A silent breakthrough in animals vaccinated with attenuated cell line of T. annulata


First joint AITVM-STVM Conference, Berlin, Germany, 4 - 08 September 2016, pp.101

  • Publication Type: Conference Paper / Full Text
  • City: Berlin
  • Country: Germany
  • Page Numbers: pp.101
  • Van Yüzüncü Yıl University Affiliated: Yes


Tick-borne diseases: Theileria vaccines 

A silent breakthrough in animals vaccinated with attenuated cell line of T. annulata

Huseyin Bilgin Bilgic1*, Ayca Aksulu1, Ahmet Hakan Unlu2, Serkan Bakirci1, Onur
Kose1, Selin Hacilarlioglu1, Hasan Eren1, William Weir3, Tulin Karagenc1

1Faculty of Veterinary Medicine, Department of Parasitology, Adnan Menderes
University, Aydın, Turkey
2University of Yüzüncü Yıl, Gevaş Vocational School, Van, Turkey
3Institute of Biodiversity Animal Health and Comparative Medicine, College of
Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United

Tropical theileriosis is caused by the protozoan parasite Theileria annulata and is
transmitted by several species of Ixodid ticks of the genus Hyalomma. It is an
economically important bovine disease, which is widespread between longitude
30?W-150?E and latitude 15?-60?N. Apart from the use of acaricides, the most effective
way to protect cattle from disease is the use of attenuated schizont vaccine for
immunization. Immune cattle develop a solid immunity against the same and to a
certain degree against heterologous strains. Such heterologous parasites can alter
the population structure and cause the formation of genetically diverse populations if
transmission occurs. Sexual recombination and transmission intensity play a
significant role in generating genetic diversity. Recent field reports have been
indicated an increasing number of the breakthrough cases in vaccinated animals.
And some suffered from severe theileriosis and died. This raised the question of “Can
attenuated schizont vaccine protect against challenge with local parasites and are
genotipically diverse parasites able to cause severe clinical infection in vaccinated
cattle?”. A total of 143 animals vaccinated by attenuated schizont vaccine
(TEYLOVACTM, Vetal) were screened between April-September 2013. Blood
samples were collected before and 45 days after vaccination and at 30 days intervals
during the disease season. DNA samples were initially screened for the presence of
T.annulata using cytob1 PCR. Then, all T.annulata positive samples were genotyped
using 23 mini and microsatellite polymorphic markers. Highresolution Spreadex gels
(Elchrom ScientificTM) were used to determine the size of each different mini and
microsatellite alleles of T.annulata. Results obtained from genotyping analysis
indicated that a certain level of protection was maintained in animals after
vaccination, however TEYLOVACTM did not provide same level of protection against
heterologous genotypes in the field. T.annulata positive animals were found to
harbour multiple parasite genotypes and the mean number of alleles per locus
ranged from 0.27 to 2.94. Principal co-ordinate analysis using the multi-locus
genotype dataset showed a high level of genotypic diversity within the same farm
and/or between different regions. Some of the detected MLGs from certain farms
were cluster into different quadrants, suggesting geographic sub-structuring of the
field population. The results presented here highlight the significant role of
transmission intensity together with cattle carrying genetically diverse populations
have the potential to cause severe disease even in vaccinated cattle.
This study was financially supported by a grant from the TUBITAK (Ref. TUBITAK-