Agricultural restructuring and gastrointestinal parasitism in domestic ruminants on the rangelands of Kazakhstan.

In order to evaluate the epidemiology of parasitism in farmed ruminants in the changed agricultural context in Kazakhstan, 505 cattle, sheep and goats were surveyed for gastrointestinal parasitism using coprological examination, and a further thirty sheep and four goats using post mortem extraction of helminths. The dominant helminth genera were Marshallagia, Nematodirus and Trichostrongylus. Haemonchus was also present. Faecal egg counts were low (mean abundance 0-115 eggs per gram in different groups), and there was no relationship between faecal egg density and body condition score. Eggs of Nematodirus spp. were more common in sheep less than 1 yr of age, whereas those of the Trichostrongylidae were generally more common in adult sheep. Based on faecal egg counts, sheep grazing on common land close to permanent human settlements were generally no more heavily infected than those grazing the remote open plains. This could be due to a non-linear relationship between livestock numbers and stocking density. We suggest that cessation of strategic nematode control in the region following post-Soviet agricultural reform was offset by a general reduction in stocking density, such that parasite burdens remained low. However, recovery in livestock numbers is likely to lead to increased levels of infection and production loss unless sustainable control strategies are put in place.

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.

Human cystic echinococcosis in Kyrgystan: an epidemiological study.

Human cystic echinococcosis (CE), caused by Echinococcus granulosus, is an emerging disease in central Asia. This study examined official data on the incidence of CE between 1991 and 2000 and studied routine hospital records in the main surgical hospitals in Bishkek, Kyrgystan, between 1990 and 2000. In addition, a cross-sectional ultrasound study of a rural population was undertaken in northern Kyrgystan. The results of this study have indicated that the annual incidence of CE over the whole of Kyrgystan has increased from 5.4 cases per 100,000 in 1991 to 18 cases per 100,000 in 2000. Likewise, hospital admissions in Bishkek, due to CE, have increased from an estimated 21 cases in 1990 to approximately 127 and 124 in 1998 and 1999, respectively. Similarly, paediatric cases have increased from 2 in 1990 to 82 in 2000. There was no obvious association with occupation of affected adults although a disproportionate number of hospital cases were registered as unemployed compared to the general population. Whilst there was no gender difference in hospital admissions amongst children, men were more likely to undergo hospital treatment than women. Fifty percent of cysts were recorded as hepatic cysts with forty seven percent recorded as pulmonary cysts. Analysis of the data suggests that the likelihood of an affected patient having a hepatic cyst decreased with age. The results of the cross-sectional study indicated that 20 of 1486 subjects (1.35%) examined by ultrasound had an abdominal hydatid cyst. By extrapolating the ratio of pulmonary to hepatic cysts recorded in the hospital population and adjusting for age it is possible that as much as 3.4% of the rural population may have sub-clinical CE. Analysis of the possible risk factors in the cross-sectional study revealed that subjects who had CE were less likely to use well water as their water supply than non-infected subjects.

The emerging epidemic of echinococcosis in Kazakhstan.

Since independence from the Soviet Union in 1991 the annual surgical incidence of cystic echinococcosis in Kazakhstan has increased from 1.4 cases/100,000 in 1991 to 5.9 cases/100,000 in 2000. In some regions the annual surgical incidence is now over 10 cases/100,000. Twenty-nine percent of recorded cases in 2000 were in children aged < 14 years, which indicates recent transmission. Most of the cases are occurring in the regions where the sheep industry is concentrated, indicating that the zoonotic sheep strain of Echinococcus granulosus is the likely cause of the problem. The gross domestic product (GDP) of Kazakhstan has declined by nearly 50% since independence. Concurrently there has been decreased health spending with decreases in the numbers of hospitals, hospital beds and physicians. This situation suggests that an increase in the diagnosis of echinococcosis is an unlikely explanation for the epidemic but that there is an increase in transmission to the human population.