Invasive Species Compendium

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Trypanosoma evansi

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Datasheet

Trypanosoma evansi

Summary

  • Last modified
  • 03 March 2020
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • Trypanosoma evansi
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Protista
  •     Phylum: Protozoa
  •       Subphylum: Sarcomastigophora
  •         Order: Kinetoplastida
  • Summary of Invasiveness
  • Trypanosoma evansi is a protozoan parasite that is the causative agent of the animal disease surra.  The disease occurs in a wide area from the northern part of Africa through the Middle East to Southeast Asia;...

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  • Draft datasheet under review

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    compend@cabi.org
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Identity

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Preferred Scientific Name

  • Trypanosoma evansi (Steel, 1885) Balbiani, 1888

Other Scientific Names

  • Spirochaeti evansi Steel, 1885
  • Trypanosoma brucei evansi

Summary of Invasiveness

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Trypanosoma evansi is a protozoan parasite that is the causative agent of the animal disease surra.  The disease occurs in a wide area from the northern part of Africa through the Middle East to Southeast Asia; it is thought to have been introduced to the Americas in the 16th century and is now found in much of Latin America except the southernmost parts.  It is not known to occur in North America (except possibly Mexico), Australia, Europe (except for rare introductions into Spain and France), or northern Russia. It affects a very large range of domestic and wild animals; only two cases of human infection have been reported. It has a significant economic and animal health impact on horses, cattle, camels and other livestock in many countries. T. evansi is mechanically transmitted primarily by several species of haematophagous flies (mainly Tabanids and Stomoxes), but in Latin America the vampire bat (Desmodus rotundus) is a vector and reservoir host. Carnivores can become infected by eating infected meat. Clinical manifestations of disease include fever, anaemia, loss of appetite, weight loss, nervous signs, abortion, cachexia, and potentially death.  No vaccine is available.  Several chemotherapeutic drugs are used for the prophylaxis and treatment of surra; however, drug resistance is known to occur. Surra is on the OIE list of multispecies notifiable diseases.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Protista
  •         Phylum: Protozoa
  •             Subphylum: Sarcomastigophora
  •                 Order: Kinetoplastida
  •                     Family: Trypanosomatidae
  •                         Genus: Trypanosoma
  •                             Species: Trypanosoma evansi

Notes on Taxonomy and Nomenclature

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Trypanosomes are protozoan parasites of the blood and tissues of many animal species.  They are taxonomically assigned to the order Kinetoplastida, family Trypanosomatidae, and genus Trypanosoma. The name is derived from the Greek trypano (borer) and soma (body) because of the corkscrew-like motion of some trypanosomatid species.  The genus Trypanosoma is known from fossils in Dominican amber represented by the extinct species T. antiquus (Poinar, 2005).  T. evansi belongs to the T. brucei group within the subgenus Trypanozoon (Desquesnes et al., 2013).  In fact, recent whole genome sequencing and analysis support the idea that T. evansi could be classified as a subspecies of T. brucei (Carnes et al., 2015). Desquesnes et al. (2013) discussed this and concluded that, as the genetic evidence was not unequivocal, and T. evansi shows strong biological, ecological and medical differences from T. brucei, it was advisable to retain the name T. evansi. T. equinum, affecting horses in South America, was previously regarded as a separate species but is now considered to be a dyskinetoplastic variant of T. evansi (Stevens and Brisse, 2004).

Infection with T. evansi causes a disease named ‘surra’ in India, El debab, El gafar, Tabourit or Mbori in North Africa and Mal de Caderas or Murrina in Latin America (OIE, 2012).  The origin of 'surra' is from the Marathi sūra, meaning “the sound of heavy breathing through the nostrils”.  A parasite that would later be named T. evansi was first identified and described as the causative agent of surra by Griffith Evans in 1880 while working in India. A young veterinarian named J.H. Steel, believing that the causative organisms were spirochaetes, named them Spirochaeti evansi.  Several years later, the taxonomic error was corrected, and they were placed in the genus Trypanosoma (Fallis, 1986).

