Parasitology



Modelling the transmission dynamics of Echinococcus granulosus in dogs in rural Kazakhstan


P. R. TORGERSON a1a2c1, B. S. SHAIKENOV a3, A. T. RYSMUKHAMBETOVA a3, A. E. USSENBAYEV a4, A. M. ABDYBEKOVA a5 and K. K. BURTISURNOV a6
a1 Faculty of Veterinary Medicine, University College Dublin, Ballsbridge, Dublin 4, Ireland
a2 Institute of Parasitology, University of Zurich, Winterthurerstrasse 266a, 8057 Zurich, Switzerland
a3 Kazakh Academy of Sciences, Institute of Zoology, Academgorodok, Almaty, Kazakhstan
a4 Skrabin Veterinary Research Laboratory, Taras, Kazakhstan
a5 Kazakh Veterinary Research Institute, Kazakh Ministry of Education and Science, Riembek 223, Almaty, Kazakhstan
a6 Department of Biology, Turkestan Medical College, University of Turkestan, Turkestan, Kazakhstan

Article author query
torgerson p   [PubMed][Google Scholar] 
shaikenov b   [PubMed][Google Scholar] 
rysmukhambetova a   [PubMed][Google Scholar] 
ussenbayev a   [PubMed][Google Scholar] 
abdybekova a   [PubMed][Google Scholar] 
burtisurnov k   [PubMed][Google Scholar] 

Abstract

Cystic echinococcosis, caused by Echinococcus granulosus, is an emerging disease in many parts of the world and, in particular, in eastern Europe and the former Soviet Union. This paper examines the abundance of infection of E. granulosus in the definitive host in southern Kazakhstan. Observed data are fitted to a mathematical model in order to decide if the parasite population is partly regulated by definitive host immunity and to define parameters in the model. Such data would be useful to develop simulation models for the control of this disease. Maximum likelihood techniques were used to define the parameters and their confidence limits in the model and the negative binomial distribution was used to define the error variance in the observed data. The results indicated that there were 2 distinct populations of dogs in rural Kazakhstan which had significantly different exposures to E. granulosus. Farm dogs, which are closely associated with livestock husbandry, particularly sheep rearing, had a relatively high mean abundance of 631 parasites per dog and a prevalence rate of approximately 23%. The best fit to the model indicated that there was significant herd immunity in the dog at this infection pressure. In contrast, village dogs which were more likely to be kept as pets had a much lower mean abundance of parasites of only 27 parasites per dog and a lower prevalence of 5·8%. With this village population of dogs, the best fit indicated negligible herd immunity.

(Received May 18 2002)
(Revised September 25 2002)
(Revised November 16 2002)
(Accepted November 22 2002)


Key Words: Echinococcus; mathematical modelling; epidemiology; maximum likelihood.

Correspondence:
c1 Institute of Parasitology, University of Zürich, Winterthurerstrasse 266a, CH-8057, Zürich, Switzerland. Fax +41 1 63 58907. E-mail: paul.torgerson@access.unizh.ch


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