Clonal diversity of a malaria parasite, Plasmodium mexicanum, and its transmission success from its vertebrate-to-insect host

Infections of the lizard malaria parasite Plasmodium mexicanum are often genetically complex within their fence lizard host (Sceloporus occidentalis) harbouring two or more clones of parasite. The role of clonal diversity in transmission success was studied for P. mexicanum by feeding its sandfly vectors (Lutzomyia vexator and Lutzomyia stewarti) on experimentally infected lizards. Experimental infections consisted of one, two, three or more clones, assessed using three microsatellite markers. After 5days, vectors were dissected to assess infection status, oocyst burden and genetic composition of the oocysts. A high proportion (92%) of sandflies became infected and carried high oocyst burdens (mean of 56 oocysts) with no influence of clonal diversity on these two measures of transmission success. Gametocytemia was positively correlated with transmission success and the more common vector (L. vexator) developed more oocysts on midguts. A high proportion ( approximately 74%) of all alleles detected in the lizard blood was found in infected vectors. The relative proportion of clones within mixed infections, determined by peak heights on pherograms produced by the genetic analyser instrument, was very similar for the lizard's blood and infections in the vectors. These results demonstrate that P. mexicanum achieves high transmission success, with most clones making the transition from vertebrate-to-insect host, and thus explains in part the high genetic diversity of the parasite among all hosts at the study site.

Chimpanzee malaria parasites related to Plasmodium ovale in Africa

Since the 1970's, the diversity of Plasmodium parasites in African great apes has been neglected. Surprisingly, P. reichenowi, a chimpanzee parasite, is the only such parasite to have been molecularly characterized. This parasite is closely phylogenetically related to P. falciparum, the principal cause of the greatest malaria burden in humans. Studies of malaria parasites from anthropoid primates may provide relevant phylogenetic information, improving our understanding of the origin and evolutionary history of human malaria species. In this study, we screened 130 DNA samples from chimpanzees (Pan troglodytes) and gorillas (Gorilla gorilla) from Cameroon for Plasmodium infection, using cytochrome b molecular tools. Two chimpanzees from the subspecies Pan t. troglodytes presented single infections with Plasmodium strains molecularly related to the human malaria parasite P. ovale. These chimpanzee parasites and 13 human strains of P. ovale originated from a various sites in Africa and Asia were characterized using cytochrome b and cytochrome c oxidase 1 mitochondrial partial genes and nuclear ldh partial gene. Consistent with previous findings, two genetically distinct types of P. ovale, classical and variant, were observed in the human population from a variety of geographical locations. One chimpanzee Plasmodium strain was genetically identical, on all three markers tested, to variant P. ovale type. The other chimpanzee Plasmodium strain was different from P. ovale strains isolated from humans. This study provides the first evidence of possibility of natural cross-species exchange of P. ovale between humans and chimpanzees of the subspecies Pan t. troglodytes.

Effect of rutin and chloroquine on White Leghorn chickens infected with Plasmodium (Bennettinia) juxtanucleare

Plasmodium juxtanucleare is one of the agents that cause avian malaria in chickens and little is known about the treatment of the infection. The aim of this study was to compare the antimalarial activities of rutin and chloroquine in chickens infected with P. juxtanucleare after immunosuppression with corticosteroid. Antimalarial activity was verified in 33 fowls by evaluation of parasitemia levels in Giemsa-stained blood smears taken to 30 days. Rutin did not exert a reduction in parasitemia from P. juxtanucleare when compared to chloroquine treatment that kept the parasites at a low level, demonstrating its antimalarial effect. During the course of the infection, the trophozoite stage predominated (80%), followed by schizont (17%) and gametocyte (3%). Maximum parasitemia levels were recorded on day 12 in control and rutin groups. There were no significant differences in the hematocrit values, weight body or the temperature of the fowls among the groups evaluated (p > 0.05).

Natural Plasmodium infections in Brazilian wild monkeys: reservoirs for human infections?

