Trypanosoma evansi: Recent outbreaks in Europe
Introduction
Trypanosoma evansi is the most widely distributed of the pathogenic African trypanosomes of animals, affecting domestic livestock and wildlife in Asia, Africa and Latin America (Luckins and Dwinger, 2004). T. evansi originated in Africa and spread to South America and Asia with the exportation of animal hosts from Africa, including camels, horses and mules (Hoare, 1972). The parasite causes a disease known as surra, and is mechanically transmitted by biting flies. The vampire bat is a vector in South America. It affects a number of domestic animals and the principal host species varies according to geographical location. Buffalo, cattle, camels and horses are particularly susceptible, although other animals, including wildlife, can also be infected (OIE, 2008).
Dromedary camels (Camelus dromedarius) were introduced into the Canary Islands six centuries ago from the near West African coast for labor, but are currently raised for tourism. With an approximate census of 2000 camels, the Canary Islands harbour the most important camel population in Europe. Since exportation of camels out of Africa is very difficult due to health regulations, many camels imported to European and South America during the last decade came from the Canary Islands. However, T. evansi has been known to be present in the Canary Islands since 1997, when the first case was diagnosed in a dromedary camel imported from Mauritania (Gutierrez et al., 2000). Despite this published evidence, T. evansi has not been included in the animal health conditions for international trade within the European Union and other countries. This failure to recognize T. evansi as endemic within the European Union has caused two recent outbreaks of T. evansi infection, one in metropolitan France in 2006 (Desquesnes et al., 2008) and another in continental Spain in 2008 (Tamarit et al., 2010). Both outbreaks were associated with the import of camels from the Canary Islands without prior checking for potential T. evansi infection. In this article we summarize these recent surra outbreaks observed on mainland Europe.
Section snippets
Trypanosoma evansi in the Canary Islands
T. evansi was diagnosed for the first time in the Canary Islands in 1997 in a dromedary camel presenting the chronic stage of the disease (Gutierrez et al., 2000). Afterwards, in collaboration with the Institute of Tropical Medicine (Antwerp, Belgium), 745 camels were examined by serological (card agglutination test (CATT/T. evansi)) and parasitological methods (micro-hematocrit centrifugation technique and mouse inoculation) (Verloo et al., 1998, Woo, 1969). Thirty-six camels were CATT/T.
Trypanosoma evansi in mainland Spain
T. evansi was observed in mainland Spain in February 2008 in a dromedary camel that presented clinical symptoms including progressive weight loss, severe anemia and weakness (Tamarit et al., 2010). The animal belonged to an equine and camel farm located in Alicante province and had been imported from Gran Canaria about 6 months earlier. Trypomastigote forms were observed in stained blood smears and were identified morphologically as T. evansi. The animal was treated with Cymelarsan® (0.25 mg/kg
Trypanosoma evansi in mainland France
T. evansi was detected for the first time in metropolitan France in 2006 on a sheep and camel farm in the Aveyron Department (Desquesnes et al., 2008). Eight camels were already present on the farm before the outbreak, some of which had been imported from Gran Canaria in 1995 and which did not present any health problem. In June 2006, 5 more camels were imported from Gran Canaria. Three-and-a-half months later, one of them developed weakness, weight loss and anemia leading to death. Post-mortem
Features of the Trypanosoma evansi Canarian strain
Many camels have been imported or have travelled from the Canaries to the European mainland (zoos, circuses, etc.) without any previous examination to detect T. evansi infection. Based on the Canarian Animal Health Department's information, approximately 220 dromedaries have been exported to European countries during the last 10 years. Thus, it is important to be aware of the features of the Canarian strain of T. evansi in order to detect the appearance of the disease as soon as possible.
The
Discussion
The occasional introduction of T. evansi into countries free of the parasite has most often resulted in the parasite becoming endemic (Hoare, 1972). The introduction of T. evansi into the Canary Islands, and later onto mainland Europe, is clearly the result of lack of control measures. These should now be adopted urgently by the different European countries in order to face the current situation. The Agriculture and Livestock Council, Regional Government of the Canary Islands, has implemented
Conflict interest statement
The authors declare that they have no conflict of interest with the contents of this paper in any respect.
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