Understanding the transmission ecology of parasites involves the challenge of studying the complexity of life-cycles at multiple levels of biological organisation and at various space-time scales. We think that a single field of science alone cannot fully address this issue and that a way to understand such complexity is to connect various fields of science, to consider the whole transmission system, and to identify which are the variables reasonably accessible to measurement and the relevant scales at which they may provide information about transmission processes and indicate a higher risk of transmission⁄emergence. Based on ongoing studies carried out in Europe and in China, the aim of the present paper is to discuss this approach and to show how results obtained from mass-screening of human populations may be combined to those obtained from small mammal and landscape ecology studies and modelling to promote an understanding of Echinococcus multilocularis transmission and to determine how differences in the time-space scales at which human infection and small mammal population dynamic processes occur may complicate the analysis.

Human echinococcosis is a zoonotic larval cestode disease usually caused by Echinococcus granulosus or E. multilocularis. Infection is chronic taking years for symptoms to develop. Because diagnosis and treatment are difficult and reservoirs of infection are maintained in domestic livestock, dogs or wildlife, the disease is difficult to assess in terms of public health and requires long-term control interventions. Estimates of numbers of cystic echinococcosis cases that may occur in 2 large endemic zones, North Africa⁄Middle East and China⁄Central Asia, indicates > 423,000 and > 484,000 cases respectively. Globally, 3.6 million DALYs could be lost due to echinoccocosis. Echinococcosis is therefore a neglected disease which is under-reported and requires urgent attention in common with a number of other zoonoses in order to reduce morbidity and to help alleviate poverty in poor pastoral areas of the sub-tropics and temperate zones

Three human taeniid species, Taenia solium, Taenia saginata and Taenia asiatica are distributed in Indonesia. A field survey conducted in Bali from 2002 to 2006 showed that the prevalence of taeniasis was highly variable among four districts (1.1-27.5%), and only two cysticercosis cases due to T. solium infection were detected. All tapeworms (n = 66) expelled from 66 tapeworm carriers were confirmed to be T. saginata by mitochondrial DNA analysis. A total prevalence of 13.0% (19⁄146) for T. solium taeniasis was found in Jayawijaya District, Papua (Irian Jaya). It included 14 of 88 (15.9%) in 1999 and 5 of 58 (8.6%) in 2001, while the seroprevalence of cysticercosis in humans by sub-district in Papua ranged from 0.0% in a non-endemic area to 48.5% in an endemic area from 1996 to 2005. The seroprevalence of cysticercosis in pigs and dogs in Jayawijaya ranged from 8.5% to 70.4% (1998-1999) and 4.9% to 33.3% (2000-2002), respectively. A 2003-2006 survey of 371 local people in Samosir island, north Sumatra revealed 6 of 240 (2.5%) to be infected with T. asiatica; 2 of 58 (3.4%) and 4 of 182 (2.2%) cases were detected in 2003 and 2005, respectively. This brief review summarizes the present situation of taeniasis and cysticercosis, the distribution of three human taeniid species, and the risk factors⁄transmission aspects of these tapeworm infections in Bali, Papua, and north Sumatra regions of Indonesia.

BACKGROUNDOvergrazing was assumed to increase the population density of small mammals that are the intermediate hosts of Echinococcus multilocularis, the pathogen of alveolar echinococcosis in the Qinghai Tibet Plateau. This research tested the hypothesis that overgrazing might promote Echinococcus multilocularis transmission through increasing populations of small mammal, intermediate hosts in Tibetan pastoral communities.

METHODSGrazing practices, small mammal indices and dog Echinococcus multilocularis infection data were collected to analyze the relation between overgrazing and Echinococcus multilocularis transmission using nonparametric tests and multiple stepwise logistic regression.

RESULTSIn the investigated area, raising livestock was a key industry. The communal pastures existed and the available forage was deficient for grazing. Open (common) pastures were overgrazed and had higher burrow density of small mammals compared with neighboring fenced (private) pastures; this high overgrazing pressure on the open pastures measured by neighboring fenced area led to higher burrow density of small mammals in open pastures. The median burrow density of small mammals in open pastures was independently associated with nearby canine Echinococcus multilocularis infection (P = 0.003, OR = 1.048).

CONCLUSIONOvergrazing may promote the transmission of Echinococcus multilocularis through increasing the population density of small mammals.

Animals ; Dog Diseases ; transmission ; Dogs ; Echinococcosis ; transmission ; veterinary ; Echinococcus multilocularis ; Humans ; Population Density ; Tibet

BACKGROUNDAlveolar echinococcosis is a major zoonosis of public health significance in western China. Overgrazing was recently assumed as a potential risk factor for transmission of alveolar echinococcosis. The research was designed to further test the overgrazing hypothesis by investigating how overgrazing influenced the burrow density of intermediate host small mammals and how the burrow density of small mammals was associated with dog Echinococcus multilocularis infection.

METHODSThe study sites were chosen by previous studies which found areas where the alveolar echinococcosis was prevalent. The data, including grass height, burrow density of intermediate host small mammals, dog and fox fecal samples as well as Global Positioning System (GPS) position, were collected from field investigations in Shiqu County, Sichuan Province, China. The fecal samples were analyzed using copro-PCR. The worms, teeth, bones and hairs in the fecal samples were visually examined. Single factor and multifactor analyses tools including chi square and generalized linear models were applied to these data.

RESULTSBy using grass height as a proxy of grazing pressure in the homogenous pasture, this study found that taller grass in the pasture led to lower small mammals' burrow density (chi(2) = 4.670, P = 0.031, coefficient = -1.570). The Echinococcus multilocularis worm burden in dogs was statistically significantly related to the maximum density of the intermediate host Ochotona spp. (chi(2) = 5.250, P = 0.022, coefficient = 0.028). The prevalence in owned dogs was positively correlated to the number of stray dogs seen within a 200 meter radius (Wald chi(2) = 8.375, P = 0.004, odds ratio = 1.198).

CONCLUSIONSOur findings support the hypothesis that overgrazing promotes transmission of alveolar echinococcosis and confirm the role of stray dogs in the transmission of alveolar echinococcosis.

Animals ; China ; Dog Diseases ; parasitology ; transmission ; Dogs ; Echinococcosis ; parasitology ; transmission ; Echinococcus multilocularis ; physiology ; Ecology ; Poaceae ; growth & development ; parasitology ; Tibet