{{Short description|Genus of roundworms}} {{Automatic_taxobox | image = Thelazia_callipaeda_female.jpg | image_caption = ''Thelazia callipaeda'' female<ref>This image is from {{cite journal |doi=10.3201/eid1404.071205 |title=Human Thelaziasis, Europe |date=2008 |last1=Otranto |first1=Domenico |last2=Dutto |first2=Moreno |journal=Emerging Infectious Diseases |volume=14 |issue=4 |pages=647–649 |pmid=18394285 |pmc=2570937 }}</ref> | taxon = Thelazia | authority = Bosc, 1819 | subdivision_ranks = Species | subdivision = See text }}
'''''Thelazia''''' is a genus of nematode worms which parasitize the eyes and associated tissues of various bird and mammal hosts, including humans.<ref>{{cite journal | pmid=15639731 | date=2005 | last1=Otranto | first1=D. | last2=Traversa | first2=D. | title=Thelazia eyeworm: An original endo- and ecto-parasitic nematode | journal=Trends in Parasitology | volume=21 | issue=1 | pages=1–4 | doi=10.1016/j.pt.2004.10.008 }}</ref><ref name="do ValeLopes2020">{{cite journal|last1=do Vale|first1=Beatriz|last2=Lopes|first2=Ana Patrícia|last3=da Conceição Fontes|first3=Maria|last4=Silvestre|first4=Mário|last5=Cardoso|first5=Luís|last6=Coelho|first6=Ana Cláudia|title=Systematic review on infection and disease caused by ''Thelazia callipaeda'' in Europe: 2001–2020|journal=Parasite|volume=27|year=2020|pages=52|issn=1776-1042|doi=10.1051/parasite/2020048|pmid= 32996882|doi-access=free|pmc=7526429}} </ref> They are often called "eyeworms", and infestation with ''Thelazia'' species is referred to as "thelaziasis" (occasionally spelled "thelaziosis"). Adults are usually found in the eyelids, tear glands, tear ducts, or the so-called "third eyelid" (nictitating membrane). Occasionally, they are found in the eyeball itself, either under the conjunctiva (the membrane that covers the white part of the eye) or in the vitreous cavity of the eyeball.<ref>{{cite journal | url=https://doi.org/10.3129/i07-167 | doi=10.3129/i07-167 | title=Thelazia callipaeda in human vitreous | date=2007 | last1=Xue | first1=Chunyan | last2=Tian | first2=Nong | last3=Huang | first3=Zhenping | journal=Canadian Journal of Ophthalmology | volume=42 | issue=6 | pages=884–885 | pmid=18059522 | doi-access=free }}</ref> All species of ''Thelazia'' for which the life cycle has been studied are transmitted by species of Diptera (flies) which do not bite, but which feed on tears.
==Representative species==
*''Thelazia anolabiata'' (Molin, 1860) ** Definitive hosts: Andean cock-of-the-rock (''Rupicola peruviana'') and many other Brazilian birds<ref>de Oliveira Rodrigues, H. (1992) "[http://memorias.ioc.fiocruz.br/pdf/Volume87/vol87(fsup1)_221-226.pdf ''Thelazia anolabiata'' (Molin, 1860) Railliet & Henry, 1910 (Nematoda: Thelazioidea), a new host record and systematic considerations]." ''Memórias do Instituto Oswaldo Cruz'' 87(Suppl 1):217-222.</ref> ** Intermediate hosts: Not known ** Distribution: South America *''Thelazia bubalis'' Ramanujachari and Alwar, 1952 ** Definitive hosts: Water buffalo ** Intermediate hosts: Not known ** Distribution: India *''Thelazia californiensis'' Price, 1930 ** Definitive hosts: Dog (''Canis familiaris''), cat (''Felis catus''), occasionally human (''Homo sapiens''), domestic sheep (''Ovis aries''), mule deer (''Odocoileus hemionus''), coyote (''Canis latrans'') and American black bear (''Ursus americanus''). ** Intermediate hosts: Lesser house fly (''Fannia canicularis'') and ''Fannia benjamini'' ** Distribution: Western North America *''Thelazia callipaeda'' Railliet & Henry, 1910 (sometimes called "Oriental eyeworm") ** Definitive hosts: Typically reported from dog (''Canis familiaris''), cat (''Felis catus''), and occasionally reported from grey wolf (''Canis lupus''), raccoon dog (''Nyctereutes procyonoides''), red fox (''Vulpes vulpes''), European rabbit (''Oryctolagus cuniculus''). Over 250 cases of ''T. callipaeda'' infestation in humans have been reported thus far.