Simian malaria at two sites in the Brazilian Amazon--II. Vertical distribution and frequency of anopheline species inside and outside the forest

An anopheline survey was carried out in two simian malaria areas in the Brazilian Amazon, Balbina and Samuel, to determine the potential vectors of Plasmodium brasilianum. The most abundant and/or acrodendrophilic anophelines in the forest and the most likely vector were Anopheles mediopunctatus, An. nuneztovari, An. oswaldoi, An. triannulatus and An. shannoni. An. darlingi and An. marajoara were captured essentially in anthropic habitats outside the forest and are unlikely to be involved in the transmission of P. brasilianum among monkeys within the forests and from monkeys to man in their surroundings in the Amazon.

Host range, survival in dead hosts, cryopreservation, periodicity and morphology of Plasmodium durae Herman in experimental infections

In experimental infections, fowl, duck, guineafowl and canary were refractory to Plasmodium durae, which in Japanese quail produced low and transient infections, but a high and long-lasting parasitaemia in a Lady Amherst pheasant. Heart, blood and brain of dead hosts injected into turkeys, allowed the recovery and further passaging of the live parasite. This technique could be useful for the recovery of malaria parasites from suspect postmortem material. Intravenous infection produced parasitaemias in chicken and turkey embryos, while attempts at altantoic-sac infections of chicken embryos were unsuccessful. A certain degree of periodicity of schizogony was demonstrated. The South African isolates of P. durae had smaller schizonts than those described from East and West Africa, with 2-14 merozoites (mostly four). Some strains did not produce mature gametocytes in the experimental hosts. Exoerythrocytic schizonts of P. durae are depicted in this paper for the first time.

The Nigerian I/CDC strain of Plasmodium ovale in chimpanzees

The chimpanzee is the only animal host currently available that can support the development of the human malaria parasite Plasmodium ovale. Thirty-one infections with the Nigerian I/CDC strain were induced in splenectomized chimpanzees. Maximum parasite counts ranged from 1,240 to 127,224/microliters. Infections were transient and unpredictable. Anopheles stephensi, Anopheles gambiae, Anopheles freeborni, and Anopheles dirus mosquitoes were infected by feeding through parafilm membranes on heparinized blood containing gametocytes; each species supported development to sporozoites in the salivary glands. Mean oocyst counts per infected mosquito ranged from 1 to 85.1; 21.7% of infected lots of mosquitoes averaged > 20 oocysts per positive mosquito gut. One infection was induced via the bites of infected An. gambiae. The prepatent period was 16 days.

Distribution and abundance of two malarial parasites of the endemic Anolis lizard of Saba Island, Netherlands Antilles

The ecology of 2 parasites, Plasmodium floridense and Plasmodium azurophilum, was studied in the endemic lizard, Anolis sabanus, on Saba island in the eastern Caribbean. Prevalence of the two parasite species was similar, but prevalence varied among sites. Lowest prevalence occurred at dry, windy sites or cool, wet mountain peaks (0-20%); the parasites were more common at most other locations on the island (40-80% infected; overall prevalence = 47%). High and low prevalence sites sometimes were only a few hundred meters apart. Prevalence was similar for males and females but increased with body size except for a decline in the largest ( = oldest) lizards. A surplus of mixed infections (P. floridense and P. azurophilum together in the same host) existed compared with chance proportions. Parasitemia generally was low; 70% of P. floridense infections were < or = 100 parasites/10,000 erythrocytes, and 70% of P. azurophilum infections were < or = 50/10,000. Parasitemia in solitary infections averaged more than twice that seen in mixed infections for both species.

