This first case of P ovale
infection in Bangladesh was detected at a relatively well-equipped research facility in the rural southeast of the country demonstrating some common pitfalls associated with the diagnosis of febrile illnesses and malaria in the tropics. Despite the fact that physicians, microscopists and laboratory technicians at this facility are highly trained, diseases that have never previously been reported from a region are typically excluded from the spectrum of possible differential diagnoses. In this case, reasons for not including P ovale
malaria as a primary diagnosis are threefold. (1) P ovale
malaria had never previously been reported from this highly malaria-endemic region of Bangladesh. (2) The limited laboratory resources available at field level make a distinction of malaria parasites difficult. This particularly applies to the rare species, such as P ovale
and Plasmodium knowlesi
(which so far has also not been reported from Bangladesh).4
(3) RDTs commonly used in malaria-endemic countries of Asia are either limited to diagnosing falciparum and vivax malaria or (in case of RDTs using pan-malaria antigens for diagnosis) are not sensitive and specific enough for the detection of non-falciparum infections.5
Despite the fact that RDTs are convenient, fast, relatively inexpensive and easy to perform, the UK malaria treatment guidelines recommend the use of RDTs only in addition to, but not as a replacement for, microscopy, and all patients with suspected malaria to have blood films prepared and examined.5
Typically RDTs today achieve a sensitivity of over 95% for falciparum malaria. Unfortunately, this statement does not necessarily apply to non-falciparum malaria. The sensitivity of malaria RDTs tends to drastically decline with decreasing numbers of parasites and as non-falciparum infections inherently present with lower parasitaemia, RDTs alone are not a good option for diagnosing malaria.6
Particularly in resource-limited healthcare systems, as typically encountered in malaria-endemic countries, adequate diagnosis can be a major challenge. Without the necessary logistics, presumptive diagnosis remains the most common means of malaria diagnosis typically resulting in massive overdiagnosis of malaria in febrile patients.7
However, this case also demonstrates that under certain circumstances even highly trained research microscopists can fail.
- This case report indicates a wider geographic distribution of P ovale than previously suspected.
- P ovale malaria should therefore always be considered a potential differential diagnosis in travellers and migrants returning from Bangladesh, possibly up to years after their return.