Performance of the Angio Detect™ in-clinic test kit for detection of Angiostrongylus vasorum infection in dog samples from Europe

Clinical bleeding diathesis, laboratory haemostatic aberrations and survival in dogs infected with Angiostrongylus vasorum: 180 cases (2005-2019)

OBJECTIVES

Bleeding diathesis is a complication in dogs infected with Angiostrongylus vasorum. This retrospective study investigated clinical and laboratory haemostatic differences in A. vasorum-positive dogs with and without signs of bleeding and impact of bleeding on survival.

MATERIALS AND METHODS

Demographics, type of clinical bleeding, haematocrit and a range of haemostatic tests, including thromboelastography and derived velocity curves were retrospectively registered from A. vasorum-positive dogs. All parameters were compared between dogs with and without signs of bleeding using univariable analyses. Binomial and multinomial regression models were applied to examine specific indicators in the bleeding dogs. P-values were false discovery rate adjusted, and adjusted P<0.05 was considered significant.

RESULTS

One hundred and eighty dogs entered the study, including 65 dogs (36.1%) presenting with bleeding diathesis. Different types of cutaneous and mucosal bleeding were the most common clinical findings. Twenty dogs presented with neurological signs associated with intracranial and intra-spinal bleeding. One hundred and thirty-seven dogs had haematological and/or haemostatic laboratory analyses performed. Haematocrit, platelet count, thromboelastographic angle, maximum amplitude, global clot strength, maximum rate of thrombin generation and total thrombin generation were decreased, while prothrombin time was prolonged in bleeding dogs. Survival rate of bleeding dogs was lower at hospital discharge (76.9%) and 1 month after diagnosis (66.0%) than in dogs without signs of bleeding (94.8% and 90.1% at discharge and at 1 month, respectively).

CLINICAL SIGNIFICANCE

Several haemostatic aberrations were detected in A. vasorum-positive dogs with bleeding diathesis. Bleeding was identified as an important negative prognostic indicator in A. vasorum-positive dogs.

Control line failure in Angiostrongylus vasorum point-of-care serology test in dogs with angiostrongylosis due to suspected hook effect

OBJECTIVES

Angiostrongylosis is a significant differential for a diverse range of clinical signs in dogs, many of whom present acutely and sometimes with fatal consequences. Point-of-care diagnostic assays include a commercially available Angiostrongylus vasorum qualitative direct lateral flow assay.

MATERIALS AND METHODS

Case records from one referral centre from dogs with an invalid A. vasorum lateral flow assay, comprising an absent control line alongside a visible test line, were reviewed. As control line failure was hypothesised to be due to antigen excess; where available the A. vasorum lateral flow assay was repeated using dilutions of the original serum.

RESULTS

Six dogs had an invalid A. vasorum lateral flow assay result. Five dogs had presented with acute-onset, severe clinical disease consistent with angiostrongylosis, and one dog was a clinically healthy in-contact. Clinical suspicion of angiostrongylosis was confirmed using alternative diagnostic testing and/or response to treatment. Repetition of the A. vasorum lateral flow assay, in four cases, using diluted plasma (10% to 12.5% v/v) resulted in the appearance of a control line alongside the visible test line.

CLINICAL SIGNIFICANCE

A heavy burden of A. vasorum infection resulting in angiostrongylosis should be suspected in dogs with compatible clinical signs and an invalid A. vasorum lateral flow assay result due to control failure alongside a visible test line. Repetition of the test with a diluted serum may be considered to account for the hook effect, also known as the postzone phenomenon, as a possible cause.

Hemostatic Dysfunction in Dogs Naturally Infected with Angiostrongylus vasorum—A Narrative Review

