Prafulla Dutta

West Nile virus infection, Assam, India.

To the Editor: West Nile virus (WNV) is a mosquito-borne flavivirus. Sporadic infections with this virus have been found in Africa, Europe, Asia, and the United States. In humans, most infections with WNV cause subclinical or a mild influenza-like illness; encephalitis occurs in some (1). In India, antibodies against WNV were first detected in humans in Bombay in 1952 (2). Virus activity has been reported in southern, central, and western India. WNV has been isolated in India from Culex vishnui mosquitoes in Andhra Pradesh and Tamil Nadu, from Cx. quinquefasciatus mosquitoes in Maharashtra, and from humans in Karnataka State (3). n nAssam (26°–27°30′N, 89°58′–95°41′E) is the most populated state in northeastern India; it contains ≈50% of the 38.8 million inhabitants of northeastern India. Japanese encephalitis virus (JEV) has caused sporadic epidemics in Assam since 1976. Studies conducted during 2000–2002 in Assam showed that 187 (53.7%) of 348 persons with acute encephalitis syndrome were infected with JEV (4). JEV-negative persons also showed symptoms of neurotropic viral infection. n nSuspecting the presence of some other closely related flavivirus in this region, we screened samples from persons with acute encephalitis syndrome for WNV in 2006. To our knowledge, no study has been conducted on the prevalence of WNV in this region. We report WNV activity in the state of Assam in northeastern India. Ethical approval for this study was obtained from the institutional ethical committee, Regional Medical Research Center, Dibrugarh, India. n nA JEV vaccination campaign (SA14-14-2 vaccine) was started in Assam during May 2006. During its first phase, children 1–15 years of age in Dibrugarh and Sivasagar Districts were vaccinated. Mosquito surveillance in the study area and in an earlier study (5) identified Cx. vishnui mosquitoes. n nDuring the study period, 103 serum samples and 88 cerebrospinal fluid samples were obtained from 167 patients with acute encephalitis syndrome admitted to the Assam Medical College and Hospital in Dibrugarh, which administers to the health needs of >7 districts of Upper Assam and neighboring states of Arunachal Pradesh and Nagaland. Among the 167 patients, 124 (74.2%) were children <15 years of age. n nAmong the 103 serum samples, 80 were positive for immunoglobulin (Ig) M against JEV (IgM monoclonal antibody–capture ELISA; National Institute of Virology, Pune, India) and 12 (11.6%) were positive for IgM against WNV (IgM antigen-capture ELISA; Panbio, Sinnamon Park, Queensland, Australia). These samples were from persons in 4 districts in Assam (Dibrugarh, Golaghat, Sivasagar, and Tinsukia) and negative for IgM against JEV (Table). Follow-up was conducted for 9 patients; 3 died, and 1 was lost to follow-up. n n n nTable n nIncidence of JEV and WNV infections among patients with acute encephalitis syndrome, Assam, India* n n n nVirus-neutralizing antibody titers against JEV and WNV were estimated in pig kidney epithelial cells by using JEV (isolate 733913) and WNV (isolate 68856) and a cytopathic-effect assay in 96-well tissue culture plates (6). Mouse polyclonal antibodies against JEV and WNV and nonimmune serum samples were included in the assay. Of 9 paired serum samples, 6 showed neutralizing antibody for WNV, of which 4 showed a 4-fold increase in antibody titer. The remaining 3 paired samples showed cross-reactivity with WNV (titer <80) and JEV (titer <40). n nAll 12 WNV-infected patients had high fever and headache. Convulsions (6 patients), altered sensorium (7 patients), vomiting (5 patients), and neck rigidity (2 patients) were also observed. Signs and symptoms at the time of hospitalization and at follow-up for 6 months (at 3-month intervals) were similar for persons infected with JEV and those infected with WNV. Neurologic sequelae observed at <6 months follow-up were impaired memory (6 patients), irritable behavior (5 patients), impaired hearing (3 patients), incoherent speech and disorientation (1 patient), breathing difficulty (1 patient), impaired speech (1 patient), and quadriparesis (1 patient). n nWe identified WNV in regions of Assam to which JEV is endemic. The finding indicates that WNV might be the cause of a substantial number of acute encephalitis syndrome cases in this region. Fever and headache were the most common signs and symptoms, as reported (7). There were 3 deaths (all children) in 13 patients. Our results corroborate a similar observation in the Kolar District of Karnataka (8). In contrast, in western countries, the attack rate and case-fatality rate for WNV infection are higher among immunocompromised elderly patients (9). Our findings may be caused by strain variations and host susceptibility to the virus. Identification of circulating genotypes of WNV and its vectors and epidemiologic studies are needed to obtain additional information on WNV infection in this region and identify WNV as a cause of acute encephalitis syndrome.

