Serological diagnosis of dengue in laboratory practice in Kolkata.

Purpose: To find out the most suitable serological investigative procedures to diagnose dengue cases effectively in the laboratory practice identifying primary and secondary cases as well as period of suffering. Materials and Methods: Dengue suspected cases sent to the laboratory in 2012 in central Kolkata by the local physicians were categorised into seven panels according to the investigations asked for such as (1) only dengue‑specific NS1 antigen (2) only IgM antibodies, (3) NS1 + IgM + IgG antibodies, (4) only IgM and IgG, (5) NS1 + IgM, (6) NS1 + IgG and (7) only IgG. Results: Out of 1892 suspected cases, dengue was diagnosed in 725 (38.3%). Through panels I, II, III, IV, V, VI and VII, it was possible to diagnose dengue in (I) 35.98% (435/1209), (II) 37.5% (24/60), (III) 49% (173/354), (IV) 30.8% (68/221), (V) 60.5% (23/38), (VI) 40% (2/5) and (VII) 0 of cases respectively. Detail information such as confirmed diagnosis, duration of the disease (whether early or prolonged) and classification of primary and secondary dengue in such early or prolonged stages would only be possible in panel III, which information would be helpful for effective monitoring and treatment of dengue patients. In all other panels, merely fragmentary information would be obtained. Conclusions: Serodiagnostic tests dengue‑specific NS1 antigen and IgM and IgG antibodies when conducted simultaneously would be able to diagnose confirmed dengue cases categorising primary and secondary dengue along with the duration of the disease, whether early or prolonged.

Dengue serosurveillance in Kolkata, facing an epidemic in West Bengal, India.

Background & objectives: A dengue outbreak occurred throughout West Bengal, India starting from August 2005. The objectives of this study were: (i) documentation of suspected cases, confirmed by MAC ELISA; (ii) a longitudinal serosurveillance of dengue in Kolkata by detecting denguespecific IgG and IgM antibodies in suspected cases and to note the seasonal incidence; (iii) to get information about proportion of primary, secondary and old dengue cases and persons free from dengue in the population tested; and (iv) to get some idea to forecast advent of dengue and dengue epidemic/precipitation of DHF. Methods: The epidemiological data were collected from different sources including Calcutta School of Tropical Medicine and Government of West Bengal. For serosurveillance in Kolkata, serum of each suspected patient was examined for detection of IgG and IgM antibodies using the microwell ELISA dengue fever kit. Results: Altogether, 6293 ELISA IgM reactive cases were documented out of 12,059 persons (52.18%) tested in the whole of West Bengal, involving 18 districts with 34 deaths. Serosurveillance of 1668 persons from August 2005 to December 2007 in Kolkata showed that only 18.1% (302) suffered from dengue, 6.03% (101) from primary, 12.03% (201) from secondary dengue, 20.44% (341) were not sufferers of dengue and 61.45% (1025) were old dengue cases. Though stray dengue cases were found perennially, most of the cases occurred in the post-monsoon season, with a peak in September. Of dengue patients, 63.24% (191) were males. Secondary dengue cases outnumbered primary dengue cases. So, possibility of DHF would remain in all age groups and in those persons who suffered from dengue on earlier occasion. Dengue cases drastically reduced in two subsequent post-epidemic years (2006 and 2007). Interpretation & conclusion: Dengue serosurveillance studies may give some idea about advent, intensity, transmission season, seasonal incidence, waxing and warning, and impending epidemic of dengue and DHF. A large-scale active longitudinal serosurvey along with the study of vector capacity and vector competence would provide more correct information.

Studies on dengue and dengue haemorrhagic fever (DHF) in West Bengal State, India.

A large outbreak of dengue and dengue haemorrhagic fever (DHF) occurred from August to November 2005 involving all districts of West Bengal. Altogether 6293 persons were serologically diagnosed to be suffering from dengue through detection of IgM antibodies, with 27 (0.42%) seropositive deaths. In Kolkata alone 3967 persons were affected with 14 deaths. A total of 874 sera samples from febrile patients were quantitatively analysed for IgG and IgM antibodies using the IVD microwell ELISA dengue fever test kit. In 21.6%, no antibody was detected and 52.6% had only IgG antibodies. In 8.9% only IgM antibodies and in 16.8% both IgG, IgM antibodies were present, suggesting primary and secondary dengue respectively. About 10% of secondary dengue would develop DHF. As in this outbreak secondary dengue was 65.3% of total dengue cases, so of the 6293 dengue victims presumably, 3998 had secondary dengue, thus having risk of DHF in about 400 persons. Case fatality rate amongst DHF patients was 8.5%. This study also indicated that DHF would be a nagging problem in coming days. Age-group analysis of primary and secondary dengue cases revealed that although secondary cases occurred in all ages, more of primary cases belonged to younger ages (1-10) years and more of secondary cases in middle to older ages. Prevailing type during this outbreak was DEN3. This epidemiological study of an outbreak categorized prevalence of primary and secondary dengue, calculated risk factors for precipitation of DHF, model of which could be utilized to compare and evaluate future epidemiological pattern, where-ever and whenever applicable.

