Biomedical subjects

L Molineaux

Publications and source records attributed to L Molineaux.

25 records · Page 2Linked to original sources

PubMed1978

Longitudinal serological study of malaria in infants in the West African savanna. Comparisons in infants exposed to, or protected from, transmission from birth.

Two infant populations, the one exposed to intense malaria transmission and the other protected, were followed and compared by six serological tests. The IgG and IgM levels increased with age and were systematically, though only slightly, lower in the protected children. The results of three Plasmodium falciparum tests (precipitin, indirect fluorescent antibody (IFA) and indirect haemagglutination and one P. malariae test (IFA) were high at birth and decreased rapidly afterwards in both populations. In the unprotected population, this decrease was followed by an increase, closely associated with the parasitological findings, while in the protected population the decrease continued to very low levels.

Africa, Western↗

PubMed1978

Changing patterns in the humoral immune response to malaria before, during, and after the application of control measures: a longitudinal study in the West African savanna.

A longitudinal seroimmunological investigation of malaria was performed as part of the WHO research project conducted in the northern part of Nigeria from 1970 to 1975. The project included a preintervention phase, an intervention phase with application of malaria control measures (spraying of residual insecticide and mass drug administration), and a postintervention phase. Serological observations were made on the total population of eight villages consisting of approximately 3000 persons. Six immunological parameters were studied, namely, the serum levels of IgG and IgM, the number of bands of precipitation for Plasmodium falciparum in the double diffusion (Ouchterlony) test, the titres of antibodies for P. falciparum and P. malariae in the indirect fluorescent antibody (IFA) test, and the titres of agglutinating antibodies for P. falciparum by the indirect (passive) haemagglutination (IHA) test. The serological results were used to evaluate the impact on the humoral immune response of different levels of parasitaemia resulting, in the unprotected population, from natural factors such as seasons and ageing and in the protected population, from human intervention through the application of control measures and their interruption. The linkage by computer processing of the longitudinal data allowed analysis of the relationship between the results of a serological test in the same person at different surveys, and analysis of correlation between serological results and the concurrent parasitological findings. The correlation between parasitaemia and the results of the different serological tests at the same survey in the same person were also examined and analysed in terms of sensitivity and specificity of the tests.

Adolescent↗

PubMed1976

The impact of propoxur on Anopheles gambiae s.1. and some other anopheline populations, and its relationship with some pre-spraying variables.

A significant and stable difference in the residual night-biting collection (NBC, observed/expected) of A. gambiae s.l. was observed among different villages of the West African savannah when sprayed for 2 years with propoxur. The residual mosquito density of a given village was positively associated with some of its pre-spraying characteristics: the NBC/PSC (pyrethrum spray collections) ratio, the median biting hour, and possibly the proportion of species B. It was not significantly associated with several other pre-spraying characteristics (absolute mosquito density, the ratios between NBC indoors and NBC outdoors, between ETC (exit-trap collections) and PSC, between fed and gravid in the PSC or ETC, between males and females in the PSC), and was not associated with variations in recorded coverage, with latitude, or with distance from unsprayed villages.In a comparison between A. gambiae s.l., A. funestus, and A. pharoensis, the residual NBC (observed/expected) was positively associated with the pre-spraying NBC/PSC ratio, and was negatively associated with the median biting hour.The pre-spraying NBC/PSC ratio thus appears to be a predictor of the variation, between villages or species, in the reduction of the NBC by residual spraying, and may assist in forecasting the effect of a residual insecticide. The limitations of any absolute prediction must, however, be kept in mind.

Animals↗

PubMed1976

Estimation of incidence and recovery rates of Plasmodium falciparum parasitaemia from longitudinal data.

