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Originally posted in August 2009.

Feral_CatOne topic that I find particularly interesting concerns how personality traits influence patterns of disease.  For example, people who are frequently stressed out are at a greater risk of becoming obese or acquiring heart disease. We often look at disease transmission at a population or community level, but I think individual level differences in behavior are a crucial and understudied area of research.

When diseases are transmitted from one individual to another, then social behaviors are an important factor in transmission dynamics. While it’s often difficult to study this phenomenon in humans, numerous social animals provide ideal study systems.

Natoli et al. 2005 is 0ne of the coolest studies that I’ve read on personality traits and disease. This research group examined 3 colonies of feral domestic cats in Europe and collected data on how male personality traits correlated with FIV (feline immunodeficiency virus) infection. According to the article, FIV infections in feral cats are usually lethal within approximately 5 years, at which point the cat’s immune system is too weak to fend off otherwise nonlethal infections.

FIV transmission occurs when one cat bites another, transmitting the virus from its saliva into the other cat’s bloodstream. Bites usually occur when two males are battling over territory or dominance rank or when a male bites a female during sex.

Feral_Cat_2In order to get a handle on the “personality” of the feral cats in each colony, the researchers logged hundreds of hours taking notes on the frequency with which each cat engaged in aggressive, submissive, affiliative, territorial, display or mating behaviors. They aggregated all of these measures and came up for a single score for each individual that indicated how “proactive” or “reactive” that individual was. Proactive cats more regularly marked their territory, were the most aggressive (often winning aggressive interactions) and often affiliated with other members of the colony. Reactive individuals rarely displayed aggressive behavior and were frequently submissive towards other members of the colony.

When the behavioral results were compared with information about which cats were infected with FIV, a clear patterns emerged. The males at the top of the hierarchy (i.e., the most proactive, dominant males) were the most likely to be infected with FIV. Their aggressive demeanor meant that they incurred bites more frequently than more submissive males, increasing the probability that aggressive males contracted the disease.

This finding brings up a logical question. If all of these aggressive cats are contracting terminal diseases, why are aggressive cats still around? Well, the first answer to that question lies in that fact the cats don’t succumb to the illness quickly. The disease has a long asymptomatic period during which the cats continue to strut around as if nothing is wrong.

Importantly, aggressive behavior also maintains access to the ladies. Paternity tests revealed that the proactive cats were fathering a lot more of the kittens than the reactive males. Because aggressive dads produce more offspring than submissive dads, we might not expect aggressive behavior to be diminishing anytime soon.

This was a particularly nice study because it examined multiple populations (lending support to the generality of the results), measured lots of behaviors, and included a direct measure of evolutionary fitness. It’s rare to find so comprehensive a study.

When dealing with socially transmitted diseases, personality plays a large role in the number of times an individual may be exposed to an infectious agent. In the study described above, aggressive behavior was the key to transmission. In other systems the important relevant measures may be frequency of sexual behavior, energy put into hygiene, number of individuals with which one associates, etc. Personality plays a large role in determining the diseases to which one is most susceptible.

24 Responses to “Personality and disease transmission”

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  2. miningzen

    Happy Birthday!

  3. JD

    HAPPY BIRTHDAY, NERD!

  4. DesertPlah

    Bappy Hirthday!

  5. Tantalus

    Happy Birthday!

  6. Saufsoldat

    HAPPY BIRTHDAY, NERD!

  7. Matt

    HAPPY BIRTHDAY, NERD!

  8. Chris Morin

    Happy Birthday, Nerd!

  9. derp

    Happy Birthday Nerd! <3 + thank you for this awesome blog!

  10. Anonymous

    HAPPY BIRTHDAY, NERD.

  11. Internet Dude

    HAPPY BIRTHDAY, NERD!

  12. Hierro

    HAPPY BIRTHDAY, NERD

  13. Josh Heggen

    Me, I wonder several things:
    How does one conduct a longitudinal study on cats effectively, especially feral ones? I’m imagining some form of chipping, combined with a lifelog device, like one sees some hobbyists tinkering with these days. In essence, a camera collar with a WiFi sim card.

