DETECTION OF VECTOR-BORNE INFECTIONS IN LIONS AND TIGERS AT TWO ZOOS IN TENNESSEE AND OKLAHOMA, USA.

Protozoal and bacterial vector-borne infections are frequently diagnosed in domestic felids. However, with the exception of Mycoplasma haemofelis and Cytauxzoon felis, their occurrence in managed nondomestic felids housed in the United States is largely unknown. Following a case in February 2020 of fulminant cytauxzoonosis in an African lion (Panthera leo), EDTA-whole blood samples were collected opportunistically from February 2020 through June 2020 from 34 adult tigers (Panthera tigris) and eight adult African lions from the same sanctuary in eastern Tennessee as well as 14 adult tigers from a zoo in southern Oklahoma. Samples were analyzed for Cytauxzoon felis, Bartonella spp., hemotropic Mycoplasma, Rickettsia spp., Anaplasma spp., Ehrlichia spp., Babesia spp., and Hepatozoon spp. DNA by PCR amplification. All animals were asymptomatic at the time of collection. None of the Oklahoma animals were positive for vector-borne organisms, but these pathogens were detected in tigers at the Tennessee facility, including Cytauxzoon felis (11.8%), "Candidatus Mycoplasma haemominutum" (5.9%), and Ehrlichia ewingii (2.9%). During the study period, two animals developed clinical signs of cytauxzoonosis and were assessed for vector-borne infections as part of their diagnostic evaluation. This study documents the presence of tick-borne diseases in managed nondomestic felids in the southeastern United States and underscores that ectoparasite control measures should be practiced to minimize exposure of carnivores in managed care.

Novel Rickettsia Species Infecting Dogs, United States.

In 2018 and 2019, spotted fever was suspected in 3 dogs in 3 US states. The dogs had fever and hematological abnormalities; blood samples were Rickettsia seroreactive. Identical Rickettsia DNA sequences were amplified from the samples. Multilocus phylogenetic analysis showed the dogs were infected with a novel Rickettsia species related to human Rickettsia pathogens.

MOLECULAR PREVALENCE OF SELECTED VECTOR-BORNE ORGANISMS IN CAPTIVE RED WOLVES (CANIS RUFUS).

The red wolf (Canis rufus) is a critically endangered North American canid, with surviving conspecifics divided between a captive breeding population and a reintroduced free-ranging population. The goal of this study was to assess the prevalence of selected vector-borne pathogens in captive red wolves. Whole blood samples were collected from 35 captive red wolves. Quantitative polymerase chain reaction (PCR) assays were performed on extracted DNA to identify infection by Trypanosoma cruzi and vector-borne organisms within the following genera: Anaplasma, Babesia, Bartonella, Ehrlichia, Mycoplasma, Neoehrlichia, Neorickettsia, and Rickettsia. All red wolves sampled were PCR-negative for all tested organisms. These pathogens are unlikely to constitute threats to red wolf conservation and breeding efforts under current captive management conditions. The results of this study establish a baseline that may facilitate ongoing disease monitoring in this species.

Potentially novel Ehrlichia species in horses, Nicaragua.

Ehrlichia sp. DNA was amplified from 4 Ehrlichia-seroreactive horses from Mérida, Nicaragua. Sequencing of 16S rDNA, sodB, and groEL genes indicated that the bacterium is most likely a novel Ehrlichia species. The tick vector and the potential for canine and human infection remain unknown.

Development and validation of a sensitive and specific sodB-based quantitative PCR assay for molecular detection of Ehrlichia species.

We developed a sensitive and specific sodB-based quantitative PCR assay to detect Ehrlichia spp. The assay's limit of detection was 5 copies/reaction, and it did not amplify nonspecific DNA. Compared with a 16S rRNA gene PCR target, the sodB target may offer an improved molecular diagnostic assay to detect Ehrlichia spp.

Detection of Anaplasma phagocytophilum in an inflammatory pericardial effusion of a dog.