<ref>{{cite journal | pmc=1723424 | date=2000 | author1=KOYAMA Y | author2=OHIRA A | author3=KONO T | author4=YONEYAMA T | author5=SHIWAKU K | title=Five cases of thelaziasis | journal=The British Journal of Ophthalmology | volume=84 | issue=4 | page=439 | doi=10.1136/bjo.84.4.439c | pmid=10777285 }}</ref> ** Intermediate hosts: Fruit flies (''Amiota (Phortica) variegata'' in Europe, and ''Phortica okadai'' in China) ** Distribution: Asia and Europe *''Thelazia erschowi'' Oserskaja, 1931 ** Definitive hosts: Pig (''Sus domesticus'') ** Intermediate host: Not known ** Distribution: Post-Soviet states *''Thelazia gulosa'' (Railliet & Henry, 1910) ** Definitive hosts: Yak (''Bos grunniens'') and other cattle (''Bos taurus''), and rarely human (''Homo sapiens'') ** Intermediate hosts: Face fly (''Musca autumnalis'') in Europe and North America, ''Musca larvipara'' in Ukraine, ''Musca vitripennis'' in Crimea, and ''Musca amica'' in the Far East ** Distribution: Asia, Europe, and North America *''Thelazia lacrymalis'' (Gurlt, 1831) ** Definitive hosts: Horse (''Equus caballus'') and cattle (''Bos taurus'') ** Intermediate hosts: Face fly (''Musca autumnalis'') and ''Musca osiris'' ** Distribution: Asia, Europe, Middle East, North America and South America *''Thelazia leesei'' Railliet & Henry, 1910 ** Definitive hosts: Dromedary (''Camelus dromedarius'') and Bactrian camel (''Camelus bactrianus'') ** Intermediate hosts: Flies (''Musca lucidulus'') ** Distribution: Post-Soviet states and India *''Thelazia rhodesii'' (Desmarest, 1828) ** Definitive hosts: mainly bovids, cattle (''Bos taurus''), water buffalo (''Bubalus bubalis''), zebu (''Bos indicus''), bison (''Bison bonasus''), and sometimes horse (''Equus caballus''), domestic sheep (''Ovis aries''), dromedary (''Camelus dromedarius''), and goat (''Capra hircus'') ** Intermediate hosts: Face fly (''Musca autumnalis'', ''Musca larvipara'', and ''Musca sorbens'') ** Distribution: Africa, Asia, and Europe *''Thelazia skrjabini'' Erschow, 1928 ** Definitive hosts: Cattle (''Bos taurus'') and yak (''Bos grunniens'') ** Intermediate hosts: Face fly (''Musca autumnalis''), ''Musca vitripennis'', and ''Musca amica'' ** Distribution: Europe and North America
== Human infections/cases == ''Thelazia anolabiata''
Thelazia anolabiata is a spirurid nematode living in the orbits of birds which can cause lacrimation, keratitis, conjunctivitis, and corneal ulcers. This species is reported for the first time from an Andean Cock of the Rock, ''Rupicola peruviana'' (Passeriformes: Cotingidae), from a zoo in Lima, Peru. Clinical signs of keratoconjunctivitis were resolved with the treatment of ivermectin, ciprofloxacin, and an epithelium regenerator, and the host is presently in good health. The nematodes were identified using the primary characteristics used to differentiate the species of this genus as lengths of spicules and other morphologic characteristics.<ref>{{Cite journal |last1=Elias |first1=R. |last2=Mamani |first2=J. |last3=Hermoza |first3=C. |last4=Kinsella |first4=J. |date=2008-12-20 |title=First report of thelaziosis (Thelazia anolabiata) in an Andean Cock of the Rock (Rupicola peruviana) from Peru |journal=Veterinary Parasitology |volume=158 |issue=4 |pages=382–383 |doi=10.1016/j.vetpar.2008.09.016 |issn=0304-4017 |pmid=18980808}}</ref>
The eyeworm ''Thelazia californiensis'' is a spiruroid nematode. It was first described by Price in 1930, as a parasite of dogs in the western United States. ''T. Californiensis'' can infest dogs, cats, sheep, deer and other mammals and causes a disease known as thelaziasis. This is not a common disease. This eyeworm commonly parasitizes in the tear ducts and conjunctival sac of its hosts, and appears as a creamy, thin-white thread measuring slightly over a half an inch in length. The adult worms may be found in the conjunctival sac or tear ducts. The eggs or larvae can be seen when the tears or secretions are examined under the microscope. The eyeworms are most common on the Pacific Coast. Humans can become infested, but it is extremely rare and thought to be accidental. There are only a few reports of ''Thelazia californiensis'' infestation in humans.<ref>{{Cite web |title=Case 279 --Clinical Microbiology Case |url=https://path.upmc.edu/cases/case279.html |access-date=2023-12-14 |website=path.upmc.edu}}</ref>
