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

摘要

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