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Prompt and accurate laboratory testing of women before or during antenatal days is necessary for detecting humoral immunological responses against cytomegalovirus (CMV) infection and assessing risk of congenital transmission. CMV is the most common viral etiology with the greatest propensity to induce neonatal pathologies. Most healthcare facilities in developing countries rely solely on anti-CMV IgM and IgG assays in diagnosing CMV infections. However, these parameters have some worrisome limitations. This study reviewed the significance of IgG avidity testing as a highly sensitive and specific tool that improves decisions regarding diagnosis of maternal and congenital CMV infections. We conducted this review from relevant published articles using an extensive literature search made through PubMed, Scopus and Google scholar on the concepts of congenital CMV (CCMV) transmission and clinical significance of IgG avidity testing in diagnosis of CCMV infections. Findings from our review revealed that IgG avidity testing in some developed societies was frequently utilized to resolve dilemmas associated with serodiagnosis of CMV infections, however, there is paucity of information in regards to its use in developing countries. The non-inclusion of IgG avidity testing during serological investigations of CMV could be a reason why congenital CMV infections and associated pathologies often go underdiagnosed in developing countries.

Following primary human cytomegalovirus (HCMV) infection, virus-specific IgG antibody shift from low to high avidity with individual variations in the rate of avidity maturation. The kinetics of the avidity maturation of IgG specific for HCMV nuclear antigen in pregnant women with primary infection was investigated. Absorbance values used for avidity index calculation of 286 sequential sera collected from 69 pregnant women with primary HCMV infection were retrieved. Percent difference in absorbance values of IgG antibody bound to the solid phase after urea treatment (IgG avidity) between early (T1, 0-90, median 31 days) and late (T2, 91-180, median 136 days) serum samples was calculated for each woman. Three groups of women were identified: 24/69 (34.8%) women showed high (>100%) avidity increase between T1 and T2 (pattern H), 29/69 (42%) low (<50%) increase (pattern L), and 16/69 (23.2%) intermediate increase (pattern I). Avidity values in T1 samples were significantly higher in women with pattern L compared to women with pattern H ( P = 0.01). Altogether, 28/69 (40.6%) women transmitted HCMV infection to their fetuses. Fetal infection preferentially occurred ( P < 0.01) in women with pattern H (15/24, 62.5%) compared with women with pattern L (7/29, 24.1%). In conclusion, different patterns of IgG avidity maturation can be detected following primary HCMV infection. Pregnant women with pattern H (rapid IgG avidity increase) appear to be at higher risk for fetal infection, whereas, pregnant women developing early antibody with high avidity appear to be at a lower risk of vertical transmission. J Med. Virol. 85:1960-1967, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Background: Toxoplasma specific IgM antibodies; the common serologic marker in diagnosis of acute toxoplasmosis has its own limitations. Confirmatory testing with other markers, introduced as a complementary tool in distinguish acute and chronic infections is unusual in Iran. In the present study, we investigated the correlation between the results of IgM ELISA, IgA ELISA, and IgG avidity tests in the diagnosis of toxoplasmosis to demonstrate the necessity of confirmatory testing in serodiagnosis of infection in the country. Methods: A total of 107 positive Toxoplasma IgG and IgM sera were obtained from patients referred to private laboratories and stored at -20 °C for futures use. Serologic tests were set up in duplicate to analyze the serum levels of IgG, IgM, IgA, and IgG avidity antibodies using commercial ELISA kits. The results were presented as semi quantitative for IgG, IgM and IgA ELISA, and Relative Avidity Index in percentage for IgG avidity test. Pearson's correlation coefficient (rp) was applied to analyze the data. Results: Of 107 serum samples, T. gondii specific IgM and IgA antibodies were positive in 67.3% and 53.3%, respectively. Besides, 29.9% of the sera displayed low avidity for IgG antibodies. The rp was - 0.572 (P<0.01) between the IgG avidity and IgM ELISA, - 0.364 between the IgG avidity and IgA ELISA (P<0.01), and 0.564 between the IgM and IgA ELISA (P<0.01). Conclusion: The study strongly highlights the necessity of confirmatory testing in differential diagnosis of acute and chronic toxoplasmosis in Iran. [ABSTRACT FROM AUTHOR]

