Sensitivity and specificity of serological and bacteriological tests for contagious bovine pleuropneumonia

In 1990 an outbreak of contagious bovine pleuropneumonia (CBPP) occurred in Italy. Subsequent surveillance for CBPP was based on random sampling in bovine herds, serological controls on all animals moved from the herd of origin and controls on slaughtered animals. Official tests employed were the complement fixation test (CFT) and bacteriological isolation and typing. A total of 33,856 serum samples collected from herds in CBPP-free regions were used to define CFT specificity, while samples from 595 animals from infected herds were employed to define the sensitivity. Ninety-nine animals from three infected herds were used to estimate the sensitivity of the isolation technique. Results showed the specificity of CFT (threshold +1:10) to be 98% and sensitivity to be 63.79%. The sensitivity of the test did not change significantly, regardless of whether the lesions were caused by acute or chronic infection. The sensitivity of the isolation technique was 54.1%.     

Diagnosis of paratuberculosis in dairy cattle, using enzyme-linked immunosorbent assay for detection of antibodies against Mycobacterium paratuberculosis in milk

An ELISA containing lipoarabinomannan (LAM) antigen was used to detect antibodies in milk and serum for diagnosis of Mycobacterium paratuberculosis infection in dairy cattle. In experiment 1, milk and serum samples were obtained from 25 cows, and subjected to LAM ELISA testing immediately, and after 1 year of storage at -70 C. Milk samples, with and without a commonly used chemical preservative, were tested. There was no significant difference in LAM ELISA results between fresh and frozen samples or between preserved and unpreserved milk samples. In experiment 2, milk samples were collected daily from 30 cows over a 14-day period. The day-to-day coefficient of variation was 0.19 for milk LAM ELISA and was 0.15 for serum LAM ELISA, with no statistically significant time effect detected. In experiment 3, single milk, serum, and fecal samples were obtained from 764 cows. The fecal samples were cultured for M paratuberculosis to identify infected cows, and the serum and milk samples were subjected to LAM ELISA testing. Results were compared, using the area under the receiver operating characteristic curves. The milk LAM ELISA had specificity (+/- 95% confidence limits) of 87 +/- 8.1% when the cutoff was set at 50% sensitivity, and specificity of 83 +/- 9.1% when sensitivity was set at 60%. The area under the receiver operating characteristic curve was 0.85 +/- 0.03 for the milk ELISA and 0.75 +/- 0.02 for the serum ELISA. In this population of cattle, the milk LAM ELISA had comparable accuracy to serum LAM ELISA, although the milk LAM ELISA was slightly less reproducible (higher coefficient of variation).     

An immunodiffusion assay for the detection of canine leishmaniasis due to infection with Leishmania infantum

An immunodiffusion assay (IDA) with polyethylene glycol (PEG) was tested for usefulness as diagnostic test for canine leishmaniasis (CL). A comparative analysis of dog sera was made using IDA with PEG, immunofluorescence assay (IFA) and enzyme immunosorbent assay (ELISA) techniques. Fourty-four dogs from Italy with CL (endemic dogs) and eight Dutch dogs with CL contracted in South Europe (expatriate dogs) were tested together with 40 endemic and 35 expatriate controls. Specificity did not differ substantially among the serotests, ELISA in endemic dogs being the least specific (mean specificity given in IFA, IDA and ELISA, 100%, 98% and 93.5%, respectively). Sensitivity in expatriate dogs was 100% for all serotests but was highly variable in endemic dogs. In parasite-negative dogs, IFA had the most sensitivity, i.e., 80.5% compared to 69% for both ELISA and IDA. In contrast, ELISA in parasite-positive endemic dogs had a sensitivity of 100% whereas both IFA and IDA gave a sensitivity of 93%. Despite its slightly lesser sensitivity than IFA or ELISA (2-6% and 5% respectively) in endemically infected dogs, IDA with PEG method may help to bring the diagnosis of CL within reach of the veterinary practitioner.     