Four hundred and forty-eight samples of total blood from wild monkeys living in areas where human autochthonous malaria cases have been reported were screened for the presence of Plasmodium using microscopy and PCR analysis. Samples came from the following distinct ecological areas of Brazil: Atlantic forest (N=140), semideciduous Atlantic forest (N=257) and Cerrado (a savannah-like habitat) (N=51). Thick and thin blood smears of each specimen were examined and Plasmodium infection was screened by multiplex polymerase chain reaction (multiplex PCR). The frequency of Plasmodium infections detected by PCR in Alouatta guariba clamitans in the São Paulo Atlantic forest was 11.3% or 8/71 (5.6% for Plasmodium malariae and 5.6% for Plasmodium vivax) and one specimen was positive for Plasmodium falciparum (1.4%); Callithrix sp. (N=30) and Cebus apella (N=39) specimens were negative by PCR tests. Microscopy analysis was negative for all specimens from the Atlantic forest. The positivity rate for Alouatta caraya from semideciduous Atlantic forest was 6.8% (16/235) in the PCR tests (5.5, 0.8 and 0.4% for P. malariae, P. falciparum and P. vivax, respectively), while C. apella specimens were negative. Parasitological examination of the samples using thick smears revealed Plasmodium sp. infections in only seven specimens, which had few parasites (3.0%). Monkeys from the Cerrado (a savannah-like habitat) (42 specimens of A. caraya, 5 of Callithrix jacchus and 4 of C. apella) were negative in both tests. The parasitological prevalence of P. vivax and P. malariae in wild monkeys from Atlantic forest and semideciduous Atlantic forest and the finding of a positive result for P. falciparum in Alouatta from both types of forest support the hypothesis that monkeys belonging to this genus could be a potential reservoir. Furthermore, these findings raise the question of the relationship between simian and autochthonous human malaria in extra-Amazonian regions.

Dispersal of Culex quinquefasciatus (Diptera: Culicidae) in a Hawaiian rain forest

Introduced mosquito-borne pathogens avian malaria (Plasmodium relictum Grassi and Feletti) and avian pox virus (Avipoxvirus) have been implicated in the past extinctions and declines of Hawaiian avifauna and remain significant obstacles to the recovery and restoration of endemic Hawaiian birds. Effective management of avian disease will require extensive mosquito control efforts that are guided by the local ecology of the vector Culex quinquefasciatus Say (Diptera: Culicidae). During October and November 1997 and September through November 1998 five mark-release-recapture experiments with laboratory-reared Cx. quinquefasciatus were conducted in a native rain forest on Hawaii Island. Of the overall 66,047 fluorescent dye-marked and released females, 1,192 (1.8%) were recaptured in 43-52 CO2-baited traps operated for 10-12-d trapping periods. Recaptured mosquitoes were trapped in all directions and at distances up to 3 km from the release site. The cumulative mean distance traveled (MDTs) over the trapping period ranged from a high of 1.89 km after 11 d (September 1998) to a low of 0.81 km after 11 d (November 1998). Released mosquitoes moved predominately in a downwind direction and they seemed to use forestry roads as dispersal corridors. Applying an estimated MDT of 1.6 km to a geographical information system-generated map of the Hakalau Forest National Wildlife Refuge clearly demonstrated that the effective refuge area could be reduced 60% by mosquitoes infiltrating into managed refuge lands. These findings should have significant implications for the design of future refuges and development of effective mosquito-borne avian disease control strategies.

