Abstract
Cerebral malaria (CM) is a diffuse encephalopathy associated with coma and seizures commonly caused by Plasmodium falciparum (P. falciparum) in children with severe malaria. We present a case of a 19-year-old man with CM due to Plasmodium vivax (P. vivax) infection. Cerebrospinal fluid (CSF) was negative for Japanese B encephalitis, enterovirus, herpes simplex 1 and 2, varicella and mumps viruses as determined by real-time polymerase chain reaction (PCR). P. falciparum and P. vivax species were analysed by microscopy, immunochromatography and PCR assays and confirmed mono-infection of P. vivax in the patient’s blood, and P. falciparum infection was established to be negative. The patient was discharged after intensive supportive care and antimalarial treatment (intravenous artesunate and oral doxycycline). We conclude that P. vivax infection is associated with CM, a life-threatening complication rarely seen in coastal districts of Karnataka. In endemic areas, the possibility of CM should be considered even with P. vivax infection.
Introduction
The severity of malaria is generally considered to be greater in infections caused by Plasmodium falciparum (P. falciparum) than in those caused by Plasmodium vivax (P. vivax). Complications such as renal failure, severe anaemia, acute respiratory distress syndrome, shock, hypoglycaemia and central nervous system damage are common with P. falciparum malaria. Malaria due to P. falciparum is accountable for about 90% of the deaths and complications worldwide. Complications are rare during the course of P. vivax infection.1,2 Cerebral malaria (CM) is a diffuse encephalopathy usually seen with P. falciparum infection. There are reports of complications caused by P. vivax infection,3,4 but minimal data are available from coastal districts of Karnataka state in India with mono-infection of P. vivax confirmed by sensitive polymerase chain reaction (PCR)-based assays. 5 This gives us a great opportunity to document such unusual cases. Few retrospective studies from coastal districts of Karnataka have presented an association of P. vivax infection with several complications.6–8 Typically, the manifestation of such complications with P. vivax infection is attributed to mixed infection by both P. falciparum and P. vivax parasites, with P. falciparum being unidentified. 9 However, these studies are completely based on hospital data and do not include molecular tests for Plasmodium species identification. We present a case of CM with mono-infection of P. vivax confirmed by PCR assays. Studies using molecular methods are more reliable than retrospective studies. 10
Ethical statement
Written prior informed consent was obtained from the patient. The Institutional Ethics Committee of Manipal University, Manipal, India, approved the study.
Case history
A 19-year-old man with no known medical illnesses was diagnosed with P. vivax malaria in a primary care hospital based on the history of high fever with chills, headache, vomiting of 2 days’ duration and a positive blood smear. He was started on treatment with oral chloroquine. He had not received any antimalarial medications before this. He had mild thrombocytopenia (platelet count 110 × 103/mm3), normal creatinine and electrolytes, and mildly elevated bilirubin (total bilirubin 1.3 mg/dL, conjugated bilirubin 0.7 mg/dL) in the initial tests. Serological tests for dengue (NS1 antigen and IgM antibodies) were negative. About 6 h after the first dose of chloroquine, he developed an episode of generalised tonic-clonic seizures (GTCS) in the hospital with up-rolling of eyes and frothing that lasted for about 5–6 min, followed by post-ictal confusion that lasted for more than 1 h. Glasgow coma scale (GCS) details for this period were not available. He was then referred to our hospital for further management.
On examination at our hospital, he was conscious and oriented, afebrile (temperature 36.9℃) and had normal vital parameters (pulse, 80 bpm; blood pressure, 124/80 mmHg; 18 breaths/min; and oxygen saturation, 98%). Neurological system examination was also essentially normal with bilateral equally reactive pupils, normal optic fundi, flexor plantar response and no signs of meningeal irritation. Blood smear with a quantitative buffy coat (QBC) preparation was reported as positive for P. vivax. Considering severe P. vivax malaria, he was initiated on intravenous artesunate and oral doxycycline along with supportive therapy. His repeat blood counts were normal except mild thrombocytopenia (haemoglobin, 14.0 g/dL; total WBC count, 8.2 × 103/mm3 with normal differential counts; platelets, 101 × 103/mm3), normal blood glucose (138 mg/dL), normal renal functions with mild hypokalaemia (blood urea, 11 mg/dL; serum creatinine, 1.0 mg/dL; serum sodium, 136 mEq/L; serum potassium, 3.0 mEq/L; and serum calcium, 9.0 mg/dL), mild elevation of liver transaminases (asparate aminotransferase, 95 u/L; alanine aminotransferase, 65 u/L). His arterial blood gases were normal too (pH, 7.36; pCO2, 33 mmHg; pO2, 158 mmHg; and HCO3, 22 mmol/L).
