Dogs and horses with antibodies to outer-surface protein C as on-time sentinels for ticks infected with Borrelia burgdorferi in New York State in 2011

Knowledge and perception of equine ticks and tick-borne diseases of Pennsylvania horse owners and caretakers

There is limited data on current knowledge of Pennsylvania horse caretakers on tick-borne diseases (TBDs), tick identification, and tick management practices. This study aimed to determine tick knowledge, concern, and management among Pennsylvania equine caretakers using an online survey. Descriptive statistics and one-way ANOVA tests were used to analyze data. The survey received 894 responses (539 completed) from Pennsylvania equine owners and caretakers. The largest proportion of respondents cared for 3-5 horses (31 %), followed by 2 horses (27 %). Veterinarian-confirmed diagnosis rates of two TBDs, Lyme disease and anaplasmosis, were 38 % and 22 %, respectively. Most respondents (39 %) were moderately confident in recognizing Lyme disease, while most (44 %) were not confident at all in recognizing anaplasmosis. Most respondents (69 %) were either extremely or very concerned about their horses contracting any TBDs. Tick bite and TBD prevention methods used by equine caretakers included performing tick checks, using on-animal repellents, and conducting pasture/landscape management. Ten knowledge-based questions were asked, and the mean correct score was 3.97 ± 2.18 out of 10 possible points. There were significant positive associations between higher knowledge scores and previous veterinarian-confirmed equine Lyme disease diagnosis, higher concern level of TBDs, and higher frequency of tick checks. With increased equine TBD prevalence and high levels of horse owner concern about TBD, Extension educators should focus on teaching about TBDs and managing ticks on horses and farms.

Prevalence of Anaplasma phagocytophilum and Borrelia burgdorferi infection in horses from Pennsylvania (2017-2019) using antibody and organism-based detection

OBJECTIVE

To determine the prevalence of Anaplasma phagocytophilum and Borrelia burgdorferi infections in Pennsylvania horses.

ANIMALS

271 horses.

PROCEDURES

A survey was conducted with PCR and serology to evaluate anaplasmosis and Lyme disease infections in horses from Pennsylvania that were suspected for tick-borne infection.

RESULTS

A phagocytophilum was detected in 19/271 (7.0%) Pennsylvania horses tested by the duplex PCR. B burgdorferi was not detected in any horse blood tested by PCR. Overall, 120/271 (44.3%) horses tested positive for presence of A phagocytophilum antibodies by at least the IDEXX SNAP 4Dx Plus lateral flow immunosorbent (SNAP) or indirect fluorescent antibody (IFA) assay, with 69 (25.5%) testing positive by both SNAP and IFA; 43 (15.9%) tested positive by IFA only, and 8 (3.0%) tested positive by SNAP only. Similarly, 209/271 (77.1%) horses tested positive for the presence of B burgdorferi antibodies by at least 1 test, with 139 (51.3%) testing positive by both SNAP and IFA; 45 (16.6%) tested positive by SNAP only, and 25 (9.2%) tested positive by IFA.

CLINICAL RELEVANCE

Both A phagocytophilum and B burgdorferi are important tick-borne infections. The study provides prevalence data for both A phagocytophilum and B burgdorferi and compares test performance. For serologic detection, IFA detected antibodies to A phagocytophilum in a higher proportion (41.3%) of horses compared to SNAP (28.4%), while SNAP detected antibodies to B burgdorferi in a higher proportion (67.9%) of horses compared to IFA (60.5%). Both diseases showed a high seroprevalence in all areas surveyed.

An analysis of companion animal tick encounters as revealed by photograph-based crowdsourced data

Background

Community science is increasingly utilized to track important vectors of companion animal disease, providing a scalable, cost‐effective strategy for identifying new foci, changing phenology, and disease prevalence across wide geographies.

Objectives

We examined photographs of ticks found attached to predominately dogs and cats reported to a photograph‐based tick surveillance program to identify potential areas for improvements in tick prevention education and risk intervention.

