Thirteen cases of pulmonary dirofilariasis in a single institution in Okinawa Island

Eriko Atsumi,Naoki Yoshimi,Hirofumi Matsumoto,Hidenori Kawasaki,Tsutomu Kawabata,Naohiro Taira,Tomofumi Yohena

doi:10.1007/s00428-019-02614-9

Abstract

Pulmonary dirofilariasis is an infection caused by Dirofilaria immitis, which is an endemic parasite in Japan. We experienced 13 surgical cases of pulmonary dirofilariasis in our hospital. Of the 13 patients, 61.5% were men. The responsible lesions were located in the right lung in all cases, and 76.9% of them were in the lower lobe. Histologically, 12 cases showed necrotic nodules with peripheral granuloma with worms inside the pulmonary artery. One case did not show a necrotic nodule but showed only thickening and hyalinization of the pulmonary artery wall with a degenerated worm inside. Eosinophils were found histologically in all cases. Thirteen cases of dirofilariasis in one institution seem to be the largest number in Japan, based on previous reports. One reason for this increased prevalence may be the hot and humid climate of our prefecture considering the ecology of the mosquito as a vector. Elastic staining and eosinophils in peripheral granulomatous areas can contribute to the diagnosis when the worms are degenerated.

Highlights

Pulmonary dirofilariasis is a nematode infection caused by Dirofilaria immitis (D. immitis), which is an endemic parasite in Japan among canines and felines
Cell counting was performed in 3 representative fields at × 400 magnification on Hematoxylin and eosin (H&E)-stained slides, and the average counts were classified into the following 3 categories: category 0: 0– 2 eosinophils in 1 high-power field (HPF); category 1: 3–50 eosinophils in 1 HPF; and category 2: > 50 eosinophils in 1 HPF
In 12 cases (92.3%), the pulmonary nodule was noted by chest imaging prior to surgery; of these cases, 7 were identified by health check, 4 by chest imaging during follow-up or workup for other diseases (1 colon cancer, 1 chronic obstructive pulmonary disease with asthma, 1 meningioma, and 1 biliary colic), and 1 was incidentally found by chest imaging taken for chest and back pain unassociated with dirofilariasis

Summary

Introduction

Pulmonary dirofilariasis is a nematode infection caused by Dirofilaria immitis (D. immitis), which is an endemic parasite in Japan among canines and felines. It is transmitted to humans by bites from mosquitos that have sucked the blood of infected animals. Since the human is not a final host, the larvae die in the heart before maturing into adult worms and are washed out into the lungs, where they form a nidus of the thrombus in the pulmonary artery [1]. Most cases are asymptomatic and usually are noted as a lung nodule on chest X-ray

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