Laboratory and field experiments were conducted on the island of Hawaii from 1977- 1980 in an effort to determine the impact of avian malaria on the forest birds. At 16 study sites from sea level to tree line in mesic and xeric habitat, birds were captured and bled to determine the host and altitudinal distribution of blood parasites. In the laboratory, six bird species were challenged with malarial parasites to measure host susceptibility. Distributions, activity cycles, and transmission po- tentials of malarial parasite vectors were also analyzed. One species of Plasmodium was present from sea level to tree line, concentrated in the mid- elevational ranges in the ecotonal area where vectors and native birds had the greatest overlap. Native forest birds were: (a) more susceptible to malaria than were introduced species; (b) most likely to have malaria during the nonbreeding, wet season; (c) found ranging lower in xeric than in mesic forests; and (d) found to have a lower prevalence of malaria in xeric forests. Temporal as well as elevational differences in prevalence and parasitemia levels of wild birds were apparent throughout the annual cycle, a result of differing host and parasite responses to biotic and abiotic factors. Avian malaria probably did not reach epizootic proportions on Hawaii until after z 1920. However, since that time it has had a negative impact on the population dynamics of the native forest birds and is today a major limiting factor, restricting both abundance and distribution of these species on the island. In response, a number of native bird species have developed immunogenetic and behavioral responses that reduce the impact of the parasite on host populations.

https://www.jstor.org/stable/pdfplus/1942550.pdf

The epizootiology and ecological significance of malaria in hawaiian land birds

We compared information obtained by both microscopy and nested mitochondrial cytochrome b PCR in determining prevalence of haemosporidian infections in naturally infected birds. Blood samples from 472 birds of 1 1 species belonging to 7 families and 4 orders were collected in Europe, Africa, and North America. Skilled investigators investigated them using the PCR-based screening and microscopic examination of stained blood films. The overall prevalence of haemosporidian infections, which was determined by combining results of both these methods, was 60%. Both methods slightly underestimated the overall prevalence of infection, which was 54.2% after the PCR diagnostics and 53.6% after microscopic examination. Importantly, both these tools showed similar prevalence for Haemoproteus spp. (21% by PCR and 22% by microscopy), Plasmodium spp. (17% and 22%), and Leucocytozoon spp. (30% and 25%), verifying that microscopy is a reliable tool in determining patterns of distribution of blood haemosporidian parasites in naturally infected birds. We encourage using optical microscopy in studies of blood parasites in parallel to the now widely employed molecular methods. Microscopy is unlikely to result in false positives, which is a major concern in large-scale PCR studies. Moreover, it is relatively inexpensive and provides valuable information regarding the ways in which molecular methods can be further improved and most effectively applied, especially in the field studies of parasites. Importantly, blood films, which are used for microscopic examination, should be of good quality; they should be examined properly by skilled investigators. In spite of the substantial time investments associated with microscopy, such examination provides opportunities for simultaneous determination and verification of taxonomically different parasites. Presently, different PCR protocols must be used for the detection of parasites belonging to different genera; this is expensive and time consuming.

https://www.jstor.org/stable/info/40059215

A comparative analysis of microscopy and pcr-based detection methods

We describe a polymerase chain reaction (PCR) assay that detects avian malarial infection across divergent host species and parasite lineages representing both Plasmodium spp. and Haemoproteus spp. The assay is based on nucleotide primers designed to amplify a 286-bp fragment of ribosomal RNA (rRNA) coding sequence within the 6-kb mitochondrial DNA malaria genome. The rRNA malarial assay outperformed other published PCR diagnostic methods for detecting avian infections. Our data demonstrate that the assay is sensitive to as few as 10−5 infected erythrocytes in peripheral blood. Results of avian population surveys conducted with the rRNA assay suggest that prevalences of malarial infection are higher than previously documented, and that studies based on microscopic examination of blood smears may substantially underestimate the extent of parasitism by these apicomplexans. Nonetheless, because these and other published primers miss small numbers of infections detected by other methods, including inspection ...

/pdf/detecting-avian-malaria-an-improved-polymerase-chain-53zlx4uy73.pdf

Detecting avian malaria: an improved polymerase chain reaction diagnostic

Numerous polymerase chain reaction (PCR)-based methods have been developed and used increasingly to screen vertebrate blood samples for the diagnosis of haemosporidian blood parasites (Sporozoa, Haemosporida), but a rigorous evaluation of the sensitivity of these methods for detecting mixed infections of different haemosporidian species belonging to the same and different genera and subgenera is lacking. This study links the information obtained by nested cytochrome b PCR and traditional microscopy in determining mixed haemosporidian infections in naturally infected birds. Samples from 83 individual passerine birds with single infections of Haemoproteus or Plasmodium spp., as determined by mitochondrial DNA amplification, also were investigated by microscopic examination of stained blood films. Thirty-six samples (43%) were found to harbor mixed Haemoproteus, or Plasmodium spp. infections, or both. Thus, the PCR assays alone underestimate the occurrence of mixed infections of haemosporidian parasites in naturally infected birds. To determine the true species composition of the haemosporidians in each individual host, PCR diagnostics need to be improved. Specific primers for Haemoproteus spp. and Plasmodium spp. should be developed. Ideally, a combination of the approaches of both microscopy and PCR-based methods is recommended for this purpose.

https://bioone.org/journals/Journal-of-Parasitology/volume-92/issue-2/GE-3547RN.1/Nested-Cytochrome-iB-i-Polymerase-Chain-Reaction-Diagnostics-Underestimate-Mixed/10.1645/GE-3547RN.1.pdf

Nested cytochrome B polymerase chain reaction diagnostics underestimate mixed infections of avian blood haemosporidian parasites: Microscopy is still essential

Tissue samples from 699 birds from three regions of Asia (Myanmar, India, and South Korea) were screened for evidence of infection by avian parasites in the genera Plasmodium and Haemoproteus. Samples were collected from November 1994 to October 2004. We identified 241 infected birds (34.0%). Base-on-sequence data for the cytochrome b gene from 221 positive samples, 34 distinct lineages of Plasmodium, and 41 of Haemoproteus were detected. Parasite diversity was highest in Myanmar followed by India and South Korea. Parasite prevalence differed among regions but not among host families. There were four lineages of Plasmodium and one of Haemoproteus shared between Myanmar and India and only one lineage of Plasmodium shared between Myanmar and South Korea. No lineages were shared between India and South Korea, although an equal number of distinct lineages were recovered from each region. Migratory birds in South Korea and India originate from two different migratory flyways; therefore cross-transmission of parasite lineages may be less likely. India and Myanmar shared more host species and habitat types compared to South Korea. Comparison between low-elevation habitat in India and Myanmar showed a difference in prevalence of haematozoans.

https://nsuworks.nova.edu/cgi/viewcontent.cgi?article=1989&context=cnso_bio_facarticles

Pilai Poonswad

Papers

Haematozoa in the Birds of Eastern and Southern Asia