This narrative review aims to describe Angiostrongylus vasorum-induced hemostatic dysfunction of dogs with emphasis on clinical and laboratory findings as well as potential therapeutic strategies for the bleeding patient. Canine angiostrongylosis (CA) is a disease with potentially high morbidity and mortality in endemic areas and with fatal outcome often associated with either severe respiratory compromise, pulmonary hypertension and right-sided heart failure, or hemostatic dysfunction with severe bleeding. The most common signs of hemorrhage are hematomas, petecchiation, ecchymoses, oral mucosal membrane bleeding and scleral bleeding, while intracranial and pulmonary hemorrhage are among the most severe. The pathophysiological mechanisms underlying hemostatic dysfunction in these patients are presently researched. While the larval effect on platelets remains unknown, the parasite appears to induce dysregulation of hemostatic proteins, with studies suggesting a mixture of pro-coagulant protein consumption and hyperfibrinolysis. Importantly, not all dogs display the same hemostatic abnormalities. Consequently, characterizing the hemostatic state of the individual patient is necessary, but has proven difficult with traditional coagulation tests. Global viscoelastic testing shows promise, but has limited availability in general practice. Treatment of A. vasorum-infected dogs with hemostatic dysfunction relies on anthelmintic treatment as well as therapy directed at the individual dog’s specific hemostatic alterations.

Angiostrongylus vasorum in Domestic Dogs in Castilla y León, Iberian Peninsula, Spain

Simple Summary

Canine angiostrongylosis is a vascular and pulmonary disease caused by Angiostrongylus vasorum. In Europe, there has been an increasing number of studies showing a rise in the studies in both domestic and wild canids. In Spain, angiostrongylosis is still little-known, and studies are scarce. The aim of this study was to analyze the presence of A. vasorum in 1475 domestic dogs from the autonomous region of Castilla y León (Spain). Antigens of this species were found in 0.75% of the tested dogs, most of which lived outdoors, a significant risk factor. The geographic information system (GIS) analysis showed that the infected animals mainly lived in areas with mild temperatures and climate during most of the year and close to water bodies: stagnant water; riverbanks or irrigated areas with a predominance of alder, holm oak and gall oak forests. One main conclusion was the need to carry out more studies in countries and areas with the presence of this parasite in order to know the prevalence in dogs and wild canids, as well as determine the environmental factors that influence its presence, to be able to take more effective measures to control this disease.

Abstract

Angiostrongylus vasorum is the causative agent of canine angiostrongylosis, a disease affecting domestic and wild canids. In Europe, it is an emerging disease, mainly reported in red foxes. In Spain, there are a few studies that address the prevalence and pathology of this disease. Castilla y León is the largest region of the Iberian Peninsula, whose extensive area is 94,224 km²; however, until now, there have been no epidemiological studies on this disease. Therefore, the aim of this study was to analyze the presence of antigens of A. vasorum in 1475 dogs from Castilla y León, showing an overall prevalence of 0.75%. The infected dogs were mainly outdoors, guard and hunting breed dogs and living in locations with mild climates close to areas of high edaphic humidity, such as stagnant water, irrigated crops or riverbanks, with the vegetation dominated by alders, holm oak and gall oak forests, where the intermediate hosts develop. It is necessary to carry out more in-depth studies on the epidemiology and pathology of this disease in Spain and Europe in order to carry out efficient control in both domestic and wild animals.

Investigation of the occurrence of Angiostrongylus vasorum in coyotes in southern Ontario, Canada

In North America, the only endemic focus for Angiostrongylus vasorum (French heartworm) was historically thought to occur in the southeastern part of the island of Newfoundland. However, reports of A. vasorum infection in wild canids in West Virginia, USA, and Nova Scotia, Canada, suggest the introduction of the parasite to mainland North America. We screened for A. vasorum in coyotes from across southern Ontario. Additionally, we evaluated the performance of ELISAs for detection of circulating A. vasorum antigen (Ag-ELISA) and antibodies against A. vasorum (Ab-ELISA) designed for use in sera or blood of foxes for use with coyotes in this region. Autopsies were performed on 397 coyotes, and lung tissue extract prepared from each carcass was tested via both ELISAs. The sensitivity and specificity for both tests were estimated in the absence of a gold standard using a 2-test single population Bayesian model; sensitivity and specificity priors were based on the performance of the assays in foxes in Switzerland. Eight coyotes tested positive for A. vasorum antigen; no animal was antibody positive. The estimated sensitivity and specificity of the Ag-ELISA were 90.8% (95% credible interval [CrI]: 83.8–95.6%) and 95.5% (95% CrI: 93.4–97.2%), respectively. For the Ab-ELISA, the estimated sensitivity and specificity were 41.9% (95% CrI: 32.1–51.9%) and 98.0% (95% CrI: 96.3–99.0%), respectively. Based on these findings and negative postmortem data for the same animals, there is insufficient evidence to suggest the presence of A. vasorum in southern Ontario coyotes.

