Investigation of serology for diagnosis of outbreaks of botulism in cattle

Serology has been used to diagnose retrospectively types C and D outbreaks of botulism in cattle in Australia and this study has investigated whether the approach would be applicable in England and Wales. Three hundred sera from routine surveillance submissions in England and Wales were used as a negative control population. Some stored sera were available from a small number of clinical cases of botulism and 125 samples were collected from cohort groups of clinical cases in four new outbreaks of botulism. Three of these outbreaks were identified as being caused by type D Clostridium botulinum toxin. Sera were tested by antibody ELISA in laboratories in Australia and Germany. There was no increase in the proportion of animals seropositive to type C or D antibody in the botulism-associated cattle. The proportion of samples which were seropositive to type D antibodies was <2% in both the negative control and outbreak populations. It was concluded that single time serology is unlikely to be helpful for retrospective diagnosis of outbreaks of type D botulism in England and Wales.     

A Bayesian evaluation of six diagnostic tests for foot-and-mouth disease for vaccinated and non-vaccinated cattle

The sensitivity and specificity of six ELISA tests for foot-and-mouth disease (FMD) to discriminate between sero-converted (for non-structural FMD virus proteins) and non-sero-converted cattle were evaluated for vaccinated and unvaccinated cattle. Since none of the tests could be considered as a proper reference test and for about half of the tested sera the true status (sero-converted or not for non-structural proteins, i.e. presence of antibodies) of the animals was unknown, a Bayesian analysis employing a latent class model was used that did not rely on the use of a reference test or gold standard. Prior information about prevalence for subsets of the data and specificity of the tests was incorporated into the analysis. The specificity of the six tests for vaccinated and non-vaccinated cattle ranged from 96 to 99%. For vaccinated cattle, one test stood out with an estimated sensitivity of 94% (95% CI from 89.8 to 98.1%). Second best for vaccinated cattle were two tests with estimated sensitivities of 85% (95% CI from 78.9 to 89.7%) and 92% (95% CI from 86.2 to 95.6%). For non-vaccinated cattle, the sensitivities of these three tests were around 97%. The remaining three tests showed lower estimated sensitivity for vaccinated cattle, ranging from 57 to 79%.     

Serological Survey of Bluetongue Virus Serotype‐8 Infection in South American Camelids in Switzerland (2007–2008)

Background: Outbreak of bluetongue virus serotype‐8 (BTV‐8) infection in domestic ruminants in Northern Europe. Objective: To investigate the South American camelids' (SAC) susceptibility to BTV‐8 infection, their role in the epidemiology of the disease, and the use of currently available serological screening tests in SAC in an endemic region. Animals: Three hundred and fifty‐four unvaccinated and 27 vaccinated SAC (170 llamas, 201 alpacas), ranging in age from 1 month to 17 years between June and August 2008. The SAC originated from 44 herds throughout the country, representing 10% of the Swiss SAC population. Methods: Prospective, observational study of a convenience sample of SAC. Serum samples were analyzed with 2 serological screening tests. When results diverged, a 3rd ELISA was carried out for confirmation (ID Screen Bluetongue Competition ELISA kit). Results: All sera from the 354 unvaccinated animals were negative in the endemic region. Reliable seroconversion was observed after administration of 2 doses of vaccine. Conclusions and Clinical Importance: This study suggests a low susceptibility of SAC to BTV‐8 despite the presence of the virus in the cattle and small ruminant population, indicating that SAC do not play a major role in the epidemiology of BTV‐8. Furthermore, these results indicate that commercially available serological tests for BTV‐8 can be used in SAC.     

The Dutch Brucella abortus monitoring programme for cattle: the impact of false-positive serological reactions and comparison of serological tests

The Dutch national Brucella abortus eradication programme for cattle started in 1959. Sporadic cases occurred yearly until 1995; the last infected herd was culled in 1996. In August 1999 the Netherlands was declared officially free of bovine brucellosis by the European Union. Before 1999, the programme to monitor the official Brucella-free status of bovine herds was primarily based on periodical testing of dairy herds with the milk ring test (MRT) and serological testing of all animals older than 1 year of age from non-dairy herds, using the micro-agglutination test (MAT) as screening test. In addition, serum samples of cattle that aborted were tested with the MAT. The high number of false positive reactions in both tests and the serum agglutination test (SAT) and complement fixation test (CFT) used for confirmation seemed to result in unnecessary blockade of herds, subsequent testing and slaughter of animals. For this reason, a validation study was performed in which three indirect enzyme-linked immunosorbent assays (ELISAs), the CFT and the SAT were compared using a panel of sera from brucellosis-free cattle, sera from experimentally infected cattle, and sera from cattle experimentally infected with bacteria which are known to induce cross-reactive antibodies (Pasteurella, Salmonella, Yersinia, and Escherichia). Moreover, four ELISAs and the MRT were compared using a panel of 1000 bulk milk samples from Brucella-free herds and 12 milk samples from Brucella abortus- infected cattle. It is concluded that the ELISA obtained from ID-Lelystad is the most suitable test to monitor the brucelosis free status of herds because it gives rise to fewer false-positive reactions than the SAT.     

