Health  

‘North, reservoir of malaria parasites in Nigeria’

Professor Wellington Oyibo is a Consultant Medical Parasitologist and Director, Research and Innovation Office, University of Lagos.


• Nigeria Has Highest Disease Burden In West Africa
• Malaria Testing By Medicine Retailers Will Promote Effective Management

Consultant medical parasitologist, and Director, Research and Innovation Office, University of Lagos, Professor Wellington Aghoghovwia Oyibo, spoke to PAUL ADUNWOKE on malaria burden, prevalent species and treatment regimen in the country.

How has the country fared with malaria, and how has government’s intervention in the last five years been?
Malaria still remains a disease of global concern, even as progress is being recorded. Current malaria estimates show that an estimated 212 million cases of malaria occurred globally in 2015, with 90 per cent of these cases occurring in Africa. In 2016, the World Health Organisation (WHO) estimated that mortality due to malaria during this period was 429, 000 deaths, with 303, 000 deaths recorded in children less than five years. Ninety-two per cent of deaths recorded were in Africa, while plasmodium falciparum was the plasmodium species responsible for 99 per cent of global deaths, according to WHO.

Nigeria and the Democratic Republic of Congo still remain countries with the highest burden of malaria in Africa, according to the 2016 WHO report, while in the West African region, Nigeria has the highest malaria burden.

In Nigeria, malaria is a disease of public health concern. It is worthy to note that the epidemiology of malaria is changing with reduction in malaria prevalence. National prevalence of malaria in 2015 was 27 per cent. The National Malaria Elimination Programme (NMEP) 2016 saw a reduction from the 2010 prevalence of 42 per cent malaria Near Point of Convergence (NPC).

The 2015 Nigeria Malaria Indicator Survey (NMIS) data showed that malaria prevalence among children of six to 59 months in the southern zone was less than 20 per cent, compared with the northern zone that was between 25 to 37 per cent. Malaria in the urban and rural areas followed already established patterns, with higher rates occurring in the rural areas. The effect of urbanisation and communicable diseases’ transmission remains an area to be carefully studied, though the drivers are pretty well known. The prevalence of malaria by microscopy in children of six to 59 months varied in the states, with the highest occurring in Kebbi 63.6 per cent, and Zamfara 62.6 per cent both in the North West; zero per cent in Lagos State. Imo State has 5.1 per cent in South East and Rivers State in South South.

Until 2010, when the National Malaria Indicator Survey was conducted, there was no national prevalence data, which made it difficult for progress in malaria control efforts to be tracked. I am happy to say that our platform in the College of Medicine, University of Lagos contributed to the determination of these national figures for malaria. We at the ANDI Centre are still providing technical support to the National Malaria Elimination Programme on malaria diagnosis, quality assurance and malaria diagnostic implementation because effective malaria case management is one of the strategies for controlling the disease, which requires early diagnosis and prompt treatment.

With the picture you have painted, what are the best preventive strategies for malaria?
Preventive strategies, such as integrated vector management; use of long-lasting insecticide treated nets (LLINs); indoor residual spray (IRS) and larval source management; chemoprevention among pregnant women, and seasonal malaria chemoprevention in children in the Sahel-Savanna region are currently being deployed. Let me also mention, with deep sense of humility, that it was a privilege to have contributed to the development of the diagnostic component of malaria case management thematic area of this plan. The NMSP was launched in 2014.

The data on the status of malaria in the country shows that we are in the control phase, given our slide positivity rate of 27 per cent despite the reduction in prevalence. We need to work hard at getting our prevalence down to attain the pre-elimination phase.

How lethal is malaria and what are the new species?
Malaria parasites, plasmodium species, are apicomplexan unicellular protozoan organisms that invade the red blood cells, following the bite of an infected female Anopheles mosquito. The new five human species that are currently recognised, include plasmodium falciparum, plasmodium ovale, plasmodium vivax, plasmodium malariae and plasmodium knowlesi.

Malaria, though preventable and curable, is a killer disease and knowledge of the attributes of the dreadful species, plasmodium falciparum is critical in dealing with malaria, either in our individual capacity, community, local government councils, state or as a country. This knowledge will also guide our attitude toward malaria, given the poor perception about it.

Plasmodium falciparum has very powerful capabilities of invading and establishing itself in the blood, while more than one parasite could enter the red blood cells and still keep the integrity of the blood, until the blood is destroyed. It has the ability to develop quickly after it leaves the liver, grow and multiplies and then re-invade newer red blood cells within a short time.