Molecular differentiation of two new world saurian Plasmodium species in different host species using the polymerase chain reaction

Several isolates of Plasmodium floridense obtained from naturally infected Anolis carolinensis and Anolis sagrei, and 2 isolates of Plasmodium chiricahuae obtained from Sceloporus jarrovi were characterized at the ribosomal DNA (rDNA) locus using the polymerase chain reaction and agarose gel electrophoresis. Enzymatic amplification of the rDNA locus from both Plasmodium species resulted in the generation of a 590-base pair (bp) DNA fragment. The results obtained with all isolates of P. floridense appeared as a doublet, with the second fragment being approximately 630 bp in size. Isolates of P. floridense obtained from A. carolinensis from ecologically different northern and southeastern Florida, and from A. sagrei a the same southeastern Florida site, were demonstrated to be molecularly similar. Plasmodium floridense and P. chiricahuae were molecularly distinct at the 18s rDNA locus, thus confirming their morphological and morphometrical distinction as taxonomic species. Anolis sagrei is a third natural host species for P. floridense in Florida.

Epizootiology of the Japanese saurian malaria parasite, Plasmodium sasai

Histological examination of hearts from 422 Japanese lacertids Takydromus tachydromoides collected at Hanno, Saitama-ken, Honshu, from 1965 to 1967, demonstrated the presence of Plasmodium sasai Telford and Ball, 1969 in 85% of first-year lizards and 92% of those older than 1 yr. Prevalence in 1966-1967, estimated by examination of blood films alone was < 1%, and no infections were detected in 1965 by this method. Prevalence differed only slightly or not at all between years, seasons, host age group, or host sex. Infection occurred immediately after hatching from August into October in each year. In the cohort hatched in 1965, prevalence had reached 100% by November, declined slightly following hibernation, but reached 100% by May. Phanerozoites were present in every month, but encysted chronozoites were found most often in March, following hibernation. Erythroid cells that contained 2->20 uninucleate parasites were sequestered within capillaries of the heart in newly infected juvenile lizards. Vectors apparently were infected from adult lizards with chronic, low level, predominantly gametocytic infections in late summer and fall and transmitted P. sasai to at least 80% of the hatchling cohort, beginning within the first few days of life, producing parasitemias at barely detectable levels. Some transmission may have occurred in late spring but probably to no more than 15% of the host population.

Plasmodium yoelii: the role of the individual epidermal growth factor-like domains of the merozoite surface protein-1 in protection from malaria

The merozoite surface protein-1 (MSP-1) is a leading candidate for a vaccine targeted at the erythrocytic stages of plasmodial parasite development. Recently, there has been increasing interest in this polypeptide, particularly in the carboxyl-terminal EGF-like domains. We have previously shown that this region from Plasmodium yoelii, when expressed in native configuration, could immunize mice against an otherwise lethal challenge infection. In this model system, protection appears to be predominantly mediated by antibodies. In all rodent immunization studies to date, however, the immunogen has contained both of the postulated EGF-like domains. We report here on the efficacy of immunization with the individual EGF-like domains from P. yoelii in elicitation of a protective host response. Although all animals developed some level of antibody in response to the various immunogens, only those animals immunized with both EGF-like domains produced antibodies which could recognize the native MSP-1 molecule. Antibodies generated against the individual EGF-like domains did cross-react with the double EGF-like domain structure, suggesting that the immunogens had retained elements of native configuration. In addition, only those animals which generated antibodies capable of recognizing native MSP-1 showed any level of protection from challenge infection. These results suggest that determinants unique to the double EGF-like domain structure may be necessary for the generation of antibodies specific for the native configuration of MSP-1 and that these antibodies may play a significant role in protection.

Reconstitution of B-cell-depleted mice with B cells restores Th2-type immune responses during Plasmodium chabaudi chabaudi infection

In mice depleted of B cells from birth by treatment with anti-immunoglobulin M(mu) antibodies, progression from a Th1- to a Th2-regulated immune response during primary infection with Plasmodium chabaudi chabaudi fails to occur. While Th1-type immunity limits parasitemia, in the absence of B cells, chronic low-grade infections persist. Here, we show that reconstituting immune, and to a lesser extent naive, B cells to mice rendered deficient in B-cell function through anti-immunoglobulin M(mu) pretreatment restores the CD4+ T-cell response to the Th2 type later in P. c. chabaudi infection and with it the capacity to eliminate infection. This finding provides clear evidence that B cells are required for switching the balance of immune regulation between CD4+ T cells from Th1 to Th2 during P.c. chabaudi infection and supports the concept that B cells, through antibody production, are needed for effective antimalarial immunity.

