Climate change futures: health, ecological and economic dimensions

The rise in minimum temperature results in the expansioninto higher latitudes, which is explained by theinverse relationship between tick survival and thedegree of subfreezing temperature exposure (Vandyk etal. 1996). This trend is clearly shown by the spreadingof suitable area north into Canada. Though I.scapularis has been collected from a variety of locationsin Canada (Keirans et al. 1996, Scotter 2001),establishment has only been shown for a limited numberof locations in southern Ontario (Schwartz et al.1997). Climate change may provide the conditionsnecessary to yield reproducing populations of I. scapulariseither by the systematic advancement from southof the border by movement on mammal hosts or byintroductions via attachment to bird hosts (Klich etal. 1996).SPECIFIC RECOMMENDATIONSFurther study of Lyme disease and other tick-borne diseasesis warranted. Tick-borne diseases includebabesiosis (an animal, malaria-like illness), erhlichiosis(bacterial), Rocky Mountain spotted fever and Q fever(rickettsial diseases), and especially in Europe, tickborneencephalitis (a viral disease). The possible roleof ticks is being studied in the investigation of an outbreakof tularemia (“rabbit fever”) that has persisted onMartha’s Vineyard, MA (USA) since 2000. A Lyme-likedisease has been reported in the southern US(Mississippi, South Carolina, Georgia, Florida, andTexas) that also responds to antibiotics, and the possiblerole of other ticks in transmitting Lyme is understudy.Minimum temperature increase alsoresults in the extension of suitabilityinto higher altitudes. Elevation is animportant limiting factor for I. scapularispopulations as it indirectly affects populationestablishment through its influenceon the complex interactionbetween climate, physical factors andbiota (Schulze et al. 1994). As a resultof increasing temperatures, the modelpredicts advancement of suitability intothe southern Appalachian Mountains.Models that predict disease emergence can be valuabletools for preparing health professionals andstrengthening public health interventions. Personal protectivemeasures for high-risk populations can reduceinfection rates. Environmental methods, including hosttargetedvaccination and larvacides, have shownpromise and have the potential to limit the spread ofLyme disease.47 | INFECTIOUS AND RESPIRATORY DISEASESCCF-II: SURPRISE IMPACTSLyme disease is a slowly advancing disease, given itscomplex life cycle involving ticks, deer, white-footedmice and the supporting habitat and food sources forall these elements. Very warm winters may change thesuitable habitat more rapidly than expectations basedon changes in average temperatures alone. But, dueto the many components of the life cycle, and the twoyearcycle of the ticks themselves, it is unlikely that thisdisease will change its distribution and incidenceabruptly and explosively.CASE STUDIES