The Spot and the Pet (Damn It Jim, I’m a Doctor Not a Veterinarian!!)

1. The Spot and the Pet(Damn It Jim, I’m a Doctor Not a Veterinarian!!) Gary L. Weinstein M.D. FCCP Internal Medicine, Clinical Grand Rounds Wednesday, January 18th, 2006

2. The Spot and the Pet • HPI : • DB is a 62 yo WM referred for eval of abnl CXR • Found on pre-op w/u for spinal stenosis • No cough, chest pain, hemoptysis, wt loss • Mild intermittent wheezing • PMH : • T & A • Appy • Sx for spinal stenosis

3. The Spot and the Pet • Allergies : none • Meds at home : none • Social Hx : • Divorced • Lives alone • Banker • 1 – 2 packs/day Tob for 40 years • 21 beers/week

4. The Spot and the Pet • Family Hx : • Lung cancer in mother • CAD in father • ROS : neg • Exam : • P 80 R 16 BP 140/78 Ht 5”6” Wt 78 kg • WDWN WM in NAD, plethoric • Scattered rhonchi • No LAN

5. The Spot and the Pet • CXR (4/05)

6. The Pet and the Spot • CXR (6/05)

7. The Pet and the Spot • CT chest (6/05)

8. The Pet and the Spot • Pt taken to the OR 7/05 for RU Lobectomy and wedge resection of RML nodule • RUL nodule  necrosis on frozen section • RML nodule  neg for tumor on frozen section

9. RUL necrotic nodule

12. Dirofilaria immitis (dog heart worm) • DIROFILARIASIS — Dirofilariasis is caused by a zoonotic filarial nematode. There are two separate clinical syndromes that are associated with infection with different dirofilarial species. Dirofilariasis is particularly common in the Mediterranean region but has been reported from many different countries, including the United States [1]. • Most cases of dirofilariasis in humans are either pulmonary or subcutaneous infections, but there have been a few reports of human dirofilariasis in unusual sites, such as large vessels, mesentery, peritoneal cavity, spermatic cord or the liver. 1. Jelinek, T, Schulte-Hillen, J, Loscher, T. Human dirofilariasis. Int J Dermatol 1996; 35:872.

13. Dirofilaria immitis (dog heart worm) • Pulmonary dirofilariasis —is caused by Dirofilaria immitis, also known as the dog heart worm since it is a common cause of congestive heart failure in dogs. Although canines are the most important natural host, other mammals can also be infected. • Adult worms of D. immitis live in the heart of the definitive host, and microfilariae are produced which circulate in the peripheral blood. The adult worms have a thick cuticle and are 400 to 500 µm in diameter. When a mosquito bites an infected animal, it can acquire infection and can transmit the infection to other animals or accidentally to humans.

14. Dirofilaria immitis (dog heart worm)

15. Dirofilaria immitis (dog heart worm) • The filariae never mature into fully gravid worms in humans but lodge in pulmonary arteries; infection can lead to granulomas or lung infarctions [2]. These can result in the appearance of nodules or cavities on chest radiographs. • Most human infections are asymptomatic, and the infection is only discovered if chest imaging is performed for some other reason. However, some patients develop chest pain, cough, hemoptysis, fever and malaise [3]. The radiologic appearance is often described as a "coin lesion" that is usually 1 to 3 cm in diameter and may be confused with a lung tumor. 2. Hiroshima, K, Iyoda, A, Toyozaki, T, et al. Human pulmonary dirofilariasis: report of six cases. Tohoku J Exp Med 1999; 189:307. 3.  Ro, JY, Tsakalakis, PJ, White, VA, et al. Pulmonary dirofilariasis: the great imitator of primary or metastatic lung tumor. A clinicopathologic analysis of seven cases and a review of the literature. Hum Pathol 1989; 20:69.

16. Figure 1: Chest x-ray showing a pulmonary "coin" lesion caused by Dirofilaria immitis infection in an adult man. 

18. Dirofilaria • Subcutaneous dirofilariasis —is caused by a few different dirofilarial species, including D. tenuis, D. repens, and others. These species are filariae of dogs and cats (D. repens), raccoons (D. tenuis), or other mammals. These filariae are also transmitted via mosquitoes. Adult worms can develop in humans, but sexual maturity and production of microfilariae do not occur since humans are an incidental host. • Lesions consist of a coiled, degenerating worm in subcutaneous tissues, typically around the eye or on the genitalia or limbs [4,5]. The nodule can be erythematous and tender and can be associated with an abscess. There may be concomitant allergic symptoms, including urticaria and fever. 4. Fuentes, I, Cascales, A, Ros, JM, et al. Human subcutaneous dirofilariasis caused by Dirofilaria repens in Ibiza, Spain. Am J Trop Med Hyg 1994; 51:401. 5.  Arvanitis, PG, Vakalis, NC, Damanakis, AG, Theodossiadis, GP. Ophthalmic dirofilariasis. Am J Ophthalmol 1997; 123:689.

19. Dirofilaria inflammatory lesion at the inner canthus of the eye An immature adult female Dirofilaria species that measured more than 12 cm in length, removed intact from human subcutaneous tissues.

21. Dirofilaria immitis (dog heart worm) • DB tolerated sx well and had no post-op comps • He has recovered fully and received no specific treatment • He is a fisherman and a hunter and to his knowledge, his dogs are well.

22. Dirofilaria immitis (dog heart worm)

23. Q U E S T I O N S ? ?

24. THE END Farley