Parasitized erythrocyte membrane antigens of Plasmodium brasilianum: relationships with the ring-infected erythrocyte surface antigen of Plasmodium falciparum

An antigen, designated here as the parasitized erythrocyte membrane antigen (PEMA), is present in the erythrocyte membrane surrounding all intraerythrocytic stages of Plasmodium brasilianum. An antibody specific for PEMA appeared in 21 (50%) of 42 antisera from Saimiri sciureus monkeys naturally infected with P. brasilianum. Of these 42 sera, nine (21.4%) contained antibody to the ring-infected erythrocyte membrane antigen (RESA); of these nine sera, six did not react with PEMA. Sera of humans infected with P. malariae reacted with PEMA and RESA in a similar pattern; i.e., of 83 antisera, 71 (85.5%) reacted with PEMA and 30 (36%) reacted with RESA. Only one of these latter 30 sera were not reactive with PEMA. Of 167 sera from humans infected with P. falciparum but not P. malariae, 133 (79.6%) reacted with RESA; of these, 43 (25.7% of the total) reacted with PEMA but not RESA. Although PEMA was demonstrated with P. brasilianum and RESA with P. falciparum, neither PEMA or RESA could be demonstrated with P. malariae. Interactions of PEMA and RESA and the corresponding antibodies offer a method whereby the two morphologically similar quartan species, P. malariae and P. brasilianum, can be readily distinguished from each other and may furnish clues to genetic separation of the two and the mechanisms of interaction of quartan malaria and P. falciparum where they are coendemic.

The blood-stages of Plasmodium georgesi, P. gonderi and P. petersi: course of untreated infection in their natural hosts and additional morphological distinctive features

In the blood of a Cercocebus albigena and of a C. galeritus agilis monkey, the infection with Plasmodium gonderi was found to follow its well-known chronic course; P. georgesi seemed to occur as a relapsing type of malaria parasite; P. petersi was found for only a few days and at a low level in C. albigena (end of an attack?). As shown by using polarized light, the pigment granules appeared mostly as fine dots in P. georgesi, short rods in P. gonderi and long needles in P. petersi. The three species can be distinguished by the morphological appearance of the nucleus of the young trophozoites, and also by the measurement of its surface area (Sa): small round nucleus (Sa = 0.81 +/- 0.06 microns 2) in P. gonderi, large 2-coloured nucleus (Sa = 1.43 +/- 0.21 microns 2) in P. petersi, and long crescent-shaped nucleus (Sa = 2.18 +/- 0.25 microns 2) in P. georgesi. The first colour illustrations of the blood-stages of P. georgesi are presented. The dynamics of single and mixed blood infections in primate malaria parasites are discussed, with a proposal to classify them into 3 types.

Effect of fatty acid treatment in cerebral malaria-susceptible and nonsusceptible strains of mice

Cerebral malaria-susceptible (C57BL/6) mice infected with Plasmodium berghei ANKA (PbA) developed low parasitemia and died from typical neurological symptoms between 8 to 10 days after infection. In contrast, nonsusceptible (BALB/c) mice developed high peripheral blood parasitemia and died 22-24 days later without neurological implications. Daily injections of fatty acids (FA) during the first 3 days after infection protected C57BL/6 mice from cerebral symptoms but had no effect on BALB/c mice. Thus, treated C57BL/6 mice developed hyperparasitemia and died 25 days after infection, like BALB/c mice. Red blood cells from C57BL/6 control mice were found to be more resistant to lysis by linoleic acid than those of BALB/c mice. Three days following infection with PbA, these differences disappeared. Treatment with FA prevented these changes. We concluded that the host's cells were altered soon after infection and that the nature and degree of alterations depended on the mouse strain, thus determining the eventual outcome of the infection. Likewise, the effects of FA might not be directed against the parasite but rather seem to act early after infection on these parasite-induced modifications of host cells.

