ABSTRACT
The current vaccines to control bovine Babesia bigemina (B. bigemina) infection are not fully protective and vaccination failures incur heavy losses to the cattle industry around the world. Using modified micro-aerophilous stationary phase, we developed a culture-derived attenuated live vaccine against B. bigemina and tested a single subcutaneous inoculation of 2 × 108 infected erythrocytes in calves. The protection was measured after a lethal intravenous challenge with 5 × 108 virulent calf-derived B. bigemina. Our results demonstrated that a single shot of attenuated vaccine was capable of inducing robust humoral and cell-mediated immune responses in calves. We found a significant increase in the IgG antibody titers post-challenge and a strong proliferation of both CD4+ and CD8+ T cells contributing towards the protection. Our vaccine provided complete protection and parasitic clearance, which was followed for more than 100 days post-challenge. This immunity against babesiosis was directly linked to strong humoral responses; however, the parasitic clearance was attributed to significant T cells effector responses in vaccinated calves as compared to the infected control calves. We anticipate that these results will be helpful in the development of more efficient culture-derived vaccines against Babesia infections, thus reducing significant global economic losses to farmers and the cattle industry.
ABSTRACT
Bovine babesiosis is an infectious protozoan disease and causes significant economic losses in terms of production loss and mortality. The genus Babesia belongs to the family Babesiidae order piroplasmida and is transmitted by ticks globally. The signs of disease are particularly prominent in old or immuno-compromised animals. The spleen plays a vital role in defence against hemoparasites like Babesia. A young cross-bred cow calf of about 3 months of age was splenectomised to propagate Babesia in vivo experimentally. Prior to splenectomy, the calf was examined through microscopy and PCR analysis and was found negative for any kind of piroplasms including Babesia. The calf was completely splenectomised, but the calf was naturally infected during its postoperative period. The calf expired after naturally acquiring Babesia bigemina and Theileria annulata during the 11 th day of postoperative period owing to increased parasitaemia, exhibiting typical mixed parasitic infection stigmata e.g. reddish urine, elevated temperature up to 41.38°C. This study concluded that complete splenectomy along with dexamethasone administration in the postop period caused exceptional increase in parasitaemia. This parasitaemia couldn't be countered by any symptomatic treatment because of the absence of spleen and greatly reduced immunity of the animal.
