Português

Wild birds face many health challenges that can harm them as individuals in addition to causing extinction threats. Some of these challenges have worsened in recent years, including habitat loss, climate change, and the spread of infectious diseases.

The authors of this study point out that diseases may not impact all birds equally. For example, certain diseases may vary depending on a bird’s origin or living situation (i.e., whether they live in the wild, are kept as companions, or are rescued from the illegal wild animal trade). For this reason, the authors set out to study the presence and frequency of different types of diseases affecting wild, captive, and rescued birds in Brazil.   

The researchers examined the bodies of 243 deceased birds who were sent to a Brazilian university’s veterinary school for analysis between 2006-2021. They did a postmortem study and/or examined affected tissues to determine what caused each animal’s death. Among the birds they studied, 24 were classified as wild (found dead in their natural habitat), while 95 were rescued from trafficking and 113 were captive companions or kept in aviaries. The remaining 11 birds’ origin was undetermined.       

Almost half of the birds (46.5%) were from the Psittaciformes species (e.g., parrots), followed by 26% who were Passeriformes (e.g., Great-billed seed finches). Galliformes made up 9% of the sample (e.g., peacocks, pheasants, and turkeys), while 6% of birds were Columbiformes (e.g., doves and pigeons).

Infectious diseases were the most common cause of death, affecting 177 birds (73%). These diseases either had a viral, bacterial, fungal, or parasitic origin. Some birds were infected by one infection, while 18% had a combination of two or more (mainly viral-bacterial or viral-parasitic). Birds with multiple infections tended to be rescued from the illegal wild animal trade. The authors point out that trafficked birds are usually kept in overcrowded environments with poor hygiene, resulting in high stress levels that can suppress their immune systems. Such conditions can cause diseases to rapidly spread through bird populations. 

Although infectious diseases affected birds from all sources, the researchers discovered that they were more frequent in captive and rescued birds compared to wild birds. Also, the infection type varied depending on a bird’s origin. For example, captive birds were more frequently affected by bacterial, fungal, and viral diseases— some of which are transmissible to humans. In contrast, rescued and wild birds were more affected by viral and parasitic diseases, respectively.

Researchers also identified a number of non-infectious diseases in the birds they studied. Metabolic disease, which is caused by inadequate diet and dehydration, was the second most common cause of death after infections, affecting 26 birds. This disease was found mainly in captive and rescued birds. Trauma and fractures were the cause of death in 14 birds, most of whom were rescued from trafficking. Poisoning was identified as the cause of death in three captive birds who accidentally inhaled toxic gases from Teflon pans. It’s been established in research that heating Teflon can be toxic to birds. 

This study highlights the importance of understanding the different diseases that affect birds, not only for the well-being of individual animals but also to protect their species. The authors recommend that experts focus on monitoring captive and wild bird populations to detect and reduce disease transmission before it causes significant harm. 

From an animal advocacy perspective, it’s also important to note that diseases vary depending on a bird’s situation. For example, while we know that trafficking causes stress for individual animals, this study suggests that trafficked animals can suffer greatly even after they’re rescued. As such, advocates should highlight disease transmission as another welfare implication of the wild animal trade. Finally, advocates should make bird guardians aware of some of the illnesses common among captive birds (e.g., metabolic disease, cancer, and poisoning) and how they can address these issues to protect their companions.