Wild equids maintained in large enclosures may suffer from helminth diseases because common hygiene practices have only limited effects on parasite populations. Weekly monitoring of helminth prevalences and pasture infestation was performed for 1 yr in several extensive maintenance systems of two wildlife parks with similar climates to determine when veterinary intervention to control parasites would be useful. We also sought evidence of natural immunogenic reactions among herds of Chapman zebras (Equus quagga antiquorum), Przewalski's horses (Equus przewalskii) and dwarf donkeys (Equus asinus africanus). Fecal and vegetation samples and cultures for third-stage larvae revealed permanent egg shedding in the three species and pasture infestation during the warm, moist periods (July–September) in all enclosures. Stable social structure and low equid population density may be sufficient to make prophylaxis unnecessary in adults, whereas biotic and abiotic environmental factors such as crowding, animal transfers, social integration of subadults, and weaning stress may facilitate temporary severe infections of individuals. Biweekly helminth monitoring is a useful diagnostic tool for extensive management of exotic equids.