Evaluation of Anaplasma spp. seroprevalence in dogs and association with incidence of human anaplasmosis

Point-of-care (POC) ELISA tests are routinely used in US veterinary practices to screen canine patients for antibodies to tick-transmitted pathogens. Results are also used to monitor spatial and temporal trends in canine seroprevalence, and these data can build awareness of the risk to humans of tick-transmitted diseases such as Lyme disease and anaplasmosis. This study utilized a second-generation test that has incorporated additional Anaplasma-specific peptides into a commercial POC ELISA test to allow detection of Anaplasma spp. antibodies earlier post-infection. A convenience population consisting of 19,894 canine samples from a US commercial diagnostic laboratory were tested using the second-generation POC ELISA test to describe regional Anaplasma spp. canine seroprevalence and assess correlation to anaplasmosis cases reported to Centers for Disease Control and Prevention by state. Antibodies to Anaplasma spp. were detected in 1646 samples (8.3%) with the Northeast and Midwest US census regions having the highest proportion of positive samples. At the state level, a significant correlation was found between canine Anaplasma spp. seroprevalence and human anaplasmosis incidence (r2 = 0.64). Although estimates of canine Anaplasma spp. seroprevalence presented here using the second-generation POC ELISA are generally increased, especially in the Northeast and Midwest, the regional distribution of canine samples testing positive for Anaplasma spp. antibodies is consistent with previous reports. The observed correlation with human anaplasmosis incidence indicates that results from the second-generation POC ELISA will continue to add value in epidemiological assessment of human anaplasmosis risk.

Analytical validation of an ELISA for the measurement of feline pancreas-specific lipase and re-evaluation of the reference interval and decision threshold for diagnosing pancreatitis

BACKGROUND

The diagnosis of feline pancreatitis can be challenging. The clinical presentation often includes mild, nonspecific clinical signs, such as vomiting, anorexia, and weight loss. Measurement of feline pancreatic lipase immunoreactivity (fPLI) concentration in serum has been reported to be sensitive and specific for a diagnosis of pancreatitis in cats. However, analytical validation for a widely available commercial assay for the measurement of fPLI concentration has not been published.

OBJECTIVE

We aimed to analytically validate the Spec fPL assay (IDEXX Laboratories, Westbrook, ME), a commercial ELISA for the measurement of fPLI concentration, and re-evaluate its reference interval and decision threshold for diagnosing pancreatitis in cats.

METHODS

Dilutional linearity, accuracy, precision, and the effect of interfering substances were assessed. The upper limit of the reference interval was calculated based on the 95th percentile of results from clinically healthy cats (n = 107), and a decision threshold for diagnosing pancreatitis was calculated with an expected specificity of 99%.

RESULTS

Analytical validation demonstrated good linearity, accuracy, and precision, as well as the absence of interference from lipemia, hemolysis, or icterus. The upper limit of the reference interval for Spec fPL was determined to be 4.4 μg/L, and the decision threshold (a theoretical cut-off) for diagnosing pancreatitis was determined to be 8.8 μg/L based on a desired specificity of 99%.

CONCLUSIONS

The Spec fPL assay is analytically valid, and results suggest that a decision threshold of 8.8 μg/L would have high diagnostic specificity for excluding clinically healthy cats.

Measuring the Humoral Immune Response in Cats Exposed to Feline Leukaemia Virus

Retroviruses belong to an important and diverse family of RNA viruses capable of causing neoplastic disease in their hosts. Feline leukaemia virus (FeLV) is a gammaretrovirus that infects domestic and wild cats, causing immunodeficiency, cytopenia and neoplasia in progressively infected cats. The outcome of FeLV infection is influenced by the host immune response; progressively infected cats demonstrate weaker immune responses compared to regressively infected cats. In this study, humoral immune responses were examined in 180 samples collected from 123 domestic cats that had been naturally exposed to FeLV, using a novel ELISA to measure antibodies recognizing the FeLV surface unit (SU) glycoprotein in plasma samples. A correlation was demonstrated between the strength of the humoral immune response to the SU protein and the outcome of exposure. Cats with regressive infection demonstrated higher antibody responses to the SU protein compared to cats belonging to other outcome groups, and samples from cats with regressive infection contained virus neutralising antibodies. These results demonstrate that an ELISA that assesses the humoral response to FeLV SU complements the use of viral diagnostic tests to define the outcome of exposure to FeLV. Together these tests could allow the rapid identification of regressively infected cats that are unlikely to develop FeLV-related disease.

Feline Leukemia Virus p27 Antigen Concentration and Proviral DNA Load Are Associated with Survival in Naturally Infected Cats

Longitudinal studies of cats naturally infected with feline leukemia virus (FeLV) are important for understanding disease outcomes. Levels of p27 antigen and copy numbers of proviral DNA have been associated with FeLV-infection courses. The purpose of this prospective study was to establish cutoff values for p27 antigen concentration and proviral DNA load that distinguished high positive from low positive groups of cats and to evaluate an association with survival. At enrollment, 254 cats were tested by point-of-care and microtiter plate enzyme-linked immunosorbent assays (ELISAs) for p27 antigen and real-time polymerase chain reaction (PCR) for proviral DNA. The 127 positive cats were retested monthly for six months and monitored for survival over the four-year study. A receiver operating characteristic-based analysis of samples with concordant or discordant qualitative results for p27 antigen and proviral DNA was used to establish cutoff values, and when applied to test results at enrollment for classifying cats as high positive or low positive, a significant difference in survival was observed. High positive cats had a median survival of 1.37 years (95% CI 0.83-2.02) from time of enrollment, while most low positive cats were still alive (93.1% survival). Quantitative results for p27 antigen concentration and proviral DNA load were highly correlated with survival times in FeLV-infected cats.

Comparison of Anaplasma and Ehrlichia species-specific peptide ELISAs with whole organism-based immunofluorescent assays for serologic diagnosis of anaplasmosis and ehrlichiosis in dogs

OBJECTIVE

To compare the performance of 5 synthetic peptide-based ELISAs with that of 3 commercially available immunofluorescent assays (IFAs) for serologic diagnosis of anaplasmosis and ehrlichiosis in dogs.

SAMPLE

A convenience set of 109 serum samples obtained before and at various times after inoculation for 23 dogs that were experimentally infected with Anaplasma phagocytophilum, Anaplasma platys, Ehrlichia canis, Ehrlichia chaffeensis, or Ehrlichia ewingii and 1 uninfected control dog in previous studies.

PROCEDURES

All serum samples were assessed with 5 synthetic peptide-based ELISAs designed to detect antibodies against A phagocytophilum, A platys, E canis, E chaffeensis, and E ewingii and 3 whole organism-based IFAs designed to detect antibodies against A phagocytophilum, E canis, and E chaffeensis. The species-specific seroreactivity, cross-reactivity with the other tick-borne pathogens (TBPs), and diagnostic sensitivity and specificity were calculated for each assay and compared among assays.

RESULTS

All serum samples obtained from dogs experimentally infected with a TBP yielded positive results on a serologic assay specific for that pathogen. In general, sensitivity was comparable between ELISAs and IFAs and tended to increase with duration after inoculation. Compared with the IFAs, the corresponding ELISAs were highly specific and rarely cross-reacted with antibodies against other TBPs.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that peptide-based ELISAs had enhanced specificity relative to whole organism-based IFAs for detection of antibodies against Anaplasma and Ehrlichia spp, which should facilitate accurate diagnosis and may help detect dogs coinfected with multiple TBPs.

