Clinical and serologic studies of canine borreliosis

During 1984 and 1985, blood samples were obtained from 271 dogs that were suspected of having borreliosis. The dogs lived in areas known to be infested with ticks and had been examined because of limb/joint disorders or for unknown illnesses marked by fever, anorexia, or fatigue. Lameness had been the most frequently reported clinical manifestation. Analyses of serum specimens, by an indirect fluorescent antibody (IFA) method or by an ELISA, detected antibodies to Borrelia burgdorferi, the etiologic agent of borreliosis in dogs and of Lyme disease in human beings. Antibody to B burgdorferi was detected in 76.3% of 114 specimens from dogs living in the lower Hudson Valley region of New York State (predominantly Westchester County), in 66.5% of 155 specimens from dogs from southern Connecticut, and in single specimens from dogs from Rhode Island and California. Geometric mean antibody titers peaked during the winter. Results of IFA tests and ELISA were in agreement, but the latter method yielded less variable results, had greater sensitivity, and was more easily standardized. Five dogs from New York State and Connecticut seropositive to B burgdorferi had developed kidney disorders during or after episodes of intermittent lameness. Application of murine monoclonal antibody in an IFA procedure verified the presence of B burgdorferi in renal cortical tissues from one dog.     

Retrospective serologic survey for the presence of feline immunodeficiency virus antibody: a comparison of ELISA and IFA techniques.

A total of 878 samples from the New York State Diagnostic Laboratory (NYSDL), dating from January 1984 to May 1987, were examined to detect antibodies to feline immunodeficiency virus (FIV). We used 2 screening methods; an indirect immunofluorescence assay (IFA) and an enzyme-linked immunosorbent assay (ELISA). Of these, 211 samples were from cats that tested negative for feline leukemia virus (FeLV) and exhibited disease signs consistent with immunodeficiency disease; 19 (9.0%) serum samples were determined to be positive. An additional 508 samples were from cats that tested FeLV-negative and were asymptomatic; 6 (1.2%) sera were determined to be positive. The final 159 samples were from FeLV-positive cats and included symptomatic and asymptomatic animals; this population of cats produced 6 (3.8%) positives. Additionally, 521 samples from the Cornell Feline Health Center (CFHC) serum bank, dating back to 1966, were tested to determine the earliest sample in which FIV antibodies could be detected. Five (2.7%) 1971 and 3 (3.3%) 1969 CFHC samples tested positive. The IFA for FIV antibody proved to be a sensitive (97.4%) and specific (100%) test. The ELISA also had high sensitivity (100%) and specificity (99.6%); however, the IFA proved to be more specific than the ELISA when assaying FeLV-positive cats.     

Seroprevalence of tularemia in wild bears and hares in Japan

Tularemia is a zoonotic disease caused by Francisella tularensis. The distribution of the pathogen in Japan has not been studied well. In this study, seroprevalence of tularemia among wild black bears and hares in Japan was determined. Blood samples collected from 431 Japanese black bears (Ursus thibetanus japonicus) and 293 Japanese hares (Lepus brachurus) between 1998 and 2009 were examined for antibodies against F. tularensis by micro-agglutination test (MA) or enzyme-linked immunosorbent assay. By subsequent confirmatory tests using western blot (WB) and indirect immunofluorescence assay (IFA), eight sera from Japanese black bears were definitely shown to be seropositive. All of these eight bears were residents of the northeastern part of main-island of Japan, where human tularemia had been reported. On the other hand, no seropositive Japanese hares were found. These results suggest that Japanese black bears can serve as sentinel for tularemia surveillance and may help understand the distribution of F. tularensis throughout the country. This is the first report on detection of antibody to F. tularensis in black bears of Japan.     