Distribution

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Trypanosoma evansi has the widest geographical distribution among the trypanosomes.  In the Eastern Hemisphere, its geographical distribution is continuous from the northern part of Africa through the Middle East to Southeast Asia.  In Africa, it is present in all countries where camels are present.  It is found in sub-Saharan and Mediterranean climates, as well as in arid deserts and semiarid steppes.  It is present in the Arabian Peninsula, Turkey (although a review by Aregawi et al. (2019) did not find any references to its presence in Turkey), Afghanistan and Pakistan (Desquesnes et al., 2013).  It is also present throughout southern Asia, including India, China, Mongolia, parts of Russia, Bhutan, Nepal, Myanmar, Laos, Vietnam, Cambodia, Thailand, Malaysia, the Philippines, and Indonesia (Luckins, 1988).  Its presence was suspected in Papua New Guinea, but not confirmed, and it is so far absent from Australia (Reid, 2002) (it was briefly introduced there in the early 20th century but was soon eradicated -- Mackerras, 1959).  In Latin America, it is present in much of South America other than the southernmost parts, and it is uncertain how far north through Central America its range extends -- some reports suggest Mexico, but this is not certain (Desquesnes, 2004).  In Europe, there have been recent introductions of T. evansi in the Canary Islands (Spain) (Gutiérrez et al., 1998), the Spanish mainland (Tamarit et al., 2010), and a single epizootic in France resulting from infected camels imported from the Canary Islands (Desquesnes et al., 2008). It is said to have been been occasionally reported from Bulgaria (Desquesnes et al., 2013), although a review by Aregawi et al. (2019) did not find any references supporting that. The parasite is absent from North America, northern Europe, and northern Russia (Desquesnes et al., 2013).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 03 Mar 2020
Continent/Country/Region Distribution Last Reported Origin First Reported Invasive Reference Notes

Africa

AlgeriaPresentHoare (1972)
BotswanaAbsent, No presence record(s)OIE Handistatus (2005)
Burkina FasoPresentHoare (1972)
BurundiAbsent, No presence record(s)OIE Handistatus (2005)
Cabo VerdeAbsent, No presence record(s)OIE Handistatus (2005)
Central African RepublicAbsent, No presence record(s)OIE Handistatus (2005)
ChadPresentHoare (1972)
Congo, Democratic Republic of theAbsent, No presence record(s)OIE Handistatus (2005)
Côte d'IvoireAbsent, No presence record(s)OIE Handistatus (2005)
DjiboutiPresentOIE Handistatus (2005)
EgyptPresentHoare (1972); OIE Handistatus (2005)
EritreaPresentHoare (1972); OIE Handistatus (2005)
EswatiniAbsent, No presence record(s)OIE Handistatus (2005)
EthiopiaPresentHoare (1972); OIE Handistatus (2005)
GhanaAbsent, Unconfirmed presence record(s)Aregawi et al. (2019); OIE Handistatus (2005)Doubtful evidence obtained by non-T. evansi specific PCR
GuineaAbsent, No presence record(s)OIE Handistatus (2005)
KenyaPresentHoare (1972)
LibyaPresentHoare (1972); OIE Handistatus (2005)
MadagascarAbsent, No presence record(s)OIE Handistatus (2005)
MaliPresentHoare (1972)
MauritaniaPresentHoare (1972)
MauritiusPresentAregawi et al. (2019); OIE Handistatus (2005)
MoroccoPresentHoare (1972); OIE Handistatus (2005)
NamibiaAbsent, No presence record(s)OIE Handistatus (2005)
NigerPresentHoare (1972)
NigeriaPresentHoare (1972)
RéunionAbsent, No presence record(s)OIE Handistatus (2005)
São Tomé and PríncipeAbsent, No presence record(s)OIE Handistatus (2005)
SenegalPresentHoare (1972)
SeychellesAbsent, No presence record(s)OIE Handistatus (2005)
SomaliaPresentHoare (1972)
South AfricaAbsent, No presence record(s)OIE Handistatus (2005)
SudanPresentHoare (1972)
TanzaniaAbsent, No presence record(s)OIE Handistatus (2005)
TunisiaPresentHoare (1972); OIE Handistatus (2005)
ZambiaAbsent, Unconfirmed presence record(s)Aregawi et al. (2019); OIE Handistatus (2005)Doubtful evidence obtained by non-T. evansi specific PCR
ZimbabweAbsent, No presence record(s)OIE Handistatus (2005)