A comparison of clinical features of Japanese encephalitis virus infection in the adult and pediatric age group with Acute Encephalitis Syndrome

BACKGROUNDnJapanese encephalitis (JE) has traditionally been regarded as a disease of children. The age shift in JE patients in Assam, India in last few years has become a cause of concern. Comparison on clinical features of adult and pediatric JE patients has not been evaluated.nnnOBJECTIVEnTo compare clinical features of adult and pediatric with JE virus infection.nnnSTUDY DESIGNnFrom January 2008 to January 2010, 550 hospitalized patients with Acute Encephalitis Syndrome were enrolled. 259 (47.1%) were serologically confirmed as JE of which 66.4% were adult and 33.6% were pediatric. Data extracted from these patients were analyzed.nnnRESULTSnFever was the most common symptom in both the adult and pediatric. When compared with adult, significantly higher percentage of pediatric had neck rigidity, convulsions, abnormal behavior, seizures and elevated aspartate transaminase (P<0.05). Serum bilirubin levels were higher in 2.3% of adult but normal in all the pediatric. We found significantly higher mean elevated level of protein and WBC in CSF in adult (P<0.001) and mean elevated aspartate transaminase level (P<0.001) in pediatrics. There was no difference in mortality rate between pediatric and adult (8.2% vs. 4.4%, P=0.647).nnnCONCLUSIONSnThis study provides some significant differences in clinical features of pediatric and adult with JE. Age shift may be due to the invasion of the disease into new demography or some change in the virus strain over time. The Government of India has initiated an adult JE vaccination programme for the first time in Assam in 2011.

The Effect of Insecticide-Treated Mosquito Nets (ITMNs) on Japanese Encephalitis Virus Seroconversion in Pigs and Humans

The effect of insecticide-treated mosquito nets (ITMNs) on Japanese Encephalitis (JE) virus seroconversion in pigs and humans was studied in Assam, Northeast India. A sharp reduction of seroconversion rate in human and pig was found in treated localities after intervention. A marked reduction was achieved in humans (risk ratio [RR] = 0.28, 95% confidence interval [CI] = 0.16-0.49) and pigs (RR = 0.21, CI = 0.11-0.40) in the Kollolua locality where ITMNs were used on both humans and pigs compared with the other two area, Athabari and Rajmai, where ITMNs were covering only either humans or pigs. Monitoring of the mosquito population in and around cattle sheds during dusk revealed no significant decline (P > 0.05) of vector density during the post-intervention period in study localities. In spite of the high preponderance of potential JE vector outdoors during the post-intervention period, an encouraging line of defense against circulation of JE virus through the use of ITMNs can be achieved in endemic areas.

Characterization of West Nile virus (WNV) isolates from Assam, India: Insights into the circulating WNV in northeastern India

West Nile virus (WNV) is a mosquito-borne flavivirus that causes subclinical symptoms, febrile illness with possible kidney infarction and encephalitis. Since WNV was first serologically detected in Assam during 2006, it has become recognized as an important etiological agent that causes acute encephalitis syndrome (AES) in addition to endemic Japanese encephalitis virus (JEV). Therefore, isolating and characterizing the currently circulating strain of WNV is important. The virus was isolated from the cerebrospinal fluid (CSF) of two patients that presented with AES. The genotyping of the isolates HQ246154 (WNIRGC07) and JQ037832 (WNIRTC08) based on the partial sequencing of 921 nucleotides (C-prM-E) of the genome placed them within lineage 5 along with other Indian strains isolated prior to 1982, but the present circulating virus formed a distinct subclade. The derived amino acid sequence alignment indicated substitution in A81T and A84P of the capsid region in HQ246154. A cross-neutralization assay suggested substantial antigenic variation between isolates. The pathogenesis in mice that suggested the circulating WNV was neuroinvasive and comparatively more pathogenic than previous strains from India.

Epidemiological concordance of Japanese encephalitis virus infection among mosquito vectors, amplifying hosts and humans in India

A temporal relationship of Japanese encephalitis virus (JEV) transmission in pigs, mosquitoes and humans revealed that sentinel pig seroconversions were significantly associated with human cases 4 weeks before (P = 0·04) their occurrence, highly correlated during the same time and 2 weeks before case occurrence (P < 0·001), and remained significantly correlated up to 2 weeks after human case occurrence (P < 0·01). JEV was detected in the same month in pigs and mosquitoes, and peaks of pig seroconversion were preceded by 1-2 months of peaks of infection in vectors. Kaplan-Meier analysis indicated that detection of JEV-positive mosquitoes was significantly associated with the median time to occurrence of seroconversion in pigs (P < 0·05). This study will not only help in predicting JEV activity but also accelerate timely vector control measures and vaccination programmes for pigs and humans to reduce the Japanese encephalitis risk in endemic areas.