Indeed, it has the shortest pre-patent and clinical incubation period among the plasmodium species. It can multiply and produce new forms in very high numbers, compared to others and has the capacity of invading red blood cells of all ages. At a particular stage of growth, when they have multiplied up to about 16 parasites in one red blood cell, the late trophozoite stage, the parasite escapes or withdraws from the blood stream into other tissues, where they mature fully before releasing the 16 younger ones into the blood. The release of these into the blood triggers the response of the body with initial fevers and other uncomplicated symptoms.

Plasmodium falciparum can change its forms with or without drug pressure, which is why care must be taken to comply with ACT regimen and complete the doses, no matter how well you feel. The destruction of the parasitised blood also triggers the destruction of non-parasitised red blood cells and severe anaemia could occur in children with higher plasmodium falciparum densities, among others. When the parasites go out of the main circulation, they consume more glucose, which accounts for the weakness and prostration in patients. This sequestration could trigger hypoglyceamia, hypoglycaemic shock and eventual death. This explains why younger children are easily killed by plasmodium falciparum. At the initial stage of the disease, it takes a very short time before the onset of complications. This is a justification for early and prompt treatment with recommended medications.

It is still puzzling that the condition of a patient with minor malaria case could swiftly deteriorate and even result in death. Why so?
It is easy for patients without exposure or little exposure to previous malaria infection to have complications of severe malaria and death, if prompt care is not given. This is a threat to expatriates, when they work in malaria endemic countries and we saw more of this during the colonial period.

Currently, the insurance for expatriates in Nigeria is primed to cover for emergencies on cerebral malaria that includes package for emergency evacuation. We receive temporary immunity that is sustained with continuous bite of an infected female Anopheles mosquito. This is called premunition. However, this immunity will begin to wane, when infection is not frequent and we could become vulnerable to acute and severe malaria, when re-exposed to plasmodium infection. This condition is now currently being created due to behavioural modifications and unfortunately; we do not have what the expatriates have in terms of appropriate insurance cover.

Why is it mandatory to conduct medical test before malaria treatment is administered?
The current practice standard for effective malaria case management is mandatory parasite-based confirmation of all suspected cases of malaria, with malaria microscopy, or malaria rapid diagnostic tests (RDTs) before treatment with ACTs. This will confirm or rule out malaria so that the presenting condition of the patient is managed appropriately.

However, there are challenges in the implementation of this policy recommendation.The assumption that all fevers are malaria by healthcare providers and the public is a major challenge. This is really not true, going by evidence of changing epidemiology of malaria in the country and results of parasite-based confirmation of malaria in patients suspected to have malaria. The competency of microscopists to accurately detect malaria by microscopy is low in many facilities. This is worse in private health facilities, including private laboratories, due to poor diagnostic capacity. Low quality malaria diagnosis or the non-performance of a malaria test is a major contributor to the over diagnosis and over-treatment of malaria.

The consequence of malaria misdiagnosis or over-diagnosis and thus over-treatment is huge. A false positive test would lead to glossing over the actual cause of fever, and the concomitant delay in seeking attention for the presenting condition. This could be disastrous, if it is a life-threatening condition that is being erroneously treated as malaria.

The basis for the recommendation of mandatory testing of malaria was the need to introduce evidence-based practice subsequent upon the validation of rapid malaria diagnostic tests (RDTs) as an additional diagnostic tool to microscopy, which does not require electricity, highly trained personnel, and sophisticated laboratory or reagent.

However, the RDTs must be quality-assured by evaluating their performance with highly characterised standards. Unfortunately, the confidence of the healthcare provider on the clinical utility of the rapid malaria diagnostic tests is low and this has resulted in the continued practice of syndromic management of malaria in some settings.

How accessible to Nigerians are these malaria tests?
The need to urgently escalate access to malaria testing to the community, including the informal private sector through the Private Propriety Medicine Vendors (PPMVs), or medicine retailers, who attend to over 60 per cent of patients with fever, is critical in attaining the malaria case management target that has the objective of ensuring that malaria test is conducted for 80 to 100 per cent of patients suspected to have malaria by 2018 and 2020, in public and private health facilities, according to NMSP report of 2014. Democratising malaria diagnosis means availability and performance of a user-friendly malaria test made for the people, used by the people and useful to the people. Parasite confirmation is currently low and most medicine retailers do not conduct a test before selling ACTs. Malaria testing by the ubiquitous medicine retailers will promote effective malaria case management and also take testing closer to households.



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