Hugh I. Jones

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.

Host specificity and incidence of Trypanosoma in some African rainforest birds: a molecular approach

Studies of host–parasite interactions in birds have contributed greatly to our understanding of the evolution and ecology of disease. Here we employ molecular techniques to determine the incidence and study the host‐specificity of parasitic trypanosomes in the African avifauna. We developed a polymerase chain reaction (PCR)‐based diagnostic test that amplified the small subunit ribosomal RNA gene (SSU rRNA) of Trypanosoma from avian blood samples. This nested PCR assay complements and corroborates information obtained by the traditional method of blood smear analysis. The test was used to describe the incidence of trypanosomes in 479 host individuals representing 71 rainforest bird species from Cameroon, the Ivory Coast and Equatorial Guinea. Forty‐two (59%) of these potential host species harboured trypanosomes and 189 individuals (35%) were infected. To examine host and geographical specificity, we examined the morphology and sequenced a portion of the SSU rRNA gene from representative trypanosomes drawn from different hosts and collecting locations. In traditional blood smear analyses we identified two trypanosome morphospecies, T. avium and T. everetti. Our molecular and morphological results were congruent in that these two morphospecies had highly divergent SSU rRNA sequences, but the molecular assay also identified cryptic variation in T. avium, in which we found seven closely allied haplotypes. The pattern of sequence diversity within T. avium provides evidence for widespread trypanosome mixing across avian host taxa and across geographical locations. For example, T. avium lineages with identical haplotypes infected birds from different families, whereas single host species were infected by T. avium lineages with different haplotypes. Furthermore, some conspecific hosts from geographically distant sampling locations were infected with the same trypanosome lineage, but other individuals from those locations harboured different trypanosome lineages. This apparent lack of host or geographical specificity may have important consequences for the evolutionary and ecological interactions between parasitic trypanosomes and their avian hosts.

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.

Microfilariae in GaláPagos penguins (Spheniscus mendiculus) and flightless cormorants (Phalacrocorax harrisi): Genetics, morphology, and prevalence

Galápagos 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.

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 hosts immune response, which, in turn, is governed by previous interactions between the host and parasite, both over the hosts 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.

Notes on Parasites in Penguins (Spheniscidae) and Petrels (Procellariidae) in the Antarctic and Sub-antarctic

Blood smears were examined from 143 penguins of four species (Aptenodytes patagonicus, Eudyptes chrysolophus, E. schlegeli, and Pygoscelis gentoo) from Sub-antarctic Macquarie Island and Heard Island. No blood parasites were reported. The vectors of Hepatozoon albatrossi (reported from three species of albatross) are probably shared by penguins, and it is suggested that the latter are not susceptible to infection with this protozoan. Cestodes of the genus Tetrabothrius were present in large numbers in the intestines of 17 Antarctic petrels (Thalassoica antarctica), and evidence is presented indicating that euphausiid crustaceans may be intermediate hosts.

HEMATOZOA FROM MONTANE FOREST BIRDS IN PAPUA NEW GUINEA

Blood smears were examined from 141 montane forest birds of 45 species in southeastern Papua New Guinea. Haemoproteus spp. occurred in 46 (32.6%), Leucocytozoon fringillinarum Woodcock, 1910 in five, Trypanosoma sp. in one and Haemogregarina sp. in one. Intensity of infection by Haemoproteus was highest in those avian species and families with the highest prevalence; increasing altitude had no demonstrable effect on the prevalence of Haemoproteus spp.

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.

Gastrointestinal Nematodes from Three Species of Australian Leaf-tailed Geckos (Reptilia: Saltuarius spp.), with Descriptions of New Species of Skrjabinodon (Oxyuroidea: Pharyngodonidae) and Hedruris (Habronematoidea: Hedruridae)

ABSTRACT:  Two new species of Skrjabinodon, Skrjabinodon barrinae n. sp. and Skrjabinodon swainii n. sp., are described from Australian leaf-tailed geckos (Gekkonidae: Saltuarius), and Skrjabinodon oedurae is redescribed from the Australian gecko Oedura robusta. They are distinguished from one another, and from Skrjabinodon poicilandri from a New Zealand gecko, Hoplodactylus maculatus, by length and proportions of the terminal tail filament and the number of spines thereon, the form of the male somatic alae, disposition of papillae at the base of the male tail, and the large excretory vesicle in S. oedurae. These 4 species of nematode possess 3 large distinctive pointed structures at the end of the female tail. Each is only known from a single host species, and they are all either geographically or ecologically isolated from one another. Hedruris saltuarii is the second species in this genus to be described from an Australian reptile; it differs from Hedruris longispicula, and from 5 other species of Hedr...

Gastrointestinal Helminths in Two Allopatric Sibling Species of Swamp Skink, Lissolepis coventryi and Lissolepis luctuosus (Reptilia: Scincidae) from Southeastern and Southwestern Australia, with Descriptions of Three New Species of Nematode

Abstract Two closely related species of swamp skink (Lissolepis coventryi and Lissolepis luctuosus) occur in Australia, one in the extreme southeast and the other in the southwest of the country. They are separated by more than 2,000 km of arid country, and they have been isolated from one another for a considerable period of time, possibly more than 20 million years. We investigated the gastrointestinal nematode fauna of each using preserved museum lizards. More than 80% of each species of lizard was infected with nematodes. Three new species of nematode are described; Spinicauda victoriae n. sp. occurs only in L. coventryi in the southeast and Spinicauda similis n. sp. only in L. luctuosus in the southwest, each occurring at a similar prevalence and intensity. Moaciria paucipapillata n. sp. occurs in both populations. Abbreviata antarctica also occurs in both populations, though infrequently in L. coventryi. Pseudorictularia disparilis was present in 14% of L. coventryi, attesting to the aquatic habitat this lizard. The close similarity of the two species of Spinicauda, which differ only in the form of the eggs, indicate a common ancestry. The presence of A. antarctica adults in these semi-aquatic hosts supports the suggestion that this morphologically variable species originated in a cool, damp environment and has adapted to a wider range of hosts and to a less-humid environment. The cestode Oochoristica vacuolata was recovered primarily from L. coventryi.