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Summary
Thelazia nematodes do not overwinter in face flies, with infections occurring only in actively reproducing insects. This eyeworm parasite is enzootic in Iowa cattle, affecting younger animals more frequently.
Area of Science:
- Veterinary Parasitology
- Entomology
- Animal Health
Background:
- Thelazia nematodes are eyeworm parasites transmitted by flies.
- Understanding the transmission cycle and prevalence is crucial for cattle health.
Purpose of the Study:
- To investigate the prevalence and transmission patterns of Thelazia nematodes in face flies and cattle in Iowa.
- To determine if Thelazia overwinter in face flies and identify risk factors for infection in cattle.
Main Methods:
- A 7-year study monitored Thelazia prevalence in face flies (Musca autumnalis) on a central Iowa beef farm.
- Necropsies were performed on cattle eyes to identify and quantify Thelazia species (T. gulosa, T. skrjabini).
- Prevalence data were analyzed based on fly reproductive status, season, cattle age, and sex.
Main Results:
- Juvenile Thelazia were only found in actively reproducing face flies, suggesting they do not overwinter in this vector.
- Mean Thelazia prevalence in flies was 2.0% over 7 breeding seasons.
- Cattle prevalence was 15% in 18-27 month olds and 3% in adult cows (3-15 years old).
- Thelazia skrjabini and T. gulosa were identified in cattle eyes, with higher worm burdens in T. gulosa infections.
Conclusions:
- Thelazia nematodes likely do not overwinter in face flies in Iowa.
- Thelaziasis is enzootic in Iowa cattle, with younger cattle being more susceptible.
- Face flies are confirmed vectors for Thelazia gulosa and T. skrjabini in this region.