Morphologic Observations and Novel 18S rRNA Sequences of Abbreviata hastaspicula and Abbreviata antarctica from Varanus spp. Lizards in Australia.

The nematodes Abbreviata antarctica von Linstow, 1899, and Abbreviata hastaspicula Jones, 1979 , are predominant spirurid nematodes in species of Varanus lizards in Australia. However, genetic knowledge of these two species of nematode is lacking. In this study, nematodes removed from Varanus gouldii were examined using integrated morphologic and molecular methods. We extracted DNA from A. hastaspicula and A. antarctica for PCR and sequencing. Specific 18S small subunit ribosomal RNA (rRNA) primers were designed on the basis of existing 18S rRNA sequences of Physalopterinae strains. Species of Abbreviata, which are closely similar morphologically, may be misidentified, especially the larvae of different species of Abbreviata that cannot be differentiated. The findings of this study will improve the accuracy in identification of A. hastaspicula and A. antarctica, both morphologically and molecularly.

Experimental habitat fragmentation disrupts nematode infections in Australian skinks.

Habitat conversion and fragmentation threaten biodiversity and disrupt species interactions. While parasites are recognized as ecologically important, the impacts of fragmentation on parasitism are poorly understood relative to other species interactions. This lack of understanding is in part due to confounding landscape factors that accompany fragmentation. Fragmentation experiments provide the opportunity to fill this knowledge gap by mechanistically testing how fragmentation affects parasitism while controlling landscape factors. In a large-scale, long-term experiment, we asked how fragmentation affects a host-parasite interaction between a skink and a parasitic nematode, which is trophically transmitted via a terrestrial amphipod intermediate host. We expected that previously observed amphipod declines resulting from fragmentation would result in decreased transmission of nematodes to skinks. In agreement, we found that nematodes were absent among skinks in the cleared matrix and that infections in fragments were about one quarter of those in continuous forest. Amphipods found in gut contents of skinks and collected from pitfall traps mirrored this pattern. A structural equation model supported the expectation that fragmentation disrupted this interaction by altering the abundance of amphipods and suggested that other variables are likely also important in mediating this effect. These findings advance understanding of how landscape change affects parasitism.

Wild cane toads (Rhinella marina) expel foreign matter from the coelom via the urinary bladder in response to internal injury, endoparasites and disease.

Dissections of >1,200 wild-caught cane toads (Rhinella marina) in tropical Australia confirm a laboratory report that anurans can expel foreign objects from the coelom by incorporating them into the urinary bladder. The foreign objects that we found inside bladders included a diverse array of items (e.g., grass seeds, twigs, insect prey, parasites), many of which may have entered the coelom via rupture of the gut wall. In some cases, the urinary bladder was fused to other organs including liver, fat bodies, ovaries, Bidder's organs, lungs, mesentery, stomach wall, gall bladder, and the abdominal wall. Acanthocephalan parasites (of a range of developmental stages) were identified from the walls of the urinary bladders of three cane toads. This organ may play a significant role in destroying or excreting metazoan parasites, as well as inanimate objects.

Nematode larvae (order Spirurida) in gastric tissues of Australian anurans: a comparison between the introduced cane toad and sympatric native frogs.

The outcomes of host-parasite interactions depend heavily on the host's immune response, which, in turn, is governed by previous interactions between the host and parasite, both over the host's life time and over evolutionary time. In the case of species introductions, such as the cane toad (Bufo marinus) to Australia, parasites that are benign to native species of the introduced range may present a major challenge to the introduced species. Stomachs of introduced cane toads and seven species of sympatric native frogs were examined for parasites, and their pathology and biology were compared. Cane toads were host to eight species of third-stage spirurid larvae, six of which also occurred in the stomach wall of four native frog species. In general, encysted nematode larvae attained higher prevalence and species richness in introduced cane toads than in sympatric native frogs. This trend was largely explained by differences in body sizes: larger anurans were more likely to possess infections, and cane toads are inherently larger than native frogs. Encysted larvae in cane toad stomachs provoked a marked pathologic response. All larvae (physalopterine and Physocephalus spp.) were surrounded by concentric layers of dense, fibrous tissue, with considerable cellular infiltration characterized by lymphocytes and polymorphs. Many cysts were invaded by cells and exudate, which, in more advanced cases, became calcified. Some larvae appeared viable; most were in various stages of destruction, and some smaller Physocephalus spp. were mummified. Conversely, pathologic response observed in native frogs was minimal, with little fibrotic reaction surrounding the cysts, and no cellular infiltration. Presumably, the contrast in pathology between introduced and native hosts reflects the long evolutionary association between these nematode larvae and native frogs, whereas the recent exposure of introduced toads to these helminths provokes a severe reaction.