An 11-year-old female spayed German Wirehaired Pointer with a 1-week history of lethargy, hyporexia, diarrhea, and coughing presented with pericardial effusion causing cardiac tamponade. An echocardiogram revealed no structural cause for pericardial effusion. The pericardial effusion was an exudate with mixed macrophagic and neutrophilic inflammation. Morulae occasionally were found within neutrophils. The pericardial fluid and blood were qPCR and cPCR positive for Anaplasma phagocytophilum (NC State University, Vector-borne Disease Diagnostic Laboratory, Raleigh, NC). The dog's blood was negative by ELISA (Vetscan Flex4 Rapid Test, Zoetis, Parsippany, NJ) for A. phagocytophilum antibodies at initial presentation and subsequently positive (SNAP4DxPlus, IDEXX, Westbrook, ME) 7 days later. After pericardiocentesis and administration of doxycycline (5 mg/kg PO q12h for 14 days), a repeat echocardiogram performed 1 month later showed no recurrence of pericardial effusion.

Evaluation of the Veterinary IDEXX SNAP 4Dx Plus Test for the Diagnosis of Lyme Disease in Humans.

Background: Lyme disease, caused by infection with Borrelia burgdorferi, is the most common vector-borne disease in the United States. The standard two-tier testing (STTT) algorithm suffers from low sensitivity, misinterpretation, and long turnaround time, preventing timely detection and treatment. To address these challenges, we hypothesized that the canine point-of-care (PoC) SNAP 4Dx Plus test used to detect Borrelia burgdorferi antibodies could be employed for human diagnosis. Materials and Methods: The SNAP 4Dx Plus testing was conducted in accordance with the manufacturer's instructions, with results read by manual inspection. All analyses were conducted using R version 4.3.1, and agreement between the PoC assay and the STTT was assessed using kappa statistics with GraphPad software. Results: We included 102 previously-tested human serum samples, of which 19 samples (18.6%) were STTT positive. Compared to the STTT, the SNAP 4Dx Plus test demonstrated a low sensitivity of 0.16 (95% CI 0.03 to 0.40). Conclusion: Overall, our results do not support the use of the SNAP 4Dx Plus LD assay for the diagnosis of human Lyme disease. Differences in antibody concentrations between human and canine samples may partly explain our findings.

First reported case of leishmaniasis in a cat in Trinidad and Tobago.

A 3-year-old, female, domestic shorthair cat, was presented to the Veterinary Teaching Hospital at the School of Veterinary Medicine (SVM), Trinidad and Tobago for a swollen nose, and multiple, variably sized small masses on both ears. The initial diagnostic tests included a CBC, serum biochemistry profile, cytological evaluation of masses on the ear and nose, and FeLV/FIV testing. The CBC and biochemistry results were unremarkable except for a hyperproteinaemia and hyperglobulinemia. Cytology of the nose and ear lesions revealed mixed inflammation and high numbers of intracellular and extracellular organisms consistent with Leishmania amastigotes. The cat was FeLV/FIV negative. Histopathology and Leishmania IFA and PCR analysis were subsequently performed, confirming the Leishmania diagnosis. The PCR, DNA sequencing and phylogenetic tree analyses identified L. amazonensis. This is the first reported case of L. amazonensis infection in a domestic animal in Trinidad with molecular characterization indicating it exists in the region and is likely being transmitted by sandflies.

A second-generation, point-of-care immunoassay provided improved detection of Anaplasma and Ehrlichia antibodies in PCR-positive dogs naturally infected with Anaplasma or Ehrlichia species.

A validated second-generation SNAP 4Dx Plus (Idexx) incorporates new peptides for improved detection of antibodies against Anaplasma and Ehrlichia tick-borne pathogens in dogs. We compared the first- and second-generation SNAP 4Dx Plus using dogs naturally infected with Anaplasma or Ehrlichia species, or dogs seroreactive by an E. canis indirect fluorescent antibody test (IFAT). The second-generation immunoassay was more sensitive than the first-generation for dogs infected with A. phagocytophilum (51.1% and 29.2%, respectively), A. platys (63.6% and 35.3%, respectively), E. canis (96.2% and 88.3%, respectively), or E. ewingii (73.7% and 70.8%, respectively), and for dogs seroreactive by E. canis IFAT (87.3% and 83.9%, respectively). The second-generation immunoassay detected significantly more Anaplasma- or Ehrlichia-infected dogs that were Anaplasma (p < 0.001) or Ehrlichia (p = 0.031) seroreactive, respectively, than did the first-generation test. When Ehrlichia seroreactivity by E. canis IFAT and both immunoassays was compared, significantly more E. canis-infected dogs were seroreactive by E. canis IFAT than the first-generation (p = 0.006) but not the second-generation (p = 0.125) immunoassay. Significantly more E. ewingii-infected dogs were seroreactive by the first- (p = 0.011) and second-generation (p = 0.049) immunoassays than the E. canis IFAT. Medical records available for 7 dogs that were Anaplasma seroreactive by the second-generation but not the first-generation immunoassay revealed case management decisions that might have been different with an immediate anaplasmosis diagnosis, including earlier doxycycline therapy and less hospitalization. The second-generation SNAP 4Dx Plus test offered improved serologic detection of Anaplasma and Ehrlichia in naturally infected dogs.

