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

Abstract

BackgroundSurra 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.MethodsFour 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.ResultsA 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.ConclusionsThis 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.Electronic supplementary materialThe online version of this article (10.1186/s13071-019-3311-4) contains supplementary material, which is available to authorized users.

Prevalence of Trypanosoma evansi in livestock in Palestine

“…The infection level depends on the infective dose injected by the vector and the time elapsed between ingesting the blood of an infected animal and biting an uninfected animal. Trypanosoma evansi does not develop in the vector like other Trypanosoma species but rather survives in the oral cavity of the vector [17]. Therefore, the use of molecular-based methods rather than wet mounts for T. evansi screening is recommended.…”

“…Hematophagous horseflies of the genus Tabanus and stable flies of the genus Stomoxys [6] seem to play an important role in the mechanical transmission of T. evansi; transmission can also occur through the contamination of a wound with infected animal blood [13]. The wide range of parasite hosts contributed to its geographical spread in 48 countries throughout the world [6,[14][15][16][17]. The disease can cause significant economic damage mainly due to reduced milk yields, decreased animal market values and annual mortality rates affecting thousands of animals [4,18,19].…”

Trypanocidal Essential Oils: A Review

“…Both trypanosomes invade the brain, causing mental deterioration, coma and death if left untreated [ 4 , 5 ]. There is also Surra, which is a trypanosomiasis caused by T. evansi, that affects wild and domestic animals mainly in Africa, Asia and South America, causing serious economic losses due to mortality and morbidity [ 6 ]. However, despite being a disease that predominantly affects animals, cases of surra have been reported in humans in the Asian region, where the main symptoms observed were fever and drowsiness, without invasion of the parasite in the central nervous system [ 7 ].…”

Evaluation of surra treatment strategies attacking horses and buffaloes in East Sumba District, Nusa Tenggara Timur Province of Indonesia (2010 – 2016)

“…Trypanosoma evansi (T. evansi) is a haemoprotozoan of the genus Trypanosoma as the causative agent of Surra. The parasite is geographically distributed in the tropical and subtropical areas such as Central and South America, Africa, Middle East and Asia, including Indonesia and attacks multispecies animals characterized by polymorphism of its clinical symptoms (Camoin et al 2017;Aregawi et al 2019). Surra is transmitted mechanically from an infected animal to another susceptible animal by haematophagous flies particularly Tabanus spp, Stomoxys spp, Haematopota spp, Lyperosia spp and Chrysops spp.…”