Centre for Food-Borne, Environmental and Zoonotic Infectious Diseases, Public Health Agency of Canada, Saint-Hyacinthe, Québec, Canada. nicholas_ogden@phac-aspc.gc.ca
Northward expansion of the tick Ixodes scapularis is driving Lyme disease (LD) emergence in Canada. Information on mechanisms involved is needed to enhance surveillance and identify where LD risk is emerging.
We used passive and active surveillance and phylogeographic analysis of Borrelia burgdorferi to investigate LD risk emergence in Quebec.
In active surveillance, we collected ticks from the environment and from captured rodents. B. burgdorferi transmission was detected by serological analysis of rodents and by polymerase chain reaction assays of ticks. Spatiotemporal trends in passive surveillance data assisted interpretation of active surveillance. Multilocus sequence typing (MLST) of B. burgdorferi in ticks identified likely source locations of B. burgdorferi.
In active surveillance, we found I. scapularis at 55% of sites, and we were more likely to find them at sites with a warmer climate. B. burgdorferi was identified at 13 I. scapularis-positive sites, but infection prevalence in ticks and animal hosts was low. Low infection prevalence in ticks submitted in passive surveillance after 2004-from the tick-positive regions identified in active surveillance-coincided with an exponential increase in tick submissions during this time. MLST analysis suggested recent introduction of B. burgdorferi from the northeastern United States.
These data are consistent with I. scapularis ticks dispersed from the United States by migratory birds, founding populations where the climate is warmest, and then establishment of B. burgdorferi from the United States several years after I. scapularis have established. These observations provide vital information for public health to minimize the impact of LD in Canada.
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Cites: Am J Trop Med Hyg. 1988 Jul;39(1):105-93400797
Siberian lemmings seem to have lesser noradrenaline (NA) calorigenic action and higher beta-adrenergic "asymmetry" of catecholamine calorigenic effects than the cold- and warmth-adapted laboratory rodents. Selective inhibition of catecholamine effects by beta-adrenoblocking drug propranolol, obvious potentiation of NA effect by caffeine, and compensatory increasing of thermoregulatory musclar contractile activity during the blockade of betaadrenoreceptors under cooling suggest the domineering of betaadrenergic mechanisms of thermogenesis in siberian lemmings and their high thermoregulatory lability.
The alternative prey hypothesis predicts that the interaction between generalist predators and their main prey is a major driver of population dynamics of alternative prey species. In Fennoscandia, changes in climate and human land use are assumed to alter the dynamics of cyclic small rodents (main prey) and lead to increased densities and range expansion of an important generalist predator, the red fox Vulpes vulpes. In order to better understand the role of these potential changes in community structure on an alternative prey species, willow ptarmigan Lagopus lagopus, we analyzed nine years of population census data from SE Norway to investigate how community interactions affected their population dynamics. The ptarmigan populations showed no declining trend during the study period, and annual variations corresponded with marked periodic small rodent peaks and declines. Population growth and breeding success were highly correlated, and both demographic variables were influenced by an interaction between red fox and small rodents. Red foxes affected ptarmigan negatively only when small rodent abundance was low, which is in accordance with the alternative prey hypothesis. Our results confirm the important role of red fox predation in ptarmigan dynamics, and indicate that if small rodent cycles are disrupted, this may lead to decline in ptarmigan and other alternative prey species due to elevated predation pressure.