Intra Vitam Diagnosis of Neglected Gurltia paralysans Infections in Domestic Cats (Felis catus) by a Commercial Serology Test for Canine Angiostrongylosis and Insights into Clinical and Histopathological Findings-Four-Case Report

Gurltia paralysans is a metastrongyloid nematode which belongs to the Angiostrongylidae family and presents tropism for veins of the subarachnoid space in vivo of domestic and wild felids causing a progressive and chronic clinical manifestation of paraparesis/paraplegia. The geographic distribution of G. paralysans includes rural and periurban areas of South America and was recently reported in Europe. To date, a definitive diagnosis of feline gurltiosis is still conducted by post-mortem examination of the spinal cord in affected animals. A presumptive diagnosis of feline gurltiosis can also be achieved based on data of compatible clinical signs and associated epidemiological risk factors. The aim of this preliminary study was to evaluate the commercial serological test Angio Detect TM^® (IDEXX Laboratories) as a possible diagnostic method of feline gurltiosis in vivo. For the study, 10 domestic felines (Felis catus) which originated from a high endemic area of Southern Chile, were analyzed. All felines presented chronic paraparesis or severe paraplegia. Subsequently, commercial Angio Detect TM^® serological tests for the detection of closely related Angiostrongylus vasorum in canids were performed according to manufacturer’s instructions. Conducted serological tests were positive in seven of ten felines showing paraplegia/paraparesis and presumably infected with G. paralysans, and four of them were additionally necropsied, and presented macroscopic findings compatible with feline gurltiosis. Furthermore, the presence of adult female and male G. paralysans specimens at the level of the subarachnoid vasculature in affected spinal cord segments were observed during necropsy. Histopathology demonstrated severe eosinophilic meningomyelitis, coagulopathies with thrombosis in G. paralysans-parasitized leptomeningeal veins. Results of this preliminary study suggest a cross-reaction between A. vasorum-specific antigens, which also parasitize blood vessels in vivo, and G. paralysans when using an Angio Detect TM^® test, which suggests its helpful use as a new diagnostic method for feline gurltiosis in live domestic felines. Additional specific antigen research will be required in order to better understand the sensitivity and specificity of A. vasorum antigens used in this test and for existing cross-reactivity with G. paralysans-derived antigens for future a suitable intra vitam immunodiagnosis of neglected feline gurltiosis.

First epidemiological survey of Angiostrongylus vasorum in domestic dogs from Spain

Background

Angiostrongylus vasorum is the causative agent of canine angiostrongylosis, a disease that mainly affects domestic dogs and other wild carnivores. In Europe, the number of infected individuals is increasing, being located in central and southern countries. In Spain, several studies have reported high prevalence of A. vasorum in wild animals. However, there are no studies addressing the current situation of the disease or its distribution in domestic dogs, and reports from veterinary personnel are very limited. Considering these facts, the objective of the present study was to evaluate the prevalence of A. vasorum in different areas of Spain.

Methods

Between November 2018 and October 2019, blood was sampled from a total of 2024 domestic dogs from six zones of Spain with a climate that favours the establishment of the disease, where all dogs included in the study lived outdoors or had regular access to areas with vegetation and none had travelled outside the study area of interest in the past year. Details about their sex and age were collected. All dogs were tested for the presence of A. vasorum circulating antigens using Angio Detect^TM.

Results

The overall prevalence of canine angiostrongylosis in the studied areas of Spain was 1.73%. No differences in overall prevalence were found between males and females, neither between age groups. Regarding eco-epidemiological areas, the highest prevalence was recorded in the zones located in the north and northwest of Spain (1.86–2.74%), which correspond to the wetter climates and most abundant vegetation, and the lowest prevalence was detected in the zones located in the center and west of Spain (0.93–0.99%).

Conclusions

Our data suggest that angiostrongylosis is present in Spain in domestic dogs where previously infected wild animals existed or where climatic conditions are favourable for the establishment of the disease.

Is Angiostrongylosis a Realistic Threat for Domestic Cats?

