Immune responses to haemorrhagic septicaemia (HS) vaccination in Trypanosoma evansi infected buffalo-calves.

To assess the immunosuppressive effect of Trypanosoma evansi infection in buffalo-calves on immune responses to heterologous antigen, the study was planned to examine the responses of haemorrhagic septicaemia vaccination in simultaneously and previously (80 days before vaccination) T. evansi-infected buffalo-calves. Eight buffalo-calves were divided into three groups. Buffalo-calves of group A (n = 3) were previously (80 days before primary vaccination with haemorrhagic septicaemia [HS] vaccine) infected with T. evansi (1 x 10(7) tryps.calf(-1); sc) and that of group B (n = 3) were infected with T. evansi (1 x 10(7) tryps.calf(-1); sc) on the day of primary vaccination with HS vaccine. Two healthy uninfected control calves given only HS vaccine were kept in group C. All the buffalo-calves were given a booster dose of vaccine 21 days post-primary vaccination (PPV). Twenty eight days PPV, animals of group A were given trypanocidal quinapyramine prosalt at 6.66 mg kg(-1). Immunosuppressive effect of T. evansi infection was evident from day 7 PPV with HS vaccine. The effect was more pronounced in previously T. evansi-infected buffalo-calves as compared with simultaneously infected buffalo-calves. Group A buffalo-calves appeared to have recovered from the immunosuppressive effect after 28 days post-trypanocidal treatment as observed by humoral and cell-mediated immune responses. Immunosuppressive effect to HS vaccination was observed in T. evansi-infected buffalo-calves, and trypanocidal therapy enabled the calves to mount the responses similar to uninfected controls.

Rodents as reservoirs of parasites in India.

We monitored the prevalence of endoparasitic infections of rodents in Punjab State, India, between January 2004 and December 2005. Three species of wild rodents, namely the house rat, Rattus rattus (n= 42), the lesser bandicoot rat, Bandicota bengalensis (n= 34) and the Indian gerbil, Tatera indica (n= 15), were live-captured from houses and crop fields. Examination of various organs revealed that the highest rates of endoparasitic infection occurred in R. rattus (40.5%), followed by B. bengalensis (35.3 %) and then T. indica (20.0%), with an overall infection rate of 35.2%. All three rodent species were found naturally infected with one or more species of helminths. Metacestodes (1-6) of Cysticercus fasciolaris (larvae of Taenia taeniaeformis) were found in all three rodent species (in the liver). In one male T. indica, numerous robust T. taeniaeformis metacestodes were found in oval sacs attached to the mesentery and the abdominal wall, an unusual site. The cauda epididymal fluid of the same gerbil was also found to be infected with a very rare species of strongylid nematode, which could not be identified to genus or species level. It is possible that this nematode is transmitted sexually and thus may affect the reproductive potential of gerbils. This appears to be the first report of this phenomenon. In one B. bengalensis individual, the intestine was found to be obstructed with an acanthocephalan, Moniliformis moniliformis, with concurrent infection with C. fasciolaris in the form of multiple cysts in the liver. Although no natural protozoan infection was found in these field rodents, experimental Trypanosoma evansi infection has been established in all three species with high pathogenicity, and the possibility of sexual transmission was supported by the presence of T. evansi in the cauda epididymal fluid of male rats.