Epidemiology of Vector-Borne Pathogens Among U.S. Government Working Dogs

High seroprevalence of selected vector-borne pathogens in dogs from Saipan, Northern Mariana Islands

BACKGROUND

Canine vector-borne diseases (CVBDs) are illnesses caused by pathogens transmitted by blood-feeding arthropods such as ticks and mosquitoes. Many CVBDs, including dirofilariosis, anaplasmosis, and ehrlichiosis, are globally distributed and may cause a variety of clinical signs in dogs. Several CVBD agents are zoonotic, making epidemiological surveillance a joint veterinary and public health effort. In this study, we determined the seropositivity of four pathogens from dogs on Saipan, Northern Mariana Islands, a US Commonwealth located in the western Pacific Ocean.

METHODS

Blood samples (n = 443) were collected from client-owned, owner surrendered, and shelter dogs that participated in an island-wide spay-and-neuter event in 2023. All samples were assessed using a commercial, point-of-care enzyme-linked immunosorbent assay (ELISA) test (SNAP® 4Dx® Plus, IDEXX Laboratory, Westbrook, Maine, USA) to detect the Dirofilaria immitis antigen and antibodies against Ehrlichia spp., Anaplasma spp., and Borrelia burgdorferi sensu lato. Risk factors were assessed for each pathogen through a univariate analysis, followed by a multivariable logistic regression.

RESULTS

Overall, 66.1% (n = 300/443) of the dogs tested positive for at least one pathogen, with the highest prevalence observed for Ehrlichia spp. (58.0%; n = 246/443), followed by Anaplasma spp. (43.1%; n = 184/443) and D. immitis (14.8%; n = 63/443). Among the dogs with a single pathogen detected (30.9%; n = 137/443), Ehrlichia spp. was most prevalent (64.9%; n = 89/137), followed by Anaplasma spp. (23.3%; n = 32/137) and D. immitis (11.6%; n = 16/137). For co-detection of two or more pathogens (36.7%; n = 163/443), Ehrlichia spp. + Anaplasma spp. presented the highest frequency (70.5%; n = 115/163), followed by Ehrlichia spp. + D. immitis (6.7%; n = 11/163), Anaplasma spp. + D. immitis (3.6%; n = 6/163), and Ehrlichia spp. + Anaplasma spp. + D. immitis (19.0%; n = 31/163). Age (P = < 0.001), residing district (P = 0.001), and ownership status (P = < 0.001) were significantly associated with D. immitis positive status in a univariable analysis. Age (P = < 0.001), residing district (P = 0.177), and ownership status (P = 0.014) were significant in a univariable analysis with Ehrlichia spp. as an outcome. Finally, Anaplasma spp. had a significant association with ownership status (P = < 0.001) as a risk factor in a univariable analysis.

CONCLUSIONS

This study shows high seropositivity for CVBPs in a dog population living in a poorly studied area. The results of this study suggest that strategies for the prevention and control of these CVBDs should be reinforced on the Island of Saipan.

Global prevalence of Borrelia burgdorferi and Anaplasma phagocytophilum coinfection in wild and domesticated animals: A systematic review and meta-analysis

Background

Both Borrelia burgdorferi (Bb) and Anaplasma phagocytophilum (Ap) can infect humans and animals through tick-borne transmission, resulting in zoonosis. Under certain conditions, human infection can lead to Lyme disease (LD) and human granulocytosis (HGA), whereas infection in animals can cause various acute and non-specific symptoms. The combination of Bb and Ap has been reported to increase the disease severity in infected animals. In this systematic review and meta-analysis, we investigated the global diversity of Bb and Ap coinfection in animals and their prevalence and distribution regarding spatial and species ecoepidemiology.

Methods

We queried PubMed, Web of Science, Embase, and the Cochrane Library for original studies on Bb and Ap coinfection. We assessed the rate of Bb and Ap in all included articles by single-group meta-analysis and subgroup analyses. We evaluated publication bias using a combination of funnel plots, Egger's tests, and Begg's tests, and conducted risk of bias assessment using the SYRCLE tool.

Results

Our search retrieved 40 articles, with eight involving 8419 infected animals meeting our inclusion criteria. The SYRCLE bias risk assessment indicated that most of the included studies were of high quality. Forest maps showed that the combined Bb and Ap infection rate in animals worldwide was 5.5% (95% confidence interval (CI) = 2.4-9.6). Subgroup analysis of forest maps showed that the coinfection rates were 8.2% (95% CI = 2.2-17.2) in North American, 0.2% (95% CI = 0.1-0.7) in European, and 1.2% (95% CI = 0.8-1.8) in Asian animals. Coinfection rates were 6.7% (95% CI = 2.7-12.2) in domestic and 0.0% (95% CI = 0.0-0.4) in wild animals. The coinfection rates were 9% (95% CI = 5.7-12.8) in domestic horses and 6% (95% CI = 1.9-12.2) in domestic dogs, whereas 7.5% (95% CI = 3-17.9) in wild squirrels and 0.2% (95% CI = 0.1-0.7) in wild mice. Funnel diagrams, Egger's tests, and Begg's tests showed no significant publication bias in the included studies.

