Latent Haemobartonellosis in the squirrel monkey (Saimiri sciureus), a New World primate:: a study conducted at the Primatology Center of the Pasteur Institute of French Guyana.

In the scope of its research programmes on the development of a malaria vaccine against Plasmodium falciparum, the Pasteur Institute developed a primate model in the 1980s, based on the squirrel monkey (Saimiri sciureus). Recent work carried out at the Primatology Center of the Pasteur Institute of French Guyana (CP-IPG), where a colony of these monkeys is based, shows that a large number of these primates are asymptomatic carriers of haemotrope prokaryotes of the genus Haemobartonella, member of the Rickettsiales. The infection due to Haemobartonella sp. - latent in the majority of the colony's animals - becomes apparent after splenectomy. Microscopic observation of Giemsa-stained blood smears reveals the presence of coccoid micro-organisms on the surface of the erythrocytes. Haemobartonellosis occurs in 75 % of the animals between 2 and 4 days after splenectomy. The infection, which is easily reproducible, comes to a peak between day 12 and day 14 before regressing and disappearing altogether one month after splenectomy. The pathological signs are generally moderate. Anaemia is the major clinical symptom during the acute phase of the infection, while the latent infection is completely asymptomatic. A few atypical cases show severe haemolytic anaemia, sometimes leading to the death of the animal. As yet, little is known as to treatment of this disorder. Oxytetracycline seems of little use but arsenic derivatives such a neoarsphenamine might be a good alternative. Furthermore, research at the CP-IPG has shown that infection due to Haemobartonella sp. may modify the course of the parasitaemia due to Plasmodium falciparum, the lethal agent of human malaria. These competitive interactions show the need to control the possible presence of Haemobartonella sp., especially during the evaluation of antimalaria vaccines. Finally, according to recent work based on the phylogenic analysis of molecular data, this little known micro-organism could well be related to the Mycoplasma family.