What is your diagnosis?
Article Type: Report
Subject: Birds (Health aspects)
Birds (Research)
Infection (Diagnosis)
Infection (Research)
Author: Parker, Dennilyn
Pub Date: 06/01/2009
Publication: Name: Journal of Avian Medicine and Surgery Publisher: Association of Avian Veterinarians Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2009 Association of Avian Veterinarians ISSN: 1082-6742
Issue: Date: June, 2009 Source Volume: 23 Source Issue: 2
Topic: Event Code: 310 Science & research
Geographic: Geographic Scope: Canada Geographic Code: 1CANA Canada
Accession Number: 252006957
Full Text: History

An imprinted, juvenile American crow (Corvus brachyrhynchos) was presented to the Western College of Veterinary Medicine, University of Saskatchewan, for a toe injury. The crow had been acquired by the owner after the crow fell from the nest as a fledgling and had been in captivity for approximately 3 weeks. On physical examination, the toe was unremarkable; however, a large 5 x 4-cm cystic mass that encircled the cloaca was observed (Fig 1). The cloaca was patent and retained tone, and the crow was able to pass urates and feces normally. Several smaller cystic structures were located within the skin over the abdomen and were associated with the follicles around the tail feathers. No other abnormalities were observed on physical examination, and the crow was in good body condition, with slightly frayed feathers typical of improper housing.

The results of a complete blood cell (CBC) count were as follows: packed cell volume (PCV) 35%, total plasma protein 4.4 g/dl, and total leukocyte count was estimated at 3 x [10.sup.3] cells/[micro]l, with 1.02 x [10.sup.3] cells/[miro]l heterophils, 1.98 x [10.sup.3] cells/[micro]l lymphocytes, and an occasional leukocytozoon parasite observed. Results of a plasma biochemical panel were within reference ranges. (1) Ventrodorsal and lateral radiographs revealed a mass that appeared separate from the coelomic cavity. Black fluid was aspirated from the mass. A slide of this fluid was stained with a modified Wright stain and was submitted for cytologic evaluation (Fig 2).




Diagnostic rule-outs for the mass included bacterial, viral, parasitic, or fungal infection; neoplasia; or a developmental anomaly. The aspirated fluid contained a large number of eggs; the eggs ranged in color from light green to blue. Some of these eggs possessed operculated ends, whereas, others had a more pointed appearance. On further examination, the mass appeared to be made up of several hundred cysts, each cyst measured approximately 3 x 3 mm in diameter. Centrally located on each cyst was a small pore that released a black fluid, especially when the area was exposed to liquid by wiping with a wet gauze or rinsing under water. Two isolated cysts from the skin over the abdomen were removed and examined by histology (Fig 3). Each cyst contained 2 hemispherical flukes within thinwalled granulomas. A diagnosis of Collyriclum faba, a trematode of the Troglotrematidae family, was made.

Because of the overwhelming number of cysts in this crow, surgical treatment was planned to remove parasites from half of the affected area, followed by treatment with a systemic antihelmintic drug for the remaining cysts. The concern was that antihelmintic treatment alone may lead to an unfavorable systemic response as a result of massive die-off of the flukes. After anesthetizing the crow and surgically preparing the area, each cyst was surgically incised, and 2 flukes were expressed from each cyst. A total of 400-500 flukes were manually removed over a 1-hour period, which accounted for approximately one-third of the affected area (Fig 4). The crow recovered uneventfully from anesthesia. Three days later, results of a CBC revealed a relative leukocytosis, most likely caused by postoperative inflammation. The PCV was 31%, and the leukocyte count was estimated at 18 x [10.sup.3] cells/[micro]l, with 9 x [10.sup.3] cells/[micro]l heterophils, 1.26 x [10.sup.3] cells/[micro]l eosinophils, 5.94 x [10.sup.3] cells/ [micro]l lymphocytes, and 1.8 x [10.sup.3] cells/[micro]l monocytes.

Surgery was repeated 3 weeks later to treat the large number of remaining cysts. However, during the second surgery most of the cysts contained only a jelly-like material presumed to be dead, degenerating flukes. Approximately half of the cysts were left intact at this point and over the following few months the tissue anomalies (cysts) resolved, with no further treatment. No antihelmintic drugs were used in this crow.



The definitive host for the trematode C faba includes both passeriform and galliform species, and infection has been reported in birds in Europe, Asia, and the Americas (North, Central, and South). (2,3) The complete life cycle of this parasite is unknown; however, it is believed that the first intermediate host is a snail and that the second intermediate host is the dragonfly. (2) In this crow, egg-rich fluid was expelled from the cysts each time the area was wiped with wet gauze or exposed to liquid. This suggests that, when the host enters a pond or puddle, the eggs are dispersed, which allows the intermediate host (snails) access and thus completes the assumed life cycle.

From 1 study, most birds infected with C faba carry 4 or fewer cysts on their body, (4) which can be easily incised to express the flukes. This is the only treatment method reported for this parasite (2); there are no reports of using systemic antiparasitic medications for C faba infections. Severe infections, as in the crow described in this case, carry a risk of anemia, emaciation, and death. (2) Heavy fluke infections are also more difficult to conventionally treat, because it is difficult to access all of the cysts involved. There is one report of a crow infected with C faba that presented with a large number of cysts; however, that crow was not treated because of poor condition and a concurrent poxvirus infection. (5)


In this crow, the flukes became degenerate after the first surgery. The reason for this is unknown; however, likely reasons could include the host mounting a successful immune response, fluke death associated with the surgical scrub or other aspects of the first surgery, or fluke death because of its natural life span. The crow showed no obvious signs of ill effect from the dying trematodes. Therefore, systemic treatment without surgical intervention may be a possible treatment option.

In this case, the bird showed no obvious signs of disease from the massive fluke infection and recovered uneventfully, which suggests that even a heavy infection may be self limiting. The successful outcome of this case may be, in part, because of the rehabilitative efforts by the owner for most of its life; therefore, it was not exposed to the stressors of a natural environment. In the wild, a heavy parasite burden may make the bird more susceptible to other illnesses because of an immunocompromised state. (5) More information about this fluke's life cycle is required to further understand the potential health risk to susceptible avian species.

This case was submitted by Dennilyn Parker, DVM, MVetSc, Dipl ABVP (Avian), from the Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5B4.


(1.) Teare JA, ed. Reference Ranges for Physiological Values in Captive Wildlife [CD-ROM]. Apple Valley, MN: International Species Information System; 2002.

(2.) Soulsby EJL. Helminths, Arthropods and Protozoa of Domesticated Animals. 7th ed. Philadelphia, PA: Lea & Febiger; 1982:63.

(3.) Literak I, Honza M, Haluzik M, et al. Cutaneous trematode Collyriclum faba in wild birds in the central European Carpathians. J Parasitol. 2003; 89(2):412-416.

(4.) Blankespoor HD, Esch GW, Johnson WC. Some observations on the biology of Collyriclum faba (Bremser in Schmalz, 1831). J Parasitol. 1985;71(4): 469-471.

(5.) Grove DM, Zajac AM, Spahr J, et al. Combined infection by avian poxvirus and Collyrielum faba in an American crow (Corvus brachyrhyncos). J Zoo Wildl Med. 2005;36(1):111-114.
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