Global distribution of canine Babesia species identified by a commercial diagnostic laboratory

Babesia species are important canine pathogens with a nearly worldwide distribution. Our understanding of the distribution of these parasites is continually improving. This is in large part, due to improved molecular diagnostic capabilities. However, it can be difficult to assimilate and compare previous reports from various regions due to differences in molecular methods. In this report, we characterize the results of over 100,000 canine samples from 52 different countries and territories spanning 4 continents that were submitted to a commercial diagnostic laboratory for Babesia testing by polymerase chain reaction. The same diagnostic algorithm was used for all samples and is designed to identify and differentiate B. gibsoni, B. canis, B. vogeli, B. rossi and B. conradae. Overall 3.4% of the samples submitted tested positive for the presence of Babesia sp. DNA and were differentiated to the species level. Babesia gibsoni was the most commonly identified species (48.8% of the positive results) followed by B. canis (35.2%) then B. vogeli (15.3%). Babesia gibsoni and B. vogeli were more widely distributed than B. canis, which was primarily found in Europe. This is the largest study of its type and these data provide a global overview of which Babesia species veterinarians could expect to find in their practice area.

Comparison of Diagnostic Tools for the Detection of Dirofilaria immitis Infection in Dogs

In the last two decades, reports of canine heartworm (HW) infection have increased even in non-endemic areas, with a large variability in prevalence data due to the diagnostic strategy employed. This study evaluated the relative performance of two microtiter plate ELISA methods for the detection of HW antigen in determining the occurrence of Dirofilaria immitis in a dog population previously tested by the modified Knott's test and SNAP 4Dx Plus test. The prevalence of this infection in the sheltered dog population (n = 363) from a high-risk area for HW infection was 44.4% according to the modified Knott's test and 58.1% according to a point-of-care antigen ELISA. All serum samples were then evaluated by a microtiter plate ELISA test performed with and without immune complex dissociation (ICD). The prevalence increased from 56.5% to 79.6% following ICD, indicating a high proportion of samples with immune complexing. Comparing these results to that of the modified Knott's test, the samples negative for microfilariae (mfs) and those positive only for D. repens mfs demonstrated the greatest increase in the proportion of positive results for D. immitis by ELISA following ICD. While the ICD method is not recommended for routine screening, it may be a valuable secondary strategy for identifying HW infections in dogs.

Borrelia burgdorferi Antibody Test Results in Dogs Administered 4 Different Vaccines

Vaccines against Borrelia burgdorferi are administered frequently to dogs in areas endemic for the infection. These vaccines produce an antibody response to spirochetal proteins that cross-react in many antibody tests, including immunofluorescence assay, Western blot, and whole cell ELISA used to document exposure to B. burgdorferi. The purpose of this study was to determine whether the in-clinic C6 ELISA assay (SNAP® 4Dx® Plus; IDEXX Laboratories, Inc., Westbrook, Maine) and the quantitative format C6 ELISA (Lyme Quant C6® Antibody Test, IDEXX Laboratories, Inc., Westbrook, ME) react to sera from dogs that have been vaccinated with 1 of 4 different commercially available B. burgdorferi vaccines. Four groups of 3 dogs each were each administered one of the 4 vaccines and sera evaluated over time by indirect fluorescent antibody assay, western blot immunoassay, the in-clinic C6 ELISA assay, and the quantitative format C6 ELISA. While all dogs developed B. burgdorferi antibodies detectable by indirect fluorescent antibody assay and western blot immunoassay after vaccination, none of the samples were positive in either of the C₆ peptide-based assays. Based on these results, positive anti-C₆ antibody results in client-owned dogs are likely to reflect exposure to B. burgdorferi rather than vaccination.

Coproantigen Detection Augments Diagnosis of Common Nematode Infections in Dogs

Microscopic methods which employ active or passive flotation have been used to detect parasite diagnostic stages in the feces of companion animals for many years. More recently, coproantigen ELISAs for the detection of excretory/secretory products from intestinal nematodes have been introduced. These assays can identify the presence of parasites when eggs are not recovered by flotation (e.g. prepatent infection or intermittent egg shedding). The study was designed to assess the added benefit of these coproantigen tests in canine fecal diagnostics. The work was performed at 3 separate sites where canine fecal samples were each independently evaluated by both centrifugal flotation with an expert examiner (CFE) and passive flotation with a less experienced examiner. All samples were also tested using coproantigen ELISA to detect ascarid, hookworm, or whipworm antigen (IDEXX Laboratories, Inc, Westbrook, Maine). A total of 1202 samples were collected; 626 were from shelter dogs and 576 were from pet dogs. CFE recovered ascarid eggs in 58 samples, hookworm eggs in 229 samples, and whipworm eggs in 95 samples. Of the positive samples identified by CFE, the PFE and ELISA identified 40 and 51 ascarid samples, 188 and 203 hookworm samples, and 65 and 67 whipworm positive samples, respectively. The coproantigen ELISA identified 8 ascarid, 82 hookworm, and 22 whipworm positive samples that were not detected by CFE. The combined results of passive flotation and the coproantigen ELISA improved the percent agreement with centrifugal flotation, suggesting that greater sensitivity of detection may be achieved through the use of complementary diagnostic methods. However, errors of misidentification and poor recovery apparently introduced by less experienced examiners using an inferior flotation method remained. A diagnostic approach that combines coproantigen assays with centrifugal flotation and examination by an expert allows detection of more ascarid, hookworm, and whipworm infections.

Clinicopathological findings in 41 dogs (2008-2018) naturally infected with Ehrlichia ewingii

Background

Ehrlichia ewingii is the most seroprevalent Ehrlichia‐infecting dogs in the southern and mid‐western United States. Fever, lameness, and polyarthritis are commonly reported findings in dogs naturally infected with E. ewingii.

Objectives

To evaluate clinicopathologic findings in a population of dogs naturally infected with E. ewingii.

Animals

Forty‐one dogs PCR positive for E. ewingii and PCR negative for other targeted vector‐borne organisms.

Methods

Retrospective study. Clinical and clinicopathologic data including physical examination findings, CBC, serum biochemistry, urinalysis (UA), symmetric dimethylarginine (SDMA), and vector‐borne disease diagnostic results were reviewed.

Results

Frequent clinical diagnoses other than ehrlichiosis (28/41; 68.3%) were renal disease (7/41; 17.1%) and immune‐mediated hemolytic anemia (IMHA) (6/41; 14.6%). The most frequent physical examination finding was joint pain (14/41; 34.1%). Prominent hematologic and biochemical abnormalities included abnormal lymphocyte counts (22/36; 61.1%); neutrophilia (21/37; 56.8%); increased alkaline phosphatase (20/35; 57.1%) and alanine transaminase (14/35; 40%) activities; and increased SDMA concentration (11/34; 32.4%). Urinalysis abnormalities included proteinuria (20/27; 74%), most with inactive sediments (16/20; 80%). Dogs were seroreactive by Ehrlichia canis immunofluorescence assay (IFA; 17/39; 43.6%) and Ehrlichia ELISA (34/41; 82.9%). Seroreactivity by IFA for other vector‐borne pathogens included Bartonella (1/39; 2.6%), Rickettsia rickettsii (spotted‐fever group rickettsiae) (12/39; 30.8%), and Borrelia burgdorferi by ELISA (1/41; 2.4%).

