Investigating the genetic load of an emblematic invasive species: the case of the invasive harlequin ladybird Harmonia axyridis.

Introduction events can lead to admixture between genetically differentiated populations and bottlenecks in population size. These processes can alter the adaptive potential of invasive species by shaping genetic variation, but more importantly, they can also directly affect mean population fitness either increasing it or decreasing it. Which outcome is observed depends on the structure of the genetic load of the species. The ladybird Harmonia axyridis is a good example of invasive species where introduced populations have gone through admixture and bottleneck events. We used laboratory experiments to manipulate the relatedness among H. axyridis parental individuals to assess the possibility for heterosis or outbreeding depression in F1 generation offspring for two traits related to fitness (lifetime performance and generation time). We found that inter-populations crosses had no major impact on the lifetime performance of the offspring produced by individuals from either native or invasive populations. Significant outbreeding depression was observed only for crosses between native populations for generation time. The absence of observed heterosis is indicative of a low occurrence of fixed deleterious mutations within both the native and invasive populations of H. axyridis. The observed deterioration of fitness in native inter-population crosses most likely results from genetic incompatibilities between native genomic backgrounds. We discuss the implications of these results for the structure of genetic load in H. axyridis in the light of the available information regarding the introduction history of this species.

Experimental evidence for the phenotypic impact of admixture between wild and biocontrol Asian ladybird (Harmonia axyridis) involved in the European invasion.

Hybridization can fuel evolutionary processes during biological invasions. The harlequin ladybird Harmonia axyridis has long been used as a biocontrol agent before the species became invasive worldwide. Previous analysis based on microsatellite data has shown that European invasive populations bear traces of admixture between an eastern North American source, which is at the origin of the worldwide invasion, and biocontrol strains used in Europe. In this study, we tested the hypothesis that this early admixture event may have fostered the European invasion by impacting on the phenotypes of wild European populations. Mean life history traits of experimental F(1) hybrids are compared with pure parental sources and wild European crosses. Our results reveal a biased impact whereby North American beetles benefitted from being admixed with European biocontrol strains. Resemblance between experimental hybrids and wild European invasive crosses further suggests a long-lasting effect of admixture that may still be at work and fostering invasiveness.

Dracunculiasis eradication.

Dracunculiasis is a disease caused by a parasite transmitted through infected drinking water. The International Drinking Water Supply and Sanitation Decade (1981-1990), provided a unique opportunity to eliminate the disease. The strategy of the eradication campaign was based on provision of safe drinking water supply, intensified case containment and health education. An appropriate epidemiological surveillance system was established to guide and evaluate the eradication effort. From an estimated 3.2 million people affected by the disease at the beginning of the campaign, the number of cases dropped to 10,674 by the end of year 2005. Currently the transmission of the disease takes place in 9 sub-Saharan countries only and another 7 countries are in the pre-certification stage. So far, 168 countries and territories have been certified free of transmission. However; eradication of the disease requires that all countries be certified free of transmission. With the support of the international community and the work of national dracunculiasis eradication programmes of affected countries, dracunculiasis may well be the first parasitic disease to be eradicated.

Reversal of impaired calcium homeostasis in the rat diaphragm subjected to Monocrotaline-induced pulmonary hypertension.

Monocrotaline (MCT) pneumotoxicity is known to alter the structure of pulmonary vascular wall and impairs endothelial cell function resulting in pulmonary hypertension. Its effect on the diaphragm muscle has not yet been elucidated. This study examines the effect of MCT pneumotoxicity on calcium transport in the rat diaphragm. Pulmonary hypertension induced by MCT pneumotoxicity caused a significant increase (P < 0.001) in calcium accumulation in strips isolated from rat diaphragms. Treatment of rats having received MCT with Indapamide reduced calcium uptake by diaphragmatic strips to levels that are not significantly different from the control (P > 0.05). Treatment with Indapamide alone did not elicit any change in calcium accumulation in the diaphragmatic strips. Treatment of the animals with MCT, Indapamide or both did not produce any significant change (P > 0.05) in the cell volume of the diaphragmatic strips. Pulmonary hypertension increased calcium uptake by the muscle cells in the rat diaphragm which may alter diaphragmatic contractility; an effect that was prevented by Indapamide.

Twenty years of cutaneous leishmaniasis in Aleppo, Syria.

Cutaneous leishmaniasis caused by Leishmania tropica has long been associated with Aleppo in Syria. For 20 years up to the mid-1980s, the number of cases reported annually in the city and environs has remained low, not exceeding a few hundred. Since then, there has been a sudden increase to several thousand cases reported each year. The increase seems too great and too sudden to be attributable to improved case detection. Insecticide spraying, begun in 1991, was followed by a reduction in number of cases in 1992, but numbers increased subsequently in spite of continued spraying. The cases are found mainly in areas undergoing development outside the old centre of the city, and may be associated with poor waste disposal and heaps of construction waste.

