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W Wouda

Publications and source records attributed to W Wouda.

At least 37 records · Page 2Linked to original sources
PubMed2000

Diagnosis and epidemiology of bovine neosporosis: a review.

Neospora caninum is a protozoan parasite that was first described in dogs in 1988. Subsequently the parasite has been associated with abortion in cattle. Evidence is accumulating that neosporosis is a major cause of reproductive failure in cattle all over the world. Recent knowledge of neosporosis is reviewed with emphasis on the diagnosis and epidemiology of the disease in cattle. In addition, attention is paid to strategies for disease control and prevention.

Abortion, Veterinary↗
PubMed1999

Characteristics of Neospora caninum-associated abortion storms in diary herds in The Netherlands (1995 to 1997).

Abortion storms in 50 dairy herds in The Netherlands were reported in which there was a strong association with Neospora caninum-infection. The duration of the abortion storms ranged from 6 to 65 d (mean 41.5 d). The cumulative proportion of aborting cows ranged from 0.11 to 0.57 (mean 0.26) of the animals at risk. An apparent seasonal influence was noted as most abortion storms occurred during the summer and early autumn. The prevalence of antibodies to N. caninum in 50 herds which had had an abortion storm was compared with that of 100 control herds which had no history of an abortion storm. Seroprevalence was estimated by testing a 20% cross sectional herd sample using a tachyzoite lysate-based ELISA method. Seroprevalence in case herds (range 17 to 87%, mean 51.5%) was significantly higher than that in control herds (range 0 to 53%, mean 13.9%). For most herds the seroprevalence levels were equal across all age groups, which suggests that the infection had been perpetuated by vertical transmission. In these herds, the abortion storms appeared to be induced by factors causing recrudescence of a N. caninum-infection in chronically infected animals rather than being the result of a recent introduction. In 6 case herds the seroprevalence in the dairy cows was significantly higher than in the young stock, which may have been attributable to superimposed postnatal infection.

Abortion, Veterinary↗
PubMed1999

Risk factors for Neospora caninum-associated abortion storms in dairy herds in The Netherlands (1995 to 1997).

A 2 to 1 matched case control study design was used to analyze herd level risk factors for Neospora caninum-associated abortion storms in 47 dairy herds. Data were obtained using a questionnaire regarding the state of affairs at the farms over the 2 years prior to the abortion storm. The questionnaire included 120 variables considered to be potential risk factors for either introduction of infection or recrudescence of chronic infection. The relationship between risk factors and case control pairs was analyzed by conditional logistic regression using a three-steps procedure. In addition, cross sectional serology was used to assess the possible role of concomitant infections. The main factors that were significant in the analysis and that were considered to have potential biological relevance were the presence of dogs, the presence of poultry, and the feeding of moldy maize-silage during summer. For both the presence of dogs and the presence of poultry on the farms, a linear relationship was found between the number of animals and the assessed risk for an abortion storm. These findings suggest a possible role of these species in the transmission of N. caninum. Further evidence for such a role of dogs was the significant association between the presence of dogs and the presence of seropositive cattle in the control herds. The feeding of moldy fodder is considered to be a factor which may induce recrudescence of a latent N. caninum-infection by mycotoxins causing immune suppression. We also found some evidence for a possible influence of management practices around calving and a high prevalence of retained afterbirths. No significant association was found for herd level prevalence of antibodies to bovine viral diarrhea virus, bovine herpesvirus 1, Leptospira hardjo or Salmonella dublin.

Abortion, Veterinary↗
PubMed1999

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

Dogs from dairy farms with a known prevalence of Neospora caninum antibodies in the cattle were examined for the presence of N. caninum antibodies using an ELISA. Data of farm dogs were compared with those of dogs examined at a university clinic, which originated mainly in urban areas. Of the 152 farm dogs, 36 (23.6%) were seropositive to N. caninum, which was significantly higher than the proportion of seropositives in the clinic dog population (19 of 344, 5.5%). Seroprevalence was significantly higher (P = 0.01) in female dogs than in male dogs. Seroprevalence in dogs increased with age, indicating postnatal infection. Seropositivity to N. caninum in farm dogs was strongly correlated with a high prevalence of N. caninum antibodies in the cattle. At farms where no dogs were present, the seroprevalence to N. caninum in the cattle was significantly lower (P = 0.0002) than in farms where dogs were present. These findings suggest that there is a relationship between N. caninum infection of farm dogs and cattle. Since dogs have been shown to be definitive hosts of N. caninum, cattle may be infected by exposure to canine oocysts. Further research is needed to find out whether and how dogs may acquire the infection from cattle.

Animals↗
PubMed1999

Pathological changes in cobalt-supplemented and non-supplemented twin lambs in relation to blood concentrations of methylmalonic acid and homocysteine.

