Recent lay press articles1 invite the public to consider tarantulas as suitable pets, suggesting that parents bring their children to discover the thrill of owning exotic animals. Few of those articles, however, mention the dangers inherent in handling these spiders. Bites are reported to cause mainly local cutaneous reactions,2,3 whereas urticating hairs can cause intense and prolonged urticaria.3,4 In the eye, the consequences of exposure to tarantula hairs may span a broader spectrum, from a mild allergic conjunctivitis to a chronic granulomatous keratoconjunctivitis or even chorioretinal lesions.5,6 A recent case prompted us to promote awareness of these potential dangers.
An 18-year-old young man from LaCrosse, Wis, presented with a 6-week history of irritation of the right eye. His symptoms included diffuse pain, redness, swelling, tearing, and photophobia. Previous treatment by an ophthalmologist with topical corticosteroid (Inflammase 1%) given for what had been diagnosed as an allergic reaction had brought inconsistent relief. On examination, his visual acuity was 20/25 in the involved right eye and 20/20 in the left eye. Slit-lamp OD examination showed a mild epibulbar injection, a papillary conjunctiva! reaction, mild cells and flare in the anterior chamber, and a few keratic precipitates. Within the corneal stroma and conjunctiva, multiple fine linear threadlike opacities with surrounding inflammatory reaction were noted at all depths (Fig 1). The fundi were unremarkable, and no preauricular nodes were palpable.
When asked about exposure to unusual foreign bodies, the patient initially denied any, but later recalled having been in contact with a friend's tarantula pet 1 day prior to the onset of symptoms. Treatment was started with topical 1% prednisolone acetate, but the patient's compliance was questionable in his group home environment and no improvement was seen on examination 4 weeks later. Several inferior limbal nodules were noted on slit-lamp viewing and biopsied under topical anesthesia. Histopathologic examination of both conjunctival and corneal lesions revealed the presence of foci of chronic foreign body giant cell granulomatous inflammation surrounding fragments of hairshafts with barbs on the side and an inner lumen, identified as tarantula hairs (Fig 2). Four months later, with patient compliance still uncertain, the inflammation had not subsided, corneal haze was worse, and mutton-fat keratic precipitates were prominent (Fig 3). The patient subsequently was lost to follow up for 1 year. In a recent follow-up call VA years after initial presentation, the patient, who had moved out of state, acknowledged that his right eye still was chronically irritated.
Fig 1: Fine threadlike opacities were seen at all depths of the corneal stroma (arrow), along with a few keratic precipitates, mild cells, and flare in the anterior chamber.
Tarantulas have become increasingly popular pets.1-3 These hairy spiders belong to the Theraphosidae family. Most appreciated for their bright colors are the Chilean rose-haired tarantula (this case) and the Mexican red-leg tarantula.2 The New World tarantulas are known to be capable of projecting a cloud of urticating hairs at the face of a predator to drive it away from the spider's burrow. When feeling threatened, the spider raises its hind legs onto the dorsum of its abdomen, and by means of rapid vibrations, flicks a cloud of possibly 10 000 to 1 million hairs. As a result, the dorsum of the abdomen will show patchy absence of hairs. The supply of urticating hairs is renewed each time the spider molts.4 Adults molt once a year and can have a lifespan of about 20 years.2
Four types of hairs are recognized.4 Type III comprises long, thin hairs ranging from 0.3 to 1.2 mm in length, with sturdy barbs along at least half their length, and are found in species from Mexico, the Caribbean, and Central and South America.7 They are capable of penetrating 2 mm deep into the human forearm skin and causing a severe urticarian reaction. The sharp-pointed head of the shaft and numerous barbs are hypothesized to facilitate traversing the cornea or sclera with eye rubbing.5
Fig 2: Corneal stroma biopsy demonstrated granulomatous inflammation with foreign body multinucleated giant cells (arrow) organized around a segment of hairshaft showing internal lumen and lateral barbs (arrow) (hematoxylin-eosin, low magnification).
