Ecology and conservation biology of avian malaria

Abstract

Avian malaria is a worldwide mosquito-borne disease caused by Plasmodium parasites. These parasites occur in many avian species but primarily affect passerine birds that have not evolved with the parasite. Host pathogenicity, fitness, and population impacts are poorly understood. In contrast to continental species, introduced avian malaria poses a substantial threat to naive birds on Hawaii, the Galapagos, and other archipelagoes. In Hawaii, transmission is maintained by susceptible native birds, competence and abundance of mosquitoes, and a disease reservoir of chronically infected native birds. Although vector habitat and avian communities determine the geographic distribution of disease, climate drives transmission patterns ranging from continuous high infection in warm lowland forests, seasonal infection in midelevation forests, and disease-free refugia in cool high-elevation forests. Global warming is expected to increase the occurrence, distribution, and intensity of avian malaria across this elevational gradient and threaten high-elevation refugia, which is the key to survival of many susceptible Hawaiian birds. Increased temperatures may have already increased global avian malaria prevalence and contributed to an emergence of disease in New Zealand.

Mosquito Communities and Avian Malaria Prevalence in Silvereyes (Zosterops lateralis) Within Forest Edge and Interior Habitats in a New Zealand Regional Park

“…Similar results have been demonstrated for avian malaria, with deforestation producing variable prevalence patterns at both local and regional scales (see Sehgal 2010, LaPointe et al 2012). For example, recent studies in Africa by Bonneaud et al (2009) and Loiseau et al (2010) found higher Plasmodium prevalence in birds inhabiting pristine forests, whereas Chasar et al (2009) revealed one parasite species was more abundant in disturbed sites and another more so in pristine sites.…”

“…However, this model is likely not applicable to continental ecosystems due to the introduced vector-parasite and naïve host system, and the Hawaiian situation is unique in that there were no bloodsucking insects prior to the accidental introduction of mosquitoes by humans (Waldbauer 2012). Nonetheless, there is a concern that other island ecosystems with high numbers of endemic birds (most notably New Zealand and the Galapagos) could be similarly affected by the interaction of exotic mosquitoes, anthropogenic environmental change and avian malaria (Derraik and Slaney 2007;LaPointe et al 2012).…”

“…Since their introductions, forest fragmentation and agricultural development have been implicated in increasing avian malaria transmission (LaPointe et al 2012). As an opencontainer breeder and a peridomestic species, C. quinquefasciatus greatly benefits from the clearing of forest for human land uses (Reiter and LaPointe 2007).…”

“…), primarily through their effect on vector species (Patz et al 2000;Harvell et al 2002). In many parts of the world, deforestation for agricultural development is a common anthropogenic driver of changes in parasite transmission rates (Yasuoka and Levins 2007;Sehgal 2010;LaPointe et al 2012). Studies of human malaria in Asia, Africa and the Amazon region have shown that forest fragmentation and increasing edge habitat produce complex host-vector responses; these can either increase or decrease malaria prevalence depending on subsequent land use and the breeding ecology of local vector species (see Yasuoka andLevins 2007, Stefani et al 2013).…”

Assessing the potential of translocating vulnerable forest birds by searching for novel and enduring climatic ranges

“…However, in attempting to explore the viability of translocation of forest bird species across the Hawaiian archipelago, we did not focus our efforts on modeling the distribution of disease and mosquitoes themselves. Besides the general lack of spatial data on the disease and vector, modeling either of these distributions would not address the differential tolerance of forest bird species to disease nor the differential environmental requirements between vector and disease (LaPointe et al., 2012). Nevertheless, because the ongoing and projected range contractions for these forest bird species are strongly related to a warming‐related shift upslope of avian malaria and its vector, it is important to consider how successful efforts to limit the spread of the disease or vector would impact our findings.…”