In a controlled field study of three years' duration we evaluated the effect of cobalt supplementation on pathological changes in cobalt/vitamin B12-deficient Texel twin lambs grazing the same cobalt-deficient pasture. Semi-quantitative evaluation of the histopathology of liver and brain was done on 44 sets of twins. Pathological changes were related to blood concentrations of vitamin B12, methylmalonic acid, and homocysteine. Lesions were mainly confined to the liver and brain. Acute hepatic changes were characterized by steatosis, hepatocytic degeneration, and single cell necrosis. Chronic changes consisted of bile duct proliferation, the presence of ceroid containing macrophages, and fibrosis in the portal triads. Many non-supplemented lambs showed polymicrocavitation and Alzheimer type II reaction in the brain. Polioencephalomalacia was observed in three non-supplemented lambs but was regarded as a secondary lesion. Our results indicate that the main lesions found in cobalt/vitamin B12-deficient lambs are acute and chronic hepatitis. These lesions were associated with low concentrations of vitamin B12 and high concentrations of methylmalonic acid and homocysteine in the blood. The liver lesions were also associated with polymicrocavitation of the brain, probably as morphological evidence of hepatoencephalopathy.

Animals↗
PubMed1998

Increased risk of abortion following Neospora caninum abortion outbreaks: a retrospective and prospective cohort study in four dairy herds.

Explosive abortion outbreaks in 4 Dutch dairy herds during 1992 to 1994 are reported. In 50 of 51 fetuses submitted during the first 3 wk of the outbreaks characteristic histological lesions compatible for infection with Neospora caninum were seen. Diagnosis of infection was confirmed by immunohistochemistry in 40 fetuses (78%). No evidence for other abortifacients was found. The abortion risk of the herds was investigated in a prospective and retrospective cohort study. The prospective study showed that cows aborting during the outbreaks and N. caninum seropositive nonaborting cows had a two- to three-fold increased risk of abortion compared with N. caninum seronegative cows. Retrospective examination showed that seropositive nonaborting cows had an increased risk of abortion before the outbreaks, which may indicate that these animals were infected with N. caninum prior to the outbreaks. It is concluded that serostatus can be used for selective culling of cows to decrease future risk of abortion in dairy herds.

Abortion, Veterinary↗
PubMed1998

Abortion risk in progeny of cows after a Neospora caninum epidemic.

A study was done of the descendants of cows from 4 dairy herds in which there had been N. caninum abortion outbreaks. Precolostral antibodies to N. caninum were demonstrated in 34 of 50 (68%) F1 calves and in 14 of 17 (82%) F2 calves from cows that aborted during the outbreaks. In 214 F1 progeny, N. caninum seroprevalence was nearly 50%, and there was a significant association between serostatus of the offspring and serostatus of dams. These observations indicated that congenital infection was an important mode of transmission after abortion outbreaks in these herds. A total of 52 abortions was recorded in 293 pregnancies of F1 progeny cows (1 to 3 pregnancies per animal). It was found that seropositive F1 cows had a three-fold increased abortion risk compared with seronegative F1 cows. In 2 of 10 abortions in seronegative cows evidence for N. caninum infection was found, suggesting that a low level of postnatal infection may also have occurred. It is concluded that N. caninum-infected calves should not be used as replacement stock, to decrease the future risk of abortion in dairy herds.

Abortion, Veterinary↗
PubMed1998

Serodiagnosis of neosporosis in individual cows and dairy herds: A comparative study of three enzyme-linked immunosorbent assays.

The performance of three enzyme-linked immunosorbent assays (ELISA) for detection of antibodies to Neospora caninum in bovine sera was evaluated by using various categories of sera. Two commercial ELISA methods, one based on chemically fixed intact tachyzoites and one based on a sonicate lysate of whole tachyzoites, were compared with an in-house ELISA based on a detergent lysate of whole tachyzoites. A brief description of the development of the latter ELISA is also given. There was good agreement among all three tests with regard to postabortion sera. By using acute-phase abortion sera from cows with confirmed N. caninum-induced and non-N. caninum-induced abortions, satisfactory levels of sensitivity and specificity were calculated for all tests. In addition, similar test results were obtained with postpartum samples from dams and calves. However, considerable differences were found between test results of sequential samples and cross-sectional and total-herd samples. Apparently, these discrepancies were due to different sensitivities of the tests for detection of low antibody levels in chronically infected animals. It is suggested that these differences were primarily due to the use of different antigens and different test sample dilutions. It is concluded that all tests are applicable as an additional diagnostic tool in cases of abortion in cattle and for monitoring of congenitally infected calves. For herd screening, the lysate-based ELISAs appear to be more adequate because of their higher sensitivities.

Abortion, Veterinary↗
PubMed1997

Serological response over time to recombinant Neospora caninum antigens in cattle after a neosporosis-induced abortion.

