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MALARIA: Resistance threatens success of mosquito nets in Nigeria

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By Chioma Obinna

Amaka Odiogo just recuperated from malaria three weeks ago.  She was never expecting another bout anytime soon.  But she was wrong!  Barely one month on, there she was, shivering and running high temperature. A laboratory test run on her revealed another bout of malaria.

It was clear Amaka was not happy even after she slept in a Long Lasting Insecticidal Treated Net (LLIN), her family benefitted from the over three million nets distributed in Imo State in 2017.

MALARIA PREVENTION Pregnant woman sleeping under Long Lasting Insecticide Treated net

Amaka lives in one of the remote communities in Ngor Okpala Local Government Area of Imo State. Interactions with residents of the community and environs revealed that they groan everyday for lack of good roads and electricity, which also contributed to the lack of access to good healthcare.

Sadly, the harsh economic situation in the country has not made their situation any better as majority of the residents are poor rural farmers shuttling between their homes and farms.

Findings by The Vanguard reveals that due to lack of awareness and regular electricity supply, community members are forced to stay late outside, taking fresh air, while some cannot afford to sleep under the nets due to hot weather condition in the rooms, occasioned by poor electricity supply.

Amaka explained that although government has distributed the nets to most families in the community, there has not been any education on the proper use of the nets.  “Many of us are using it today as a fence for our plants.  Some of us use it for other things.  And some have decided to abandon its usage entirely,” Amaka said.

Right in her compound, Vanguard spotted the net being used to cover cassava mash waiting to be fried into garri.

According to the World Health Organisation, WHO, universal access to and use of LLINs remain the goal for all people at risk of malaria, including Nigerians. LLINs are designed to maintain their effectiveness against mosquitoes that carry the malarial parasite and other diseases for at least three years if used properly.

A visit to Kosofe community in Lagos State, one of the waterlogged areas in the state, revealed that previously, at least two children died every month from malaria until the government distributed Insecticide-Treated Nets (ITNs) freely to the people

Mrs. Boade Sule, a mother who resides in the area, recalled the case of a 9-month old baby that developed high fever in the middle of the night but died few hours after she was taken to the hospital, where it was confirmed that she had malaria.

Mrs Boade is of the opinion that government should intensify public education and sustain the free distribution of the nets which has been a major concern of the people.

Statistics from the Nigeria Malaria Fact sheet states that malaria is endemic in Nigeria and mostly affects pregnant women and children.

The 2017 WHO World Malaria report also shows that Nigeria falls among the highest malaria burden countries, accounting for 27 per cent of global malaria cases. It also shows that malaria is a risk for 97 per cent of the country’s population and contributes to an estimated 11 per cent of maternal mortality.

The National Malaria Elimination Programme, NMEP, estimates that malaria costs the country’s economy about N132 billion annually.

However, indications have emerged that the mosquitoes are becoming resistant to current group of insecticides (pyrethroids) used in treating the nets, which have been described as the most effective and affordable protection against the debilitating disease.  Today, Nigerians who against all odds chose to sleep under the nets, are still at risk of malaria.

Studies conducted by the Nigerian Institute of Medical Research, NIMR, revealed that there is high level of resistant mosquitoes in several states in Nigeria.

Nigeria has over the years seen unprecedented progress in malaria in the areas of prevention and control. This has mainly been as a result of a significant scaling up of numerous interventions put in by government and stakeholders. However, these fragile gains are likely to be threatened by emerging resistance to insecticides among Anopheles mosquitoes and to anti-malarial medicines among Plasmodium parasites.

According to WHO, resistance is known to affect all major malaria vector species and all four recommended classes of insecticides. Since 2010, a total of 61 countries have reported resistance to at least one class of insecticide, with a 50 of those countries reporting resistance to two or more classes.

WHO defines resistance to insecticides as “an ability to tolerate doses of toxicants, which would prove lethal to the majority of individuals in a normal population of the same insect species.” Resistance arises from the selection of individuals able to survive and reproduce in an insecticide-treated environment or after being in contact with insecticides.