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.

Vector-borne disease and its relationship to hematologic abnormalities and microalbuminuria in retired racing and show-bred greyhounds.

BACKGROUND: Reference intervals for platelets and white blood cell (WBCs) counts are lower in greyhounds than other breeds. Proteinuria is common. Vector-borne diseases (VBD) cause thrombocytopenia, leukopenia, and proteinuria. Racing greyhounds are commonly exposed to vectors that carry multiple organisms capable of chronically infecting clinically healthy dogs. HYPOTHESIS/OBJECTIVES: Vector-borne disease prevalence is higher in retired racing greyhounds than in show-bred greyhounds. Occult infection contributes to breed-related laboratory abnormalities. ANIMALS: Thirty National Greyhound Association (NGA) retired racing and 28 American Kennel Club (AKC) show-bred greyhounds. METHODS: Peripheral blood was tested for Anaplasma, Babesia, Bartonella, Ehrlichia, hemotropic Mycoplasma, and Rickettsia species using PCR. Antibodies to Anaplasma, Babesia, Bartonella, Ehrlichia, and Rickettsia species and Borrelia burgdorferi were detected using immunofluorescence and ELISA assays. Complete blood counts, semiquantitative platelet estimates, and microalbuminuria concentration were determined. RESULTS: Seven of 30 NGA and 1/28 AKC greyhounds tested positive for ≥1 VBD (P = .05). More positive tests were documented in NGA (10/630) than in AKC dogs (1/588; P = .02). Exposure to Bartonella species (3/30), Babesia vogeli (2/30), Ehrlichia canis (1/30), and infection with Mycoplasma hemocanis (3/30) occurred in NGA dogs. Platelet counts or estimates were >170 000/µL. White blood cell counts <4000/µL (4/28 AKC; 5/30 NGA, P > .99; 1/8 VBD positive; 8/51 VBD negative, P = .99) and microalbuminuria (10/21 AKC; 5/26 NGA, P = .06; 1/8 VBD positive; 14/25 VBD negative, P = .41) were not associated with VBD. CONCLUSIONS AND CLINICAL IMPORTANCE: The prevalence of thrombocytopenia and B. vogeli exposure was lower than previously documented. Larger studies investigating the health impact of multiple VBD organisms are warranted.

Targeted Next-Generation Sequencing for Comprehensive Testing for Selected Vector-Borne Pathogens in Canines.

The standard for detecting vector-borne pathogens is real-time PCR (rtPCR). However, this requires many individual tests to obtain an accurate diagnosis. The purpose of this study was to develop and validate a targeted next-generation sequencing (NGS) assay for vector-borne pathogens. Pathogen target regions were amplified via PCR using two primer pools that were developed in conjunction with ThermoFisher Scientific, and barcoded DNA libraries were prepared and sequenced with the Ion Torrent S5 system. Data were assembled using SPAdes and mapped to a reference file containing sequences from the pathogens. The raw reads were analyzed to confirm the results. Test feasibility and analytical specificity were evaluated with type strains or validated positive clinical samples from dogs. The analytical sensitivity of the method was compared to Ct values obtained by rtPCR testing. Diagnostic sensitivity and specificity were assessed with a set of known positive and negative clinical samples based on rtPCR testing. Positive and negative percent agreements and Cohen's kappa were calculated. The primer sets were specific for the intended targets, based on sequence analysis of the amplified products, and the method detected 17 different pathogens. Analytical sensitivity was equivalent to an rtPCR Ct value of approximately 35-36. The positive percent agreement was 92%, and the negative percent agreement was 88%. Cohen's kappa was 0.804, which indicates almost perfect agreement between the rtPCR assays and the targeted NGS assay. Using a targeted method reduces the costs associated with NGS sequencing and allows for a 2-3 day turn-around time, making this a viable method for detection of vector-borne pathogens in canine whole blood samples.

