Thanksgiving is later this week. I’m not the biggest fan of turkey. I asked my family if we could make steak or fish for Thanksgiving and I got three categorical No’s. Humans domesticated the turkey some 1500 years ago (N. Scharping. 2016. When Humans Domesticated the Turkey. Discover), but I still think that no amount of brining, roasting, grilling, or gravy can make turkey taste nearly as good as steak. Since I was thinking about this at work, my mind got all jumbled up between turkeys and our lab’s major interest, malaria. Scientists have long known that all kinds of birds get infected by malaria parasites. In fact, there is such a dizzying array of Plasmodium-like parasites that infect birds (as well as amphibians and other non-vertebrates) that a bunch of taxonomic reclassifications are apparently needed (Galen et al. 2018. Roy Soc Open Science. DOI: 10.1098/rsos.171780).
- Malaria in turkeys - The most common species of Plasmodium in turkeys in the U.S. is Plasmodium relictum, a species with a wide range in poultry and interestingly transmitted by the Northern house mosquito, Culex pipiens. Although Culex can transmit West Nile virus and other pathogens to humans, Culex do not transmit the species of Plasmodium parasites that infect humans.
- Bird malarias led to great discoveries relevant to our understanding of all malaria parasite species. Malaria parasites that infect birds have taught us an extraordinary amount about the Plasmodium lifecycle. For instance, the great malaria parasitologist Giovanni Battista Grassi suggested that there must be a hiding place for parasites AFTER an infectious mosquito bite but BEFORE the emergence of the parasites in the blood stage. In 1898, it was the bird malaria parasite P. relictum (a favorite of holiday turkeys!) that was observed in liver and spleens of infected birds (MacCallum. 1898. J Exp Med 3:117). This and other findings eventually helped reveal the “pre-erythrocytic” phase in primate malarias (Shortt et al. 1948. Nature 161:126), which is now the major focus of vaccine development for our lab and many others.
- How does a bird even get bitten by mosquitoes? Presumably like you and me anywhere on their exposed skin, but this photo of a canary's feet being fed upon by P. relictum-infected Culex mosquitoes adds an interesting new dimension and makes me want to wear shoes even more (Kazlauskiene et al. 2013. Exp Parasitol 133:454).
- Malaria produces chronic side effects in asymptomatically-infected birds: P. relictum usually doesn't cause obvious clinical illness in birds, but a 2015 report in Science showed that infected birds produced fewer eggs, were less successful at rearing offspring, had significantly shortened telomeres (an outcome that was also seen in their chicks). There’s a nice summary of that study in the Audubon Magazine – with another amazing photo of a mosquito feeding on a bird’s eye.
So even though it doesn't taste like steak, all hail the Thanksgiving turkey today.
Happy Thanksgiving!