title: Morbid attraction to leopard urine in Toxoplasma-infected chimpanzees.
abstract: Parasites are sometimes capable of inducing phenotypic changes in their hosts to improve transmission [1]. Toxoplasma gondii, a protozoan that infects a broad range of warm-blooded species, is one example that supports the so-called 'parasite manipulation hypothesis': it induces modifications in rodents' olfactory preferences, converting an innate aversion for cat odor into attraction and probably favoring trophic transmission to feline species, its only definitive hosts [2]. In humans, T. gondii induces behavioral modifications such as personality changes, prolonged reaction times and decreased long-term concentration [3]. However, modern humans are not suitable intermediate hosts because they are no longer preyed upon by felines. Consequently, behavioral modifications in infected people are generally assumed to be side effects of toxoplasmosis or residual manipulation traits that evolved in appropriate intermediate hosts. An alternative hypothesis, however, states that these changes result from parasite manipulative abilities that evolved when human ancestors were still under significant feline predation [3,4]. As such, T. gondii also alters olfactory preferences in humans; infected men rate cat urine, but not tiger urine, as pleasant while non-infected men do not [5]. To unravel the origin of Toxoplasma-induced modifications in humans, we performed olfactory tests on a living primate still predated by a feline species. We found in our closest relative, the chimpanzee (Pan troglodytes troglodytes), that Toxoplasma-infected (TI) animals lost their innate aversion towards the urine of leopards (Panthera pardus), their only natural predator. By contrast, we observed no clear difference in the response of TI and Toxoplasma-non-infected (TN) animals towards urine collected from other definitive feline hosts that chimpanzees do not encounter in nature. Although the adaptive value of parasitically induced behavior should be assessed carefully, we suggest that the behavioral modification we report could increase the probability of chimpanzee predation by leopards for the parasite's own benefit. This possible parasite adaptation would hence suggest that Toxoplasma-induced modifications in modern humans are an ancestral legacy of our evolutionary past.
authors: CEFE-CNRS UMR 5175, 1919 Route de Mende, 34293 Montpellier Cedex 5, France. Electronic address: c.poirotte@gmail.com.
authors: Clémence
authors: C
authors: Poirotte
authors: Behavioral Ecology and Sociobiology Unit, German Primate Center, Kellnerweg 4, 37077 Göttingen, Germany.
authors: Peter M
authors: PM
authors: Kappeler
authors: Centre de Primatologie, Centre International de Recherche Médicale de Franceville (CIRMF), BP 769, Franceville, Gabon.
authors: Barthelemy
authors: B
authors: Ngoubangoye
authors: Agence Nationale des Parcs Nationaux, Libreville, Gabon.
authors: Stéphanie
authors: S
authors: Bourgeois
authors: SODEPAL, BP 52, Bakoumba, Gabon.
authors: Maick
authors: M
authors: Moussodji
authors: CEFE-CNRS UMR 5175, 1919 Route de Mende, 34293 Montpellier Cedex 5, France.
authors: Marie J E
authors: MJ
authors: Charpentier
mesh_terms: D000818:Animals; D005260:Female; D020387:Food Chain; D008297:Male; D002679:Pan troglodytes; D046009:Panthera; D012903:Smell; D014122:Toxoplasma / Q000502:physiology*; D014124:Toxoplasmosis, Animal / Q000469:parasitology / Q000503:physiopathology*; D014556:Urine