Malaria and Hepatocystis species in wild macaques, southern Thailand

Southeast Asian macaques are natural hosts for a number of nonhuman primate malaria parasites; some of these can cause diseases in humans. We conducted a cross-sectional survey by collecting 99 blood samples from Macaca fascicularis in southern Thailand. Giemsa-stained blood films showed five (5.1%) positive samples and six (6.1%) isolates had positive test results by polymerase chain reaction. A phylogenetic tree inferred from the A-type sequences of the small subunit ribosomal RNA gene confirmed Plasmodium inui in five macaques; one of these macaques was co-infected with P. coatneyi. Hepatocystis, a hemoprotozoan parasite transmitted by Culicoides, was identified in an isolate that was confirmed by analysis of mitochondrial cytochrome b sequences. All malaria-infected monkeys lived in mangrove forests, but no infected monkeys were found in an urban area. These findings indicate regional differences in malaria distribution among these macaques, as well as differences in potential risk of disease transmission to humans.

Icsbp1/IRF-8 is required for innate and adaptive immune responses against intracellular pathogens

The chronic myeloid leukemia syndrome of the BXH-2 mouse strain (Mus musculus) is caused by a recessive mutation (R294C) in the transcriptional regulator Icsbp1/IRF-8. In trans activation assays using an IL-12p40 gene reporter construct introduced in RAW 264.7 mouse macrophages, we show that the Icsbp1(C294) isoform behaves as a partial loss-of-function. The Icsbp1(C294) hypomorph allele appears to have a threshold effect on IL-12 production, with pleiotropic consequences on resistance to different types of infections in vivo. Despite the presence of a resistance Nramp1(G169) allele, BXH-2 mice (Icsbp1(C294)) show impaired control of Mycobacterium bovis (bacille Calmette-Guérin) multiplication both early and late during infection, with uncontrolled replication linked to inability to form granulomas in infected liver and spleen. Studies in informative (BXH-2 x BALB/cJ)F(2) mice show that homozygosity for Icsbp1(C294) causes susceptibility to Salmonella enterica serovar Typhimurium to a level comparable to that seen for mice lacking functional Nramp1 or TLR4. Finally, impaired Icsbp1(C294) function is associated with the following: 1) increased replication of the Plasmodium chabaudi AS malarial parasite during the first burst of blood parasitemia, and 2) recurring waves of high blood parasitemia late during infection. These results show that Icsbp1 is required for orchestrating early innate responses and also long-term immune protection against unrelated intracellular pathogens.

[Morphology, biology and life-cycle of Plasmodium parasites]

Laveran first discovered that an infectious agent was responsible for malaria by using a simple microscope, without the assistance of specific stains. Our knowledge of the Plasmodium life cycle and cellular biology has progressed with each technological advance, from Romanovsky staining and histology to electron microscopy, immunocytochemistry, molecular methods and modern imaging techniques. The use of bird, primate and rodent models also made a major contribution, notably in the development of antimalarial drugs that are still in use today.

Clonal diversity of a lizard malaria parasite, Plasmodium mexicanum, in its vertebrate host, the western fence lizard: role of variation in transmission intensity over time and space

Within the vertebrate host, infections of a malaria parasite (Plasmodium) could include a single genotype of cells (single-clone infections) or two to several genotypes (multiclone infections). Clonal diversity of infection plays an important role in the biology of the parasite, including its life history, virulence, and transmission. We determined the clonal diversity of Plasmodium mexicanum, a lizard malaria parasite at a study region in northern California, using variable microsatellite markers, the first such study for any malaria parasite of lizards or birds (the most common hosts for Plasmodium species). Multiclonal infections are common (50-88% of infections among samples), and measures of genetic diversity for the metapopulation (expected heterozygosity, number of alleles per locus, allele length variation, and effective population size) all indicated a substantial overall genetic diversity. Comparing years with high prevalence (1996-1998 = 25-32% lizards infected), and years with low prevalence (2001-2005 = 6-12%) found fewer alleles in samples taken from the low-prevalence years, but no reduction in overall diversity (H = 0.64-0.90 among loci). In most cases, rare alleles appeared to be lost as prevalence declined. For sites chronically experiencing low transmission intensity (prevalence approximately 1%), overall diversity was also high (H = 0.79-0.91), but there were fewer multiclonal infections. Theory predicts an apparent excess in expected heterozygosity follows a genetic bottleneck. Evidence for such a distortion in genetic diversity was observed after the drop in parasite prevalence under the infinite alleles mutation model but not for the stepwise mutation model. The results are similar to those reported for the human malaria parasite, Plasmodium falciparum, worldwide, and support the conclusion that malaria parasites maintain high genetic diversity in host populations despite the potential for loss in alleles during the transmission cycle or during periods/locations when transmission intensity is low.

