Wildlife disease and conservation in Hawaii: Pathogenicity of avian malaria (Plasmodium relictum) in experimentally infected Iiwi (Vestiaria coccinea)

Abstract

Native Hawaiian forest birds are facing a major extinction crisis with more than 7 5 % of species recorded in historical times either extinct or endangered. Reasons for this catastrophe include habitat destruction, competition with non-native species, and introduction of predators and avian diseases. We tested susceptibility of Iiwi (Vestiaria coccinea), a declining native species, and Nutmeg Mannikins ( Lonchura punctulata), a common non-native species, to an isolate of Plasmodium relictum from the island of Hawaii. Food consumption, weight, and parasitaemia were monitored in juvenile Iiwi that were infected by either single (low-dose) or multiple (high-dose) mosquito bites. Mortality in both groups was significantly higher than in uninfected controls, reaching 100 % of high-dose birds and 90 % of low-dose birds. Significant declines in food consumption and a corresponding loss of body weight occurred in malaria-infected birds. Both sex and body weight had significant effects on survival time, with males more susceptible than females and birds with low initial weights more susceptible than those with higher initial weights. Gross and microscopic lesions in malaria fatalities included massive enlargement of the spleen and liver, hyperplasia of the reticuloendothelial system with extensive deposition of malarial pigment, and overwhelming anaemia in which over 30% of the circulating erythrocytes were parasitized. Nutmeg Mannikins, by contrast, were completely refractory to infection. Our findings support previous studies documenting high susceptibility of native Hawaiian forest birds to avian malaria. This disease continues to threaten remaining high elevation populations of endangered native birds.

Morphological versus molecular identification of avian Haemosporidia: an exploration of three species concepts

“…relictum has been reported from a very broad host and geographical range (Atkinson et al 1995) which suggests this described species masks a cryptic diversity of taxa. We identified P. relictum from 11 birds of 3 families, and found all sequences identical (10 infections) or differing by only a single synonymous substitution (1 infection).…”

Are islands the end of the colonization road?

“…Cases of island populations losing their fear of predators or their defenses against introduced diseases (e.g. malaria in the Hawaiian avifauna [27,28]) have been well documented. As in the case of reduced dispersal ability, if defenses diminish over evolutionary time, the window of opportunity for island-to-continent colonization might be narrow.…”

Review on Culex quinquefasciatus: Southern House Mosquito

“…From the public health standpoint the importance of Southern House Mosquito, Culex quinquefasciatus as a mosquito vector relies on the fact that it is the principal vector of bancroftian filariasis and a potential vector of Dirofilaria immitis. It is also a competent vector of several arboviruses like West Nile virus (WNV) in north eastern United States and Asia [12][13] St. Louis encephalitis virus (SLEV) in eastern and south-central North America, Rift Valley fever virus, and several protozoa like Plasmodium relictum that causes bird malaria [14] .…”