Enhanced passive screening and diagnosis for gambiense human African trypanosomiasis in north-western Uganda - Moving towards elimination.

INTRODUCTION: The incidence of gambiense human African trypanosomiasis (gHAT) in Uganda has been declining, from 198 cases in 2008, to only 20 in 2012. Interruption of transmission of the disease by early diagnosis and treatment is core to the control and eventual elimination of gHAT. Until recently, the format of available screening tests had restricted screening and diagnosis to central health facilities (passive screening). We describe a novel strategy that is contributing to elimination of gHAT in Uganda through expansion of passive screening to the entire population at risk. METHODOLOGY / PRINCIPAL FINDINGS: In this strategy, patients who are clinically suspected of having gHAT at primary health facilities are screened using a rapid diagnostic test (RDT), followed by parasitological confirmation at strategically located microscopy centres. For patients who are positive with the RDT and negative by microscopy, blood samples undergo further testing using loop-mediated isothermal amplification (LAMP), a molecular test that detects parasite DNA. LAMP positive patients are considered strong suspects, and are re-evaluated by microscopy. Location and upgrading of facilities to perform microscopy and LAMP was informed by results of georeferencing and characterization of all public healthcare facilities in the 7 gHAT endemic districts in Uganda. Three facilities were upgraded to perform RDTs, microscopy and LAMP, 9 to perform RDTs and microscopy, and 200 to screen patients with RDTs. This reduced the distance that a sick person must travel to be screened for gHAT to a median distance of 2.5km compared to 23km previously. In this strategy, 9 gHAT cases were diagnosed in 2014, and 4 in 2015. CONCLUSIONS: This enhanced passive screening strategy for gHAT has enabled full coverage of the population at risk, and is being replicated in other gHAT endemic countries. The improvement in case detection is making elimination of the disease in Uganda an imminent possibility.

Assessing the impact of a novel strategy for delivering animal health interventions to smallholder farmers.

In many countries of the developing world village poultry play a vital role in the rural economy, providing a source of protein and valuable income with relatively small investments. In almost all areas in which village poultry are raised Newcastle disease (ND) is identified as one of the biggest causes of poultry loss, this is often coupled with a lack of knowledge of poultry management practices. Inexpensive and effective vaccines are available that are suitable for use in rural village environments, but in many areas service providers and reliable structures for delivery remain an obstacle to uptake of vaccines. To overcome this, GALVmed has implemented a network for vaccine distribution in which individuals in the villages are trained as vaccinators. The vaccinators purchase ND vaccines from local agro-veterinary stores and sell single doses at market determined prices. Implementation of these networks was preceded by a programme of smallholder sensitisation to increase awareness of diseases and flock management practices. Here we present analysis of the impacts of this scheme on village poultry production. We compare the results of a baseline survey carried out before implementation of the networks, with the results of a survey 16-24 months following implementation. We present results in terms of the uptake of ND vaccine, flock size, consumption of poultry meat, and poultry sales from Gairo district in Tanzania, Mayurbhanj district in India and Banke district in Nepal. In all areas, there was a significant increase in the numbers of flocks that were using ND vaccines, with over 75% uptake in all areas, reaching 98% in India. In all areas flock sizes doubled, the numbers of eggs that were set for hatching and that hatched increased by 25-50% and there was an increase in the frequency with which chicken meat was consumed and chickens were sold. Additionally, farmers reported fewer ND outbreaks, but this is prone to reporting bias and so improvements in production cannot be categorically ascribed to ND vaccination. These results have shown that establishing a market driven approach for the distribution of ND vaccines and community sensitisation on poultry husbandry practices results in a high rate of uptake of the vaccines. The results also suggest a reduction in the number of ND outbreaks and improvements to the livelihoods of rural smallholders.

Improved detection of Trypanosoma brucei by lysis of red blood cells, concentration and LED fluorescence microscopy.

Confirmatory diagnosis of African trypanosomiasis relies on demonstration of parasites in body fluids by bright field microscopy. The parasitaemia in infected patients and animals is usually low, and concentration methods are used to try and increase the chances of seeing parasites. Recently, fluorescence microscopes using light-emitting diodes (LED) have been developed. Since they emit strong light, their use does not require a dark room, making field application a possibility. We have combined LED fluorescence microscopy with lysis of red blood cells (RBC) to improve the sensitivity and speed of detecting trypanosomes. In studies conducted at four centers in Uganda and the Democratic Republic of the Congo, parasitaemic blood was serially diluted and the RBCs lysed using commercial buffer. Samples were then concentrated by centrifugation, and different volumes of the sediment used to make thin and thick smears. Next, these were stained with acridine orange or Giemsa, and examined using an LED microscope under fluorescence or bright light, respectively. Detection of parasites was significantly improved by RBC lysis and concentration, regardless of the staining and microscopy method used. Further improvements were made when smears were prepared using larger volumes of sediment. The best results were obtained with thin smears prepared using 20 µl of sediment and stained with acridine orange. The time taken to see the first parasite was dramatically reduced when smears were examined by LED fluorescence microscopy, compared to bright light. LED fluorescence microscopy was found to be easier and requiring less visual effort than bright field microscopy. These studies demonstrate the potential for incremental improvement in detection of Trypanosoma brucei by combining LED fluorescence microscopy with RBC lysis and concentration. The lysis and concentration method may also be useful in sample preparation for other diagnostic tests for trypanosomiasis.