A first case report of Plasmodium knowlesi infection in Saraburi Hospital and pitfall of malaria diagnosis by microscopic technique

Abstract

Malaria is caused by Plasmodium infection. All species can be transmitted from human to human but Plasmodium knowlesi is a zoonosis. The differentiate diagnosis of P. knowlesi via a microscopic technique is difficult and requires high experience. Because the characteristics of early trophozoite of P. knowlesi are similar to P. falciparum, while growing trophozoite are similar to P. malariae. Therefore, the classification of this species is high rate of misidentification. According to WHO recommendations, P. knowlesi may be confirmed with molecular technique. In 2019, a 23-year-old male patient admitted at Saraburi Hospital with high fever, chills and shaking in the evening period for 6 days. Thin blood smear was positive 0.2% of parasitemia with ring form and growing trophozoite suggestive non-P. falciparum malaria infection (P. vivax). Surprisingly, The PCR was demonstrated positive with P. knowlesi infection. However, microscopic examination of differentiating P. knowlesi has limitations and may be considered molecular technique support in complicated cases with low parasitemia, unclassified morphologic appearance and non-endemic area.