VPA 221: Veterinary Entomology and Acarology (1+1)

EFFECT ON THE HOST - HORSE BOT FLIES

Adult flies

• The presence of the hovering flies result in gadding in horses and the resultant injury, loss of condition due to improper feeding

Larval stages

•  The first stage larvae during its migration in the tongue can result in ulceration of the tongue
• The second stage larvae may attach itself to the epiglottis, the pharynx and can cause injury to these regions by its oral hooks
• Since the second and third stage larvae ultimately attach to the non glandular part of the stomach they do not seem to cause much damage
• However there is a inflammatory reaction to the attached larvae and the stomach mucosa is thickened into a rim around the site of attachment
• Debility is observed in animals with the infestation and is believed to be due to the toxicity of the excretions and secretions of the larvae
• The third stage mature larvae is also capable of causing injury by its oral hooks and other spines  to the rectal region when its passed out in the faeces
• However, generally horses harbour these larvae without any sign of discomfort or disease