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.

A representative number of 217 camels (Camelus dromedarius) from different areas of western Rajasthan State, India, were examined from July 2002 to May 2003 for Trypanosoma evansi infection. The tests used were parasitological (wet blood film, WBF; stained thin blood smear, TBS), immunodiagnostic (double antibody sandwich enzyme linked immunosorbent assay for antigen detection, Ag-ELISA), and DNA amplification by polymerase chain reaction (PCR). These techniques were compared and the best efficiency was found for the last named (PCR). A prevalence of T. evansi infection was detected in 17.05, 9.67, 4.60 and 4.14% by PCR, Ag-ELISA, TBS and WBF with a sensitivity of 100, 56.75, 27.02 and 24.32%, respectively. PCR revealed a specific 227bp band in positive samples. The intensity of PCR bands was variable in different test samples depending upon the level of infection in the test samples. The history of intermittent fever, emaciation, oedema, poor body condition significantly correlated with positive serological status in ELISA as well as trypanosome DNA detection by PCR.

Parasitological diagnostic methods for surra, one of the most important disease of camels, are slow and may miss up to 50-80% of the true infections during the chronic phase of the disease. Inoculation of laboratory rodents with blood from suspected camels is a very sensitive method for detecting low parasitaemia. The present study was conducted to assess the suitability of the test for surveillance of Trypanosoma evansi infection in field cases. The observations made during the study are reported. The incubation period and course of infection in the rodents is also discussed.

Fenbendazole and morantel citrate at the dose rate of 5.0 mg/kg body weight showed 98 and 91.01% efficacy, and at 7.5 mg/kg body weight showed 100 and 92.79% efficacy, respectively against mixed gastrointestinal nematodoses in camels of the selected canal irrigated area while Sonex at 40 g total dose was 73.52% and at 50 gm total dose was 79.76% efficacious.

The present status of T. evansi infection in camels of Rajasthan was investigated. Blood samples from 436 camels were examined for trypanosome infection by various diagnostic tests including parasitological, chemical, biological and immunodiagnostic tests. Comparison of various tests included in the present study revealed the highest efficacy of MIT (86.23%) followed by ag-ELISA (85.32%), WFE (44.95%), MCT (41.28%), TFE (38.53%), and AGIDT(28.44%). However, the MIT cannot be recommended for use in field conditions owing to its limitations of cost and feasibility. The ag-ELISA was found to be more useful method for undertaking studies to detect natural T.evansi infection in camel.

Evaluation of various diagnostic tests, viz. parasitological tests (wet blood film -WBF), biological test (mouse subinoculation - MSI) and immunodiagnostic tests based on antibody detection (double immunodiffusion test - DID), antigen detection (double antibody sandwich enzyme linked immunosorbent assay Ag-ELlSA) was done in donkeys experimentally infected with Trypanosoma evansi. WBF and MSI detected the infection as early as 96 hr and 48 hr post - infection respectively. Antibodies were detected as early as 13 days post -infection, while the trypanosomal antigens were detected as early as 7 days post - infection. The diagnostic efficacy of MSI was 100% followed by Ag- ELISA, WBF and DID.

One hundred and eight camels (Camelus dromedarius) from Trypanosoma evansi endemic areas of the Thar Desert of Rajasthan State, India, were evaluated by various diagnostic tests including parasitological tests (wet blood film-WBF, stained thick blood film), chemical test (mercuric chloride), biological test (mouse subinoculation-MSI), and immunodiagnostic tests based on antibody detection (double immunodiffusion test-DID, card agglutination test-CATT), antigen detection (double antibody sandwich enzyme linked immunosorbent assay-Ag-ELISA). Of the tested camels 49 were found infected using the WBF of which nine gave false negative results with the mercuric chloride test. The efficacy of MSI was 87.03 percent, while the mercuric chloride test was 60.18 percent efficient. The diagnostic efficacy of CATT (72.22 percent) was found to be much better than DID (28.70 percent). Ag-ELISA was 86.11 percent efficient in detecting trypanosomal antigens. A good correlation was found between the positive results obtained by wet blood film, CATT and Ag-ELISA. It was inferred that CATT can be used to study the seroprevalence of T. evansi with great ease, however, trypanosome antigen detection may give a more accurate idea of the prevalence of T. evansi in an endemic area.

Blood samples from 240 camels (Camelus dromedarius) were examined for trypanosome infection. Of these, 18 (7.50%) were found to be infected using the wet blood Giemsa stain technique, while 76 (31.66%) camels were found to be positive for Trypanosoma evansi antigen using the double antibody sandwich enzyme-linked immunosorbent assay (ELISA). The latter was found to be a more useful method for the detection of current infection.

An evaluation has been made of the protective effect of immunizing pigs with excretory-secretory homologous antigens on Taenia solium infections. This procedure reduced the number of cysticerci established from a challenge infection.