Emergence of suspected type D botulism in ruminants in England and Wales (2001 to 2009), associated with exposure to broiler litter

Scanning surveillance by the Veterinary Laboratories Agency revealed the emergence of suspected botulism in ruminants in 2003, presented as flaccid paralysis. From 2003 to 2009, 168 cattle and 19 sheep incidents were recorded, with mortality between 5 and 80 per cent. All sheep incidents and 95 per cent of cattle incidents had proximity to broiler litter. From July 2006, the gut contents collected from 74 affected cattle and 10 affected sheep were tested for Clostridium botulinum toxins using mice bioassays and for organisms by culture. Type D toxin was identified in 32 per cent of cattle and 18 per cent of sheep samples. C botulinum type D organisms were identified in 40 per cent of cattle and 30 per cent of sheep samples, but broth from one sample reacted with C and D antisera. Type C botulism has previously been reported more commonly than type D in the UK and has been associated with the use of poultry litter as fertiliser, bedding or feed. The almost exclusive association with C botulinum type D toxins or organisms in the gut contents in this survey suggests a change in the source or epidemiology of botulism in the UK. The source of C botulinum type D was uncertain. Broilers may carry C botulinum type D in their gut flora subclinically. The emergence of a new type D strain, or changes in broiler husbandry and nutrition, medication and other enteric infections may have affected colonisation with C botulinum. Further investigation of poultry and farm environments for sources of type D awaits the development of tests for C botulinum toxins that do not require the use of mice.     

Comparative immunogenicity of two bivalent botulinum vaccines

OBJECTIVE: To compare the ability of a new single-dose botulinum vaccine containing a non-mineral oil adjuvant with a single dose of a conventional botulinum vaccine product to produce antibody to Clostridium botulinum types C and D in cattle in Northern Australia. DESIGN AND PROCEDURE: One hundred and fifty Brahman steer weaners were randomly divided into two groups receiving either a single dose of CSL Bivalent Botulinum vaccine or Websters Singvac. Blood samples were collected at 0, 8 and 24 weeks and tested by antibody ELISA. The final samples were also tested by the toxin neutralisation test, to test titres of neutralising antibody. RESULTS: Six months after inoculation, cattle vaccinated with Websters Singvac had ELISA antibody response twice that of CSL conventional product. However, this difference was only evident for neutralising antibody to type C botulinum toxin. Both products produced similar titres of type D neutralising antibody after a single dose. CONCLUSION: Websters' Singvac produces a greater neutralising antibody response to type C botulism upon single inoculation than a conventional vaccine. The product produces an equivalent neutralising antibody response to type D.     

The immunization of calves against heartwater: subsequent immunity both in the absence and presence of natural tick challenge

Cattle, vaccinated as calves with Cowdria ruminantium-infected tick stabilate, were challenged 6, 12 and 24 months later. In the absence of tick challenge, vaccination of calves induced a partial immunity against subsequent challenge at 12 and 24 months. In animals exposed to ticks, the resistance was no better than that of control, unvaccinated cattle. When they were challenged at 6 months of age there was no difference between vaccinated and unvaccinated calves, either in the absence or presence of tick challenge, and all the animals manifested a high degree of natural resistance. This study therefore suggests that the value of vaccinating Afrikander-cross calves in heartwater endemic areas should be further investigated. The indirect fluorescent antibody (IFA) test proved to be a valuable means of monitoring the serological response of vaccinated animals and detecting the sero-conversion of animals exposed to tick infection. On one hand, there was good correlation between the febrile reaction and the results of the IFA test on the sera of vaccinated and control cattle challenged with the heartwater agent, in that all sero-positive animals were resistant to challenge. On the other hand, though, a considerable percentage of the animals that were serologically negative were also resistant to challenge.     