Recombinant Neospora caninum tachyzoite antigens were evaluated in an enzyme-linked immunosorbent assay (ELISA) for recognition by serum antibodies (Ab) from Neospora-infected cattle. Serum samples were obtained every 2 to 3 weeks for 8 to 15 months from 10 cows with histories of Neospora-associated abortion. Serum samples were also obtained from offspring of these animals and from a large number of cows that had aborted a fetus, due to infection by Neospora or other organisms, at various times during gestation. All 10 cows had positive ELISA Ab titers to both recombinant N. caninum tachyzoite antigens after abortion, during subsequent gestation, and after parturition. In three cows, there was a noticeable peak in Ab titers early in gestation. Calves born to Neospora-infected cows also had positive titers of Ab to the recombinant tachyzoite antigens, and these titers remained elevated for at least 4 months after birth. A portion of the serum immunoglobulin in calves may have been derived from colostrum of infected cows. A calf born from a seronegative mother had a positive ELISA titer only after being fed colostrum from a seropositive cow. However, precolostral titers in calves born from Neospora-infected cows were high at birth, suggesting that the parasite was transmitted to the fetus via the placenta and induced a humoral immune response therein. The recombinant tachyzoite antigens were also useful for corroborating clinical diagnoses of Neospora-induced abortion. A significant difference (P < 0.05) between anti-recombinant antigen Ab titers in cows that aborted due to Neospora and those in cows that aborted from other causes was found.

Abortion, Veterinary↗
PubMed1997

Bovine fetal neosporosis: a comparison of epizootic and sporadic abortion cases and different age classes with regard to lesion severity and immunohistochemical identification of organisms in brain, heart, and liver.

Eighty bovine fetuses with confirmed neosporosis were used to score lesion severity and presence of parasites in brain, heart, and liver. A comparison was made between epizootic and sporadic abortion cases. The possible influence of fetal age was also investigated. Histologic lesions of multifocal encephalitis, myocarditis, and periportal hepatitis with or without focal hepatocellular necrosis were almost always observed. Neospora caninum tachyzoites were identified immunohistochemically in 85% of the brains, 14% of the hearts, and 26% of the livers. Tissue cysts were observed in 21% of the brains. Significant differences between epizootic and sporadic abortion cases were found only in the liver. Hepatic lesions were more prominent and N. caninum tachyzoites were observed more frequently and in higher numbers in epizootic cases. Examination by immunohistochemistry of the liver in addition to the brain can be highly contributive diagnostically, particularly in epizootic cases. There were no significant age-related differences except for a higher presence of tachyzoites in the hearts of younger fetuses (3-4 months gestational age).

Abortion, Veterinary↗
PubMed1997

Serological diagnosis of bovine fetal neosporosis.

To evaluate the efficacy of fetal serology in the diagnosis of bovine neosporosis abortion, sera from 48 fetuses with immunohistochemically confirmed neosporosis and 42 fetuses without demonstrable Neospora caninum were examined in the indirect fluorescent antibody test (IFAT). Fetal sera were diluted 2-fold starting at a 1:25 dilution. Antibodies to N. caninum were detected in 31 of 48 (65%) fetuses with confirmed neosporosis; the IFAT antibody titers were 1:25 (5 fetuses), 1:50 (17 fetuses), 1:200 (6 fetuses), and > or = 1:800 (3 fetuses). Neospora caninum antibodies were found in 3 of 42 fetuses without demonstrable protozoa; in all 3 cases, a high titer was found suggesting undiagnosed congenital neosporosis. A recombinant antigen enzyme-linked immunosorbent assay was not useful for the detection of fetal antibodies to N. caninum.

Abortion, Veterinary↗
PubMed1993

[Neospora caninum as a cause of lameness symptoms in young dogs].

At the age of three weeks, two Labrador retriever puppies, out of a litter of nine, suffered from diarrhoea and muscular weakness. One puppy died within two days. The other was killed after a tetraparalysis had developed. Two weeks later a third puppy was killed because of a paretic hind leg. At the age of five months another dog had to be euthanized because of progressive hind limb ataxia. Pathological examination revealed polyradiculoneuritis, multifocal encephalomyelitis and polymyositis. In the lesions, particularly in the nerve roots, free and clustered protozoal tachyzoites were found. In the central nervous system tissue cysts were seen. By use of immunohistochemistry the protozoal organisms were identified as Neospora caninum, a newly recognized protozoan in the dog. Fresh bovine heart, that had been fed to the puppies, is regarded as the possible source of infection.

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

[Salmonella dublin on dairy farms in the North of the Netherlands].

During the last century many calves and cows with Salmonella dublin infections are diagnosed in the North of the Netherlands, especially in the province of Friesland. In this paper are retrospectively traced the problems by paratyphoid infections in cattle, from 1919 till now, the diagnosis of which was made at the Animal Health Service in Friesland and North-Netherlands. Over the decennia a decrease is noticed for the percentage of necropsies of calves with S. dublin infections, although some irregular peaks appear. However since 1988 an increase is observed in dairy farms with S. dublin problems, revealing high mortality in calves, abortions and sick cows.

Animals↗
PubMed1992

[Pasteurella haemolytica serotypes in cattle].

Eight-two bovine Pasteurella haemolytica strains were serotyped. The majority of the strains were isolated from calves which had died from fibrinous pneumonia and small numbers from cases of pleuritis, sepsis and abortion. A total of eight different serotypes were noticed. Serotype A1 was found to be the most prevalent 37.8 per cent, followed by serotype A2 with 20.7 per cent. Antibiotic resistance was found for sulfonamide, tetracycline and penicillin in about half of all strains. Conventional combination of biotype to serotype per strain was not confirmed by the results of arabinose and trehalose fermentation.

Animals↗