Antigenic and Genetic Characterization of an Avian Poxvirus Isolated from an Endangered Hawaiian Goose (Branta sandvicensis)

MORTALITY PATTERNS IN ENDANGERED HAWAIIAN GEESE (NENE; BRANTA SANDVICENSIS)

Understanding causes of death can aid management and recovery of endangered bird populations. Toward those ends, we systematically examined 300 carcasses of endangered Hawaiian Geese (Nene; Branta sandvicensis) from Hawaii, Maui, Molokai, and Kauai between 1992 and 2013. The most common cause of death was emaciation, followed by trauma (vehicular strikes and predation), and infectious/inflammatory diseases of which toxoplasmosis (infection with Toxoplasma gondii) predominated. Toxicoses were less common and were dominated by lead poisoning or botulism. For captive birds, inflammatory conditions predominated, whereas emaciation, trauma, and inflammation were common in free-ranging birds. Mortality patterns were similar for males and females. Trauma predominated for adults, whereas emaciation was more common for goslings. Causes of death varied among islands, with trauma dominating on Molokai, emaciation and inflammation on Kauai, emaciation on Hawaii, and inflammation and trauma on Maui. Understanding habitat or genetic-related factors that predispose Nene (particularly goslings) to emaciation might reduce the impact of this finding. In addition, trauma and infection with T. gondii are human-related problems that may be attenuated if effectively managed (e.g., road signs, enforcement of speed limits, feral cat [Felis catus] control). Such management actions might serve to enhance recovery of this endangered species.

Reversion to virulence and efficacy of an attenuated Canarypox vaccine in Hawai'i 'Amakihi (Hemignathus virens)

Vaccines may be effective tools for protecting small populations of highly susceptible endangered, captive-reared, or translocated Hawaiian honeycreepers from introduced Avipoxvirus, but their efficacy has not been evaluated. An attenuated Canarypox vaccine that is genetically similar to one of two passerine Avipoxvirus isolates from Hawai'i and distinct from Fowlpox was tested to evaluate whether Hawai'i 'Amakihi (Hemignathus virens) can be protected from wild isolates of Avipoxvirus from the Hawaiian Islands. Thirty-one (31) Hawai'i 'Amakihi were collected from high-elevation habitats on Mauna Kea Volcano, where pox transmission is rare, and randomly divided into two groups. One group was vaccinated with Poximune C, whereas the other group received a sham vaccination with sterile water. Four of 15 (27%) vaccinated birds developed life-threatening disseminated lesions or lesions of unusually long duration, whereas one bird never developed a vaccine-associated lesion or "take." After vaccine lesions healed, vaccinated birds were randomly divided into three groups of five and challenged with either a wild isolate of Fowlpox (FP) from Hawai'i, a Hawai'i 'Amakihi isolate of a Canarypox-like virus (PV1), or a Hawai'i 'Amakihi isolate of a related, but distinct, passerine Avipoxvirus (PV2). Similarly, three random groups of five unvaccinated 'Amakihi were challenged with the same virus isolates. Vaccinated and unvaccinated 'Amakihi challenged with FP had transient infections with no clinical signs of infection. Mortality in vaccinated 'Amakihi challenged with PV1 and PV2 ranged from 0% (0/5) for PV1 to 60% (3/5) for PV2. Mortality in unvaccinated 'Amakihi ranged from 40% (2/5) for PV1 to 100% (5/5) for PV2. Although the vaccine provided some protection against PV1, both potential for vaccine reversion and low efficacy against PV2 preclude its use in captive or wild honeycreepers.