Conclusions and Clinical Importance

Renal disease, IMHA, proteinuria, neutrophilia, abnormal lymphocytes, and increased liver enzyme activities were common in this group of E. ewingii‐infected dogs. Studies are needed to determine if E. ewingii contributes to comorbidities or is a precipitating factor in clinical syndromes in persistently infected dogs.

Canine and human infection with Borrelia burgdorferi in the New York City metropolitan area

BACKGROUND

Autochthonous transmission of Borrelia burgdorferi, the primary agent of Lyme disease in dogs and people in North America, commonly occurs in the northeastern United States, including the New York City metropolitan area, a region with a large human and pet population and broadly diverse demographics and habitats.

METHODS

We evaluated results from a specific, C6-based serologic assay performed on 234,633 canine samples to compare evidence of past or current infection with B. burgdorferi (sensu stricto) in dogs to county-wide social and environmental factors, as well as to reported cases of Lyme disease in people.

RESULTS

The data revealed a wide range of county level percent positive canine test results (1.2-27.3%) and human case reports (0.5-438.7 case reports/100,000 people). Dogs from highly (> 50%) forested areas and counties with lower population density had the highest percent positive test results, at 21.1% and 17.9%, respectively. Canine percent positive tests correlated with population-adjusted human case reports (R2 = 0.48, P < 0.0001), as well as population density, development intensity, temperature, normalized difference vegetation index, and habitat type. Subsequent multiple regression allowed an accurate prediction of infection risk in dogs (R2 = 0.90) but was less accurate at predicting human case reports (R2 = 0.74).

CONCLUSION

In areas where Lyme disease is endemic, canine serology continues to provide insight into risk factors for transmission to both dogs and people although some differences in geographic patterns of canine infection and human disease reports are evident.

Serologic responses to peptides of Anaplasma phagocytophilum and Borrelia burgdorferi in dogs infested with wild-caught Ixodes scapularis

Anaplasma phagocytophilum and Borrelia burgdorferi are both transmitted by Ixodes spp. and are associated with clinical illness in some infected dogs. This study evaluated canine antibody responses to the A. phagocytophilum p44 peptides APH-1 and APH-4 as well as the B. burgdorferi C6 peptide before and after doxycycline treatment. A total of eight dogs were infested with wild-caught I. scapularis for 1 week. Blood was collected prior to tick attachment and from Days 3-77 to 218-302 with doxycycline treatment beginning on Day 218. Blood was assayed for A. phagocytophilum DNA by PCR assay. Sera was assessed for antibodies by immunofluorescent antibody (IFA) test and ELISA. Anaplasma phagocytophilum DNA was amplified from blood of all dogs by Day 7. Antibodies to APH-4 were detected in serum as early as 14days after tick exposure and six dogs had APH-4 antibodies detected 3-7 days before antibodies against APH-1. All dogs were seropositive for A. phagocytophilum from Days 218 to 302. Antibodies to B. burgdorferi were detected in 6/8 dogs beginning 21days after I. scapularis infestation. Among the five dogs that remained seropositive at Day 218, C6 antibody levels declined on average 81% within 84days of initiating treatment. The results suggest that the APH-4 peptide may be more useful than APH-1 for detecting antibodies earlier in the course of an A. phagocytophilum infection. After doxycycline administration, C6 antibody levels but not APH-1 or APH-4 antibody levels decreased, suggesting a treatment effect on C6 antibody production.

Analytical validation of a reference laboratory ELISA for the detection of feline leukemia virus p27 antigen

Feline leukemia virus (FeLV) is an oncogenic retrovirus of cats. Immunoassays for the p27 core protein of FeLV aid in the detection of FeLV infections. Commercial microtiter-plate ELISAs have rapid protocols and visual result interpretation, limiting their usefulness in high-throughput situations. The purpose of our study was to validate the PetChek FeLV 15 ELISA, which is designed for the reference laboratory, and incorporates sequential, orthogonal screening and confirmatory protocols. A cutoff for the screening assay was established with 100% accuracy using 309 feline samples (244 negative, 65 positive) defined by the combined results of FeLV PCR and an independent reference p27 antigen ELISA. Precision of the screening assay was measured using a panel of 3 samples (negative, low-positive, and high-positive). The intra-assay coefficient of variation (CV) was 3.9–7.9%; the inter-assay CV was 6.0–8.6%. For the confirmatory assay, the intra-assay CV was 3.0–4.7%, and the inter-assay CV was 7.4–9.7%. The analytical sensitivity for p27 antigen was 3.7 ng/mL for inactivated whole FeLV and 1.2 ng/mL for purified recombinant FeLV p27. Analytical specificity was demonstrated based on the absence of cross-reactivity to related retroviruses. No interference was observed for samples containing added bilirubin, hemoglobin, or lipids. Based on these results, the new high-throughput design of the PetChek FeLV 15 ELISA makes it suitable for use in reference laboratory settings and maintains overall analytical performance.

Canine infection with Borrelia burgdorferi, Dirofilaria immitis, Anaplasma spp. and Ehrlichia spp. in Canada, 2013-2014

BACKGROUND

Canine test results generated by veterinarians throughout Canada from 2013-2014 were evaluated to assess the geographical distribution of canine infection with Borrelia burgdorferi, Dirofilaria immitis, Ehrlichia spp., and Anaplasma spp.

METHODS

The percent positive test results of 115,636 SNAP® 4Dx® Plus tests from dogs tested were collated by province and municipality to determine the distribution of these vector-borne infections in Canada.

RESULTS

A total of 2,844/115,636 (2.5%) dogs tested positive for antibody to B. burgdorferi. In contrast, positive test results for D. immitis antigen and antibodies to Ehrlichia spp. and Anaplasma spp. were low, with less than 0.5% of dogs testing positive for any one of these three agents nationwide. Provincial seroprevalence for antibodies to B. burgdorferi ranged from 0.5% (Saskatchewan)-15.7% (Nova Scotia); the areas of highest percent positive test results were in proximity to regions in the USA considered endemic for Lyme borreliosis, including Nova Scotia (15.7%) and Eastern Ontario (5.1%). These high endemic foci, which had significantly higher percent positive test results than the rest of the nation (P < 0.0001), were surrounded by areas of moderate to low seroprevalence in New Brunswick (3.7%), Quebec (2.8%), and the rest of Ontario (0.9%), as well as northward and westward through Manitoba (2.4%) and Saskatchewan (0.5%). Insufficient results were available from the westernmost provinces, including Alberta and British Columbia, to allow analysis.

CONCLUSION

Increased surveillance of these vector-borne disease agents, especially B. burgdorferi, is important as climate, vector range, and habitat continues to change throughout Canada. Using dogs as sentinels for these pathogens can aid in recognition of the public and veterinary health threat that each pose.

Factors associated with Anaplasma spp. seroprevalence among dogs in the United States

Background

Dogs in the United States are hosts to a diverse range of ticks and tick-borne pathogens, including A. phagocytophilum, an important emerging canine and human pathogen. Previously, a Companion Animal Parasite Council (CAPC)-sponsored workshop proposed factors purported to be associated with the infection risk for tick-transmitted pathogens in dogs in the United States, including climate conditions, socioeconomic characteristics, local topography, and vector distribution.

Methods

Approximately four million test results from routine veterinary diagnostic tests from 2011–2013, which were collected on a county level across the contiguous United States, are statistically analyzed with the proposed factors via logistic regression and generalized estimating equations. Spatial prevalence maps of baseline Anaplasma spp. prevalence are constructed from Kriging and head-banging smoothing methods.

