STUDIES ON TROPICAL THEILERIOSIS IN TURKEY

biotec at goliat.ugr.es biotec at goliat.ugr.es
Sat Mar 22 06:33:38 EST 1997


STUDIES ON TROPICAL THEILERIOSIS IN TURKEY

 	Tropical theileriosis, Theileria annulata infection, is the 
most important disease of cattle in Turkey and is a major threat to 
the high yielding exotic cattle introduced into the country in 
order to improve the productivity of local breeds.  A vaccination 
programme, using locally produced vaccine, has operated for several 
years but despite these efforts to control the disease the 
importance of tropical theileriosis in Turkey is increasing.  The 
inability to control the disease is related to lack of 
epizootiological knowledge and incorrect targeting of the vaccine. 
 
	
	The present study (STD2A 170), funded by the European 
Union, and coordinated by Professor C.G.D. Brown, CTVM, University 
of Edinburgh was undertaken with the aims of improving the 
epidemiological understanding of tropical theileriosis in selected 
areas of Turkey by the use of sero-epidemiological methods and the 
study of tick transmission patterns of T.annulata in four species; 
Hyalomma anatolicum anatolicum, H.a. excavatum, H.detritum and 
H.marginatum, widely distributed in Turkey.  Stocks of T.annulata 
isolated from clinical cases of tropical theileriosis in villages 
in Central and Eastern Anatolia were isolated in tissue culture and 
cryopreserved for further study which included characterisation by 
biochemical methods.

	The epidemiology of tropical theileriosis in central 
Anatolia Turkey was investigated over a four year period by 
serology, identification of carrier animals, clinical disease and 
the analysis of tick species.  The infection rates in ticks and 
their biology was investigated in an attempt to explain infection 
and disease patterns and the levels of Theileria annulata infection 
in the region.  Four tick species, Hyalomma anatolicum anatolicum, 
H.a. excavatum, H.detritum and H.marginatum were identified as 
vectors of T.annulata in Central Anatolia.  The disease coincided 
with the feeding of adult ticks in late spring / early summer 
related to an increase in temperature.  Female ticks were found to 
lay eggs in summer with the hatching and development of larvae 
followed by feeding and the moult into nymphs in late summer / 
early autumn.  The nymphs then fed on carrier cattle in autumn when 
there is no disease and over wintered: either as engorged nymphs, 
in which case T.annulata remains as zygotes in the nymph and 
develops into sporoblasts and sporozoites the following year in 
spring when temperatures increase and the nymphs moult into adults; 
or as adults to which the nymphs may moult in autumn, with the 
concomitant development of T.annulata into sporoblasts and 
sporozoites.

	Over four years the sero-epidemiology of the disease around 
Ankara was studied using the indirect fluorescent antibody test on 
sera collected from cattle and compared with blood smears to detect 
piroplasms in order to determine the extent of T.annulata 
infection.  Two pilot studies were carried out at the State 
Veterinary Laboratory at Pendik; the first describes the isolation 
and cryopreservation of cell lines isolated from the Aydin region 
of western Turkey; the second a preliminary study on the 
clonability of the Pendik T.annulata vaccine cell line.

	The phenotypic diversity of stocks of T.annulata isolated 
from cattle with clinical tropical theileriosis around Ankara in 
central Anatolia and Elazig in eastern Anatolia was examined.  This 
was done by isoenzyme analysis, of glucose phosphate isomerase 
(GPI), lactate dehydrogenase (LDH) and hexokinase (HK).  The GPI 
assays were carried out on piroplasms isolated directly from 
animals, on schizonts grown in cell culture from infected animals 
and occasionally on sporozoites obtained from ticks feeding on 
experimentally infected animals.  The T.annulata parasites isolated 
from clinical cases showed polymorphism with respect to GPI 
isoenzymes which appeared to arise from various combinations of 
parasite populations.  The GPI pattern of the vaccine cell lines at 
Pendik showed a simple triplet pattern, reflecting a decrease in 
the number of populations present.  LDH piroplasm patterns were 
identical for the 10 or so stocks examined, indicating that it 
could be a species-specific marker.  The  variation of GPI patterns 
was followed for two stocks over a period of two years during 
cattle-tick passage.  Differences were found in the banding 
patterns in the bovine host, the tick vector and in tissue culture 
conditions but a stable isoenzyme profile was the norm.

	In vivo transmission studies were carried out on the Ankara 
stock of T.annulata and the clones derived from it.  The parent 
stock and clones were initially used to infect calves, then ticks 
fed on these calves to assess the infectivity of each clone for 
ticks.  GPI patterns were used to trace the parasite through ticks 
and cattle.  The clones and parent stock induced protection in 
cattle following mild disease.  Ticks fed on the cattle were not 
able to pick up a proportion of the clones, representing important 
biological differences between these clones.  The virulence of the 
clones appeared to be enhanced by passage through the tick.

	The infection rates in four species of Hyalomma ticks which 
occur widely in central Anatolia were compared with respect to 
their ability to pick up T.annulata piroplasms from experimentally 
infected calves.  All species of ticks were infected by the 
parasite with no significant differences.  The efficacy of the 
Pendik theileriosis vaccine was assessed in a series of 
experiments.  Protection afforded by various doses, was compared 
with that provided by the standard vaccination dose of 107 cells 
against challenge with virulent heterologous stocks.  This study 
showed that, with an attenuated and cryopreserved vaccine such as 
this a large cell dose was necessary to ensure protection.

For further information contact:

Professor Fahri Sayin
Faculty of Veterinary Medicine
University of Ankara, Diskapi
06110 Ankara Turkey

OR

Professor C.G.D. Brown
Centre for Tropical Veterinary Medicine
University of Edinburgh
Easter Bush, Roslin
Midlothian EH25 9RG
Scotland



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