The phylogenetic analysis of avipoxvirus in New Zealand

Avipoxvirus is known to be endemic in New Zealand and it is a cause of ongoing mortalities in the endangered black robin and shore plover populations. There is no information on the strains of avipoxvirus occurring in New Zealand and their likely origin or pathogenicity. This study was designed to identify the phylogenetic relationships of pathogenic avipoxvirus strains infecting introduced, native, and endemic bird species in New Zealand. Avipoxvirus 4b core protein gene was detected in tissue samples from 25/48 birds (52.1%) from 15 different species in New Zealand. Bootstrap analysis of avipoxvirus 4b core protein gene revealed that the New Zealand avipoxvirus isolates comprised of three different subclades. The majority of New Zealand avipoxvirus isolates (74%) belonged to A1 subclade which shared 100% genetic similarity with the fowlpox HPB strain. An isolate from a wood-pigeon (kereru) belonged to subclade A3, displaying 100% sequence homology to albatrosspox virus. An additional group, isolated from two shore plovers and one South Island saddleback, grouped within subclade B1 and presented 99% sequence homology to European PM33/2007 and Hawaiian HAAM 22.10H8 isolates. The results suggest that a variety of New Zealand bird species are susceptible to avipoxvirus infection, that there are more than two distinctive avipoxvirus subclades in New Zealand, and that the most prevalent A1 strain may have been introduced to New Zealand through introduced avian hosts such as passerines or poultry.

Molecular characterization of a poxvirus isolated from an American flamingo (Phoeniconais ruber rubber)

An avian poxvirus from the beak scab of an American flamingo (Phoeniconais ruber rubber) was isolated by inoculation on the chorioallantoic membrane (CAM) of specific-pathogen-free (SPF) chicken embryos. The virus produced multifocal areas of epithelial hyperplasia along with foci of inflammation in the CAM, and rare cells contained small eosinophilic intracytoplasmic bodies. Chickens inoculated with the isolated virus in the feather follicle of the leg did not develop significant lesions. Nucleotide sequence comparison of a PCR-amplified 4.5 kb HindIII fragment of the genome of flamingo poxvirus (FlPV) revealed very high homology (99.7%) with condor poxvirus (CPV), followed by approximately 92% similarity with canary poxvirus (CNPV) and Hawaiian goose poxvirus (HGPV), but less similarity (approximately 69%) to fowl poxvirus (FPV), the type species of the genus Avipoxvirus of family Poxviridae. As in the cases with CPV, CNPV, and HGPV, genetic analysis of FlPV revealed an absence of three corresponding FPV open reading frames (ORF199, 200, and 202) and an absence of any reticuloendotheliosis virus (REV) sequences in this region. There are only nine nucleotide substitutions observed between FlPV and CPV in the 4.5 kb fragment; those were clustered in the ORF201 region, which in FPV genome is a site for integration of REV sequences. Phylogenetic analysis of the predicted amino acid sequences of the ORF201-coded hypothetical protein demonstrated FlPV to be more closely related to CPV, as well as to CNPV and HGPV, than to FPV.

Avipoxvirus infection in a collection of captive stone curlews (Burhinus oedicnemus)

A natural outbreak of avipoxvirus occurred in recently purchased stone curlews (Burhinus oedicnemus) at a breeding farm and subsequently spread to other stone curlews residing at the farm. The initial outbreak was characterized by mild vesicular skin lesions on the legs, which then developed crusts and bled. The overall morbidity rate was 100%, but none of the birds died, and all recovered without complication. Four gallinaceous species, also kept on the farm, did not develop lesions. Avipoxvirus was identified from the skin lesions by virus isolation, electron microscopy, and monoclonal antibody testing, as well as by polymerase chain reaction testing. Eight months after this outbreak, 7 male stone curlews developed large, round, crusty lesions on their legs. Although poxvirus virions were identified in the lesions, results of virus isolation were negative. These lesions possibly were the result of a recrudescence of the original infection in male birds that were stressed because they were housed together during the breeding season. This is the first clinical description of an avipoxvirus infection in stone curlews.

Evaluation of pathogenicity of avian poxvirus isolates from endangered Hawaiian wild birds in chickens

Pathogenicity of two avian poxviruses isolated from endangered Hawaiian wild birds, the Hawaiian Goose and the Palila, was compared with fowl poxvirus in chickens. Immune responses were measured by ELISA pre- and postimmunization with Hawaiian poxviruses and after challenge with fowl poxvirus. Both isolates from Hawaiian birds developed only a localized lesion of short duration at the site of inoculation in specific-pathogen-free chickens and did not provide protection against subsequent challenge with virulent fowl poxvirus. On the other hand, birds inoculated with virulent fowl poxvirus developed severe lesions. In contrast to high antibody response in chickens immunized with fowl poxvirus, birds immunized with either of the two Hawaiian isolates developed low to moderate antibody responses against viral antigens. The level of immune responses, however, increased in birds of all groups following subsequent challenge.