Hunting alters viral transmission and evolution in a large carnivore (2022) Fountain-Jones et al., Nature Ecology & Evolution, https://doi.org/10.1038/s41559-021-01635-5
Image credit: Joachim S. Müller, CC BY-NC-SA 2.0
It’s no secret than humans have had an enormous impact on the native wildlife of our planet, and we have looked into many of these complicated relationships and effects before on Ecology for the Masses. One common interaction is that of hunting, whereby humans hunt and kill an animal for recreation and/or food. Regardless of your feelings on hunting, such removal of animals can be an issue in systems where there is density-dependent transmission, meaning the more animals there are, the more likely there is to be parasite transmission within the populations of these animals. Reducing animal populations via hunting can either decrease, have no effect on, or even increase density-dependent transmission.
These changes in transmission dynamics (and subsequent changes in infection patterns) will have effects on the evolution of the parasites infecting these animals, making it easier for researchers to detect if (and how much) transmission is occuring. To investigate these patterns, today’s authors studied data on feline immunodeficiency virus (FIV) and its puma (Puma concolor) hosts. FIV is mostly benign and infects its hosts for life, though puma hosts can become infected with different strains of FIV. The goal of today’s study was to understand how hunting affects transmission dynamics of FIV within populations of puma that are hunted.
Viruses are weird – they are non-living, yet still contain genetic information and are dependent on a live host to actually replicate and survive. Unlike many other parasites, since viruses are basically just a string of DNA or RNA, they actually need to actually get inside the cells of their host and hijack some of the components of these cells to allow them to replicate. After infection they are (at least partially) in the driving seat and can control and manipulate how some cells behave.
This means that viruses often have the capacity to also alter the behaviour of their host – which can be particularly beneficial to help ensure that the virus can also spread from one host to another. A good example is rabies, whereby the virus triggers infected individuals to become exceptionally aggressive – a surefire way to probably lead to them biting another individual and allowing infection to occur via the bite wound.
Sometimes the behavioural changes can be more nuanced – in this case caterpillars infected by a baculovirus start perceiving then sun in a positive light (pun definitely intended). Infected caterpillars become attracted to sunlight and feel compelled to move towards it (this process is known as phototaxis). Unfortunately in this case is is drawing them to an untimely death. Having the caterpillars die near the tree canopy is beneficial for the virus, as its a better scouting ground for newer hosts.
Read more: Baculoviruses hijack the visual perception of their caterpillar hosts to induce climbing behaviour thus promoting virus dispersal
Tanya Strydom is a PhD candidate at the Université de Montréal, mostly focusing on how we can use machine learning and artificial intelligence in ecology. Current research interests include (but are not limited to) predicting ecological networks, the role species traits and scale in ecological networks, general computer (and maths) geekiness, and a (seemingly) ever growing list of side projects. Tweets (sometimes related to actual science) can be found @TanyaS_08.