Evaluation of four commercial serum ELISAs for detection of Mycobacterium avium subsp. paratuberculosis infection in dairy cows

During the first 3 months of 2006, a study was performed on four dairy cattle herds with a history of clinical paratuberculosis, to evaluate different enzyme-linked immunosorbent assays (ELISAs). Serum samples obtained from 326 animals were analysed using four ELISAs to detect antibodies to Mycobacterium avium subsp. paratuberculosis (MAP). Kappa (kappa) concordance coefficients in pairwise comparisons of the ELISA outcomes ranged up to 0.22 (linear kappa) and 0.25 (quadratic kappa). When the borderline positives obtained were considered as negatives, kappa values remained low (kappa up to 0.19). Having performed the serological tests, faecal samples were then obtained from 55 animals (including all animals testing positive in two or more ELISAs) from the same herds. Faecal culture and faecal polymerase chain reaction (PCR) for the detection of MAP were negative in all cases. The results indicate that neither the currently available serum ELISAs nor faecal culture and PCR are effective for the early detection of MAP in dairy cattle.     

Evaluation of an ELISA for detection of antibodies to Babesia bovis in cattle in Australia and Zimbabwe

An enzyme-linked immunosorbent assay (ELISA) for antibodies to Babesia bovis was evaluated in comparison with the indirect fluorescent antibody test (IFAT) in Australia and Zimbabwe. Positive and negative threshold values for the ELISA were set using sera from cattle of known infection status. Sensitivity and specificity estimates for the ELISA based on 158 positive sera from cattle experimentally infected with Australian isolates of B. bovis and 318 negative sera collected from B. bovis-free herds in Australia were 100% and 99.4%, respectively. The specificity of the assay in Africa, based on 328 sera from B. bovis-free herds in Kenya and South Africa, was 99.7%. The ELISA was compared with the IFAT using sequential sera from 16 calves experiencing primary B. bovis infections, and a total of 777 field sera collected from B. bovis-endemic herds in Australia and Zimbabwe. In primary infections, the ELISA and IFAT detected antibodies at or about the same time. With sera from endemic herds, the performance of the ELISA was at least comparable with that of the IFAT. Two hundred and fourteen of 221 sera that were negative by IFAT, were negative by ELISA, and 428 of 439 sera that were clearly positive by IFAT were positive by ELISA. Of 117 sera that gave equivocal (suspect or weak positive) results in the IFAT, 20 were positive by ELISA, 7 were suspect and 90 were negative. We conclude that the ELISA will be useful for epidemiological studies on B. bovis in Australia and Zimbabwe, and probably elsewhere.     

Diagnosis of botulism types C and D in cattle by a monoclonal antibody-based sandwich ELISA

This study was undertaken to evaluate two monoclonal antibody-based sandwich ELISAs (sELISAs) for the detection of Clostridium botulinum neurotoxins (BoNTs) types C and D from culture-enriched intestinal content samples from cattle. To validate the diagnostic significance of the presence of cultivable, toxin-producing C botulinum in the intestines of cattle, samples from both suspect and non-suspect botulism cases were examined. BoNT was detected by both sELISAs in a greater number of suspect animals than by direct testing of uncultured samples by mouse bioassay. One sELISA detected two BoNT C and one BoNT Group III mosaic isoform in three animals that were missed by the other, and both sELISAs failed to identify samples from two mouse bioassay-positive BoNT C animals. BoNT D was also detected in one non-suspect sample by one of the sELISAs.     

Use of an ELISA for serodiagnosis of parasitic bronchitis in cattle.

The enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of parasitic bronchitis in cattle was evaluated in naturally injected, experimentally infected and vaccinated animals. Significant antibody titres could be demonstrated from five weeks after animals had been exposed to the parasite, so that infected animals could be identified during the summer. The test did not give false positive results in vaccinated animals. The technique proved particularly useful in revealing latent infections in milking herds in the autumn when heavy burdens of worms in the lungs do not generate any larvae in the faeces.     

Relationship between the anti-FMD virus antibody reaction as measured by different assays, and protection in vivo against challenge infection.