Results

All of the examined factors, with the exception of surface water coverage, were significantly associated with Anaplasma spp. prevalence. Overall, Anaplasma spp. prevalence increases with increasing precipitation and forestation coverage and decreases with increasing temperature, population density, relative humidity, and elevation. Interestingly, socioeconomic status and deer/vehicle collisions were positively and negatively correlated with canine Anaplasma seroprevalence, respectively. A spatial map of the canine Anaplasma hazard is an auxiliary product of the analysis. Anaplasma spp. prevalence is highest in New England and the Upper Midwest.

Conclusions

The results from the two posited statistical models (one that contains an endemic areas assumption and one that does not) are in general agreement, with the major difference being that the endemic areas model estimates a larger prevalence in Western Texas, New Mexico, and Colorado. As A. phagocytophilum is zoonotic, the results of this analysis could also help predict areas of high risk for human exposure to this pathogen.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1431-7) contains supplementary material, which is available to authorized users.

Serological and molecular analysis of feline vector-borne anaplasmosis and ehrlichiosis using species-specific peptides and PCR

Background

With the exception of Bartonella spp. or Cytauxzoon felis, feline vector-borne pathogens (FVBP) have been less frequently studied in North America and are generally under-appreciated as a clinical entity in cats, as compared to dogs or people. This study investigated selected FVBP seroreactivity and PCR prevalence in cats using archived samples.

Methods

Feline blood samples submitted to the Vector Borne Diseases Diagnostic Laboratory (VBDDL) at North Carolina State University College of Veterinary Medicine (NCSU-CVM) between 2008 and 2013 were tested using serological assays and PCR. An experimental SNAP® Multi-Analyte Assay (SNAP® M-A) (IDEXX Laboratories, Inc. Westbrook, Maine, USA) was used to screen all sera for antibodies to Anaplasma and Ehrlichia genus peptides and A.phagocytophilum, A.platys, B.burgdorferi, E.canis, E.chaffeensis, and E.ewingii species-specific peptides. PCR assays were used to amplify Anaplasma or Ehrlichia DNA from extracted ethylenediaminetetraacetic acid (EDTA)-anti-coagulated blood samples. Amplicons were sequenced to identify species.

Results

Overall, 7.8 % (56/715) of cats were FVBP seroreactive and 3.2 % (13/406) contained Anaplasma or Ehrlichia DNA. Serologically, B.burgdorferi (5.5 %) was the most prevalent FVBP followed by A.phagocytophilum (1.8 %). Ehrlichia spp. antibodies were found in 0.14 % (12/715) of cats with species-specific seroreactivity to E.canis (n = 5), E.ewingii (n = 2) and E.chaffeensis (n = 1). Of seropositive cats, 16 % (9/56) were exposed to more than one FVBP, all of which were exposed to B.burgdorferi and either A.phagocytophilum (n = 7) or E.ewingii (n = 2). Based upon PCR and DNA sequencing, 4, 3, 3, 2, and 1 cat were infected with A.phagocytophilum, A.platys, E. ewingii, E. chaffeensis and E.canis, respectively.

Conclusions

Cats are exposed to and can be infected with vector-borne pathogens that commonly infect dogs and humans. To our knowledge, this study provides the first evidence for E.chaffeensis and E.ewingii infection in naturally-exposed cats in North America. Results from this study support the need for regional, serological and molecular FVBP prevalence studies, the need to further optimize serodiagnostic and PCR testing for cats, and the need for prospective studies to better characterize clinicopathological disease manifestations in cats infected with FVBP.

Persistent Ehrlichia ewingii infection in dogs after natural tick infestation

Background

Ehrlichia ewingii, which causes disease in dogs and people, is the most common Ehrlichia spp. infecting dogs in the United States, but little is known about how long E. ewingii infection persists in dogs.

Hypothesis/Objectives

To evaluate the persistence of natural infection with E. ewingii in dogs.

Animals

Four Class A Beagles; no previous exposure to ticks or tick‐borne infectious agents.

Methods

Dogs were exposed to ticks by weekly walks through tick habitat in north central Oklahoma; dogs positive for infection with Ehrlichia spp. by sequence‐confirmed PCR and peptide‐specific serology were evaluated for 733 days (D). Whole blood was collected once weekly for PCR, and serum was collected once monthly for detection of antibodies to Ehrlichia canis (peptide p16), Ehrlichia chaffeensis (indirect fluorescence antibody [IFA] and variable‐length PCR target [VLPT]), and E. ewingii (peptide p28).

Results

All dogs (4/4) became infected with Ehrlichia spp. as evidenced by seroconversion on IFA to E. chaffeensis (4/4); PCR detection of E. ewingii (4/4) and E. chaffeensis (2/4) DNA using both nested and real‐time assays; and presence of specific antibodies to E. ewingii (4/4) and E. chaffeensis (2/4). Infection with E. chaffeensis was not detected after D55. Intermittent E. ewingii rickettsemia persisted in 3 of 4 dogs for as long as 733 days.

Conclusions and Clinical Importance

Our data demonstrate that dogs infected with E. ewingii from tick feeding are capable of maintaining infection with this pathogen long‐term, and may serve as a reservoir host for the maintenance of E. ewingii in nature.

A serological survey of tick-borne pathogens in dogs in North America and the Caribbean as assessed by Anaplasma phagocytophilum, A. platys, Ehrlichia canis, E. chaffeensis, E. ewingii, and Borrelia burgdorferi species-specific peptides

Introduction

Tick-borne pathogens cause a spectrum of disease manifestations in both dogs and humans. Recognizing regional and temporal shifts in exposure are important as tick distributions change. To better delineate regional exposure to canine tick-borne pathogens, an expanded set of species-specific peptides were used to detect Anaplasma phagocytophilum (Aph), Anaplasma platys (Apl), Ehrlichia canis (Ec), Ehrlichia chaffeensis (Ech), Ehrlichia ewingii (Eew), and Borrelia burgdorferi (Bb) antibodies in canine serum.

Methods

Archived canine serum samples (n=6,582) collected during 2008–2010 and in 2012 from the US, Canada, and the Caribbean were retrospectively screened for antibodies against Ehrlichia and Anaplasma species-specific peptides. Overall, regional and temporal seroprevalence rates were determined.

Results

Overall Bb and Eew were the most seroprevalent pathogens. During 2008–2010, seroprevalence rates increased overall for Aph and Ech, and regionally, Bb and Aph seroprevalence rates increased in the South. Canada had unexpectedly high seroprevalence rates for Ec and Apl. The most common co-exposures were Eew+Ech, followed by Aph+Bb and Eew+Bb.

Conclusions

This study demonstrated significant shifts in canine vector-borne disease seroprevalence rates. The use of specific peptides facilitated improved geographic delineation of tick-borne pathogen distributions among dogs, which may enhance epidemiological surveillance of vector-borne pathogens shared by dogs and humans.

