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PubMed1998

Determination of the association between Neospora caninum infection and reproductive performance in beef herds.

OBJECTIVE: To determine seroprevalence of Neospora caninum infection in beef herds and the association between serologic status and rate of abortion, stillbirth, calf mortality, and reproductive failure. DESIGN: Longitudinal study. ANIMALS: 419 cows from 8 beef herds in central Alberta. PROCEDURE: 1,391 serum samples from a serum bank were analyzed, using ELISA, and results were compared, using logistic regression, with productivity data on individual cows obtained from a database established during a 4-year period. RESULTS: 30% of cows were seropositive at some point during the 4-year period. Risks of abortion (odds ratio [OR], 5.7) and stillbirth (OR, 2.8) in seropositive cows were significantly greater than in seronegative cows. Risks of being culled for any reason (OR, 1.9) or for reproductive failure (OR, 2.5) in seropositive cows were also significantly greater than in seronegative cows. Changes in titer with time in individual cows and a lack of association between serologic status of dam versus daughter suggest that postnatal transmission was possible in these herds. However, horizontal transmission did not appear to play a substantial role in abortions that occurred in these herds. CLINICAL IMPLICATIONS: Neosporosis should be investigated as a potential source of economic loss to the beef industry.

Abortion, Veterinary↗
PubMed1998

Seroepidemiologic study of Neospora caninum in dairy herds.

OBJECTIVE: To identify risk factors associated with Neospora caninum infection in dairy herds in Québec and to estimate seroprevalence in case and control herds. DESIGN: Herd-based case-control and seroprevalence study. ANIMALS: 3,059 cows from 24 case and 22 control dairy herds in Québec. PROCEDURE: Blood samples were obtained from each cow, and sera were tested, using an ELISA, for antibodies to N caninum. Owners of herds answered questionnaires requesting information on demographics and herd management practices. Seroprevalence was compared between case and control herds, using the Mann-Whitney test. Risk factors were compared between case and control herds, using logistic regression. RESULTS: All case herds and 73% of control herds had at least one seropositive cow. Median seroprevalence was significantly greater among case herds (22.5%) than among control herds (7.5%). Dogs were found most often and in greatest numbers on farms housing case herds compared with control herds during the past 3 years. CLINICAL IMPLICATIONS: Although the exact role that dogs have in transmission of N caninum in dairy herds needs to be elucidated, dogs should have limited access to barns and cattle.

Animal Husbandry↗
PubMed1992

Characterization of anti-Neospora caninum hyperimmune rabbit serum by western blot analysis and immunoelectron microscopy.

The antigens recognized by hyperimmune rabbit serum raised against tachyzoites of the NC-1 isolate of Neospora caninum were characterized using chemiluminescent Western blotting, immunogold-silver staining and immunoelectron microscopy. Approximately 20 immunodominant antigens whose relative rates of migration were 16-80 kDa were recognized by the serum in Western blots using reduced or nonreduced parasite antigen preparations. The nonreduced parasite antigens were more strongly recognized by the serum than were the reduced antigen preparations. Immunoelectron microscopy revealed that the rabbit-serum-labeled antigens were localized to some organelles of N. caninum tachyzoites and to the parasitophorous vacuole surrounding them. In particular, antigens found in the dense granules, in the micronemes, and in the posterior portion of the rhoptries were strongly labeled by an indirect immunogold-labeling technique.

Animals↗
PubMed1989

Encephalomyelitis and myositis in a boxer puppy due to a Neospora-like infection.

A 10-week-old Boxer dog from Uppsala, Sweden, was killed because of hind limb paralysis. The hind limb muscles were grossly atrophied and encephalomyelitis and myositis were the predominant microscopic lesions. Neospora caninum-like tachyzoites were found in the brain and skeletal muscles, and tissue cysts were found in the brain. The organism was not Toxoplasma gondii, as T. gondii antibody was not found in the indirect fluorescent antibody test in serum samples from the puppy and the dam, and the organism in the dog's brain did not react with T. gondii antibody in the immunoperoxidase test.

Animals↗
PubMed1989

A Neospora-like protozoon found in an aborted bovine placenta.

