Studies on hepatic oxidative stress and antioxidant defence system during chloroquine/poly ICLC treatment of Plasmodium yoelii nigeriensis infected mice

Reactive oxygen species are important mediators of tissue injury during malaria infection. The status of hepatic oxidative stress and antioxidant defence indices were studied during Plasmodium yoelii nigeriensis (P. y. nigeriensis) infection and chloroquine/polyinosinic-polycytidylic acid stabilized with polylysine and carboxymethylcellulose (poly ICLC) treatment of infected mice. P. y. nigeriensis infection resulted in a significant increase in oxidative stress indices viz., xanthine oxidase and rate of lipid peroxidation (LPO). This was accompanied by a highly significant increase in antioxidant defence indices viz., reduced glutathione (GSH) and glutathione reductase while superoxide dismutase (SOD) and catalase showed a highly significant decrease with respect to normal mice. Chloroquine treatment of infected mice caused a decrease in parasitaemia which was associated with restoration of indices altered during infection towards normalization. Poly ICLC treatment of infected mice caused no change in blood parasitaemia but resulted in a significant increase in GSH, glutathione reductase, SOD and catalase with respect to infected mice. Combination therapy of chloroquine and poly ICLC resulted in clearance of parasitaemia and restoration of all oxidative stress and antioxidant defence indices to normal levels.     

Primary peak and chronic malaria infection levels are correlated in experimentally infected great reed warblers

SUMMARY Malaria parasites often manage to maintain an infection for several months or years in their vertebrate hosts. In humans, rodents and birds, most of the fitness costs associated with malaria infections are in the short initial primary (high parasitaemia) phase of the infection, whereas the chronic phase (low parasitaemia) is more benign to the host. In wild birds, malaria parasites have mainly been studied during the chronic phase of the infection. This is because the initial primary phase of infection is short in duration and infected birds with severe disease symptoms tend to hide in sheltered places and are thus rarely caught and sampled. We therefore wanted to investigate the relationship between the parasitaemia during the primary and chronic phases of the infection using an experimental infection approach. We found a significant positive correlation between parasitaemia in the primary peak and the subsequent chronic phase of infection when we experimentally infected great reed warblers (Acrocephalus arundinaceus) with Plasmodium ashfordi. The reason for this association remains to be understood, but might arise from individual variation in exoerythrocytic parasite reservoirs in hosts, parasite antigenic diversity and/or host genetics. Our results suggest that the chronic phase parasitaemia can be used to qualitatively infer the parasitaemia of the preceding and more severe primary phase, which is a very important finding for studies of avian malaria in wild populations.     

An electron microscopic study of intravascular agglutination in the cerebral cortex due to Babesia argentina infection

The progressive changes in brain capillaries of calves infected with Babesia argentina are described. Initially, the parasitaemia was low (about 5 per cent) and infected red cells had an essentially normal appearance. Terminally, the parasitaemia was > 90 per cent and by this time infected cells were stellate in appearance, connected by fine strands to other infected cells, and to the capillary endothelium which also showed pathological changes. Uninfected cells appeared normal at all stages of the infection. In severe cases most infected cells were haemolysed. The presumed stickiness of infected cells was probably due to changes in the erythrocyte membrane. Parasites were larger than normal and usually possessed two or three nuclei, containing aggregations of chromatin.     

Observations of rainbow trout, Salmo gairdneri Richardson, infected with Cryptobia salmostica

Rainbow trout, Salmo gairdneri , were experimentally infected with Cryptobia salmositica . The parasitaemia was associated with increases in the size of the spleen, liver and heart (% body weight). The splenomegaly was pronounced and was often 600-fold larger. The amounts of blood lactic acid and lactic dehydrogenase in the infected and control fish were similar. However, glycogen levels of the liver, heart and epaxial muscle declined. Liver glycogen levels were most affected and decreased to values which represented 20% of the control values. The pattern of the glycogen levels of the liver, heart and epaxial muscle declined to rise to normal values by day 56 post-inoculation. Thus, the glycogen levels both paralleled the acute parasitaemia and the subsequent partial recovery of the infected fish as they tolerated a low chronic parasitaemia.     

