Parmendra Sirohi

Thrombocytopenia in Plasmodium falciparum, Plasmodium vivax and mixed infection malaria: A study from Bikaner (Northwestern India)

The occurrence, relation and magnitude of thrombocytopenia in different species of malaria are not clearly defined. This study included 1,064 patients admitted with malaria to study thrombocytopenia (platelet count <150,000 /cumm) in Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) mono infection and mixed infection (Pf + Pv). The species diagnosis was done by peripheral blood film (PBF) and rapid diagnostic test (RDT). Validation by polymerase chain reaction (PCR) was done only in patients with severe thrombocytopenia (platelet count <20,000 /cumm). The breakup of patients was 525 (49.34%) Pf, 460 (43.23%) Pv and 79 (7.42%) mixed malaria (Pf + Pv). Thrombocytopenia was observed in 24.6% (262/1064) patients. The risk was greatest in the mixed infections in comparison to monoinfection individually (43.04% [34/79]; mixed vs Pv monoinfection: Odds Ratio [OR] = 1.675 [95% Confidence Interval (CI) 1.029–2.726], p < 0.0366; mixed vs Pf monoinfection: OR=3.911 [95% CI 2.367–6.463], p < 0.0001). Pv monoinfection (31.09% [143/460]) had greater risk compared to Pf monoinfection (16.19% [85/525]; OR = 2.335 [95% CI 1.722–3.167], p < 0.0001). The occurrence of severe thrombocytopenia was also higher in Pv monoinfection (18.18% [26/143]) in comparison to either Pf monoinfection (10.59% [9/85], OR = 1.877 (95% CI 0.834–4.223)) or mixed infection (11.76% [4/34]; OR = 1.667 (95% CI 0.540–5.142) but this association was statistically not significant. Six patients (3 Pv, 2 Pf and 1 mixed) developed severe epistaxis requiring platelet transfusion. There was no relation between parasite density and platelet count as many patients with severe thrombocytopenia had parasite density similar to patients without thrombocytopenia. We found that the association of thrombocytopenia was statistically more significant with P. vivax monoinfection as compared to P. falciparum.

An unexpected cause of fever and seizures

In June, 2007, a 27-year-old man was brought to our emergency department by ambulance, having regained consciousness after a generalised tonic-clonic seizure. He had been having fever, chills, and rigors, on alternate days, for the previous 8 days. He had no past history of convulsions, head injury, febrile convulsions during infancy, birth trauma, meningitis, encephalitis, or psychiatric illness. There was no other past medical history of note. Until he fell ill, he had been working in a jewellery shop in Surat, Gujarat—a city where both falciparum and vivax malaria are endemic. On examination, nothing abnormal was found. The patient’s full blood count was normal; biochemistry tests, including a blood glucose measurement, also gave unremarkable results. Electrocardiography, ophthalmoscopy, examination of the cerebrospinal fl uid, and CT of the head all showed nothing of note. However, examination of the blood fi lm showed trophozoites of Plasmodium vivax, at a density of 16 200 per μL (fi gure). A rapid diagnostic test (FalciVax, Zephyr Biomedical Systems, Goa, India) indicated the presence of parasite lactate dehydrogenase, specifi c to P vivax, and the absence of histidine-rich protein 2, specifi c to P falciparum. 6 h after he arrived, the patient had another generalised seizure. He was immediately given intravenous quinine, as per the WHO guidelines for severe vivax malaria; in addition, anticonvulsant drugs were given. Over the next 12 h, the patient had a total of eight generalised seizures, with intervals of 30–120 min, without regaining full consciousness. 48 h after treatment began, the fever subsided, and the patient became fully conscious. Further blood tests—for dengue fever, leptospirosis, and HIV—gave negative results; repeat CT of the head, and electroencephalography, showed nothing remarkable. PCR, which was done as described by Kochar and colleagues, confi rmed that the patient had been infected by P vivax, but not P falciparum. The patient was discharged 8 days after his arrival. When last seen, in August, 2007, he was entirely well. P falciparum is known to cause cerebral malaria, which can manifest with seizures. The parasite multiplies in red blood cells, which adhere to the walls of small blood vessels, causing reduced cerebral blood fl ow. P vivax is less likely than P falciparum to cause severe illness— indeed, the typical 48 h interval between fevers, and benign course, have led to vivax malaria being termed “benign tertian malaria”. Classically, P vivax has not been thought to cause cerebral malaria. However, it is now known that severe P vivax infection can cause cerebral malaria—although, to our knowledge, this is the fi rst case in which the cause of seizures has been confi rmed as P vivax alone. How P vivax causes cerebral malaria is unclear, but recent studies indicate that the mechanism may be similar to that triggered by P falciparum. Other causes of seizures in malaria include hypoglycaemia, hyponatraemia, lactic acidosis—and other illnesses, such as epilepsy.

Revealing natural antisense transcripts from Plasmodium vivax isolates: Evidence of genome regulation in complicated malaria

Plasmodium vivax is the most geographically widespread human malaria parasite causing approximately 130-435 million infections annually. It is an economic burden in many parts of the world and poses a public health challenge along with the other Plasmodium sp. The biology of this parasite is less studied and poorly understood, in spite of these facts. Emerging evidence of severe complications due to infections by this parasite provides an impetus to focus research on the same. Investigating the parasite directly from infected patients is the best way to study its biology and pathogenic mechanisms. Gene expression studies of this parasite directly obtained from the patients has provided evidence of gene regulation resulting in varying amount of transcript levels in the different blood stages. The mechanisms regulating gene expression in malaria parasites are not well understood. Discovery of Natural Antisense Transcripts (NATs) in Plasmodium falciparum has suggested that these might play an important role in regulating gene expression. We report here the genome-wide occurrence of NATs in P. vivax parasites from patients with differing clinical symptoms. A total of 1348 NATs against annotated gene loci have been detected using a custom designed microarray with strand specific probes. Majority of NATs identified from this study shows positive correlation with the expression pattern of the sense (S) transcript. Our data also shows condition specific expression patterns of varying S and antisense (AS) transcript levels. Genes with AS transcripts enrich to various biological processes. To our knowledge this is the first report on the presence of NATs from P. vivax obtained from infected patients with different disease complications. The data suggests differential regulation of gene expression in diverse clinical conditions, as shown by differing sense/antisense ratios and would lead to future detailed investigations of gene regulation.

Dataset of natural antisense transcripts in P. vivax clinical isolates derived using custom designed strand-specific microarray.

Natural antisense transcripts (NATs) have been detected in many organisms and shown to regulate gene expression. Similarly, NATs have also been observed in malaria parasites with most studies focused on Plasmodium falciparum. There were no reports on the presence of NATs in Plasmodium vivax, which has also been shown to cause severe malaria like P. falciparum, until a recent study published by us. To identify in vivo prevalence of antisense transcripts in P. vivax clinical isolates, we performed whole genome expression profiling using a custom designed strand-specific microarray that contains probes for both sense and antisense strands. Here we describe the experimental methods and analysis of the microarray data available in Gene Expression Omnibus (GEO) under GSE45165. Our data provides a resource for exploring the presence of antisense transcripts in P. vivax isolated from patients showing varying clinical symptoms. Related information about the description and interpretation of the data can be found in a recent publication by Boopathi and colleagues in Infection, Genetics and Evolution 2013.