Clinical and etiological profile of acute febrile encephalopathy in eastern Nepal.

Objective. To investigate the clinical and etiological profile of acute febrile encephalopathy in children presenting to a tertiary care referral center of Eastern Nepal. Methods. 107 children (aged 1 month to 14 yr) presenting to the emergency with fever (> 380 C) of less than 2 wk duration with altered sensorium with/ or without seizure were prospectively investigated for etiological cause. The investigations included blood and CSF counts, blood and CSF cultures, peripheral smear and serology for malarial parasite, and serology for Japanese encephalitis (JE) virus. Other investigations included EEG and CT or MRI wherever indicated. Results. The most common presenting complaints apart from fever and altered sensorium were headache and vomiting. Convulsions, neck rigidity, hypertonia, brisk deep tendon reflexes, extensor plantar response and focal neurological deficits were seen in 50%, 57%, 22.4%, 28%, 39.3% and 9.3% of the subjects, respectively. The diagnoses based on clinical presentation and laboratory findings were pyogenic meningitis in 45 (42%), non JE viral encephalitis in 26 (25%), JE in 19 (18%), cerebral malaria in 8 (7%), herpes encephalitis and tubercular meningitis in 4 (4%) each, and typhoid encephalopathy in 1 case. Conclusion. Pyogenic meningitis and viral encephalitis including JE are the most common causes of acute presentation with fever and encephalopathy. Preventive strategies must be directed keeping these causes in mind.

Outdoor resting preference of Culex tritaeniorhynchus, the vector of Japanese encephalitis in Warangal and Karim Nagar districts, Andhra Pradesh.

BACKGROUND & OBJECTIVES: Entomological investigations were carried out in Warangal and Karim Nagar districts of Andhra Pradesh during viral encephalitis outbreak in July 2003. METHODS: Adult mosquito collections in outdoor were done using sweep cage method and in indoor with the help of aspirator tube and flash light. Larval collections were done by dipping method. JE virus positivity was tested by IgM capture ELISA test. RESULTS: Outdoor collections revealed presence of Culex tritaeniorhynchus, Cx. bitaeniorhynchus and Cx. gelidus and in indoor collections--Cx. quinquefasciatus, Cx. tritaeniorhynchus, An. vagus and An. subpictus. In the outdoor collections Cx. tritaeniorhynchus was predominant (96.3% of total collection). Three samples out of 55 serum samples from human cases and five from contacts showed the presence of antibodies against JE virus. INTERPRETATION & CONCLUSION: Cx. tritaeniorhynchus, a known vector of JE is predominant in outdoors and playing a main role in JE transmission in this area. Vector control aimed at the outdoor resting population might limit virus circulation in the mosquito vertebrate host cycle and prevent human infection.

Biting behaviour and biting rhythm of potential Japanese encephalitis vectors in Assam.

Studies on biting behaviour and biting cycles of medically important mosquitoes were carried out in Madhupur village and Tarajan tea estate of upper Assam. Collections were made off human baits outdoors and indoors and off cattle bait outdoors from August 1991 to July 1992. Human bait collections were performed using the 'stationary direct bait' technique. A total of 9,072 adult host seeking female mosquitoes representing 26 species and 5 genera were collected off baits of which 36.9% were collected off human baits and the rest from cattle. All mosquitoes were primarily zoophilic, although significant numbers were collected biting man outdoors. Biting preferences of important Japanese encephalitis (JE) vectors for man and cattle were studied using outdoor man:outdoor cattle ratio (attraction ratio = AR). Culex quinquefasciatus was attracted towards human baits the most (AR = 8.1:1), followed by Cx. bitaeniorhynchus (AR = 1.6:1) and Mansonia annulifera (AR = 1.3.1). The hourly biting activity of important JE vectors throughout the night on two bait types was also studied using three point moving averages. Hierarchical agglomerative cluster analysis was used to compare and classify mosquitoes on the basis of their similarity in biting rhythms.

Vectors of Japanese encephalitis virus (JEV): species complexes of the vectors.

The vectors of JEV are Cx. tritaeniorhynchus, Cx. vishnui, Cx. pseudovishnui, Cx. gelidus, Cx. fuscocephala, Cx. quinquefasciatus, Cx. pipiens pallens, Cx. bitaeniorhynchus, Cx. annulirostris, Aedes togoi, Ae. japonicus, Ae. vexans nipponii, Anopheles annularis and An. vagus. Cx. tritaeniorhynchus is in the tritaeniorhynchus complex, breeds in rice fields, ground pools in vast areas. Two types of mating behavior, eurygamy and moderate stenogamy were detected. In the case of the eurygamy type, the mosquitoes were from Southern Thailand and hilly areas near Kanchanaburi, Thailand. Female mosquitoes are usually dark in color, the cibarial armature has rod teeth and the posterior end of the cibarial armature is bowl shaped with a typical rim. The rim of the bowl is everted. The moderate stenogamy type were mosquitoes from the plain areas such as Bangkok, Ayutthaya, Suphan Buri and Saraburi. The posterior end of the cibarial armature is bowl shaped with a stout rim. The larvae were characteristic in their siphon index, antennal index, hair O of prothoracic segment, and comb scale number and arrangement. Cx. tritaeniorhynchus summorosus from Japan, Los Banos and Luzon, Philippines, differed from Cx. tritaeniorhynchus in that on the lateral plate of the phallosome tritaeniorhynchus teeth are somewhat weakly developed and only gently curved whereas in tritaeniorhynchus summorosus they are strongly developed, considerably longer, and sharply recurved. The siphons of larvae are short, the sides parallel and the apex truncate in tritaeniorhynchus whereas in tritaeniorhynchus summorosus they are long and slender. Cx. tritaeniorhynchus var. siamensis is possibly present. Colonies have been maintained in the Department of Medical Entomology for 31 generations. The characteristics are in hair O (short, less than 20 branches, and without secondary branching and the larval siphon (short and broad where the others are long). Cx. vishnui and Cx. pseudovishnui are in the vishnui complex. Cx. quinquefasciatus and Cx. pipiens pallens are in the Cx. pipiens complex comprising: (1) Cx. pipiens; (2) Cx. quinquefasciatus Say; (3) Cx. molestus Forskal; (4) Cx. pipiens pallens; (5) Cx. australicus; (6) Cx. globocoxitus. Anopheles annularis is a species complex evidenced by two types of polytene chromosomes.

Studies on Japanese encephalitis vectors in Indonesia.

Entomologic surveys indicated that JE vectors in Indonesia are Cx. tritaeniorhyncus and Cx. gelidus. In most study areas, the former were predominant among all the culicine mosquitoes. The seasonal abundance of the two JE vector species was correlated significantly with the rainfall. The virus activity was parallel to the seasonal fluctuation of the vectors suggesting that the transmission of the disease would depend on the population dynamics of the vectors.