Detection of antibodies to Borrelia burgdorferi in naturally infected horses in the USA by enzyme-linked immunosorbent assay using whole-cell and recombinant antigens

Blood samples were collected from 98 horses suspected of having borreliosis or granulocytic ehrlichiosis in Connecticut and New York State, USA during 1985, 1995, and 1996. Serum antibodies to Borrelia burgdorferi were detected by an enzyme-linked immunosorbent assay (ELISA), based on whole-cell and recombinant antigens, in 82 (84%) horses. Of the 181 sera tested, 59% were positive, using whole-cell antigens, compared to 48% with protein (p)37 and 35% with VlsE antigens. An ELISA containing either of these fusion proteins can be used as an adjunct to general screening by an ELISA or immunoblotting in animals not vaccinated for this disease.     

Sensitivity, specificity, and predictive values of ClinEase-Virastat saliva test for feline leukemia virus infection

Detection of virus in saliva using a commercial enzyme-linked immunosorbent assay (ELISA), ClinEase-VirastatR, was compared to evidence of FeLV infection by the indirect immunofluorescent antibody assay (IFA) and plasma ELISA. The sensitivity and specificity of the saliva ELISA were derived by comparison to IFA and plasma ELISA in 103 cats from a large colony in New York State. The sensitivity of the saliva test in relation to IFA and plasma ELISA was approximately 100% and 93%, respectively. The specificity of the saliva ELISA in relation to IFA and plasma ELISA was approximately 85% and 92%, respectively. This test appears to be particularly suitable as a screening test for FeLV infection, especially in populations where the expected prevalence is low. Because of its high sensitivity, the saliva test has a high negative predictive value, particularly in populations where the disease is rare. Since the specificity is moderate, however, the predictive value of a positive test will be poorest in cats originating from places where the infection is rare (e.g. single cat households, or free roaming cats), and better among cats from environments having a high prevalence of FeLV (e.g. multiple-cat households).     

Comparison and interpretation of diagnostic tests for feline immunodeficiency virus infection.

Feline sera were submitted to the Cornell Feline Health Center (n = 497) or to the New York State Diagnostic Laboratory (n = 1,565) for feline immunodeficiency virus (FIV) testing. Some sera (n = 166) were submitted for confirmation of previous FIV-positive results; 151 of these sera had been tested at the referring veterinary practice or laboratory, using an in-house ELISA. Excluding the samples submitted for confirmation, a total of 173 samples (9.1%) were FIV-positive; 11.6% of the clinically ill or high-risk cats and 0.49% of the healthy, low risk cats were positive for FIV antibody. A commercially available ELISA for detection of antibody to FIV was evaluated in relation to the immunofluorescent antibody (IFA) test and the immunoblot assay. The ELISA was interpreted according to the manufacturer's instructions, with the ratio of sample optical density to positive control optical density (S/P) determining a positive or negative result. The ELISA results based on the S/P interpretation were compared with a kinetics-based (KELA) interpretation of the ELISA. The KELA values were reported as positive, negative, or equivocal. Using the immunoblot as the standard, ELISA (S/P interpretation) had sensitivity of 0.93 and specificity of 0.98, whereas the IFA test had sensitivity of 0.95 and specificity of 0.98. However, the sensitivity and specificity of the ELISA (S/P interpretation) were markedly reduced for sample results falling in the KELA equivocal range, indicating that equivocal results were valid interpretations for some sera. A high number (22.5%) of the samples submitted for confirmation of a positive result from use of the in-house ELISA were determined to be negative for FIV antibody.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of serologic and viral detection methods for diagnosing feline herpesvirus-1 infection in cats with acute respiratory tract or chronic ocular disease