Experimental test for premunition in a lizard malaria parasite (Plasmodium mexicanum)

Premunition in Plasmodium spp. is the prevention of superinfection by novel genotypes entering an already established infection in a vertebrate host. Evidence for premunition was sought for the lizard malaria parasite, P. mexicanum, in its natural host, the fence lizard, Sceloporus occidentalis. Clonal diversity (= alleles for the haploid parasite) was determined with the use of 3 microsatellite markers. Both naturally infected lizards (N = 25) and previously noninfected lizards (N = 78) were inoculated intraperitoneally (IP) with blood from donor infections and followed over a 3-mo period. Compared to the success of clonal establishment in all the naive lizards (78/78 successful), clones entering preexisting infections had a significant disadvantage (9/25 successful). The number of preexisting clones (1-2 vs. 3-4) within recipient infections had no effect on the success of superinfection. Infections that excluded entering novel clones did not have higher initial asexual parasitemia, but had a higher initial density of gametocytes, suggesting they were older. Infections allowing superinfection experienced a higher final parasitemia.

Transmission of human and macaque Plasmodium spp. to ex-captive orangutans in Kalimantan, Indonesia

Data are lacking on the specific diseases to which great apes are susceptible and the transmission dynamics and overall impact of these diseases. We examined the prevalence of Plasmodium spp. infections in semicaptive orangutans housed at the Orangutan Care Center and Quarantine, Central Kalimantan, Indonesia, by using a combination of microscopic and DNA molecular techniques to identify the Plasmodium spp. in each animal. Previous studies indicated 2 orangutan-specific Plasmodium spp., but our data show 4 Plasmodium spp. These findings provide evidence for P. vivax transmission between humans and orangutans and for P. cynomolgi transmission between macaques and orangutans. These data have potential implications for the conservation of orangutans and also for the bidirectional transmission of parasites between orangutans and humans visiting or living in the region.

MALARIA AND RISK OF PREDATION: A COMPARATIVE STUDY OF BIRDS

Predators have been hypothesized to prey on individuals in a poor state of health, although this hypothesis has only rarely been examined. We used extensive data on prey abundance and availability from two long-term studies of the European Sparrowhawk (Accipiter nisus) and the Eurasian Goshawk (Accipiter gentilis) to quantify the relationship between predation risk of different prey species and infection with malaria and other protozoan blood parasites. Using a total of 31 745 prey individuals of 65 species of birds from 1709 nests during 1977-1997 for the Sparrowhawk and a total of 21 818 prey individuals of 76 species of birds from 1480 nests for the Goshawk during 1977-2004, we show that prey species with a high prevalence of blood parasites had higher risks of predation than species with a low prevalence. That was also the case when a number of confounding variables of prey species, such as body mass, breeding sociality, sexual dichromatism, and similarity among species in risk of predation due to common descent, were controlled in comparative analyses of standardized linear contrasts. Prevalence of the genera Haemoproteus, Leucocytozoon, Plasmodium, and Trypanosoma were correlated with each other, and we partitioned out the independent effects of different protozoan genera on predation risk in comparative analyses. Prevalence of Haemoproteus, Leucocytozoon, and Plasmodium accounted for interspecific variation in predation risk for the two raptors. These findings suggest that predation is an important factor affecting parasite-host dynamics because predators tend to prey on hosts that are more likely to be infected, thereby reducing the transmission success of parasites. Furthermore, this study demonstrates that protozoan infections are a common cause of death for hosts mediated by increased risk of predation.