A method is described of estimating the malaria incidence rate ĥ and the recovery rate r from longitudinal data. The method is based on the assumption that the phenomenon of patent parasitaemia can be represented by a reversible two-state catalytic model; it is applicable to all problems that can be represented by such a model.The method was applied to data on falciparum malaria from the West African savanna and the findings suggested that immunity increases the rate of recovery from patent parasitaemia by a factor of up to 10, and also reduces the number of episodes of patent parasitaemia resulting from one inoculation. Under the effect of propoxur, ĥ varies with the estimated man-biting rate of the vector while r increases, possibly owing to reduced super-infection.

Adolescent↗

PubMed1974

A malaria model tested in the African savannah.

A new mathematical model of malaria has been developed for comparing the effects of alternative control measures. It describes both the temporal changes of the P. falciparum infection rate and the immunity level of the population as a function of the dynamics and characteristics of the vector populations, which are summarized in the concept of vectorial capacity. A critical vectorial capacity is specified, below which malaria cannot maintain itself at an endemic level. The model has been tested with epidemiological data collected in a WHO research project in the African Savannah, Kano State, Northern Nigeria, since October 1970. The estimates of the model parameters were obtained by minimizing the chi(2) function that measures the discrepancy between the observed and expected age-specific parasite rates in the two villages with the highest and the lowest vectorial capacity, respectively, at five surveys during one year of baseline data collection and between the observed and expected infant inoculation rates, in the main transmission seasons, in the same two villages. The model describes three aspects of immunity: loss of infectivity, loss of detectability, and increase of recovery rate. It is assumed that loss of infectivity precedes loss of detectability and increase of recovery rate. Superinfections are slowing down the recovery for high inoculation rates but do not reduce them to zero. They do not increase infectivity.

Adolescent↗

PubMedDate not supplied

Genesis, sequestration and survival of Plasmodium falciparum gametocytes: parameter estimates from fitting a model to malariatherapy data.

Plasmodium falciparum malaria is one of mankind's main killers. Part of the parasite's life-cycle is spent in human blood, mainly as asexual stages. A fraction of the asexual parasites develops into gametocytes (gamete precursors) while sequestered in deep tissues. After re-entering the circulation, gametocytes can be picked up by a mosquito to continue the parasite's life-cycle. We present estimates of the conversion probability from asexual parasites to circulating gametocytes and of the gametocytes' sequestration and circulation times, obtained for the first time by fitting a dynamic model to individual patients' histories (daily records of 113 neurosyphilitic patients undergoing malariatherapy). The model assumes that the conversion probability can vary among the successive waves of asexual parasitaemia of a patient, and that gametocytes die at an age-dependent rate which increases under high asexual parasite densities. On average, 1 gametocyte per 156 asexual parasites (range 7.4-3700) is produced. The most remarkable findings are the large individual variation of conversion probabilities and circulation times, the average gametocyte circulation time of 6.4 days (range 1.3-22.2 days) which is more than twice the currently accepted value, and the large variation of conversion probabilities among successive waves of asexual parasitaemia without any particular time pattern. The latter finding could be explained by an association between conversion probability and variation of PfEMP1.

Animals↗

PubMedDate not supplied

Malaria therapy reinoculation data suggest individual variation of an innate immune response and independent acquisition of antiparasitic and antitoxic immunities.

Malaria therapy reinoculation data were examined for the possible detection of effects attributable to stable individual host-specific factors, through correlation between descriptive variables of first and second infections. Such an effect was demonstrated with respect to the first local maximum of the asexual parasite density, i.e., the density at which a host controls parasite growth. The effect was seen between an individual host's first and second Plasmodium falciparum infection, as well as between an individual host's first malaria infection with P. ovale and second malaria infection with P. falciparum. We give reasons to believe that the main underlying mechanism is individual variation of an innate immune response. The data were also examined for systematic changes from first to second P. falciparum infection, as indicators of acquired immunity. In addition to the well-known reduction in parasite density, the data show the early development of apparent parasite tolerance. We give reasons to interpret the latter as antitoxic immunity.

Animals↗