Portions of the placenta and kidneys from a 5-month-old bovine fetus were examined histologically. The placental cotyledonary villi were necrotic and protozoa were found in lesions. The organisms were in trophoblasts, periodic acid Schiff-negative and did not react in an immunoperoxidase test using anti-Toxoplasma gondii serum. Individual zoites were approximately 5 x 2 microns and the biggest collection was 45 x 35 microns. The organism in the present case was structurally distinct from Sarcocystis spp. and Toxoplasma gondii, but resembled Neospora caninum.

Abortion, Veterinary↗
PubMed2003

Assessment of antibody avidity in aborting cattle by a somatic Neospora caninum tachyzoite antigen IgG avidity ELISA.

A Neospora caninum IgG avidity ELISA was carried out on the basis of a somatic N. caninum tachyzoite antigen. The test was validated using experimentally infected calves, where a clear maturation of the IgG avidity over time could be demonstrated. At a maximum of 82 days after infection (d.p.i.), all animals showed antibody avidities ranging above 35%, and respective sera were thus defined as highly avid. Sera of 103 naturally infected seropositive cows with abortion (N. caninum association was provided by a N. caninum PCR-positivity of the fetus in 40 cases) and 139 seropositive animals without abortion history were concurrently examined. Significantly lower avidities were observed in aborting cows when compared to animals without abortion problems (P<0.01). While the avidity of sera collected before abortion remained practically constant until abortion, a significant increase of avidity could be observed in samples collected weeks to months after abortion (P<0.01). The avidities of non-aborting animals from farms with or without abortion problems did not differ significantly with time and were mainly located in the high avidity area. These data indicate that low avidities are not necessarily linked to recent N. caninum infection but can also be an indicator for increased abortion risk in cattle.

Abortion, Veterinary↗
PubMed2001

Recent advances in understanding the epidemiology of Neospora caninum in cattle.

INTRODUCTION: Neospora caninum is the most frequently diagnosed cause of cattle abortion in New Zealand and is an important pathogen worldwide. The parasite has been found in aborted bovine foetuses and in puppies with neurological disease. Recent developments have provided new insights into the epidemiology of the disease that are reviewed in this article. TRANSMISSION: Transplacental infection is of major importance in the spread of N. caninum overseas. Most congenital infections result in the birth of apparently healthy calves. Seroepidemiological studies indicate introduced point-source infections are also likely, as do investigations of abortion outbreaks in cattle herds attributed to N. caninum. Horizontal transmission is an important determinant of the stability of infection prevalence in a herd. Two potential sources of horizontal transmission that have recently been reported are: via a canine definitive host and; cow-to-calf transmission through pooled colostrum or milk. Transmission parameters for the organism have been estimated using mathematical modeling, to explore the epidemiology and options for control of N. caninum infection in dairy cattle in the absence of precise epidemiological data. LIFE-CYCLE: Seroepidemiologic studies, combined with the knowledge that dogs can be a definitive host, provide evidence supporting a dog-cattle life-cycle. The importance of dogs in the epidemiology of bovine neosporosis is not yet clear. It is likely that N. caninum oocysts in dog faeces could serve as a source of infection for cattle and recent studies have shown that the canine and bovine isolatesflare the same organism. Infection of cattle orally exposed to oocysts has been demonstrated experimentally but not in nature. It is not known if other wild carnivores may serve as definitive hosts of N. caninum. CONCLUSION: Despite active research for over a decade, very little is known about the mechanisms of transmission of N. caninum. Vertical transmission is well documented but horizontal spread and the pathogenesis of abortion from this disease need further investigation. It is evident that, even with a very high probability of vertical transmission, some form of horizontal transmission is required for the disease to persist in a herd.

Journal Article↗
PubMed2002

Control options for Neospora caninum infections in cattle--current state of knowledge.