OBJECTIVE: To determine the value of virus isolation (VI), immunofluorescent antibody (IFA) assay, serum neutralization (SN), and ELISA for the diagnosis of clinical feline herpesvirus-1 (FHV-1) infection in cats. ANIMALS: 46 clinically normal cats, 17 cats with signs of acute respiratory tract disease, and 38 cats with signs of chronic ocular disease. PROCEDURE: Conjunctival swabs for VI, conjunctival scrapings for IFA testing, and venous blood samples for SN or ELISA testing were obtained from all cats. RESULTS: FHV-1 was detected in 10.9 and 28.3% of clinically normal cats and in 18.2 and 33.3% of cats with FHV-1-associated disease by VI and the IFA assay, respectively. There were no significant differences in the viral detection rate between cats with acute respiratory tract disease and cats with chronic ocular disease or between diseased cats and clinically normal cats; however, FHV-1 was never detected by both methods in clinically normal cats. Overall FHV-1 seroprevalence was 97% when tested by ELISA and 66% when tested by SN. Seroprevalence did not vary significantly among the 3 groups for either serologic test. Magnitude of SN and ELISA titers varied greatly but independently of presence or absence of clinical signs of FHV-1-associated disease. Sensitivity, specificity, and positive and negative predictive values were assessed for VI and the IFA assay--jointly and individually--and for each SN and ELISA titer magnitude. Values never all exceeded 50%. CLINICAL IMPLICATIONS: Because FHV-1 can be detected commonly in clinically normal cats by the IFA assay or VI, neither test appears to aid in the clinical diagnosis of FHV-1 infection. Seroprevalence does not appear to vary between affected and clinically normal cats. SN, ELISA, VI, and the IFA assay appear to be of limited value in the diagnosis of FHV-1-associated disease in cats. Concurrent assessment of the IFA assay and VI results may permit exclusion of FHV-1 as an etiologic agent if results of both tests are negative.     

A comparison of serologic tests for the detection of serum antibodies to whole-cell and recombinant Borrelia burgdorferi antigens in cattle

Serum samples from healthy dairy and beef cattle, living in tick-infested areas of Connecticut, USA, were analyzed by polyvalent enzyme-linked immunosorbent assays (ELISA), indirect fluorescent antibody (IFA) staining methods, or Western blot procedures to detect antibodies to tick-borne agents. Of the 80 sera tested by ELISA with whole-cell or 10 separate recombinant antigens (fusion proteins) of Borrelia burgdorferi sensu stricto, 57 (71%) were positive to 1 or more antigens, while 36 (45%) reacted to whole-cell antigens by IFA staining methods. Three (4%) of 80 samples had antibodies to Anaplasma phagocytophilum. There were antibodies to outer surface protein (Osp) A, OspB, OspC, OspE, OspF, protein (p) 41-G, p35, p37, and VlsE antigens of B. burgdorferi, but there was no reactivity to the p39 antigen by ELISA. Western immunoblots of a subset of 9 sera verified antibody presence in all samples and showed distinct reactivities to multiple proteins having molecular masses of about 31 kilodaltons (kDa), 34 kDa, 35 kDa, 41 kDa, and 83/93 kDa. High specificity (97%) was noted when 16 cattle sera containing antibodies to Leptospira interrogans serovars, Brucella sp., Anaplasma marginale, or A. phagocytophilum were tested by ELISA with separate whole-cell or recombinant B. burgdorferi antigens. An ELISA and Western blot analyses can be used to confirm the exposure of cattle to B. burgdorferi.     

Seroprevalence of antibodies against Borrelia burgdorferi and Anaplasma phagocytophilum in cats

OBJECTIVE: To determine whether cats in the northeastern United States develop serum antibodies against antigens of Borrelia burgdorferi and Anaplasma phagocytophilum and whether coinfection with the 2 organisms occurs. SAMPLE POPULATION: Serum samples from 84 healthy cats and 9 cats with lameness, fever, anorexia, or fatigue. PROCEDURE: Serum antibodies against B. burgdorferi and A. phagocytophilum were measured with an ELISA incorporating a whole-cell preparation or purified recombinant antigens, by means of Western blot analysis, or indirect fluorescent antibody (IFA) staining. RESULTS: ELISA results indicated that 44 of 93 (47%) sera contained antibodies against > or = 3 B. burgdorferi antigens, whereas 43 (46%) were reactive to whole-cell B. burgdorferi. Serum reactivity to protein 35, VlsE, and outer surface proteins A and F was most common. Seropositivity to > or = 3 antigens occurred at the same rate (5/9) in the 9 ill cats as in the 84 healthy cats (46% [39/84]). Of 13 sera reactive to recombinant antigens, 9 were seropositive as measured by Western blot testing with whole-cell antigen. Seropositivity rates of 30% and 38% were detected for antibodies against A phagocytophilum via IFA and ELISA testing, respectively. Fifteen (16%) sera had antibodies against both pathogens. CONCLUSIONS AND CLINICAL RELEVANCE: Cats living in areas infested by Ixodes scapularis ticks are exposed to B. burgdorferi and A. phagocytophilum and, in some instances, may be coinfected. Most cats appeared healthy. An ELISA incorporating specific recombinant antigens may be used adjunctively with Western blot and other assays to confirm B. burgdorferi and A. phagocytophilum infection in cats.     

