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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ability of parasites to change the behavior of infected hosts has been documented and reviewed by a number of different authors (Holmes and Bethel, 1972; Moore, 1984a). This review attempts to quantify the population dynamic consequences of this behavior by developing simple mathematical models for the most frequently recorded of such parasite life cycles. Although changes in the behavior of infected hosts do occur for pathogens with direct life cycles, they are most commonly recorded in the intermediate hosts of parasites with complex life cycles. All the changes in host behavior serve to increase rates of transmission of the parasites between hosts. In the simplest case the changes in behavior increase rates of contact between infected and susceptible conspecific hosts, whereas in the more complex cases fairly sophisticated manipulations of the host's behavioral repertory are achieved. Three topics are dealt with in some detail: (1) the behavior of the insect vectors of such diseases as malaria and trypanosomiasis; (2) the intermediate hosts of helminths whose behavior is affected in such a way as to make them more susceptible to predation by the definitive host in the life cycle; and (3) the behavior and fecundity of molluscs infected with asexually reproducing parasitic flatworms. In each case an expression is derived for R0, the basic reproductive rate of the parasite when first introduced into the population. This is used to determine the threshold numbers of definitive and intermediate hosts needed to maintain a population of the pathogen. In all cases, parasite-induced changes in host behavior tend to increase R0 and reduce the threshold number of hosts required to sustain the infection. The population dynamics of the interaction between parasites and their hosts are then explored using phase plane analyses. This suggests that both the parasite and intermediate host populations may show oscillatory patterns of abundance. When the density of the latter is low, parasite-induced changes in host behavior increase this tendency to oscillate. When intermediate host population densities are high, parasite population density is determined principally by interactions between the parasites and their definitive hosts, and changes in the behavior of intermediate hosts are less important in determining parasite density. Analysis of these models also suggests that both asexual reproduction of the parasite within a host and parasite-induced reduction in host fecundity may be stabilizing mechanisms when they occur in the intermediate hosts of parasite species with indirect life cycles.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The population biology of parasite-induced changes in host behavior. 304 62

Chloroquine-resistant Plasmodium vivax was originally reported in Papua, New Guinea by Reickman in 1989.1 In the same year, in Colombia, South America, Arias and Corredor2 reported relapses of 11 patients suffering from vivax malaria, following a chloroquine-primaquine regimen. Garavelli and Corti3 suggested chloroquine-resistant Plasmodium vivax may be present in Brazil following these therapeutic relapses. Further therapeutic failures in returned travelers from South America were reported by Moore et al (1994).4 We report vivax malaria in a group of expeditioners visiting Guyana who, whereas compliant with antimalarial chemoprophylaxis, developed clinical malaria, adding evidence to the presence of chloroquine-resistant Plasmodium vivax in South America. Raleigh International is a youth development charity that undertakes environmental and community projects around the world. These are usually in remote locations. Nine expeditions in countries such as Chile, Belize, Zimbabwe, Uganda, and Malaysia are organized annually. A project manager and a medical officer are placed at each site, along with approximately 10 venturers (age 17-25.) Participants are of all nationalities, but, at present, they are predominantly British.
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PMID:Prophylaxis Failure Against Vivax Malaria in Guyana, South America. 981 25

The 35 kb circular genome (plDNA) of the Plasmodium falciparum apicoplast replicates by the bidirectional ori/D-loop mechanism. PlDNA replication was previously shown to initiate within the inverted repeat (IR) region of the apicoplast genome [Williamson DH, Preiser PR, Moore PW, McCready S, Strath M, Wilson RJM (Iain). The plastid DNA of the malaria parasite Plasmodium falciparum is replicated by two mechanisms. Mol Microbiol 2002;45:533-42; Singh D, Chaubey S, Habib S. Replication of the Plasmodium falciparum apicoplast DNA initiates within the inverted repeat region. Mol Biochem Parasitol 2003;126:9-14.] and the presence of at least two ori within each segment of the IR was postulated. Using 5' end-labelled nascent DNA as probe, we now demonstrate the utilization of several putative ori located within the IR for plDNA replication. Quantitation of signals obtained for different segments of the IR as well as determination of the number of molecules emanating from two ori regions by competitive PCR analysis indicated differential strengths of ori during plDNA replication prior to schizogony.
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PMID:Multiple replication origins within the inverted repeat region of the Plasmodium falciparum apicoplast genome are differentially activated. 1561 Aug 24

Blood parasites infect all vertebrates (Clayton and Moore 1997). Avian malaria parasites (Plasmodium spp., Plasmodiidae) are cosmopolitan in their distribution and are responsible for severe diseases in domestic and wild birds.In September 2009, nine raptorial birds that either arrived recently or were maintained as permanent residents at the Safaripark Pombia (northwest Italy) showed loss of stamina, developing listlessness, anorexia and regurgitation. Within one month three animals died and were necropsied.Following the diagnosis of Plasmodium infection all other raptorial birds were treated: clinical improvement was observed in all birds, and blood smears made after one month resulted negative for parasites.
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PMID:Plasmodium spp. In a captive raptor collection of a Safaripark in northwest Italy. 2685 May 50