Asia

AfghanistanPresentDesquesnes et al. (2013)
BahrainAbsent, No presence record(s)OIE Handistatus (2005)
BangladeshPresentMisra et al. (2016)
BhutanPresentLuckins (1988); OIE Handistatus (2005)
CambodiaPresentLuckins (1988)
ChinaPresentLuckins (1988)
GeorgiaAbsent, No presence record(s)OIE Handistatus (2005)
Hong KongAbsent, No presence record(s)OIE Handistatus (2005)
IndiaPresentHoare (1972)
IndonesiaPresentLuckins (1988); OIE Handistatus (2005)
IranPresentAregawi et al. (2019)
IraqPresentDesquesnes et al. (2013); OIE Handistatus (2005)
IsraelPresentDesquesnes et al. (2013); OIE Handistatus (2005)
JapanAbsent, No presence record(s)OIE Handistatus (2005)
JordanPresentDesquesnes et al. (2013); OIE Handistatus (2005)
KazakhstanPresentDesquesnes et al. (2013); OIE Handistatus (2005)
KuwaitPresentAregawi et al. (2019); OIE Handistatus (2005)
LaosPresentLuckins (1988)
LebanonPresentDesquesnes et al. (2013); OIE Handistatus (2005)
MalaysiaPresentLuckins (1988)
MongoliaPresentLuckins (1988); OIE Handistatus (2005)
MyanmarPresentLuckins (1988); OIE Handistatus (2005)
NepalPresentLuckins (1988)
North KoreaAbsent, No presence record(s)OIE Handistatus (2005)
OmanPresentDesquesnes et al. (2013); OIE Handistatus (2005)
PakistanPresentDesquesnes et al. (2013)
PalestinePresentAregawi et al. (2019)
PhilippinesPresentLuckins (1988); OIE Handistatus (2005)
QatarAbsent, No presence record(s)OIE Handistatus (2005)
Saudi ArabiaPresentDesquesnes et al. (2013); OIE Handistatus (2005)
SingaporeAbsent, No presence record(s)OIE Handistatus (2005)
South KoreaAbsent, No presence record(s)OIE Handistatus (2005)
Sri LankaPresentAregawi et al. (2019)
SyriaPresentDesquesnes et al. (2013); OIE Handistatus (2005)
TaiwanAbsent, No presence record(s)OIE Handistatus (2005)
ThailandPresentLuckins (1988)
TurkeyAbsent, Unconfirmed presence record(s)Desquesnes et al. (2013); Aregawi et al. (2019)
TurkmenistanAbsent, No presence record(s)OIE Handistatus (2005)
United Arab EmiratesPresentDesquesnes et al. (2013)
UzbekistanAbsent, No presence record(s)OIE Handistatus (2005)
VietnamPresentLuckins (1988); OIE Handistatus (2005)

