Evaluation of ivermectin mass drug administration for malaria transmission control across different West African environments.

BACKGROUND: Mass drug administration (MDA) of ivermectin to humans for control and elimination of filarial parasites can kill biting malaria vectors and lead to Plasmodium transmission reduction. This study examines the degree and duration of mosquitocidal effects resulting from single MDAs conducted in three different West African countries, and the subsequent reductions in parity and Plasmodium sporozoite rates. METHODS: Indoor-resting, blood-fed and outdoor host-seeking Anopheles spp. were captured on days surrounding MDAs from 2008-2013 in Senegalese, Liberian and Burkinabé villages. Mortality was assessed on a portion of the indoor collection, and parity status was determined on host-seeking mosquitoes. The effect of MDA was then analysed against the time relative to the MDA, the distributed drugs and environmental variables. RESULTS: Anopheles gambiae survivorship was reduced by 33.9% for one week following MDA and parity rates were significantly reduced for more than two weeks after the MDAs. Sporozoite rates were significantly reduced by >77% for two weeks following the MDAs in treatment villages despite occurring in the middle of intense transmission seasons. These observed effects were consistent across three different West African transmission dynamics. CONCLUSIONS: These data provide a comprehensive and crucial evidence base for the significant reduction in malaria transmission following single ivermectin MDAs across diverse field sites. Despite the limited duration of transmission reduction, these results support the hypothesis that repeated MDAs with optimal timing could help sustainably control malaria as well as filarial transmission.

Assessment of Culicidae collection methods for xenomonitoring lymphatic filariasis in malaria co-infection context in Burkina Faso.

BACKGROUND: Entomological surveillance of lymphatic filariasis and malaria infections play an important role in the decision-making of national programs to control, or eliminate these both diseases. In areas where both diseases prevalence is low, a large number of mosquitoes need to be sampled to determine vectors infection rate. To do this, efficient mosquito collection methods must be used. This study is part in this framework, to assess appropriate mosquito collection methods for lymphatic filariasis xenomonitoring in a coexistence context with malaria in Burkina Faso. METHODOLOGY/PRINCIPAL FINDINGS: Mosquito collections were performed between August and September 2018 in four villages (Koulpissi, Seiga, and Péribgan, Saptan), distributed in East and South-West health regions of Burkina Faso. Different collection methods were used: Human Landing Catches (HLC) executed indoor and outdoor, Window Exit-Trap, Double Net Trap (DNT) and Pyrethrum Spray Catches (PSC). Molecular analyses were performed to identify Anopheles gambiae s.l. sibling species and to detect Wuchereria bancrofti and Plasmodium falciparum infection in Anopheles mosquitoes. A total of 3 322 mosquitoes were collected among this, Anopheles gambiae s.l. was the vector caught in largest proportion (63.82%). An. gambiae s.l. sibling species molecular characterization showed that An. gambiae was the dominant specie in all villages. The Human Landing Catches (indoor and outdoor) collected the highest proportion of mosquitoes (between 61.5% and 82.79%). For the sampling vectors infected to W. bancrofti or P. falciparum, PSC, HLC and Window Exit-Trap were found the most effective collection methods. CONCLUSIONS/SIGNIFICANCE: This study revealed that HLC indoor and outdoor remained the most effective collection method. Likewise, the results showed the probability to use Window Exit-Trap and PSC collection methods to sample Anopheles infected.

Baseline drivers of lymphatic filariasis in Burkina Faso.

Lymphatic filariasis (LF) is a parasitic disease that is endemic throughout sub-Saharan Africa, infecting approximately 40 million people. In Burkina Faso, mass drug administration (MDA) for LF with ivermectin and albendazole has been ongoing since 2001, and by 2006 all endemic health districts were receiving MDA with a therapeutic coverage of at least 65%. As MDA activities scale down, the focus is now on targeting areas where LF transmission persists with alternative elimination strategies. This study explored the relationship between village-level, baseline LF prevalence data collected in 2000 with publicly available meteorological, environmental and demographic variables in order to determine the factors that influence the geographical distribution of the disease. A fitted multiple logistic regression model indicated that the length of the rainy season, variability in normalized difference vegetation index (NDVI) and population density were significantly positively associated with LF prevalence, whereas total annual rainfall, average June-September temperature, mean NDVI, elevation and the area of cotton crops were significantly negatively associated. This model was used to produce a baseline LF risk map for Burkina Faso. An extended model which incorporated potential socio-demographic risk factors also indicated a significant positive relationship between LF prevalence and wealth. In overlaying the baseline LF risk map with the number of MDA rounds, plus an insecticide-treated net (ITN) ownership measure, the central southern area of the country was highlighted as an area where baseline LF prevalence was high and ITN coverage relatively low (<50%), while at least 10 rounds of MDA had been undertaken, suggesting that more concentrated efforts will be needed to eliminate the disease in these areas.

Efficacy of home-based lymphoedema management in reducing acute attacks in subjects with lymphatic filariasis in Burkina Faso.

One of the two main goals of the Global Programme to Eliminate Lymphatic Filariasis (LF) is to provide care for those suffering from the devastating clinical manifestations of this filarial infection. Among the 120 million infected people worldwide, up to 16 million have lymphoedema. The WHO strategy for managing lymphoedema is based on rigorous skin hygiene, exercise, antibiotics and antifungals when indicated. The aim is to reduce acute attacks of adenolymphangitis and cellulitis responsible for lymphoedema progression and disability. The objective of our study was to assess the effectiveness of home-based lymphoedema management implemented by the national health system of Burkina Faso. Any patient was eligible to participate in the study if suffering from LF-related lymphoedema of a lower limb at any stage, and receiving care as part of the health education and washing project between April 2005 and December 2007. The primary readout was the occurrence of an acute attack in the month preceding the consultation reported by the patient or observed by the care-giver. In all, 1089 patients were enrolled in the study. Before lymphoedema management intervention, 78.1% (95%CI: 75.5-80.5) of the patients had an acute attack in the month preceding the consultation; after four and half months of lymphoedema management, this was reduced to 39.1% (95%CI: 36.2-42.1). A reduction of acute attacks related to the number of consultations or related to the patients' age and gender was not observed. Our results suggest that the home-based lymphoedema management programme in the primary health care system of Burkina Faso is effective in reducing morbidity due to LF in the short-term (4.5 months). The lymphoedema management requires no additional human resources, but whether its effect can be sustained remains to be seen.