ≥ 0.81. The overall prevalence of neosporosis in the 16 beef herds was 30% (range: 5-60%). The ciELISA_tSAG1 could be useful for large-scale detection of anti-N. caninum antibodies in cattle and seroepidemiologic investigations, given its appropriate sensitivity and specificity, and the simplicity of production.

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.

Seroprevalence of anti-Neospora caninum antibodies in cows of North-Eastern Algeria

AIM

The present cross-sectional study aimed at assessing the seroprevalence of Neospora caninum infection both at herd and within herd and at determining risk factors that are associated with its seropositivity.

MATERIALS AND METHODS

A total of 90 cows distributed over seven herds located in two North-Eastern Algerian provinces were blood sampled in order to be tested for the presence of antibodies against N. caninum using a commercially available enzyme-linked immunosorbent assay kit.

RESULTS

The individual seroprevalence of N. caninum was found to be 12.22%, and six of the seven herds tested had at least one seropositive cow. The logistic regression model revealed that abortion (odds ratio [OR]=29.15) and parity (OR=7.38) were positively associated with the seropositivity of animals on an individual basis.

CONCLUSION

The study confirms the existence of N. caninum infection in cattle in North-Eastern Algeria. However, a widespread infection rate of 85.71% and its significant statistical association with previous abortion (OR=29.15) need further investigations.

Using beef-breed semen in seropositive dams for the control of bovine neosporosis

A program for controlling bovine neosporosis based only on the use of beef semen, without culling seropositive animals, was evaluated in a closed dairy cattle herd over a 5-year period (2013-2017). The program was based on individual and periodic serological screenings to identify seropositive breeders. Seropositive cows were inseminated with beef-breed semen, thus excluding their descendants from the remount in order to prevent the vertical transmission of the disease. Seronegative animals, as well as heifers at first insemination, were tested before each insemination. Sera of 1097 cattle were examined by a commercial indirect ELISA for the detection of antibodies anti-Neospora caninum. To verify the difference in seropositivity values among years of sampling, statistical analysis through generalized estimation equations (GEEs) was performed, also considering the effects of age, lineages, and occurrence of abortion. A seroprevalence of 33.8% was found in the first screening. The prevalence and incidence of the infection within the herd decreased significantly in 2017 (P = 28.9%, I = 1.4%) (p-value = 0.0001). The family line investigation detected a higher risk of being seropositive for a cow born to a seropositive dam (p-value = 0.0001) than to a seronegative dam, decreasing both the apparently vertical and horizontal transmissions. The number of spontaneous abortions decreased after the first year of the study (23 in 2013 to 6 in 2017). Seropositive animals were associated with abortion events (p-value = 0.0001). Although an eradication of N. caninum was not achieved at the end of the study period, a significant reduction in prevalence and incidence of neosporosis in the herd and a reduction of the abortion rate was achieved with the application of this control plan in five years, without culling a high number of seropositive potential milk-producing animals.

[Detection of Chlamydia abortus in bovine reproductive losses in the province of La Pampa, Argentina]

Reproductive losses linked to an infectious etiology in bovine cattle are a major economic concern worldwide. In Argentina, more than 50% of abortion cases have unknown causes. Species belonging to Chlamydiaceae family are frequent etiologic agents of abortion around the world; however, there is yet no information on their prevalence in Argentina. The objective of this work was to identify Chlamydia spp., and particularly C. abortus in reproductive losses from bovine cattle in La Pampa, Argentina. Real time PCR targeting Chlamydiaceae-specific DNA fragments was performed on 251 samples obtained from bovine abortions and stillborns, and ArrayTube was used for species identification on positive samples. Chlamydiaceae DNA was detected in 12 samples of aborted fetuses (4.78%), 83.33% (10/12) accounting for abortions and 16.66% (2/12) for stillborns. C. abortus was detected by ArrayTube in 5 cases (1.99% of all samples, and 41.67% of Chlamydiaceae positive samples). This study shows the first detection of Chlamydiaceae and C. abortus DNA on reproductive losses of bovine cattle in Argentina, and the described prevalence value (4.78%) should be taken as baseline value due to the type of samples analyzed. Detection of genetic material from Chlamydiaceae not matching any of the studied species could be due to intraspecies variants or local species not yet described. Further research on Chlamydia infections in bovine cattle in Argentina is imperative to describe their range, to analyze their economic and zoonotic implications and to make recommendations about prevention and control measures.

An Ibero-American inter-laboratory trial to evaluate serological tests for the detection of anti-Neospora caninum antibodies in cattle

We carried out an inter-laboratory trial to compare the serological tests commonly used for the detection of specific Neospora caninum antibodies in cattle in Ibero-American countries. A total of eight laboratories participated from the following countries: Argentina (n = 4), Brazil (n = 1), Peru (n = 1), Mexico (n = 1), and Spain (n = 1). A blind panel of well-characterized cattle sera (n = 143) and sera representative of the target population (n = 351) was tested by seven in-house indirect fluorescent antibody tests (IFATs 1-7) and three enzyme-linked immunosorbent assays (ELISAs 1-3; two in-house and one commercial). Diagnostic performance of the serological tests was calculated and compared according to the following criteria: (1) the "Pre-test information," which uses previous epidemiological and serological data; (2) the "Majority of tests," which classifies a serum as positive or negative according to the results obtained by most tests evaluated. Unexpectedly, six tests showed either sensitivity (Se) or specificity (Sp) values lower than 90%. In contrast, the best tests in terms of Se, Sp, and area under the ROC curve (AUC) values were IFAT 1 and optimized ELISA 1 and ELISA 2. We evaluated a high number of IFATs, which are the most widely used tests in Ibero-America. The significant discordances observed among the tests regardless of the criteria employed hinder control programs and urge the use of a common test or with similar performances to either the optimized IFAT 1 and ELISAs 1 and 2.

Canine neosporosis: perspectives on pathogenesis and management

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