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National Institute of Communicable Diseases |
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ANNUAL REPORT 1997 |
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NICD Branch, Bangalore Plague,
a disease of great antiquity was a major health problem throughut India till
the mid twentieth century A.D. The authenticated Plague epidemic started in the
year 1895-96 and reached its peak in 1907. During the two decades from
1898-1918 there were over 25 million deaths in India (Including Pakistan and
Bangladesh). The decimal death rated to plague in India per 1,00,000 population
during these decades were 183.3 and 133.8 respectively. Since then morality due
to plague has declined reaching zero level in 1967. Though, human plague had
not been reported from India since 1966, yet sporadic cases of suspected human
plague had been reported and at times localised sylvatic plague incidence
encountered in the last decade from Himachal Pradesh and South India tri
junction of Andhra Pradesh, Tamil Nadu and Karnataka. During the last episode
of Plague in South India (1961-63), NICD undertook investigations on human and
wild rodent Plague from 1963-1972. Later the Government of India felt the need
of having a National Unit at Bangalore. Plague Surveillance Unit of NICD has
been functioning since 1976. During the recent human plague outbreak at Beed,
Maharashtra and Surat, Gujarat, the NICD, Plague Surveillance Unit was actively
involved in diagnosis of the cases and took appropriate anti plague measures to
combat the disease. The broad objectives of the Unit are: §
To
study the population stress under which rodent migration takes place from
sylvatic to peripheral commensal habitates. §
To
study the shift in rodent population consequent to interference in ecology in
urban, semi urban and rural situations in endemic areas. §
To
map out the fauna of rodent fleas in the country vis-à-vis their sustaining
hots particularly with reference to Xenopsylla
cheopis and Xenopsylla astia. §
To
work out the dynamics of flea infection interchange on hosts at ecological
interfaces. §
Serological
investigations of rodent, bacteriological investigations for isolation of
plague organism from rodent and vector fleas. §
Collection
of epidemiological information regarding rodent epizootic and human cases of
lymphadenopathy illness simulating plague and its detailed investigations. §
To
work out the susceptibility status of fleas to various insecticides for flea
control. §
Evaluation
of mechanical methods and rodenticides for the control of rodents in different
ecological situations. The
Unit has three sections i) Entomology ii) Bacteriology iii) Serology Maintenance
of flea colonies Cyclic
colony of different strains of X.cheopis
and X-astia are being maintained
under controlled laboratory conditions i.e. 25±20C and 75% R.H. Research Projects 1. Surveillance of plague To
detect evidence of Plague antibodies among wild rodents in order to ascertain
the current status of sylvatic plague in the trijunctionof three bordering
states of Andhra Pradesh, Tamil Nadu and Karnataka, serological surveillance
was carried out during the year 1997. A total of 36884 rodent sera and 1695 dog
sera samples were collected. Out of these 12984 rodents and 606 dog sera were
collected from Anti Plague Unit, Palamaner, Andhra Pradesh; 19636 rodents and
1089 dog sera were collected from Kolar, Karnataka, 3934 rodents from
Dharmapuri district of Tamil Nadu and 366 rodents from Attibele, Bangalore
rural district, Karnataka. Out of these rodents 25807 were Tetra indica Cauveri (water house), 4489 Bandicoota bengalensis and
6588 Rattus rattus. The ratio of
Domestic and wild rodents was found to be 1:4.6. During the year none of the
rodent sera samples showed the presence of plague antibodies as assessed by
Passive Haemagglutination Test using fraction 1 antigen. During the year 267
human sera samples were collected from Devarapali and surrounding villages in
Dharmapuri district, Tamil Nadu. Of the 267 samples eight (8) samples found to
be positive for plague antibodies. Necessary anti plague measures were
undertaken in the area to prevent the occurrence of human bubonic plague
outbreak in the area. 2. Bacteriological investigations for
Y.pestis Rodent
organs collected from T.indica and B.bengalensis were cultured and bi-polar
bodies were characterised for the isolation of Y.pestis. Of the 8034 organs examined none of the samples collected
from different plague control units were found to be positive for Y.pestis. During the year, 1383 organ
smears collected from heart, lung, liver and spleen were examined by direct
microscopy for the detection of bi-polar bodies. All the smears were found to
be negative. 3. Rodent ectoparasite (REP) survey State
Plague Control Units i.e. Plague Control Unit, Kolar, Karnataka State and Anti
Plague Unit, Palamaner, Andhra Pradesh conducted routine Ectoparasite Surveys
every fortnight. The flea samples collected during the survey were transported
to NICD, Plague Surveillance Unit, Bangalore for processing and identification.