Evaluation of an ELISA rapid device for the serological diagnosis of Leishmania infantum infection in dog as compared with immunofluorescence assay and Western blot

In this study we compared a commercial enzyme linked immunosorbent assay (ELISA) rapid test (Snap CLATK Canine Leishmania Antibody Test Kit, IDEXX-Snap) with indirect immunofluorescence assay (IFA) and Western blot (WB) for the detection of Leishmania infantum antibodies in dogs. In total sera from 234 dogs were collected: 59 positives and 51 doubtful sera (IFA 1:40-1:80) from an L. infantum endemic area and 124 negative sera from a non-endemic area were tested. To evaluate the Snap CLATK's performances on whole blood, blood in EDTA and sera from 37 dogs were tested in parallel with Snap CLATK. Snap CLATK sensitivity and specificity compared to IFA were 91.1% and 99.2%, while compared to WB were 93.4% and 98.3%, respectively. When IFA doubtful sera (titers of 1:40 or 1:80) were tested Snap CLATK, using WB as reference, sensitivity and specificity were 90.9% and 100%, respectively. Moreover, a complete concordance was observed when Snap CLATK rapid assay was carried out on whole blood or sera from 37 dogs. The Snap CLATK has demonstrated simplicity and performance and can be considered a quick and reliable alternative for the diagnosis of L. infantum infection in dogs.     

Bartonella henselae IgG antibodies are prevalent in dogs from southeastern USA

In contrast to the large body of literature regarding Bartonella henselae in humans and cats, there is little information about B. henselae as an infectious agent in dogs. Due to the paucity of information regarding the B. henselae serology in dogs, we performed a cross-sectional serosurvey using B. henselae antigen in order to compare the seroprevalence between sick and healthy dogs from the south-eastern USA. Ninety-nine sera were collected from clinically healthy dogs. Three hundred and one sera from sick dogs were submitted to North Carolina State University for serologic screening against a panel of arthropod-transmitted organisms. Serological tests were performed using B. henselae (Bh), Rickettsia rickettsii (Rr), Ehrlichia canis (Ec), Bartonella vinsonii subspecies berkhoffii (Bvb), Babesia canis (Bc) and Borrelia burgdorferi (Bb) antigens. Serum B. henselae IgG antibodies were detected in 10.1% of healthy dogs and in 27.2% of sick dogs. The difference in seroprevalence between the two groups was statistically significant. The majority of seroreactive dogs (80%) had low titers of 1:64 or 1:128. In healthy dogs, seroprevalence for Rr was 14.1% and for Bvb was 1%. In sick dogs, Rr seroprevalence was 29.7%, Ec 6.5%, Bvb 4.7%, Bb 1.7% and Bc was 0.85%. Of the sick dogs that were seroreactive to B. henselae antigens, 40.6% were also seroreactive to Rr, 15.0% reactive to Bvb antigens, 14.8% reactive to Ec antigens, 1.8% reactive to Bc antigens and 1.75% reactive to Bb antigens. Sera from dogs experimentally infected with B. vinsonii subsp. berkhoffii, E. canis or R. rickettsii did not cross react with B. henselae antigens, by IFA testing. This study indicates that B. henselae IgG antibodies are prevalent in healthy and sick dogs living in the south-eastern USA. Nevertheless, further studies are needed to evaluate the epidemiological, clinical and zoonotic relevance of B. henselae infection in dogs.     