Conclusions

Spatial epidemiology showed that coinfection with Bb and Ap in animals worldwide was most prevalent in the southwestern region of North America, whereas species epidemiology showed that coinfection was most prevalent in domesticated horses, followed by wild squirrels and domesticated dogs, but was less common in wild mice. These data on the epidemiological status of Bb and Ap coinfection in animals may help guide the prevention and treatment of zoonosis.

Assessing the Influence of Climate Change and Environmental Factors on the Top Tick-Borne Diseases in the United States: A Systematic Review

In the United States (US), tick-borne diseases (TBDs) have more than doubled in the past fifteen years and are a major contributor to the overall burden of vector-borne diseases. The most common TBDs in the US-Lyme disease, rickettsioses (including Rocky Mountain spotted fever), and anaplasmosis-have gradually shifted in recent years, resulting in increased morbidity and mortality. In this systematic review, we examined climate change and other environmental factors that have influenced the epidemiology of these TBDs in the US while highlighting the opportunities for a One Health approach to mitigating their impact. We searched Medline Plus, PUBMED, and Google Scholar for studies focused on these three TBDs in the US from January 2018 to August 2023. Data selection and extraction were completed using Covidence, and the risk of bias was assessed with the ROBINS-I tool. The review included 84 papers covering multiple states across the US. We found that climate, seasonality and temporality, and land use are important environmental factors that impact the epidemiology and patterns of TBDs. The emerging trends, influenced by environmental factors, emphasize the need for region-specific research to aid in the prediction and prevention of TBDs.

Validation of a multiplex microsphere immunoassay for detection of antibodies to Trypanosoma cruzi in dogs

The vector-borne protozoan parasite Trypanosoma cruzi causes Chagas disease in humans, dogs, and many other mammalian hosts. Canine Chagas disease is increasingly diagnosed in dogs of the southern United States where triatomine insect vectors occur, and there are limited veterinary testing options; only the indirect fluorescent antibody (IFA) test is offered at a single accredited diagnostic laboratory. We evaluated a multiplex microsphere immunoassay (MIA) for the detection of antibodies against T. cruzi in dogs and compared it with existing serologic methods to establish cutoff values and relative sensitivity and specificity. We tested 135 canine sera that had been characterized using the IFA and off-label use of 2 commercial rapid assays with our multiplex MIA against 12 antigens: 9 T. cruzi antigens, a negative control recombinant protein (green fluorescent protein, GFP), a Leishmania antigen, and a canine parvovirus antigen (used as an antibody control given near-ubiquitous parvoviral vaccination). The median fluorescence intensity (MFI) ratio between each T. cruzi antigen and GFP was calculated for every sample. Samples with an antigen:GFP MFI ratio > 4 SDs above the mean of 25 known-negative sera were considered positive to that antigen. Samples testing positive to ≥ 2 antigens were considered positive for T. cruzi antibodies. Compared to the IFA, our multiplex MIA had a relative sensitivity of 100% and specificity of 97.0%. Given its precision, high-throughput format, potential for automation, and lack of subjective interpretation, our multiplex MIA should be considered a valid and improved assay for T. cruzi antibodies in dogs.

Toward One Health: a spatial indicator system to model the facilitation of the spread of zoonotic diseases

Recurrent outbreaks of zoonotic infectious diseases highlight the importance of considering the interconnections between human, animal, and environmental health in disease prevention and control. This has given rise to the concept of One Health, which recognizes the interconnectedness of between human and animal health within their ecosystems. As a contribution to the One Health approach, this study aims to develop an indicator system to model the facilitation of the spread of zoonotic diseases. Initially, a literature review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to identify relevant indicators related to One Health. The selected indicators focused on demographics, socioeconomic aspects, interactions between animal and human populations and water bodies, as well as environmental conditions related to air quality and climate. These indicators were characterized using values obtained from the literature or calculated through distance analysis, geoprocessing tasks, and other methods. Subsequently, Multi-Criteria Decision-Making (MCDM) techniques, specifically the Entropy and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) methods, were utilized to combine the indicators and create a composite metric for assessing the spread of zoonotic diseases. The final indicators selected were then tested against recorded zoonoses in the Valencian Community (Spain) for 2021, and a strong positive correlation was identified. Therefore, the proposed indicator system can be valuable in guiding the development of planning strategies that align with the One Health principles. Based on the results achieved, such strategies may prioritize the preservation of natural landscape features to mitigate habitat encroachment, protect land and water resources, and attenuate extreme atmospheric conditions.