Effect of the intensity of host parasitemia on the vectorial competence of Glossina morsitans Westwood, 1850 (Mall) infected by Trypanosoma (Nannonmonas) congolense IL 1180

Two groups of teneral flies (aged less than 32 hours) of Glossina morsitans morsitans (Mall) were fed separately on two rats that had been infected with Trypanosoma (Nannomonas) congolense IL 1180, among which one had a low parasitaemia (antilog 5.4-5.7) and the other a high parasitaemia (antilog 7.8-8.1). Following to the two modes of parasitaemia, variations of the procyclic indexes were found between males and females. When both sexes were considered, it was found that the intestinal infection rate was relatively higher in the flies that were fed on the rat with a low parasitaemia than in those fed on the rat with a high parasitaemia. Although no significant differences in metacyclic indexes were observed between sexes, the mature infection rate was most pronounced in the flies that were fed on the rat with high parasitaemia. When both sexes were considered, the vectorial competence (VC) reached 0.5532 and 0.5521 in the flies that had been fed on the rats with low and high parasitaemia, respectively. The VC of the two modes of infectious feeding was not significantly different. However, when considering the parasitaemia of antilog 5.4-5.7, the VC was relatively more important in the females than in the males. No significant difference in VC was detected between sexes when considering the antilog 7.8-8.1 parasitaemia. It was found that there is discrepancy in the way the metacyclic infection and the VC evolve in relation to the procyclic infection, suggesting that the intensity of the parasitaemia only influences the intestinal stage.     

The therapeutic use of isometamidium chloride against Cryptobia salmositica in rainbow trout Oncorhynchus mykiss.

Rainbow trout Oncorhynchus mykiss injected intramuscularly with isometamidium chloride (0.01 or 0.1 mg kg-1) at 3 wk post-infection and given a booster 2 wk later had significantly lower parasitaemias than infected controls. Packed cell volume increased after treatment and remained higher than in infected controls. The concentration of isometamidium in plasma was highest at 2 wk after injection and then declined. An intramuscular dose of 1.0 mg kg-1 of isometamidium chloride at 1, 2 and 3 wk postinfection (preclinical) significantly reduced the parasitaemia in rainbow trout 2 wk after treatment. A booster at 9 wk postinfection (chronic disease phase) reduced the parasitaemia further in all fish. The packed cell volume in these fish was higher than in infected controls. Treatment at 5, 6, and 7 wk postinfection (acute disease) had no effects and parasitaemias in treated fish were higher than in infected controls; also, anti-Cryptobia salmositica antibodies and titres of complement-fixing antibody were higher in these than in infected controls. Incubation of immune plasma or complement with isometamidium for 3 h did not affect the lytic titres of complement-fixing antibodies nor rainbow trout complement.     

Trypanosoma cruzi: parasitaemia produced in mice does not seem to be related to in vitro parasite-cell interaction

The interaction of Trypanosoma cruzi strains producing subpatent or high parasitaemia in mice with mouse macrophages, Vero and L929 cells was evaluated using tissue culture trypomastigotes. Macrophages were the cells most readily infected while Vero cells presented the highest parasite intracellular multiplication rates. Subpatent strains were equal or more infective than the high parasitaemia. Due to the small number of strains, no correlation could be established between the zymodemes and parasitaemia or parasite-cell interaction in vitro. However parasitaemia in mice does not seem to be related to in vitro parasite-cell interaction.     

gamma delta T-cells may interfere with a productive immune response in Plasmodium yoelii infections.

Mice lacking alpha beta T-cells or gamma delta T-cells were infected with Plasmodium yoelii 17X NL (non-lethal) and followed for parasitaemia and cytokine production. While the parasitaemia in wild type mice resolved after reaching a peak value of 30 to 50%, it persisted in the -alpha beta T-cell mice until death. However, in the -gamma delta T-cell mice the peak parasitaemia was 12.5% of the levels seen in the wild type and -alpha beta T-cell mice and resolved faster than in the wild type mice. Higher levels of IL-10 and IFN-gamma were consistently found in the wild type and -gamma delta T-cell mice but not in the -alpha beta T-cell mice.     

Oral artesunate prevents Plasmodium berghei Anka infection in mice

Artesunate, a semi-synthetic derivative of a naturally occurring anti-malarial artemisinin was compared with chloroquine in C57BL/6 mice infected with Plasmodium berghei Anka (PbA). A 7-day oral administration of artesunate prevented parasitaemia at 10 mg/kg/day. However, recrudescence of parasitaemia and cerebral malaria occurred upon cessation of treatment followed by death within 28 days. However, a 14-day course of artesunate (100 mg/kg/day) prevented completely the development of parasitaemia and cerebral malaria with a survival of more than 60-days as did 10 mg/kg/day chloroquine. These data demonstrate that oral artesunate inhibits PbA and prevents cerebral malaria, but needs to be administered at high dose and for prolonged time to eradicate PbA infection in mice.     

