Biology:Thelazia callipaeda
| Thelazia callipaeda | |
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| Male | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Chromadorea |
| Order: | Rhabditida |
| Suborder: | Spirurida |
| Infraorder: | Spiruromorpha |
| Superfamily: | Thelazioidea |
| Family: | Thelaziidae |
| Genus: | Thelazia |
| Species: | T. callipaeda
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| Binomial name | |
| Thelazia callipaeda Railliet and Henry, 1910
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Thelazia callipaeda is a parasitic nematode, and the most common cause of thelaziasis (or eyeworm infestation) in humans, dogs and cats.[1] It was first discovered in the eyes of a dog in China in 1910.[2] By 2000, over 250 human cases had been reported in the medical literature.[3]
Morphology
The adult Thelazia callipaeda worm typically measures 5 to 20 mm in length and 250 to 800 µm in diameter. The males tend to be smaller than the females in size. In distinguishing this species from other worms, they have a distinct buccal capsule and a cuticle with spaced transverse striations giving it a ridged appearance. Adult females could also be identified by the position of their vulva which is anterior to the oesophagus-intestinal junction. The males can be distinguished by their possession of five pairs of postcloacal papillae.[4]
Hosts
In addition to humans, cats and dogs,[1] definitive hosts of T. callipaeda include the wolf (Canis lupus), raccoon dog (Nyctereutes procyonoides), red fox (Vulpes fulva), and European rabbit (Oryctolagus cuniculus). This species has been found in China , France , Germany , India , Indonesia, Italy, Japan , Korea, the Netherlands, Russia , Switzerland , Taiwan, Croatia and Thailand.[5]
Two intermediate hosts have been identified so far: Phortica variegata (Diptera: Drosophilidae) in Europe and Phortica okadai in China,[6] which feed on tears of humans and carnivores.[7] Some data suggests that only the males of A. (P.) variegata carry Thelazia callipaeda larvae, making Thelazia the only parasite species known to be spread exclusively by a male vector.[8][9]
Life cycle
The eggs of Thelazia callipaeda develop into first stage larvae (L1), in utero while the female is in the tissues in and around the eye of the definitive host.[10] The female deposits these larvae, which are still enclosed in the egg membranes, in the tears (lacrymal secretions) of the host. When a tear-feeding fly (intermediate host) feeds, it ingests the T. callipaeda larvae. Once inside the fly, the L1 larvae "hatch" from the egg membrane and penetrate the gut wall. They remain in the hemocoel (the fly's circulatory system) for 2 days, and then invade either the fat body or testes of the flies. In these tissues, the larvae develop into third stage larvae (L3). The L3 migrates to the head of the fly, and is released in or near the eye of a new host mammal when the fly feeds again. Once in the eye, eyelid, tear glands, or tear ducts of the mammalian host, the L3 larvae develop through the L4 larval stage and into adults in about 1 month. The seasonal timing of L1 and L4 larvae in the lacrymal (tear) secretions of naturally infested dogs in Italy was found to coincide with the activity of the fly vectors.[11]
Symptoms, diagnosis and treatment
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Symptoms of T. callipaeda infestation include conjunctivitis, excessive watering (lacrimation), visual impairment, and ulcers or scarring of the cornea. In some cases, the only symptom is the worm obscuring the host's vision as a "floater".[12]
Diagnosis is made by finding the adult worms in the eye or surrounding tissues. Human cases are treated by simply removing the worms. In canines, topical imidacloprid with moxidectin,[13] or milbemycin oxime (Interceptor)[14] have been recommended.
In canines, prevention against canine thelaziosis by monthly administrations of a combination of milbemycin oxime and afoxolaner has been found effective.[15]
References
- ↑ 1.0 1.1 do Vale, Beatriz; Lopes, Ana Patrícia; da Conceição Fontes, Maria; Silvestre, Mário; Cardoso, Luís; Coelho, Ana Cláudia (2020). "Systematic review on infection and disease caused by Thelazia callipaeda in Europe: 2001–2020". Parasite 27: 52. doi:10.1051/parasite/2020048. ISSN 1776-1042. PMID 32996882.