Simian malaria at two sites in the Brazilian Amazon. I--The infection rates of Plasmodium brasilianum in non-human primates

The parasite that causes simian malaria in the Brazilian Amazon, Plasmodium brasilianum, is infective to man. In this region, where humans live within and in close proximity to the forest, it was suspected that this parasite could be the cause of a zoonosis. A study was performed in the areas surrounding two hydroelectric plants in the Amazon, Balbina and Samuel, aiming at determining the zoonotic potential of this parasite. P. brasilianum was detected in, respectively, 15.8% and 9.9% of 126 and 252 primates belonging to seven and eight species examined from Balbina and Samuel. The highest malaria infection rates were found among the red-howler monkey Alouatta seniculus straminea (32.3%), the bearded-saki Chiropotes satanas chiropotes (50%) and the spider-monkey Ateles paniscus paniscus (2[1+]) from Balbina and in the squirrel-monkey Saimiri ustus (21%) and the black-faced-spider-monkey Ateles paniscus chamek (28.6%) from Samuel.

Transmission immunity in malaria: reflections on the underlying immune mechanisms during natural infections and following artificial immunization

Malaria transmission-blocking immunity has been studied in natural malarial infections in man, during infections in animals and following artificial immunization of animals with sexual stage malaria parasites. Effective immunity, which prevents infectivity of a malarial infection to mosquitoes, has been observed under all of these circumstances. Two general types of effector mechanism have been identified. One is an antibody mediated mechanism which acts against the extracellular sexual stages of the parasite within the midgut of a blood feeding mosquito. The other is a cytokine mediated mechanism which inactivates the gametocytes of the parasites while still in the circulation of the vertebrate host. Both effects have been observed during natural infections and following artificial immunization. The basis of induction of transmission-blocking immunity, including the nature of the memory for such immunity, however, may be very different in different host/parasite systems and during natural infection or following artificial immunization. Following artificial immunization a strong immune memory for transmission blocking immunity has been observed in animal systems. By contrast, following natural infections in man immune memory for transmission blocking immunity has been found to be weak and short lived if it occurs at all. It is suggested that the immunogens which induce natural transmission blocking immunity may be CD4+ independent.

Simian malaria in Brazil

In Brazil simian malaria is widely spread, being frequent in the Amazon region (10% of primates infected) and even more in the forested coastal mountains of the Southeastern and Southern regions (35% and 18% infected, respectively), but absent in the semi-arid Northeast. Only two species of plasmodia have been found: the quartan-like Plasmodium brasilianum and the tertian-like P. simium, but the possible presence of other species is not excluded. P. brasilianum is found in all enzootic foci, but P. simium was detected only on the coast of the Southeastern and Southern regions, between paralles 20 degrees S and 30 degrees S. Nearly all hosts are monkeys (family Cebidae, 28 species harbouring plasmodia out of 46 examined), and very rarely marmosets or tamarins (family Callitrichidae, 1 especies out of 16). P. brasilianum was present in all infected species, P. simium in only two. The natural vector in the Southeastern and Southern regions was found to be Anopheles cruzi, but has not been conclusively identified in the Amazon. One natural, accidental human infection due to P. simium was observed. There is no evidence of the relation of simian to human malaria in the Southeastern and Southern regions, where human malaria was eradicated in spite of the high rates of monkeys infected, but in the Amazon recent serological studies by other workers, revealing high positivity for P. brasilianum/P. malariae antibodies in local indians, would suggest that among them malaria might possibly be regarded as a zoonosis.

