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Toxic Birds

October 21, 2019

Introduction:

To consider something toxic, it must produce “an adverse biological effect” to humans or other animals (“Basic Terminology”). For birds, several species have adverse effects on humans through touch or ingestion. The remainder of this article explores several of these species including quail, pitohui birds, and spur-winged geese.

 

Quail:

Sources from the Roman Empire and the Bible document epidemics caused by the consumption of quail. The disease, referred to today as coturnism, only affected humans during certain migration periods. As the birds travel west to Europe, their flesh becomes deadly, but when they returned east, the birds are no longer toxic. Scientists believe the toxicity in quails comes from their own diet. Early speculation of quail toxicity thought the birds ingested plants like hemlock or henbane, but recent researchers believe that the culprit is Stachys annua, a plant that exhibits toxicity at consistent intervals with the quail migration (Bartram & Boland).

Stachys annua

Pitohui Birds:

The pitohui birds, native to New Guinea, have a neurotoxin originally only thought present in poison-dart frogs (found in Columbia and Central America). The toxin, present on the bird’s feathers and bodily tissue, if touched, can cause nausea, numbness, burning, and sneezing. With more exposure, the neurotoxin can lead to severe symptoms such as convulsions and contractions. (Bartram & Boland). The concentration of poison in the pitohui birds is 3-times less than that of the poison-dart frog. Contact with a frog can lead to cardiac arrest and death, but these extreme issues are much less common after contact with the pitohui birds (Ligabue-Braun & Carlini). The neurotoxins found in both pitohui birds and poison-dart frogs can only develop with appropriate diet. Poison dart frogs, when raised in captivity, no longer have the neurotoxin, and scientists assume the same is true for the birds. The specific ingredient that causes the poisonous neurotoxin remains unknown (Bartram & Boland). The low concentration of neurotoxins in pitohui birds causes some scientists to believe that the toxin developed evolutionarily to deter against parasites. Research shows that these birds have one of the lowest rates of tick infestations compared to other species in the area (Ligabue-Braun & Carlini).

Pitohui Birds

Other:

There are 13 other documented bird species that can harm or kill a human because of their own diet. Spur-winged geese, for example, eat a type of beetle that contains toxic material which causes severe skin blisters and death in humans (Bartram & Boland). More research is needed in the field of toxic birds to document reactions and determine causes of toxicity.

Spur-Winged Goose

Citations:

Bartram, S. and Boland, W. (2001), Chemistry and Ecology of Toxic Birds. ChemBioChem, 2: 809-811. doi:10.1002/1439-7633(20011105)2:11<809::AID-CBIC809>3.0.CO;2-C

“Basic Terminology.” U.S. National Library of Medicine, National Institutes of Health, toxtutor.nlm.nih.gov/01-002.html.

Ligabue-Braun, Rodrigo, and Célia Regina Carlini. “Poisonous Birds: A Timely Review.” Toxicon, vol. 99, 2015, pp. 102–108., doi:10.1016/j.toxicon.2015.03.020.

 

Picture Sources:

https://commons.wikimedia.org/wiki/File:Spur-winged_Goose_RWD4.jpg

https://en.m.wikipedia.org/wiki/File:Rectes_uropygialis_-_The_Birds_of_New_Guinea.jpg

https://commons.wikimedia.org/wiki/File:Stachys_annua_Sturm47.jpg

 

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.