Methods

We compared estimated days of tick attachment using a Kruskal–Wallis one‐way analysis of variance, and a Pearson's chi‐square analysis of variance on the number of submissions by host type submitted for each season.

Results

The blacklegged tick (Ixodes scapularis) was the most common species reported (39.8%). Tick photographs submitted were almost entirely adults (89.5%), and ticks found on companion animals exhibited an estimated median engorgement time of 2.5 days. Ixodes scapularis displayed the highest median engorgement of the top tick species found feeding on companion animals (χ² = 98.96, p < 0.001). Ticks were spotted year‐round; during spring and summer, ticks collected from pets represented 15.4 and 12.8% of all submissions, but increased to 28.5 and 35.2% during autumn and winter, respectively.

Conclusions

Crowdsourced data reveal that mostly adult ticks are detected on pets, and they are found at a point in the blood‐feeding process that puts pets at heightened risk for disease transmission. The increase in proportion of ticks found on pets during colder months may reveal a critical knowledge gap amongst pet owners regarding seasonal activity of I. scapularis, a vector of Lyme disease, providing an opportunity for prevention‐education.

Evaluation of 2 ELISAs to determine Borrelia burgdorferi seropositivity in horses over a 12-month period

The blacklegged tick (Ixodes scapularis), which transmits Borrelia burgdorferi, the causative agent of Lyme disease, has undergone rapid range expansion in Ontario. In horses, Lyme disease remains an enigmatic disease, with limited understanding of the pathogenesis and many issues pertaining to selection and interpretation of laboratory tests. We evaluated B. burgdorferi seropositivity in naturally exposed horses over a 12-mo period and compared paired samples with 2 common serologic tests. Serum samples were collected in 2017, ~1 y after initial testing, from a cohort of 22 horses that were seropositive in a 2016 seroprevalence study. Samples were tested using a C6 ELISA and a multiplex ELISA targeting outer surface proteins A, C, and F. 1 y after initial testing, 14 of 22 (64%) horses remained seropositive; 7 (32%) were positive on the multiplex ELISA, 2 (9%) on C6 ELISA, and 5 (23%) on both tests. Repeatability was 100% for the C6 ELISA, and 95% for the multiplex ELISA, with no significant difference between paired sample multiplex titer values. Our results indicate strong intra-test reliability, although further investigation is required to determine the clinical significance of serologic testing.

Seroprevalence of Antibodies Against Anaplasma Phagocytophilum and Borrelia Burgdorferi in Horses (Equus Caballus) from Northern Algeria

Introduction

Horses (Equus caballus) are susceptible to tick-borne diseases. Two of them, Lyme borreliosis due to Borrelia burgdorferi and granulocytic anaplasmosis due to Anaplasma phagocytophilum were investigated in Algerian horses. The diseases have been less extensively studied in horses and results pertinent to Algeria have not been published.

Material and Methods

Blood samples were obtained from 128 horses. IgG antibodies directed against Anaplasma phagocytophilum and Borrelia burgdorferi were detected by an indirect immunofluorescence antibody test (IFAT) and ELISA. The potential effects of age, gender, breed, and health status on seropositivity were also evaluated.

Results

Using IFAT, 28 (21.8%) and 25 (19.5%) animals were positive for B. burgdorferi and A. phagocytophilum, respectively. Using ELISA, 19 (14.8%) and 33 (25.9%) animals were positive for these bacteria.

Conclusion

The study shows that horses in Algeria are exposed or co-exposed to tick-transmitted zoonotic bacterial species.