This article reviews control options for Neospora caninum infection and abortion in cattle, drawing on published literature and the authors' own research in this field. Apart from the successful use of embryo transfer to prevent congenital infection in calves born to infected cows, there are currently no accepted control methods for the prevention of abortions in cattle. The epidemiological data at hand suggest that concomitant infections with bovine pestivirus increase the risk of abortion significantly and that these infections, for which effective vaccines exist, should therefore be controlled. While vertical transmission appears to be the major route of infection in cattle, there is also a role for postnatal transmission, involving a definitive host. Presently, the control of dogs and their access to bovine tissues, particularly potentially infected placentae and other foetal tissues, appear to be the most prudent control methods. There are some indications that vaccination against N. caninum may aid in the prevention of abortions. Suggestions for control options are limited by our current lack of actual experiences with control strategies. Further practical fieldwork is needed in this area.

Journal Article↗
PubMed2003

Prevalence of antibodies to Neospora caninum in dogs of rural or urban origin in central New Zealand.

AIM: To investigate the seroprevalence of Neospora caninum infection in populations of dogs from dairy farms, sheep/beef farms and urban areas in the central part of New Zealand. It was postulated seroprevalence would be higher for farm dogs than urban dogs if the life-cycle of this parasite involves transmission between dogs and cattle. METHODS: Serum samples were obtained from dogs that lived on dairy farms (n=161), sheep/beef farms (n=154) and in urban situations (n=150). The relative risk of detecting antibodies to N. caninum using an immunofluorescent antibody test (IFAT) was compared between farm and urban dogs. RESULTS: The relative risk of having a titre of > or = 1:200 to N. caninum was 2.43 (95% CI=1.88-3.14) for dairy-farm dogs and 3.16 (95% CI=2.48-4.02) for sheep/beef-farm dogs, compared with urban dogs. At this titre, which is currently used in New Zealand to indicate seropositivity, seroprevalence of N. caninum infection was 30.7% in urban dogs, 74.5% in dairy-farm dogs and 96.8% in sheep/beef-farm dogs. CONCLUSION: This observation is consistent with a cycling of this disease between cattle and dogs on farms in New Zealand and with higher exposure of dogs to N. caninum on farms than occurs in urban environments. The prevalence of antibodies in all three groups of dogs tested in this study (dairy-farm dogs, sheep/beef-farm dogs and urban dogs) is higher than has generally been reported elsewhere. New Zealand farm dogs have a higher serological prevalence of N. caninum infection than urban dogs. CLINICAL RELEVANCE: Management and disease control practices that break the life-cycle of transmission between cattle and dogs should assist in controlling cattle abortion due to N. caninum.

Journal Article↗
PubMedDate not supplied

Ultrastructure of tachyzoites, bradyzoites and tissue cysts of Neospora caninum.

Dividing tachyzoites of Neospora caninum were 4 x 3 microns and had ultrastructural characteristics typical for the cyst-forming coccidia. Unusual ultrastructural characteristics of fully-formed tachyzoites included no micropores, 8-12 anterior and 4-6 posterior rhoptries, and a few posterior micronemes. Most tachyzoites were located free in the host cell cytoplasm; only a few occurred within a parasitophorous vacuole. Parasite multiplication appeared to be rapid because most organisms were in various stages of endodyogeny. Neural tissue cysts of N. caninum were 24.3 x 19.2 microns and contained 50-200 bradyzoites (7.3 x 1.5 microns), which lacked micropores. The cyst wall was 0.74-1.12 microns thick and consisted of the primary cyst wall (the parasitophorous vacuole membrane) and a thick granular layer with electron-dense vesicles.

Animals↗
PubMed1994

The phylogeny of Neospora caninum and Toxoplasma gondii based on ribosomal RNA sequences.

Neospora caninum is a newly described cyst-forming coccidium which is the cause of severe neurological disease in dogs. The parasite is morphologically similar to Toxoplasma gondii, but the two species can be differentiated serologically. In order to define the phylogenetic position of N. caninum, we have determined 16S-like rRNA sequences from three members of the family of Sarcocystidae: N. caninum, T. gondii, and Sarcocystis fusiformis. The 16S-like rRNA genes from the three parasites were amplified by polymerase chain reaction and the sequences were determined by direct solid-phase sequencing. The sequences derived were computer aligned with several other 16S-like rRNA sequences from protozoan parasites to construct phylogenetic trees. The study confirmed that N. caninum should be classified as a member of the family Sarcocystidae. However, because of the close relationship to T. gondii it seems questionable that N. caninum should be placed in a new genus.

