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Thelaziosis in Humans, a Zoonotic Infection, Spain, 2011 - - Emerging Infectious Disease journal - CDC

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Thelaziosis in Humans, a Zoonotic Infection, Spain, 2011 - - Emerging Infectious Disease journal - CDC


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Thelaziosis in Humans, a Zoonotic Infection, Spain, 2011

Isabel FuentesComments to Author , Isaías Montes, Jose M. Saugar, Stefania Latrofa, Teresa Gárate, and Domenico Otranto
Author affiliations: Author affiliations: Instituto de Salud Carlos III, Madrid, Spain (I. Fuentes, J.M. Saugar, T. Gárate); Hospital Ciudad de Coria, Cáceres, Spain (I. Montes); Università degli Studi di Bari, Valenzano, Italy (S. Latrofa, D. Otranto)
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Abstract

After Thelazia callipaeda infection in dogs and cats were reported in Spain, a human case of thelaziosis in this country was reported, suggesting zoonotic transmission. The active reproductive status of this nematode in situ indicates that humans are competent hosts for this parasite.
Thelazia callipaeda (Spirurida, Thelaziidae) is a parasitic helminth transmitted by zoophilic insects of the order Diptera, family Drosophilidae, genus Phortica while feeding on ocular secretions of their hosts during summer (1,2). The parasitic first-stage larvae are ingested by the vectors along with the conjunctival secretions of infected animals; they mature into their third larval stage in 2–3 weeks; and they are released as third-stage infective larvae into the eye of a new host (2). Nematodes localize in the orbital cavity and associated tissues of canids, felids, rodents, and humans, causing mild (i.e., lacrimation, itching, exudative conjunctivitis) to severe (i.e., corneal ulceration and keratitis) signs and symptoms, if not properly treated (3,4).
T. callipaeda has long been called the oriental eyeworm, referring to its traditional distribution across eastern and southeastern Asia (i.e., China, North and South Korea, Japan, Indonesia, Thailand, and India) where infection is endemic in animals and humans (5), usually in poorer rural areas and mainly among children and the elderly. Since the first cases of canine thelaziosis identified in Europe, which were in northern Italy in 1988 (6), several studies have indicated that the disease is endemic throughout Italy (7). In recent years, thelaziosis in cats and dogs has also been reported in France, Germany, and Switzerland, highlighting the spread of the disease in Europe (8). Autochthonous cases of T. callipaeda infection among dogs have recently been reported in Spain near the western part of the country (La Vera, Cáceres); prevalence in some municipalities has reached 39.9% of dogs examined (9).
After the parasite spread among domestic and wild carnivores from Europe, the first human cases of this zoonotic disease in Italy and France were described (10). Although humans are competent hosts, they usually act as accidental-ending hosts in whom the third stage larvae can grow into adults but without epidemiologic effects on parasite transmission. This lacking of effect could be explained because humans, in contrast to animals, are likely to report symptoms and consequently have parasites removed, causing the interruption of transmission.
We report a case of human thelaziosis in Spain. This report highlights the emerging nature of this zoonotic disease and calls for attention to its possible public health consequences. In addition, the finding of a mature female parasite with developed larvae in the uterus suggests that humans may be proper hosts for T. callipaeda development in areas where thelaziosis is endemic in dogs or cats.

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