Experimental Dirofilaria immitis infection in dogs: effects of doxycycline and Advantage Multi® administration on immature adult parasites

To better understand the efficacy of doxycycline and 10% imidacloprid+2.5% moxidectin (Advantage Multi(®); Bayer Animal Health, Shawnee Mission, Kansas) on immature adult Dirofilaria immitis parasites and the results of antigen tests, 12 healthy, randomly selected dogs were experimentally infected with D. immitis and monitored for 407 days. Two dogs in each of three subgroups of four dogs were each infected with six (total of 6 dogs) or 12 (total of 6 dogs) D. immitis infective third-stage larvae (L3) obtained from infected mosquitoes. Doxycycline (10mg/kg per os twice daily×30 days) and 10% imidacloprid+2.5% moxidectin (1ml/kg by topical application every 30 days) treatment was initiated at 105 (Group A) and 149 (Group B) days post infection (PI) in two groups. One subgroup of two dogs given 6 L3 and one subgroup of two dogs given 12 L3 remained as untreated controls (GroupC). Serum obtained regularly throughout the study was evaluated by ELISA (PetChek(®) Heartworm-PF Antigen Test, IDEXX Laboratories, Inc.) for D. immitis adult circulating antigens. Six of the eight dogs in the treated groups had detectable antigenemia starting between 148 and 240 days post infection, but antigen was not detected in any treated dog at the end of the study. In the control subgroups, the dogs that received 6 L3 had no detectable antigen while the two dogs that received 12 L3 had detectable antigen beginning on Day 180 that persisted until the end of the study. None of the infected dogs had evidence of circulating microfilariae. At necropsy, no heartworms were recovered from the treated dogs, but all dogs in the untreated group had viable adult heartworms. These results indicate that early immature adult worms (3.5 and 5 months of age) of D. immitis were susceptible to a combined treatment regimen of doxycycline and 10% imidacloprid+2.5% moxidectin.

Development of antibodies to and PCR detection of Ehrlichia spp. in dogs following natural tick exposure

Dogs exposed to ticks in the southern US may become infected with multiple species of Ehrlichia. To better define infection risk, blood samples collected from 10 dogs infested with ticks via a natural infestation model were evaluated by blood smear examination, PCR, patient-side ELISAs (SNAP® 4Dx® and SNAP® 4Dx® Plus), IFA, and peptide based ELISA for evidence of infection with Ehrlichia canis, E. chaffeensis, and/or E. ewingii. Although morulae were rarely identified in blood smears, every dog (10/10) became infected with Ehrlichia spp. as evidenced by nested PCR detection of E. chaffeensis (7/10) and E. ewingii DNA (10/10); real-time PCR detection of E. chaffeensis (0/10) and E. ewingii (9/10); seroconversion on two different patient-side ELISAs (4/10 or 10/10); seroconversion on IFA to E. canis (10/10, maximum inverse titer=128-4096, GMTMAX=548.7) and E. chaffeensis (10/10, maximum inverse titer=1024-32,768, GMTMAX=4096); and seroconversion on peptide specific ELISA to E. chaffeensis VLPT (7/10) and E. ewingii p28 (9/10). Rickettsemia with E. chaffeensis and E. ewingii, as determined by nested PCR, persisted in dogs for an average of 3.2 or 30.5 days, respectively. Ehrlichia canis was not detected in any dog by any method, and no dogs developed signs of clinical disease. Our data suggest that in areas where ticks are common, dogs are at high risk of infection with Ehrlichia spp., particularly E. ewingii and E. chaffeensis, and can serve as a sentinel for monitoring for the presence of these zoonotic pathogens.

Development of a novel anti-canine CD20 monoclonal antibody with diagnostic and therapeutic potential

In humans, passive immunotherapy with anti-CD20 monoclonal antibodies (mAbs) has created immeasurable improvements in outcomes of patients with B-cell malignancies. However, the lack of comparable reagents has precluded development of this approach in dogs. We developed a novel anti-canine CD20 mAb designated as 6C8. 6C8 recognized the extracellular domain of canine CD20 and showed high-affinity binding to canine CD20 in solution, as well as in its native conformation on canine B-cells. The 6C8 target was expressed invariably in B-cell lineage cells, but not in T-cells or myeloid cells. 6C8 promoted phagocytosis of B-cell lymphoma cells by macrophages, but in its current framework, it did not induce direct cytotoxicity or complement dependent cytotoxicity. In summary, we have established a novel anti-canine CD20 mAb that is useful as a diagnostic tool to phenotype B-cells, and which could be integrated as a tool for passive immunotherapy to treat dogs with B-cell disorders.

Canine infection with Dirofilaria immitis, Borrelia burgdorferi, Anaplasma spp., and Ehrlichia spp. in the United States, 2010-2012

BACKGROUND

The geographic distribution of canine infection with vector-borne disease agents in the United States appears to be expanding.

METHODS

To provide an updated assessment of geographic trends in canine infection with Dirofilaria immitis, Borrelia burgdorferi, Ehrlichia spp., and Anaplasma spp., we evaluated results from an average of 3,588,477 dogs tested annually by veterinarians throughout the United States from 2010 - 2012.

RESULTS

As in an earlier summary report, the percent positive test results varied by agent and region, with antigen of D. immitis and antibody to Ehrlichia spp. most commonly identified in the Southeast (2.9% and 3.2%, respectively) and antibody to both B. burgdorferi and Anaplasma spp. most commonly identified in the Northeast (13.3% and 7.1%, respectively) and upper Midwest (4.4% and 3.9%, respectively). Percent positive test results for D. immitis antigen were lower in every region considered, including in the Southeast, than previously reported. Percent positive test results for antibodies to B. burgdorferi and Ehrlichia spp. were higher nationally than previously reported, and, for antibodies to Anaplasma spp., were higher in the Northeast but lower in the Midwest and West, than in the initial report. Annual reports of human cases of Lyme disease, ehrlichiosis, and anaplasmosis were associated with percent positive canine test results by state for each respective tick-borne disease agent (R2=0.701, 0.457, and 0.314, respectively). Within endemic areas, percent positive test results for all three tick-borne agents demonstrated evidence of geographic expansion.

CONCLUSIONS

Continued national monitoring of canine test results for vector-borne zoonotic agents is an important tool for accurately mapping the geographic distribution of these agents, and greatly aids our understanding of the veterinary and public health threats they pose.

Typical and atypical manifestations of Anaplasma phagocytophilum infection in dogs

Eighteen clinically ill dogs, naturally infected with Anaplasma phagocytophilum, were examined at a veterinary practice in Baxter, Minnesota. A clinical examination, complete blood cell count, enzyme- linked immunosorbent assay (ELISA) for A phagocytophilum, Borrelia burgdorferi, and Ehrlichia canis antibodies and Dirofilaria immitis antigen, and a polymerase chain reaction test for A phagocytophilum DNA were obtained for all dogs. Physical examination findings included fever, arthropathy, lymphadenopathy, epistaxis, acute gastritis, cervical hyperpathia, and central nervous system dysfunction. Complete blood cell count abnormalities included thrombocytopenia, morulae in neutrophils, anemia, leukopenia, eosinopenia, lymphopenia, and monocytosis. Seroreactivity to A phagocytophilum was found in 61%, B burgdorferi antibodies in 17%, and D immitis antigen in 5% of the dogs. Fever, arthropathy, neurologic dysfunction, and epistaxis are clinical syndromes that can be associated with A phagocytophilum infection. Treatment with doxycycline resulted in rapid resolution of clinical signs in all dogs.

Seroprevalence of Ehrlichia canis, Ehrlichia chaffeensis and Ehrlichia ewingii in dogs in North America

BACKGROUND

This study evaluated the exposure of dogs to three different Ehrlichia spp. in the south and central regions of the United States where vector-borne disease prevalence has been previously difficult to ascertain, particularly beyond the metropolitan areas.

METHODS

Dog blood samples (n = 8,662) were submitted from 14 veterinary colleges, 6 private veterinary practices and 4 diagnostic laboratories across this region. Samples were tested for E. canis, E. chaffeensis and E. ewingii specific antibodies using peptide microtiter ELISAs.

