Evaluating the use of packed cell volume as an indicator of trypanosomal infections in cattle in eastern Zambia

Abstract

In this study, packed cell volume-values (PCV) are evaluated as indicator of trypanosomiasis infections in cattle. A total of 734 blood samples were collected in 11 different sampling sites in eastern Zambia: 84 calves (<1 year), 52 young females and 40 young males (between 1 and 3 years), 228 cows, 317 oxen and 13 bulls (>3 years). All samples were subjected to three diagnostic tests: parasitological examination using the buffy coat method, PCR/RFLP and PCV determination. The results were compared and analysed in a Bayesian model, which allowed the estimation of the infection prevalence and the respective test sensitivities and specificities. The presence of a trypanosomal infection significantly reduced the PCV, independently of the age and sex of the infected animal. The estimated prevalence of trypanosomal infections in the study area was 34% (95% credibility interval: 30-38%). While the specificity of both the parasitological and the PCR/RFLP tests were set to 1, the parasitological diagnosis had a low sensitivity (37%) compared to the PCR/RFLP (96%). When using a cut-off value of 24, the PCV had a high specificity (98%) but a rather low sensitivity (53%) for identifying trypanosomiasis infections. Using 26% as a cut-off increased the sensitivity to 76% without much affecting the specificity (94%). A parallel combination of the parasitological diagnosis and the PCVimproved the diagnostic sensitivity (74% and 89% for PCV cut-off values of 24% or 26%, respectively) while specificity remained high (98% and 94% for PCV cut-off values of 24% or 26%, respectively). These results suggest that such a combination could advantageously be used for the diagnosis of cattle trypanosomiasis in the field: it is much www.elsevier.com/locate/prevetmed more sensitive than parasitological examination alone and it is much cheaper than molecular tests. However, the value of this approach depends largely on the determination of an appropriate cut-off value to consider a sample positive, depending on the required test sensitivities and specificities. #

Bovine trypanosomosis: A threat to cattle production in Chena district, southwest Ethiopia

“…Such significant difference of PCV values in infected and non-infected cattle had been reported by several workers [26][27][28]. They demonstrated that haematocrit values of infected cattle decreased during the infection period.…”

Baseline survey of animal trypanosomosis in the region of the Boucle du Mouhoun, Burkina Faso

“…This value of 26% constitutes a threshold that is a valuable indicator of trypanosomal infections when associated with the parasitological results (Marcotty et al, 2008). The low proportion of anaemic animals is a strong signal that treatments are effective in this area and that the health condition of the animals can be maintained even in the presence of the parasites and their vectors.…”

Prevalence of Trypanosoma brucei brucei and Potential In Vitro Trypanocidal Activity of Aqueous Extracts of Some Medicinal Plants in the Pastoral Area of Gaongho in Burkina Faso

“…This could be explained by the effects of climate change and anthropogenic actions on natural resources in the area in recent years that have contributed to the current transformation of tsetse ecology for their survival (Dao et al al., 2008;. This could be added to the diagnostic method used in the study which is less sensitive than the PCR technique using parasite-specific primers which is more sensitive and allows to have higher prevalences (Desquesnes et al, 1999;Marcotty et al, 2008).…”