Microfilariae in Galápagos penguins (Spheniscus mendiculus) and flightless cormorants (Phalacrocorax harrisi): genetics, morphology, and prevalence.

Galapagos penguins (Spheniscus mendiculus) and flightless cormorants (Phalacrocorax harrisi) live in small, isolated populations on the westernmost islands of Isabela and Fernandina in the Galápagos Islands, Ecuador. Between August 2003 and February 2005, 4 field trips, 2 in the cool, dry season (August 2003 and August 2004) and 2 in the hot, rainy season (March 2004 and February 2005), were undertaken; 298 Galápagos penguins and 380 cormorants were sampled for prevalence and intensity of hemoparasites. Microfilariae were found in both the penguins and the cormorants. Blood smears were negative for the presence of other species of hemoparasites. Overall prevalence of microfilariae across seasons was 42.0% in cormorants and 13.8% in the penguins. Intensity of infection was generally low (mean = 3.2-31.7 in 25 fields across seasons and species) with the exception of a few individuals with markedly high intensities of parasites (>300 in 25 fields in 1 cormorant). Prevalence of microfilariae increased significantly over the 4 sampling periods for cormorants, but not for penguins. Prevalences were significantly higher in cormorants than in penguins for 3 of the 4 collecting trips. Male penguins had higher prevalences than females; however, there were no gender differences in cormorants. No relation was detected between body mass and either presence or intensity of parasitism. Morphological characteristics of the microfilariae are also described and specimens from each host species were similar in all characters measured. DNA sequence data from the mitochondrial cytochrome c oxidase subunit I gene were consistent with the morphological evidence and together demonstrate that the penguins and cormorants are likely to be infected with the same species of microfilariae.

Dracunculus mulbus n. sp. (Nematoda: Spirurida) from the water python Liasis fuscus (Serpentes: Boidae) in northern Australia.

A new species of Dracunculus Reichard, 1759 (Nematoda: Spirurida) is described from the tissues surrounding organs in the body-cavity of the water python Liasis fuscus Peters in northern Australia. One to 14 worms were recovered from 22% (27/120) of pythons examined. Males were located principally around the lungs, liver and heart of the hosts, and females were recovered from peritoneal tissue surrounding the intestines and lining the body-cavity. This species differs from previously described species of Dracunculus in the position of the papillae at the posterior end in males, and in the possession of thick, narrow caudal alae. Submedian cephalic papillae are single in both sexes. Dorsal and ventral anterior cephalic papillae are absent in males. This is the first report of a species of Dracunculus from the Australian region.

Molecular evidence for host specificity of parasitic nematode microfilariae in some African rainforest birds.

Here we describe, determine the prevalence, and examine the host-specificity of some parasitic nematode microfilariae in selected bird species from West and Central Africa. We used microscopy to determine the prevalence of microfilariae in 969 host individuals representing 121 rainforest bird species from Cameroon, Côte d'Ivoire and Equatorial Guinea. Thirteen (11%) of these potential host species harboured microfilariae, and 35 individuals (3.6%) were infected. From the 35 infected individuals, we identified eight distinct morphological microfilarial forms. Sixteen of the 35 infected individuals were of one host species, the Fire-crested Alethe (Alethe diademata), at a prevalence rate of 62%. To examine host and geographical specificity, we sequenced a portion of the LSU rDNA gene from representative microfilariae drawn from different hosts and collecting locations. Identical sequences of the nematode LSU rDNA gene were found in A. diademata collected from locations in Côte d'Ivoire and Equatorial Guinea, locations separated by the Dahomey Gap and associated with different hypothesized refugial areas. In contrast, several other bird species collected at the same sites harboured different microfilaria lineages. We sequenced the mitochondrial ATP synthase genes of the host species A. diademata, and found a 5.4% sequence divergence between the birds sampled in Côte d'Ivoire, and those from Cameroon. Thus, despite this split between the two populations, they harbour microfilariae with identical lineages. These data provide evidence that the microfilariae found in A. diademata may be highly host specific. This apparent specificity may have important implications for the evolutionary and ecological interactions between parasitic nematodes and their avian hosts.