RESULTS

Overall, E. canis, E. chaffeensis and E. ewingii seroprevalence was 0.8%, 2.8%, and 5.1%, respectively. The highest E. canis seroprevalence (2.3%) was found in a region encompassing Arkansas, Louisiana, Oklahoma, Tennessee and Texas. E. chaffeensis seroreactivity was 6.6% in the central region (Arkansas, Kansas, Missouri, and Oklahoma) and 4.6% in the southeast region (Georgia, Maryland, North Carolina, South Carolina, Tennessee and Virginia). Seroreactivity to E. ewingii was also highest in the central region (14.6%) followed by the southeast region (5.9%). The geospatial pattern derived from E. chaffeensis and E. ewingii seropositive samples was similar to previous reports based on E. chaffeensis seroreactivity in white-tailed deer and the distribution of human monocytic ehrlichiosis (HME) cases reported by the CDC.

CONCLUSIONS

The results of this study provide the first large scale regional documentation of exposure to E. canis, E. chaffeensis and E. ewingii in pet dogs, highlighting regional differences in seroprevalence and providing the basis for heightened awareness of these emerging vector-borne pathogens by veterinarians and public health agencies.

Performance of a commercially available in-clinic ELISA for the detection of antibodies against Anaplasma phagocytophilum, Ehrlichia canis, and Borrelia burgdorferi and Dirofilaria immitis antigen in dogs

OBJECTIVE

To evaluate the sensitivity and specificity of a commercially available in-clinic ELISA for detection of heartworm infection and tick-borne diseases in dogs.

SAMPLE POPULATION

846 serum, plasma, or blood samples obtained from dogs.

PROCEDURES

Samples were evaluated via the in-clinic ELISA to detect antibodies against Anaplasma phagocytophilum, Ehrlichia canis, and Borrelia burgdorferi and Dirofilaria immitis (heartworm) antigen. True infection or immunologic status of samples was assessed by use of results of necropsy, an antigen assay for D immitis, and immunofluorescence assay or western blot analysis for antibodies against B burgdorferi, E canis, and A phagocytophilum.

RESULTS

Sensitivity and specificity of the in-clinic ELISA for detection of heartworm antigen (99.2% and 100%, respectively), antibodies against B burgdorferi (98.8% and 100%, respectively), and antibodies against E canis (96.2% and 100%, respectively) were similar to results for a similar commercial ELISA. In samples obtained from dogs in the northeast and upper Midwest of the United States, sensitivity and specificity of the in-clinic ELISA for antibodies against Anaplasma spp were 99.1% and 100%, respectively, compared with results for an immunofluorescence assay. Samples from 2 dogs experimentally infected with the NY18 strain of A phagocytophilum were tested by use of the in-clinic ELISA, and antibodies against A phagocytophilum were detected by 8 days after inoculation. Antibodies against Anaplasma platys in experimentally infected dogs cross-reacted with the A phagocytophilum analyte. Coinfections were identified in several of the canine serum samples.

CONCLUSIONS AND CLINICAL RELEVANCE

The commercially available in-clinic ELISA could be used by veterinarians to screen dogs for heartworm infection and for exposure to tick-borne pathogens.

Performance Validation and Method Comparison of an In-Clinic Enzyme-Linked Immunosorbent Assay for the Detection of Canine Pancreatic Lipase

Diagnosis of pancreatitis is often difficult in dogs that present with acute vomiting, anorexia, and abdominal pain, as these clinical signs may occur with a variety of other illnesses. While quantitative reference laboratory methods specific for canine pancreatic lipase are available to aid in diagnosis, results are generally not available until the next day. The objective of the current study was to validate a semiquantitative in-clinic rapid test for the measurement of canine pancreas–specific lipase (cPL) and to compare its performance to the reference lab method. Comparison of the reference method for cPL to the in-clinic assay demonstrated 96–100% agreement for canine serum samples with normal levels of cPL and 88–92% agreement for samples with elevated levels of cPL. Common interfering substances such as bilirubin, lipids, or hemoglobin had no effect on assay performance. Both within-day and day-to-day variations ranged from 10% to 20% of the calculated cPL concentration, which demonstrated a high degree of precision for the in-clinic assay. Performance of 3 lots of the in-clinic assay with the same set of canine serum samples demonstrated high assay reproducibility, with interclass correlation coefficients of ≥0.93. Results of the in-clinic cPL assay, based on both visual and calculated cPL concentrations, were consistent throughout 15 months of storage. The in-clinic test provides immediate, semiquantitative results to supplement existing pancreatitis diagnostics at the time of acute illness. Because the reference and in-clinic methods are aligned, they can be used together as an immediate aid pet-side and as a fully quantitative follow-up test at the reference laboratory.

Evaluation of a new in-clinic method for the detection of canine heartworm antigen

Canine heartworm is endemic in many parts of the world, and veterinarians rely on rapid in-clinic antigen tests to screen for this infection. Recently, an in-clinic, instrument-based rotor employing a colloidal gold agglutination immunoassay was launched in the marketplace (VetScan VS2(®) Canine Heartworm (HW) Antigen Test Kit; Abaxis, Inc.). Because of the widespread use of heartworm prevention and possible false negative test results in dogs with low heartworm burdens, the performance of the VetScan VS2(®) HW test and a commercially available in-clinic, membrane-based ELISA test (SNAP(®) Heartworm RT Test; IDEXX Laboratories) was compared using samples from dogs with low heartworm burdens and/or low levels of circulating antigen. Ninety serum samples were evaluated using the two methods. Testing was performed according to the manufacturer's product insert by personnel blinded to sample status. The samples were derived from two populations: dogs with necropsy-confirmed heartworm status (40 with 1-4 female worms, 30 with no worms), and field dogs (20) confirmed positive for antigen by microtiter plate ELISA (PetChek(®) Heartworm PF Antigen Test; IDEXX Laboratories). All 40 dogs with heartworms on necropsy were also confirmed to have circulating antigen by the PetChek HW ELISA. In necropsy-negative dogs (n=30), neither the VetScan VS2 HW nor SNAP HW tests detected heartworm antigen. Of the samples testing positive for antigen by PetChek HW (n=60), the VetScan VS2 HW and SNAP HW tests detected antigen in 15 and 56 samples, respectively. Percent agreement (plus 95% confidence interval) for each test relative to the PetChek HW qualitative result was 50% (40-60%) for VetScan VS2 HW and 96% (89-98%) for SNAP HW. Relative to the presence or absence of female worms at necropsy, agreement was 61% (50-72%) for VetScan VS2 HW and 99% (92-99.6%) for SNAP HW tests. It is clinically important that dogs with low heartworm burdens and/or low levels of circulating heartworm antigen be correctly identified by veterinarians in order to ensure prompt treatment, and the VetScan(®) VS2 HW test does not appear to be as accurate as the SNAP HW or PetChek HW tests when performed on this subset of patients.

