The Sensitivity of Ice Pack Preserved Trypanosoma Evansi to Different Parasitological Diagnostic Methods

Abstract

The aim of this study is to determine the sensitivity of ice pack preservation of Trypanosomaevansi to some parasitological diagnostic techniques like wet blood film (WBF), haematocrit centrifugation test (HCT) and mice inoculation test (MIT). Three millilitres each of blood containing approximately 10 x 10³ T. evansi/ml was placed in four different sample bottles and preserved in an insulated flask containing ice at 5 0C. WBF & HCT were used prior to ice preservation and at 4, 8, 12, 24, and 36 hrs post ice preservation to observe for the presence of motile trypanosomes. A total of 8 mice, two per sample were inoculated intraperitonealy with 0.2mls of the blood samples at each time interval of preservation. The level of parasitaemia was also estimated at each time of preservation by c ount ing the number of live trypanosomes in wet film preparation of the buffy coat materials of each sample under phase contrast microscopy. Decrease in the sensitivities of the tests were noticed as follows: from 100% at 0 – 8 hrs to 75% at 12 hrs and 50% at 36 hrs post preservation for WBF; from 100% at 0 – 12 hrs to 75% and 50% at 24 and 36 hrs post preservation respectively for HCT; and from 100% at 0 – 8 hrs to 63%, 38% and 25% at 12, 24 and 36 hrs post preservation for MIT. Increase in pre-patent periods from 3 days to 21 days in mice inoculated at 0 hr & 36 hrs post preservation respectively were observed Significant decrease (P < 0.001) in mean parasitemia of the preserved infected blood samples was noticed at 24 and 36 hours post preservation. The duration of preservation of the infected blood sample statistically correlated with parasitaemia in the preserved blood samples (r = - 0.95; P < 0.05) and with pre-patent period (r = 0.93; P < 0.05) in the inoculated mice.

Keywords: Ice pack preservation, Trypanosoma evansi, viability, infectivity

Nigerian Veterinary Journal, VOL:33 (2) 505-510