Development of a control strategy towards elimination of Trypanosoma evansi infection (surra) in camels in Africa.

With an increasing worldwide population that presently exceeds 38 million, camels are important source of meat, milk, and transportation of goods, in many regions of the world. Camels are particularly critical in the northern parts of Africa, above the tsetse belt. However, camel breeding areas are expanding into southern areas, under the pressures of global warming, leading to increasing risk of acquiring parasitic infections in these non-traditional ecotypes. Common biting flies (tabanids, stomoxyine flies, and Hippobosca camelina) act as mechanical vectors, resulting in exposure to trypanosomosis (Trypanosoma evansi; Surra) and high camel morbidity and mortality. In these regions, complicating infections with other Trypanosoma may also occur, particularly Trypanosoma vivax. In many modern camel-breeding areas, human populations are living under political upheaval (terrorism, riots), poverty, and precarity (drought, climate modification). Hence, control and/or elimination of Surra in camels would be beneficial to the economies of these populations. Due to the relatively straightforward epidemiology (single parasite with seasonal transmission in a single host species), control of Surra in Africa is affordable and should be based on implementing: (1) national veterinary services capabilities; (2) efficient diagnosis and control methods; (3) joint integrated control of Surra, gastrointestinal helminthoses (mainly haemonchosis), and sarcoptic mange. We propose that methods to control two economically-critical disease problems, gastrointestinal parasitosis and sarcoptic mange, will support improved Surra control in camels. Aided by decision-makers and donors, elimination of Surra could improve camel health and productivity, and stabilize camel-rearing in regions of the world that suffer from political instability and global warming pressures.

Equine trypanosomosis: enigmas and diagnostic challenges.

Equine trypanosomosis is a complex of infectious diseases called dourine, nagana and surra. It is caused by several species of the genus Trypanosoma that are transmitted cyclically by tsetse flies, mechanically by other haematophagous flies, or sexually. Trypanosoma congolense (subgenus Nannomonas) and T. vivax (subgenus Dutonella) are genetically and morphologically distinct from T. brucei, T. equiperdum and T. evansi (subgenus Trypanozoon). It remains controversial whether the three latter taxa should be considered distinct species. Recent outbreaks of surra and dourine in Europe illustrate the risk and consequences of importation of equine trypanosomosis with infected animals into non-endemic countries. Knowledge on the epidemiological situation is fragmentary since many endemic countries do not report the diseases to the World Organisation for Animal Health, OIE. Other major obstacles to the control of equine trypanosomosis are the lack of vaccines, the inability of drugs to cure the neurological stage of the disease, the inconsistent case definition and the limitations of current diagnostics. Especially in view of the ever-increasing movement of horses around the globe, there is not only the obvious need for reliable curative and prophylactic drugs but also for accurate diagnostic tests and algorithms. Unfortunately, clinical signs are not pathognomonic, parasitological tests are not sufficiently sensitive, serological tests miss sensitivity or specificity, and molecular tests cannot distinguish the taxa within the Trypanozoon subgenus. To address the limitations of the current diagnostics for equine trypanosomosis, we recommend studies into improved molecular and serological tests with the highest possible sensitivity and specificity. We realise that this is an ambitious goal, but it is dictated by needs at the point of care. However, depending on available treatment options, it may not always be necessary to identify which trypanosome taxon is responsible for a given infection.

Atypical human infections by animal trypanosomes.

The two classical forms of human trypanosomoses are sleeping sickness due to Trypanosoma brucei gambiense or T. brucei rhodesiense, and Chagas disease due to T. cruzi. However, a number of atypical human infections caused by other T. species (or sub-species) have been reported, namely due to T. brucei brucei, T. vivax, T. congolense, T. evansi, T. lewisi, and T. lewisi-like. These cases are reviewed here. Some infections were transient in nature, while others required treatments that were successful in most cases, although two cases were fatal. A recent case of infection due to T. evansi was related to a lack of apolipoprotein L-I, but T. lewisi infections were not related to immunosuppression or specific human genetic profiles. Out of 19 patients, eight were confirmed between 1974 and 2010, thanks to improved molecular techniques. However, the number of cases of atypical human trypanosomoses might be underestimated. Thus, improvement, evaluation of new diagnostic tests, and field investigations are required for detection and confirmation of these atypical cases.

Trypanosoma evansi: recent outbreaks in Europe.

Here, two recent outbreaks of Trypanosoma evansi infection in mainland France and Spain associated with the importation of dromedary camels from the Canary Islands, are reported. The disease is well-known on the Archipelago since 1997 and many efforts have been made towards control and eventual eradication, but some areas still remain affected. Both mainland outbreaks were controlled by means of massive treatments and monthly serological, parasitological and molecular (PCR) evaluations carried out by Valencian Regional Animal Health laboratory and by CIRAD, Montpellier, respectively. Possible causes for the persistence of the parasite in a small area of the Canaries are discussed. T. evansi must be included among the animal health conditions for international trade within the European Union as well as many other countries. Moreover, procedures including diagnosis, curative or preventive treatment and quarantine should be established to insure the status of the animals moving from a country to another.

Presence of Trypanosoma theileri in Spanish Cattle.

Trypanosoma theileri (Laveran, 1902) has been diagnosed in many countries and is commonly considered as a nonpathogenic hemoparasite, although some authors have described clinical signs in cattle infected with T. theileri. In April and May, 2005, 12 blood samples were received at the Exopol Diagnostic Laboratory (Zaragoza, Spain) from a Spanish bull-fighting farm located at Seville province. Clinical exploration of the animals revealed fever, progressive weight loss, anemia, and frequent recumbent position. Microscopic examination showed Theileria spp. in all cases (12), and in four of them, T. theileri was also observed. The clinical picture observed in the animals could be compatible with T. theileria infection. However, the contribution of T. theileri to the clinical signs seen at least in four cases is unknown. Further studies are necessary to determine the pathogenicity of T. theileri in the different animal species. To our knowledge, this is the first isolation of T. theileri in Spain.

Trypanosoma equiperdum: master of disguise or historical mistake?

After 100 years of research, only a small number of laboratory strains of Trypanosoma equiperdum exists, and the history of most of the strains is unknown. No definitive diagnosis of dourine can be made at the serological or molecular level. Only clinical signs are pathognomonic and international screening relies on an outdated cross-reactive serological test (the complement-fixation test) from 1915, resulting in serious consequences at the practical level. Despite many characterization attempts, no clear picture has emerged of the position of T. equiperdum within the Trypanozoon group. In this article, we highlight the controversies that exist regarding T. equiperdum, and the overlap that occurs with Trypanosoma evansi and Trypanosoma brucei brucei. By revisiting the published data, from the early decades of discovery to the recent serological- and molecular-characterization studies, a new hypothesis arises in which T. equiperdum no longer exists as a separate species and in which current strains can be divided into T. evansi (the historical mistake) and Trypanosoma brucei equiperdum (the master of disguise). Hence, dourine is a disease caused by specific host immune responses to a T. b. equiperdum or T. evansi infection.