Borreliosis in Sport Horse Practice

Given the variable clinical signs attributed to Borrelia burgdorferi, including infectious arthritis, neurologic disease, and behavioral changes, B burgdorferi is an important differential for decreased performance in sport horses. The primary vectors (Ixodes tick species) are expanding their range and thus Borrelia species are located in a wider area, making exposure more likely. Due to regionally high seroprevalence and vague clinical signs, diagnosis of Lyme disease in the horse is believed overestimated. Antibiotics are first-line treatment of confirmed Lyme disease. A single positive serologic test, by itself, is not conformation of Lyme disease but is evidence of current or past infection.

Borrelia burgdorferi Infection and Lyme Disease in North American Horses: A Consensus Statement

Borrelia burgdorferi infection is common in horses living in Lyme endemic areas and the geographic range for exposure is increasing. Morbidity after B. burgdorferi infection in horses is unknown. Documented, naturally occurring syndromes attributed to B. burgdorferi infection in horses include neuroborreliosis, uveitis, and cutaneous pseudolymphoma. Although other clinical signs such as lameness and stiffness are reported in horses, these are often not well documented. Diagnosis of Lyme disease is based on exposure to B. burgdorferi, cytology or histopathology of infected fluid or tissue and antigen detection. Treatment of Lyme disease in horses is similar to treatment of humans or small animals but treatment success might not be the same because of species differences in antimicrobial bioavailability and duration of infection before initiation of treatment. There are no approved equine label Lyme vaccines but there is strong evidence that proper vaccination could prevent infection in horses.

Serological detection of Tick-Borne Relapsing Fever in Texan domestic dogs

Tick-Borne Relapsing Fever (TBRF) is caused by spirochetes in the genus Borrelia. Very limited information exists on the incidence of this disease in humans and domestic dogs in the United States. The main objective of this study is to evaluate exposure of dogs to Borrelia turicatae, a causative agent of TBRF, in Texas. To this end, 878 canine serum samples were submitted to Texas A&M Veterinary Medical Diagnostic Laboratory from October 2011 to September 2012 for suspected tick-borne illnesses. The recombinant Borrelial antigen glycerophosphodiester phosphodiesterase (GlpQ) was expressed, purified, and used as a diagnostic antigen in both ELISA assays and Immunoblot analysis. Unfortunately, due to significant background reaction, the use of GlpQ as a diagnostic marker in the ELISA assay was not effective in discriminating dogs exposed to B. turicatae. Nevertheless, immunoblot assays showed that 17 out of 853 samples tested were considered to be seropositive, which constitutes 1.99% of all Texas samples tested in this study. The majority of positive samples were from central and southern Texas. Exposure to TBRF spirochetes may be seasonal, with 70.59% (12 out of 17) of the cases detected between June and December. In addition, 2 out of the 17 sero-reactive cases (11.76%) showed reactivity to both B. burgdorferi (causative agent of Lyme disease) and B. turicatae (a causative agent of TBRF). This is the first report of TBRF sero-prevalence in companion animals in an endemic area. Our findings further indicate that B. turicatae is maintained in domestic canids in Texas in regions where human disease also occurs, suggesting that domestic dogs could serve as sentinels for this disease.

Identification of a defined linear epitope in the OspA protein of the Lyme disease spirochetes that elicits bactericidal antibody responses: Implications for vaccine development

The lipoprotein OspA is produced by the Lyme disease spirochetes primarily in unfed ticks. OspA production is down-regulated by the blood meal and it is not produced in mammals except for possible transient production during late stage infection in patients with Lyme arthritis. Vaccination with OspA elicits antibody (Ab) that can target spirochetes in the tick midgut during feeding and inhibit transmission to mammals. OspA was the primary component of the human LYMErix^™ vaccine. LYMErix^™ was available from 1998 to 2002 but then pulled from the market due to declining sales as a result of unsubstantiated concerns about vaccination induced adverse events and poor efficacy. It was postulated that a segment of OspA that shares sequence similarity with a region in human LFA-1 and may trigger putative autoimmune events. While evidence supporting such a link has not been demonstrated, most efforts to move forward with OspA as a vaccine component have sought to eliminate this region of concern. Here we identify an OspA linear epitope localized within OspA amino acid residues 221–240 (OspA_221–240) that lacks the OspA region suggested to elicit autoimmunity. A peptide consisting of residues 221–240 was immunogenic in mice. Ab raised against OspA_221–240 peptide surface labeled B. burgdorferi in IFAs and displayed potent Ab mediated-complement dependent bactericidal activity. BLAST analyses identified several variants of OspA_221–240 and a closely related sequence in OspB. It is our hypothesis that integration of the OspA_221–240 epitope into a multivalent-OspC based chimeric epitope based vaccine antigen (chimeritope) could result in a subunit vaccine that protects against Lyme disease through synergistic mechanisms.