Three species of Angiostrongylus have been found in felids thus far, i.e., Angiostrongylus chabaudi, Angiostrongylus felineus and Angiostrongylus vasorum. Angiostrongylus chabaudi lives in the right heart and pulmonary arteries of the definitive natural host, the European wildcat (Felis silvestris), and non-patent infections have been reported in domestic cats (Felis catus). Angiostrongylus felineus, described in the Puma yaguarondi (Herpailurus yagouaroundi), has never been reported in domestic felids, while recently a non-patent infection by A. vasorum was unequivocally described in a F. catus. Nonetheless, epizootiological and clinical relevance of angiostrongylosis in domestic cats are practically unknown. This study investigated whether cases of angiostrongylosis may be missed in cats living in areas enzootic for Angiostrongylus spp. and other metastrongyloids. Overall, 100 cats that were either positive (n.50) or negative (n.50) for metastrongyloid larvae at the Baermann's test, were examined for Angiostrongylus spp. with DNA-based methods and with the serological test Angio Detect™ for circulating antigen. The PCR analysis confirmed the copromicroscopy results, where 25 cats scored positive for Aelurostrongylus abstrusus, 16 for Troglostrongylus brevior and 9 for both, while no cats were positive for Angiostrongylus-like larvae, including A. chabaudi. None of the 100 sera samples scored positive at the Angio Detect™ test. These data suggest that currently feline angiostrongylosis is a minor parasitosis for domestic cats. Nevertheless, it cannot be excluded that the epizootiological drivers which have favored the spillover of A. vasorum and T. brevior from wildlife to dogs and cats, could promote the emergence of feline angiostrongylosis, with an unpredictable health impact.

Distribution of the feline lungworm Aelurostrongylus abstrusus in the USA based on fecal testing

Objectives

The aim of this study was to compile commercial reference laboratory data over a 10-year period to determine the distribution of Aelurostrongylus abstrusus, commonly known as feline lungworm, within the USA based on widespread fecal testing in cats.

Methods

The results of 3,610,455 feline ova and parasite (O&P) zinc sulfate centrifugation fecal flotation tests performed at IDEXX Reference Laboratories in the USA from January 2008 to December 2017 were compiled and sorted for tests positive for A abstrusus larvae. The results of 3625 Baermann tests, currently considered the gold standard diagnostic for feline lungworm, were also retrieved from the same period.

Results

Of the tests performed, 4721 (0.13%) feline O&P zinc sulfate centrifugation fecal flotation tests and 75 (2.07%) of the Baermann tests conducted were positive for the presence of A abstrusus larvae. The O&P data revealed a significant association between infection status and sex, while male cats in both the O&P and Baermann data sets had a higher risk of A abstrusus infection than females. Significant variation in positive rates were observed by region and most positive cases were clustered in the Northeast, Midwest and West regions of the USA.

Conclusions and relevance

This study highlights the distribution of feline lungworm in the USA and the limitations of using current testing to diagnose this infection. The introduction of higher throughput, less labor-intensive diagnostic methods could help increase awareness of this parasite among veterinary professionals, achieve a greater understanding of epidemiological factors, and improve the care and treatment for clinically ill feline patients.

Survey-based pilot study into the chosen therapy and prophylaxis used by UK primary care veterinary surgeons against canine angiostrongylosis

Canine Angiostrongylosis (CA), a gastropod-borne parasitic infection caused by the metastrongyloid nematode Angiostrongylus vasorum, is an important cause of significant morbidity to domestic dogs across the UK as well as in other European countries. This study aimed to ascertain the frequency at which particular drugs were used by primary care practitioners in the UK for therapy against and prophylaxis for CA. Primary care veterinary clinicians were surveyed using an online questionnaire and face-to-face or telephone interviews. Eighty-six veterinary surgeons responded. The majority of practices (n = 52) included lungworm in their standard anthelmintic protocols; moxidectin was the most common drug used for prophylaxis (n = 71). Fenbendazole was the most frequently selected drug, by 45% of vets, for treatment of confirmed cases of CA despite it being unlicensed for this purpose in the UK and the absence of a clear treatment protocol. The results of this pilot study provide an initial insight into the approach taken by primary care practitioners in their approach to CA. This provides an important starting point for future studies investigating the decision-making for CA amongst UK veterinary surgeons, particularly to clarify whether in a larger cohort an unlicensed drug remains the treatment of choice. The absence of a clear protocol for fenbendazole means that treatment of dogs affected by CA may be suboptimal, increasing the risk of morbidity and mortality.