    Also, how do FIV and Toxoplasma gondii coexist and interact within these cat populations? What would the behavioral modification of the second do to the incidence rate of the first?

    Thirdly, are you having a happy birthday, nerd? 😉

    • weinersmith

      The feral cats stayed in a fairly central location (or at least came back regularly) so they were able to identify them by their markings. They trapped them to collect blood and other data, but it looks like it was just a lot of grad students hour sitting around watching cats. 😉

      Good question! I’m not sure how FIV and T. gondii interact. I’m not aware of T. gondii inducing behavioral changes in cats and behaviorally manipulative parasites usually don’t cause much harm to their definitive hosts. They need these hosts to stay healthy so they can continue to defecate all over the place, spreading the parasite around.

      I’m having a great birthday! Thanks! Thanks for reading and asking questions! 🙂

  14. Bregalad

    Is there evidence of cats becoming more aggressive with age. Or of them becoming more aggressive after contracting FIV?

    And Happy Birthday!

  15. Mr Z

    Is it totally impossible to generalize population stats regarding stress, lifestyle etc?

    It might take some effort, but collating foreclosure/reposition information across an semi isolated population along with medical statistics, Google trends info etc, you should be able to estimate stress levels in a generalized way. If disease correlates linearly in several sample trials using such methods, you may find ways to further isolate documented stress factors for the society in which they occur. Police data can be used also: drug / alcohol related incidents by district, divorce proceedings by district and on. There are many things which can indicate strong stress factors for any section of population. In the area under study, the number of thriving daycare centers and fast food restaurants etc. can tell you many things. Fire department incident reports and others can give you a glimpse into a neighborhood’s social stress levels. Graffiti and gang tagging can tell you much as well. There are hundreds of sources of strong indicators as to what social stress factors are at work. None of these are invasive and are signs of what is happening in general. The local hospital emergency room stats can tell you much too. If 90% of their incidents are sports related rather than fights/accidents it says something.

    Google itself has much of this data logged. You might be able to get strong indicators of the problems and inferred causal relationships sitting at the computer.
    Google is your friend… and is recording all you do in some fashion. It would be a lot of work to collate the data, but it’s out there to be used. If you can get clinic stats on the number of reported colds/flu their clients are nearly 100% local to their business. You could pay students to count people in the mall(s) local to your population to estimate obesity levels across the local populace and other such efforts which are not invasive to get generalized but strong indicators.

    I’d like to see studies of what the situation is when there are more generally healthy options available than unhealthy options. More than average healthy food sources, less than average fast food establishments etc. Are there semi-linear fluctuations in population health and happiness?

    Very interesting.

    • Mr Z

      Gahh, the spiel chequeuer got me… reposition should be repossession.

    • Mr Z

      Interesting. In replying to your post I got the ‘bug’ and had to look around a bit. The studies that are available looking at the link between health and wealth : http://www.google.com/search?hl=en&output=googleabout&btnG=Search+our+site&q=relationship%20between%20wealth%20and%20health are abundant. Now, to write an app that uses Google data to plot property value against fast food restaurants and other ‘common’ or stereotyped indicators of wealth status. Very interesting… perhaps an Android app that can tell you whether you are likely to be surrounded by obese people who are likely to have the flu based on GPS… ahahahahaha, yep, that’s the ticket.

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  17. Jake

    HAPPY BIRTHDAY, NERD!

  18. Black Bloke

    Happy belated birthday Kelly 😉

    And after having seen you in person I conclude Zach is right, you are totally hot. Also intelligent and stuff…

  19. radleft

    Happy Birthday – Nerd! By the way, love your blog. There’s no way parasites that big can’t affect behavior. Heck, they’d change the way I moved if they were on me and proportionate. Cat society has always intriqued me. They go from one type of social behavior below a certain population density – to a very different social behavior above that limit, I would have loved to assisted on that study. And…Happy Birthday – Nerd!

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  21. Suchmaschine

    To start earning money with your blog, initially use Google Adsense but gradually as your traffic
    increases, keep adding more and more money making programs to your site.
    thanks !! very helpful post!

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