Short report: the use of a polymerase chain reaction to detect Echinococcus granulosus (G1 strain) eggs in soil samples.

Cystic echinococcosis is a re-emerging disease in central Asia. A total of 120 soil samples taken from 30 gardens of rural homesteads in southern Kazakhstan were analyzed for the presence of taeniid eggs using a concentration technique. Of these, 21 (17.5%) were shown to be contaminated with taeniid eggs. These isolated taeniid eggs were further analyzed using a polymerase chain reaction specific for the G1 (sheep) strain of the tapeworm Echinococcus granulosus, and five samples were shown to be positive. This study demonstrates the widespread contamination of the environment with E. granulosus eggs in an Echinococcus-endemic area and thus the potential for indirect transmission of E. granulosus to humans from such sources.

Modelling the transmission dynamics of Echinococcus granulosus in sheep and cattle in Kazakhstan.

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 and prevalence of infection of E. granulosus in cattle and sheep in Kazakhstan. Observed data are fitted to a mathematical model in order to determine if the parasite population is partly regulated by intermediate 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 are significant variations in the infection pressure to sheep depending on their location. In particular sheep from Almaty Oblast and from central and northern Kazakhstan appeared to have a greater exposure than sheep from Jambyl or South Kazakhstan Oblasts. The infection pressure to cattle was somewhat lower in comparison. In common with other similar studies, there was no evidence of parasite-induced immunity in sheep or cattle in Kazakhstan due to natural infection. The highest abundance and prevalence were seen in the oldest age classes of animals.

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

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.

The changing epidemiology of echinococcosis in Kazakhstan due to transformation of farming practices.

In recent years there has been a substantial increase in cystic echinococcosis in Kazakhstan. There are several factors that have contributed to this change in the epidemiology of the disease. The primary reason was the degradation of traditional nomadic system of livestock breeding and closing of large collective farms. Small private farms have started to keep stock year round in closer proximity to permanent human habitation. Furthermore, routine anthelmintic prophylaxis of dogs has been abandoned and there is inadequate control over the use and disposal of animal carcasses. Large mechanized slaughterhouses are no longer operational. Now more people (7-8 times) and more dogs (8-10 times) participate in the husbandry of 1000 sheep, than during Soviet administration. Because of the close association of dogs with man there is the potential for a substantial increase in eggs and of Echinococcus in immediate environment of inhabited houses. Soil samples taken from 61% of yards of village homes contained taeniid eggs and from 35% of yards from around farmsteads. During an examination of 1464 village dogs the average rate of infection with Echinococcus granulosus was 5.8%, whilst the prevalence in 607 shepherd dogs was 23.2%. At present, these dogs represent a major source of infection for people with this dangerous parasite. Examination of hospital records suggested that children and people in occupations associated with animal husbandry were at most risk of infection.