Isolation and characterization of Bordetella bronchiseptica from cats in southern Louisiana

The role of Bordetella bronchiseptica in respiratory disease of domestic cats is currently being explored. Clinical and experimental studies in the United Kingdom have shown Bordetella bronchiseptica to be a primary respiratory pathogen in cats; similar studies in the United States are limited. The purpose of this study is to report on the isolation, seroprevalence, and partial characterization of Bordetella bronchiseptica from shelter cats in southern Louisiana. A total of 614 cats from four local shelters were studied. All cats appeared to be asymptomatic for signs of respiratory disease. Bordetella bronchiseptica was isolated in 19/614 (3.1%) cats by oropharyngeal swab and in 6/614 cats by bronchial lavage. Using an antibody capture ELISA method, 148/614 (24.1%) cats were seropositive for Bordetella bronchiseptica. The 25 isolates of Bordetella bronchiseptica were further characterized by ribotype analysis, and a total of 17 different ribotypes were identified. Specific pathogen-free kittens were experimentally infected with five of the isolates, and four of the five isolates induced clinical signs typical of feline bordetellosis. It is concluded that Bordetella bronchiseptica is present in the cat population in southern Louisiana, the organism can be isolated from asymptomatic cats, some of these isolates can produce disease in specific pathogen-free kittens, and that Bordetella bronchiseptica isolates from cats in a relatively small geographic area are genetically diverse. This and other studies indicate that Bordetella bronchiseptica should be considered in cases of feline respiratory disease.     

Influence of orthodontic treatment in the primary dentition upon development of the dentition and craniofacial growth

The aim of the present study was to compare the sensitivity, specificity and usefulness of the DIG-ELISA, DOT-ELISA and Indirect ELISA tests for determining the seroprevalence of fasciolosis in cattle under tropical conditions in Mexico. To standardize the tests, positive and negative sera to F. hepatica from 88 Holstein Freisian adult cows located in an enzootic area of fascioliosis and 88 crossbred adult cattle from a fluke-free area were used. For the epidemiological study, 85 crossbred cattle between 1 to 7 years of age were used. Animals were bled every two months, from March 1995 to September 1996 and the sera obtained were stored at -70 degrees C, until used. Indirect ELISA showed a sensitivity of 96.5% and a specificity of 98.8%, DIG-ELISA 97.5% and 80.0% and DOT-ELISA 93.1% and 95.4%, respectively. During 1995, Indirect ELISA yielded the highest levels of IgG anti-F. hepatica antibodies. However, in 1996, after animal treatment with triclabendazole, DIG-ELISA tended to show higher percentages of antibody-positive animals, but it was not significantly different (p>0.05) from the other tests. Comparisons made in parallel to the faecal sedimentation test demonstrated that all serological tests detected higher percentages of positive animals. Only one serum out of ten (10%) of Paramphistomum spp. cross-reacted with the DOT-ELISA test, but no cross-reaction was observed with sera from animals with other parasites. All ELISA tests were highly sensitive and specific; they may be recommended for use in seroepidemiological surveys for F. hepatica.     

Sensitivity and specificity of antigen-capture ELISAs for diagnosis of Trypanosoma congolense and Trypanosoma vivax infections in cattle

Sensitivity and specificity of the FAO/IAEA antigen-ELISA kits for diagnosis of bovine trypanosomosis were investigated using sera from experimental cattle infected by tsetse challenge with cloned populations of Trypanosoma congolense (three populations) or T. vivax (one population). The kits are based on monoclonal antibodies that recognise internal antigens of tsetse-transmitted trypanosomes. Ten cattle were infected with each trypanosome population for at least 60 days, and in combination with uninfected cohorts (n = 16) were used in a double-blind study design. Sensitivity and specificity of the tests depended on the choice of positive-negative thresholds expressed as percent positivity with respect to the median OD of four replicates of the strong positive reference serum provided with the kit. In general, while overall specificities were high, sensitivities of the antigen-ELISAs were poor. For example, at a cut-off of 5% positivity, the sensitivities of the antigen-ELISAs were 11% for samples (n = 1162) from T. congolense infected cattle (n = 30), and 24% for samples (n = 283) from T. vivax infected cattle (n = 10). The corresponding specificity values were 95% and 79%, respectively. At a cut-off of 2.5% positivity sensitivity for T. congolense was 25%, and for T. vivax 35%; corresponding specificity values were 85% and 63% respectively. There were no values of the positive-negative threshold at which both sensitivity and specificity were satisfactory. Restricting the analyses to samples taken more than 2 weeks after tsetse challenge did little to improve sensitivity estimates. Trypanosome species specificities of the antigen-ELISAs were also poor. Sensitivity and species specificity of the antigen-ELISA for Trypanosoma brucei infections were not investigated. In contrast to the antigen-ELISA, the sensitivity of the buffy-coat technique when applied to the same experimental animals was fairly high at 67% for T. congolense infections and 60% for T. vivax infections. For samples taken more than 2 weeks after tsetse challenge, high sensitivity estimates of 96% for T. congolense and 76% for T. vivax infections were obtained.     

