Are captive birds at the Auckland Zoo at risk of avian malaria infections?

Abstract

This study provides new information about the risk of avian malaria infection to captive birds at the Auckland Zoological Park, based upon surveys of likely vectors and thin blood smears from Auckland birds. A survey of mosquito larvae and adults at the Auckland Zoo revealed a mosquito fauna dominated by two exotic species; Culex quinquefasciatus, known to be a competent vector of invasive avian malaria parasites, and Aedes notoscriptus. This dominance by exotic mosquito species indicates the replacement of a native mosquito, Culex pervigilans, a species previously widespread within the site in a 2003 survey. The only other mosquito collected in this survey were two native Cx. asteliae larvae, a species previously only found in phytotelmata habitats within or directly adjacent to mature native forest. This finding is the first recording of this species within an urban habitat not immediately adjacent to large, mature native forest. Interestingly, the Cx. quinquefasciatus larvae displayed a great deal of morphological variation. Only 3/9 characters were highly consistent; each observed in >90% of larvae, when visible. Details of this variability is presented to aid future identification of this species within the region. Thin blood smears (n= 148) from 13 introduced, 5 native, and 6 endemic bird species collected from the Auckland region were examined for avian malaria parasites. An overall low Plasmodium spp prevalence was found (11%). Four bird species (three introduced, and one endemic) were infected, but only the blackbirds (Turdus merula) showed a high infection rate of 53%. Three subgenera of Plasmodium were identified; P. (Haemamoeba) sp., P. (Huffia) elongatum, and P. (Novyella) vaughani, all of which have been reported as relatively common in introduced birds in New Zealand. One Plasmodium sp. observed in the endemic tui (Prosthemadera novaeseelandiae) has not been fully characterised. These results in combination with previous work demonstrate a minimum of 5 introduced and 3 native or endemic common species living wild within the Auckland Zoo are potential reservoirs for avian malaria parasites. Therefore, these data suggests that captive birds at the zoo are at a high on-going risk of exposure to avian malaria. Recommendations for management strategies are provided to target the numerous artificial mosquito breeding habitats within the Auckland Zoo to reduce the likelihood of Plasmodium sp. transmission.