CROW Case of the Week: Mottled Duck (#19-1903)

The mottled duck (Anas fulvigula) is a close relative to the more common mallard. It has a sturdy body, short neck, buffed head, short tail and relatively long bill. These “dabbling ducks” usually feed at the surface or reach for submerged vegetation. Not known as divers, they rarely submerge in water unless being attacked by a predator.

Mottled ducks pair up earlier than most other ducks, typically by November before the breeding season starts the following spring. While many dabbling duck pairs are known to split up as soon as the female lays eggs, male mottled ducks tend to be more loyal and remain with their mate well into the incubation period and sometimes later.

The mottled duck population is threatened by the draining and destruction of marshland as well as interbreeding with mallards in regard to its pure stock outlook. The latter is the result of the release of numerous pet mallards in Florida and elsewhere in the southeast. These feral birds interbreed with mottled ducks and, as a result, dilute the wild population of the mottled ducks.

At CROW, a mottled duck was admitted from Fort Myers after being found lying on her back unable to stand upright or fly. Initial examinations done by veterinarians showed the patient had poor control of its limbs and an inability to correctly stand, symptoms consistent with botulism.

“We are treating this case as a suspect botulism based on the clinical signs, which is mainly symmetrically decreased use of the hind limbs,” said Dr. Kyle Abbott, CROW veterinary intern. “We also consider other differentials (possible diagnoses) such as spinal trauma, pelvic trauma, or other toxins. We performed radiographs to assess for spinal and pelvic trauma and help us determine the most likely diagnosis.”

Radiographs taken of the patient showed no abnormalities. “Botulism is usually obtained from ingestion of the toxin in the environment,” said Dr. Abbott. “The toxin can naturally occur, and the ducks ingest it through normal eating.”

Red tide poisoning was ruled out due to the patient’s feeding environment. “Brevetoxicosis is unlikely to cause signs in mottled ducks as they do not feed in the salt water areas where the algae is prominent. They feed more along fresh and brackish water areas where other toxins are much more likely,” said Dr. Abbott.

“In the clinic, we have not seen many cases of brevetoxicosis over the past few months.” Veterinarians are treating the suspect botulism with medical care and physical therapy, including tub time. “The treatment of botulism is mainly supportive care with appropriate fluid therapies and nutritional support to help the body clear the toxin. We also use an antibiotic that treats the bacterium that causes the disease in case there are living bacteria and not just the toxin itself,” said Dr. Abbott.

“The treatment process can take anywhere from one to multiple weeks.” After a few more days of medical care, the mottled duck appears to be getting better, but the road to full recovery is expected to be long.“The patient is improved and able to stand and walk, although with significant weakness. The duck will continue to need supportive care prior to release,” said Dr. Abbott.

CROW Case of the Week stories are written by Bob Petcher and appear weekly in the Island Sun and River Weekly Newspapers.

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