A meta-analysis of the prevalence of African animal trypanosomiasis in Nigeria from 1960 to 2017

Abstract

Background: African animal trypanosomiasis is an economically significant disease that affects the livestock industry in Nigeria. It is caused by several parasites of the genus Trypanosoma. National estimates of the disease prevalence in livestock and tsetse flies are lacking, therefore a systematic review and meta-analysis were performed to understand the trend of the disease prevalence over the years.

Methods: Publications were screened in Web of Science, Ovid MEDLINE, Global Health, EMBASE and PubMed databases. Using four-stage (identification, screening, eligibility and inclusion) process in the PRIMSA checklist, only studies that met the inclusion criteria for AAT and tsetse infections were analysed. Point estimates prevalence and subgroup analyses based on diagnostic techniques in livestock were evaluated at 95% confidence interval (CI).

Results: A total of 74 eligible studies published between 1960 and 2017 were selected for meta-analysis. This covers the six geopolitical zones, involving a total of 53,924 animals. The overall prevalence of AAT was 16.1% (95% CI: 12.3-20.3%). Based on diagnostic techniques, the prevalence of AAT in cattle was highest in PCR followed by serology and microscopy while the highest prevalence in pigs was observed with serology. Out of 12,552 tsetse flies examined from 14 eligible studies, an overall prevalence of 17.3% (95% CI: 4.5-36.0%) and subgroup prevalence of 49.7% (95% CI: 30.7-68.8%), 11.5% (95% CI: 6.1-18.5) and 4.5% (95% CI: 1.8-8.8%) in G. morsitans, G. tachinoides and G. palpalis, respectively, were observed using the random effects-model.

Conclusions: The prevalence of trypanosomes in both vectors and animal hosts was high in Nigeria. Therefore, further research on risk factors, seasonal and transhumance effects, vectoral capacity and competence are warranted for an effective control of AAT in Nigeria.

Keywords: Livestock; Nigeria; Prevalence; Trypanosomes; Tsetse.

Fig. 1

Flow diagram detailing the selection of eligible studies and excluded studies in a systematic approach for the prevalence of AAT and tsetse infections in Nigeria

Fig. 2

Forest plot of the prevalence estimates of AAT in animals in Nigeria between 1960–2017 [, –, , , , –105]

Fig. 3

The prevalence of AAT in Nigeria over six decades. Tukey multiple pairwise comparison test of the analysis of variance shows no significant difference (F_{(5, 68)} = 1.616, P = 0.1676, r² = 10.6%) in the prevalence reports across decades. Proportions of each study conducted (74 studies) and total number of animal screened is shown in the graph

Fig. 4

Forest plot of the prevalence estimates of trypanosome-infected tsetse flies in Nigeria between 1960–2017 [, , , , , , , –112]

Fig. 5

Nigeria states showing the intensity of trypanosomiasis studies conducted between 1960–2017