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A NUMBER of cases of tongue worm, Linguatula serrata, in stray dogs imported into the UK have been brought to our attention recently. Infected dogs may show a mucopurulent nasal discharge, epistaxis and sneezing, but infection may also be asymptomatic.
The adult parasite is an elongated tongue-shape with transverse striations and is found in the nasal cavities or sinuses of dogs, foxes and other canids. These animals are infected by the ingestion of L serrata nymphs in raw offal of infected intermediate hosts (sheep, goats and cattle, but also rabbits and horses). The eggs from the adult parasite are expelled from the final host by sneezing or coughing and are immediately infective. They may also be swallowed and appear in the faeces (Taylor and others 2016).
The adult parasite is large, with males measuring up to 20 mm and females 30 to 130 mm in length (Fig 1).
This parasite has been previously reported in the nasal passages of foxes in the UK (Lapage 1968), but the recent cases have been seen in imported stray dogs from Romania, where dogs are routinely fed on raw meat. There are reports, in Romanian journals, of a prevalence of infection with L serrata nymphs of 20 to 40 per cent in the mesenteric lymph nodes of slaughtered domestic ruminants (M. Ionita, Faculty of Veterinary Medicine of Bucharest, personal communication).
The parasite is also potentially zoonotic with rare human infections reported (Acha and Szyfres 2003). These infections have included parasite localisation in the eye requiring surgical intervention (Koehsler and others 2011, Pal and others 2011). Therefore, where the parasite is confirmed or suspected, strict hygiene measures during pet handling should be observed by the owner and all those who have contact with the animal, as eggs could be expelled via the oral, nasal or faecal routes, or contaminate the animal's coat.
Nasal flushing with warm salty water may help to detach the parasites in the dog. Screening of suspected infected animals by identification of eggs in nasal flushes could also be carried out. Surgical removal of the parasite may not be curative as they can attach to the sinuses.
Macrocyclic lactones are used as a treatment in Romania. There is a report of parasite expulsion following milbemycin oxime treatment in a dog (Gjerde 2013) and also that injectable ivermectin was effective against a related species, Linguatula arctica, in reindeer (Haugerud and others 1993).
There has been an incident of the related species, L arctica, being detected in the nasal cavity and distal bronchi of a three-year-old reindeer in Great Britain that died of an unrelated condition. This parasite is reported as being relatively common in semi-domesticated reindeer in northern Norway (Gjerde 2013).
Veterinary practitioners should be alert to the possibility of L serrata, particularly in imported dogs, and should treat appropriately and provide the correct advice to owners.
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