Searching for Lyme borreliosis in Australia: results of a canine sentinel study

BACKGROUND

Lyme borreliosis is a common tick-borne disease of the northern hemisphere that is caused by bacterial spirochaetes of the Borrelia burgdorferi (sensu lato) (Bbsl) complex. To date, there has been no convincing evidence for locally-acquired Lyme borreliosis on the Australian continent and there is currently a national debate concerning the nature and distributions of zoonotic tick-transmitted infectious disease in Australia. In studies conducted in Europe and the United States, dogs have been used as sentinels for tick-associated illness in people since they readily contact ticks that may harbour zoonotic pathogens. Applying this principle, we used a combination of serological assays to test dogs living in tick 'hot spots' and exposed to the Australian paralysis tick, Ixodes holocyclus, for evidence of exposure to B. burgdorferi (s.l.) antigens and other vector-borne pathogens.

RESULTS

Altogether, 555 dogs from four demographic groups were recruited into this study. One dog had evidence of exposure to Anaplasma spp. but no other dog was positive in screening tests. A total of 122 dogs (22.0%) had a kinetic ELISA (KELA) unit value > 100, and one dog with a high titre (399.9 KELA units) had been vaccinated against B. burgdorferi (sensu stricto) before travelling to Australia. Older dogs and those with a history of tick paralysis were significantly more likely to have a KELA unit value > 100. Line immunoassay analysis revealed moderate-to-weak (equivocal) bands in 27 (4.9%) dogs.

CONCLUSIONS

Except for a single dog presumed to have been exposed to Anaplasma platys, infection with Anaplasma spp. B. burgdorferi (s.l.), Ehrlichia spp., and Dirofilaria immitis, was not detected in the cohort of Australian dogs evaluated in this study. These results provide further evidence that Lyme borreliosis does not exist in Australia but that cross-reacting antibodies (false positive results) are common and may be caused by the transmission of other tick-associated organisms.

Regional seroreactivity and vector-borne disease co-exposures in dogs in the United States from 2004-2010: utility of canine surveillance

Vector-borne disease (VBD) pathogens remain an emerging health concern for animals and humans throughout the world. Surveillance studies of ticks and humans have made substantial contributions to our knowledge of VBD epidemiology trends, but long-term VBD surveillance data of dogs in the United States is limited. This seroreactivity study assessed US temporal and regional trends and co-exposures to Anaplasma, Babesia, Bartonella, Borrelia burgdorferi, Dirofilaria immitis, Ehrlichia spp., and spotted fever group Rickettsia in dogs from 2004-2010. Dog serum samples (N=14,496) were submitted to the North Carolina State University, College of Veterinary Medicine, Vector Borne Disease Diagnostic Laboratory for vector-borne pathogens diagnostic testing using immunofluorescent antibody (IFA) and enzyme-linked immunosorbent assay (ELISA) assays. These convenience samples were retrospectively reviewed and analyzed. The largest proportion of samples originated from the South (47.6%), with the highest percent of seroreactive samples observed in the Midatlantic (43.4%), compared to other US regions. The overall seroreactivity of evaluated VBD antigens were Rickettsia rickettsia (10.4%), B. burgdorferi (5.2%), Ehrlichia spp. (4.3%), Bartonella henselae (3.8%), Anaplasma spp. (1.9%), Bartonella vinsonii subsp. berkhoffii (1.5%), Babesia canis (1.1%), and D. immitis (0.8%). Significant regional and annual seroreactivity variation was observed with B. burgdorferi, Ehrlichia, and Rickettsia exposures. Seasonal seroreactivity variation was evident with Rickettsia. Seroreactivity to more than one antigen was present in 16.5% of exposed dogs. Nationally, the most prevalent co-exposure was Rickettsia with Ehrlichia spp. (5.3%), and the highest odds of co-exposure was associated with Anaplasma spp. and B. burgdorferi (odds ratio=6.6; 95% confidence interval 5.0, 8.8). Notable annual and regional seroreactivity variation was observed with certain pathogens over 7 years of study, suggesting canine surveillance studies may have value in contributing to future VBD knowledge.

