Vaccinations for Parrots?
We are often asked about vaccinating our parrots. And the answer is, well, maybe. We have limited vaccines and some have come and gone from the market — mostly gone. The only vaccine available is the polyomavirus vaccine. So what should we do?
Polyomavirus at one time was killing our parrots — mostly hand-reared chicks and sometimes adults, and often in large numbers. In budgies, the disease would affect the nestlings from 10-25 days of age, causing death acutely. Larger parrots are also susceptible to avian polyomavirus (APV) infection but usually do not have signs of disease. Some species are highly susceptible to disease, especially caiques, while others rarely if ever develop signs of disease.
APV-disease occurs at different ages in different species. In conures, death typically occurs in birds less than 6 weeks of age. Death in macaws and Eclectus parrots occur at about (8 weeks) weeks or younger. Most, possibly all, of the nestlings lost are being hand-fed when this happens. Infected chicks that are being hand-fed appear healthy, show very few premonitory signs, and then die suddenly. Chicks kept in the nest box, being fed by the parents, rarely develop disease; this fortunate outcome is due to the transfer of secretory antibody. When signs do occur, they precede death by up to 24 hours. Observant owners may notice delayed crop emptying, weakness, a generalized pallor, or bruising under the skin in the preceding hours before death. Yellow discoloration of the urates is another rare observation. Necropsy findings typically include generalized pallor with subcutaneous and subserosal hemorrhages and enlargement of the spleen and liver. Less commonly, ascites of abdominal fluid and/or pericardial effusion around the heart may be present.
Infection versus Disease
It has become evident that infection and disease are not synonymous, particularly with this virus. Many birds can be infected with the virus but rarely do adult birds develop disease. They develop sensitized B and T lymphocytes, as well as antibodies and an immune response that prevents disease from occurring and eliminates the viral infection. Those that do show disease often are immunosuppressed. The exception is caique species, where adult birds can develop disease. Whether disease will develop is dependent on the species of bird infected, the age of the bird infected, and whether that bird is immune-suppressed. Birds that are infected and do not develop disease still have virus replication within their bodies and shed virus in their droppings for a period of time. The length of time that virus shedding occurs, again, depends on the age of the bird at the time of infection and its species. Some hand-fed birds that are partially immune-competent will develop and recover from transient disease. These birds often retain the viral infection for prolonged periods of time and serve to transmit the infection to naïve individuals.
Birds that are infected but do not develop signs of disease will become viremic and may begin shedding virus through the cloaca and possibly oral mucosa. Rarely, viremia lasts for months. Fecal shedding lasts for up to 16 weeks, but again is much shorter in adult birds and nestlings that are infected at an older age.
A commercial vaccine is available for polyomavirus. Some avian veterinarians recommend vaccination starting at 21 days of age and repeat the vaccine in two weeks. They then follow the recommendation that the parrot should receive the vaccine yearly. Some birds immunized with this vaccine will develop persistent swellings at the immunization site, which is usually the subcutaneous tissue over the caudal pectoral muscles. These lesions will take several weeks to a few months to regress completely. There are other times that these injection sites can lead to dermal tumors. The other problem with the vaccine is that, scientifically, administration of the vaccine in one study did not result in titers when given to young parrots that had not been previously exposed to the virus. Multiple blood samples were collected including 2 weeks after the second booster. None of the naïve individuals produced detectable antibody titers. Antibody was detected in a 1-year-old sun conure that survived a polyomavirus outbreak. This bird had detectable titers prior to vaccination that did not change throughout the study. Because none of the naive parrots produced any antibody titers, it was unknown if the vaccine could protect them if they were exposed to the virus.
For these reasons, other avian veterinarians have chosen not to vaccinate parrots for polyomavirus. While there are other infectious diseases out there that affect our feathered companions and can cause serious harm, effective vaccines have not been produced to date to keep them from getting diseases these organisms cause.
Importance of Annual Vet-Checks
But that does not mean that because we don’t have reliable vaccines for our parrots we should not take them to our avian veterinarians for yearly exams. All companion birds, just like our dogs and cats, need to get checked out with a yearly examination. Many companion birds can have low-grade infections, and if the immune system becomes depressed, can develop serious signs of illness quickly. For this reason, many avian veterinarians will perform Gram stains of the choanal slit in the oral cavity of the patient along with a fecal Gram stain. This will help them to determine if there are infections in the bird, which attempts to mask signs of disease.
Depending on the age and the health status of a particular avian patient, we might also take X-rays, measure their blood pressure, do cardiac ultrasounds, and/or take blood for various tests. All of these processes, along with reviewing the husbandry of the avian patient, is designed to keep them as healthy as possible. We want them to all lead long and healthy, enjoyable lives!