Several species of mites can parasitize reptiles; the one that unquestionably stands out in terms of frequency is the arthropod of the mesostigmata suborder Ophionyssus natricis (Fig. 1).
Class: Arachnida
Subclass: Acari
Order: Parasitiformes
Suborder: Mesostigmata
Family: Macronyssidae
Genus: Ophionyssus
Species: O. natricis
Ophionyssus natricis is ahematophagous, non-burrowing mite, which lives on the outer skinof reptiles, on both snakes and lizards. It is an "international" mite, as it is present in all continents. The body of the adult stage of O. natricis is oval, with eight, ventrally inserted, long and thin legs; the body length is between 0.6 and 1.3 mm, making it visible to the naked eye or with the aid of a simple magnifying glass. The limbs and the body surface both present short hairs, in limited numbers.
The life cycle of the mite takes place on a single host: the egg hatches a non-feeding larva, which then reaches the adult stage through two nymphal stages, making a blood meal between each stage. The egg hatches after a period varying between 1 to 4 days and the completion of the entire biological cycle requires less than 20 days; the adult’s average life span may exceed 40 days.
O. natricis parasitizes especially snakes, but also lizards, and is at times the cause of massive infestations within the reptile cage. The mites, which are visible on the body surface of the reptile, attack any new subject added to the parasitized cage, resulting in substantial blood withdrawals with consequent marked anaemia; in more severe infestations the blood sucking can cause the death of the parasitized subject. In the case of mild infestations, or even of massive ones but still in their initial stages, the animals are restless and try to get relief by rubbing against the reptile cage furniture or soaking in the water tank. When the blood loss becomes significant, the affected subjects become apathetic, they remain still and refuse food. These arthropods may also cause scabbing dermatitis, which may give rise to secondary infections. The diagnosis is mainly based on the detection of the parasite directly on the animal’s body or within the display case, or because of the presence of the mite’s excrements.
In some cases the mite may also be detected on the skin of the owner or of the person who takes care of the reptiles, on whom it may occasionally cause inflammatory reactions. O.natricis may also spread some diseases, such as parasitic blood infections, bacterial septicaemia and IBD.
The infestation can be treated successfully; however, the complete eradication of the parasite is rather difficult as it canhide away from the host and survive for several days, to then make its reappearance after a short period of time.
For treatment, various ectoparasiticides may be used, each one with its own specific therapeutic protocol: Carbaryl, Fipronil, Ivermectin, Permethrin, Pyrethrin, Resmethrin or olive oil brushings (for more details refer to the Scivac Therapeutic Formulary (2014) or the Carpenter Drug Formulary (2013)).
Some authors suggest the use of biological control agents, such as the predatory mite Cheyletus eruditus, already used in agriculture and in the control of Dermanyssus gallinae.
As for prevention, itis advisable to quarantine and keep under observation all newly acquired animals, housing them in clean, disinfected and disinfested cages. When necessary, new specimens should preferably be treated before their transfer into the collection. The cages must be sanitized, disinfected and possibly treated with acaricides (obviously compatible with the species being stabulated, or properly rinsed) or with steam.