Human Thelaziasis, Europe

Domenico Otranto; Moreno Dutto

Disclosures

Emerging Infectious Diseases. 2008;14(4):647-649. 

In This Article

Abstract and Introduction

Thelazia callipaeda eyeworm is a nematode transmitted by drosophilid flies to carnivores in Europe. It has also been reported in the Far East in humans. We report T. callipaeda infection in 4 human patients in Italy and France.

Nematodes transmitted by arthropods may cause diseases of different severity, especially in developing countries.[1] Among these nematodes, Thelazia callipaeda Railliet and Henry, 1910 (Spirurida, Thelaziidae) has received little attention. Commonly referred to as eyeworm, it infects orbital cavities and associated tissues of humans, carnivores (i.e., dogs, cats, and foxes), and rabbits.[2] Because of its distribution in the former Soviet Union and in countries in the Far East, including the People's Republic of China, South Korea, Japan, Indonesia, Thailand, Taiwan, and India[2] it has been known as oriental eyeworm. T. callipaeda infection is endemic in poor communities in Asia, particularly in China,[3] where it is frequently reported as being responsible for human thelaziasis with mild to severe symptoms (including lacrimation, epiphora, conjunctivitis, keratitis, and corneal ulcers).[4]

A second species, T. californiensis Price, 1930, has been reported to infect humans in the United States.[2] Infective third-stage larvae of eyeworm are transmitted by insects that feed on lacrimal secretions of infected animals and humans that contain Thelazia spp. first-stage larvae. In the vector T. callipaeda, first-stage larvae undergo 3 molts (~14-21 days), and infective third-stage larvae may be transmitted to a new receptive host and develop into the adult stage in ocular cavities within ~35 days.[5] Competence of drosophilid flies of the genus Phortica as vectors of T. callipaeda has been recently demonstrated.[6,7,8]

Ocular infection of carnivores by T. callipaeda has been reported in France.[9] This infection is also common in dogs (Figure 1) and cats in Italy.[10] Imported carnivore cases of thelaziasis have also been reported in Germany, the Netherlands, and Switzerland.[11] The number of case reports of human thelaziasis has increased in several areas of Asia,[3] where it occurs predominantly in rural communities with poor living and socioeconomic standards and mainly affects the elderly and children. In spite of increasing reports of T. callipaeda infection in carnivores in different European countries, no human cases have been described. Thus, infection with this eyeworm is unknown to most physicians and ophthalmologists.

Massive Thelazia callipaeda eye infection in a dog.

We report autochthonous cases of human thelaziasis in Europe. We sought to raise awareness in the scientific community of the risk for disease caused by this parasite and the need to include this infection in the differential diagnosis of ocular diseases.

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