A study on pathogenicity and mosquito transmission success in the rodent malaria parasite Plasmodium chabaudi adami

We investigated the parasitology, pathogenicity (virulence) and infectivity to mosquitoes of blood infections in mice, of two strains, DS and DK, of the rodent malaria parasite Plasmodium chabaudi adami. Blood infections of DS were found to be highly pathogenic; the asexual parasites in these infections were fast-growing and showed no evidence of selectivity in their infection of host erythrocytes. In contrast to DS, blood infections of DK were much less pathogenic; the asexual parasites were slower-growing and showed a moderate degree of selectivity to a subset of erythrocytes which were not reticulocytes. In both DS and DK infections, infectivity to mosquitoes was highest before the peak of asexual parasitaemia had occurred; usually this did not coincide with the time when gametocyte numbers in the blood were highest. Infections with the pathogenic DS strain in CBA mice produced fewer gametocytes than did the less pathogenic DK strain. The DS strain infections in both CBA and C57 mice were also significantly much less infective to mosquitoes than the DK strain. Investigations by others on the related rodent malaria parasite subspecies, Plasmodium chabaudi chabaudi, have indicated that the mosquito infectivity of blood infections in mice tended to be higher in the more pathogenic (virulent) and lower in the less pathogenic strains of this parasite subspecies. This is the converse of the finding of the present investigation of blood infections of P. c. adami in mice in which a more pathogenic, or virulent, strain (DS) of these parasites was significantly much less infective to mosquitoes than was a less pathogenic strain (DK).     

Development of a pharmacodynamic model of murine malaria and antimalarial treatment with dihydroartemisinin

Antimalarial treatment strategies based on in vitro studies are limited by the paucity of pharmacodynamic information for dosage regimen design. We postulated that a murine model could be used for pre-clinical stages of drug development, especially in dose–response studies and evaluation of combination therapies. Swiss mice infected with Plasmodium berghei parasites (2–5% starting parasitaemia) were given dihydroartemisinin (0–100 mg/kg single dose). Parasite density was regularly determined from thin blood films. A parasite population growth model comprising parasite multiplication, decline in erythrocyte count with increasing parasitaemia and parasite clearance after drug administration was developed. This model described the rise in parasitaemia following inoculation, the nadir following dihydroartemisinin administration, and the subsequent resurgence of parasitaemia (analogous to ‘recrudescence’). At doses of 10, 30 and 100 mg/kg dihydroartemisinin, there was a graded response with 2.5 ± 1, 5 ± 1 and 12 ± 4-fold decreases in parasitaemia, respectively. The nadir parasitaemia (at 21–27 h) was also dose-dependent. This study demonstrates that a murine malaria pharmacodynamic model is a valuable tool for understanding how single drugs and their dosing schedules alter the time course and level of infection.     

Impact of the large-scale deployment of artemether/lumefantrine on the malaria disease burden in Africa: case studies of South Africa,Zambia and Ethiopia

Background

Azathioprine triggers suicidal erythrocyte death or eryptosis, characterized by cell shrinkage and exposure of phosphatidylserine at the erythrocyte surface. Eryptosis may accelerate the clearance of Plasmodium -infected erythrocytes. The present study thus explored whether azathioprine influences eryptosis of Plasmodium -infected erythrocytes, development of parasitaemia and thus the course of malaria.

Methods

Human erythrocytes were infected in vitro with Plasmodium falciparum (P. falciparum) (strain BinH) in the absence and presence of azathioprine (0.001 – 10 μM), parasitaemia determined utilizing Syto16, phosphatidylserine exposure estimated from annexin V-binding and cell volume from forward scatter in FACS analysis. Mice were infected with Plasmodium berghei (P. berghei) ANKA by injecting parasitized murine erythrocytes (1 × 10⁶) intraperitoneally. Where indicated azathioprine (5 mg/kg b.w.) was administered subcutaneously from the eighth day of infection.

Results

In vitro infection of human erythrocytes with P. falciparum increased annexin V-binding and initially decreased forward scatter, effects significantly augmented by azathioprine. At higher concentrations azathioprine significantly decreased intraerythrocytic DNA/RNA content (≥ 1 μM) and in vitro parasitaemia (≥ 1 μM). Administration of azathioprine significantly decreased the parasitaemia of circulating erythrocytes and increased the survival of P. berghei -infected mice (from 0% to 77% 22 days after infection).

Conclusion

Azathioprine inhibits intraerythrocytic growth of P. falciparum, enhances suicidal death of infected erythrocytes, decreases parasitaemia and fosters host survival during malaria.     