Comparative strain analysis of Anaplasma phagocytophilum infection and clinical outcomes in a canine model of granulocytic anaplasmosis

A pilot study was conducted to determine whether existing human or canine strains of Anaplasma phagocytophilum would reproduce clinical disease in experimentally inoculated dogs similar to dogs with naturally acquired granulocytic anaplasmosis. Six hounds were inoculated intravenously with one human and two canine strains of A. phagocytophilum that were propagated in vitro in HL-60 cells or in infected autologous neutrophils. Infected dogs were monitored for lethargy, anorexia, petechiae, lymphadenopathy, and fever. Dogs were assessed for complete blood count (CBC), serum chemistry, and serology (IFA and SNAP® 4Dx®); for A. phagocytophilum blood load by quantitative polymerase chain reaction; and for cytokine production. Prominent clinical signs were generalized lymphadenopathy and scleral injection; only one dog developed fever lasting 4 days. Notable laboratory alterations included sustained leukopenia and thrombocytopenia in all dogs. A. phagocytophilum morulae were noted in blood between days 10 and 11, although all dogs retained A. phagocytophilum DNA in blood through day 60. All dogs seroconverted by days 10-15 by IFA, and by days 17-30 by SNAP 4Dx; cytokine analyses revealed 10-fold increases in interleukin-2 and interleukin-18 in the neutrophil-propagated 98E4 strain-infected dog. All A. phagocytophilum strains produced infection, although canine 98E4 strain reproduced clinical signs, hematologic changes, and inflammatory cytokine elevations most consistent with granulocytic anaplasmosis when recognized clinically. Therefore, this strain should be considered for use in future studies of A. phagocytophilum canine infection models.

Detection of feline panleukopenia virus using a commercial ELISA for canine parvovirus

Feline panleukopenia virus (FPV) is a significant pathogen of cats. Rapid virus detection is critical for treatment and management, especially in populations in which spread may occur. This study investigated the ability of the SNAP Canine Parvovirus Antigen Test Kit (SNAP Parvo, IDEXX Laboratories) to detect FPV with confirmation of viral identity by polymerase chain reaction (PCR) assay and genetic sequencing on fecal samples (n = 97) from cats with suspected FPV infection. Fifty-five samples were positive by SNAP Parvo; 54 of 55 were also positive by conventional PCR assay and were identified as FPV by genetic sequencing. This study demonstrates that SNAP Parvo can detect FPV in clinical samples.

Serological and molecular prevalence of Borrelia burgdorferi, Anaplasma phagocytophilum, and Ehrlichia species in dogs from Minnesota

A population of 731 naturally exposed pet dogs examined at a private practice in Baxter, Minnesota, an area endemic for Lyme disease and anaplasmosis, was tested by serological and molecular methods for evidence of exposure to or infection with selected vector-borne pathogens. Serum samples were tested by enzyme-linked immunosorbent assay (ELISA) for Anaplasma phagocytophilum, Borrelia burgdorferi, and Ehrlichia canis antibodies and for Dirofilaria immitis antigen. Blood samples from 273 dogs were also analyzed by polymerase chain reaction (PCR) for Anaplasma and Ehrlichia species DNA. Based on the owner history and the attending veterinarian's physical examination findings, dogs exhibiting illness compatible with anaplasmosis or borreliosis were considered clinical cases, and their results were compared to the healthy dog population. Antibodies to only A. phagocytophilum were detected in 217 (29%) dogs; to only B. burgdorferi, in 80 (11%) dogs; and seroreactivity to both organisms, in 188 (25%) dogs. Of 89 suspected cases of canine anaplasmosis or borreliosis, A. phagocytophilum or B. burgdorferi antibodies were detected in 22 dogs (25%) and 8 dogs (9%) respectively, whereas antibodies to both organisms were found in 38 dogs (43%). Ehrlichia canis antibodies and D. immitis antigen were each detected in 11 (1.5%) dogs. Anaplasma phagocytophilum DNA was amplified from 7 of 222 (3%) healthy dogs and 19 of 51 (37%) clinical cases. Seroreactivity to both A. phagocytophilum and B. burgdorferi was detected more frequently in suspected cases of anaplasmosis and/or borreliosis than seroreactivity to either organism alone. Based on PCR testing, A. phagocytophilum DNA was more prevalent in suspected cases of anaplasmosis or borreliosis than in healthy dogs from the same region.

Transforming growth factor-beta and insulin-like signalling pathways in parasitic helminths

The signal transduction pathways involved in regulating developmental arrest in the free-living nematode, Caenorhabditis elegans, are fairly well characterised. However, much less is known about how these processes may influence the developmental timing and maturation in helminth parasites. Here, we provide an overview of two signalling pathways implicated in the regulation of dauer larva formation in C. elegans, the insulin-like signalling pathway and the transforming growth factor-beta pathway, and explore what is known about these signalling pathways in a variety of parasitic helminths. Understanding the differences about how these pathways are affected by environmental cues in free-living versus parasitic species of helminths may provide insights into novel mechanisms for the control or prevention of helminth-induced disease.

Eukaryotic initiation factor 2 alpha subunit associates with TGF beta receptors and 14-3-3 epsilon and acts as a modulator of the TGF beta response

Schistosoma mansoni receptor kinase 1 (SmRK1) is a divergent member of the TGF beta receptor family. Intracellular proteins that associate with these receptors are likely to play an important role in signaling. 14-3-3 epsilon is a previously described cytoplasmic protein, which associates with both SmRK1 and the human type I TGF beta receptor (T beta RI); overexpression of 14-3-3 epsilon leads to enhanced TGF beta-mediated signaling by T beta RI. We now describe the identification of S. mansoni eukaryotic translation initiation factor 2 alpha subunit (eIF2 alpha), through its interaction with SmRK1 in a yeast two-hybrid assay. S. mansoni eIF2 alpha also interacts with human TGF beta receptors. Strongest association was demonstrated with kinase inactive receptors, particularly the type II TGF beta receptor (T beta RII). Both T beta RI and T beta RII phosphorylate eIF2 alpha in vitro, at sites other than the previously described eIF2 alpha phosphorylation sites. EIF2 alpha also modulates signaling by TGF beta receptors; however, in contrast to 14-3-3 epsilon, eIF2 alpha overexpression inhibits the TGF beta-driven response. These data suggest a novel function for eIF2 alpha in the TGF beta signaling pathway. In addition, we have demonstrated an independent interaction between eIF2 alpha and 14-3-3 epsilon. Coexpression of 14-3-3 epsilon with eIF2 alpha leads to the abrogation of the inhibitory effect of eIF2 alpha on TGF beta-mediated signaling. The interaction of these two regulatory proteins with each other and with the TGF beta receptors and their relative expression levels are likely to be important in fine-tuning the regulation of TGF beta signal transduction.

Human transforming growth factor-beta activates a receptor serine/threonine kinase from the intravascular parasite Schistosoma mansoni

The biology of the helminth parasite Schistosoma mansoni is closely integrated with that of its mammalian host. SmRK1, a divergent type I transforming growth factor-beta (TGF-beta) receptor of unknown ligand specificity, was previously identified as a candidate for a receptor that allows schistosomes to respond to host-derived growth factors. The TGF-beta family includes activin, bone morphogenetic proteins (BMPs), and TGF-beta, all of which can play crucial roles in metazoan development. The downstream signaling protein of receptors that respond to TGF-beta and activin is Smad2, whereas the receptors that respond to BMPs signal via Smad1. When a constitutively active mutant of SmRK1 was overexpressed with either schistosome Smad1 (SmSmad1) or SmSmad2, a receptor-dependent modulation of SmSmad phosphorylation and luciferase reporter activity occurred only with SmSmad2. To evaluate potential ligand activators of SmRK1, a chimeric receptor containing the extracellular domain of SmRK1 joined to the intracellular domain of the human type I TGF-beta receptor was used. The chimeric receptor bound radiolabeled TGF-beta and could activate a luciferase reporter gene in response to both TGF-beta 1 and TGF-beta 3 but not BMP7. Confirmatory results were obtained using full-length SmRK1. These experiments implicate TGF-beta as a ligand for SmRK1 and as a potential host-derived regulator of parasite growth and development.