Europe

AndorraAbsent, No presence record(s)OIE Handistatus (2005)
AustriaAbsent, No presence record(s)OIE Handistatus (2005)
BelarusAbsent, No presence record(s)OIE Handistatus (2005)
Bosnia and HerzegovinaAbsent, No presence record(s)OIE Handistatus (2005)
BulgariaAbsent, Unconfirmed presence record(s)OIE Handistatus (2005); Desquesnes et al. (2013); Aregawi et al. (2019)
CroatiaAbsent, No presence record(s)OIE Handistatus (2005)
CyprusAbsent, No presence record(s)OIE Handistatus (2005)
CzechiaAbsent, No presence record(s)OIE Handistatus (2005)
DenmarkAbsent, No presence record(s)OIE Handistatus (2005)
EstoniaAbsent, No presence record(s)OIE Handistatus (2005)
FinlandAbsent, No presence record(s)OIE Handistatus (2005)
FrancePresent, Few occurrencesIntroduced2006Desquesnes et al. (2008); OIE Handistatus (2005)
GermanyPresentAregawi et al. (2019); OIE Handistatus (2005)
GreeceAbsent, No presence record(s)OIE Handistatus (2005)
HungaryAbsent, No presence record(s)OIE Handistatus (2005)
IcelandAbsent, No presence record(s)OIE Handistatus (2005)
IrelandAbsent, No presence record(s)OIE Handistatus (2005)
Isle of ManAbsent, No presence record(s)OIE Handistatus (2005)
JerseyAbsent, No presence record(s)OIE Handistatus (2005)
LatviaAbsent, No presence record(s)OIE Handistatus (2005)
LiechtensteinAbsent, No presence record(s)OIE Handistatus (2005)
LithuaniaAbsent, No presence record(s)OIE Handistatus (2005)
LuxembourgAbsent, No presence record(s)OIE Handistatus (2005)
MaltaAbsent, No presence record(s)OIE Handistatus (2005)
MoldovaAbsent, No presence record(s)OIE Handistatus (2005)
NetherlandsPresentAregawi et al. (2019); OIE Handistatus (2005)
North MacedoniaAbsent, No presence record(s)OIE Handistatus (2005)
NorwayAbsent, No presence record(s)OIE Handistatus (2005)
PolandAbsent, No presence record(s)OIE Handistatus (2005)
PortugalAbsent, No presence record(s)OIE Handistatus (2005)
RomaniaAbsent, No presence record(s)OIE Handistatus (2005)
RussiaPresentCABI (Undated); OIE Handistatus (2005)Present based on regional distribution
-Southern RussiaPresentDesquesnes et al. (2013)
-Western SiberiaPresentDesquesnes et al. (2013)
Serbia and MontenegroAbsent, No presence record(s)OIE Handistatus (2005)
SlovakiaAbsent, No presence record(s)OIE Handistatus (2005)
SloveniaAbsent, No presence record(s)OIE Handistatus (2005)
SpainPresent, Few occurrencesIntroducedTamarit et al. (2010); OIE Handistatus (2005)
-Canary IslandsPresentIntroduced1995Gutiérrez et al. (1998)
SwedenAbsent, No presence record(s)OIE Handistatus (2005)
SwitzerlandAbsent, No presence record(s)OIE Handistatus (2005)
UkraineAbsent, No presence record(s)OIE Handistatus (2005)
United Kingdom
-Northern IrelandAbsent, No presence record(s)OIE Handistatus (2005)