The antibody response of cattle after vaccination against foot-and-mouth disease (FMD) virus was monitored using the serum neutralization test (SNT), the sandwich ELISA, liquid-phase ELISA, sandwich competition ELISA, liquid-phase competition ELISA, and the liquid-phase sandwich competition (blocking) ELISA. The competition ELISAs (in particular the "blocking" ELISA) were the most effective at detecting reactivity in these cattle sera. However, 95% of negative sera also competed in the most sensitive ELISA (the "blocking" ELISA) to titres of 1:32 (4% of the sera competed to a titre of 1:128). Comparisons between the different ELISAs, and between these ELISAs and the SNT, demonstrated that the tests were not measuring exactly the same reaction of antibody with FMD virus. With respect to the capacity of animals to resist FMD virus challenge, neither the SNT nor the competition ELISAs were consistently able to identify such animals. The anti-FMD virus antibody titres obtained could be classified into three zones; the "white zone" wherein antibody titres were high and donor animals likely to be protected; the "black zone" wherein antibody titres were low and donor animals likely to be susceptible to infection; the "grey zone" wherein the antibody titres were intermediary and no interpretation could be made with respect to protection. Assays such as ELISA and SNT cannot and do not measure immunological protection; they are a measure of antibody responses and nothing more, and should be interpreted in terms of the "three zone" phenomenon.     

Preparation and evaluation of the specificity of Parafilaria bovicola antigen for detection of specific antibodies by ELISA

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies in bovine sera against Parafilaria bovicola nematodes was developed and its sensitivity was compared with the immunodiffusion (ID) method. An exoantigen of P. bovicola which was shown to contain four major polypeptides was used in these procedures. The serological reactivity of the antigen polypeptides was defined by using the enzyme-linked immunoelectrotransfer blot technique (EITB) and whole-worm extract proteins. It identified only four serologically reactive polypeptides with sera from one experimentally infected calf and a verified field case. These two positive sera reacted mainly with four major antigens which coincided in molecular weights of the polypeptides of the exoantigenic preparation, namely, 43, 39, 28 and 25 KDa. Calves experimentally infected with P. bovicola showed a positive reaction with ELISA at 4 months after inoculation, and after this period a rapid increase in serum antibody response occurred. In these cases the ID reaction was observed for the first time at 7 months after inoculation. The specificity of an ELISA method using crude exoantigen preparation of P. bovicola was tested for the diagnosis of bovine parafilariasis. No cross-reactivity was detected when the P. bovicola exoantigen preparation was tested against sera from calves experimentally infected with Onchocerca lienalis, as well as against the sera from cattle naturally infected with Dictyocaulus viviparus or from cattle chronically infected with Ostertagia ostertagi. In addition, testing of 740 field sera from cattle in areas non-endemic and endemic for P. bovicola indicated a specificity of the antigen preparation used. Forty sera from laboratory-confirmed field cases of P. bovicola infection were tested by ELISA and immunodiffusion. All of these sera were ELISA positive, whereas only 70% of these were positive in the ID test. Seven (2.1%) of 328 sera from 21 herds from non-endemic P. bovicola areas were ELISA positive, as opposed to none in the ID test. Of the 94 sera from six herds in areas endemic for P. bovicola infection, 51 (54%) were ELISA positive whereas only 24 (26%) were positive in the ID test. When 56 slaughtered cattle, with varying degrees of meat condemnations due to parafilariasis, were tested for P. bovicola specific antibody, 91% of the serum samples were positive by ELISA. These results suggest that the exoantigen of P. bovicola can be used in a sensitive and reliable serological detection of parafilariasis by ELISA.     

Comparison of a competitive inhibition ELISA and the card agglutination test for detection of antibodies to Anaplasma marginale and Anaplasma centrale in cattle

OBJECTIVE: To compare a recently developed recombinant MSP-5 competitive inhibition ELISA with a card agglutination test for detection of antibodies to Anaplasma marginale and Anaplasma centrale in Australian cattle. MATERIALS AND METHODS: The ELISA was compared with the card agglutination test using 208 sera from cattle in Anaplasma-free herds, 86 sera from cattle experimentally infected with A marginale or A centrale and 757 sera from cattle in areas endemic for A marginale. RESULTS: The specificity of the ELISA, based on testing 208 sera from cattle in Anaplasma-free areas, was 99.5%, and the sensitivities for detection of antibodies to A marginale and A centrale in sera from the experimentally infected cattle were 98.0% and 100%, respectively. For the same sets of sera, the specificity of the card agglutination test was 98.6% and the sensitivities for detection of antibodies to A marginale and A centrale were 98.0% and 100%, respectively. For the 757 sera collected from cattle in areas endemic for A marginale, the agreement between the ELISA and the card agglutination test depended on the positive threshold selected for the ELISA. The maximum achievable agreement was 91.5% (kappa = 0.73; 95% confidence interval 0.66, 0.79). CONCLUSION: We conclude that the competitive inhibition ELISA is a useful alternative to the card agglutination test for detection of A marginale or A centrale infection in cattle. The assay should be particularly useful for epidemiological applications such as prevalence studies and control programs.     

