Shinya Mizutani, Yuko Mizutani, Yoshimichi Goda, Hiroyuki Satoh, Taketoshi Asanuma, Ayako Yoshida, Shidow Torisu

Background
Paragonimiasis, a zoonotic disease caused by Paragonimus spp., typically affects the lungs of humans, dogs, and cats. It is endemic in parts of Asia and can lead to chronic respiratory symptoms. Standard diagnostic imaging methods like X-ray and CT may not sufficiently differentiate paragonimiasis from other lung pathologies. This study reports the first use of dynamic computed tomography (DCT) to visualize live parasite movement in canine pulmonary cysts due to paragonimiasis.

Methods
An 11-year-old French bulldog with incidental findings of pulmonary cysts underwent DCT imaging to assess the lesions. CT scans were performed under anesthesia, and contrast-enhanced CT followed the DCT session. Parasitological tests, including sputum smear and serological ELISA, were used to confirm diagnosis. The study focused on the utility of DCT to dynamically detect movement within cysts.

Results
CT imaging showed two cysts in the right lung lobe, each with distinct air and soft tissue-like layers. DCT revealed undulating motion in the soft tissue-like layer of one cyst, indicating the presence of live parasites. Sputum analysis confirmed Paragonimus eggs, and serological testing was positive for Paragonimus westermani. The nasal lesion was separately diagnosed as adenocarcinoma. The dog's condition remained stable for six months post-diagnosis before succumbing, with no specific treatment administered for paragonimiasis.

Limitations
This case report is limited to a single subject, making broader generalization difficult. DCT's spatial limitations mean only one cyst can be effectively assessed per scan. Furthermore, DCT alone is insufficient for definitive diagnosis and should be complemented with parasitological or serological tests.

Conclusions
This is the first reported case demonstrating the use of DCT to visualize live worm movement in pulmonary cysts in dogs. DCT offers a non-invasive diagnostic tool to differentiate paragonimiasis from other lung conditions, especially in endemic areas. When combined with serology or egg detection, DCT may aid in early and post-treatment assessment of paragonimiasis.

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