North America

BarbadosAbsent, No presence record(s)OIE Handistatus (2005)
BelizeAbsent, No presence record(s)OIE Handistatus (2005)
BermudaAbsent, No presence record(s)OIE Handistatus (2005)
British Virgin IslandsAbsent, No presence record(s)OIE Handistatus (2005)
CanadaAbsent, No presence record(s)OIE Handistatus (2005)
Cayman IslandsAbsent, No presence record(s)OIE Handistatus (2005)
Costa RicaAbsent, Unconfirmed presence record(s)Desquesnes (2004); OIE Handistatus (2005)
CubaAbsent, No presence record(s)OIE Handistatus (2005)
CuraçaoAbsent, No presence record(s)OIE Handistatus (2005)
DominicaAbsent, No presence record(s)OIE Handistatus (2005)
Dominican RepublicAbsent, No presence record(s)OIE Handistatus (2005)
El SalvadorAbsent, No presence record(s)OIE Handistatus (2005)
GuadeloupeAbsent, No presence record(s)OIE Handistatus (2005)
GuatemalaAbsent, Unconfirmed presence record(s)Desquesnes (2004); OIE Handistatus (2005)
HaitiAbsent, No presence record(s)OIE Handistatus (2005)
HondurasAbsent, Unconfirmed presence record(s)Desquesnes (2004); OIE Handistatus (2005)
MartiniqueAbsent, No presence record(s)OIE Handistatus (2005)
MexicoAbsent, Unconfirmed presence record(s)Desquesnes (2004); OIE Handistatus (2005)
NicaraguaAbsent, Unconfirmed presence record(s)Desquesnes (2004); OIE Handistatus (2005)
PanamaPresentIntroducedDesquesnes (2004)
Saint Kitts and NevisAbsent, No presence record(s)OIE Handistatus (2005)
Saint Vincent and the GrenadinesAbsent, No presence record(s)OIE Handistatus (2005)
Trinidad and TobagoAbsent, No presence record(s)OIE Handistatus (2005)
United StatesAbsent, No presence record(s)OIE Handistatus (2005)

Oceania

AustraliaAbsent, No presence record(s)OIE Handistatus (2005)
French PolynesiaAbsent, No presence record(s)OIE Handistatus (2005)
New CaledoniaAbsent, No presence record(s)OIE Handistatus (2005)
New ZealandAbsent, No presence record(s)OIE Handistatus (2005)
SamoaAbsent, No presence record(s)OIE Handistatus (2005)
VanuatuAbsent, No presence record(s)OIE Handistatus (2005)

South America

ArgentinaPresentIntroducedDesquesnes et al. (2013)
BoliviaPresentIntroducedDesquesnes (2004); OIE Handistatus (2005)
BrazilPresentIntroducedInvasiveDesquesnes (2004)As of 2004, spreading in Brazil with considerable clinical and economic consequences in newly infected regions
ChilePresent, LocalizedIntroducedDesquesnes (2004); OIE Handistatus (2005)
ColombiaPresent, WidespreadIntroducedDesquesnes (2004)
EcuadorAbsent, Unconfirmed presence record(s)Desquesnes (2004); OIE Handistatus (2005)
Falkland IslandsAbsent, No presence record(s)OIE Handistatus (2005)
French GuianaPresent, Few occurrencesIntroducedDesquesnes (2004); OIE Handistatus (2005)One case in a dog suggests presence in wild animals
GuyanaAbsent, Formerly present1970Desquesnes (2004); OIE Handistatus (2005); Aregawi et al. (2019)
ParaguayPresentIntroducedDesquesnes (2004)
PeruPresentIntroducedDesquesnes (2004); OIE Handistatus (2005)
SurinamePresent, Few occurrencesIntroducedDesquesnes (2004)A few reports in dogs; some PCR evidence of presence in cattle
UruguayAbsent, No presence record(s)OIE Handistatus (2005)
VenezuelaPresentIntroducedDesquesnes (2004); OIE Handistatus (2005)Enzootic throughout plains

History of Introduction and Spread

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Trypanosoma evansi was first described in 1880 from India.  However, it is thought to be derived from the African T. brucei brucei, which is restricted to the tsetse fly belt of Africa.  T. evansi is no longer able to undergo its cycle in the tsetse fly (Glossina sp.) due to the loss of the maxicircles of mitochondrial DNA; however, it is not known when this phenomenon occurred.  Historical data suggests that surra was already present in India at least several centuries B.C. (Desquesnes et al., 2013).  Apparently the parasite ultimately spread eastward from India, but the date of this initial spread is unknown.  The westward extension of T. evansi is more recent, however.  It is thought to have been introduced into Latin America in the 16th century with the Arabian horses belonging to the Spanish conquistadores (Hoare, 1965).  It was described for the first time on the Island of Marajo at the mouth of the Amazon River in Brazil in 1827; and was further observed in Paraguay in 1847; in the Pantanal, Brazil in 1850; and Mato Grosso, Brazil in 1860, before further spreading into Bolivia, Venezuela, Guyana, and Colombia (Hoare, 1972). 

