Musca domestica is not a vector of Thelazia callipaeda in experimental or natural conditions

Abstract

Thelazia callipaeda Railliet and Henry (Spirurida: Thelaziidae), commonly called oriental eyeworm for its widespread presence in the Far East, has been recently found to affect dogs, cats and foxes in northern and southern Italy. Although the biology of T. callipaeda in the definitive hosts has been recently investigated, many doubts still remain about its biology in insect vectors. It has been suggested that more than one species of Diptera, namely Musca domestica Linnaeus (Diptera: Muscidae) and Amiota okadai Maca (Diptera: Drosophilidae), may be involved in the transmission of T. callipaeda in China. The aim of the work described here was to verify the role of M. domestica as a vector of T. callipaeda both in experimental and natural conditions. A total of 310 m. domestica (Group 1) were put in a cage and allowed to feed for 14 days around the eyes of a dog naturally infected by T. callipaeda. Ten flies were collected daily for 14 days. A total of 149 houseflies (Group 2) were fed with T. callipaeda first stage larvae (L1) and dissected at 1, 2 and 7 days post-infection. From June to August 2003, flies were netted (Group 3) in two different sites every 10 days both from the environment and directly from the periocular region of dogs affected by thelaziosis. Musca flies were examined for eyeworms by dissection and visual inspection of house flies (Groups 1 and 2) and using a molecular approach (Groups 1-3) via a specific amplification of the ribosomal internal transcribed spacer 1 (ITS1) sequence of T. callipaeda. On the whole, 180 pools of M. domestica flies were processed molecularly and all the experimentally infected flies (Groups 1 and 2) were found to be negative both at the visual dissection and at the molecular assay. Similarly, the 234 M. domestica collected from Group 3 were negative for T. callipaeda. The results clearly suggest that M. domestica is unlikely to act as a vector of T. callipaeda in southern Europe, in contrast with a single previous report.

Identification of the intermediate hosts of Habronema microstoma and Habronema muscae under field conditions

“…Larvae were reared and all pupae allowed to develop until the emergence of the imagos, according to the procedures described in Otranto et al (2005). Flies that emerged from each collection were divided into four groups, which were killed as described above on post‐emergence days 0, 1, 2 and 3, respectively.…”

“…Specimens were quenched in liquid nitrogen and genomic DNA was extracted (Otranto et al , 2003, 2005) from each pool of flies using a commercial kit (DNeasy Tissue Kit; Qiagen GmbH, Hilden, Germany) and stored at 4°C.…”

Thelazia Callipaeda and Eye Infections

“…It has been suggested that more than one species of Diptera, namely Musca domestica Linnaeus (Diptera: Muscidae) and Amiot okadai Maca (Diptera: Drosophilidae), may be involved in the transmission of T. callipaeda; however, so far, this was not proved in research conducted in experimental and natural conditions (12). …”

“…In France, ocular infections of carnivorous T. callipaeda have been reported (9). This infection is also common in dogs and cats in Italy (12)(13)(14). Several studies have shown that the disease is endemic throughout Italy (13,14).…”

“…Therefore, in the European countries in which this zoonosis has been described, also the cases of human infection of T. callipaeda have been reported. Most often it is in Italy and France (9,(12)(13)(14).…”