Serological evidence of Ehrlichia spp. exposure in cats from northeastern Spain

There is little information about Ehrlichia canis as an infectious agent in cats. In order to estimate the prevalence of antibodies to E. canis in the feline population, 235 cat sera were analysed by indirect fluorescent-antibody test. With the objective to determine some risk factors associated with seropositivity, serum samples were divided into two groups: urban stray cats and pet cats. The seroprevalence detected was 17.9%. Most positive sera (83.3%) showed low antibody titres (<1:80). Seropositivity was very similar when comparing the two groups of animals: 17.4% in urban stray cats and 18.4% in pet cats. Results revealed that cats are exposed to Ehrlichia spp. infection, as the low antibody titres detected and the serological cross-reactivity between Ehrlichia species do not allow us to confirm E. canis exposure.     

Prevalence of neutralizing antibody to the calf rotavirus in New York cattle.

In March 1973, a modified live virus vaccine was released for sale in the United States for the protection of neonatal calves from infection with calf rotavirus. At that time no published evidence existed that this agent was present in New York or the New England states. Serum neutralizing antibodies for the calf rotavirus (reovirus-like agent of neonatal calf diarrhea) were detected in serum from 108 of 110 dairy cattle in New York State representing 78 different herds. To exclude the possibility that the demonstrated serologic response may have been stimulated by vaccine virus, 36 samples were included that had been collected prior to the date of vaccine release. Neutralizing antibodies were demonstrated in 108 of the 110 sera ranging from titers of 4 to greater than 1024, thereby offering indirect evidence of the ubiquitous nature of calf rotavirus in New York.     

IDENTIFYING REMOVABLE RADIOACTIVITY ON THE SURFACE OF CATS DURING THE FIRST WEEK AFTER TREATMENT WITH IODINE 131

Because radioiodine (1-131) is excreted in urine and saliva, treated cats can accumulate I-131 on their coats from contacting soiled litter and grooming. This could result in removable radioactivity, which is a potential source of human exposure to radiation and specifically to internal contamination. The purpose of this study was to determine if there is removable radioactivity on cats treated with I-131. Daily wipe tests were performed for 7 days at two sites (both flanks, one site; and all four paws, one site) on six hyperthyroid cats treated with I-131. A y counter was used to determine the counts per minute (cpm) of the samples, which were converted to disintegrations per minute (dpm) to estimate activity. The results were compared to the New York State limits of removable activity for a non-controlled area (<1000dpm/100 cm2) to determine if the amount of removable activity was acceptable for a member of the public. The median value of removable activity was 241 dpm (range from 34 to 4184 dpm) for the flanks, and 308 dpm (range from 60 to 1890 dpm) for the paws. The amount of removable radioactivity on the surface of hospitalized cats treated with I-131 during the first week after treatment, occasionally and without obvious pattern, exceeded the New York State limit. Sporadic activity as high as 4148 dpm was found. It is prudent to advise owners to observe routine hygiene when handling cats after discharge to minimize the risk of internal contamination.     

Using CF0218-ELISA to distinguish Chlamydophila felis-infected cats from vaccinated and uninfected domestic cats

Chlamydophila felis is a causative agent of acute and chronic conjunctivitis and pneumonia in cats. Cats can be vaccinated with killed or attenuated C. felis. However, current serodiagnostics cannot distinguish these cats from naturally infected cats. This causes difficulty of early diagnosis and seroepidemiological survey for C. felis. We previously reported that C. felis CF0218 can be used as a C. felis-infection-specific diagnostic antigen in experimentally infected and/or vaccinated cats. In this study, we evaluated an enzyme-linked immunosorbent assay using recombinant CF0218 as antigen (CF0218-ELISA) to detect anti-C. felis antibody in 714 sera of domestic cats whose histories of vaccination against C. felis are known. The 44 vaccinated cats were 93% negative using CF0218-ELISA; half of these scored positive by immunofluorescence assay (IFA) using C. felis-infected cells as antigen. The 670 non-vaccinated cats had CF0218-ELISA positivity rates that were statistically in agreement with IFA (18% vs. 21%). These results show that CF0218, which was identified as a C. felis-infection-specific antigen, is a useful serodiagnostic antigen to distinguish naturally C. felis-infected cats from vaccinated and non-infected cats.     