''Thelazia callipaeda'' eye worm is a nematode transmitted by drosophilid flies not only primarily to carnivores and lagomorphs but also to humans. Only a few cases have been reported in Europe (Italy, France, and Portugal). Here, we report the first eye infection in a German patient.<ref>{{cite journal | pmc=7008349 | date=2020 | last1=Dolff | first1=S. | last2=Kehrmann | first2=J. | last3=Eisermann | first3=P. | last4=Dalbah | first4=S. | last5=Tappe | first5=D. | last6=Rating | first6=P. | title=Case Report: Thelazia callipaeda Eye Infection: The First Human Case in Germany | journal=The American Journal of Tropical Medicine and Hygiene | volume=102 | issue=2 | pages=350–351 | doi=10.4269/ajtmh.19-0483 | pmid=31912777 }}</ref>
''Thelazia gulosa''
''Thelazia gulosa'', the cattle eyeworm, was found in the left eye of a 26-year-old woman from Oregon in 2018. This case was the first-ever reported human infection from this genus.<ref>{{cite journal | pmc=5928835 | date=2018 | last1=Bradbury | first1=R. S. | last2=Breen | first2=K. V. | last3=Bonura | first3=E. M. | last4=Hoyt | first4=J. W. | last5=Bishop | first5=H. S. | title=Case Report: Conjunctival Infestation with Thelazia gulosa: A Novel Agent of Human Thelaziasis in the United States | journal=The American Journal of Tropical Medicine and Hygiene | volume=98 | issue=4 | pages=1171–1174 | doi=10.4269/ajtmh.17-0870 | pmid=29436343 }}</ref> The ten previous cases reported from the United States were caused by ''Thelazia californiensis.'' Human infections caused by ''Thelazia callipaeda'' have also been reported in Japan, China, India, Taiwan, Burma, Thailand, Korea, Indonesia, Italy, Russia, and France.
The 26-year-old woman had been practicing horsemanship in Gold Beach, Oregon, which is a region where cattle farming is common. After a few weeks, her left eye started to feel irritated followed by a sensation of a foreign object. On the eighth day of her symptoms, she found and removed a small, translucent worm from her eye. She went to a local physician, who found and removed two more worms. These worms were sent to Northwest Pathology for analysis and identification. It was then forwarded to the Center for Disease Control and Prevention (CDC) Parasitic Diseases Reference Laboratory for identification.
The next day, the woman went to an optometrist where three more worms were removed. She was sent to see an infectious disease specialist, who was able to remove a partial worm. The patient was diagnosed with parasitic infiltration of the left periocular tissues and a secondary bilateral papillary reaction of the upper and lower palpebral conjunctive. Even after multiple washouts by ophthalmologists, no more worms were seen, but the patient continued to remove additional worms from her eye. Over 20 days, a total of 14 worms were removed. Since then, the patient no longer had any symptoms and no more worms were detected.
Equine thelaziosis is a neglected vector-borne parasitic disease in modern veterinary medicine, lacking recent reports. It is transmitted by ''Musca autumnalis'', and potentially other Muscidae species, by ingesting the lachrymal secretions of its equine host. The distribution of both ''Thelazia lacrymalis'' and its intermediate hosts remains largely unknown throughout Europe, with most studies dating back 20 years. The aim of this study was to assess the presence, prevalence and distribution of ''T. lacrymalis'' in horses from Romania.<ref>{{Cite journal |last1=Cotuțiu |first1=Vlad-Dan |last2=Ionică |first2=Angela Monica |last3=Lefkaditis |first3=Menelaos |last4=Cazan |first4=Cristina Daniela |last5=Hașaș |first5=Alina Diana |last6=Mihalca |first6=Andrei Daniel |date=2022-11-14 |title=Thelazia lacrymalis in horses from Romania: epidemiology, morphology and phylogenetic analysis |journal=Parasites & Vectors |volume=15 |issue=1 |pages=425 |doi=10.1186/s13071-022-05532-z |issn=1756-3305 |pmc=9664606 |pmid=36376981 |doi-access=free }}</ref>
Examination of 122 eyes and 162 nasolachrymal ducts of cattle over 8 years old in Denmark revealed Thelazia skrjabini in 2 cows. This is the first record of Thelazia in Denmark.<ref>{{Cite web |title=How to access research remotely |url=https://www.cabdirect.org/cabdirect/welcome/?target=%2fcabdirect%2fabstract%2f19750818805 |access-date=2023-12-14 |website=www.cabdirect.org}}</ref>
== See also ==
== References == {{Reflist}}
{{Helminthiases|state=expanded}} {{Taxonbar|from=Q3656383}}
Category:Spirurida Category:Rhabditida genera Category:Parasitic nematodes of vertebrates Category:Veterinary helminthology Category:Taxa described in 1819