Avian Pathogens and Vectors - Kahuku Unit of Hawaii Volcanoes National Park

Science Center Objects

While the Hawaiian avian disease system has been well-studied in the forests of the older section of Hawai‘i Volcanoes National Park (HAVO), and in many other locations throughout the state, nothing was known about avian disease in the new Kahuku Unit of Hawai‘i Volcanoes National Park and the adjacent Kau Forest Reserve.  The high elevation forests of Kahuku are the only habitat located on National Park Service (NPS) lands where the federally listed endangered akiapōlāʻau, Hawai‘i ‘akepa, and Hawai‘i creeper still exist but distributions of native forest bird diversity and abundance in lower Kahuku suggest that avian disease might constrain existing populations and will hinder future attempts at restoration. The adjacent Ka‘u Forest Reserve is part of the broader forest landscape and critical habitat for a number of Kahuku species. Ka‘u Forest Reserve has also been identified by the U.S. Fish and Wildlife Service (USFWS) as a possible location for the restoration of the federally listed endangered Hawaiian crow or ʻalalā.

Overview:

Jackie Gaudioso covered in mud

Biologist Jackie Gaudioso-Levita displays the perils of fieldwork in Hawai‘i including non-stop rain and mud in the Ka‘u Forest Reserve. (Credit: Dennis LaPointe, USGS. Public domain.)

We collected information about the distribution and prevalence of avian disease and disease vectors to support HAVO resource management in their preservation and restoration of endangered forest bird species. Disease surveys in Kahuku were used to document the spread of emerging diseases like knemidokoptic mange and potential new vectors like Aedes japonicus. In the next decade, landscape-level convergence of environmental change associated with changing climate, invasive species, residential development adjacent to the park, and the introduction of new pathogens and vectors will likely intensify the impact of avian disease on forest birds in Kahuku. To address these growing threats, monitor future trends in disease, and support development of strategies for disease control, managers will need baseline and updated data on the prevalence of pathogens, distribution of vectors, and comparative studies on the factors influencing the abundance of vectors. Field studies on mosquito-borne disease also maintain capacity for rapid response to zoonotic disease such as West Nile virus.

Project Objectives:

Dennis LaPointe collects a blood sample from a forest bird

Dr. Dennis LaPointe collects a blood sample from a Hawai‘i ‘amakihi. Photo: D. LaPointe (Public domain.)

The main goal of the project was to provide resource managers at Hawai‘i Volcanoes National Park and endangered species biologists at Pacific Islands U.S. Fish and Wildlife Service Office with baseline data on the occurrence of disease vectors and prevalence of avian disease in the Kahuku Unit and the adjacent Ka‘u Forest Reserve. This information should support efforts to limit disease transmission and foster preservation and restoration of endemic Hawaiian forest birds such as ‘akiapōlā‘au, ‘akepa, ‘alalā and Hawai‘i creeper. Ongoing studies on mosquito-borne avian disease also maintains capacity for rapid response to zoonotic disease such as West Nile virus in the Pacific.  Specific objectives were to 1) determine the status of adult mosquito populations and map larval mosquito habitat across an altitudinal and habitat gradient in the Kahuku Unit and nearby Ka‘u Forest 2) determine the prevalence of avian disease (avian malaria, avian pox, and knemidokoptic mange) across altitudinal and habitat gradients in the Kahuku Unit and nearby Ka‘u Forest and 3) identify environmental determinants of disease prevalence.

Mosquito trap

Mosquito trap set up to collect adult mosquitoes. Photo: D. LaPointe (Public domain.)

Highlights and Key Findings: 

In 2013, we detected the emerging avian disease knemidokoptic mange in Hawai‘i ‘amakihi inhabiting the Kahuku Ranch unit of Hawai‘i Volcanoes National Park.  We found infested birds at sites located at 1200 m above sea level (asl) and 1500 m asl. These observations provide further evidence of the geographical and altitudinal spread of this disease. We also captured adult Culex quinquefasciatus at our 1200 m asl site.  Adults mosquitoes were present in late summer (October) and were infected with the avian malaria Plasmodium relictum at 20% prevalence. An adult Aedes japonicus was captured in August 2014 at our highest site at 1900 m asl. This is the highest elevation where we have detected Aedes japonicus, a recently introduced mosquito from temperate Asia. No other mosquitoes were captured in our Kahuku Ranch sites despite 100+ trap-nights of effort conducted throughout the year. We captured over 500 birds and completed molecular diagnostics on 570+ blood samples.

Progress: 

This project was completed in 2016. The final report is now available.