Outdoor Residual Insecticide Spraying (ODRS), a New Approach for the Control of the Exophilic Vectors of Human Visceral Leishmaniasis: Phlebotomus orientalis in East Africa

Visceral Leishmaniasis (VL) due to Leishmania donovani is a neglected protozoan parasitic disease in humans, which is usually fatal if untreated. Phlebotomus orientalis, the predominant VL vector in East Africa, is a highly exophilic/exophagic species that poses a major challenge to current Integrated Vector Management (IVM). Here we report results of pilot studies conducted in rural villages in Gedarif state, Sudan, to evaluate outdoor residual spraying of 20mg active ingredient (a.i.) /m² deltamethrin insecticide applied to the characteristic household compound boundary reed fence and to the outside of household buildings (Outdoor Residual Insecticide Spraying, ODRS), and as an alternative, spraying restricted to the boundary fence only (Restricted Outdoor Residual Insecticide Spraying, RODRS). Four to six clusters of 20 households were assigned to insecticide treatments or control in three experiments. Changes in sand fly numbers were monitored over 2,033 trap-nights over 43–76 days follow-up in four sentinel houses per cluster relative to unsprayed control clusters. Sand fly numbers were monitored by sticky traps placed on the ground on the inside (“outdoor”) and the outside (“peridomestic”) of the boundary fence, and by CDC light traps suspended outdoors in the household compound. The effects of ODRS on sand fly numbers inside sleeping huts were monitored by insecticide knockdown. After a single application, ODRS reduced P. orientalis abundance by 83%-99% in outdoor and peridomestic trap locations. ODRS also reduced numbers of P. orientalis found resting inside sleeping huts. RODRS reduced outdoor and peridomestic P. orientalis by 60%-88%. By direct comparison, RODRS was 58%-100% as effective as ODRS depending on the trapping method. These impacts were immediate on intervention and persisted during follow-up, representing a large fraction of the P. orientalis activity season. Relative costs of ODRS and RODRS delivery were $5.76 and $3.48 per household, respectively. The study demonstrates the feasibility and high entomological efficacy of ODRS and RODRS, and the expected low costs relative to current IVM practises. These methods represent novel sand fly vector control tools against predominantly exophilic/exophagic sand fly vectors, aimed to lower VL burdens in Sudan, with potential application in other endemic regions in East Africa.

Phlebotomus orientalis is the predominant vector of visceral leishmaniasis (VL, kala azar) in Sudan and other countries of East Africa, where the disease causes high morbidity and mortality. This sylvatic sand fly species is abundant in wild habitats characterized by presence of black cotton soil and vegetation dominated by Balanites aegyptiaca and/or Acacia seyal trees. In villages, the vector bites people in the household yard and in nearby peri-domestic locations, exhibiting limited indoor resting behaviour. The marked exophagic and exophilic behaviours of P. orientalis represent a profound challenge for VL control by excluding indoor residual spraying of insecticides (IRS) and compromising the efficacy of insecticide-impregnated bednets (ITNs). In this study, we evaluated the entomological efficacy of residual pyrethroid applied outdoors to household boundary fences and the exterior walls of household huts (outdoor residual insecticide spraying, ODRS), to reduce the abundance of P. orientalis inside and outside houses. We also evaluated the entomological impact of a restricted outdoor residual insecticide spraying (RODRS), whereby insecticide was applied only to the boundary fence. The study was carried out in June 2016-June 2017 in Jebel-Algana and Umsalala villages, Gedarif state, eastern Sudan, which are highly endemic for VL. The results showed that a single ODRS application of 20mg a.i. /m² 2.8% deltamethrin provided average reductions of 83%-99% in outdoor and peridomestic P. orientalis sand fly numbers relative to unsprayed control clusters. RODRS reduced outdoor and peridomestic P. orientalis by 60%-88%. The average cost of ODRS and RODRS per household were $5.76 and $3.48, respectively. The costs of these community-based control measures were substantially lower than the costs of LLINs, which is the only evidence-based tool used to protect against VL in the area. Future studies should evaluate the impact of ODRS/RODRS transmission of VL incidence in endemic villages and in seasonal agricultural farms.