Background. The IgG avidity test is usually used for differentiating between primary and non-primary HCMV infection within 3 months. Weak avidity is highly suggestive of a primary infection, while high avidity tends to exclude it.An indeterminate or moderate avidity, however, does not allow a clear dating. Since there are several avidity tests with different performances, those tests that are able to minimize the results with indeterminate/moderate avidity are particularly useful. Objectives. The aim of our work was to evaluate the results obtained with two IgG avidity tests in IgG and IgM anti-HCMV positive patients. Study Design. 113 anti-HCMV IgG and IgM positive samples were tested with Enzime Linked Fluorescent Assay (ELFA) and Chemiluminescence Immuno Assay (CLIA) IgG avidity test. Results. 21 samples (18.6%), 50 (44.2%) and 42 (37.2%) with ELFA and 53 samples (46.9%), 10 (8.8%) and 50 (44.2%) with CLIA were found to have respectively low, indeterminate/moderate and high avidity. Of the 50 ELFA indeterminate avidity samples, 32 (64%), 10 (20%) and 8 (16%) were found to have respectively low, moderate and high CLIA.avidity. For 11 cases of the 32 ELFA indeterminate avidity and CLIA low avidity, there were previous data showing a seroconversion within three months. In a case of the 8 ELFA indeterminate avidity and CLIA high avidity, there were, instead, previous data of IgG and IgM positivity already four months earlier. Conclusions. It appears that the CLIA test for IgG avidity is more effective than ELFA for dating HCMV infection.

We report the detection of specific IgA antibodies and the determination of IgG avidity in sequential serum samples from a patient exhibiting significant levels of Toxoplasma-specific IgM antibodies for seven years after the onset of the clinical symptoms of toxoplasmosis. IgM antibodies were detected by an indirect immunofluorescence test and by three commercial enzyme-linked immunosorbent assays (ELISA). Anti-T. gondii IgA was quantified by the a-capture ELISA technique using a commercial kit. As defined by the manufacturer of the IgA ELISA test used, most patients with acute toxoplasmosis have antibody levels > 40 arbitrary units per ml (AU/mL). At this cut-off level, the patient still had a positive ELISA result (45 AU/mL) in a serum sample taken one year after the beginning of clinical manifestations. The IgG avidity-ELISA test was performed with the Falcon assay screening test (F.A.S.T.®) - ELISA system. Avidity indices compatible with a recent Toxoplasma infection were found only in serum samples taken during the first 5 months after the onset of the clinical symptoms of toxoplasmosis. These results show that the interpretation of positive IgM results as indicative of recently acquired toxoplasmosis requires additional laboratory confirmation either by other tests or by the demonstration of a significant rise in the antibody titers in sequential serum samples.

Copyright of Revista do Instituto de Medicina Tropical de São Paulo is the property of Instituto de Medicina Tropical de Sao Paulo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista do Instituto de Medicina Tropical de São Paulo is the property of Instituto de Medicina Tropical de Sao Paulo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Abstract: A search for specific IgM antibodies was used for the detection of primary human cytomegalovirus (HCMV) infections, but the significance of the results is limited by the possible persistence of specific IgM over time, the fact that they are also produced during episodes of reactivation or reinfection, and possible cross-reactions with other viruses. Anti-HCMV antibody screening was carried out to assess the positive predictive value of detecting specific IgM antibodies using IgG and IgM enzyme-linked immunosorbent assays (ELISAs) in 6990 patients examined during the period 2005–2007. In comparison with IgG avidity, the positive predictive value of screening by IgM ELISA alone was 49.3%, which increased to 73% when the presence of IgM was confirmed by an enzyme-linked fluorescent assay (ELFA). The predictive values of highly or weakly positive IgM ELISA alone were respectively 68.8% and 16.4%, but increased to 83.1% and 39.1% if IgM was confirmed by ELFA. The positive predictive value of the IgM/IgG ratio ranged from 26.7% for a low ratio and the detection of IgM by ELISA alone, to 90.7% for a high ratio and ELFA-confirmed IgM detection. These findings indicate that a specimen in which highly positive IgM ELISA values are confirmed by ELFA, or which shows a high IgM/IgG ratio, is a good indicator of infection occurring within the previous three months. [Copyright &y& Elsevier]