Protozoal meningoencephalitis and myelitis in 4 dogs associated with Trypanosoma cruzi infection

American trypanosomiasis is caused by the zoonotic protozoa Trypanosoma cruzi and primarily results in heart disease. Organisms also infect the central nervous system (CNS). The Texas A&M University veterinary teaching hospital archive was searched for dogs with CNS disease with intralesional protozoal amastigotes. This study summarizes 4 cases of dogs with disseminated trypanosomiasis and CNS involvement confirmed by quantitative polymerase chain reaction (qPCR) with T. cruzi primers. Clinical signs included lethargy, respiratory distress, tetraparesis, and seizures. Central nervous system lesions included meningeal congestion (1/4), necrosis with hemorrhage in the spinal cord gray and white matter (2/4), and histiocytic meningoencephalitis (4/4), and meningomyelitis (2/4) with intralesional and intracellular protozoal. Genotyping identified 1 case of T. cruzi discrete typing unit (DTU) TcI and 2 cases as TcIV, both are common variants in the United States. Trypanosomiasis should be considered a differential diagnosis for dogs with CNS signs in T. cruzi-endemic areas.

Nanopore Sequencing Using the Full-Length 16S rRNA Gene for Detection of Blood-Borne Bacteria in Dogs Reveals a Novel Species of Hemotropic Mycoplasma

Dogs across the globe are afflicted by diverse blood- and vector-borne bacteria (VBB), many of which cause severe disease and can be fatal. Diagnosis of VBB infections can be challenging due to the low concentration of bacteria in the blood, the frequent occurrence of coinfections, and the wide range of known, emerging, and potentially novel VBB species encounterable. Therefore, there is a need for diagnostics that address these challenges by being both sensitive and capable of detecting all VBB simultaneously. We detail the first employment of a nanopore-based sequencing methodology conducted on the Oxford Nanopore Technologies (ONT) MinION device to accurately elucidate the "hemobacteriome" from canine blood through sequencing of the full-length 16S rRNA gene. We detected a diverse range of important canine VBB, including Ehrlichia canis, Anaplasma platys, Mycoplasma haemocanis, Bartonella clarridgeiae, "Candidatus Mycoplasma haematoparvum", a novel species of hemotropic mycoplasma, and Wolbachia endosymbionts of filarial worms, indicative of filariasis. Our nanopore-based protocol was equivalent in sensitivity to both quantitative PCR (qPCR) and Illumina sequencing when benchmarked against these methods, achieving high agreement as defined by the kappa statistics (k > 0.81) for three key VBB. Utilizing the ability of the ONT' MinION device to sequence long read lengths provides an excellent alternative diagnostic method by which the hemobacteriome can be accurately characterized to the species level in a way previously unachievable using short reads. We envision our method to be translatable to multiple contexts, such as the detection of VBB in other vertebrate hosts, including humans, while the small size of the MinION device is highly amenable to field use. IMPORTANCE Blood- and vector-borne bacteria (VBB) can cause severe pathology and even be lethal for dogs in many regions across the globe. Accurate characterization of all the bacterial pathogens infecting a canine host is critical, as coinfections are common and emerging and novel pathogens that may go undetected by traditional diagnostics frequently arise. Deep sequencing using devices from Oxford Nanopore Technologies (ONT) provides a solution, as the long read lengths achievable provide species-level taxonomic identification of pathogens that previous short-read technologies could not accomplish. We developed a protocol using ONT' MinION sequencer to accurately detect and classify a wide spectrum of VBB from canine blood at a sensitivity comparable to that of regularly used diagnostics, such as qPCR. This protocol demonstrates great potential for use in biosurveillance and biosecurity operations for the detection of VBB in a range of vertebrate hosts, while the MinION sequencer's portability allows this method to be used easily in the field.

