By Sam Vaughn, DVM, Dip., ABVP — Avian Practice
I recently lost a pet cockatoo named Angel to a disease my veterinarian calls sarcocystosis. My veterinarian said that opossums transmit this disease. I have another pet bird, a double-yellowheaded Amazon, and three pairs of breeder cockatoos. I am tremendously confused about how my bird contracted this disease, because my birds are usually kept completely indoors. They may go out for a while in the summer in their outdoor cages by the pool. This outside time is always supervised, and they are never in contact with any wild birds or mammals. Can you shed some light on how my bird could contract such a disease? I am really concerned that we have an incorrect diagnosis.
First, I would ask the veterinarian how the diagnosis was achieved. If it was by histopathology as a result of autopsy, then you have an iron-clad diagnosis. This disease, caused by the protozoal organism Sarcocystis falculata, is a rapidly fulminating pulmonary edema. This means that fluid accumulates very fast in the lungs and susceptible species can die in a very short period of time from a lack of oxygen because the lungs are full of fluid. Old World species of psittacines are extremely susceptible to this disease; this is probably why your Amazon remains normal while your cockatoo passed away very quickly. I am sorry for your loss, and I hope you do not lose any more birds. Old World psittacines include primarily those that are from Africa and Australia. Thus, Amazons, conures and macaws are much more resistant. We believe the reason for this is that Old World species have no natural reservoir (opossum) and thus have not ever established immunity to this organism.
Last year, here in Kentucky, I had an individual with three pairs of Indian ringnecked parakeets. He lost six birds in five days. These birds were in an outside aviary in a relatively densely populated suburban area. Opossums frequented the outside garbage can where he disposed of aviary waste. This was an obvious means of transmission, because opossums do not have to come near the birds at all. It appears that the opossum feces contained the infectious organisms. A transport host, like cockroaches or other insects, feeds on the opossum feces, and then deposits its feces in birds' food or water bowls, infecting them. This might be how your bird became infected. Also, flies could do their little regurgitation/feeding cycle on a fresh branch you cut for your birds to chew on and brought into the house.
This disease is being diagnosed with increasing frequency for a number of reasons, I believe. First, avian veterinarians are more aware of this disease than they previously were. I remember at my earliest avian veterinarian meetings, 10 to 12 years ago, that this disease was thought to occur only in the deep, deep South. Eight years ago when I diagnosed the first recorded event of this disease in Kentucky, many veterinarians thought I had lost my mind. I have now diagnosed it as far north as about 200 miles north of Indianapolis. I think with this new data that many veterinarians are now including this disease in the differential diagnosis of acute death with fulminating pulmonary edema.
Also many veterinarians, including myself, have thought of this as an aviary disease and not a pet bird disease. Or another way to say this is an outside bird disease versus an inside bird disease. The truth is that this devastating disease can occur either outdoors or indoors. This organism can enter your home many different ways: via different types of insects, on your clothes, on your shoes, on your Christmas tree, by your four-legged pets and I firmly believe that flies can zoom right into your living room and deposit the organism anywhere in your home.
You probably have the right diagnosis, even though it is often hard to understand how birds in our homes could be exposed to such diseases.
So what do you do? Well, if I had opossum frequenting my property, I would set humane traps and trap them and relocate them to a National Forest. There are commercial companies that do this type of work. Some folks build "opossum fences" a six-inch high electric fence as far as possible away from the aviary, around the entire perimeter of their property to keep all small mammals of this size away from the aviary. Insect control is always important, as is the control of vermin. The old fashioned fly strips are ugly and not very appealing to the eye but when placed where your birds cannot reach them, they do a nice job of fly control without chemicals flying around your birds.
West Nile Virus
Another disease to be watch for is the West Nile Virus. This was diagnosed by a woman veterinarian in the Northeast, and found to be transmitted by mosquitoes. It has claimed several human lives. The veterinarian began her inquisition as a result of finding large numbers of dead crows. I wonder how susceptible psittacines are to this virus? I hope I do not have to find out, but I will be looking.
Warning About Chemical Vermin Control
Let me take a moment here to say something about rat and mouse control. Please do not use chemical rodenticides around your birds. Rodents consume these over a period of time before they die. While they are doing this, they are still defecating in your birds' food and water bowls. Your birds ingest this when feeding and can be poisoned themselves. In the case of anticoagulant rodenticides, this can wreak havoc in your aviary. One of the worst disasters I had in an aviary was a result of this. Please use traps, not chemicals, to avoid this disaster in your aviary.
If you have a question for Dr. Vaughn, send him an e-mail care of BIRD BREEDER at firstname.lastname@example.org. We regret that columnists are not able to respond to letters individually.
Sam Vaughn, DVM, Dip., ABVP — Avian Practice is an avian specialist based in Louisville, Kentucky. Certified in Avian Practice by the American Board of Veterinary Practitioners, Dr. Vaughn owns Avian Medical Services Inc. (an avicultural service and consultation practice) and is a partner in Veterinary Associates Stonefield, a full-service avian/exotic and small animal practice. Dr. Vaughn holds degrees in biology, chemistry and a Doctorate of Veterinary Medicine from Auburn University. Feel free to visit his web site at http://www.vetcity.com. Telephone consultations by appointment are available by calling (502) 245-7863.