Polymorphism in Trypanosoma simiae and the morphology of the metacyclic forms

Characterization of trypanosome isolates from naturally infected horses on a farm in Kenya

Following an outbreak of trypanosomosis in horses on a farm in Kenya, 18 trypanosome isolates were collected from the infected animals over a period of one and a half years and cryopreserved for characterization. The characterization was done on the basis of morphology using Giemsa-stained blood and buffy coat smears, infectivity to mice, recombinant DNA hybridization, and chromosome separation by orthogonal field alternation gel electrophoresis (OFAGE). Morphologically, all the trypanosome isolates were identified as belonging to the subgenus Nannomonas, and a total of 16 out of the 18 isolates grew in mice. Using the recombinant DNA hybridization technique, the isolates were further classified as the 'savannah' type of Trypanosoma congolense. Furthermore, chromosome separation by OFAGE, carried out on six clones derived from different isolates, exhibited a profile characteristic of T. congolense, 'savannah' type. However, there were differences in the number and positions of the medium-sized and minichromosomes indicating a diversity of serodemes within the isolates. Hence the infecting trypanosomes in this disease outbreak were T. congolense, 'savannah' type, and comprised several serodemes or strains.

In vitro development of metacyclic Trypanosoma simiae derived from bloodstream trypomastigotes

A stock of Trypanosoma simiae was transformed into procyclic forms at 26 C in a semi-defined maintenance medium. After transformation, the trypanosomes were maintained in a modified Eagle's MEM medium. On day 35 of cultivation, epimastigotes attached to the bottom of the culture flask. From day 44 onwards, metacyclic-like trypanosomes were observed. Subcutaneous injections into pigs of trypanosome suspensions obtained from cultures on day 10 were not infective, whereas culture-derived metacyclics (days 44, 63 and 69) were highly pathogenic.

Isolation and cultivation in vitro to the infective, metacyclic stage of Trypanosoma (Nannomonas) simiae from Glossina morsitans submorsitans

Two separate trypanosome isolations were made from a single Nannomonas-infected Glossina morsitans submorsitans from The Gambia. Inoculation of a piglet with the infected hypopharynx produced an infection with Trypanosoma simiae. DNA was isolated from the bloodstream forms to prepare a probe specific for this species. Trypanosomes isolated from the fly midgut were frozen in liquid nitrogen and then cultivated in vitro. Amplification of this population and elimination of a yeast contaminant were achieved by two passages through laboratory G. m. morsitans. Further cultivation in vitro resulted in the production of epimastigotes and, later, metacyclic forms. Two pigs inoculated with cultivated metacyclic forms developed infections with atypical, relapsing parasitaemias and extended survival time. Neither the metacyclic forms, nor bloodstream forms derived from them, infected calves. The identity of various stages of the in vitro cultivated, procyclic-derived stock was confirmed morphologically and with the T. simiae-specific DNA probe.

Morphological and taxonomic studies on mammalian trypanosomes. IX. Revision of Trypanosoma dimorphon

Owing to inadequate and conflicting descriptions, there have always been doubts about the identity of Trypanosoma dimorphon, which is commonly regarded as a synonym of T. congolense. However, the occurrence of atypical strains, with characters like those of T. dimorphon, has re-opened the question of the possible independence of this species.

To solve this problem, the author has undertaken a complete revision of T. dimorphon, based on Laveran and Mesnil's original type-material. In the course of this work, a total of 1200 trypanosomes, belonging to samples taken from animal passages in the course of 4 years, were studied biometrically and morphologically.