Plasmodium knowlesi and human malaria parasites in Khan Phu, Vietnam: Gametocyte production in humans and frequent co-infection of mosquitoes.

Four species of malaria parasite, Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium knowlesi infect humans living in the Khanh Phu commune, Khanh Hoa Province, Vietnam. The latter species also infects wild macaque monkeys in this region. In order to understand the transmission dynamics of the three species, we attempted to detect gametocytes of the three species in the blood of infected individuals, and sporozoites in the salivary glands of mosquitoes from the same region. For the detection of gametocyte-specific mRNA, we targeted region 3 of pfg377, pvs25, pmg and pks25 as indicators of the presence of P. falciparum, P. vivax, P. malariae and P. knowlesi gametocytes, respectively. Gametocyte-specific mRNA was present in 37, 61, 0 and 47% of people infected with P. falciparum (n = 95), P. vivax (n = 69), P. malariae (n = 6) or P. knowlesi (n = 32), respectively. We found that 70% of mosquitoes that had P. knowlesi in their salivary glands also carried human malaria parasites, suggesting that mosquitoes are infected with P. knowlesi from human infections.

Malaria transmission and major malaria vectors in different geographical areas of Southeast Asia.

During the last decade, major progress in malaria control has been achieved in Vietnam, Laos and Cambodia. However, malaria is still a potentially fatal disease in some hilly-forested areas and continues to be endemic in a few coastal foci. To estimate the risk that stems from the major vectors after a decade of intensive malaria control, an entomological study based on human landing collections was conducted between April 1998 and November 2000 in six study villages (four in Vietnam, one in Cambodia and one in Laos) located in different physio-geographical areas. Five villages were selected in places where new cases of malaria still occurred. In the sixth village, in the northern hilly area of Vietnam, no case of malaria was detected during the past 3 years. In three study villages of the hilly forested areas of Cambodia and central Vietnam, Anopheles dirus A still played an important role in malaria transmission and maintain perennial transmission inside the villages despite its low density. Anopheles minimus A was found in all study villages except in the southern coastal village of Vietnam. Its role in malaria transmission, however, varied between localities and surveys. In one study village of central Vietnam it was almost absent (one specimen collected over 480 man nights), and in another village sporozoite positive specimens (2.8%) were only observed during the first two surveys whereas this species disappeared from the collections from November 1998 onwards (six surveys: 360 man nights). In the northern study site An. minimus A and C were found in all collections, but no local malaria transmission occurred. However, the constant presence of these two species associated with a high longevity (parous rate up around 80% and 65%, respectively), suggests that transmission can occur at almost any time if parasite reservoirs are reintroduced in the area. The proper management of malaria cases and population movement is, therefore, important to prevent outbreaks and the reintroduction of malaria in northern Vietnam. In the study site of the Mekong delta, An. sundaicus occurred at high densities (up to 190 bites/man/night). The recent changes in land use from rice cultivation to shrimp farming probably explains the increase of this brackish water breeding species during the study period. However, none of the 11,002 specimens was positive for Plasmodium circumsporozoite protein (CSP). The relative low survival rate as estimated by the parous rate (around 47%) may reflect its low vectorial status that could explain the very low malaria incidence (1.9 case/100 persons/year) in this study site. A calculated sporozoite rate of maximum 1/300,000 is enough to explain this low malaria incidence. Despite the successes in malaria control, the vector An. dirus A continues to play an important role in malaria transmission, whereas An. minimus A showed temporal and spatial variation in its role as vector. The role of An. sundaicus as vector could not be confirmed because of the low incidence in the coastal study village. Other Anopheles species may be locally involved, but in the five study villages where malaria is still present they probably do not contribute significantly to malaria transmission. The study also points towards the fact that in Southeast Asia it will become increasingly difficult to incriminate Anopheles species in malaria transmission while the risk for malaria transmission still persist.

[Interpretation of the values of urinary cotinine in smokers and non-smokers]. / Interprétation des valeurs de la cotininurie chez les fumeurs et les non-fumeurs.

The values of urinary cotinine measured using high performance liquid chromatography in 125 adults (44 men and 81 women) were compared with the degree of intoxication and/or exposure to tobacco experienced over six consecutive days by auto-questionnaire. The subjects were classified in 6 groups: non exposed non smokers and non smokers exposed for less than one hour (1, n = 16); non smokers exposed for between 1 and 10 hours (2, n = 26); non smokers exposed for more than 10 hours and less than 30 hours (3, n = 33); non smokers exposed for more than 30 hours (4, n = 13); smokers smoking less than 20 cigarettes per day (5, n = 16); smokers smoking 20 cigarettes or more per day (6, n = 21). The measurements were made on urine specimens from the first morning (fraction F1), from the day and night (F2) and those of the second morning (F3). The results were expressed in micrograms/fraction and were as follows: Group 1: 37.3 (F1); 149.5 (F2); 26.8 (F3)--Group 2: 81.2; 234.1; 75.4--Group 3: 121.1; 383.1; 80.7--Group 4: 98.8; 253.7; 117.2--Group 5: 206.9; 773.8; 188--Group 6: 483.1; 1908.2; 431.3. Cotinine was found in all individuals whether they declared that they were exposed or non exposed (with the exception of a single person amongs the latter). In spite of a certain amount of overlapping between the results of the individuals in groups 4 and 5, the values obtained enabled a differentiation between the degrees of tobacco absorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma fibronectin depletion after cardiac surgery in children with or without cardiopulmonary bypass.

Plasma fibronectin depletion decreases resistance to sepsis. After cardiac surgery, septic complications occur more frequently when the surgical procedure is managed with a cardio-pulmonary bypass than when it is not. To determine whether cardio-pulmonary bypass produces a greater decrease in plasma fibronectin than surgery without cardio-pulmonary bypass, we studied plasma fibronectin concentrations in two groups of children operated for congenital heart diseases. Group I: 10 children undergoing surgery with cardio-pulmonary bypass. Group II: 11 children undergoing surgery without cardio-pulmonary bypass. Plasma fibronectin was monitored pre-operatively (t 1) and post-operatively at the 6th hour (t 2), 1st (t 3) and 7th (t 4) days. In both groups, plasma fibronectin concentration dropped at (t 2) and (t 3) and rose again at (t 4). There was no significant difference in plasma fibronectin levels between the two groups at any time. We conclude that the plasma fibronectin decline alone cannot explain why septic complications after surgery are more frequent with cardio-pulmonary bypass than without.

Polyacrylamide gel electrophoresis in quantification of high-density lipoprotein cholesterol.

We evaluated a method for quantifying high-density lipoprotein cholesterol in plasma, based on electrophoretic migration of the prestained (with Sudan Black III) sample through a discontinuous polyacrylamide++ gel and densitometric integration of the stain associated with each class of lipoprotein. With this method, operations can be carried out on all types of lipoproteins over a broad range of concentrations. Overloading with very-low and low-density lipoproteins did not affect reliability within a wide range of HDL concentrations (0.45 to 16.60 mmol/L). Results for 22 individual plasma samples from normal and dyslipemic subjects correlated well with those by ultracentrifugal analysis (r=0.96; Student's t= 0.90, p > 0.30). We conclude that this method is reliable, sensitive, and accurate, It may be used for simultaneously typing dyslipoproteinemias and assaying HDL cholesterol.