 |
| (c) Anjajuli Dreamstime.com |
Thelaziosis is a parasitic disease caused by nematodes (round worms) of the genus Thelazia (typically Thelazia lacrymalis in horses).
In the United States, the infection rate for cattle and horses in has been estimated at 15% to 38%. In Europe, equine thelaziosis has been reported occasionally in countries such as Russian Federation, England, France, Germany, Sweden and Italy.
Eyeworms live in the tear glands, conjunctival sac, and under the eyelids. The intermediate hosts are non-biting flies, such as Musca autumnalis, which swallow the larvae as they feed on the lachrymal secretions. Larvae become infective within 2-4 weeks and are deposited on the horse’s eye when the fly feeds. In about 10 weeks the adult worms produce more larvae and the cycle continues.
Infections may occur year-round, but disease outbreaks usually are associated with the warm season when the flies are more active.
Infections often produce no obvious signs. However, inflammation of the conjunctiva and eyelids can occur, and more severe cases may show inflammation, swelling, and cloudiness of the cornea.
A study in Romania, examined post-mortem specimens from 273 horses. The work, by Vlad-Dan Cotuțiu, and colleagues, is reported in Parasites & Vectors.
They found 12 infected horses (4.39%). They recovered 87 worms, which they identified as T. lacrymalis. They report that the intensity of infestation varied between one and 33 nematodes/animal. Five animals were infected in both eyes.
The numbers found were too low to reach statistically significant conclusions. However, the authors suggest that altitude may be a factor in the occurrence of thelaziosis. “In this study there were no infested animals originating from the alpine ecoregion (0 of 45); therefore, a plausible explanation could be the decreased vector abundance and shorter seasonal activity at higher altitudes.”
They also suggest that the widespread use of oral deworming protocols, including macrocyclic lactones or fenbendazole, probably contributed to the low prevalence.
The authors conclude: “We consider equine thelaziosis a neglected disease in Europe, which requires more attention from veterinary practitioners mainly from an animal welfare point of view due to the potentially severe clinical impact.”
For more details, see:
Thelazia lacrymalis in horses from Romania: epidemiology, morphology and phylogenetic analysis.
V-D Cotuțiu, A M Ionică, M Lefkaditis, C D Cazan, D H Alina, A D Mihalca.
Parasites Vectors 15, 425 (2022).
1 comment:
What wormers are effective in getting rid of this parasite?
Post a Comment