First evidence of chikungunya virus infection in Assam, Northeast India

During June-September 2008, an illness characterized by fever, headache and joint pain was reported in Assam state, northeast India. It presented characteristic features resembling chikungunya or dengue virus infection based on clinical symptoms. Dengue and chikungunya IgM antibody was detected in 10.0% (28/280) and 3.6% (10/280) patients respectively. The chikungunya positive patients did not travel to and from any endemic region confirming indigenous transmission. Persistent arthralgia and hearing loss has been observed in a recovered patient. Entomological surveys revealed the presence of vectors viz. Aedes aegypti and Aedes albopictus. This is the maiden report of chikungunya occurrence in Northeast India.

Leptospirosis presenting as acute encephalitis syndrome (AES) in Assam, India

Abstract Objective To establish leptospirosis as a new aetiology of the patients presenting acute encephalitis syndrome (AES). Methods Japanese encephalitis, West Nile, Dengue and Chikungunya negative samples were tested by IgM capture ELISA for leptospira specific IgM. For further confirmation, the IgM positive samples were subjected to Microscopic agglutination test (MAT). The clinical details and laboratory findings of the positive patients were recorded. Results We report 8 cases of leptospirosis presenting as AES, proven on IgM capture ELISA and confirmed by MAT. Fever (100%) and altered sensorium (62.5%) were two most common symptoms. Low haemoglobin (7.5 ± 2.8) g/dL, elevated blood urea (79.16 ± 46.43) mg/dL, serum creatinine (1.5 ±1.2) mg/dL, SGOT (66.5 ± 14.84) U/L and SGPT (70.5 ± 4.9) U/L were observed in positive patients. Conclusions This is the maiden study reporting leptospirosis as a new aetiology of the patients presenting AES. Establishing aetiology is very important for a successful therapy at least in treatable conditions like leptospirosis.

Scrub Typhus Leading to Acute Encephalitis Syndrome, Assam, India

To determine the contribution of Orientia tsutsugamushi, the agent of scrub typhus, as a cause of acute encephalitis syndrome (AES) in Assam, India, we conducted a retrospective study of hospital patients with symptoms of AES during 2013–2015. Our findings suggest that O. tsutsugamushi infection leads to AES and the resulting illness and death.

Malaria control in a forest fringe area of Assam, India: a pilot study.

A study was conducted to evaluate the preventive efficacy of insecticide-treated mosquito nets (ITMNs) and mosquito repellent (MR) in a malaria-endemic foothill area of Assam, India, with forest ecosystem. During the first year, a survey was conducted in four demarcated sectors (A-D) to observe the malaria endemicity and vector prevalence patterns before implementing intervention measures. All four sectors were endemic for malaria. The prevalence of established malaria vectors such as Anopheles dirus, A. minimus and A. philippinensis was observed. During the second year, intervention measures were implemented in the four sectors as follows: A, ITMN + MR; B, ITMN; C, MR; D, no intervention. The most effective intervention was in sector A, followed by sectors B and C. Sectors A and B exhibited significantly higher (P < 0.001) malaria protective efficacy during both the first and second years of intervention compared with sector D. The total vector population in the three intervention sectors decreased significantly compared with that of the non-intervention one. Information-education-communication activities motivated the residents to participate actively in the intervention programme. The finding could be an effective model for containment of high malaria morbidity in inaccessible forest fringe areas of the northeastern region of India.

Japanese encephalitis epidemiology in Arunachal Pradesh, a hilly state in northeast India

Abstract Objective To confirm Japanese encephalitis (JE) cases from the state of Arunachal Pradesh (AP), India for the first time. Methods Suspected acute encephalitis syndrome (AES) cases were screened from 2005-2010. The cases were initially tested for antibodies against JE by using IgM MAC ELISA kits (National Institute of Virology, Pune). RNA was extracted from the cerebrospinal fluid (CSF) samples followed by molecular amplification of JE virus specific gene primer. The data obtained were used to calculate relative risks between the age groups and between the genders. Epi info 6.0 was used for the statistical analysis. Results Presence of JE cases in the state of AP, India was established. JE cases from 10 out of 16 districts were recorded. As part of control and preventive measures, mass vaccination for children (0-15 years) by SA-14-14-2 JE vaccine was taken up in 2010 in the district of Lohit. Vaccination coverage of 83.09% among the target population was achieved. Conclusions The study presents the first report of confirmed JE cases from the state of AP, India. This finding attracts attention as JE cases are rarely seen to occur in hilly places.