Experiments by researchers at UH Hilo show great promise in clearing the way for new vaccines to be used in the fight against this rapidly spreading disease

Endangered native bird populations in Hawai‘i have extremely limited immunity to imported diseases. Scientists suspect that avian malaria and avian pox, both recent imports, have played a large role in the decline and extinction of a variety of species of endemic forest birds. A small number of Hawaiian species have evolved some degree of immunity to malaria, but most have not. West Nile Virus (WNV), which has yet to arrive in Hawai‘i, could prove even more devastating to Hawai‘i’s birds. The virus has spread rapidly through South and Central American avian populations in recent years, killing millions of birds. To date scientists have recorded WNV infections in nearly 300 bird species. The appearance of WNV is a virtual certainty, given the quantity of wild birds that stop in Hawai‘i while migrating from other locales.

Bird researchers in Hawai‘i fear that, left unchecked, WNV could quickly eliminate the small remaining populations of native birds such as the ‘Alala‚ (Hawaiian crow) and the Nēnē (Hawaiian goose). A zoo in Hawai‘i and several on the mainland have used an existing West Nile Virus vaccine to inoculate bird populations. Called the Fort Dodge Vaccine, this vaccine was originally developed to protect horses from the virus. The Fort Dodge version uses live organisms that have been sufficiently weakened to induce immune response without causing disease symptoms or full-blown infection. Significant adverse side-effects to the Fort Dodge vaccine have been reported in bird populations, with some reports of deaths associated with vaccination. For an endangered bird population, using an unproven vaccine represents an unacceptable risk.

Over the past year, University of Hawai‘i at Hilo researcher Susan Jarvi has led a collaborative project to test a WNV vaccine developed for humans on avian populations. Honolulu biotechnology firm Hawaii Biotech Inc. developed the vaccine and helped fund this study. The HBI vaccine uses copies of a small fragment of protein found on the exterior shell of WNV to trick the immune system into responding and developing immunological protection. Jarvi suspects that this version, which uses no live viruses, could prove safer for endangered birds, and possibly for all birds. In the summer of 2005, Jarvi began an experiment with the vaccine in collaboration with other researchers from UH Hilo, UH Mānoa, the U.S. Geological Survey’s National Wildlife Health Center in Madison, Wis., Pacific Islands Ecosystems Research Center in Hawai‘i Volcanoes National Park, the National Park Service, and local veterinarians from the East Hawai‘i Veterinary Clinic and the Pet Hospital.

In the first phase of experiments, which concluded in August, 2006, Jarvi tested the human WNV vaccine on dozens of 21-day-old domestic geese. Roughly half of the goslings were then injected at 90 days of age with live WNV at a biologically secure research facility in Madison. The results showed that the vaccinated birds had higher antibody responses and lower virus counts than the non-vaccinated groups. Most importantly, none of the geese showed any adverse effects due to exposure to the vaccine. This appears to be a safe and effective vaccine in domestic geese.

Jarvi and her team hope that these initial positive findings will allow them within the next year to proceed with testing the Hawai‘i Biotech WNV vaccine on captive, non-breeding populations of rare Hawaiian birds, in order to measure side effects. “Transmission is key to the spread of any disease. The use of vaccines minimizes transmission. Vaccinating our birds will not only help to save our unique native species, it will also help to minimize the impact the disease has on people of Hawai‘i,” explains Jarvi.

Ultimately, Jarvi hopes the vaccine can be used on populations of birds intended to be released into the wild. Beyond Hawai‘i, the provision of a safe WNV vaccine with minimal side-effects could make it far easier for global health authorities to convince suspicious farmers to vaccinate large flocks of domesticated birds (chickens, geese and ducks). That, in turn, could prove to be a significant step in preventing WNV outbreaks in humans in the future if the virus mutates and, potentially, becomes more virulent.

Susan Jarvi is an associate professor of biology at the University of Hawai‘i at Hilo. She specializes in evolutionary genetics of native Hawaiian birds and avian pathogens in the Hawaiian rainforest. She is also a co-principal investigator on a National Science Foundation project on the Biocomplexity of Introduced Diseases in Hawai‘i.

   Photo: Sam Kim