Coronavirus antibody detection in cats by computer-assisted kinetics-based enzyme-linked immunosorbent assay (KELA): field studies

A total of 2238 feline serum samples submitted to the New York State Diagnostic Laboratory over a 1-year period were tested for the presence of coronavirus antibodies, using the computer-assisted, kinetics-based enzyme-linked immunosorbent assay (KELA). Cats from which sera were obtained were categorized by sex, age, breed, and disease status, and variations in mean antibody titers for different sub-classifications within each category were analyzed by computerized statistical analysis. As expected, higher mean antibody titers were recorded for cats with feline infectious peritonitis, and for cats with a recent history of possible coronavirus exposure. However, an unexpected inverse relationship between coronavirus antibody titer and age was also found. Certain cattery-oriented pure breeds appeared to have higher mean antibody titers, because their sample populations contained a higher percentage of younger cats and cats of unknown age-groups which, over-all, had higher mean titers. Taken together, the data substantiated the efficacy of the computer-assisted KELA for routine detection of serum coronavirus antibodies in cats.     

Clinical evaluation of cats with lower urinary tract disease.

In a prospective study, 141 cats with hematuria, dysuria, urethral obstruction, or combinations of these signs were evaluated by contemporary diagnostic methods and compared with 26 clinically normal cats (controls). Specific diagnosis was established in 45% (64/141) of cats affected with lower urinary tract disease (LUTD). Crystalline matrix plug-induced urethral obstruction was diagnosed in 21% (30/141) of affected cats, uroliths were identified in 21% (30/141) of affected cats, uroliths with concomitant bacterial urinary tract infection (UTI) were identified in less than 2% (2/141) of affected cats, and bacterial UTI alone was identified in less than 2% (2/141) of cats with LUTD. Viruses, mycoplasmas, and ureaplasmas were not isolated from urine samples collected from affected or control cats. Bovine herpesvirus 4 (BHV-4)-neutralizing antibodies were not detected in any serum sample obtained from cats with LUTD or from control cats. In contrast, BHV-4 antibodies were detected by an indirect immunofluorescent antibody (IFA) test in sera obtained from 31% (44/141) of cats with LUTD and 23% (6/26) of control cats. The prevalence of positive BHV-4 IFA test results in affected cats was not significantly different from that observed in control cats. Significant association was not apparent between positive BHV-4 IFA test results and clinical diagnosis, abnormal laboratory findings, or cat age. However, the number of male cats with BHV-4 IFA titer was significantly (P less than 0.02, chi 2 test) greater than that of female cats. Detection of BHV-4 antibodies in approximately 30% of affected and control cats indicates prior virus exposure. Further investigations are warranted to clarify the specific role of BHV-4 in cats with naturally acquired LUTD.     

Evaluation of an in-practice test for feline coronavirus antibodies

A commercially available in-practice test for feline coronavirus (FCoV) antibodies (FCoV Immunocomb, Biogal Galed Laboratories) was evaluated by comparison with the gold standard FCoV immunofluorescent antibody (IFA) test. One hundred and three serum or plasma samples were selected and tested: 70 were positive by both tests, 24 were negative by both tests. The in-practice test produced five false positive and four false negative results. The sensitivity of the in-practice test was 95% and the specificity was 83%. When the titres were compared it was found that the in-practice test results were significantly correlated with IFA titres but the degree of correlation was not likely to be clinically useful. The IFA titres of the four false negative samples were found to be low (less than 40) which suggests that even a cat with a false negative result is still unlikely to be excreting FCoV. A negative result with the in-practice assay is likely to be reliable for screening cats prior to entry into an FCoV-free cattery or stud. It would also be useful in the investigation of suspected FIP as most cats with this condition have high IFA titres of antibodies. A strong positive result would be useful in the diagnosis of FIP (in conjunction with other biochemical and cytological testing), but positive results would be of limited value in monitoring FCoV infection in healthy cats as the antibody titre could not be reliably compared with those obtained with IFA. All positive results obtained using the in-practice kit should be confirmed and titrated by IFA. The kit also appeared to work efficiently with ascites samples (n=6) but too few samples were analysed to draw firm conclusions.     