Rodent malaria parasites: molecular karyotypes characterize species, subspecies and lines

The molecular karyotypes of the African murine malaria parasites P. berghei (3 strains, 2 lines) P. yoeli (2 strains) P. chabaudi (3 strains, 1 line) and P. vinckei (4 strains) have been studied using orthogonal field alternation gel electrophoresis (OFAGE). The genome of each species was resolved into 9 to 11 distinct chromosomal DNA banas molecules of varying intensities which seem to represent 14 chromosomes ranging in size from 600 kb to 3500 kb. The position of certain chromosomes allowed the identification of a unique karyotype for each of the strains and lines under study. P. yoelii appears by criteria of chromosome size, chromosome numbers and localisation of DNA probes to differ considerably from the other three rodent malaria species. The chromosomal location of 5 DNA probes allowed the identification of corresponding chromosomes in rodent malaria parasites and the differentiation between species and strains. Assignment of the "PMMSA" gene of P. c. chabaudi IP-PC 1 enables the distinction of the four rodent malaria species. The molecular karyotype combined to chromosomal assignment of DNA probes provides a useful tool for a more precise characterization by a genetic definition of malaria parasites.

Pathogenicity and chemotherapy of Plasmodium durae in experimentally infected domestic turkeys

Only 3 out of 8 South African isolates of Plasmodium durae used in 524 turkeys in 161 passages caused approximately 50% mortality, a further 3 produced approximately 10% mortality while 2 were found to be apathogenic. Exoerythrocytic schizonts were the main pathogenic stage. In most survivors the effect on mass gains was minimal. Twelve drugs currently available for use in poultry, as well as chloroquin phosphate, were tested for their activity against experimental infections with Plasmodium durae in domestic turkeys. While chloroquin phosphate showed a certain degree of effectivity, Amprolium, Amprolium + Ethopabate, Maduramycin, Toltrazuril, Metronidazole, Furazolidone, Enrofloxacin and Sulfamethoxypyridazine + Trimethoprim were ineffective. Halofuginone and Penta-Sulfa at a high dose had some protective effect. At high doses Sulfachloropyrazine protected from mortality without affecting the parasitaemia, while Sulfamonomethoxine suppressed parasitaemia without entirely protecting from mortality. From these data it is concluded that Halofuginone has a potential as possible chemoprophylactic. While a combination of Sulfamonomethoxine and Sulfachloropyrazine could be used in the treatment of outbreaks in the field.

A host-parasite list of the haematozoa of domestic poultry in sub-Saharan Africa and the isolation of Plasmodium durae Herman from turkeys and francolins in South Africa

An annotated host-parasite list of the blood parasites of domestic poultry in sub-Saharan Africa is presented. This list contains the haematozoa found in domestic waterfowl (ducks, geese and muscovies) and phasianids (turkey, fowl and peafowl). In South Africa Plasmodium durae was isolated from 4 out of 8 backyard turkeys, from 3 out of 26 Swainson's francolins and from 1 redwing francolin, but not from 20 helmeted guineafowls and 9 greywing francolins. This points at Swainson's and redwing francolins as being the main natural hosts of P. durae in South Africa. The increase in the period of prepatency after intramuscular subinoculation as compared with the intravenous route was found to correspond to that of a 1,000 fold dilution of an intravenous inoculum of parasitized blood. This delay was not due to an intervening cycle of exoerythrocytic schizogony, but to large numbers of the injected erythrocytes apparently not finding their way into the circulation of the new host.

Experimental transmission of murine malaria by the oral route

A total of 116 young male CD1 mice were orally inoculated with mouse blood; half of the animals received 0.2 ml of uninfected blood and the others were given 0.2 ml of Plasmodium berghei yoelii-infected blood in six experiments performed at different times. Almost 30% of the experimental mice acquired malaria as demonstrated by the observation of parasites in their blood. In no case were parasites found in the blood of control mice. Rodent malaria parasites may be transmitted to CD1 mice by the ingestion of mouse blood parasitized by P. b. yoelii. As far as we know, this study represents the first demonstration of oral transmission of murine malaria. Oral transmission studies in this mouse-Plasmodium model may produce very important information on the biology of the malaria parasites.