The non-structural polyprotein 3ABC of foot-and-mouth disease virus as a diagnostic antigen in ELISA to differentiate infected from vaccinated cattle

A diagnostic assay to differentiate antibodies induced by foot-and-mouth disease virus (FMDV) infection from those induced by vaccination was developed. The test is an indirect-trapping ELISA which uses a monoclonal antibody to trap the non-structural 3ABC-FMDV polypeptide expressed in E. coli. Experimental and field sera from naive, vaccinated and infected cattle were examined. Using the established threshold of 0.20 optical density units, the sensitivity of the assay was 100%, as all the experimental post-infection sera (n degree = 137) gave values greater than this threshold, irrespective of the FMDV serotype used for the infection. In contrast, more than 99% of sera from vaccinated animals were negative (225 out of 228 primo-vaccinates and 159 out of 159 multi-vaccinates). A high degree of specificity was also confirmed by the finding that 99.5% (442 out of 444) of sera from naive animals gave negative results. Serum conversion against 3ABC was first detected 8 days post-infection and demonstrable levels of 3ABC specific antibodies were detectable at least 1 year post-infection. The described 3ABC-ELISA is safe, cheap and also easy to perform in large scale serological surveys. The high specificity and sensitivity makes this test an ideal tool for FMD eradication campaigns and control programs.     

Rapid detection of a Schistosoma mansoni circulating antigen excreted in urine of infected individuals by using a monoclonal antibody

Schistosoma circulating antigens were used to indicate the infection intensity and to assess cure. An immunoglobulin G2a (IgG2a) mouse monoclonal antibody was used in a fast dot-enzyme-linked immunosorbent assay (ELISA; FDA) for rapid and simple diagnosis of schistosomiasis in the field. Seven hundred Egyptians were parasitologically examined for Schistosoma mansoni and other parasitic infections. A rectal biopsy was done as a "gold standard" for individuals showing no S. mansoni eggs in their feces. Egg counts were obtained by the Kato smear method for only 100 of 152 individuals with eggs in their feces. Specific anti-schistosome IgG antibodies were evaluated in sera by ELISA. Urine samples from the 700 individuals were tested by FDA for detection of the circulating antigen. The assay showed a sensitivity of 93% among 433 infected individuals and a specificity of 89% among 267 noninfected individuals. FDA showed the highest efficiency of antigen detection (91%) compared with the efficiency of antibody detection by ELISA (75%) and stool analysis (60%). In addition, FDA detected infected patients with 20 eggs/g of feces. Also, the sensitivity of FDA ranged from 90 to 94% among samples from patients with different clinical stages of schistosomiasis. All the assay steps can be completed within 30 min at room temperature for 96 urine samples. The monoclonal antibody identified a 74-kDa antigen in different antigenic extracts of S. mansoni and Schistosoma haematobium and in the urine of infected individuals. In addition, a 30-kDa degradation product was identified only in the urine samples. On the basis of these results, FDA should be used as a rapid tool for the sensitive and specific diagnosis of Schistosoma infection.     

An enzyme-linked immunosorbent assay (ELISA) for serological diagnosis of Neospora sp. infection in cattle

A kinetic enzyme-linked immunosorbent assay (ELISA) was developed and optimized for detection of antibodies to Neospora sp. in cattle. Sonicated tachyzoites of Neospora sp. isolated from an aborted bovine fetus were used as antigen. Variability in immunoblot patterns among positive sera, and the fact that all life stages of the parasites are unknown, justified use of a multiple-antigen ELISA to allow for maximum sensitivity. Immunoblot analysis revealed negligible cross-reactions between Toxoplasma gondii antigen and Neospora sp. antisera and between Neospora sp. antigen and antisera from various apicomplexan parasites. The maximum positive-to-negative Vmax (average maximum slope of the optical density over time) ratio was obtained using 200 ng/well of sonicated tachyzoite antigen and a 1:200 serum dilution. Using logistic regression to determine the optimal cutoff point between known infected and noninfected cattle, a sample-to-positive control Vmax ratio of 0.45 was found to maximize the percent correct classification, with an estimated sensitivity of 88.6% and specificity of 96.5%. Use of Neospora caninum antigen following the same protocol demonstrated no difference in ELISA interpretation. Comparison with an existing indirect immunofluorescent antibody (IFA) test showed the ELISA to be the more sensitive and specific test for serodiagnosis of Neospora infection in cattle.     

