Zoonotic Onchocerca lupi infection in a 22-month-old child in Arizona: first report in the United States and a review of the literature

Abstract

A 22-month-old girl presented with neck pain and stiffness and magnetic resonance imaging showed an extradural mass extending from C2 through the C4 level with moderate to severe compression of the cord. A left unilateral C2-C4 laminectomy was performed revealing an extradural rubbery tumor; a small biopsy was obtained. Examination of stained tissue revealed the presence of a parasitic worm that was identified as a gravid female Onchocerca lupi. A magnetic resonance imaging at 7 weeks follow-up showed a significantly decreased size of the enhancing lesion and the patient's symptoms gradually resolved. This is the first report of zoonotic O. lupi in the United States. The parasite has been reported in dogs and cats in the western United States, and from people in four cases reported from Europe. A great deal more needs to be learned, including full host range and geographic distribution, before we fully understand O. lupi infections in animals and man.

Figure 1.

T1 post-contrast magnetic resonance (MR) images of the neck with fat saturation of patient with zoonotic Onchocerca infection. (A) Image pre-biopsy showing a soft tissue mass (arrow) in the cervical central canal extending from C2 through the C4 level. (B) Image 7 weeks post biopsy showing significant reduction in the soft tissue mass (arrow) in the cervical central canal extending from C2 through the C4 level.

Figure 2.

Tissue sections of female Onchocerca lupi, hematoxylin and eosin stain. (A) Cross-section illustrating the morphology of the worm, including the detail of the muscle cells and large lateral chords, and the presence of microfilariae in utero (arrows). Scale bar = 50 μm. (B) Tangential section in which the same morphologic features are evident, including the presence of a microfilaria in utero (large arrow), and illustrating the distinctive cuticular ridges (small arrows). Scale bar same as in (A).

Figure 3.

Longitudinal section of female Onchocerca lupi at higher magnification illustrating the multilayered cuticle with external circular ridges (long arrow) and inner striae (short arrow). Scale bar = 10 μm.

Figure 4.

Map of the United States illustrating the approximate location where the 15 unusual cases of onchocerciasis have been reported in humans, dogs, and cats.