Public Health and Communicable Diseases - SA Health - SA.Gov.au

number of people living in areas of higher denguerisk, from 1.5 billion in 1990 to about 50-60% of globalpopulation in 2085 8 . In Australia, most notified cases ofdengue are from north Queensland, where the vectormosquito Aedes aegypti is endemic. The two mostserious epidemics noted in Queensland during the lastdecade were in 1998 and 2003 respectively (Figure 1),with more than 1,100 cases notified. To date, denguehas not caused outbreaks in southern parts of Australia.However, a recent study suggested that there might bea dengue threat for southern parts of Australia in thefuture. 9Other Flavivirus infections include Japanese encephalitis,Murray Valley encephalitis (MVE) and Kunjin (KUN) virusinfection with less than 100 notified cases annually inAustralia (Figure 1). For MVE and KUN viruses, the majorvector is Culex annulirostris, which breeds in freshwater.Most cases in this category are notified in northernAustralia. There has been only one case of MVE notifiedin South Australia during the last five years. Attentionshould be given to Japanese encephalitis in Australiain order to keep it under control. 10 This is particularlyimportant in north Queensland. Health professionalsneed to keep alert for the potential transmissionof Japanese encephalitis, including correct clinicaldiagnosis, health information sharing and exchange, andhealth education and promotion.MalariaAustralia has claimed to be malaria free since 1983.Since then all notified cases of malaria are believed to beimported and the notified cases have remained relativelystable during the last ten years, with around 700 casesper year (Figure 1). While there is currently no evidencefor local transmission of malaria within Australia, thereis potential for this to occur in view of the presence ofthe main mosquito vector Anopheles farauti. Studiesindicate that increases in the incidence of malaria arestrongly associated with higher temperatures andincreased rainfall. In Australia, the length and intensity ofwet seasons have a significant effect on the distributionof Anopheles farauti. 11 Climate modelling shows thatglobal warming will enlarge the potential range of thisvector, which could extend, by 2030, to a location 800km south of its present limit in Queensland. 12 Therefore,Australian health professionals should remain alert forthis potential risk.Situation in South AustraliaIn South Australia, RRV is the most important vectorbornedisease. There have been more than 1,600 RRVcases notified in the last ten years with the highestnumber occurring in the year 1997 (635 notified cases).There were four epidemics in the period 1992-2003,with the majority of cases acquired from regions alongthe River Murray. There was some evidence of spreadof the disease to regions in which activity of RRV hadnot been previously recognised, such as the Mid-Northand the South-East 13 . In terms of disease distributionamongst the population, it was found that the highestrates occurred in the 30–49 year age range. There wasno significant difference in disease rates between malesand females 13 . BFV is another important concern inSouth Australia, with a sharp increase in cases in 2005and 2006, and notifications ten times higher comparedto a decade ago. Factors contributing to this increaseinclude climatic variation and also increased awarenessamong the general community and GPs of the disease,as well as changes in testing procedures. Healthprofessionals including GPs should pay great attentionto RRV and BFV especially in the areas where the caseshave not identified before. Dengue and other notifiedFlavivirus infections, eg Murray Valley encephalitis, arenot a big threat in South Australia at the moment.Implications for public health practiceMosquito control may be the most effective way toprevent and control the spread of vector-borne diseases.Mosquito surveillance programs have been performed insome States and proved to be effective in identifying thedistribution of mosquito species, presence and activityof the arboviruses. 14,15 A national strategy to enhancethe routine mosquito monitoring and surveillance,which involves the collaboration with local council, Stategovernments and research organisations, could prove tobe most effective in controling and prevent in the spreadof the vector-borne diseases.In addition to maintaining high quality surveillance, anearly warning system should also be set up for bothmosquitos and arbovirus diseases. Time series analysisand spatial analysis 16,17 techniques could be performedto build a predictive model to highlight potential riskareas, using local vector data, meteorological data andother influencing factors eg population dynamics, landuse, vegetable types, reservoir information and socioeconomicindex. These predictive models could assistrisk assessment for policy makers and public healthpractitioners.In South Australia, fortunately, there are somerecent developments in mosquito management.The Environmental Health Service coordinated theimplementation of the SA Integrated MosquitoManagement Strategy (SAIMMS). “This process wasinitiated due to the need to promote and integratemosquito management practices throughout SA toensure that programs are as effective, economical andenvironmentally sensitive as possible”. 18 There are 15agencies in SA involved in this working group, includingthe Local Government Association, EPA, PIRSA and the10