Evaluation of a commercially available enzyme-linked immunosorbent assay for detecting antibodies to Fasciola hepatica and Fasciola gigantica in cattle, sheep and buffaloes in Australia

A commercially available ELISA for detecting antibodies to liver fluke was evaluated for use in Australia. Milk and serum samples from cattle and sheep in which infection with Fasciola hepatica was confirmed by detection of eggs in faeces were used to estimate sensitivity. Similar samples collected from cattle and sheep outside the F. hepatica-endemic area were used to estimate specificity. The ELISA was also evaluated for detecting antibodies to F. hepatica in milk from sheep and antibodies to Fasciola gigantica in sera from cattle and buffaloes, but with small numbers of samples. In cattle, the sensitivity and specificity of the ELISA were 98.2% and 98.3% using serum and 97.7% and 99.3% using milk. In infected herds, 41.4% and 41.5% of animals were positive in the serum and milk ELISAs, respectively, whereas F. hepatica eggs were found in faecal samples from 26.5% of animals. In sheep, the sensitivity of the ELISA was 96.9% and the specificity was 99.4%. In infected flocks, 60.2% of animals were positive in the serum ELISA and F. hepatica eggs were found in faecal samples 52.2% of animals. There was perfect agreement in the ELISA between paired serum and milk samples collected from ewes. The assay detected antibodies in sera from cattle and buffaloes with natural and experimental F. gigantica infections. In the experimentally infected animals, antibodies were detected 2 weeks post-infection. We conclude that the ELISA will be a valuable tool for diagnosing F. hepatica infections in cattle and sheep. The assay may also be useful for diagnosing F. gigantica infections but further studies are required to establish sensitivity and specificity.     

Evaluation of commercial ELISA kits for the detection of antibodies against bluetongue virus

The aim of this study was to estimate the diagnostic value of different commercially available ELISA kits for the detection of bluetongue virus (BTV) antibodies in infected and vaccinated animals. The relative specificity of ELISA kits was evaluated using a panel of sera originating from healthy cattle, never vaccinated nor exposed to BTV. All ELISA kits applied had a high relative specificity (99.3 - 100%). The relative sensitivity of ELISA kits assessed using a panel of sera collected from BTV infected cattle was also high and similar for all the kits (97.3 - 100%). However, the relative sensitivity evaluated on the basis of testing vaccinated animals was different: the highest sensitivity was found for Ingenasa, PrioCHECK and ID VET ELISAs (96.5 - 98.3%). Slightly lower sensitivity was calculated for Pourquier and LSI kits (82.8% and 85.4%, respectively) and much lower sensitivity was found for VMRD ELISA kit (69.5%). The repeatability of BTV ELISA kits was expressed as a coefficient of variation (CV) of results of sera tested 5 times in the same day and in different days by the period of 2 months, by the same person, in the same conditions, and by using the same equipment. The CVs of sera tested in all ELISA kits ranged from 6.1 to 9.8% and were below 10% threshold adopted as a maximum for the acceptable repeatability of the method. In conclusion, it can be stated that the applied ELISA kits can be a valuable diagnostic tool for the serological monitoring studies in the BTV contaminated premises. All the methods are very specific and sensitive when testing BTV infected animals. Nevertheless, the Ingenasa and PrioCHECK can be the most useful in sero-surveillance of livestock following vaccination.     

Comparison of three serological tests in the diagnosis of Brucella infection in unvaccinated cattle in Eritrea

Three serological methods, the Rose-Bengal test (RBT), the complement-fixation test (CFT) and an indirect enzyme-linked immunosorbent assay (I-ELISA) were compared for the detection of Brucella-infected animals in unvaccinated cattle herds in Eritrea. In this study, 71 herds first were classified as positive or negative for Brucella infection on the basis of at least one animal being seropositive by RBT and CFT. All the 159 RBT-positive samples from the 26 seropositive herds and 214 RBT-negative samples randomly selected from the seropositive herds and from the 45 negative herds were tested further by CFT and I-ELISA. Using the ELISA titer as main predictor, and incorporating the RBT results, a logistic model was built to predict the CFT-negative or -positive status of individual sera and to estimate sensitivity and specificity. Whilst the ELISA titers (< or =20) accurately predicted all the negative sera in herds that were also negative by the CFT, the number of seropositive animals was higher by ELISA in herds that had positive animals. Serum samples which give higher degrees of agglutination with the RBT need not be re-tested with CFT; consideration of the seropositive status of a herd should be taken into consideration on defining the cut-off optical density readings for ELISA.     

