Trypanosoma evansi
Alireza Sazmand ,1,2,
* Marc Desquesnes ,3,4,5
and Domenico Otranto 1,6
1
Department of Pathobiology, Faculty of Veterinary Science, Bu-Ali Sina University, 6517658978, Hamedan, Iran
2
Zoonotic Diseases Research Center, Department of Food Hygiene and Safety, School of Public Health, Shahid Sadoughi University of Medical Sciences, 8915173160 Yazd, Iran
3
CIRAD, UMR InterTryp, F-34398 Montpellier, France
4
InterTryp, Univ Montpellier, CIRAD, IRD, Montpellier, France
5
ENVT, 23 Chemin des Capelles, 31076 Toulouse, France
6
Department of Veterinary Medicine, University of Bari, Valenzano, 70010, Bari, Italy
Trypanosoma evansi
Other minor transmission routes
VerƟcally (transplacental, colostrum, milk)Orally to carnivorous animals
Very rare cases of human infecƟon
Iatrogenically, butchering …
Morphology
- Length: 25–35 μm
- Free flagellum
- Large undulaƟng membrane
- Central nucleus
- Small and subterminal kinetoplast
- Thin posterior extremity
Biology
- TrypomasƟgotes mulƟply by binary
fission in body fluids (e.g., blood, lymph,
and spinal fluid)
- No epimasƟgote or amasƟgote forms
- No intermediate host
MovementdirecƟon
Anterior
Posterior
Parasites are mainly transmiƩed mechanically by biƟng flies
TrendsTrendsininParasitologyParasitology
Trypanosoma evansi, the causative agent of 'surra', is a flagellated hemoprotozoan parasite. It kills thousands of
animals every year and causes significant animal morbidity and loss of productivity. T. evansi originated from
Trypanosoma brucei through deletion of the maxicircle kinetoplast DNA which conferred the capacity for mechanical
transmission by flies and allowed T. evansi to expand beyond the tsetse belt. Presently, it is the most widely
distributed pathogenic trypanosome in Africa, Asia, and Latin America, but its potential for geographical extension
is not limited, as shown by recent sporadic cases in Spain and France. The most susceptible animals are horses,
dogs, camels, and buffaloes, but other domestic livestock and wild mammals (including Australian marsupials,
experimentally) can also be infected. Test-and-treatment of infected hosts and mass treatment programs are
recommended in high-prevalence settings. International trading of potential carriers is a risk.
Eastern Asia
Africa,
Western AsiaSouth America
Endemic countries and regions
Countries and regions with sporadic cases
DistribuƟon and host types of Trypanosoma evansi
TrendsTrendsininParasitologyParasitology
KEY FACTS:
T. evansi can affect all mammals and has
a wide range of domestic and wild
reservoirs.
Diagnosis is made by detection of
parasites in blood. This method has
low sensitivity when the parasites are
few in number (e.g., in reservoirs and
wild mammals) or absent in blood
while present in the nervous system;
surveillance is consequently
challenging.
No vaccine is available because of the
rapid changes in trypanosomal surface
glycoproteins, supporting avoidance of
immune responses.
Very rare human cases have been
described from India, Vietnam, Sri
Lanka, and Egypt. Clinical presentation
among humans is quite similar to the first
stage of the chronic form of human
sleeping sickness caused by T. brucei.
DISEASE FACTS:
Surra is a trypanosomal disease that
affects multiple mammalian taxa, with
variable clinical presentation, severity,
and outcome.
Clinical presentation may include fever,
anemia, edema, loss of weight and
condition, overt emaciation, sometimes
paralysis, and death.
Surra can occur as acute, subacute, or
chronic disease, or it may be
asymptomatic.
Treatment with melarsomine and
quinapyramine is efficacious if applied
early. Otherwise, surra is invariably fatal
in highly susceptible individuals.
Better knowledge of distribution and
treatment is needed.
*Correspondence:
alireza.sazmand@basu.ac.ir (A. Sazmand).
Trends in Parasitology, June 2022, Vol. 38, No. 6 © 2022 Elsevier Ltd. All rights reserved. https://doi.org/10.1016/j.pt.2021.12.010 489
Trends in Parasitology | Parasite of the Month
Acknowledgments
We thank Dr Dennis Lawler for proofreading the manuscript, and Dr Jairo Alfonso Mendoza-Roldan for assistance in the design of the
first figure.
Declaration of interests
The authors declare no competing interests.
Resources
www.oie.int/fileadmin/home/eng/health_standards/tahm/3.01.21_trypano_surra.pdf
https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2017.4892
Literature
1. Desquesnes, M. et al. (2013) Trypanosoma evansi and surra: a review and perspectives on transmission, epidemiology
and control, impact, and zoonotic aspects. Biomed. Res. Int. 2013, 321237
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morphology, hosts, and pathogenic effects. Biomed. Res. Int. 2013, 194176
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Trypanosoma evansi. Parasit. Vectors 12, 67
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zoonotic parasite Trypanosoma evansi in Southeast Asia. Clin. Infect. Dis. 62, 1002–1008
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in central desert of Iran. Yale J. Biol. Med. 94, 249–258
8. Gutierrez, C. et al. (2010) Trypanosoma evansi: recent outbreaks in Europe. Vet. Parasitol. 174, 26–29
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TAXONOMY AND CLASSIFICATION:
PHYLUM: Euglenozoa
CLASS: Kinetoplastea
ORDER: Trypanosomatida
FAMILY: Trypanosomatidae
GENUS: Trypanosoma
SPECIES: T. evansi
Trends in Parasitology | Parasite of the Month
490 Trends in Parasitology, June 2022, Vol. 38, No. 6 © 2022 Elsevier Ltd. All rights reserved. https://doi.org/10.1016/j.pt.2021.12.010