The Deputy Director, Research and Head, Malaria Research Group, NIMR, Dr. Sam Awolola who gave insight into the findings, confirmed resistant mosquitoes to the nets in over 20 states where the studies were conducted.

He traced the new trend of resistance to use of same reagents on agricultural products, stressing that, “basically, one of the major factors that contributed to insecticide resistance is the use of same reagents for agriculture globally. Most of the insecticides used in public health are also used in agriculture, which is a major source of resistance.”

Dr Awolola who is also the head of the Department of Public Health, NIMR with over 20 years post-doctoral research experience in Malaria Prevention and Control, however, confirmed that LLINs still remained number one prevention tool against malaria in Nigeria and has helped reduce the burden in the country significantly.

He said although there are other interventions that could be used like indoor residual spray; the nets are more affordable and easy to use.

Science behind the nets

He further explained that unlike in the past when nets were treated with insecticides routinely, insecticides have now been incorporated into the fibres of the nets right from the production phase, making it more effective than before.  The nets are no longer Insecticide-Treated Nets but Long Lasting Insecticidal Nets, which last for multiple years.

“Again, because the insecticide has been incorporated into the LLINs, it has three main functions: it creates a barrier between the people sleeping under the net and repels mosquitoes, and if the mosquitoes are stubborn, it kills the mosquitoes. An additional function with the new LLINs, which is now the fourth function is that when somebody sleeps under the net because it is in the room, it guards other people that are not sleeping under the net due to the insecticides’ ability to repel the mosquitoes.”

He, however, raised the alarm that Nigeria is facing high level of resistance following a study carried out by NIMR which showed that mosquitoes in 20 states of Nigeria have developed resistance to the current class of insecticides in the country.

”This is a major problem for us in the field because it is the only class of insecticides currently in the country, although researches are ongoing to get new active ingredients or a combination of nets.

Way out to fight resistance

Dr Awolola explained that science has been able to find a way with the development of new generation nets.  “The new generation nets are science-based insecticide net to kill the mosquitoes that have developed resistance. A new product called Piperonyl Butoxide, PBO, has been incorporated into the mosquito nets.

“With the addition of Piperonyl Butoxide, nets are now able to remove that resistance whilst also killing the mosquitoes”, he explained.

Professor Babatunde Salako, Director-General, NIMR, explains that resistance could occur not only when the chemicals are not of quality but when they are of quality as well.

The mosquitoes, he noted, have the ability to change their genetic makeup such that it will be able to resist. They all have some form of innate genetic ability to develop something the drug will not be able to identify.”

Prof.Salako posited that “From the report we have, resistance is almost in all the states of South-West and it is obvious that the use of the nets cannot be effective until the insecticides used for impregnation are changed to fight the resistant ones.

“Government should commission NIMR as a hub for vector surveillance and insecticide resistance mapping in Nigeria. Empower NIMR to explore the use of alternative mosquito control measures such as the “Sterile Insect Techniques” and “Genetic Modified Mosquito” for malaria control in Nigeria,’’

Although, the greatest intervention in history against malaria had remained the LLINs, which have dramatically reduced malaria globally and particularly, in Africa. Since its introduction, the gains against malaria are being threatened as a result of the fact that mosquitoes are now resistant to the group of chemicals used currently in Nigeria.

Mechanisms that decrease the insecticide toxicity can only rely on modifications in one or several genes of the mosquito, and, as a result, resistance is a heritable trait. In the presence of insecticides, the frequency of alleles responsible for insecticide resistance increases in the population because they confer a strong advantage.

Unfortunately, resistance against this insecticide family is widespread and may jeopardise the success of malaria control.

Unchecked, insecticide resistance could lead to a substantial increase in malaria incidence and mortality. The global malaria community and for that matter, Nigeria, needs to take urgent action to prevent an increase in insecticide resistance, and to maintain the effectiveness of existing vector-control interventions.

Health experts believe that finding alternative with the recently introduced nets that contain permethrin and PBO that remove the resistance will boost the effectiveness of the nets in the fight against malaria.

This story is supported by Africa Science Desk.

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