He remained stable throughout that night, but developed another episode of GTCS lasting for about 3 min in the ICU, that was managed with intravenous lorazepam. He had a brief duration of unresponsiveness lasting for about 30 min with GCS of 11 (E3 V4 M4). He was also initiated on intravenous levetiracetam to prevent further seizures and investigated further. He did not have any history of similar seizure episodes in the past. Repeat QBC was also positive for only P. vivax, and P. falciparum was specifically reported as negative. The blood sample was also diagnosed by PCR to confirm the presence of Plasmodium species. Two sets of primer pairs were used to detect malaria parasites – primer pairs for PfCRT and PvLDH genes specific for P. falciparum and P. vivax, respectively,
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and this demonstrated positive result for P. vivax infection and negative for P. falciparum (Figure 1). A number of tests were performed to rule out the presence of any other co-infection and complications as listed in Table 1. The patient was HIV negative. Contrast-enhanced computed tomography (CT) scan of the brain was normal. A lumbar puncture was performed to look for evidence of encephalomeningitis. Opening pressure was normal and cerebrospinal fluid (CSF) was clear. CSF had no cells and biochemical tests were normal (protein, 33 mg/dL; glucose, 82 mg/dL; and adenosine deaminase, 4 u/L). Subsequently CSF was reported as sterile on culture and negative for Japanese B encephalitis, enterovirus, herpes simplex 1 and 2, varicella and mumps viruses by real-time PCR. Magnetic resonance imaging (MRI) of the brain was also normal. Electroencephalogram (EEG) was performed 2 days after the episode and found to be normal. He remained stable throughout the stay and did not have any further episodes of seizure. All abnormal reports improved gradually and returned to normal at discharge 6 days later. QBC smear after treatment was negative for malarial parasites. He was diagnosed as having CM presenting with seizures, due to P. vivax malaria. He came for follow-up about 2 weeks later. Levetiracetam was tapered and stopped over the next 2 weeks. He remained asymptomatic when reviewed last after about 6 months of the episode.
(a, b) PCR amplification product of 182 bp and 145 bp by using PvLDH specific for P. vivax (forward 5′-AAGAACCTGGGGGACGTAGT-3′ and reverse 5′-TCTCGGTTCCATTCCTTGTC-3′) and PfCRT specific for P. falciparum (forward 5′-TGTGCTCATGTGTTTAAACTT-3′ and reverse 5′-CAAAACTATAGTTACCAATTTTG-3′) primers pairs, respectively. Lane 1 in (a, b) represents 100 bp DNA marker. In (a), lanes 2, 3 and 4 are negative PCR control, test sample and P. vivax positive PCR control, respectively. In (b), lanes 2, 3 and 4 are negative PCR control, test sample and P. falciparum positive PCR control, respectively. Table showing tests performed on the subject to exclude other causes.
Discussion
Cerebral malaria is commonly seen with severe P. falciparum infection. Classically, demonstration of CM with P. vivax is attributed to mixed infection by both P. falciparum and P. vivax parasites. Studies have shown cytoadherence of P. vivax to erythrocytes, causing rosetting in vitro. Other studies have shown adherence of P. vivax to endothelium and to chondroitin sulphate A,12,13 although the intensities of adhesion by P. vivax in these circumstances are less than those of P. falciparum. However, these observations suggest the possibility that cerebral microvascular sequestration may cause P. vivax-associated CM. Hence, it is very important to document such unique cases after confirming mono-infection of P. vivax with reliable assays like PCR. It is impossible completely to preclude the possibility of P. falciparum by conventional methods, which may perhaps explain, in various cases, use of anti-malarial therapy against both P. falciparum and P. vivax infection. 14 It has been shown that chances of identifying mixed infection by PCR assays are 15 times higher than with conventional assays. 10 Here, we present a case of CM caused by mono-infection of P. vivax detected by PCR analysis in an adult man. To the best of our knowledge, most such cases are seen in children. 13
Our patient developed two episodes of GTCS in the hospital with up-rolling of eyes and frothing that lasted for few minutes followed by confusion that lasted for more than 1 h after the first seizure. Various definitions of CM exist. The World Health Organization (WHO) clinical definition of CM includes the following: a Blantyre coma score of <2 (or GCS ≤ 11); P. falciparum parasitaemia by blood film; and no other evident cause of coma (e.g. meningitis, post-ictal state, hypoglycaemia). 15 However, the most recent WHO publication in 2014 defines CM as: definite evidence of malaria infection; asexual forms of P. falciparum in the blood film; and a GCS of less than 11 for at least 1 h. 16 Seizures per se are not a criterion for diagnosis of CM, but for severe malaria. However, as our patient had the first seizure before being referred to our hospital and had prolonged unresponsiveness lasting for more than 1 h, we considered the diagnosis of CM without a definite GCS value. It is to be also noted that a definite diagnosis of CM requires postmortem examination of the brain either by autopsy or supra-orbital sampling, which were not possible in our case. More importantly, we have excluded all other locally prevalent causes for this neurological complication. However, there are also other definitions of CM where the duration of unarousable coma is recommended as 30 min after a generalised convulsion. 17
Unrecognised CM in P. vivax infection may lead to increased mortality in P. vivax malaria. It is important to be aware of significant complications in P. vivax, that are generally considered to be seen only with P. falciparum, so that clinical effort may also be directed to avoid and detect such complications. Mortality due to P. vivax infection can jeopardise the efforts of the Asia Pacific Malaria Elimination Network, to eliminate and control P. vivax infection in the Asia Pacific regions. Accurate diagnosis of malaria parasites via molecular methods can have a big impact on public health policies.
Footnotes
Acknowledgments
The authors wish to thank Dr Arunkumar G of Manipal Centre for Virus Research, Manipal University, India where CSF was tested for viruses.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.