University of Hawaiʻi at Hilo

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The University of Hawaiʻi at Hilo is a state university with a private college atmosphere. We offer small class sizes, a low faculty-to-student ratio and opportunities for research and hands-on learning.

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Browsing University of Hawaiʻi at Hilo by Author "Apelgren, Chloe"

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    Distribution and prevalence of knemidokoptic mange in Hawai`i `amakihi on the island of Hawai`i
    (2016-01-24) Gaudioso-Levita, Jaqueline; LaPointe, Dennis; Atkinson, Carter; Apelgren, Chloe
    Knemidokoptic mange was first observed on two Hawai‘i ‘Amakihi (Hemignathus virens) mist netted in Manuka Natural Area Reserve (NAR) on the Island of Hawai‘i in June 2007. Microscopic examination of skin scrapings from lesions of the infested individuals revealed the scaley-leg mite, Knemidokoptes jamaicensis. Continued surveillance at Manuka NAR (2007-2009) documented a 24% (15/63) prevalence of mange among Hawai‘i ‘Amakihi distributed from coastal habitat to 1,500 m above sea level (asl). From 2012-2014, we conducted an island-wide survey of wild passerine birds from several leeward sites (Manuka NAR, Kahuku Unit of Hawai‘i Volcanoes National Park (HAVO), Pu‘u Wa‘awa‘a Forest Bird Sanctuary, and Kipahoehoe NAR) and windward sites (Hakalau Forest National Wildlife Refuge, ‘Ᾱinahou Ranch of HAVO, Malama Ki Forest Reserve, and Keauohana Forest Reserve) to determine the current distribution and host range of knemidokoptic mange. We also determined the prevalence of malaria in Hawai‘i ‘Amakihi populations where mange was present and treated a subset of infested Hawai‘i ‘Amakihi mange with a single, topical dose of moxidectin. We mist netted and examined a total of 1,734 passerines, including 738 Hawai‘i ‘Amakihi. Mange was present in Hawai‘i ‘Amakihi at Manuka NAR (595 and 305 m asl), Kahuku Ranch Unit of HAVO (Glover site: 1,201 m asl and Kipuka Akala site: 1,532 m asl), Malama Ki Forest Reserve and Keauohana Forest Reserve (293 m asl). No other passerine birds (n = 995) were infected. Mange prevalence ranged from a high of 69% (40/58) in Keauohana Forest Reserve to a low of 2% (1/65) in the Kahuku Ranch Unit of HAVO (Kipuka Akala). At Manuka NAR prevalence had decreased from 26% in 2010 to 10% (7/81) in 2012–2014. We found no significant relationship between the prevalence of mange and the prevalence of avian malaria in mesic habitats at Manuka NAR (P = 0.59 (FET, n = 81)), but there was a significant association between the prevalence of mange and the prevalence of malaria in lowland wet forests in Puna Forest Reserves (P < 0.01 (FET, n = 72)). This apparent association may be a reflection of the high prevalence of malaria (>80%) in these areas. There was no difference in the frequency of recapture of birds that were infested versus un-infested at first capture at our long-term sites (Manuka NAR and Puna sites) (χ2(1, n = 227) = 1.51, P = 0.22, but when all sites with mange present were pooled, there was a significant difference in the frequency of recaptures between infested and un-infested birds (χ2(1, n = 424) = 7.13, P = 0.01). There was a significant association between parasitemia level (per 10,000 RBCs) and the ranked stage of mange present in infested individuals. We treated 24 Hawai‘i ‘Amakihi with moxidectin and upon recapture (n = 2), found a reduction in both the size and stage of mange lesions, such that a single dose, topical treatment of moxidectin appears to be an effective treatment for knemidokoptic mange in wild populations. Our results suggest that knemidokoptic mange is currently limited to Hawai‘i ‘Amakihi and prevalent in low elevation sites on both the windward and leeward sides of the island.
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    Effects of climate and land use on diversity, prevalence, and seasonal transmission of avian hematozoa in American Samoa
    (2016-01-25) Atkinson, Carter; Utzurrum, Ruth; Seamon, Joshua; Schmaedick, Mark; LaPointe, Dennis; Apelgren, Chloe; Egan, Ariel; Watcher-Weatherwax, William