Abstract: Background: The interpretation of a positive IgM antibody result to human cytomegalovirus (HCMV) in a pregnant woman is of major importance for the correct management of the pregnancy. Determination of HCMV-specific IgG avidity is considered an useful approach for distinguishing IgM antibody due to primary HCMV infection from IgM antibody elicited during non-primary infection. Objective: Comparative evaluation of eight commercial HCMV IgG avidity assays currently available in Europe. Study design: A panel of 198 sequential samples collected from 65 pregnant women at 0–90, 91–180, and >180 days after the onset of primary HCMV infection was retrospectively tested by Abbott, BioMérieux, Bio-Rad, DiaSorin, Diesse, Euroimmun, Radim, and Technogenetics HCMV IgG avidity assays according to the manufacturer''s instructions. Results: None of the 198 samples tested yielded identical scores by the kits under evaluation. The Euroimmun and Radim assays showed the best correlation with expected results in terms of low (0–90 days), intermediate (90–180 days) and high (>180 days) avidity results, respectively. The best accuracy in diagnosing a recent (<90 days after the onset) or non-recent (>180 days after the onset) primary HCMV infection was shown by Radim followed by Euroimmun and Diesse. The best correlation with a well established in-house developed HCMV IgG avidity assay was shown by Radim. Conclusions: HCMV IgG avidity kits need to be improved and standardized. In the meantime, highly specific IgM assays are preferable for screening purposes in pregnant women. [Copyright &y& Elsevier]

AIM: The diagnosis of acute toxoplasmosis depends on the presence of immunoglobulin M (IgM), but it may persist for a long time in some cases. The objective of this study was to determine the role and accuracy of IgG avidity for the detection of acute Toxoplasmosis in early pregnancy. METHOD: The study included 160 women. Sera were screened for anti-Toxoplasma IgG and IgM and for IgG-avidity using ELIZA. PCR was done for confirmation in selected group of specimens. This study was performed at the College of Medicine, King Faisal University, Saudi Arabia from January 2008 through April 2009. RESULTS: 32 cases of low avidity were negative IgM while 15 cases of high avidity were positive IgM. 16 cases of low avidity were positive IgG. The accuracy of low avidity in relation to positive IgM revealed a sensitivity, specificity, positive predictive value, negative predictive value and likelihood ratio of 77.0%, 51.5%, 64.0%, 66.7% and 1.58 respectively. The accuracy of low IgG avidity in comparison with PCR demonstrated 91%, 45.7%, 60.4% and 84.2% respectively. CONCLUSION: Negative IgM didn't exclude recent Toxoplasma infection and positive IgG may be present with recent infection. IgG avidity testing help in accurate differentiation of recent infections. [ABSTRACT FROM AUTHOR]

The article discusses a study which examined serum samples from 711 sheep from 109 farms in Minas Gerais State, Brazil. In this study, enzyme-linked immunosorbent assay (ELISA) and indirect fluorescence antibody test (IFAT) were was used to determine the Toxoplasma gondii seroprevalence. It notes that Toxoplasma gondii seroprevalence was 31.1% by ELISA and 43.2% by IFAT. According to the author, 19% of the serum samples contained low avidity Immonoglobulin G (IgG) antibody. Variables associated with Toxoplasma gondii including age, sex and breed, were analyzed as risk factors for toxoplasmosis.