Malariogenic situations amounting to premunition in areas of Ajodhya Hills of District Purulia, West Bengal.

Since a long time, Purulia District in West Bengal has been endemic for malaria. In 1997 and 1998, the district contributed 12.4% (9932 out of 79,811) and 10.0% (13,248 out of 130,288) of malaria cases respectively occurring in West Bengal, resulting 9.45% (7 out of 74) and 5.5% (4 out of 72) of deaths respectively in the state. ABER of the district was 10.4% in 1997 and 8.5% in 1998.

Emerging Plasmodium falciparum in an endemic area in Calcutta.

Calcutta is now intensely malarious. Malarial infections are detected in every month. In an endemic area in central Calcutta a year-long study from August 1996 to July 1997 reveals that 31.47% of all cases are due to Plasmodium falciparum infection. A competition is going on between P vivax and P falciparum to gain upperhand. An equilibrium is there in the month of January (1997), when P vivax and P falciparum cases constitute 51.13% and 49.43% respectively. The highest and lowest percentage of P falciparum infection is in December 1996 (67.98%) and in May 1997 (0.89%) which is just reverse in the case of P vivax in December 1996 (33.60%) and in May 1997 (99.10%). Three imported cases of P malariae have been detected but the patients cannot be traced. Six cases of mixed infections have been found.

Urban malaria vector biology.

One of the main reasons for the set-back in the urban malaria control programme is the peculiar biobehaviour of the principal urban malaria vector Anopheles stephensi. Certain relevant facts such as incrimination as the vector of malaria, sibling or biological species, resting habitat, manlanding behaviour, seasonal prevalence, blood meal analysis, longevity, parity status, daily survival and mortality rates of adults, breeding habitats and vertical distribution of larvae of An. stephensi have been discussed. Determination of density of the vector using various parameters and their relation to malaria endemicity in an urban situation have been reviewed. An. stephensi has become resistant to DDT, HCH, malathion and propoxur in many places in India. Hence for control source reduction, use of predators such as fish and biolarvicides such as Bacillus thuringiensis var israelensis H14 and B. sphaericus, personal protection, i.e., use of appropriate clothing, bed nets, indigenous repellents, etc., information, education and communication (IEC) are to be stressed.

Effect of DDT on Phlebotomus sandflies in Kala-Azar endemic foci in West Bengal.

Phlebotomous argentipes, the vector of Kala-azar was found susceptible to DDT and found to reappear in the nine months after one time DDT spray at the rate of lg/m2 in three endemic foci of districts North and South 24-Parganas of West Bengal. Ph. papatasi, the other predominant species found resistant to DDT appeared within one month of DDT spray.

An institutional outbreak of hepatitis E--reported first time from Calcutta city.

A sudden outbreak of hepatitis occurred in a micro-epidemic form, amongst the staff members of the School of Tropical Medicine, Calcutta, during May-June, 1995. A total of 21 persons developed jaundice, out of whom 11 members who attended the Virology Department and were tested for detection of different serological markers of hepatitis by ELISA. All the sera (N = 11) showed evidence of non-A, non-B infection by process of exclusion and 9 of the above sera showed evidence of anti-HEV when tested specifically. This is the first documented outbreak of viral hepatitis in respect of Calcutta.

Susceptibility status of Phlebotomus argentipes to DDT, dieldrin and malathion in Hoogly, West Bengal.

Susceptibility tests were carried out with DDT (4%), dieldrin (0.4%) and malathion (5%) using the WHO test kits against Phlebotomus argentipes sandflies collected from Dankuni, situated in Hoogly district, 21 km from Calcutta, West Bengal. P. argentipes was found to be susceptible to all the three insecticides tested. LT 50 was calculated to be 10.6 minutes, 10.2 minutes and 2.8 minutes for DDT, dieldrin and malathion against the flies.

Transmission of Sarcoptes scabiei from animal to man and its control.

Outbreak of Sarcoptes scabiei in animals spilling over to man in close association was observed in two adjacent villages, Fewgram and Nurpur in the district of Birbhum, West Bengal, from mid-November to mid-December, 1991. Nineteen goats and one calf who did not receive any treatment died of sarcoptic manage. All infected animals got cured with external application of deltamethrin, a synthetic pyrethroid and triazapentadiene. Human cases were treated successfully with benzene hexachloride (2%).

A simple medium without blood modified for successful isolation & cultivation of LD bodies.

A simple growth medium for primary isolation and subsequent cultivation of Leishmania donovani promastigotes without using whole blood is described. This medium is modified from Aljeboori's biphasic medium (used originally only for cultivation), containing only beef extract, peptone, sodium chloride, bactoagar and foetal calf serum (FCS). We have modified the medium by adding glucose and ascertaining the pH in the solid phase and by drastically reducing (91%) FCS in the liquid phase. The medium helps in isolation of L. donovani promastigotes from kala-azar patients, in addition to luxurious growth of parasites. The medium is simple, reliable, reproducible and convenient, with minimal interference in using the parasitic cells for immunological, molecular and isoenzyme studies.