From the Field: On the Frontlines of Malaria in Bagamoyo, Tanzania (Part I)
Lancet pricks the finger and blood streams out. A tiny glass pipette sucks a drop – 5 microliters to be exact. Blood is dropped in the sample well and two drops of solution in the buffer well. Now begins the twenty minute wait. This is the Malaria Rapid Diagnostic Test (mRDT). The lab technicians at Bagamoyo District Hospital do approximately 15-20 of these tests each day, all seven days a week. Not one day goes by without a positive malaria diagnosis, and sometimes, the number is as high as half a dozen. The Bagamoyo District Council estimates that 15,080 malaria cases were reported in 2016. Only upper respiratory and urinary tract infections outnumber malaria in outpatient departments. However, a month on the frontlines of malaria in Bagamoyo has revealed, beyond these numbers, the complexities that truly underlie this disease and pose a barrier in its eradication. It has exposed gaps in the healthcare system that have allowed the disease to flourish as well as the various solutions that promise to limit its spread.
It is important to acknowledge that great strides have already been made towards limiting the spread of malaria. Just in the Bagamoyo district, incidence rates for malaria in the worst-affected districts now hover under 10%. Just two decades ago, these rates were as high as 80%. However, as the WHO acknowledges, the number of malaria cases have historically been over-reported. Before the advent and widespread use of mRDT’s (with their instant and straightforward diagnosis of malaria), microscopy served as the gold standard for clinical diagnosis. However, due to a lack of equipment as well as skilled technicians to read microscopy slides, getting a definitive diagnosis for malaria was an immense challenge by itself, and still is in many places today. In practice, clinicians were forced to diagnose malaria on the basis of the general symptoms associated with the disease – fever, vomiting, chills, nausea, diarrhea, headache etc. This obviously resulted in the over-diagnosis of malaria, but more importantly, the over-prescription of malaria medication. This has rendered medications such as chloroquine ineffective in Bagamoyo (and Tanzania in general) because of drug resistance among local strains of the malaria parasite. Despite the recent improvements in diagnostics with the use of mRDT’s there are still many challenges that need to be addressed. For example, studies have claimed that mRDT’s often give false results due to limits in specificity and sensitivity and a comparative analysis still suggests that microscopy is the preferred method of diagnosis, despite being fairly unavailable.
When it comes to transmission, even though it is tempting to think of the Anopheles mosquito as the sole culprit for the spread of malaria, it is important to realize that this mosquito only acts as the shuttle for the parasite from one person to the next. Relying solely on the mosquito as a carrier (with a 2-3 week life cycle) is not particularly advantageous from the parasite’s perspective. Over a long period of time, these parasites (example, Plasmodium Vivax) have adapted forms (gametocytes) that allow them to stay dormant in humans for years while still being present in a form that can be easily transmitted from one person to the next with the help of the Anopheles mosquito. People living in endemic regions such as Bagamoyo are constantly exposed to local strains of the malaria parasite. This often results in increased immunity for people that have contracted and previously been treated for the disease. However, most existing drug regimens have proven ineffective in eliminating gametocytes. Primaquine is the only drug in use that if effective against gametocytes and its use is limited by safety concerns. In effect, children under the age of 5 are most vulnerable to malaria without this added buffer of immunity and simply trying to eliminate as many mosquitos as possible does not address the problem at its core.
Adding another dimension of complexity to this problem is the issue that due to lack of education as well as lack of access to affordable care, people in rural areas are more likely to misguidedly self-medicate the symptoms of malaria with antibiotics (often bought over-the-counter), or even wait until symptoms become unbearable. While treatment such as this might temporarily relieve symptoms, the outcomes for patients will undoubtedly be worse the longer their malaria is left untreated. Given all these challenges, it is not surprising that malaria eradication has become an immense challenge.