We encountered a woman whose infant developed congenital toxoplasmosis. Serum Toxoplasma gondii antibody titers (320×) at 12 weeks of gestation increased to 5120× at 25 weeks. Toxoplasma immunoglobulin M was 2.8 index, and immunoglobulin G avidity index was 23%. Cyclic administration of acetylspiramycin was maintained from 22 weeks until delivery. Multiplex-nested polymerase chain reaction of maternal blood and amniotic fluid at 28 weeks both tested positive for Toxoplasma DNA. A male neonate weighing 2916 g was born at 38 weeks via cesarean section. No abnormalities were detected by physical and funduscopic examinations, whereas a head computed tomography of the neonate revealed three independent intracranial calcifications. The infant underwent therapy with pyrimethamine and sulfadiazine for one year. Serum titers of Toxoplasma gondii antibodies were all less than cut-off values between 5 and 12 months after birth, but all increased up to positive levels 18 months after birth. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this work was to carry out a study on caprine toxoplasmosis in the state of Minas Gerais, Brazil. To determine the prevalence of toxoplasmosis in goats in Minas Gerais, 767 sera from goats were tested by ELISA (enzyme-linked immunosorbent assay) and IFAT (indirect fluorescence antibody test). The prevalence of antibodies to Toxoplasma gondii was 43.0% and 46.0% by ELISA and IFAT, respectively. It was observed that 26.8% of the goats show low-avidity IgG to T. gondii. These results suggest the presence of animals in recent phase of toxoplasmosis in Minas Gerais. The risk factors for toxoplasmosis in goats were: age over 36 months (OR=1.21; IC 95% 1.02–1.44), use of pen (OR=1.83; IC 95%1.01–3.31) and pure breed animals (OR=2.49; IC 95% 1.11–5.59). [Copyright &y& Elsevier]

Background The accuracy of IgG avidity assays is crucial for the diagnosis of primary CMV infection in pregnancy. Objective To compare the performance of the second generation avidity assays LIAISON ® CMV IgG Avidity II and VIDAS ® CMV IgG Avidity II for the diagnosis of primary infection in pregnant women. Study design In our laboratory, in sera of pregnant women presenting with positive CMV IgG and positive CMV IgM, the two avidity assays were run in parallel from January 2013 to April 2015. Results The results of the 2 avidity assays were analyzed in 280 sera. The correlation between the second generation LIAISON ® and VIDAS ® avidity results was significantly higher than between the results of the first generation assays (77% versus 49%, p < 0.001). Discrepant results were mainly explained by the difficulty of the VIDAS ® assay to reach intermediate and high avidity status over time, suggesting the superiority of the LIAISON ® assay to achieve high avidity levels. In 4 sera from 3 pregnant women (1.4%) with documented primary infection the LIAISON ® avidity was falsely high. In these cases the level of CMV IgG was low (<50 U/mL). Conclusion The LIAISON ® CMV IgG Avidity II assay reached more rapidly higher avidity status than the VIDAS ® CMV IgG Avidity II. However, with the LIAISON ® CMV IgG Avidity II, we identified rare sera with high positive avidity values in documented recent seroconversion. The advantages and drawbacks of each assay must be known for a sound interpretation of the results. [ABSTRACT FROM AUTHOR]

Human toxocariasis is a zoonosis caused by infection with larvae of the ascarid nematode Toxocara canis and, less frequently, T. cati . Our study developed a method for distinguishing distant from recent human toxocariasis by assessing the avidity of the IgG antibodies. The avidity of specific antibodies increases with time after antigen challenge and assessment of the degree of avidity can be used to discriminate between recent and distant infections. The relative avidity was measured in 150 sera from children with visceral toxocariasis and in 46 sera from children with ocular toxocariasis. The probable time of infection was estimated on the basis of the medical history and clinical syndrome. Our study showed that 94·2% of positive sera collected from patients reporting infection > 6 months ago had high IgG avidity values, confirming distant toxocariasis, whereas 25·9% of positive sera taken < 6 months after infection showed low indices of IgG avidity. Our results suggest that measurement of the specific IgG avidity may assist in discriminating between recent and distant toxocariasis. The method can be used effectively to rule out (because of high avidity) a recently acquired infection. Low avidity is less reliable in discriminating between recent and distant infections. [ABSTRACT FROM AUTHOR]

