Devon Harvey
Article Summary
In July of 1977 a detection survey was conducted for malaria infection in two villages of the
Khanmouane Province, Lao People’s Democratic Republic. Malaria infection was detected by
microscopy and Polymerase Chain Reaction assay (PCR assay). Earlier studies had been done in
1995 and 1996 but microscopy was the only detection method; PCR assay makes clearer the
results due to the accuracy of the method. Both methods will be used to detect the infection and
then compared results to see the difference. The villages were Phavang and Sisomsouen and the
estimated population was 230 for Phavang and 430 for Sisomsouen but only 143 and 193 people
were tested. The results will help get more accurate data and therefore have a more accurate
estimate of the number of those infected by the disease.
Malaria is caused by a single-celled parasite from the genus Plasmodium. Generally,
malaria is contracted from mosquitos but can also be contracted from contaminated blood. The
infected red blood cells begin to burst causing chills, fever, and sweating. These symptoms happen
in paroxysms or recurring attacks. During the chills phase, it is common to see headaches, fatigue,
muscular pains, nausea, and diarrhea. By the end of the attack the person will begin to feel tired
and weak and will most likely fall asleep. The latest survey before this one indicated that 2.2-7.6%
of the population was infected. The PCR assay method has shown to provide more accurate data
and will help to get a more accurate count of infected people.
In the previous surveys where blood smear examination was the only method used to
detect infection, many times the infection was not recognized. Thick and thin blood smears stained
with Giemsa were analyzed. The blood was retrieved by a single finger prick. Any think smears
that had no parasite detected after 100 oil immersions fields was considered negative. Blood
parasitemia was calculated on the basis of positive smears collected in Phavang; it was based on the
number of parasites per µL of blood in a thick smear assuming a leukocyte count of 8,000/ µL. It is
Devon Harvey
difficult to detect parasites in subclinical infections under microscopic examination therefore
leading to an underestimate of the value. For the PCR method, approximately 100 µL of blood was
collected and then sent to the lab. During PCR, reverse primers that are complementary to the
four human malaria parasites were added. With each of the samples, a negative control was also
run. Ten µL of the PCR product was then electrophoresed on a 2% agarose gel. When the gel was
looked at under UV light, positive signals could be observed at 110 base pairs.
From the village of Phavang, there were a total of 143 people tested for malaria infection.
Using microscopic examination of blood smears, 46 or 34.3% of the people’s results returned
positive for a malaria parasite. Using PCR assay, 87 or 60.8% of people tested positive. In
Sisomsouen village there was a total of 193 people tested. Microscopic examination showed that 9
or 4.7% of people were infected. PCR assay showed that 30 or 15.5% of people had contracted
malaria. In the village of Phavang there was a difference of approximately 30% between the
detection of malaria using microscopic examination and PCR assay in individuals between the ages
of 41 and 50. In the village of Sisoumsouen, for people between the ages of 31 and 40 there was
20% of them that tested positive using PCR assay and 0% using microscopy. These results clearly
show the differences between the accuracy of the methods.
Clearly, using PCR assay is much more effective and accurate. The results from this
experiment will greatly influence future experiments of a similar nature and increase the accuracy
of such experiments. The results indicate that there is a high number of the population that is
infected and is a serious problem. The country already has started anti-malaria activities including
DDT residual spraying, improvement of diagnostic facilities, and better treatment of malaria cases.
These should all help combat the spread and transmission of this disease. The overall success of
this survey was high. The results showed data that corresponded directly to what the study was
trying to analyze. More studies similar to this will be occurring in the future.