Reactivity of serum samples of dogs and horses tested by use of class-specific recombinant-based enzyme-linked immunosorbent assays for detection of granulocytic ehrlichiosis

OBJECTIVE: To test serum samples of dogs and horses by use of class-specific recombinant-based ELISA for establishing a diagnosis of granulocytic ehrlichiosis attributable to infection with organisms from the Ehrlichia phagocytophila genogroup. SAMPLE POPULATION: Serum samples from 43 client-owned dogs and 131 horses (81 with signs of acute illness and 50 without signs of disease). PROCEDURE: Serum samples were analyzed, using ELISA with a recombinant 44-kd protein antigen for IgM and IgG antibodies to the human granulocytic ehrlichiosis (HGE) agent (NCH-1 strain). Western blot analyses, using infected human promyelocytic leukemia cells, were conducted on 38 serum samples of horses and 11 serum samples of dogs to verify reactivity to the 44-kd peptide. RESULTS: IgM or IgG antibodies to the HGE agent were detected in 5 to 28% of dog serum samples and 5 to 37% of horse serum samples. Thirty-five of 38 (92%) horse serum samples had corresponding results on both tests (2 positive results for 26 samples and 2 negative results for 9 samples), using an ELISA for IgG antibodies or immunoblotting for total immunoglobulins. All 11 serum samples of dogs had positive results for both methods. CONCLUSION AND CLINICAL RELEVANCE: These ELISA with recombinant 44-kd antigen are suitable for detecting IgM or IgG antibodies to the HGE agent in serum samples of dogs and horses. Positive results for serum samples of horses from Connecticut, New York, Virginia, and Georgia indicate that the HGE agent is widely distributed in tick-infested areas of the eastern United States.     

Evaluation of alternative methods for the detection of bovine leukaemia virus in cattle

AIM: To evaluate commercially available enzyme-linked immunosorbent assays (ELISAs) and the polymerase chain reaction (PCR) for their ability to detect antibodies against or nucleic acid of the bovine leukaemia virus (BLV), the causal agent of enzootic bovine leukosis (EBL), and to assess their usefulness in a national eradication programme. METHODS: Eighty-two well-defined sera (including 18 from an OIE reference laboratory) and 399 field sera from New Zealand cattle were tested in five ELISAs and the results compared with the agar gel immunodiffusion (AGID) test and electrophoretic immunoblotting (EIB) results. A polymerase chain reaction-based technique, which could detect BLV-RNA and proviral-DNA, was also evaluated on a subsample of the field cases. RESULTS: Two commercial ELISAs classified 99% of the defined sera correctly, with the other three ranging in their correct classification between 88% and 95%. The ELISAs agreed in their general classification on the majority of the 399 blood samples (91.7%), and with the AGID for more than 95 % of the sera. In a dilution series of the international reference serum E4, the highest dilution with a positive (or suspicious) result ranged from 1:80 to 1:5120. A dilution series of 202 field positive samples tested in the preferred ELISA detected 98% of positive sera at a 15 and 1: 10 dilution, reducing to 78% at a 1:80 dilution of the sera. Agreement between serological tests and PCR was poor, mainly due to failure of the PCR to detect a number of serologically positive animals. CONCLUSION: ELISA tests detected about 10% more reactors than the AGID and the EIB combined. Some ELISA-positive animals were not detected by PCR, raising doubts about the usefulness of PCR-based technology in EBL eradication programmes.