MR imaging of the liver: comparison between single-shot echo-planar and half-Fourier rapid acquisition with relaxation enhancement sequences

We previously reported the case of a human chronic Bordetella bronchiseptica respiratory infection, due to contact with infected rabbits. Lipopolysaccharides of the human isolates, of one rabbit isolate and of isolate from other origins were analyzed with sera from infected mice, rabbit and human. Antigenicity and length of the lipopolysaccharide molecules varied between isolates. We showed a progressive loss of O-chain during infection, associated with an enhanced susceptibility of the isolates to the bactericidal effect of normal serum. This observation suggests the existence of an intracellular niche which selects for strains with distinct lipopolysaccharide types.     

Two-color hybridization assay for simultaneous detection of Bordetella bronchiseptica and toxigenic Pasteurella multocida from swine

Bordetella bronchiseptica and toxigenic Pasteurella multocida are the etiologic agents of swine atrophic rhinitis. Methods currently used for their identification are time-consuming and suffer from a lack of sensitivity. We describe a colony lift-hybridization assay for detection of B. bronchiseptica and toxigenic P. multocida that can be performed with a single colony lift derived from a primary isolation plate without the need for pure subcultures of suspect bacteria. Membranes are hybridized simultaneously to probes derived from the B. bronchiseptica alcA gene and the P. multocida toxA gene. A multicolor development procedure permits sequential detection of bound probes. The assay was tested with 84 primary isolation plates generated from nasal swabs from swine with clinical signs of atrophic rhinitis. Comparison of the results from the colony lift-hybridization assay with those from conventional testing, based on a combination of colony morphology, biochemical reactions, mouse lethality, and enzyme-linked immunosorbent assay, indicated that the colony lift assay has superior sensitivity and comparable specificity. This technique has wide application for diagnostic and experimental studies.     

Combinations of three immunological assays for detecting anti-Toxoplasma IgG in the sera of patients infected with Toxoplasma gondii

Enzyme-linked immunosorbent assay (ELISA), Dot-ELISA and Dot-immunogold silver staining (Dot-IGSS) were simultaneously used to detect the specific IgG against Toxoplasma gondii in 65 patients infected with the protozoa. The positive rates were 86.51%, 92.51% and 98.64%, respectively. When ELISA and Dot-ELISA results were put together, the positive rate increased to 95.38%. When Dot-IGSS results were combined with those of ELISA or Dot-ELISA, the positive rate was raised to 100%. The difference in positive rate between ELISA and Dot-IGSS was significant (x2 = 6.93, p < 0.01), but no statistically significant differences were found between ELISA and Dot-ELISA or between Dot-ELISA and Dot-IGSS. Paired comparison of the reacting intensities of the sera in the 3 assays showed the correlations were highly significant (p < 0.001), with r = 0.608 between Dot-IGSS and Dot-ELISA, r = 0.8194 between Dot-IGSS and ELISA and r = 0.517 between Dot-ELISA and ELISA. Hence combination of different serological assays may increase their sensitivity and specificity for detecting the anti-Toxoplasma antibodies.     

Evaluation of an ultramicroELISA system for the diagnosis of rubella

An indirect Ultramicro ELISA assay, previously standardized in our laboratory, for detecting antibodies IgG to the rubella virus was assessed in comparison to the hemagglutination inhibition technique. This assessment allowed to determine its efficacy in the National System for Epidemiological Surveillance of this entity. One hundred and ninety serum pairs of clinically suspected cases of rubella were studied and a high percent of coincidence (99.4%), specificity (99.4%), and sensitivity (100%) was found between both techniques. In addition, 73 serum samples of blood donors were processed using an indirect microELISA system (Berhing) which was compared to the Ultramicro ELISA technique for rubella and it showed a 100% of sensitivity, specificity, and coincidence.     