Rickettsia typhi infection in a clinically-ill dog from Houston, Texas.

In 2020, Rickettsia typhi was diagnosed in a dog from Houston, Texas, USA based upon R. typhi IFA seroreactivity in both acute and convalescent sera, and PCR with DNA sequencing of 4 different gene regions, all of which were 100% identical to R. typhi. The dog was clinically ill with intermittent fever, lethargy, inappetence, and lymphadenopathy. Clinicopathological abnormalities included a mild nonregenerative anemia, neutrophilia, lymphopenia, thrombocytopenia, hypoalbuminemia, and elevated ALP. The dog rapidly recovered with doxycycline administration.

An Improved Point-of-Care ELISA for the Diagnosis of Anaplasmosis and Ehrlichiosis During the Acute Phase of Tick-Borne Infections in Dogs.

Veterinarians often test for serologic evidence of vector-borne infections in sick dogs presenting with clinical signs or to screen for subclinical chronic infections. Additional peptide targets for the detection of antibodies to Anaplasma phagocytophilum, Anaplasma platys, and Ehrlichia canis were added to an existing point-of-care (POC) ELISA test (SNAP 4Dx Plus Test, IDEXX Laboratories, Westbrook, ME). This second-generation, multi-analyte test detects Dirofilaria immitis antigen and antibodies to Anaplasma spp., Borrelia burgdorferi, and Ehrlichia spp. The second-generation test is expected to better meet the needs of practicing veterinarians and their patients. To assess this expectation, the second-generation POC test was evaluated with serum samples from experimentally infected dogs and a broader field population of dogs. Compared to the first-generation test, most dogs experimentally infected with A phagocytophilum (n = 7/8), A platys (n = 4/6), or E canis (n = 4/6) had detectable antibody responses 3-22 days earlier post-infection; these results demonstrated better alignment with polymerase chain reaction (PCR) amplification results and the onset of clinical signs. Using a convenience sample set of 510 sera from both academic and commercial veterinary diagnostic laboratories, the second-generation test had sensitivities greater than 90% for Anaplasma spp. (94.1%), B burgdorferi (95.5%), Ehrlichia spp. (93.4%) and D immitis (98.0%). Specificity ranged from 96.8% - 100% across the four assays. Results from this study demonstrate that the second-generation POC ELISA had an improved ability to detect serologic responses during the acute phase of A phagocytophilum, A platys, and E canis experimental infections. The results from the broader field samples support overall high sensitivity and specificity, consistent with the historical performance of the first-generation POC ELISA test.

Development of a Multiplex Droplet Digital PCR Assay for the Detection of Babesia, Bartonella, and Borrelia Species.

We describe the development, optimization, and validation of a multiplex droplet digital PCR (ddPCR) assay for the simultaneous detection of Babesia, Bartonella, and Borrelia spp. DNA from several sample matrices, including clinical blood samples from animals and humans, vectors, in-vitro infected human and animal cell lines, and tissues obtained from animal models (infected with Bartonella and/or B. burgdorferi). The multiplex ddPCR assay was able to detect 31 Bartonella, 13 Borrelia, and 24 Babesia species, including Theileria equi, T. cervi, and Cytauxzoon felis. No amplification of Treponema or Leptospira spp. was observed. Sensitivity of 0.2-5 genome equivalent DNA copies per microliter was achieved for different members of the Bartonella and Borrelia genus, depending on the species or matrix type (water or spiked blood DNA) tested. The ddPCR assay facilitated the simultaneous detection of co-infections with two and three vector-borne pathogens comprising four different genera (Babesia, Bartonella, Borrelia, and Theileria) from clinical and other sample sources.

Demographics and travel history of imported and autochthonous cases of leishmaniosis in dogs in the United States and Canada, 2006 to 2019.