Safety, efficacy and cross-protectivity of a live intranasal aerosol haemorrhagic septicaemia vaccine

The safety, efficacy and cross-protectivity of a live intranasal aerosol haemorrhagic septicaemia vaccine containing Pasteurella multocida serotype B:3,4 were tested in young cattle and buffaloes in Myanmar, where more than 1.5 million animals had been inoculated with this vaccine between 1989 and 1999. A recommended dose of 2 x 10(7) viable organisms was used for the efficacy test. The administration of 100 times the recommended dose to 50 cattle and 39 buffalo calves was innocuous. Seven months after they were vaccinated, three of three buffaloes were protected and 12 months after they were vaccinated, three of four buffaloes were protected against a subcutaneous challenge with serotype B:2 which killed three of three unvaccinated buffaloes. Twelve months after they were vaccinated, eight of eight cattle survived a serotype B:2 challenge, which killed four of four unvaccinated controls. The vaccinated cattle had developed serum antibodies detectable by the passive mouse protection test. Indirect haemagglutination tests on sera taken from cattle 10 days and five weeks after they were vaccinated showed high titres of antibodies. The serum of vaccinated cattle cross-protected passively immunised mice against infection with P. multocida serotypes E:2, F:3,4 and A:3,4.     

Evaluation of an enzyme-linked immunosorbent assay (ELISA) for serodiagnosis of infectious bovine rhinotracheitis infection, with results of a preliminary survey

An indirect enzyme linked immunosorbent assay (ELISA) procedure was evaluated against the serum neutralisation test (SNT) for the detection of antibodies to infectious bovine rhinotracheitis virus (bovine herpesvirus type l), using 2028 sera from 166 dairy and 172 beef cattle herds. The results showed the ELISA to give high levels of agreement with the SNT in classifying positive and negative sera (98% and 97% respectively). Such disagreements as did occur involved weakly reactive sera with SNT titres of % or less. A number of sera (n=123) with trace neutralising activity of doubtful diagnostic significance were found to give marginal reactivity with ELISA. ELISA absorbance values were found to be highly correlated with SNT titres (r=0.909) on an overall basis, though agreements were lower with individual sera. The ELISA procedure was quicker, cheaper, and detected more reactors than the SNT. It also allowed results to be obtained with a number of sera which were unsuitable for testing by SNT because of their cytotoxic nature. Analysis of ELISA results showed reactors to be present in 57% of tested sera, representing 81% of cattle herds. Reactor rates for sera and herds in the South Island, (37% and 58%), were significantly lower than for those in the North Island (64% and 88%). Antibody prevalence was also found to be significantly lower in districts having a low annual rainfall (<850 mm), and to be lower in beef cattle than in dairy cattle. A surprising exception to the latter occurred in low rainfall districts, where dairy cattle showed significantly lower reactor rates than local beef animals.     

Evaluation of a commercially available ELISA kit for detection of antibodies to Anaplasma marginale and Anaplasma centrale in cattle in Australia and Zimbabwe

A newly available competitive inhibition ELISA kit for the serological diagnosis of anaplasmosis was evaluated in Australia and Zimbabwe. In Australia the performance of the test was compared with the card agglutination test (CAT).The assay was evaluated using negative sera collected from Anaplasma-free herds, positive sera from experimentally infected cattle and sera from Anaplasma marginale-endemic herds. The sensitivity and specificity of the ELISA in Australia were 100 % and 83,3 %, respectively, and the sensitivity and specificity of the CAT were both 100%. The agreement between the ELISA and CAT in the sera from endemic herds was 86,4 % (kappa = 0,718). The specificity of the ELISA in Zimbabwe was 100%. No meaningful estimate of sensitivity was possible in Zimbabwe because few known positive sera were available for testing, but all eight known positive sera that were available were clearly positive. We conclude that the ELISA is a useful alternative to the CAT for epidemiological studies.The ELISA kits have advantages over the CAT in that the ELISA is more robust and reagents are better standardized, but the kits are expensive.