Health-care technology transfer: expert and information systems for developing countries

The alkaline phosphatase immunoassay (APIA) is an antibody detection technique which permits the diagnosis of schistosomiasis using a butanolic extract preparation from adult worms. APIA has demonstrated high sensitivity and specificity in previous reports with well characterized human sera. Its potential as a diagnostic tool for epidemiological surveillance was assessed in comparison with three other diagnostic tests: stool examination, ELISA with soluble egg antigen (SEA) and the circumoval precipitin test (COPT). APIA was 100% specific in an area without Schistosoma mansoni transmission and had 89% sensitivity in an endemic area where 69% of the infected subjects excreted less than 100 eggs g of faeces. It was found to be less sensitive in children under 5 years of age who were positive by the COPT test. APIA can be applied as an initial screening test, based on its high sensitivity, specificity, absence of cross-reactivity with intestinal parasites and the fact that it is a technique suitable for use in epidemiological surveillance.     

Macrophages infected with bovine leukaemia virus (BLV) induce humoral response in rabbits

BLV is a lymphotropic retrovirus which infects mainly B-cells. However, the possible infection of cells of the monocyte/macrophage lineage (M/M) might explain some aspects of the disease such as latency or disease progression. We infected sheep M/M with BLV either by culturing M/M with supernatant containing virus, or coculturing M/M with persistently infected cell lines. These BLV-infected M/M were inoculated into rabbits and the serological response was followed for two years. ELISA results using adsorbed sera showed a persistent production of specific antibodies from as early as the first week post inoculation. Two tests were used to detect the response against envelope glycoprotein gp51: Agar gel immunodiffusion (AGID) and a virus neutralization test read as syncytia inhibition (SI). Sera were positive by AGID after the second or third inoculation. Neutralizing titres (SI) were higher than those seen in control rabbits inoculated with persistently infected cell lines, suggesting that the virus may be expressed better in M/M. Gag-related proteins were analyzed by Western Blot (WB). Sera from rabbits inoculated with BLV-infected M/M recognized as many viral proteins as sera from BLV immunized control rabbits or infected cows, and this profile did not change with repeated inoculations. All these results suggest that BLV may infect M/M, where viral proteins are actively expressed to the point that they induce a humoral immune response in animals, and that animals get persistently infected.     

Evaluation of an ELISA for Mycobacterium bovis infection in badgers (Meles meles)

The performance of an indirect ELISA for diagnosing Mycobacterium bovis infection in live badgers was evaluated by examining blood samples collected from 1982 badgers captured during statutory badger removal operations in south west England. The Validity of the test and the factors affecting the prevalence of infection are described. The sensitivity of the ELISA was 40.7 percent, its specificity was 94.3 percent, the predictive value of a positive test was 67.5% percent and the predictive value of a negative test was 84.6 percent. Its sensitivity was significantly higher in males and animals with gross lesions typical of tuberculosis. The sensitivity and positive predictive values were enhanced when the results were grouped by control operation. Variables of significance for prevalence were the county, the time of year, the age and sex of animal, and the time after the start of a control operation. The possible use of the ELISA as a screening test is discussed.     

Giardiasis in travellers: evaluation of an antigen-capture ELISA for the detection of Giardia lamblia-antigen in stool

Diagnosis of giardiasis relies largely on the microscopical detection of trophozoites or cysts in feces. However, this method is labour- and time-intensive and depends highly on the skill of an experienced microscopist. In order to identify the prevalence of Giardia lamblia in travellers returning from overseas, we evaluated sensitivity and specificity of a commercially available ELISA kit for the detection of Giardia-lamblia-antigen in stool. Nine hundred seventy-eight stool samples from 795 patients were examined by microscopy (iron-hematoxyilin-stain, SAF-concentration) and ELISA. Altogether, Giardia infection could be detected in 74 subjects. On evaluation of all samples, the ELISA turned out to be more sensitive than microscopy (95.5% vs. 81.8%) and 99.7% specific for Giardia lamblia. Especially with microscopy, the examination of more than one stool specimen did improve diagnostic sensitivity. It seems therefore advisable to retain the practise of examining at least three stool samples before considering a patient as not infected. The coproantigen-ELISA is especially advantageous in situations where only a single stool sample can be examined. It should not, however, replace microscopical examination of stool specimens for ova and parasites since other potential pathogens would otherwise escape detection.     