In Europe, there have been recent introductions of T. evansi in the Canary Islands (Spain) (Gutiérrez et al., 1998) and the Spanish mainland (Tamarit et al., 2010), and a single epizootic in France in 2006 resulting from infected camels imported from the Canary Islands (Desquesnes et al., 2008).

Risk of Introduction

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Due to its wide host range, Trypanosoma evansi has the potential to invade new geographical areas, as shown by the recent incursions in continental Spain and France. Europe, North America and Australia might potentially be at risk (Desquesnes et al., 2013).

Pathogen Characteristics

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Trypanosoma evansi is classified within the genus Trypanosoma, subgenus Trypanozoon, along with T. brucei brucei (cause of nagana in livestock), T. brucei rhodesiense and T. brucei gambiense (cause of human African sleeping sickness), and T. equiperdum (cause of a sexually transmitted disease in horses).  When observed microscopically in fresh blood samples, T. evansi appears small with thin anterior and posterior extremities and a free flagellum at the anterior end.  There is also a highly visible undulating membrane.  When observed on a Giemsa stained thin smear, T. evansi is described as a monomorphic thin trypomastigote parasite (Desquesnes et al., 2013).  By comparison with T. brucei, it shows mostly slender forms with a long free flagellum and thin posterior extremity with subterminal small kinetoplast, but some intermediate (shorter free flagellum and posterior extremity) and rare “stumpy” forms have been reported. 

The mean length of the parasite is 24 ± 4 µm, which does not vary sustainably with geographical, host, or strain origin, but can change in relation to the growing conditions of the parasite and the immune response of the host (Tejero et al., 2008).  Like all pathogenic trypanosomes, T. evansi is covered by a dense protein layer consisting of a single protein called the variant surface glycoprotein (VSG) (Richards, 1984).

Two key, and related, biological features distinguish T. evansi from the T. brucei group.  First, its transmission is independent from the tsetse fly as an obligatory vector.  Second, all strains of T. evansi investigated so far are akinetoplastic or dyskinetoplastic, that is lacking all or critical parts, respectively, of the mitochondrial or kinetoplast DNA (kDNA).  T. brucei has a complex life cycle involving a vertebrate bloodstream stage and a procyclic stage in the tsetse fly.  In T. evansi a total or partial loss of kDNA has “locked” the trypanosome in the bloodstream form resulting in the elimination of the need for the tsetse fly vector. This has resulted in its ability to leave the African tsetse fly belt and spread to other continents (Lai et al., 2008; Lun and Desser, 1995), allowing T. evansi, along with T. equiperdum, to become one of the pathogenic trypanosomes with the widest geographical distribution.

Surra, the disease associated with this pathogen, is on the list of diseases notifiable to the World Organisation for Animal Health (OIE). Animal Health and Production Compendium users can refer to the AHPC library for further information from OIE, including the International Animal Health Code and the Manual of Standards for Diagnostic Tests and Vaccines. Also see the website: www.oie.int.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Military movementsProbably introduced to the Americas with the horses of the Spanish conquistadores Yes Hoare, 1965

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Host and vector organismsMechanically transmitted by haematophagous flies; in Latin America the vampire bat is mainly responsible for dissemination Yes Desquesnes et al., 2013

Vectors and Intermediate Hosts

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VectorSourceReferenceGroupDistribution
AtylotusInsect
ChrysopsInsect
Desmodus rotundusOtherSouth America|Central America|South America
HaematobiaInsect
HaematopotaInsect
StomoxysInsect
Stomoxys calcitransInsect
TabanidaeInsect
TabanusInsect