BACKGROUND: Leishmania infantum infections are reported in foxhounds throughout the United States (US) and Canada, but only rarely in other dog breeds. A seroprevalence report from 2006 documented leishmaniosis in foxhounds (8.9%) tested in the US between 2000 and 2003. All other breeds were seronegative. OBJECTIVE: To reexamine demographics and travel history of L. infantum-infected dogs in the US and Canada, we hypothesize detection of L. infantum in more foxhounds than nonfoxhounds and that infected nonfoxhounds will have traveled to endemic regions. ANIMALS: A total of 125 dogs positive for L. infantum by immunofluorescent antibody, PCR, or both. METHODS: Retrospective, descriptive study of L. infantum-infected dogs between 4 January 2006 and 22 May 2019. Travel history and known lineage to foxhounds was collected from questionnaires. RESULTS: Leishmania infantum was detected in 125 (6.4%) of 1961 dogs tested between 4 January 2006 and 22 May 2019, of which 10 (8%) were foxhounds and 115 (92%) were nonfoxhound breeds. Travel history available for 69 (55%) dogs showed 60 (86.9%) dogs had traveled outside of the US or Canada. Nine (13%) dogs had not traveled outside of the US or Canada, 5 of which were nonfoxhounds. CONCLUSIONS AND CLINICAL IMPORTANCE: The majority of L. infantum cases were detected in nonfoxhounds, many of which had traveled to L. infantum-endemic countries, and several nonfoxhound breeds had no travel history. Leishmania surveillance should be considered for dogs that return from L. infantum-endemic regions to monitor emergence of this zoonotic disease in the US and Canada.

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.

Evaluation of a commercial microbial enrichment kit used prior DNA extraction to improve the molecular detection of vector-borne pathogens from naturally infected dogs.

Accurate detection of vector-borne pathogens (VBPs) is extremely important as the number of reported cases in humans and animals continues to rise in the US and abroad. Validated PCR assays are currently the cornerstone of molecular diagnostics and can achieve excellent analytical sensitivity and specificity. However, the detection of pathogens at low parasitemia still presents a challenge for VBP diagnosis, especially given the very low volume of specimens tested by molecular methods. The objective of this study is to determine if a commercially available microbial enrichment kit, used prior DNA extraction, is capable of expanding the overall microbial community and increasing detectable levels of VBPs in canine blood samples through host DNA depletion. This study used EDTA-whole blood samples from dogs naturally infected with varying parasitemia levels of either Anaplasma phagocytophilum, Babesia gibsoni, or Ehrlichia ewingii. For two VBPs, EDTA-blood samples were diluted to determine the effect of microbial concentration at low parasitemia. Paired EDTA-blood samples from each dog were subjected to traditional, automated DNA extraction with or without the microbial concentrating kit (MolYsis®) prior DNA extraction. Relative amounts of pathogen DNA in paired samples were determined by real-time PCR and Next-Generation Sequencing targeting conserved regions of 16S rRNA (for bacteria) and 18S rRNA (for protozoa). Results from the three molecular methods suggest that the microbial concentrating kit did not improve the detection of VBPs, although significantly reduced the presence of host DNA. Alternative methods for VBP enrichment in clinical samples prior to molecular testing should continue to be investigated, as it may significantly improve clinical sensitivity and reduce the number of false-negative results.

Bartonella rochalimae, a newly recognized pathogen in dogs.

BACKGROUND: Bartonella spp. comprise a genus of bacteria that frequently cause persistent, often subclinical infection. Although many Bartonella spp. have been implicated in a variety of clinical presentations, Bartonella rochalimae has yet to be documented in association with a clinical presentation other than infectious endocarditis (IE) in dogs. OBJECTIVES: To document a spectrum of clinical presentations accompanied by mild hematological abnormalities in B rochalimae-infected dogs from the United States. ANIMALS: Eight dogs with documented B rochalimae infection. METHODS: Retrospective 10-year study of B rochalimae naturally infected dogs. Clinical and clinicopathologic data, including medical history, CBC, serum biochemistry panel, urinalysis, echocardiogram, and comprehensive vector-borne disease diagnostic panel results, were reviewed. RESULTS: Eight dogs were diagnosed with B rochalimae via polymerase chain reaction (PCR) amplification. Five dogs were diagnosed with IE. Three dogs, PCR positive for B rochalimae, were diagnosed with seizures or antibiotic responsive lameness or during routine screening of a military working dog. CONCLUSIONS: This case series provides support for an association between B rochalimae and IE and provides documentation of dogs infected with B rochalimae with other clinical diagnoses.