During the year 1997 a total of 3559 and 479 Rattus rattus were collected from
domestic situations during REP survey from Palamner and Kolar respectively. The
total flea indices and specific flea indices for X.cheopis for Palamner and Kolar were calculated to be 1.05/0.65
and 1.1/0.7 respectively. Specific flea index for X.astia for Palamner and Kolar were found to 0.4. 4. Detection of sylvatic plague foci
at Mamla village, Beed dist. Aurangabad in Maharashtra and Surat in Gujarat A total
of 116 Tetra indica, 236 Rattus
rattus and 2 B.bengalensis (Total-456
rodents) could be collected by digging and trapping during the visit to Beed,
Aurangabad and Surat Area in order to detect the evidence of plague antibodies
among wild and commensal rodents. Total flea indices for Beed, Aurangabad and
Surat were calculated to be 0.7, 1.1 and 0.8 respectively. All the rodent sera
samples were found to be negative for plague antibodies by PHA test. To detect
evidence of active plague transmission in the areas all the wild and commensal
rodents were dissected. All the rodents were found to be negative for
pathological changes due to Y.pestis,
410 rodent organs smears collected from the dissected rodents were examined but
none of the smears was found to be positive for bi-polar bodies. Rodent organ
samples collected in CBT and the sera samples were transported to NICD,
Bangalore. No colony of Y.pestis
could be raised from the samples. 5. Studies on Japanese Encephalitis
outbreak in Bellary District, Karnataka Cases
and deaths due to JE have been reported from few districts of Karnataka since
1981. The districts reporting JE cases during 1997 from Karnataka include
Bellary Raichur, Chitradurge, Kolar, Mandya and Bangalore (Rural and Urban). In
addition a few cases were being reported from Karnool and Anantapur district of
Andhra Pradesh. Japanese encephalitis was recognised in Bellary district since
1981. During
1997 the total number of cases from Bellary and adjoining districts of
Karnataka (Raichur and Chitradurge Districts) and Andhra Pradesh (Anantapur and
Karnool Districts) was reported to be 294 and 57 deaths. The incidence of
deaths due to JE was found increasing to the highest level in 1997 after 10
yrs. The highest attack rate was found in children 0-14 yrs. old. Age specific
attack rate was highest in 5-8 years age group. Number of male cases was 1.3
times that of the female cases. Human
blood sera samples collected during the survey were sent to NICD, Delhi for
serological tests. All the adult JE vector species were collected from indoor
situations. Survey in permanent water collection paddy fields, irrigation
channels bordering paddy fields and pockets in the riverbeds with aquatic
vegetation revealed the presence of Cu.tritaeniohynchus,
An hycanus and An.subpictus in large densities. Almost nil adult densities in
indoor sprayed structures but high larval densities of Cu.vishnui group of mosquitoes in peri-domestic situations revealed
that the species is exophilic and exophagous in nature and there was no impact
of DDT on the the mosquito population. JE transmission in the area was appeared
to be extra-domicillary in nature. The
combination of steady development of resistance, less impact of DDT on vector
population, economic burden on vector control programme and vast areas
labelling as perinnial vector breeding sources demand environmental management
and biological methods as routine measures for vector control. |