Immunization with a Borrelia burgdorferi BB0172-derived peptide protects mice against lyme disease

Lyme disease is the most prevalent arthropod borne disease in the US and it is caused by the bacterial spirochete Borrelia burgdorferi (Bb), which is acquired through the bite of an infected Ixodes tick. Vaccine development efforts focused on the von Willebrand factor A domain of the borrelial protein BB0172 from which four peptides (A, B, C and D) were synthesized and conjugated to Keyhole Limpet Hemocyanin, formulated in Titer Max® adjuvant and used to immunize C3H/HeN mice subcutaneously at days 0, 14 and 21. Sera were collected to evaluate antibody responses and some mice were sacrificed for histopathology to evaluate vaccine safety. Twenty-eight days post-priming, protection was evaluated by needle inoculation of half the mice in each group with 10³ Bb/mouse, whereas the rest were challenged with 10⁵Bb/mouse. Eight weeks post-priming, another four groups of similarly immunized mice were challenged using infected ticks. In both experiments, twenty-one days post-challenge, the mice were sacrificed to determine antibody responses, bacterial burdens and conduct histopathology. Results showed that only mice immunized with peptide B were protected against challenge with Bb. In addition, compared to the other the treatment groups, peptide B-immunized mice showed very limited inflammation in the heart and joint tissues. Peptide B-specific antibody titers peaked at 8 weeks post-priming and surprisingly, the anti-peptide B antibodies did not cross-react with Bb lysates. These findings strongly suggest that peptide B is a promising candidate for the development of a new DIVA vaccine (Differentiate between Infected and Vaccinated Animals) for protection against Lyme disease.

Opportunities for bead-based multiplex assays in veterinary diagnostic laboratories

Bead-based multiplex assays (BBMAs) are applicable for high throughput, simultaneous detection of multiple analytes in solution (from several to 50–500 analytes within a single, small sample volume). Currently, few assays are commercially available for veterinary applications, but they are available to identify and measure various cytokines, growth factors and their receptors, inflammatory proteins, kinases and inhibitors, neurobiology proteins, and pathogens and antibodies in human beings, nonhuman primates, and rodent species. In veterinary medicine, various nucleic acid and protein-coupled beads can be used in, or for the development of, antigen and antibody BBMAs, with the advantage that more data can be collected using approximately the same amount of labor as used for other antigen and antibody assays. Veterinary-related BBMAs could be used for detection of pathogens, genotyping, measurement of hormone levels, and in disease surveillance and vaccine assessment. It will be important to evaluate whether BBMAs are “fit for purpose,” how costs and efficiencies compare between assays, which assays are published or commercially available for specific veterinary applications, and what procedures are involved in the development of the assays. It is expected that many veterinary-related BBMAs will be published and/or become commercially available in the next few years. The current review summarizes the BBMA technology and some of the currently available BBMAs developed for veterinary settings. Some of the human diagnostic BBMAs are also described, providing an example of possible templates for future development of new veterinary-related BBMAs.