Spinal intradural extramedullary hydatidosis: report of three cases.

OBJECTIVE: Spinal hydatid cyst is a serious form of hydatid disease affecting fewer than 1% of all patients with hydatid disease. We report 3 healthy patients who presented with progressive paraparesis attributed to a histologically proven intradural hydatid cyst. METHODS: There were 2 children (1 boy, 1 girl) and 1 adult with a mean age of 12 years. The median follow-up duration was 16 months. Spinal magnetic resonance imaging was performed in the 3 patients, and an anatomic and topographical diagnosis of the intradural hydatid cyst was made. RESULTS: Magnetic resonance imaging scans revealed cystic lesions with peripheral contrast enhancement. Surgery was performed through laminectomy, complete resection was achieved, and antihelminthic treatment with albendazole 10 mg/kg-1 per day for 6 months was included in the postoperative treatment. The patients improved after surgery with normal motor function. CONCLUSION: This localization is rare and serious, but its prognosis is excellent if diagnosis is made early enough and surgery is performed in time to prevent cyst rupture.

Establishment of adult Parelaphostrongylus tenuis, patent infections, and acquired immunity after experimental infection of white-tailed deer (Odocoileus virginianus) and red deer (Cervus elaphus elaphus).

Experimental Parelaphostrongylus tenuis infections were established in white-tailed deer (Odocoileus virginianus) and an atypical host, red deer (Cervus elaphus elaphus). Groups of deer were fed 10, 25, or 100 third-stage larvae (L3) of P. tenuis and received a single equivalent challenge exposure at varying intervals. Infections were monitored up to 6 yr in white-tailed deer and up to 2.8 yr in red deer. The prepatent period in white-tailed deer varied from 91 to 1,072 days (381 +/- 374) and in red deer from 105 to 358 days (167 +/- 77). Adult worms lived for up to 6 yr in white-tailed deer. Although most had patent infections until necropsy, latent periods were observed regardless of season. Adult worms lived for up to 2.8 yr in red deer, and patent infections persisted for 20-363 days (152 +/- 106). Patent infections were correlated with the presence of adult worms in blood vessels and sinuses of both deer species. Worms were restricted to the subdural space in all deer with latent and occult infections. Adult worm recovery in white-tailed deer fed 10 or 25 L3 corresponded to the mean intensities reported in natural infections of white-tailed deer Recovery from deer fed 100 L3 was not typical of natural infection intensities. Adult P. tenuis established in all groups of red deer, but neurologic disease was restricted to animals fed 100 L3. Acute neurologic disease was associated with subdural hemorrhage and occurred at 11 mo postinfection in 2 red deer. The absence of postchallenge patent periods and the persistence of occult infections indicated that challenge exposures did not establish. These data indicate that acquired immunity to P. tenuis was established by 6 mo postinfection in both white-tailed and red deer. Latent periods in white-tailed deer and latent infections in red deer reinforce the need for a reliable diagnostic assay.

Meningeal worm is a long-lived parasitic nematode in white-tailed deer.

A natural infection of the meningeal worm, Parelaphostrongylus tenuis, persisted for at least 3.7 yr in a white-tailed deer (Odocoileus virginianus). The deer was 5-7 yr old and was shedding dorsal-spined nematode larvae at the time of quarantine. Larvae were extracted from all fecal samples collected up to 730 days post-quarantine (dpq) and thereafter only at 862 dpq and at necropsy (1,350 dpq). Live adults of P. tenuis, one male and one female, were recovered from the cranium at necropsy. Parelaphostrongylus tenuis infections are long lived and latent periods may be extended. Our findings reaffirm the need for reliable antemortem diagnosis to identify non-patent P. tenuis infections to prevent inadvertent introduction of infected animals to non-endemic areas.

Low-dose meningeal worm (Parelaphostrongylus tenuis) infections in moose (Alces alces).

Parelaphostrongylosis has a rapid onset and is lethal in neonatal moose (Alces alces) when large numbers of third-stage Parelaphostrongylus tenuis larvae (L3) are given experimentally. Little is known, however, about the severity and prognosis of infections acquired naturally by accidentally ingesting terrestrial gastropods which are rarely infected and have few larvae. To investigate the relationship between infecting dose, age of moose, and severity of disease, five calves were given low doses of three to 10 L3 when five (n = 2) or 9.5 mo old (n = 3). Each of two animals initially given low doses were later challenged with a dose of 15 L3. As positive controls, two calves were given doses of 15 and 30 L3, considered to be high. All five calves given low doses showed abnormal locomotory signs at 20-28 days postinoculation (DPI) that progressively became more pronounced with hind quarter weakness and front lameness. However, after 77-130 DPI, signs diminished markedly in two of these animals and disappeared in another two. Challenge infections of 15 L3 given 199 days after initial infections had no noticeable effects although an immature worm, probably resulting from the challenge, was found in the spinal cord of one animal killed 51 days later. Two positive control animals given the high doses of 15 and 30 L3 showed moderate to severe, non-resolving, locomotory signs and had to be euthanized. Results demonstrate that single, low doses of three to 10 P. tenuis L3 cause moderate disease in moose calves but over time, some worms die and animals can recover. A degree of protection may develop against future infection.

Migration of adult Elaphostrongylus rangiferi (Nematoda: Protostrongylidae) from the spinal subdural space to the muscles of reindeer (Rangifer tarandus).

To trace the intrahost migration of adult (fifth-stage) Elaphostrongylus rangiferi 9 reindeer calves were fed infective larvae and examined for worms 48-250 days postinfection. The average length of worms recovered increased asymptotically with time. Gravid females and adult males were recovered from 52 days postinfection (d.p.i.), and the fraction made up by these categories increased with time. Immature females and subadult males were recovered as late as 161 d.p.i. Nematodes were recovered from the spinal subdural space 48-161 d.p.i., from the cranial subdural space 48-90 d.p.i., and from the musculature 90-250 d.p.i. Immature females were found in the spinal subdural space and the cranial subdural space, whereas gravid females were found also in the musculature with an increasing fraction with time. Subadult and adult males were found in all 3 sites but with an increasing fraction of adults from the spinal canal to the cranium to the musculature.