    The indigenous forest birds of American Samoa are increasingly threatened by changing patterns of rainfall and temperature that are associated with climate change as well as environmental stressors associated with agricultural and urban development, invasive species, and new introductions of avian diseases and disease vectors. Long term changes in their distribution, diversity, and population sizes could have significant impacts on the ecological integrity of the islands because of their critical role as pollinators and seed dispersers. We documented diversity of vector borne parasites on Tutuila and Ta‘u Islands over a 10-year period to expand earlier observations of Plasmodium, Trypanosoma, and filarial parasites, to provide better parasite identifications, and to create a better baseline for detecting new parasite introductions. We also identified potential mosquito vectors of avian Plasmodium and Trypanosoma, determined whether land clearing and habitat alterations associated with subsistence farming within the National Park of American Samoa can influence parasite prevalence, and determined whether parasite prevalence is correlated with seasonal changes in rainfall, temperature and wind speed. Three taxonomically distinct lineages of Plasmodium were identified from mosquito vectors and forest birds based on partial sequence data from parasite mitochondrial genes. All three have been described from passerine and galliform birds in Australasia. Two lineages, SCEDEN01 and ORW1, had elongate gametocytes and large schizonts that were consistent with species of Plasmodium in the subgenus Giavannolaia, but were taxonomically distinct from known morphological species of Plasmodium based on a Bayesian phylogenetic analysis of a 478 bp region of the parasite cytochrome b gene. Both are candidates for description as new species. The third lineage (GALLUS02) was detected only in mosquito vectors on Tutuila and was similar in cytochrome b sequence to P. juxtanucleare, a pathogenic species of Plasmodium from chickens and other galliform birds from Australasia, Africa, and South America. Plasmodium relictum, the malarial parasite that has had such a devastating impact on Hawaiian forest birds, was not detected. We observed large, striated trypanosomes in avian hosts from both Tutuila and Ta‘u Islands that fell within the same taxonomic clade as T. corvi and T. culicavium based on 18S ribosomal DNA sequence. We also observed sheathed microfilariae with pointed tails that had some morphological similarities to microfilaria from species of Pelecitus, Struthiofilaria and Eulimdana, but identification will require recovery and examination of adult filarial worms from the connective tissue or body cavities of infected birds. We also observed one or more species of haemococcidians (Isospora, synonym = Atoxoplasma) within circulating lymphocytes from multiple avian host species. Overall prevalence of Plasmodium was higher on Ta‘u (22%, 75/341) than Tutuila (9.2%, 27/294), with most infections occurring in Polynesian starlings, Samoan starlings, Wattled honeyeaters, and Cardinal honeyeaters. Prevalence was relatively constant from year to year and between seasons at individual study sites, but varied among study sites, with highest rates of infection in areas with agricultural activity at Faleasao (37.4%, 73/195, Ta‘u Island) and Amalau Valley (9.7%, 21/216, Tutuila Island). Prevalence in more remote areas of the National Park of American Samoa was lower, ranging from 1.4% (2/146) at Laufuti and Luatele on Ta‘u to 7.7% (6/78) at Olo Ridge on Tutuila. Similar trends were evident for infections with Trypanosoma and filarial worms. Overall prevalence was not influenced significantly by warmer, wet (summer) or cooler, dry (winter) season. We detected Plasmodium infections in Culex sitiens and C. quinquefasciatus through either salivary gland and midgut dissections or PCR amplification of parasite cytochrome b genes in pooled or individual samples of mosquitoes that were collected on Tutuila. Pooled or individual Aedes oceanicus, A. polynesiensis, A. tutuilae, A. upolensis, A. nocturnus, Aedes (Finlaya) (mixed pools of A. samoanus, A. oceanicus, A. tutuilae), Aedes (Stegomyia) (mixed pools of A. aegypti, A. upolensis, A. polynesiensis), and C. annulirostris were negative for Plasmodium, but we detected infections with Trypanosoma through midgut and salivary gland dissections in a single C. sitiens from Amalau Valley, Tutuila and three A. oceanicus from Faleasao, Ta‘u. Two of the A. oceanicus from Faleasao amplified successfully with Trypanosoma primers, but sequences were distinctly different from those obtained from avian hosts. We found a strong association between land use and prevalence of mosquito-transmitted parasites on Ta‘u Island with odds of being infected more than 20 times greater in agricultural plots than more remote native forest. This relationship was evident on Tutuila Island but not statistically significant because of the close proximity of study sites and observed movement of birds between native forest and agricultural land. Our data support previous studies that have suggested that Plasmodium and other vector-borne parasites are part of the indigenous parasite fauna in American Samoa. Transmission dynamics appear to be affected by environmental changes associated with land use practices.