Temporal dynamics and diversity of avian malaria parasites in a single host species

1. We have used molecular methods to unravel a remarkable diversity of parasite lineages in a long-term population study of great reed warblers Acrocephalus arundinaceus that was not foreseen from traditional microscopic examination of blood smears. This diversity includes eight Haemoproteus and 10 Plasmodium lineages of which most probably represent good biological species. 2. Contrary to expectation, the relative frequency of parasite lineages seemed not to change over the 17-year study period and we found no effects of the parasites on a male secondary sexual ornament (song repertoire size) and two measures of fitness (adult survival and production of recruited offspring). 3. We discuss whether the absence of fitness consequences of the parasites might relate to the fact that we have studied the host at the breeding sites in Europe, whereas the transmission seems to take place at the wintering sites in Africa, where the naïve birds encounter the parasites for the first time and the resulting primary infections likely make them sicker than during the chronic phase of the infection. 4. The prevalence of the three most common lineages appeared to fluctuate in parallel with a periodicity of approximately 3-4 years. Theoretical models based on intrinsic interactions between parasite antigen and host immune genes cannot explain such dynamics, suggesting that knowledge of extrinsic parameters such as vector distribution and alternative hosts are required to understand these patterns.

Studies on sporozoite-induced and chronic infections with Plasmodium fragile in Macaca mulatta and New World monkeys

Plasmodium fragile continues to be investigated because of its biologic similarities to the human malaria parasite, Plasmodium falciparum. Two strains of P. fragile are available for study; one strain is able to infect mosquitoes, whereas the other strain is transmissible only by blood inoculation. The Sri Lanka strain of P. fragile was transmitted to Macaca mulatta, Macaca fascicularis, Aotus lemurinus griseimembra, Aotus nancymaae, Aotus vociferans, and Saimiri boliviensis monkeys via sporozoites that developed to maturity only in Anopheles dirus mosquitoes. The prepatent periods ranged from 12 to 35 days for macaques and from 15 to 30 days for New World monkeys after intravenous injection of sporozoites. Eight rhesus monkeys were infected with the Nilgiri strain and followed for 482 days. Parasitemia in 6 animals persisted at relatively high density through the period of observation. Erythrocyte, hematocrit, and hemoglobin values reached their lowest levels 3 wk after infection and slowly recovered; however, the values did not approach preinfection levels as long as parasitemia persisted in the monkeys. The mean corpuscular volume and corpuscular hemoglobin concentration reached their peak and lowest values, respectively, at day 38 and then returned to the preinfection level. The mean corpuscular hemoglobin value decreased to its lowest level at day 87 and then returned to preinfection level.

Morphologically defined subgenera of Plasmodium from avian hosts: test of monophyly by phylogenetic analysis of two mitochondrial genes

Malaria parasites in the genus Plasmodium are now placed within 11 subgenera based on morphology under the light microscope, life-history traits, and host taxon. The phylogenetic significance of these characters, however, is problematic because the observed variation could be homoplasious. Using Plasmodium infections found in 2632 birds of many avian families collected in the USA, and several samples from other locations, we compared identifications to subgenus based on morphology in blood smears with a 2-gene molecular phylogeny (the first for avian Plasmodium) to determine if the 5 avian Plasmodium subgenera represent monophyletic groups. Phylogenetic trees recovered by parsimony, likelihood, and Bayesian methods presented nearly identical topologies. The analysis allowed testing the hypothesis of monophyly for the subgenera. Monophyly of the subgenera Haemamoeba, Huffia, and Bennettinia was supported by the analysis. The distinctive morphology of Haemamoeba species appears to have evolved once. Most samples identified to Novyella also fell within a monophyletic clade with the exception of 2 samples that fell basal to all other avian Plasmodium. Samples of the subgenus Giovannolaia did not form a monophyletic group. Thus, the characters used by parasitologists for over a century to define subgenera of Plasmodium vary in their phylogenetic significance.

