SKIN AND EYE PARASITES
NEMATODA Order: Filariata

DIROFILARIA spp.


 

diro4-ic

A 51-year-old farmer from the Po river valley (norwestern Italy)
presented to the hospital after 2 days of pain in the right eye
with redness and blurring of vision.
Excision of a whitish, motile mass, 5 mm of diameter,
located under the bulbar conjunctiva,
( Fig. 1 ) yielded a 95 x 0.45 mm roundworm ( Fig.  2  ).
Microscopical characteristics under low-power magnification were
consistent with a nematode belonging to the genus Dirofilaria,
while H-E stained sections ( Figure  3  and  4  ),
lead to the identification of an adult female of Dirofilaria repens.
Subcutaneous, ocular and pulmonary dirofilariasis,
due to immature adults of either D.repens or D.immitis
(the latter often causing solitary lung nodules)
has been reported in humid temperate regions of both emispheres.
Transmission occurs through the bite of Aedes, Culex or Anopheles mosquitoes,
carrying infective larvae acquired from microfilariae-rich blood of animal hosts,
parasitized with either deep-seated (dog's heartworm: D.immitis),
or subcutaneous worms (D.repens in dogs and cats, D. tenuis in raccoons in the USA).
Microfilaraemia has never been reported in humans; eosinophilia occurs
in less than 15% of cases with D.immitis, and rarely with D.repens.
Figure 1: clinical presentation of subconjunctival worm (arrows)
before excision and removal.

diro5-ic

Figure 2: excised worm before lactophenol treatment (scale in cm).

diro6-ic

Figure 3: Hematoxylin-Eosin stained longitudinal section of the worm,
showing the thick multilayered cuticle and the muscle cell layer.

diro7-ic

Figure 4: Hematoxylin-Eosin stained longitudinal section of the worm,
showing the organs in the pseudocoelon.