Systematic review and meta-analysis on the global distribution, host range, and prevalence of Trypanosoma evansi

Authors: AREGAWI, WELDEGEBRIAL - Ethiopian Institute Of Agricultural Research; Agga, Getahun; ABDI, RETA - Long Island University; BUSCHER, PHILIPPE - Institute Of Tropical Medicine

Submitted to: Parasites & Vectors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2019
Publication Date: 1/31/2019
Publication URL: https://handle.nal.usda.gov/10113/6296987
Citation: Aregawi, W.G., Agga, G.E., Abdi, R.D., Buscher, P. 2019. Systematic review and meta-analysis on the global distribution, host range, and prevalence of Trypanosoma evansi. Parasites & Vectors. 12:67. https://doi.org/10.1186/s13071-019-3311-4.
DOI: https://doi.org/10.1186/s13071-019-3311-4

Interpretive Summary: Surra is animal disease caused by Trypanosoma evansi, a protozoan parasite. The disease is transmitted through the bite from various species of flies. The disease leads to a debilitating condition with severe economic losses through sickness and death of infected animals. In this study we reviewed geographic and host distribution of the parasite, and quantified the magnitude of infection in animal hosts. The disease was reported from 48 countries, 37 of these are from Africa and Asia. Surra was reported from all farm animal species and wide range of wild animals. Camels were the most affected with the infection rate reaching up to 31%. Our study identifies the widespread of this devastating animal disease severely affecting the developing countries. The role of wild animals for the maintenance of the disease requires further investigation for planning control programs.

Technical Abstract: Background Surra is an animal trypanosomosis, caused by infection with Trypanosoma evansi and leading to severe economic loss due to mortality and morbidity. Compared to tsetse-transmitted animal trypanosomoses, little attention is given to the epidemiology and control of surra. Understanding its epidemiology is a first step in local and global efforts to control the disease. We conducted a systematic review and meta-analysis of published studies on distribution, host ranges and prevalence of T. evansi infection. Methods Four electronic databases were searched for publications on T. evansi that met our inclusion criteria for the systematic review. Subsets of publications were subjected to meta-analysis for the pooled prevalence of T. evansi in various hosts as determined by multiple detection methods. Results A total of 272 references published between 1906–2017 were included. Trypanosoma evansi was reported from 48 countries; largely confined to Africa and Asia with publications on natural T. evansi infections from 77% (n = 48) of countries, contrasting with seven countries in South America, and four in Europe where T. evansi is not endemic but was imported with infected animals. Although surra is a notifiable disease, many countries do not report surra cases to OIE. Trypanosoma evansi was mainly reported from dromedary camels in Africa and the Middle East, water buffaloes, cattle, dogs and horses in East and Southeast Asia. In South America, the acute form of the disease was reported in horses and dogs. Surra was also reported in a wide range of wild animals. Some rare human cases occurred in India and Vietnam. Meta-analysis on a subset of 165 publications indicated pooled prevalence of T. evansi in domestic animals ranging from 14–31%, 6–28% and 2–9% using respectively antibody detection, molecular and parasitological tests, with camels as the most affected, followed by buffalo and cattle. Conclusions This study illustrates that T. evansi affects a wide range of domestic and wild animals in Africa, Asia and South America with highest prevalence observed in dromedary camels. For successful control of T. evansi, both locally and globally, the role of wild animals in the epidemiology of surra needs further investigation.