PARASITES IN A BIODIVERSITY HOTSPOT: A SURVEY OF HEMATOZOA AND A MOLECULAR PHYLOGENETIC ANALYSIS OF PLASMODIUM IN NEW GUINEA SKINKS

A sample of 204 skinks (Squamata: Scincidae) from 10 genera representing 24 species were collected from 10 different localities in New Guinea and examined for blood parasites. Hemogregarines, trypanosomes, microfilarial worms, and 8 infections showing 2 distinct morphological types of malaria parasites (Plasmodium sp.) were observed. Molecular sequence data, in the form of mitochondrial cytochrome b sequences from the Plasmodium infections, showed 2 distinct clades of parasites, 1 in Sphenomorphus jobiense hosts and 1 in Emoia spp., which correspond to the 2 morphotypes. There was substantial genetic variation between the 2 clades, as well as within the clade of Emoia parasites. Nearly half of the skinks sampled had green blood pigmentation, resulting from the presence of biliverdin in the plasma; however, only 1 of these lizards was infected with Plasmodium sp. and only 2 had any blood parasites. These preliminary results suggest a high degree of phylogenetic diversity but a very low prevalence of Plasmodium spp. infections in the skinks of this globally important biodiversity hot spot.

The phylogeny of rodent malaria parasites: simultaneous analysis across three genomes

Species of Plasmodium that naturally infect wild rodents but can also be maintained in laboratory mice have long been used as model systems in which to study the biology of malaria parasites. Several of these rodent parasites are now providing useful genomic comparisons to those species that cause malaria in humans. Here we examined the phylogenetic relationships of 19 strains of rodent malaria parasites including four species native to African thicket rats (Plasmodium berghei, Plasmodium chabaudi, Plasmodium vinckei, and Plasmodium yoelii) and one from a porcupine (Plasmodium atheruri) using DNA sequence data collected from seven genes from each of the three parasite genomes. These included the nuclear dihydrofolate reductase gene and a cysteine protease gene, mitochondrial cytochrome b and cytochrome oxidase I genes, and the elongation factor tufA, caseinolytic protease C, and "open reading frame 470" genes from the apicoplast genome, for a combined total of 5049 nucleotides. Using simultaneous analysis, a method of combining each of the gene partitions into a super-matrix, two equally parsimonious trees were recovered. Bayesian analysis of the dataset produced the same topology. The basic species groups were well supported, with the exception of the placement of P. atheruri within the P. vinckei clade. Named subspecies showed a wide array of genetic differentiation, but fell into monophyletic groups.

Contrasting histories of G6PD molecular evolution and malarial resistance in humans and chimpanzees

Although mutations in the glucose-6-phosphate dehydrogenase (G6PD) gene result in several blood-related diseases in humans, they also confer resistance to malarial infection. This association between G6PD and malaria was supported by population genetic analyses of the G6PD locus, which indicated that these mutations may have recently risen in frequency in certain geographic regions as a result of positive selection. Here we characterize nucleotide sequence variation in a 5.2-kb region of the G6PD locus in a population sample of 56 chimpanzees, as well as among 7 other nonhuman primates, to compare with that in humans in determining whether other primates that are impacted by malaria also exhibit patterns of G6PD polymorphism or divergence consistent with positive selection. We find that chimpanzees have several amino acid variants but that the overall pattern at G6PD in chimpanzees, as well as in Old and New World primates in general, can be explained by recent purifying selection as well as strong functional constraint dating back to at least 30-40 MYA. These comparative analyses suggest that the recent signature of positive selection at G6PD in humans is unique.

Natural transmission of Plasmodium knowlesi to humans by Anopheles latens in Sarawak, Malaysia

Four species of malaria parasites are known to infect humans. A fifth species, Plasmodium knowlesi, has been reported to infect humans in Malaysian Borneo. Here we report for the first time the incrimination of Anopheles latens as the vector of P. knowlesi among humans and monkeys in Sarawak, Malaysia.

