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

Filipe Dantas-Torres,Melissa J. Beall,Rossella Panarese,Roberta Iatta,Domenico Otranto,Jairo Alfonso Mendoza-Roldan,Frédéric Beugnet,Donald Szlosek,Joe Liu,Jennifer Braff

doi:10.3390/pathogens9060499

Abstract

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.

Highlights

Dirofilaria immitis and Dirofilaria repens are widespread mosquito-borne filarial worms that may infect and cause mild to severe diseases in a vast range of mammals, including dogs, cats and humans [1,2,3]
Dirofilaria immitis is the causative agent of heartworm disease (HWD), while D. repens is that of subcutaneous dirofilariosis (SCD) in dogs
The prevalence of Dirofilaria spp. in the studied sheltered dog population from a high-risk geographical area for HWD varies according to the diagnostic method employed, ranging from 44.4%

Summary

Introduction

Dirofilaria immitis and Dirofilaria repens are widespread mosquito-borne filarial worms that may infect and cause mild to severe diseases in a vast range of mammals, including dogs, cats and humans [1,2,3]. Dirofilaria immitis is the causative agent of heartworm disease (HWD), while D. repens is that of subcutaneous dirofilariosis (SCD) in dogs. Dirofilaria spp. infections in humans are oftentimes underestimated or misdiagnosed, but symptomatic cases are usually detected in areas with a high prevalence of infection in dogs [4,5]. In the last two decades, reports of clinical cases of heartworm (HW) infection in dogs have increased even in non-endemic areas with new endemic foci detected in the Mediterranean region [8,9,10].

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