The impact of health education to promote cloth filters on dracunculiasis prevalence in the northern region, Ghana.

This paper describes a health education intervention which was conducted during the 1990 dry season in 3 study villages in the Northern Region of Ghana, to reduce dracunculiasis prevalence in that area by promoting the use of cloth filters for drinking water and avoidance of water contact by sufferers. The impact of the intervention in reducing dracunculiasis prevalence was examined by comparing the period prevalence of infection in 1990 and 1991. The findings demonstrate that the intervention had a measurable but limited impact on dracunculiasis prevalence. Face-to-face health education was successful in persuading 56% of households to buy filters. Ownership of at least one filter for every 10 people in the household was associated with a reduction of at least 20% in the risk of dracunculiasis.

The impact of dracunculiasis on the nutritional status of children in South Kordofan, Sudan.

This paper assesses the indirect impact of dracunculiasis on the nutritional status of children under 6 years of age in South Kordofan, Sudan. Weight-for-height anthropometric measurement was used as a measure of the nutritional status of 774 children in 428 households. The indirect impact was investigated by comparing the nutritional status in 1988 of children in 'affected' households, where more than half the adult members had suffered from dracunculiasis in 1987, with children in other households. It was anticipated that when the otherwise able adult members of a households had dracunculiasis they were likely to be disabled by the disease and so prevented from fully performing their agricultural activities, so that the nutritional status of children in the same household would deteriorate in the following year. It was found that in 16.9% of the 136 'affected' households the children were wasted (with mean Z-scores of -2 or less), compared with only 6% of the other households.

The public and domestic domains in the transmission of disease.

This paper discusses the distinction between the transmission of infectious diseases within the domestic domain (the area normally occupied by and under the control of a household) and that in the public domain, which includes public places of work, schooling, commerce and recreation as well as the streets and fields. Whereas transmission in the public domain can allow a single case to cause a large epidemic, transmission in the domestic domain is less dramatic and often ignored, although it may account for a substantial number of cases. Statistical methods are available to estimate the relative importance of the two. To control transmission in the public domain, intervention by public authorities is likely to be required. Two examples show how environmental interventions for disease control tend to address transmission in one or the other domain; interventions are needed in both domains in order to interrupt transmission.

The reliability of retrospective studies using a one-year recall period to measure dracunculiasis prevalence in Ghana.

BACKGROUND: Cross-sectional studies are usually adopted to assess the one-year period prevalence of dracunculiasis. They depend upon a recall period of up to one year. This paper aims to examine the degree of accuracy with which villagers in an endemic region recall the occurrence of dracunculiasis during the 12 months prior to a cross-sectional survey. METHODS: Two types of study were conducted in Tolon, a village in Northern Ghana--retrospective and prospective. Data from people interviewed in a bimonthly survey throughout 1990 were compared with the results of a cross-sectional retrospective study conducted in early 1991. RESULTS: The results showed that retrospective studies using a recall period of up to one year to measure dracunculiasis prevalence gave only 59.9% of the actual cases, but there were roughly equal numbers of 'false positive' and 'false negative' cases, so that overall prevalence obtained was very close to the correct figure. CONCLUSIONS: Cross-sectional surveys may be of use to obtain estimates of the one-year period prevalence of dracunculiasis, but are not likely to be reliable enough for more detailed study.

PIP: Cross-sectional studies are usually used to assess the one-year period prevalence of dracunculiasis. The authors assessed the degree of accuracy with which villagers in an endemic region recall the occurrence of dracunculiasis during the 12 months prior to such a cross-sectional survey. The study was conducted in Tolon, a village in Northern Ghana, using both retrospective and prospective studies. Data from people interviewed in a bimonthly survey throughout 1990 were compared with the results of a cross-sectional retrospective study conducted in early 1991. The authors determined that retrospective studies using a recall period of up to one year to measure dracunculiasis prevalence gave only 59.9% of the actual cases. However, since there were almost equal numbers of false positive and false negative cases, the overall resultant prevalence obtained was very close to the correct figure. It seems that cross-sectional surveys may be adequate to obtain estimates of the one-year period prevalence of dracunculiasis, but they are unlikely to be reliable enough for more detailed study.

Water sources and other determinants of dracunculiasis in the northern region of Ghana.

This paper describes a study carried out in a rural area of Ghana on the drinking water sources and other determinants of dracunculiasis (guinea worm disease). The results confirm the association between water source choice and the prevalence of the disease. A logistic regression model was used to show the combined effect of several behavioural, biological, and environmental risk factors. The important behavioural factors were related to the head of household, fetching of water, travelling, and farming. Age was found to be an important biological risk factor for dracunculiasis, but the greatest relative risk applied to those who had suffered from guinea worm disease in the previous year. Although males were significantly more infected than females when analysing the raw data, sex did not prove to be a significant risk factor in this model. Village of residence was an important environmental risk factor for dracunculiasis. Factors related to socio-economic status were not associated with the risk of infection. The paper concludes by presenting the policy implications of the study findings.