Morphometric analyses of canine blood microfilariae isolated by the Knott’s test enables Dirofilaria immitis and D. repens species-specific and Acanthocheilonema (syn. Dipetalonema) genus-specific diagnosis

Abstract

BackgroundConsidering the increasing importance of small animals travel medicine and the spread of filariae with zoonotic potential to non-endemic European areas, routine filarial diagnosis in dogs is becoming important. Dirofilaria immitis, D. repens, Acanthocheilonema dracunculoides and A. reconditum are the most common canine filarial nematodes presenting blood circulating microfilariae (mf) which can be differentiated to species level by the acid phosphatase activity patterns or by PCR. Available data on the size of the mf vary considerably in the literature. The aim of this study was to validate morphometric criteria for filarial identification in blood samples of dogs after concentration of mf with the modified Knott’s technique.MethodsMorphometric analysis of 10 mf from samples identified to species level by acid phosphatase activity and partially confirmed by PCR were performed with specimens from 377 dogs.ResultsThe mean length and width of D. immitis mf from 60 dogs were 301.77±6.29 μm and 6.30±0.26 μm, of D. repens mf from 171 dogs 369.44±10.76 μm 8.87±0.58 μm, of A. dracunculoides mf from 133 dogs 259.43±6.69 μm and 5.09±0.47 μm and of A. reconditum mf from 13 dogs 264.83±5.47 μm and 4.63±0.52 μm.For a subset of 30 samples, morphometric analysis was repeated with identical results in two laboratories. Furthermore, the size of mf concentrated and fixed by the Knott’s technique was shown to be stable over 105 days.ConclusionsThe Knott’s test enables to clearly distinguish between D. immitis, D. repens and Acanthocheilonema spp. However, due to the overlapping size ranges of A. dracunculoides and A. reconditum, biochemical or molecular methods are required to distinguish these two species.

Subcutaneous Dirofilaria repens infestation in non-descript canines

“…It is similar to those described by Ananda et al (2006). The mean length and width of microfilaria in this study accord well with those observed by Magnis et al (2013) (369.44 ± 10.76 lm 9 8.87 ± 0.58 lm) and (366.2 ± 12.1 lm 9 6.40 ± 0.3 lm) by Cringoli et al (2001).…”

Geographic distribution of canine heartworm (Dirofilaria immitis) infection in stray dogs of eastern Romania

“…Dip. ) reconditum (Magnis et al, 2013). Cardiopulmonary dirofilariosis or heartworm disease (HWD) is caused by D. immitis, which is the one of the most pathogenic parasites of dogs with an increasing distribution, possibly due to climatic changes as well as animal and human movements (Genchi et al, 2011).…”

Periodicity of Dirofilaria immitis in Longterm Infections

“…260 µm x 5 µm), and Acanthocheilonema reconditum (approx. 265 µm x 5 µm) (Magnis et al 2013). Figure 1 shows a representative D. immitis mf stained in this manner.…”