The effects of different storage temperature conditions on the infectivity of Trypanosoma brucei in mice in Southeastern Nigeria

Abstract

The effects of storing Trypanosoma brucei in different temperature conditions were studied using 55 adult female albino mice weighing between 18 and 33 g. The mice were divided into six groups. Groups 2–6 comprised ten mice each while group 1 comprised five mice and served as the control. Groups 2–6 were each further subdivided into two sub-groups of five mice each. Storage temperature conditions were room temperature (25–28 °C) (bench) and refrigeration temperature (4 °C). The onset of parasitaemia and packed cell volume were monitored. Groups 1–6 were infected intraperitoneally with 1.0 × 10⁶ trypanosomes at 0, 3, 6, 9, 12 and 24 h, respectively, following blood sample collection and storage. It was observed that the parasites in both temperature conditions were all active till the 9th hour of storage. However, the parasites stored at room temperature (bench) were sluggish and weak compared to the very active parasites in the group stored in the refrigerator by the 12th and 24th hours of storage. A pre-patent period of 4–8 days was recorded for all infected mice despite their storage condition. Surprisingly, the parasites in both storage conditions irrespective of time of infection produced patent infections. However, the pre-patent periods were highest for mice infected at both 12 and 24 h of storage. There were no significant differences (p < 0.05) in the mean packed cell volume between groups infected with blood stored at either temperature prior to infection irrespective of the time of infection. We therefore conclude that trypanosomes in blood samples are infective for up to 24 h either at room temperature or at the refrigeration temperature (4 °C). Even so, for optimum infectivity, the infected blood should be used for infection within 9 h of collection.