Statistics from Altmetric.com
Editor,—In its normal life cycle, Theromyzon tessulatum (duck leech) enters the nasal cavities of waterfowl to suck blood, staying in its host for hours up to days. Infestation of the human eye is very rare and may be classified as a zoonosis. To our knowledge only one case is described in the literature.1
A 4 year old girl bathed in a flooded gravel pit located in the western part of Freiburg (southwest Germany) for approximately 15 minutes; occasionally she had put her head under the surface of the water. Within 15 minutes after the girl had left the water, her father found a black coloured, oval shaped animal of about 10 mm length and of soft consistency at the temporal part of her right eye. His attempts to remove the animal were unsuccessful. In the eye hospital of Freiburg University the animal was found to be adherent to the temporal bulbar conjunctiva of the girl’s right eye (Fig 1) and provisionally identified as a leech. After amethocaine (Tetracaine) eye drops were instilled into the eye, the animal could be removed. It fell down on to the right cheek, from where it was pulled off. Minor subconjunctival bleeding, but no conjunctivitis, occurred at the affected part of the conjunctiva. Dexpanthenol eye drops were instilled repeatedly. On the following day, no conjunctival injection was seen. The presumptive leech was later identified by a parasitologist (AK) as the duck leech Theromyzon tessulatum, a species which is common in the central and western part of Europe (Fig2).
In wild mallard ducks (Anas platyrhynchos) and wild coots (Fulica atra), which were shot by hunters in the state of Baden-Württemberg (southwest Germany), up to three specimens ofTh tessulatum have been found in their nasal cavities.2 A report from Britain deals with the infestation of both young and adult waterfowl, which showed signs of conjunctivitis associated with a watery ocular discharge. On postmortem examination, leeches were found in the conjunctival sacs. Sometimes there was haemorrhage from the external nares caused by parasites in the nasal cavities and sinuses, which on at least one occasion were present in sufficient numbers to cause asphyxia.3
Infestation of the eyes of four domestic geese was also reported in the former East Germany, the leeches numbered from seven to 19 specimens per host. In these cases, Th tessulatum stuck to all parts of the conjunctiva, especially on the membrana nictitans causing haemorrhagic inflammation of the mucous membranes, oedema, and watery ocular discharge.4 Christiansen observed minor bleeding of the pale conjunctiva and mucous purulent exudate, as well as a diffuse corneal opacity with disseminated whitish dots in a domestic goose in Denmark, whose eyes, nasal and buccal cavities were infested withTh tessulatum.5
In our case, as well as in the report of Pawlowski,1 the conjunctiva showed minor bleeding, which resulted from the bite of the leech. Conjunctivitis was not observed in the human cases, which may be due to the short time of attachment by each leech.