Observations on the exoerythrocytic stages of different isolates of Plasmodium cynomolgi in hepatocytes of New World aotus and Saimiri monkeys

Sporozoites of 3 isolates of Plasmodium cynomolgi dissected from the salivary glands of Anopheles dirus and Anopheles quadrimaculatus were injected intravenously into 9 New World monkeys. Liver stage parasites were demonstrated in all 9 animals; 7 of these animals also produced blood stages after prepatent periods of 9 to 23 days.

Oral vaccination of mice against rodent malaria with recombinant Lactococcus lactis expressing MSP-1(19)

AIM

To construct the recombinant Lactococcus lactis as oral delivery vaccination against malaria.

METHODS

The C-terminal 19-ku fragments of MSP1 (MSP-1(19)) of Plasmodium yoelii 265-BY was expressed in L. lactis and the recombinant L. lactis was administered orally to BALB/c and C57BL/6 mice. After seven interval vaccinations within 4 wk, the mice were challenged with P. yoelii 265-BY parasites of erythrocytic stage. The protective efficacy of recombinant L. lactis was evaluated.

RESULTS

The peak parasitemias in average for the experiment groups of BALB/c and C57BL/6 mice were 0.8+/-0.4% and 20.8+/-26.5%, respectively, and those of their control groups were 12.0+/-0.8% and 60.8+/-9.6%, respectively. None of the BALB/c mice in both experimental group and control group died during the experiment. However, all the C57BL/6 mice in the control group died within 23 d and all the vaccinated mice survived well.

CONCLUSION

The results imply the potential of recombinant L. lactis as oral delivery vaccination against malaria.

Widespread occurrence of antibodies against circumsporozoite protein and against blood forms of Plasmodium vivax, P. falciparum and P. malariae in Brazilian wild monkeys

BACKGROUND

A survey of malaria antibodies was carried out over 7 years and a total of 777 serum samples from wild monkeys were collected in three distinct ecological areas of Brazil where autochthonous malaria has been reported: the 'Cerrado' (similar to savanna), the Atlantic Forest and the Atlantic Semideciduous Forest.

METHODS

We carried out enzyme-linked immunosorbent assay to investigate the presence of IgG antibodies against peptides of the circumsporozoite protein (CSP) repeat region of 'classic'Plasmodium vivax, P. vivax VK247, human P. vivax-like/P. simiovale, P. brasilianum/P. malariae and P. falciparum. We also carried out immunofluorescence assay with asexual forms of P. vivax, P. malariae and P. falciparum.

RESULTS

The high prevalence of antibodies against CSP in all areas indicates that the monkeys had intense contact with sporozoites from infected anophelines. The immune response against asexual forms of Plasmodium in the monkeys from the Atlantic Forest indicates the development of the infection.

CONCLUSIONS

We discuss the possibility of monkeys being malaria reservoirs in non-endemic areas.

Detection of a Malaria Parasite (Plasmodium mexicanum) in Ectoparasites (Mites and Ticks), and Possible Significance for Transmission

Two species of sandflies (Lutzomyia) are competent vectors of Plasmodium mexicanum, a malaria parasite of lizards. The very patchy distribution of sites with high P. mexicanum prevalence in the lizards, and often low or even nil sandfly density at such sites, provoked an evaluation of 2 common lizard ectoparasites, the tick Ixodes pacificus and the mite Geckobiella occidentalis, as potential passive vectors. Plasmodium sp.-specific polymerase chain primers were used to amplify a long segment of the mitochondrial cytochrome b gene that is unlikely to survive intact if the parasite cells are killed within a blood-feeding arthropod. The segment was strongly amplified from sandflies (the positive control for the method) from 1 to 96 hr postfeeding on an infected lizard. For ticks, the gene fragment was poorly amplified at 0 hr postfeed, and not amplified after 2 hr. In contrast, strong amplification of the parasite DNA was observed from mites from 0 to 20 hr postfeed, and weak amplification even at 96 hr.