Animals↗
PubMedDate not supplied

Neospora caninum infection in English Springer Spaniel littermates. Diagnostic evaluation and organism isolation.

Progressive paraparesis developed in four male English Springer Spaniel pups from a litter of five during the first 10 weeks of life. Two of the pups, which had the earliest onset of neurologic signs, were euthanatized without further workup. However, a detailed investigation was completed on the remaining two littermates at 12 weeks of age. Both pups had progressive paraparesis for 3 to 4 weeks before presentation, with one dog developing subsequent asymmetric pelvic limb extensor rigidity. Based on results from neurologic examination, cerebrospinal fluid (CSF) analysis, electrophysiology, and muscle/nerve biopsy, a presumptive diagnosis of protozoal polyradiculitis and polymyositis was made. Necropsy of the most severely affected pup confirmed the clinical diagnosis of inflammatory nerve root and muscle disease but no organisms were found. To increase the potential yield of organisms, the second pup was placed on immunosuppressive doses of corticosteroids and euthanatized 2 weeks later. Numerous organisms were found in lesions in muscle and the central nervous system. Organisms grew in tissue culture and were isolated from the peritoneal fluid of gerbils inoculated with infected tissue. Organisms were not isolated from inoculated mice, guinea pigs, rabbits, and hamsters. No parasites were seen in feces or tissues of three cats fed infected dog tissues. Serologic testing demonstrated a strong positive titer to Neospora caninum in both pups, and electron microscopy showed the characteristic morphology of this parasite.

Animals↗
PubMed1990

Infection of mice with Neospora caninum (Protozoa: Apicomplexa) does not protect against challenge with Toxoplasma gondii.

Neospora caninum and Toxoplasma gondii are structurally related protozoal parasites of mammals that may cause abortion and neonatal morbidity and mortality. Groups of mice were subcutaneously inoculated with 10(5) live zoites of the NC-1 or NC-3 isolates of N. caninum and reinoculated with an identical number of live zoites 2 weeks later. Groups of mice which were injected subcutaneously with Hanks balanced salt solution served as controls. Three weeks after the final N. caninum inoculation, one-half of the mice were inoculated subcutaneously with 2.5 x 10(4) zoites of the RH isolate of T. gondii and the other half were inoculated subcutaneously with 2.5 x 10(4) zoites of the GT-1 isolate of T. gondii. Serum samples taken from mice on the day of T. gondii inoculation were negative for specific antibodies to T. gondii, but mice inoculated with N. caninum had reciprocal titers of greater than or equal to 800 to this protozoan. All of the mice died after challenge with T. gondii, and no significant differences (P greater than 0.05) between the survival times of mice inoculated with either isolate of N. caninum and those of control mice were seen. This study indicates that N. caninum and T. gondii are distinct biologic entities and not closely related isolates.

Animals↗
PubMed1993

Detection of Neospora caninum in tissue sections using a murine monoclonal antibody.

A murine monoclonal antibody (MAb 6G7), isotype IgG2a, produced against tachyzoites of Neospora caninum (isolate NC-1) reacted specifically with tachyzoites of N. caninum in an indirect immunofluorescent antibody test. MAb 6G7 did not react with tachyzoites of Toxoplasma gondii, sporozoites of Isospora suis, Eimeria bovis, or E. tenella, or merozoites of E. bovis in the indirect immunofluorescent antibody test. MAb 6G7 reacted positively with both tachyzoites and bradyzoites of N. caninum in an avidin-biotin peroxidase complex immunohistochemical test on formalin-fixed paraffin-embedded tissues. No reaction was observed with the following: tachyzoites and bradyzoites of T. gondii, T. gondii-like parasites, or Hammondia hammondi; bradyzoites of Frenkelia microti; schizonts and merozoites of Sarcocystis-like organisms; schizonts, sarcocysts, and oocysts/sporocysts of S. cruzi; schizonts and merozoites of S. canis; schizonts of S. hirsuta, S. tenella, and S. capracanis; merozoites of S. neurona and S. neurona-like organisms, E. bovis, or Haemoproteus sp.; bradyzoites and merozoites of S. montanaensis; bradyzoites of S. odocoileocanis, S. cruzi, and S. tenella; meronts, sexual stages, and caryocysts of Caryospora sp. and C. bigenetica; micromerozoites, macromerozoites, and schizonts of Hepatozoon canis; sporozoites, sexual stages, and oocysts of Cryptosporidium parvum and C. baileyi; trophozoites of Monocystis lumbrici, Tritrichomonas foetus, and Balantidium coli; tissue cysts and bradyzoites of Besnoitia sp. and B. jellisoni; amastigotes of Leishmania sp.; and trophic theronts of Ichthyopthirius multifilis. MAb 6G7 reacted with tachyzoites and bradyzoites of N. caninum in natural and experimental infections in dogs, cattle, mice, rats, sheep, and goats, indicating that host origin of the tissues did not affect the performance of the test.