Fig 3: Slit lamp appearance after 4 months of treatment, showing prominent mutton-fat keratic precipitates (arrow) and increased corneal haze.
At first, the foreign body induces an acute inflammatory reaction, through a mechanical effect or possibly a hypersensitivity or toxic effect.4,7 Subsequently, a chronic granulomatous inflammation ensues over weeks to months, which can include stromal keratitis and subepithelial opacities, mutton-fat keratic precipitates, iritis, nodular conjunctivitis (granulomas), and possibly, delayed chorioretinal lesions after several months.3,5 This clinical entity has been called conjunctivitis nodosa or, as the whole eye is involved, ophthalmia nodosa.5,6
Caterpillar setae, which share the same structure as tarantula hairs, cause an even more pronounced acute allergic reaction, presumably due to histamine release.5,8,9 In addition to all of the features described, they have been known to induce intense iritis with occasional iris nodules (especially when a caterpillar hair has entered the anterior chamber), vitritis with or without cystoid macular edema and papillitis, endophthalmitis, and even loss of the eye. Ophthalmia nodosa also has been reported with synthetic fibers that can be found, eg, in fabrics and toys.10
Besides irrigation of the conjunctival fornices and mechanical removal of all accessible hairs in an emergency, the recommended treatment is based on corticosteroid in topical administration of drops or in subconjunctival or peribulbar injections. Some authors advocate conservative treatment, as steroids can taper the inflammation despite the intracorneal retention of the hairs.6 Disappearance of the engulfed hairs by 10 months after a 3-month treatment with steroids has been reported.3 Others, however, urge surgical removal of all accessible hairs, considering their capacity to migrate deeper.5,8
Four months after our initial examination in this case, keratic precipitates, corneal haze, and ciliary injection remained. At the time of our writing, more than 20 months from initial presentation, the ocular inflammation persists. The chronicity of our case stresses the necessity for an early diagnosis; if possible, immediate removal of the hairs before their incarceration; and the need for prolonged topical corticosteroid use with adequate monitoring to assure compliance.
Due to recent lay press articles that promote tarantulas as pets suitable for children, parents and physicians must be aware of the possible dangers of these animals.
1. Along came some spiders. Wisconsin State Journal. October 12, 1993; section C:1.
2. de Vosjoli P. Arachnomania: TAe General Care and Maintenance of Tarantulas and Scorpions. Lakeside, Calif: Advanced Vivarium Systems; 1991.
3. Chang PC, Soong HK, Barnett JM. Corneal penetration by tarantula hairs. Br J Ophthalmol. 1991; 75: 253-254.
4. Cooke JA, Miller FH, Grover RW, Dufly JL. Urticaria caused by tarantula hairs. Am J Trop Med Hyg. 1973;22: 130-133.
5. Hered RW, Spauldiog AG, Sanitate JJ, Wander AH. Ophthalmia nodosa caused by tarantula hairs. Ophthalmology. 1988;95:166-169.
6. Ratzen AR, Weise JS, Kachadooriau H. Tarantula hair ophthalmia nodosa. Am J Ophthalmol- 1993;! 19:381-382.
7. Stulting RD, Hooper RJ, Cavanagh HD. Ocular injury caused by tarantula hairs. Am J Ophthalmol. 1983^96: 118-1 19.
8. Teske SA, Hirst LW, Gibson BH, ffConnor PA, Watts WH, Carey TM. Caterpillar-induced keratitis. Cornea. 1991;10:317-321.
9. Cadera W, Patchman MA, Fountain JA, Ellis FD, Wilson FM. Ocular lesions caused by caterpillar hairs (ophthalmia nodosa). Can J Ophthalmol. 1984; 19: 40-44.
10. Resnick SC, Schainkeer BA, Ortiz JM. Conjunctiva! synthetic and nonsynthetic fiber granulomas. Cornea. 1991;10:59-62.