- ↑ Railliet, A.; Henry, A. (1910). "Nouvelles observations sur les Thélazies, Nématodes parasites de l'oeil". Comptes rendus des séances de la Société de biologie et de ses filiales 68: 213–216, 783–785.
- ↑ "Five cases of thelaziasis". The British Journal of Ophthalmology 84 (4): 439c–439. April 2000. doi:10.1136/bjo.84.4.439c. PMID 10777285.
- ↑ Otranto, Domenico; Eberhard, Mark (23 March 2011). "Zoonotic helminths affecting the human eye". Parasites & Vectors 4 (41): 1756-3305. doi:10.1186/1756-3305-4-41. PMID 21429191.
- ↑ "Human thelaziasis, Europe" (Free full text). Emerging Infectious Diseases 14 (4): 647–9. April 2008. doi:10.3201/eid1404.071205. PMID 18394285. PMC 2570937. https://www.cdc.gov/eid/content/14/4/647.htm.
- ↑ "Nematode biology and larval development of Thelazia callipaeda (Spirurida, Thelaziidae) in the drosophilid intermediate host in Europe and China". Parasitology 131 (Pt 6): 847–55. December 2005. doi:10.1017/S0031182005008395. PMID 16336738.
- ↑ "The zoophilic fruitfly Phortica variegata: morphology, ecology and biological niche". Medical and Veterinary Entomology 20 (4): 358–64. December 2006. doi:10.1111/j.1365-2915.2006.00643.x. PMID 17199746.
- ↑ "Phortica variegata as an intermediate host of Thelazia callipaeda under natural conditions: evidence for pathogen transmission by a male arthropod vector". International Journal for Parasitology 36 (10–11): 1167–73. September 2006. doi:10.1016/j.ijpara.2006.06.006. PMID 16842795.
- ↑ "Parasite transmission by insects: a female affair?". Trends in Parasitology 24 (3): 116–20. March 2008. doi:10.1016/j.pt.2007.12.005. PMID 18258484.
- ↑ Anderson, Roy C. (2000). "T. callipaeda Railliet and Henry, 1910". Nematode parasites of vertebrates: their development and transmission. Wallingford: CAB International. p. 405. ISBN 978-0-85199-421-5. OCLC 42080206. https://books.google.com/books?id=lEERbfsvP1EC&pg=PA405.
- ↑ "Biology of Thelazia callipaeda (Spirurida, Thelaziidae) eyeworms in naturally infected definitive hosts". Parasitology 129 (Pt 5): 627–33. November 2004. doi:10.1017/S0031182004006018. PMID 15552407.
- ↑ "Intraocular infestation with the worm, Thelazia callipaeda". The British Journal of Ophthalmology 83 (10): 1194–5. October 1999. doi:10.1136/bjo.83.10.1194a. PMID 10636646.
- ↑ "Treatment of dog thelaziosis caused by Thelazia callipaeda (Spirurida, Thelaziidae) using a topical formulation of imidacloprid 10% and moxidectin 2.5%". Veterinary Parasitology 129 (1–2): 89–93. April 2005. doi:10.1016/j.vetpar.2004.12.020. PMID 15817208.
- ↑ "Therapeutic and prophylactic efficacy of milbemycin oxime (Interceptor) against Thelazia callipaeda in naturally exposed dogs". Veterinary Parasitology 154 (3–4): 351–3. July 2008. doi:10.1016/j.vetpar.2008.03.011. PMID 18456409.
- ↑ Lebon, Wilfried; Guillot, Jacques; Álvarez, Maria-Jesús; Antonio Bazaga, José; Cortes-Dubly, Marie-Laure; Dumont, Pascal; Eberhardt, Marianne; Gómez, Héctor et al. (2019). "Prevention of canine ocular thelaziosis (Thelazia callipaeda) with a combination of milbemycin oxime and afoxolaner (Nexgard Spectra®) in endemic areas in France and Spain". Parasite 26: 1. doi:10.1051/parasite/2019001. ISSN 1776-1042. PMID 30644355.
Wikidata ☰ Q3015107 entry
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