Vector-borne diseases in a warmer world: Will they stay or will they go?

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Leverikten: en gammel kending i fremgang

Liver flukes are very successful group of parasites that can infect many different hosts including humans. They can be found in different forms and sizes, and found almost all of the world. In Denmark, two species are found. The well-known "common liver fluke" has existed in Denmark since the Vikings, but is increasing again recently. Not so known is "the lancet fluke", which is also fascinating as it can make the ants behave like zombies

Associations between patterns of human intestinal schistosomiasis and snail and mammal species richness in Uganda:can we detect a decoy effect?

In recent years, ecological research has suggested several mechanisms by which biodiversity might affect the risk of acquiring infectious diseases (i.e., the decoy, dilution or amplification effects), but the topic remains controversial. While many experimental studies suggest a negative relationship between biodiversity and disease, this relationship is inherently complex, and might be negative, positive or neutral depending on the geographical scale and ecological context. Here, applying a macroecological approach, we look for associations between diversity and disease by comparing the distribution of human schistosomiasis and biogeographical patterns of freshwater snail and mammal species richness in Uganda. We found that the association between estimated snail richness and human infection was best described by a negative correlation in non-spatial bi- and multivariate logistic mixed effect models. However, this association lost significance after the inclusion of a spatial component in a full geostatistical model, highlighting the importance of accounting for spatial correlation to obtain more precise parameter estimates. Furthermore, we found no significant relationships between mammal richness and schistosomiasis risk. We discuss the limitations of the data and methods used to test the decoy hypothesis for schistosomiasis, and highlight key future research directions that can facilitate more powerful tests of the decoy effect in snail-borne infections, at geographical scales that are relevant for public health and conservation.<br /

Bayesian conditional autoregressive models to assess spatial patterns of diarrhoea risk among children under the age of 5 years in Mbour, Senegal

Diarrhoeal diseases remain a major public health problem, causing more than half a million child deaths every year, particularly in low- and middle-income countries (LMICs). Despite existing knowledge on the aetiologies and causes of diarrhoeal diseases, relatively little is known about its spatial patterns in LMICs, including Senegal. In the present study, data from a cross-sectional survey carried out in 2016 were analysed to describe the spatial pattern of diarrhoeal prevalence in children under the age of 5 years in the secondary city of Mbour in the south-western part of Senegal. Bayesian conditional autoregressive (CAR) models with spatially varying coefficients were employed to determine the effect of sociodemographic, economic and climate parameters on diarrhoeal prevalence. We observed substantial spatial heterogeneities in diarrhoea prevalence. Risk maps, stratified by age group, showed that diarrhoeal prevalence was higher in children aged 25-59 months compared to their younger counterparts with the highest risk observed in the north and south peripheral neighbourhoods, especially in Grand Mbour, Médine, Liberté and Zone Sonatel. The posterior relative risk estimate obtained from the Bayesian CAR model indicated that a unit increase in the proportion of people with untreated stored drinking water was associated with a 29% higher risk of diarrhoea. A unit increase in rainfall was also associated with an increase in diarrhoea risk. Our findings suggest that public health officials should integrate disease mapping and cluster analyses and consider the varying effects of sociodemographic factors in developing and implementing areaspecific interventions for reducing diarrhoea

Lymphatic filariasis control in Tanga Region, Tanzania:status after eight rounds of mass drug administration

BackgroundLymphatic filariasis (LF) control started in Tanga Region of Tanzania in 2004, with annual ivermectin/albendazole mass drug administration (MDA). Since then, the current project has monitored the effect in communities and schools in rural areas of Tanga District. In 2013, after 8 rounds of MDA, spot check surveys were added in the other 7 districts of Tanga Region, to assess the regional LF status.MethodsLF vector and transmission surveillance, and human cross sectional surveys in communities and schools, continued in Tanga District as previously reported. In each of the other 7 districts, 2¿3 spot check sites were selected and about 200 schoolchildren were examined for circulating filarial antigens (CFA). At 1¿2 of the sites in each district, additional about 200 community volunteers were examined for CFA and chronic LF disease, and the CFA positives were re-examined for microfilariae (mf).ResultsThe downward trend in LF transmission and human infection previously reported for Tanga District continued, with prevalences after MDA 8 reaching 15.5% and 3.5% for CFA and mf in communities (decrease by 75.5% and 89.6% from baseline) and 2.3% for CFA in schoolchildren (decrease by 90.9% from baseline). Surprisingly, the prevalence of chronic LF morbidity after MDA 8 was less than half of baseline records. No infective vector mosquitoes were detected after MDA 7. Spot checks in the other districts after MDA 8 showed relatively high LF burdens in the coastal districts. LF burdens gradually decreased when moving to districts further inland and with higher altitudes.ConclusionLF was still widespread in many parts of Tanga Region after MDA 8, in particular in the coastal areas. This calls for intensified control, which should include increased MDA treatment coverage, strengthening of bed net usage, and more male focus in LF health information dissemination. The low LF burdens observed in some inland districts suggest that MDA in these could be stepped down to provide more resources for upscale of control in the coastal areas. Monitoring should continue to guide the programme to ensure that the current major achievements will ultimately lead to successful LF elimination