Responses in animals vaccinated with theTheileria annulata (Hisar) cell culture vaccine

Abstract

Bovine tropical theileriosis caused by Theileria annulata is an economically important disease of cattle in India. The disease has assumed paramount importance with the intensification of cross-breeding programmes aimed at enhancing milk production in the country. To control this disease, a cell culture vaccine was developed in this department by continuous passaging of T. annulata (Hisar) schizonts in vitro. Current work in this department has concentrated on the epidemiology of theileriosis: development of the cell culture vaccine for very young calves and pregnant cows; evaluation of serological responses using immunofluorescent antibody (IFA) tests and Enzyme-linked immunosorbent antibody assays (ELISA); studies on the duration of immunity stimulated by the cell culture vaccine; the immune/susceptible status of calves born to vaccinated dams. Results have shown the following. Clinical cases of theileriosis were mainly observed in young calves below two months of age followed by adults in exotic and cross-bred animals. Amongst indigenous animals, only young calves below two months of age suffered from clinical disease. Clinical cases of theileriosis mainly occurred between the months of April to October. The T. annulata schizont cell culture vaccine developed in the department was extensively used in the susceptible calves and pregnant/lactating cows in the field. Sufficiently high antibody titres were detected by both schizont as well as piroplasm antigen using both ELISA and IFAT. The results indicated that the vaccine was safe, potent and effective for all breeds and age groups of cattle under field conditions. ELISA was standardised for T. annulata using three antigens, viz.: soluble piroplasm, soluble schizont and cellular schizont antigens. Comparison of results with IFAT showed that ELISA is more sensitive, objective, reliable and specific as well as less cumbersome than IFAT. Piroplasm, cellular schizont and soluble schizont antigens were found to be suitable for the detection of antitheilerial antibodies as per their order in ELISA. Studies on the duration of immunity stimulated by the T. annulata schizont cell culture vaccine indicated that immunity started waning after six months. Calves born of dams immunised against T. annulata with the cell culture vaccine were found to be fully susceptible to theileriosis soon after birth. This indicated that there was no passive transfer of immunity from dams to their offspring through colostrum.

Identification and Analysis of Immunodominant Antigens for ELISA-Based Detection of Theileria annulata

“…Different forms of antigen preparation such as crude antigen extracts and stage-specific recombinant antigens have been used to develop ELISAs. However, ELISAs with crude antigen extracts, obtained from macroschizont and piroplasms [ 31 , 32 ], provided lower sensitivity and specificity than IFAT. Moreover, there were issues with shelf-life and quality control.…”

Molecular and Phylogenetic analysis revealed new genotypes of Theileria annulata parasites from India

“…However, the molecular based assays such as PCR have proven to be the most reliable tool for detecting Theileria parasites in clinical and subclinical cases of theileriosis especially detecting carrier state [ 3 – 7 ]. A number of control measures have been employed such as acaricides application, chemotherapy and vaccination, however, due to lack of knowledge on the prevalence of Theileria infection these measure are not effective [ 8 , 9 ].…”

Single dilution ELISAs using soluble piroplasm, cellular schizont and soluble schizont antigens for the detection of antibodies against Theileria annulata

“…Theileria annulata is an important haemoprotozoa that causes a serious leucoproliferative disease of cattle bovine tropical theileriosis in tropical and subtropical countries. The disease is of particular economic importance since exotic "European" cattle were imported into the tropics to increase the productivity of local "Zebu" cattle as exotic cattle and their cross-breds are highly susceptible [1]. The diagnosis of the disease has traditionally been confirmed by examination of Giemsa stained thin blood smears and/or lymph node biopsy smears.…”

“…Following infection, the surviving cattle carry low numbers of piroplasms in erythrocytes for long periods. Examination of smears of animals living under field conditions has been extensively used to estimate the prevalence of carriers and exposure to T. annulata infection [1,4]. However, such a technique is time consuming and may not be very sensitive since piroplasms cannot be detected in blood smears of all carrier animals.…”