Abstract: Methods used to diagnose Lyme borreliosis (LB) vary according to clinical presentations. A very good basis to clarify this nosological and clinical entity is the study published by the “European Concerted Action on Lyme Borreliosis” (EUCALB). In fact, only few studies were performed on cohorts of patients including all clinical forms of LB. For Erythema migrans, serology sensitivity is low (20% to 50%), while the sensitivity of culture or PCR reaches 50%. In early-complicated forms, serology is more sensitive (70 to 90%) with the presence of concomitant IgG and IgM. Screening for antibodies in CSF is very useful for the diagnosis of neuroborreliosis. For this clinical form, culture or PCR sensitivity is disappointing (10 to 30%). In arthritis and acrodermatitis chronica atrophicans (ACA), IgG serology is 100% positive with very high titers; however IgM serology is only positive in 5 to 10% of the cases. In ACA, culture sensitivity ranges from 20 to 60% and PCR sensitivity from 60 to 90%. Specificity of antibodies, natural exposure to the etiologic agent, and cross-reactivity are critical for the final interpretation of serological assessment. Only the use of “serological profiles” allows the exploitation of detailed results (isotypes, intensity). In this approach, IgG avidity could be constructive. The western-blot is intended to confirm the specificity of antibodies found in screening methods (Elisa). [Copyright &y& Elsevier]

Abstract: Sheep are important domestic animals in the Northeast region of Brazil due to their minimal rearing and maintenance costs, and to their production of both meat and milk. In animals, Toxoplasma gondii infection results in significant reproductive and economic losses. The epidemiology of toxoplasmosis in sheep in the Northeast of Brazil has been little studied; particularly in Rio Grande do Norte State. Sera from 102 sheep intended for consumption in Lajes were subjected to the Toxoplasma-ELISA test to detect anti-T. gondii specific IgG confirming a past infection. Of the total tested, 30 (29.41%) sera were positive for IgG with an increasing number of positive animals with advancing age. We used IgG avidity ELISA in 30 positive samples and observed that 6 (20%) had low avidity antibodies and 24 (80%) had high avidity antibodies. Epidemiological studies are required in order to identify sources of infection for these hosts as well as their impact on animal breeding in the region and risk of transmission to humans. [Copyright &y& Elsevier]

Abstract: Avidity tests can be used to discriminate between cattle that are acutely and chronically infected with the intracellular parasite Neospora caninum. The aim of this study was to compare the IgG avidity ELISA tests being used in four European laboratories. A coded panel of 200 bovine sera from well documented naturally and experimentally N. caninum infected animals were analysed at the participating laboratories by their respective assay systems and laboratory protocols. Comparing the numeric test results, the concordance correlation coefficients were between 0.479 and 0.776. The laboratories categorize the avidity results into the classes “low” and “high” which are considered indicative of recent and chronic infection, respectively. Three laboratories also use an “intermediate” class. When the categorized data were analysed by Kappa statistics there was moderate to substantial agreements between the laboratories. There was an overall better agreement for dichotomized results than when an intermediate class was also used. Taken together, this first ring test for N. caninum IgG avidity assays showed a moderate agreement between the assays used by the different laboratories to estimate the IgG avidity. Our experience suggests that avidity tests are sometimes less robust than conventional ELISAs. Therefore, it is essential that they are carefully standardised and their performance continuously evaluated. [Copyright &y& Elsevier]

Copyright of Revue Francophone des Laboratoires is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revue Francophone des Laboratoires is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of EMC-Gynecologie--Obstetrique is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Wiener Klinische Wochenschrift is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Very sensitive and allowing discrimination between IgG and IgM, the enzyme immunoassays are the most commonly used to carry out viral serologies. The presence of IgG corresponding to a natural or postvaccination immune status or to a latent or occult infection is a reliable information to assess the protection against some opportunistic or teratogenic infections respectively in children or pregnant women. The search of IgM by immunocapture is suitable to early diagnose the majority of common viral diseases in childhood, specially when presenting in an atypical form, and to attest a congenital rubella infection. Moreover, IgG avidity proved to be useful in dating an infection and confirming positive IgM results. However, viral infections localized at an entry site of the host, such as respiratory and enteric diseases, as well as syndromes of herpes simplex and enteroviral origin, do not represent indications of serological diagnosis. Provided its use with discernment, the serological diagnosis of viral infections have to be considered as a high performance and of low cost biological tool. [Copyright &y& Elsevier]

