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Table 7 Reported length and width measurements of microfilaria of Dirofilaria immitis, D. repensa, Acanthocheilonema reconditum, and A. dracunculoidesa recovered by modified Knott (formalin fixed)

From: Prime detection of Dirofilaria immitis: understanding the influence of blocked antigen on heartworm test performance

Measurement (μm) Dirofilaria immitis Dirofilaria repens a Acanthocheilonema reconditum Acanthocheilonema dracunculoides a Reference
Length 295–325 268–360 250–288 189–230 [39]
  290–330 300–360 260–283 190–247 [42]
  295–308 359–380 259–270 253–266 [43]
  307–332 360 246–292 ~ 300 [45]
  231–288b 302–344b NR NR [46]
  ≥ 315 NR < 290 < 290 [68]
  280–320 NR 215–270 NR [69]
Width 5.0–7.5 5.0–8.0 4.5–5.5 5.0–6.0 [39]
  5.0–7.0 6.0–8.0 4.0 4.0–6.5 [42]
  6.0–6.6 8.3–9.5 4.1–5.1 4.6–5.6 [43]
  6.8 12.0 4.7–5.8 NR [45]
  6.1–7.2 NR 4.7–5.8 NR [69]
  6.0–7.0 NR < 5.6 NR [70]
  1. aAutochthonous infections not documented to occur in North America
  2. bMicrofilaria recovered by thick smear (methanol fixed)