Bots
Basic Information 
Epidemiology
Contagion and Zoonosis
• Bots are not directly contagious from horses to people.
• There are occasional reports of human infection with horse botfly larvae, several of which involved patients with known exposure to horses.
• Migration of first-stage larvae is associated with cutaneous and ocular myiasis in humans.
• The burrowing of larvae beneath the skin may produce a tortuous path with severe pruritus.
Geography and Seasonality
• Infection with botfly larvae occurs in horses worldwide.
• G. intestinalis and G. nasalis are the most common species in North America.
• G. pecorum is found in Asia.
• Adult fly activity is most common in the summer and fall.
• Larvae persist in the stomach and intestine through the winter and spring.
Clinical Presentation
History, Chief Complaint
• Most horses show no recognizable clinical signs.
• Abnormal behavior may be caused by attempts at fly evasion.
• Signs associated with minor gingival irritation and necrosis, including increased salivation, abnormal mastication, and swallowing.
• Signs of colic and endotoxemia in the rare horse with gastric ulceration and rupture, gastritis, peritonitis secondary to gastroduodenal perforation, or gastroesophageal reflux.
• Aberrant larval migration may cause more unusual clinical signs.
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