Narender Singh*, K.M.L. Pathak, Rajender Kumar** and M.B. Chhabra***
Department of Veterinary Parasitology, College of Veterinary and Animal Science, Bikaner- 334001 (Rajasthan)
*Officer Commanding, 15 MFVH, C/O 99 APO, India
**Scientist, National Reaserch Centre on Equines, Hisar, India
***Prof and Head (Retd.), 2518, Sector D-II, Vasant Kunj, New Delhi-110 070, India
Trypanosomosis due to Trypanosoma evansi (surra) is a major enzootic disease of the dromedary camel. Recent surveys have confirmed the widespread occurrence of the disease within a wide range of climate and vegetation zones in Asia, the Middle East, the Far East, Central and South America and usually outside the tsetse belt in Africa. Only a few reliable data exist on the distribution and seasonal prevalence of the disease in endemic areas. Reports of over 12000 cases of surra in India during 1940-42 showed that disease prevalence peaked during the months of the monsoon season. Epidemiological studies in Mauritania by Jacquit et al (1994) in dromedaries from herds of 3 types revealed infection levels ranging from 4.4-14.9% by blood smear examinations and 11-38% by immunofluorescent complement fixation tests (ICFT). Mean T. evansi prevalence ranged from 11.1% by microhaematocrit centrifugation technique to 28.1% using a monoclonal antibody based card latex agglutination test (Suratex) and 37.9% using CATT/T. evansi. An epidemiological survey of camel trypanosomosis conducted for the first time in Morocco in 1997 and 1998, found the overall seroprevalence of 14.1% by CATT and 18.2% by Ab-ELISA. Concentration techniques were shown to improve the chances of demonstrating trypanosomes in the blood of infected animals. The most applicable and commonly used technique is microhaematocrit centrifugation technique (MHCT). Buffy coat technique devised by Murray et al (1977) further improved this parasitological technique. The MHCT can detect trypanosomes in camel blood 6 to 10 days earlier than in wet or thick blood films. Inoculation of laboratory rodents with blood from suspected infectious camels is a very sensitive method for detecting low parasitaemia caused by T. evansi. The development of an enzyme linked immunosorbent antibody assay (ELISA) (Voller et al, 1976) was a major breakthrough for the detection of antibodies in serum by the specific antigen. A highly sensitive and specific PCR based assay for the detection of T. evansi in the blood of different animals and the vector was developed.
Key words: Camels, diagnosis, epidemiology, surra, Trypanosoma evansi