Epidemiology of the eye worm Thelazia callipaeda in cats from southern Switzerland.

Thelazia callipaeda is a spiruroid nematode of dogs, cats and wild carnivores transmitted by zoophilic drosophilid Phortica flies and found in an increasing number of European countries. In cats the disease is diagnosed sporadically. This study presents an epidemiological investigation of feline thelaziosis, performed in southern Ticino, Switzerland, an endemic area for T. callipaeda. Between January 2009 and July 2011 2171 cats, having outdoor access and presenting for various reasons, were examined by in-depth eye examinations, and clinical and anamnestic data were collected. The overall prevalence of T. callipaeda in the study area was 0.8% (17/2171 cats, 95% confidence interval: 0.5-1.3%). Among cats showing ocular illness, the prevalence was 9.2% (11/120, CI: 4.7-15.8%). Cats with eye worms had no international travel history and were significantly more often diagnosed between June and December than during other months. With one exception, one single eye per cat was infested, each harboring between 1 and 10 eye worms (arithmetic mean: 2.8 per cat). One cat presented with conjunctivitis and ulcers, seven with conjunctivitis only and 3 with a mildly increased lacrimation, while 6 cats were asymptomatic. Significantly more male than female cats had eye worms and cats older than one year were overrepresented. No pure-bred cats were infested. This study confirms the establishment of this potentially zoonotic parasite in cats from the study area. Due to the clinical relevance and pain caused by the infestations, increased disease awareness and in depth eye examination for the detection of T. callipaeda in cats are recommended, even in absence of obvious clinical signs, in order to initiate appropriate anthelmintic treatment.

Emergence of canine ocular Thelaziosis caused by Thelazia callipaeda in southern Switzerland.

In Europe, Thelazia callipaeda has been reported in Italy and France in the eyes of dogs, cats and foxes and, recently, also in humans. In southern Switzerland (Ticino), the first case of T. callipaeda in a dog was detected in 2000 and because of an increasing number of dog thelaziosis, a survey in veterinary practices was carried out. A total of 106 Thelazia-positive dogs from a retrospective analysis and from ongoing cases between 2005 and 2007 as well as five positive cats were reported. For a cross-sectional study, 529 randomly selected dogs (from six veterinary practices), to which anaesthesia was given for other medical reasons, were additionally checked for the presence of adult specimens of Thelazia in 2006: 28 dogs were found positive indicating an overall prevalence of 5.3%. Thelazia-infection was furthermore diagnosed in 7 of 126 foxes (5.6%) shot in Ticino in winter 2005-2006. Affected foxes, dogs and cats originated from the same regions up to 863m of altitude. The cats and 57.9% (55/95) of the infected dogs had never crossed the Swiss border. Collected nematodes were morphologically identified as T. callipaeda, and this diagnosis was confirmed by the analysis of a part of the sequence of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1), revealing haplotype 1, the only one so far found in Europe. Animals harboured 1-23 eye worms. The most common symptoms were conjunctivitis and epiphora, while keratitis was present only in a low number of animals. Young and small sized dogs were significantly less involved than large animals and over 3 years of age. The results indicate that thelaziosis is endemic in that area.