OBJECTIVE: The authors reviewed the pathophysiology and clinical management of endemic alveolar hydatid disease in Alaskan Eskimos, incorporating recent developments in diagnosis and treatment. SUMMARY BACKGROUND DATA: Alveolar hydatid disease is a highly lethal zoonotic infection caused by the larval stage of Echinococcus multilocularis. This cestode is restricted geographically to northern climates, where foxes and small rodents represent the natural hosts. Domestic dogs also may serve as definitive hosts, and thus, transmit the parasite to humans. Human infection is characterized by the development of a cancer-like hepatic mass, which may extend to adjacent structures or metastasize to distant sites. If the infection goes untreated, mortality reaches 80%. METHODS: The medical records of all patients with alveolar hydatid disease diagnosed or treated at the Alaska Native Medical Center between 1951 and 1993 were reviewed. Forty-two cases of active disease are presented. RESULTS: Nine patients underwent resection of hepatic lesions with intent to cure, and each had a favorable result. Average post-diagnosis survival of those patients was 22 years; six still are living and free of disease. Partial resections or drainage procedures were performed in ten patients. Chemotherapy was used to augment the surgical treatment of eight patients, and four received chemotherapy alone, resulting in improved outcomes compared with historic controls. Late complications included hepatic abscess, biliary obstruction, and portal venous hypertension. CONCLUSIONS: Whereas alveolar hydatid disease rarely is encountered in other areas of North America, the biologic potential for spread of the disease may be increasing because of illegal importation of infected foxes to the Eastern seaboard. Therefore, the surgical community should maintain an awareness of the diagnosis and management of this potentially devastating parasitic infection.
The variability of four microsatellite loci of rodents, caught from the head part of Eastern Urals Radioactive Trace (EURT), along with the rodents inhabiting contiguous zone with background radiation level and distant-reference territory, was analyzed forthe first time. Differences in the parameters of genetic diversity between northern red-backed voles from the EURT zone and from the reference population were detected. An increase in some indices of genetic diversity in animals from a contiguous to the EURT zone was found; this is probably associated with animal migration and configuration of the area of pollution. A transfer of radiation-induced effects to the contiguous territories and a decrease in the possibility of fixation of adaptations in a series of generations of mobile rodent species in the area of local radioactive pollution are consequences of migrations. The results of the study make it possible to recommend microsatellite markers for the analysis of radiation-induced effects in rodents as model objects of radioecological monitoring.
The paper reviews as zoonosis the disease called Nephropathia epidemica in north European countries. The etiology is as yet unsolved but a viral one is highly suspected with small rodents (voles and mice) as the source of infection. Based on the epidemiological peculiarities of the disease, the ecology of the agent and hypothetical ways of transmission of infection from small rodents to man are discussed.
The outbreak of hemorrhagic fever with renal syndrome (HFRS) in the Republic of Bashkortostan, resulting in 10,057 registered cases of the disease (287 cases per 100,000 of the population), was analyzed. HFRS cases among the population were registered in 52 out of 54 regions of Bashkortostan. 31% of the total number of patients were the inhabitants of rural regions (170 cases per 100,000) and 69% were urban dwellers (295 cases per 100,000), mainly in Ufa (512 cases per 100,000). HFRS morbidity among males was fourfold higher than among females. In 70% of cases persons aged 20-49 years were affected. 5% of the total number of patients were children aged up to 14 years. In 34 cases (0.4%) the severe clinical course of the disease had a fatal outcome. Cases of HFRS were registered from April 1997 till March 1998 with the highest morbidity rate observed during the period of August-December. In most cases (46.8%) both urban and rural dwellers contacted infection during a short-term stay in the forest. As the result of the serological examination of the patients, all HFRS cases were etiologically attributed to hantavirus, serotype Puumala. The main natural reservoir of this virus and the source of human infection in Bashkortostan were bank voles (Clethrionomys glareolus), the domination species among small mammals in this region.
At the period of 1982 - 2003, morbidity rate in pseudotuberculosis and the Yersinia pseudotuberculosis culture rates in groups of servicemen (from different abiotic objects, from humans and small rodents) in different geographic zones were studied. The cases of the isolation of Y. pseudotuberculosis were most frequently registered in groups of servicemen in the Far East and the Kola Peninsula. In these regions the highest morbidity rate in pseudotuberculosis was registered among servicemen. The contamination rate of vegetables during the year was always greater than in other objects under study, including small rodents. The study demonstrated that in the Armed Forces could appear, temporary and relatively constant anthropurgic foci of pseudotuberculosis even in non endemic regions. They were formed in the objects of the food supply service due to the supply of contaminated vegetables. Synanthropic rodents played a secondary role, though they too facilitated the formation of new anthropurgic foci. Under definite conditions anthropurgic foci could exist autonomously, independently of natural foci.
