Intraocular infestation with Thelazia callipaeda

Abstract

To the EditorIn their recently published manuscript, Kim and colleagues[1] describe a case of human intraocular infestation byworms. The authors erroneously identify the nematodecollected in the conjunctiva as Thelazia callipaeda (Spiru-rida: Thelaziidae). However, the morphological identifica-tion of T. callipaeda adult nematodes relies on evidence ofthe presence of a buccal capsule with the internal marginseverted and subdivided by excavations into six festoons andthe mouth opening with a hexagonal profile. These mor-phological features clearly differ from those of the nema-tode in the figure presented by Kim and colleagues [1]. Theauthors also state that the life cycle of T. callipaeda remainsunclear and discuss the possibility of human infectionthrough the skin or by drinking untreated water. It isimportant for physicians and ophthalmologists who may notbe experts in parasitology to realize that, similarly to othermembers of the Thelaziidae, and at a higher taxonomicallevel of the order Spirurida, T. callipaeda is transmittedonly by secretophagous flies [2]. T. callipaeda develops thefirst to third infective stages of larvae within its body andthese are then deposited into the eyes of receptive hostswhen flies feed on lachrymal secretions.The lack of knowledge of this helminth’s infestation isprobably due to the fact that, until the last decade, the bodyof literature on this nematode was published in languagesother than English (mainly Chinese) and thus it was notaccessible to a great part of the western scientific commu-nity. This nematode was commonly known as the ‘‘orientaleye-worm’’ because of its distribution in Asian countrieswhere it is still frequently reported as being responsible forthelaziosis in humans, carnivores (dogs, cats and foxes) andrabbits, causing mild to severe clinical signs (includingepiphora, conjunctivitis, keratitis and/or even cornealulcers) [2]. The little attention medical researchers tend topay human thelaziosis may also be attributable to the dif-ficulties in its clinical diagnosis and differentiation fromallergic conjunctivitis, particularly when small numbers ofadult or larval stages are present in affected patients. Overthe last decades, however, infestation by T. callipaeda hasgained the interest of the scientific community and there isevidence of its spreading throughout Europe, with a highprevalence (up to 60%) in dogs being recorded in someareas of southern Italy [2]. In the same areas the frequencyof wolves, beech martens, brown hares and wild cats asdefinitive hosts for T. callipaeda has been recently dem-onstrated. In addition, there is evidence for its occurrence indogs in France, Germany and Switzerland. Recently, thefirst four cases of human thelaziosis in Europe have alsobeen diagnosed [3]. Correct knowledge of the biology ofT. callipaeda is, therefore, pivotal in addressing the pre-vention of human thelaziosis (e.g., use of nets to protectchildren while sleeping, keeping their faces and eyes clean).Domenico OtrantoDepartment of Veterinary Public Healthand Animal SciencesFaculty of Veterinary Medicine of BariStrada Provinciale per Casamassima km 370010 Valenzano (Bari), ItalyReferences