Single oral-dose fluralaner treatment against Ophionyssus natricis infestation – a large scale study demostrating long-term efficacy in captive snakes

The hematophagous mite Ophionyssus natricis, vector of several viral and bacterial diseases in snakes, is one of the most challenging pathogens for snake breeders. The high environmental resistance of its larval stage makes repeated treatment of the animals unavoidable, while eradication of the mites from enclosures requires extensive cleansing and disinfection, often involving chemical products with known toxicity. The use of ectoparasiticides of the family of isoxazoline have recently proved effective against both adult and larvae of O. natricis, nevertheless data for fluralaner remains limited, particularly in large cohorts. In this study, 1579 snakes representing 18 different species were treated orally with a liquid formulation of fluralaner (Exzolt®) at 2.5 mg/kg, administered either by injection into the prey prior to feeding or via gastric gavage. Mite detachment and mortality occurred within 5 h, and no reinfestation was observed during subsequent 6-months follow-up period, despite the absence of environmental treatments. No side effects were reported in any treated animals, and no negative impact was observed on oviposition or hatching rate. The prolonged efficacy observed in this study further supports its suitability as a minimally invasive yet highly effective treatment of O. natricis infestations in snakes, given the long half-life of fluralaner already documented in mammals.