Clinical features and treatment outcomes of visceral leishmaniasis patients admitted to three centers in Oromia, Ethiopia

INTRODUCTION

In three health care facilities in the Oromia region, the aim of this study is to report on 1) the number of VL cases registered over time (2013-2018) and 2) the clinical profile, type of treatment used and response to treatment.

METHODOLOGY

A retrospective cohort study was conducted among all VL cases admitted with a diagnosis of VL.

RESULTS

A total of 434 VL cases were registered at the three health facilities, but patient files were available for only 188. Most (51.6%) were children and only three presented with VL relapse. 78 (41.5%) of the 188 patients presented within one month of symptom onset. Concurrent severe acute malnutrition (27.1%), tuberculosis (6.4%) and malaria (6.4%) were common. There were only two cases with HIV coinfection. Fourty-three percent were treated with antimonials, 34% with antimonials combined with paromomycin and 23% with AmBisome. Amongst the 188 patients with patient files there were no deaths and one treatment failure. Six months outcome data were however missing for all. Aggregated data from the 434 VL cases reported three deaths, two treatment failures and one relapse.

CONCLUSIONS

Children were most commonly affected, suggesting long-term endemicity. While short-term outcomes are encouraging, long-term follow-up data are required.

Impact of Education on Knowledge and Practice of Kala Azar Preventive Measures among Seasonal and Migrant Agricultural Workers in Northwest Ethiopia

Kala azar occurs among seasonal and migrant agricultural workers in northwest Ethiopia and accounts for almost 60% of the disease burden in the country. We conducted a quantitative study on the level of knowledge and practice of this vulnerable group in relation to kala azar transmission and acceptability of its vector control tools. A total of 403 workers were randomly selected from eight farms using a purposive sampling technique. Knowledge and practice scores were calculated based on 12 and 9 core questions, respectively. Binary logistic regression was used to identify factors associated with knowledge and practice. A large gap in knowledge of the disease and the vector was evident with 61.8%, 24.6%, and 13.6% of the workers having poor, moderate, and good levels of knowledge scores, respectively. Similarly, 95% of the seasonal workers reported poor level of use of protective measures against the bite of the sand fly vector. Good level of knowledge about kala azar and its sand fly vector was statistically associated with formal education (adjusted odds ratio [AOR] = 2.11; 95% CI = 1.17, 3.80; P < 0.05) and previous exposure to health education (AOR = 4.72; 95% CI = 1.99, 11.16; P < 0.001). Despite poor current knowledge and practice, a large proportion of the study participants showed interest in using vector control tools if made available, with 78% of the seasonal and migrant workers expressing some willingness to pay for different measures that can protect against sand fly bites. Therefore, we strongly recommend that comprehensive health education and vector control programs should be provided to these workers.

Epidemiological and molecular investigation of resurgent cutaneous leishmaniasis in Sudan

OBJECTIVES

Local health personnel have drawn attention to an apparent increase in incidence and severity of cutaneous leishmaniasis (CL) in Sudan. The objective of this study was to investigate CL burden and surveillance.

METHODS

Surveillance data were compiled from the KalaCORE programme, Leishmania coordinators in Northern Kordofan and Southern Darfur, and Khartoum Dermatology Hospital. CL lesions were sampled from 14 suspected cases from Northern Kordofan and the Hospital for Tropical Diseases in Omdurman. PCR-restriction fragment length polymorphism analysis and multilocus sequencing were used to characterize the disease agent.

RESULTS

All sites reported substantial increases from 2014 to 2016/7, far exceeding World Health Organization case reports for 2014, consistent with a widespread outbreak. Single seasonal peak incidence was observed, except for two peaks in Southern Darfur. In Northern Kordofan, the odds ratio for CL in the 35-44 years age group was 2.6 times higher than in the >45 years age group (p<0.0001); in Southern Darfur, the OR was 2.38 greater in males than females (p<0.0001). Lesions included severe presentations, despite chemotherapy. Leishmania major was identified as the agent.

CONCLUSIONS

Active surveillance is required to understand the extent of CL in Sudan, as well as training to standardize surveillance, diagnosis, reporting, and quality control. Point-of-care rapid diagnosis would be valuable. Genotyping and phenotyping are required to monitor the emergence of pathogenic strains, drug resistance, outbreaks, and changes in severity.