Trypanosoma cruzi: infection patterns in intact and athymic mice of susceptible and resistant genotypes

Inbred strains of mice inoculated with the T cruzi Y strain behaved as susceptible (A/J, C3H/HeN), intermediate (BALB/c) or relatively resistant (C57BL/6) with respect to the magnitude of parasitaemia and mortality rate. C57BL/10 mice were susceptible in relation to parasitaemia but resistant when mortality was analyzed. Infection with T cruzi CL strain presented the same results, except for C57BL/6 which behaved as susceptible mice. Athymic mice of various backgrounds revealed no differences in susceptibility, presenting the same dramatic parasitaemia, tissue colonization pattern and no inflammatory reaction in any of the tissues studied. Infection of euthymic and athymic BALB/c mice elicited the production of parasite-specific antibodies, which reached similar levels on the first 9 days but differed after day 13. Serum transfer experiments in BALB/c mice did not show great differences in parasitaemia but altered T. cruzi polymorphism reducing the slender forms in athymic mice. Histopathology of athymic BALB/c mice showed the same tissue tropism when infected either with T cruzi Y or CL strain.     

Haemosporidian parasitism in the blackcap Sylvia atricapilla in relation to spring arrival and body condition

Parasites can exert strong selection on hosts. Throughout the year migrants are exposed to different sets of parasites, which may affect life history traits such as migratory schedules. Here, we studied the relationship between parasite infection and arrival date of blackcaps Sylvia atricapilla to their breeding grounds in Germany throughout a period of six years (2007–2012). We used two data sets, one that included all blackcaps and one that included only recaptured birds. We assesed whether parasites influence spring arrival to breeding grounds, and for the recaptured data set, we analysed temporal variation in parasitism (i.e. infection status and parasitaemia) throughout the breeding season. We used both microscopy and PCR (a fragment of ? 479 bp of the mtDNA cyt b) to determine haemosporidian infection. Blackcaps were mostly infected with Haemoproteus parabelopolskyi (lineages SYAT01 and SYAT02). Infection status, but not parasitaemia, was constant through time for individual birds; meaning that once a bird is infected, it most likely will retain the infection for life. We found that infection by haemosporidian parasites has no relationship to arrival date in this blackcap population; however, infection by H. parabelopolskyi has a marginally significant effect on arrival date of recaptured blackcaps, somewhat delaying their arrival to breeding grounds. Birds captured later in the season were more likely to be infected than those from early spring, and parasitaemia was frequently lower in birds captured earlier in the season compared to those captured later (summer).     

Effect of the Aedes fluviatilis saliva on the development of Plasmodium gallinaceum infection in Gallus (gallus) domesticus

Effect of Aedes fluviatilis saliva on the development of Plasmodium gallinaceum experimental infection in Gallus (gallus) domesticus was studied in distinct aspects. Chickens subcutaneously infected with sporozoites in the presence of the mosquito salivary gland homogenates (SGH) showed higher levels of parasitaemia when compared to those ones that received only the sporozoites. However, the parasitaemia levels were lower among chickens previously immunized by SGH or non-infected mosquito bites compared to the controls, which did not receive saliva. High levels of anti-saliva antibodies were observed in those immunized chickens. Moreover, 53 and 102 kDa saliva proteins were recognized by sera from immunized chickens. After the sporozoite challenge, the chickens also showed significant levels of anti-sporozoite antibodies. However, the ability to generate anti-sporozoites antibodies was not correlated to the saliva immunization. Our results suggest that mosquito saliva components enhance P. gallinaceum parasite development in naive chickens. However, the prior exposure of chickens to salivary components controls the parasitemia levels in infected individuals.     

Plasmodium chabaudi: relationship between the occurrence of recrudescent parasitaemias in mice and the effective levels of acquired immunity

In NIH inbred mice infected with the $\text{A}\text{S}$ strain of Plasmodium chabaudi the erythrocytic infection shows an acute primary parasitaemia which becomes subpatent after about 2 weeks. A period (7–10 days) of subpatency follows before a short-lasting patent recrudescence appears. The appearance of the recrudescent parasitaemia was examined in relation to (1) the level of antiplasmodial antibody detected by the indirect fluorescent antibody (IFA) test, (2) the antiparasite activity of the serum measured by the passive protection test, and (3) the ability of the mice to control and eliminate a large intravenous challenge infection. In the period between the primary parasitaemia becoming subpatent and the onset of the recrudescence there was a slight drop in the IFA levels, and a steep decline in passive protective levels and in the ability of the mice to control a large intravenous challenge infection. It is suggested that a decline in the effector arm in the immune response contributes to emergence of the recrudescent parasitaemias.     

