Bromethalin, a common poison in rats, is the agent responsible for a neurological disease that has sickened or killed birds in a popular group of naturalized parrots residing mainly in the Telegraph Hill area of northern San Francisco, according to a new study conducted by the research laboratory on Infectious diseases of the University of Georgia and funded by Mickaboo Companion Bird Porter relief.
The study, published today in PLOS ONE, culminates a multi-year effort to determine the cause of the disease, observed in parrots of this herd since at least 1999.
"The survey, inspired and funded by Mickaboo, required the establishment of a team of veterinarians, pathologists and researchers. It is only because the poisoned birds were wild parrots that the state has been the subject of such a thorough investigation, "said first author, Fern Van Sant, whose clinic For the Birds, in San Jose , California, had treated many affected parrots. "The results provide us with an opportunity to assess the real risk of this rodenticide for domestic animals and wildlife and to clarify the risk of potential contamination of soil and water."
The study focused on four parrots presented in 2018 with a series of characteristic neurological signs reported by veterinary veterinarians to varying degrees: ataxia, cerclage, convulsions and tumbling. Three of these parrots, like many before them, were euthanized when their condition worsened and they could no longer feed themselves.
The research team looked for bromethalin, or its active metabolite, demethyl bromethalin, based on their findings in 15 historical cases from 2013 to 2017. Historical cases lacked evidence of viruses known to cause disease Neurological in parrots, as well as exposure to lead. or other toxins. However, pathologists have found consistent lesions in the central nervous system suggestive of bromethalin poisoning.
Bromethalin is difficult to detect, especially in live animals and especially in wild birds. Some assays have detected bromethalin in adipose animal tissues, but birds usually do not show excess fat from which samples can be taken and tested. In their study, the team led by UGA examined fecal samples of live birds as well as liver and brain samples from deceased parrots. The co-author, Sayed M. Hassan, director of the UGA laboratory for environmental analysis of the Center for Applied Studies on Isotopes, detected bromethalin and desmethyl bromethalin in brain and liver samples. and stool using high performance liquid chromatography.
The results of the study suggest that parrots do not metabolize potent neurotoxin in the same manner as described in other species and / or that they ingest a sublethal dose. The authors do not know how parrots are exposed to bromethalin, but they plan a follow-up study to determine the source.
"We now need funds from individuals and groups interested in protecting our environment to help us understand if this toxin is accumulating in a space where it could pose a health risk to our environment." other wild animals or, possibly, pets and people, "said co-author Branson W. Ritchie, professor of veterinary research and co-director of the Laboratory of Infectious Diseases.
Birds reside primarily in neighborhoods near the San Francisco-Oakland Bay Bridge and frequent the area's parks, but infected birds have been found throughout San Francisco, including the busy downtown streets and sidewalks. . The total number of birds affected so far is difficult to estimate, but from 2003 to 2018, Mickaboo Companion Bird Rescue had set records for 158 San Francisco parrots, including 55 dead, 53 adopted, 22 released, including three who had escaped and 25 remain in foster care. Many foster and adopted birds have persistent neurological deficits, including paresis and ataxia, that require special care.
Members of the public who come in contact with a parrot likely to be affected should immediately report the bird and its location to San Francisco Animal Care and Control, at 415-554-9400; Poisoned birds need the help of a professional and should not be handled or injured. If necessary, a towel can be used to move the bird in a secure box or kennel.
"Mickaboo Companion Bird Rescue is grateful to Dr. Van Sant, of the University of Georgia, and to all the skilled professionals who have worked so hard and so long to discover what had killed these magnificent birds," said Michelle Yesney. , Current CEO of Mickaboo. The parrots and their plight gained notoriety after being featured in a book and documentary titled "Telegraph Hill's Wild Parrots".
Among the co-authors of the study included Drury Reavill, of the Zoo / Exotic Pathology Service, Carmichael, California; Elizabeth W. Howerth and Mauricio Seguel, Department of Pathology, College of Veterinary Medicine; Rita McManamon, Christopher R. Gregory and Paula G. Ciembor, Infectious Diseases Laboratory, College of Veterinary Medicine; Kathy M. Loftis, Center for Applied Studies on Isotopes; and Richard Bauer, a graduate student in the Environmental Analysis Laboratory. "Evidence for bromethalin toxicity in conures" San Francisco's "Telegraph Hill" is available online at https://journals.plos.org/plosone/article?id=10.1371/journal.pone. 0213248.