Conserved role for 14-3-3epsilon downstream of type I TGFbeta receptors

Schistosoma mansoni receptor kinase-1 (SmRK1) is a divergent type I transforming growth factor beta (TGFbeta) receptor on the surface of adult parasites. Using the intracellular domain of SmRK1 as bait in a yeast two-hybrid screen we identified an interaction with S. mansoni 14-3-3epsilon. The interaction which is phosphorylation-dependent is not specific to schistosomes since 14-3-3epsilon also binds to TbetaRI, the human type I TGFbeta receptor. 14-3-3epsilon enhances TGFbeta-mediated signaling by TbetaRI and is the first TbetaRI-interacting non-Smad protein identified that positively regulates this receptor. The interaction of 14-3-3epsilon with schistosome and human TbetaRI suggests a conserved, but previously unappreciated, role for this protein in TGFbeta signaling pathways.

Functional conservation of Schistosoma mansoni Smads in TGF-beta signaling

To begin to understand the molecular basis of communication between the parasite Schistosoma mansoni and its mammalian host, we are studying the signaling pathway downstream of S. mansoni receptor kinase-1 (SmRK1), a divergent type I transforming growth factor-beta (TGF-beta) receptor found on the tegumental surface of the parasite. In this study, we have used a homology based PCR approach to clone two S. mansoni Smad (SmSmad) genes; Smads play a pivotal role in the most well understood signaling pathways initiated by the TGF-beta family of ligands in other organisms. Comparison of the amino acid sequences with those of other Smads reveals that the conserved MH1 and MH2 domains of SmSmads show a high degree of identity to homologues in Drosophila. Transcripts for both SmSmads are detected in the same developmental stages as SmRK1, and both are capable of interacting with the intracellular domain of the receptor in vitro. Functional characterization using the human type I TGF-beta receptor further confirms the highly conserved nature of these proteins, as both SmSmads show TGF-beta dependent enhancement of luciferase activity and nuclear translocation in mammalian cells. These data are the first to show a TGF-beta-like receptor/Smad signaling pathway in parasitic helminths and by analogy with other systems, is likely important in regulating schistosome development.

Retrospective analysis of the clinical utility of ambulatory electrocardiographic (Holter) recordings in syncopal dogs: 44 cases (1991-1995)

The objective of this study was to evaluate retrospectively the clinical utility of ambulatory (Holter) electrocardiographic monitoring in syncopal dogs and to compare the Holter recording with the clinic electrocardiogram (ECG) in these animals. Fifty Holter reports and 44 medical records from 44 dogs were evaluated. A syncopcal episode occurred during monitoring in 24% of the recordings. No obvious relationship was found between the frequency of syncope occurring before Holter recording and the likelihood of a dog having an episode during recording. Holter recordings were helpful in establishing a diagnosis 42% of the time, but no relationship was detected between the frequency of episodes occurring before Holter recording and the likelihood of a diagnostically useful Holter. An arrhythmia was ruled out as the cause of syncope in 12% of the recordings and was implicated as the cause of syncope in 30% of recordings. Of these, 20% were ventricular tachyarrhythmias and 10% were bradyarrhythmias including pacemaker failure. Ambulatory electrocardiographic recordings led to a therapeutic change in 38% of cases. A comparison of the Holter recordings and clinic ECGs documented the expected increased sensitivity for Holter detection of arrhythmias. The average clinic ECG heart rate consistently exceeded the average Holter heart rate with a mean difference between the average heart rates recorded by the two techniques of 31 bpm (range -8-87 bpm).

Melanocortin mediated inhibition of feeding behavior in rats

Melanocortinergic neurons are believed to play a role in the control of food intake. Melanocortin receptor agonists and antagonists modulate feeding in several mouse models of chemically and genetically induced hyperphagia. To date, little information is available describing the role of this neurological system in the control of the natural feeding cycle in genetically intact rats. To evaluate the involvement of melanocortins in spontaneous nocturnal feeding, the synthetic melanocortin receptor agonist, MTII and the antagonist, SHU9119 were administered ICV (third ventricle) alone and in combination. Dose-dependent inhibition or stimulation of food intake was observed with MTII or SHU9119, respectively. Co-injections containing equal concentrations of MTII and SHU9119 resulted in food intake that was indistinguishable from controls. Food intake patterns observed in studies in which various dose combinations of MTII and SHU9119 were co-injected are consistent with the concept that both affect feeding by acting on similar melanocortin receptors. The hypothesis that effects of melanocortins on feeding may be mediated via an NPY related pathway was tested by co-injecting MTII and NPY in a 2-h satiated food intake paradigm. MTII inhibited food intake induced by 5.0 microg hNPY in a dose dependent manner with the highest dose tested abolishing the NPY feeding response. The studies suggest that melanocortins act via specific receptors to control food intake in rats, possibly via an NPY related pathway. If similar neurochemical processes operate in humans, selectively modulating specific melanocortin receptor signaling may be an approach to the treatment of human obesity.

Heterogeneity of layer II neurons in human entorhinal cortex

Abnormalities in the layer II neurons of human entorhinal cortex have been implicated in the pathophysiology of Alzheimer's disease and schizophrenia. The reported abnormalities are not homogeneously distributed throughout the entorhinal cortex, suggesting that layer II of entorhinal cortex may contain different subpopulations of neurons, each with a different susceptibility to pathological mechanisms. In order to investigate the possible heterogeneity of neurons in layer II of human entorhinal cortex, we first identified distinct subdivisions of human entorhinal cortex by adapting the cytoarchitectonic criteria for subdivisions of monkey entorhinal cortex described by Amaral et al. (J Comp Neurol 264:326, 1987). The morphology and regional distribution of distinct subpopulations of human layer II neurons were determined through the use of immunohistochemical techniques. Multipolar, stellate, and modified pyramidal neurons in the characteristic cell clusters or islands of layer II were immunoreactive for nonphosphorylated neurofilament proteins. The intensity of immunoreactivity for the nonphosphorylated neurofilament proteins gradually increased along the rostrocaudal axis of entorhinal cortex and was primarily due to a similar gradient in the density of labeled neurons per island. The calcium-binding protein calbindin D-28K was found in both pyramidal and nonpyramidal neurons in layers II and superficial III. The distribution of calbindin-immunoreactive neurons also depended upon the region of entorhinal cortex. In rostral entorhinal cortex, labeled neurons were scattered throughout the superficial layers, whereas in caudal entorhinal cortex, distinctive patches of small calbindin-immunoreactive neurons were found among the layer II islands. Another calcium-binding protein, parvalbumin, was present in nonpyramidal neurons in layers II and III that were distinct from those containing calbindin. The regional distribution of parvalbumin-positive neurons was very similar to that of the neurofilament immunoreactive neurons; in rostral entorhinal cortex very few parvalbumin-labeled neurons were present but their frequency gradually increased in the caudal direction. In addition, punctate parvalbumin immunoreactivity was frequently encountered in the location of the nonphosphorylated neurofilament protein-positive layer II islands. These findings demonstrate that layer II of human entorhinal cortex contains distinct subpopulations of neurons, that the relative density of each subpopulation differs across cytoarchitectonic regions, and that the patterns of distribution of these subpopulations are in some cases similar and in other cases complementary. This heterogeneity in the organization of layer II of human entorhinal cortex has important implications for the study of some neuropsychiatric disorders.