Leucocytozoon (Apicomplexa: Leucocytozoidae) from West African birds, with descriptions of two species.

Five species of Leucocytozoon were recovered from 35/828 birds of 95 species examined from 6 sites in West Africa between May 1995 and June 2001. Leucocytozoon pogoniuli n. sp. is described from the tinker barbets Pogoniulus subsulphureus and Pogoniulus atroflavus. Leucocytozoon trachyphoni n. sp. is described from the barbet Trachyphonus purpureus. No leucocytozoids have been reported previously in species of Pogoniulus. Leucocytozoon nectariniae was identified from the sunbird Nectarinia olivacea, and Leucocytozoon brimonti was recovered from 4 species of Pycnonotidae (bulbuls), all of which are new host records. We also report the first Leucocytozoon to be recovered from the phylogenetically isolated bird, Picathartes sp. (Picathartidae). This parasite is similar in appearance to Leucocytozoon sakharoffi, and probably represents a previously undescribed species. In view of the intraspecific variability and, frequently, relatively minor interspecific differences within Leucocytozoidae, we suggest that the development and application of molecular techniques would greatly advance understanding of speciation and relationships within this family.

Blood parasites of some West African rainforest birds.

A total of 969 birds representing 121 species of 21 families from the West African nations of Cameroon, Equatorial Guinea and Ivory Coast were examined for haematozoa using thin blood smears; 277 individuals (28.6%) harbored blood parasites. The parasites identified included species of Haemoproteus (7.7% prevalence), Plasmodium (10.7%), Leucocytozoon (4.6%), and Trypanosoma (7.3%). In addition, microfilariae of filariid nematodes were present in 3.6% of the individuals examined. The birds were collected over a period of 12 years, from 1989-2001, from rainforest and ecotone habitats. We report a relatively high prevalence of parasites in colonial nesting birds, and two species of ground nesting birds. In addition, we compared data from bird species collected at a site identical to a previously published study, and did not find significant differences in parasite prevalence between the two years constituting two different seasons. Our results are also compared to other studies in Africa that implement similar and different methodologies.

A comparative analysis of PCR-based detection methods for avian malaria.

Here, 4 polymerase chain reaction (PCR) assays are compared to test for the presence of avian malaria, including both the Plasmodium and Haemoproteus genera, in 29 different species of African rainforest birds. Two of these PCR assays use primer sets that amplify fragments of the cytochrome b (cyt b) gene of Plasmodium; the other 2 target the 18S ribosomal subunit gene. These PCR assays were performed using genomic DNA extracted from blood and subsequently compared with the results obtained by microscopic examination of blood smears taken from the same individuals. The 2 primer sets amplifying the cyt b gene were found to perform more reliably than those that target the 18S rRNA gene and yielded a substantial number of positive samples that were undetected by blood smear analysis. Of all the individuals screened by PCR, 40% tested positive for avian malaria, whereas 27% tested positive by blood smear analysis. Although sequence variation in the parasites may prohibit the specific alignment of primers and the subsequent PCR amplification of some individuals, PCR, once optimized, is faster, cheaper, and more reliable than blood smear analysis for large-scale screening.

Survey of South Polar skuas (Catharacta maccormicki) for blood parasites in the Vestfold Hills region of Antarctica.

Thin blood smears prepared from 125 South Polar skuas (Catharacta maccormicki) at breeding islands and feeding sites in the Vestfold Hills region of Antarctica between December 1999 and January 2000 did not contain hematozoa. These findings confirm results of previous smaller studies, and provide baseline data for this species.