Economic Impact

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Several economically important animals, including camels, horses, buffaloes, and cattle, are particularly affected by surra (OIE, 2012).  Camels, for example, are a major part of the economies of many African and Middle East countries, being used for nomadic pastoralism, transportation, racing, and production of milk, wool and meat.  According to the United Nations Food and Agriculture Organization, the total world camel population is approximately 23 million animals (FAO, 2016), and surra is considered the most important single cause of morbidity and mortality in camels (OIE, 2013).  In addition to camels, Trypanosoma evansi and other livestock trypanosomes threaten 48 million cattle in 37 African countries and are responsible for major losses in the production of milk, meat, and manure fertilizer (Desquesnes et al., 2013).  In addition to Africa, T. evansi (and other animal trypanosomes) place a permanent constraint on raising livestock throughout much of Asia and Latin America.

Environmental Impact

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While Trypanosoma evansi infects a wide range of domestic and wild animals, clinical disease (surra) mainly affects domestic livestock, but there has been an outbreak in an Indian zoo in which several tigers died (P. Büscher, Institute of Tropical Medicine, Antwerp, Belgium, personal communication, 2019).  Infected wildlife can become reservoir hosts (i.e. asymptomatic carriers). There is no evidence that T. evansi has a large impact on biodiversity and the environment, but it is not certain that its impact is negligible.

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
Impact outcomes
  • Host damage
  • Negatively impacts agriculture
  • Negatively impacts animal health
  • Negatively impacts livelihoods
Impact mechanisms
  • Pathogenic
Likelihood of entry/control
  • Difficult to identify/detect in the field
  • Difficult/costly to control

Gaps in Knowledge/Research Needs

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An important area for future research is the development of new anti-trypanosome therapeutics, and drug resistance. There are only a limited number of drugs available for the treatment of trypanosomiasis, and an even more limited number suitable for treatment of Trypanosoma evansi infection in camels due to the toxicity of some of the available drugs in camels. None of the existing drugs are able to cure the neurological stage of T. evansi infection, so animals may clinically recover for a while after treatment but relapse later (P. Büscher, Institute of Tropical Medicine, Antwerp, Belgium, personal communication, 2019; Büscher et al., 2019). In addition, these drugs have been in use over many decades, including use as prophylaxis, which can lead to increased drug resistance. In most endemic countries, suitable drugs are not registered and not available, and in some, counterfeit drugs are a significant problem (P. Büscher, Institute of Tropical Medicine, Antwerp, Belgium, personal communication, 2019).

Better diagnostic techniques are also needed, as existing ones lack sensitivity or specificity; even existing techniques are often unaffordable in endemic countries (P. Büscher, Institute of Tropical Medicine, Antwerp, Belgium, personal communication, 2019; Büscher et al., 2019).

An effective vaccine against surra is sorely needed to control this disease.  This has not been possible to date due to the rapid turnover of the parasite’s outer surface glycoprotein (VSG), which also occurs in other animal and human pathogenic trypanosomes.  More research is needed to develop ways to stop or control this antigenic variation and/or develop new vaccine targets.

References

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Aregawi, W. G., Agga, G. E., Abdi, R. D., Büscher, P., 2019. Systematic review and meta-analysis on the global distribution, host range, and prevalence of Trypanosoma evansi. Parasites and Vectors, 12(67), (31 January 2019). https://link.springer.com/article/10.1186/s13071-019-3311-4 doi: 10.1186/s13071-019-3311-4

Büscher, P., Gonzatti, M. I., Hébert, L., Inoue, N., Pascucci, I., Schnaufer, A., Suganuma, K., Touratier, L., Reet, N. van, 2019. Equine trypanosomosis: enigmas and diagnostic challenges. Parasites and Vectors, 12(234), (15 May 2019). https://link.springer.com/article/10.1186/s13071-019-3484-x

