Plasmodium vivax malaria is endemic and often neglected protozoal infection that is distinguished by a delayed clinical presentation and a milder clinical course in the initial stages of the disease. Fever, chills, hepatosplenomegaly and anemia are most important symptoms. The diagnosis can be made through several tests, but a thorough clinical assessment is vital for raising suspicion toward malaria as the underlying cause.
Plasmodium vivax malaria, one of the types of this protozoal disease, is considered to be a global health problem, as it causes up to 390 million clinically apparent infections every year on several continents . P. vivax, transferred by the Anopheles family of mosquitoes to the human host, primarily causes infection in South East Asia and the Central/South America, whereas only a few African countries (Madagascar, Sudan) are the site of P. vivax malaria infection   . The pathogenesis of malaria lies in the ability of the protozoa to cause red blood cell (RBC) destruction and a severe inflammatory reaction. Similarly to other types of malaria, the clinical presentation is comprised of chills, myalgia, and high fever, but the 48 hour-cyclic appearance (tertian fever) is a highly specific finding for P. vivax and P. ovale . Additional findings include malaise, abdominal pain, gastrointestinal irritation (nausea, vomiting, diarrhea), jaundice, hepatosplenomegaly, anemia, and a cough    Although P. vivax was until recently interpreted as a milder form of malaria, studies have confirmed the increasing presence of prostration, respiratory insufficiency, persistent vomiting and hyperpyrexia in patients suffering from this type of malaria . The incubation period may be quite long, as certain forms of P. vivax inhabit the human liver and remain dormant for a significant period of time (week, months or even years might pass before the onset of symptoms or relapse) . The relapsing and remitting course of the disease, as well as its challenging therapy (but also a delayed diagnosis), are major issues when treating these patients, and requires a comprehensive approach.
The diagnosis of P. vivax malaria must be made early on, as 10-20% of patients are estimated to suffer from a severe form of illness, for whom mortality rates range between 5-15% . The ability of the physician to recognize signs and symptoms of malaria is vital. Patients should be asked about recent travel (possibly to endemic areas) and whether the symptoms appear in a specific fashion (tertian fever). After a detailed physical examination, which may detect hepatosplenomegaly and jaundice, laboratory studies are the next step. A complete blood count (CBC) will virtually always reveal anemia, and thrombocytopenia up to a certain extent  , while a complete biochemical workup is recommended. To confirm the diagnosis of malaria and determine the specific subtype, several tests have been described in the literature, such as peripheral blood smear examination, microscopy, rapid diagnostic testing and polymerase chain reaction (PCR)  . Although microscopic techniques and blood smear examinations lack sensitivity, they are a superior method for the detection of Plasmodium species, but these sophisticated tests are rarely available in areas affected by malaria . Thus, rapid diagnostic tests (RDTs), which are able to detect malarial antigen in blood and cost less are easily performed in this setting .