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Table 2 Historical overview of the studies describing unusual infections caused by monoxenous trypanosomatids

From: The evolution of trypanosomatid taxonomy

Year Reference Description
1980 McGhee & Cosgrove [88] Report of a possible monoxenous infection in a woman from Texas presenting with ill-defined symptoms. Examination of the cultures excluded the possibility of Leishmania or Trypanosoma infection, and suggested the organism was a Herpetomonas sp.
1986 Githure et al. [143] Trypanosomatids isolated from HIV-negative patients in Kenya were revealed to be more closely related to Crithidia species through iso-enzyme and kDNA analyses, than that of Leishmania.
1988 Morsey et al. [93] An unnamed trypanosomatid species was isolated from rats and stray dogs in Egypt in 1989 by Morsey et al. (1988). The rodent/canine isolate was later found to be a member of the genus Herpetomonas [94].
1989 Conchon et al. [144] Crithidia ancanthocephali, Crithidia fasciculate, Crithidia thermophile, Leptomonas seymori, Herpetomonas samuelpessoai were used to experimentally infect tomato plants (Lycopersicon esculentum).
1991 Sabbatani et al. [145] A case of unusual visceral leishmaniasis was reported in a HIV-positive 10-year-old girl from Guinea-Bissau, where the disease had not been previously identified. It was speculated that this case resulted from an infection with a reptilian trypanosomatid that had not been identified in humans previously.
1992 Mebrahtu et al. [146] Parasites isolated from HIV-negative patients suffering from visceral leishmaniasis were described as resembling Crithidia species rather than the pathogenic Leishmania.
1996 Jimenez et al. [147] An “unusual Leishmania-like parasite” was reported in a case of visceral leishmaniasis/HIV co-infection.
1998 Pacheco et al. [89] A monoxenous trypanosomatid was isolated from the bone marrow of an HIV patient presenting with a visceral leishmaniasis-like syndrome. The patient was positive for a Leishmania braziliensis infection. Molecular analyses also revealed a co-infecting parasite that did not belong to the genus Leishmania or Trypanosoma and hybridisation analyses confirmed kinetoplast DNA (kDNA) cross-hybridisation with Leptomonas pulexsimulantis.
2007 Srivastava et al. [91] Report of nine cases of visceral leishmaniasis in patients from India. PCR analysis revealed the presence of both Leishmania donovani and a Leptomonas species designated Leptomonas sp. BHU. It was proposed that the monoxenous flagellates were able to infect these patients due to immune-suppression associated with visceral leishmaniasis.
2012 Ghosh et al. [85] In a study of Indian Leishmania donovani infected patients, 4/29 (13.8%) patients with visceral leishmaniasis and post-kala-azar dermal leishmaniasis (PKDL) were co-infected with the previously identified Leptomonas sp. BHU, which was later confirmed as Leptomonas seymouri.
2013 Singh et al. [80] Through whole genome sequencing of the L. donovani clinical isolates from India, the presence of monoxenous trypanosomatids in cases of visceral leishmaniasis was reported as Leptomonas seymouri. It is important to note that a recent study by Kraeva et al. found that some of the DNA sequences of Leptomonas seymouri were misidentified as Leishmania donovani in GenBank [53].
  1. Note: A case of diffuse cutaneous infection caused by a presumably monoxenous parasite was reported in 1995 in an immunocompromised patient infected with HIV [148]. The same parasite isolated in 1995 by Dedet et al. was reported in an immunocompromised patient from Martinique causing a localised cutaneous lesion [149]. This parasite has since been confirmed as Leishmania martiniquensis [150] and so has been excluded from the table