Abstract: Immunoglobulin G avidity assays are used to distinguish between the acute and chronic phase of several infectious diseases, and there is evidence of autoantibody affinity maturation also in autoimmune diseases. To assess whether the analysis of the avidity of autoantibodies against the protein tyrosine phosphatase-like IA-2 molecule and glutamic acid decarboxylase (GAD65) could improve the accuracy of risk assessment of progression to clinical type 1 diabetes, we established methods for the determination of the autoantibody avidity based on our previously developed time-resolved fluorometric IA-2 and GAD65 autoantibody (IA-2A and GADA) assays. The avidity indices of sequential plasma samples from six IA-2A-positive and seven GADA-positive prediabetic children were analysed applying elution with urea and diethylamine (DEA). For comparison, corresponding avidity indices of control children, who have remained non-diabetic for at least 3 years after seroconversion to IA-2A and GADA positivity, were analysed. For most of the children, only a slight fluctuation in the avidity index values was observed over time, although the titres for IA-2A and GADA varied substantially in some cases. The avidity indices of the prediabetic children remained within the same range as those of the control group throughout the follow-up. Our results indicate that the analysis of the avidity index levels of IA-2A and GADA does not improve the accuracy of the prediction of type 1 diabetes based on autoantibody detection. [Copyright &y& Elsevier]

Copyright of Revue Francaise des Laboratoires is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

PROBLEM: Toxoplasmosis is a major cause of congenitally acquired infections causing high degree of morbidity and mortality in the newborns. METHODS OF STUDY: IgG avidity method was used to distinguish the recent and more than 4 months old infection in a prospective cohort study for the first time in India. One hundred and eighty pregnant women presented in their first 4 months of pregnancy were included in this study. Their sera were tested for anti-Toxoplasma gondii antibodies using direct agglutination test, immunoglobulin (Ig)G and IgM-enzyme-linked immunosorbent assay, IgM-immunosorbent agglutination assay and VIDAS-IgG avidity. RESULTS: Overall IgG seroprevalence rate of toxoplasmosis was 45%. Only seven women (3.3%)were found to have IgM antibodies and only two of these showed low IgG avidity indicating recent infection of ≤4 months duration. One woman aborted spontaneously at her fourth month of gestation. In remaining five women the recent infection could successfully be excluded by IgG avidity testing. All these women had uneventful pregnancy. CONCLUSIONS: This study indicated that all IgM antibody positive pregnant must be tested for IgG avidity to rule out recent primary infection. [ABSTRACT FROM AUTHOR]

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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. [Copyright &y& Elsevier]

A longitudinal study was performed in a Swedish dairy herd where Neospora caninum had been isolated from a stillborn calf. Starting in autumn 1994, blood samples from all female animals in the herd were collected once yearly until 1999. The sera were analysed for presence of IgG1 antibodies to N. caninum by the iscom ELISA, and by an avidity ELISA to establish the timing of infection. In addition, data on reproductive performance were compiled. During the study the percentage of seropositive female animals increased from 63% to 87%. In 1994 a large number of young animals tested seropositive although their dams were seronegative, indicating that a transmission of the parasite other than the vertical had recently occurred. Low avidity values supported this assumption. The annual abortion rate increased from a mean of 2% before the initiation of the study to 9% in 1994-1998. During the same time, as judged by the avidity data, a large proportion of the animals shifted from being recently to being chronically infected. The source of the external infection in the herd could not be identified. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate the high rate of seroconversion for Neospora caninum in a dairy herd. Forty-five of 95 (47%) of the seronegative animals seroconverted within a period of 6 months. Seropositive animals were not equally distributed among age-groups. A high seroprevalence age-group of 8–30 months was housed together during a period of 4 months, indicating a point source infection within this period. A lack of association between the serological status of daughters and mothers also indicated horizontal transmission of the infection. Low avidity indices in the seroconverted animals confirmed a recent infection in this herd. However, there was no increased abortion rate in connection with the seroconversion, which indicates that mass seroconversions in dairy herds may remain unnoticed. There was circumstantial evidence that the farm dog played a role in the transmission of the infection to the cattle. However, also evidence was found for an unexplained ongoing horizontal transmission after the initial point source exposure. [Copyright &y& Elsevier]