Plasmodium berghei: sporozoites are sensitive to human serum but not susceptible host serum

Human complement was activated by rodent malaria, Plasmodium berghei, sporozoites through the alternative pathway, as revealed by C3 deposition on sporozoites using the fluorescent antibody technique. Sporozoites exposed to fresh human serum decreased in infectivity to HepG2 cells, but those exposed to heated or C3-deficient human serum showed normal infectivity to HepG2 cells. In contrast, C3 deposition was not observed on the sporozoites treated with mouse or rat serum even in the presence of specific polyclonal anti-sporozoite antibody. However, following treatment with trypsin (250 micrograms/ml), 81% of salivary gland sporozoites and 49% of oocyst sporozoites became reactive with mouse serum, and reactive sporozoites deposited mouse C3 on their surface in the presence of 30 mM EGTA and 1 mM Mg2+ without antibody. Concomitantly some sporozoites lost reactivity to anti-circumsporozoite protein monoclonal antibody. These results suggest that P. berghei sporozoites possibly express surface molecules that regulate the complement activation pathway of susceptible hosts but not of nonhosts, and that the putative structures consist of protease-sensitive molecule(s) which are closely associated with the circumsporozoite protein.

Host association and the capacity of sand flies as vectors of lizard malaria in Panama

In this paper the capacity of sand flies (Lutzomyia) as vectors of parasites that cause malaria in anoles (Anolis limifrons) in the Zona de Canal, Panama was investigated. Inhabiting all study plots, often in local abundance, L. trinidadensis emerged as the principal candidate sand fly vector; the results of surveys did not suggest a likely mosquito vector. Although L. trinidadensis and infected anoles co-inhabited all plots, their abundances seemed unrelated. No evidence that sand flies parasitized anoles was uncovered. As anole activity patterns in daylight reciprocate with those of sand flies and at night anoles seem to avoid locations that sand flies frequent, anoles may evade sand fly bites altogether. Further, these sand flies occurred in close numerical and ecological association with Thecadactylus rapicauda, a reclusive moist forest gecko, often parasitizing these hosts in large numbers. Thus, sand flies lack capacity as vectors of malaria-causing parasites in central Panamanian anoles.

Susceptibility of Macaca fascicularis monkeys from Mauritius to different species of Plasmodium

Macaca fascicularis monkeys from Mauritius were shown to be susceptible via sporozoite inoculation to 7 species of Plasmodium (P. fragile, P. coatneyi, P. gonderi, P. inui, P. cynomolgi, P. knowlesi, and P. fieldi), indigenous to macaques in southeastern Asia. Four monkeys were sequentially infected with different species of Plasmodium to determine maximum and course of parasitemia. In 2 nonsplenectomized monkeys, P. fragile developed maximum parasite counts of only 134 and 155/microliters. For Plasmodium knowlesi, a parasite that is life-threatening to rhesus monkeys, maximum parasite counts were 4,278 and 7,440/microliters. Plasmodium coatneyi developed to what must be considered as moderate levels. After animals underwent splenectomy, parasite counts of P. coatneyi were 58,280, 89,094, 4,464, and 43,524/microliters. The maximum parasite counts for P. gonderi (13,508 and 21,576/microliters) and P. fieldi (1,767 and 17,836/microliters) were lower than would be expected in M. mulatta. In 2 monkeys that developed patent parasitemia with P. inui, the maximum parasite counts (95,046 and 728,748/microliters) indicated that this parasite may be the best adapted species for development in these animals once infection is established. Finally, the reinfection of 2 monkeys with P. cynomolgi suggested that some animals may be basically more resistant than others, whether splenectomized or not, to the production of high-density parasitemia.

Multiple alpha-globin genes in crab-eating macaques (Macaca fascicularis)

Alpha-globin genes in crab-eating macaques were found to be triplicated at high frequencies according to restriction-enzyme comparisons. The frequencies of triplicated alpha-globin genes in macaques originally from Malaysia and Indonesia were 0.432 and 0.275, respectively, while no triplication was found in individuals from either the Philippines or northern and central Thailand. Quadruplicated alpha-globin genes were also observed, at frequencies of 0.045 (Malaysia), 0.075 (Indonesia), and 0.021 (the Philippines). A single locus was detected in only one of 40 chromosomes from Indonesia (frequency 0.025).