Animals↗
PubMed1992

[Neospora abortion in cattle in The Netherlands].

Three cases of bovine protozoal abortion at three different dairy farms are reported. Multiple abortions had occurred, on two farms, and a sporadic abortion on the third farm. Histopathological examination of foetal tissues revealed a distinctive multifocal necrotising encephalitis as well as focal inflammatory lesions in the myocardium, liver, kidney and lung. In one foetus protozoal tissue cysts were found in the brain and individual and clustered tachyzoites were seen in brain, and lung. In another foetus a cluster of tachyzoites was seen in a section of a placentoma. Immunohistochemically, tissue cysts as well as tachyzoites reacted with Neospora caninum antiserum. Tachyzoites were also detected in the brain lesions of the other two foetuses. The preliminary results of a histopathological survey of aborted bovine foetuses indicate that this protozoal infection may be an important cause of bovine abortion in The Netherlands.

Abortion, Veterinary↗
PubMed1992

Neospora caninum (Apicomplexa) in a stillborn goat.

Tissue cysts of Neospora caninum were found in sections of brain from a stillborn pygmy goat. The tissue cysts had 1-2-microns-thick cyst walls and stained with anti-N. caninum serum in an immunohistochemical test. Glial nodules, mononuclear perivascular cuffing, and foci of inflammation were associated with N. caninum tissue cysts throughout the brain. This report indicates that N. caninum can be transmitted transplacentally in goats.

Animals↗
PubMed2005

[Survey of Neospora caninum in cattle in some provinces in the Eastern Anatolian region.].

This study was carried out in order to investigate the presence of Neospora caninum in cattle in the Elaziğ, Malatya, Muş and Bingöl provinces from January 2003- May 2004. Blood samples were collected from 513 cattle and 32 aborting cows that were of various breeds and ages in all provinces. Sera were obtained from these animals and antibodies against N. caninum were investigated using the enzyme-linked immunosorbent assay (ELISA). A commercially available competitive ELISA (cELISA) kit (VMRD, Inc., Veterinary Medical Research and Development, Pullman, WA, USA. Product Code 5NO5.20) was used to detect the N. caninum antibodies in the sera. Out of 513 cattle in the region, 36 (7.01 %) were found to be seropositive by cELISA. Seropositivity rates obtained by cELISA were 15.00% in Elaziğ, 4.00% in Malatya, 4.86% in Muş and 4.69% in Bingöl. One of the 32 aborting cows (3.12 %) was found to be seropositive against N. caninum.

English Abstract↗
PubMed1992

Factors affecting the survival of Neospora caninum bradyzoites in murine tissues.

Studies were conducted to determine factors that influence the survival of bradyzoites of Neospora caninum within tissue cysts in the brains of experimentally inoculated mice. Viable tissue cysts were detected in the brains of mice inoculated 13 mo previously with either of 2 isolates (NC-1 or NC-2) of N. caninum. Bradyzoites within tissue cysts of the NC-2 isolate survived for at least 14 days at 4 C in refrigerated brain homogenates. Bradyzoites within tissue cysts of the NC-2 isolate also survived in the intact brain of a mouse carcass refrigerated at 4 C for 7 days. Bradyzoites within tissue cysts of the NC-3 isolate were killed by freezing at -20 C for 1 day.

Animals↗