Action of adrenalin on the circulation of the murine Plasmodium developing stages, in different blood compartments

Adrenalin was used to investigate in vivo the circulation of the different stages of rodent Plasmodium present in the blood. A single dose of adrenalin injected to mice infected with P. yoelii resulted immediately in i) a diminution of the parasitaemia of approximately 50% in the peripheral large vessels (estimated in tail blood films), as well as in the capillaries (estimated in smears of blood collected from a fed Anopheles), and ii) an increased parasitaemia in blood collected by cardiac puncture from the right heart. The numbers of young stages of P. yoelii in the peripheral blood were initially somewhat reduced but, unexpectedly, midterm trophozoites were preferentially expelled from the peripheral blood into major organs like the heart. With P. vinckei, parasitaemia decreased only when midterm trophozoites predominated, and with P. chabaudi no effect was observed at any time. We propose that midterm trophozoites, by their increased surface area, as compared to rings, and their flexibility which contrasts with the rigid schizonts, are particularly susceptible to haemodynamic perturbations.     

Bayesian Geostatistical Modeling of Malaria Indicator Survey Data in Angola

The 2006–2007 Angola Malaria Indicator Survey (AMIS) is the first nationally representative household survey in the country assessing coverage of the key malaria control interventions and measuring malaria-related burden among children under 5 years of age. In this paper, the Angolan MIS data were analyzed to produce the first smooth map of parasitaemia prevalence based on contemporary nationwide empirical data in the country. Bayesian geostatistical models were fitted to assess the effect of interventions after adjusting for environmental, climatic and socio-economic factors. Non-linear relationships between parasitaemia risk and environmental predictors were modeled by categorizing the covariates and by employing two non-parametric approaches, the B-splines and the P-splines. The results of the model validation showed that the categorical model was able to better capture the relationship between parasitaemia prevalence and the environmental factors. Model fit and prediction were handled within a Bayesian framework using Markov chain Monte Carlo (MCMC) simulations. Combining estimates of parasitaemia prevalence with the number of children under we obtained estimates of the number of infected children in the country. The population-adjusted prevalence ranges from in Namibe province to in Malanje province. The odds of parasitaemia in children living in a household with at least ITNs per person was by 41% lower (CI: 14%, 60%) than in those with fewer ITNs. The estimates of the number of parasitaemic children produced in this paper are important for planning and implementing malaria control interventions and for monitoring the impact of prevention and control activities.     

Some observations of rainbow trout, Salmo gairdneri, Richardson, infected with Cryptobia salmositica

Rainbow trout ( Salmo gairdneri ) were infected with an inoculum of infected blood containing 10⁶ Cryptobia salmositica. Parasitaemia was cyclical with a major peak at 14–21 days and a smaller peak at 42 days. The first peak of parasitaemia was correlated with low glucose, plasma proteins, and haematocrit levels. During this time clinical symptoms (exophthalmia, ascites, pale liver and gills) of the pathogenic condition were observed. The partial disappearance of the parasites from the blood was corrrelated with their appearance in the peritoneal cavity. As plasma glucose, proteins, and haematocrit levels returned towards control values, the oedema and gill paleness declined. Examination of the liver and spleen showed an exudate of fibrous matrix on their exterior surfaces. In addition, the presence of 2–4×10³ mm⁻³ Cryptobia in asymptomatic surviving fish suggests that a chronic parasitaemia can be tolerated.     

Anaplasma marginale: Effect of challenge of cattle with varying doses of infected erythrocytes

Three groups, each of 6 Hereford cattle, were infected by the i.v. inoculation of 10¹⁰, 10⁸ or 10⁶ Anaplasma marginale-infected erythrocytes. The mean time taken to reach a 1% parasitaemia was 7.3, 13.9 and 19.9 days in the 10¹⁰, 10⁸ and 10⁶ infection dose groups, respectively. The rates of increase in parasitaemias during the exponential phase of parasite multiplication were similar for the 3 groups (doubling time 0.9 days). The exponential increase of the parasitaemia in the 10¹⁰ dose group extended to a higher level than in the 10⁸ or 10⁶ dose groups (to approximately 10% compared with 3%). The mean maximum parasitaemia attained in the 10¹⁰, 10⁸ and 10⁶ infection dose groups was 23.7, 14.7 and 8.7%, respectively. The time taken to reach the treatment criterion (packed cell volume decrease to 15% or lower) from a 1% parasitaemia was similar for the 3 groups. These results showed that the pathological outcome (anaemia) of anaplasmosis were similar over the 10 000-fold infective dose range tested.