Clinical evaluation of the Serum CrossLaps One Step ELISA, a new assay measuring the serum concentration of bone-derived degradation products of type I collagen C-telopeptides

The Serum CrossLaps One Step ELISA is a sandwich assay using two monoclonal antibodies specific for a beta-aspartate form of the epitope EKAHDGGR derived from the carboxy-terminal telopeptide region of type I collagen alpha1-chain. Our objective was to assess the clinical value of the Serum CrossLaps assay for monitoring antiresorptive therapy in osteoporosis treatment. Samples obtained from postmenopausal women treated with different doses of cyclic or continuous hormone replacement therapy (HRT) with an estrogen analog (tibolone) or with a bisphosphonate (ibandronate) were measured in the Serum CrossLaps One Step ELISA at baseline and at various time points during therapy. The corresponding urine samples were measured in the urine CrossLaps ELISA and corrected for creatinine excretion. The serum CrossLaps measurements and corresponding urinary CrossLaps measurements were highly correlated (r >0.8 for all studies). The serum and urine CrossLaps measurements showed a significant decrease among the women treated with clinically relevant doses of either of the antiresorptive agents. Furthermore, the annual percentage change in bone mineral density (BMD) correlated with the measured changes in CrossLaps concentration. The serum CrossLaps assay showed a specificity of 83-100% and a sensitivity of 59-83% for assessing BMD changes. The corresponding values for the creatinine-corrected urinary measurements were 83-92% specificity and 68-79% sensitivity. We conclude that performance of the convenient Serum CrossLaps One Step ELISA is at least equivalent to that of the urine text for follow up of antiresorptive treatment in osteoporosis. Further studies are needed to optimize its use in this and other clinical applications.     

Detection of anti-Ro(SSA) antibodies in autoimmune diseases: comparison of five methods

Counterimmunoelectrophoresis (CIE), RNA precipitation, ELISA and immunoblotting against cytoplasmic HeLa cell extract (IB-HeLa) and erythrocyte extract (IB-RBC) were applied to detect anti-Ro(SSA) antibodies in 93 sera selected from patients with various autoimmune diseases [47 were anti-Ro(SSA) positive by CIE]. The RNA precipitation assay, which demonstrated the highest sensitivity was selected as the reference method. CIE was found to be reliable with a specificity of 100% and a sensitivity of 89%. ELISA showed a comparable specificity (95%) but somewhat lower sensitivity (72%). Antibodies to 52 or 60 kDa Ro(SSA) proteins by IB-HeLa demonstrated a high specificity (95 and 97% respectively) but a low overall sensitivity (36 and 17% respectively). Anti-Ro(SSA) antibodies to 52, 54 and 60 kDa erythrocyte proteins by IB-RBC, had a variable overall specificity (95, 97 and 57%) and sensitivity (51, 13 and 34%). The anti-52 kDa antibodies detected by IB-HeLa correlated to those found by IB-RBC (P < 0.001) and occurred predominantly in primary Sj?gren's syndrome (P < 0.001, sensitivity: 71 and 77%) as well as in sera with anti-Ro(SSA) and anti-La(SSB) antibodies (P < 0.001). These findings confirm that RNA precipitation assay has the highest sensitivity and specificity for anti-Ro(SSA) antibody detection. However, until a more sensitive ELISA is available, CIE because of its reliability appears to be the method of choice. Finally IB-RBC was found to be more sensitive than IB-HeLa for the detection of anti-Ro52 kDa antibodies.     

Evaluation of an enzyme immunosorbent assay for the diagnosis of Argentine haemorrhagic fever

To elaborate a set of serological tests for the diagnosis of Argentine haemorrhagic fever (AHF), an enzyme-linked immunosorbent assay (ELISA) for detection of specific anti-Junin virus (JV) IgG is described, and its performance is compared with that of the plaque reduction neutralization test (PRNT). The reproducibility, sensitivity, specificity, and confidence limits for positive and negative results for ELISA were statistically analysed. The value of 800 was demonstrated as the lowest positive titer. Titers > or = 800 varied within one (two-fold) dilution in 95.6% of the tests, while the sensitivity and specificity were 99.2% and 98.8%, respectively. The assay yielded 1% of false positives and 0.05% of false negatives. A comparison of ELISA to PRNT in detecting the seroconversion for JV was studied by the chi square test (comparison of proportions in paired samples) and the K parameter for agreement proportion. Comparison of ELISA to PRNT showed no significant difference in the proportions of positive and negative results of these assays (P < 0.01), demonstrating an equivalent performance (K = 0.98) in the diagnosis of AHF. In addition, the simplicity and safety of the procedures involved make this ELISA the most suitable test to detect natural human JV infections.