Effective sandlfy-control methods could reduce Kala-azar burden

A new multi-country study including icddr,b finds insecticide-infused durable wall lining (DWL) the most effective method to control breeding of sand flies that spread kala-azar, also known as visceral leishmaniasis (VL).

(left) A DWL is being installed. (right) DWL after installation. Photo: Dinesh Mondal / icddr,b

The wall linings are thin polyethylene material coated with insecticide that obstruct sand flies from hatching eggs on the walls. Controlling the breeding will help reduce kala-azar, which is spread when sand flies infected with the Leishmania parasite bite humans – resulting in fever, weight loss, swelling of the spleen and liver and serious anaemia which, if left untreated, can claim lives.

“Prevention is indeed better than cure. This new study has helped determine the most effective management of controlling the sandflies - the ‘vectors’ that spread the disease,” says Dr Dinesh Mondal, a senior scientist at icddr,b and principal investigator of the study published in PLOS NTDs.

Kala-azar victimises the poor, mostly in rural Bangladesh, India, Nepal and East Africa, while the first three countries reportedly contribute up to 60% of the worldwide VL burden, estimated at 200,000 - 400,000 cases every year.

With the introduction of a kala-azar elimination programme in 2005, its burden has been reduced significantly in the Indian subcontinent. The programme recommends sand fly reduction through integrated vector control management, which optimally requires more than one vector control method.

The study has also found insecticide infused bed-nets – canopies made with thin nets over the beds to prevent mosquitos and sand flies -  as the second most effective method. “The study recommends these two methods for the VL elimination programme in the Indian subcontinent,” adds Dr Mondal.

Sand flies. Photo: LTC. Russ Coleman / AFPMB. CC BY-NC-ND 2.0

Recent reports say that the parasite has been around for 65 million years and still causes an estimated 20,000 deaths every year worldwide. In Bangladesh, the Government has successfully reduced the burden of disease over the years by combined active case searches (identifying infected individuals in the community), treatment and vector control strategies.

“The quest for devising cost-effective solutions to kala-azar detection also remains important,” says Dr Mondal.

 

Frugal solutions to detect kala-azar infections

Recent icddr,b research has shown that kala-azar detection methods work as well on urine samples as on blood samples, suggesting they could be used as non-invasive diagnostic tests for Leishmania infection.

A new study, published in the Parasites and Vectors journal, evaluated a number of recently developed laboratory assays that detect the presence of Leishmania-specific antibodies. To date, these assays have generally been used on blood samples, but as these antibodies are excreted in urine, it may also be possible to identify Leishmania infections by testing urine samples, which are more convenient and safer to collect.

icddr,b researchers examining the test kit with urine samples. Photo: Rabiul Hasan / icddr,b

“One of the assays has shown 98.9% sensitivity and optimum specificity in detection of antibodies against Leishmania,” says Mr Prakash Ghosh, lead researcher of the study.

“The accuracy rate reflects the idea that a test kit using urine samples in combination with that assay could be a cost-effective alternative for detecting VL infection,” he adds.

Dr Mondal, who is a senior author of the study, commenting on the finding says, “An accurate, cost-effective and less-complicated method for detecting VL would be ideal for a low-resource setting like Bangladesh. If proven effective in a phase III clinical trial, this method could be a promising solution for mass screening as it might only cost US$2-3 to evaluate each sample.”

An earlier icddr,b study led by Dr Mondal has shown a solar-powered mobile suitcase laboratory to detect VL to be as accurate as laboratory tests.

MN