Topically applied ivermectin: efficacy against torsalo (Diptera: Cuterebridae)

Area of Science:

• Veterinary Parasitology
• Dermatology
• Animal Health

Background:

• Torsalo (Dermatobia hominis) larvae cause significant economic losses in cattle production.
• Effective and persistent ectoparasiticides are crucial for livestock management.
• Previous formulations may have limitations in systemic efficacy and duration.

Purpose of the Study:

• To evaluate the systemic efficacy and persistence of a 0.5% ivermectin topical formulation.
• To assess the control of natural Dermatobia hominis infestations in cattle.
• To determine the duration of action of the ivermectin formulation.

Main Methods:

• Two trials were conducted in Colombia and two in Brazil.
• 56 cattle naturally infested with Dermatobia hominis larvae were used.
• 28 cattle received a topical 0.5% ivermectin formulation (0.5 mg AI/kg), while 28 served as untreated controls.

Main Results:

• Treated cattle showed significantly fewer torsalo larvae compared to controls on days 9 and 10.
• The formulation achieved greater than 99% control of Dermatobia hominis larvae.
• The first signs of reinfestation were noted in a few animals around days 30 and 31.

Conclusions:

• The 0.5% ivermectin topical formulation is highly effective and provides systemic control against Dermatobia hominis larvae in cattle.
• The formulation exhibits significant persistence, offering protection for at least 30 days.
• This treatment represents a viable option for managing torsalo infestations in cattle.