Men, Women and Parasites: The Pleasantness of Smelling Urine

Still another finding about cats and “fatal attraction”:

Fatal Attraction Phenomenon in Humans – Cat Odour Attractiveness Increased for Toxoplasma-Infected Men While Decreased for Infected Women,” Jaroslav Flegr [pictured here], Pavlína Lenochová, Zdeněk Hodný, Marta Vondrová, PLoS Neglected Tropical Diseases, no. 5, vol. 11, epub November 8, 2012, e1389. The authors, at Charles University and at the Institute of Molecular Genetics ASCR, both in Prague, Czech Republic, report:

“Latent toxoplasmosis, a lifelong infection with the protozoan Toxoplasma gondii, has cumulative effects on the behaviour of hosts, including humans. The most impressive effect of toxoplasmosis is the so-called “fatal attraction phenomenon,” the conversion of innate fear of odour of the definitive host, the cat, into attraction to cat odour in rodents infected with Toxoplasma. While most behavioural effects of Toxoplasma infection were confirmed also in humans, neither the fatal attraction phenomenon nor any toxoplasmosis-induced changes in olfactory functions have been searched for in them. Our study performed on 34 Toxoplasma-infected and 134 noninfected students showed that the infected men rated odour of cat urine as more pleasant than did the noninfected men, while infected women rated the same odour as less pleasant than did noninfected women. No significant effect of toxoplasmosis on the urine odour pleasantness was found for horse, tiger, brown hyena and dog. The possible absence of the effects of toxoplasmosis on the urine odour pleasantness score attributed to tiger would suggest that the amino acid felinine, which is absent in urine of large cats, could be responsible for the fatal attraction phenomenon.”

Here is a chart from the study, about the odour pleasantness of urine that was attributed to horse, tiger, brown hyena and dog:

(Thanks to investigator Neil Martin for bringing this to our attention.)