Carnes, J., Anupama, A., Balmer, O., Jackson, A., Lewis, M., Brown, R., Cestari, I., Desquesnes, M., Gendrin, C., Hertz-Fowler, C., Imamura, H., Ivens, A., Korený, L., Lai DeHua, MacLeod, A., McDermott, S. M., Merritt, C., Monnerat, S., Moon, W. J., Myler, P., Phan, I., Ramasamy, G., Sivam, D., Lun ZhaoRong, Lukeš, J., Stuart, K. (et al), 2015. Genome and phylogenetic analyses of Trypanosoma evansi reveal extensive similarity to T. brucei and multiple independent origins for dyskinetoplasty. PLoS Neglected Tropical Diseases, 9(1), e3404. http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0003404 doi: 10.1371/journal.pntd.0003404

Cross, G. A. M., 1975. Identification, purification and properties of clone-specific glycoprotein antigens constituting the surface coat of Trypanosoma brucei. Parasitology, 71(Pt 3), 393-417. doi: 10.1017/S003118200004717X

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Distribution References

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Desquesnes M, 2004. Livestock trypanosomoses and their vectors in Latin America. [ed. by Desquesnes M]. Paris, France: OIE (World Organisation for Animal Health). ix + 174 pp.

Desquesnes M, Bossard G, Patrel D, Herder S, Patout O, Lepetitcolin E, Thevenon S, Berthier D, Pavlovic D, Brugidou R, Jacquiet P, Schelcher F, Faye B, Touratier L, Cuny G, 2008. First outbreak of Trypanosoma evansi in camels in metropolitan France. Veterinary Record. 162 (23), 750-752. http://veterinaryrecord.bvapublications.com/archive/

Desquesnes M, Holzmuller P, Lai DeHua, Dargantes A, Lun ZhaoRong, Jittaplapong S, 2013. Trypanosoma evansi and surra: a review and perspectives on origin, history, distribution, taxonomy, morphology, hosts, and pathogenic effects. BioMed Research International. Article ID 194176. http://www.hindawi.com/journals/bmri/2013/194176/

Gutiérrez C, Montoya J A, Padron M, Corbera J A, Juste M C, Molina J M, 1998. Description of a case of trypanosomiasis due to Trypanosoma evansi in a dromedary in the Canary Islands. (Descripción de un caso de tripanosomosis en el dromedario por T. evansi en Canarias.). Medicina Veterinaria. 15 (6), 356-357.

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Luckins A G, 1988. Trypanosoma evansi in Asia. Parasitology Today. 4 (5), 137-142.

Misra K K, Roy S, Choudhury A, 2016. Biology of Trypanosoma (Trypanozoon) evansi in experimental heterologous mammalian hosts. Journal of Parasitic Diseases. 40 (3), 1047-1061. http://link.springer.com/article/10.1007/s12639-014-0633-1 DOI:10.1007/s12639-014-0633-1

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Tamarit A, Gutierrez C, Arroyo R, Jimenez V, Zagalá G, Bosch I, Sirvent J, Alberola J, Alonso I, Caballero C, 2010. Trypanosoma evansi infection in mainland Spain. Veterinary Parasitology. 167 (1), 74-76. http://www.sciencedirect.com/science/journal/03044017 DOI:10.1016/j.vetpar.2009.09.050

Links to Websites

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WebsiteURLComment
OIE Reference Laboratories http://www.oie.int/en/our-scientific-expertise/reference-laboratories/list-of-laboratories
World Organization for Animal Health (OIE) http://www.oie.int

Organizations

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Japan: National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, , Inada-cho Nishi 2-13 Obihiro, Hokkaido 080-8555 , http://www.obihiro.ac.jp/~protozoa/eng/index-eng.html

France: World Organization for Animal Health (OIE), Paris, http://www.oie.int

Italy: Food and Agriculture Organization of the United Nations (FAO), Rome, http://www.fao.org

Principal Source

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Draft datasheet under review

Contributors

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20/01/2016 Original text by:

Chris Whitehouse, US Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702-5011, USA.

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