Vector-borne pathogens of zoonotic concern in hunting dogs of southern Italy

Dogs are commonly exposed to vector-borne pathogens (VBPs), yet few data are available on hunting dogs, which are often at high risk of infection due to their involvement in field activities. To investigate the occurrence of VBPs and evaluate the relative performance of different diagnostic tools, blood and serum samples were collected from hunting dogs (n = 1,433) in rural areas of southern Italy. All samples were tested by Knott's technique for filarioids, serologically (SNAP® 4Dx® Plus) for Anaplasma spp., Borrelia burgdorferi sensu lato, Dirofilaria immitis and Ehrlichia spp. and molecularly (qPCR) for all except B. burgdorferi of the above pathogens plus Babesia spp. and Leishmania infantum. Logistic regression was run to evaluate the statistical associations between the risk of VBP infection and independent variables (such as geographic area of provenience, age class and sex) and K-Cohen formula for assessing the concordance among diagnostic tests. Overall, out of 321 dogs (22.4%) positive to at least one VBP, 28 (1.9%) were infected by filarial species at the Knott's technique. In particular, Acanthocheilonema reconditum was the most prevalent (1.6%), followed by D. immitis (0.2%) and Dirofilaria repens (0.1%). One hundred forty (9.8%) and 231 (16.1%) dogs scored positive to VBPs by serological and molecular methods, respectively. The most prevalent pathogens detected were Ehrlichia spp. (7.3%) with SNAP® 4Dx® Plus, and A. reconditum (7.7%) by qPCR. Statistics revealed a significant association (p < 0.001) between A. reconditum infestation and both Ehrlichia spp. seropositivity and geographical origin of dogs. An agreement of 99.9%, 94.0% and 95.7% for Knott - SNAP® 4Dx® Plus, Knott - qPCR and SNAP® 4Dx® Plus - qPCR for D. immitis was found, respectively. Data demonstrate a high prevalence of VBPs in hunting dogs, indicating that this group of animals is largely exposed to several arthropod vector species and suggesting the transmission risk of pathogens to humans in rural areas of southern Italy. A multi-diagnostic approach and a deeper cooperation among healthcare and stakeholders are required to prevent VBP infections to animals and humans.

Infections and Coinfections by Trypanosomatid Parasites in a Rural Community of Venezuela

INTRODUCTION

Trypanosoma cruzi, Trypanosoma rangeli and Leishmania spp. are parasites that coexist in several endemic areas. The identification of these parasites in hosts is important for the control programs.

METHODS

216 samples from human blood (101), blood of other mammals (45) and triatomine intestinal content and hemolymph (70), from an endemic area of Venezuela, were analysed. The samples were evaluated by; serology (only humans) and PCR for T. cruzi in human, other mammals and triatomines, PCR for T. rangeli in mammals-including human and triatomines and PCR for Leishmania in mammals-including human.

RESULTS

The 9.9% of the human samples were positive for T. cruzi by serology, 11.9% by PCR, 4% for T. rangeli PCR and none for Leishmania spp. PCR. 60% of the samples of other mammals showed DNA amplification for T. cruzi, 42.2% for T. rangeli and 4.4% for Leishmania spp. 61.4% of the triatomine samples showed DNA amplification for T. cruzi and 10% for T. rangeli.

CONCLUSIONS

High T. cruzi infection was detected in mammals and triatomines compared with T. rangeli. Low leishmanial infection was detected in other mammals. It is the first time that T. cruzi/T. rangeli coinfection, in humans, Canis familiaris (dog), and Bos Taurus (cow), were reported world-wide, and that this coinfection was described in Tamandua tetradactyla (anteater) from Venezuela. The coinfection T. cruzi/T. rangeli in mammals-including humans and triatomines, and coinfection T. cruzi/Leishmania spp. in non-human mammals, show the risk for trypanosomic zoonoses in this endemic area.

Tick-Borne Pathogens, Babesia spp. and Borrelia burgdorferi s.l., in Sled and Companion Dogs from Central and North-Eastern Europe

Ticks are important vectors of numerous pathogens of medical and veterinary significance. The aim of the current study was to determine the prevalence of Babesia spp. and Borrelia burgdorferi s.l. in sled and pet dogs from Central and North-Eastern Europe. Neither Babesia spp. nor Borrelia burgdorferi s.l. infections were detected in sled dogs from seven countries (Poland, Lithuania, Latvia, Estonia, Belarus, Russia and Finland). The DNA of Babesia spp. was detected in 100% of symptomatic and 5.4% of asymptomatic pet dogs from Poland. Similarly, the DNA of Babesia spp. was identified in 82% of symptomatic and 3.8% of asymptomatic pet dogs from Ukraine. The DNA of Borrelia burgdorferi s.l. was detected in 4.4% of pet dogs. Molecular typing confirmed the presence of Babesia canis and Borrelia burgdorferi sensu stricto (s.s.) in selected samples. Four dogs were co-infected by B. canis and Borrelia burgdorferi s.l. Tick-borne pathogens constitute a serious health threat to pet dogs in Central and South-Eastern Europe, but were not observed among sled dogs from the same region of Europe nor in the Baltic countries.