Serological evidence of rickettsial infections in Delhi.

Background & objectives: Rickettsial infections remain under-diagnosed due to lack of diagnostic facilities in developing world. Here we present our experience at National Centre for Disease Control, Delhi, about a serosurvey done in Delhi for rickettsial disease with easy to perform low cost, low expertise Weil Felix test. Methods: On the basis of cut-off titre obtained in healthy population, Weil Felix test results were interpreted along with clinical data. Entomological investigation was also carried out in select areas of Delhi. Rodents were trapped from houses and gardens and vector mites were collected. Results: When serum samples were collected during initial 5 yr period from patients with fever of unknown origin, seropositivity was 8.2 per cent whereas when rickettsial infection was kept as one of the differential diagnosis by clinicians seropositivity increased to 33.3 per cent. Rickettsial infections detected were scrub typhus (48.2%) followed by spotted fever group (27.5%) and typhus group (6.8%) during 2005-2009. In preliminary entomological survey vector mite Leptotombidium deliense was found on rodents. Interpretation & conclusions: Our findings showed that results of Weil Felix test should not be disregarded, rather clinically compatible cases should be treated to save lives.

Humoral response to rabies vaccines in pet dogs.

Humoral immune response was studied in dogs vaccinated with different tissue culture vaccines commonly used for immunization of dogs in India. The results revealed that after single dose of vaccination only 56% dogs developed protective titer (> or = 1:8). The response of the three vaccines used in the study was not similar, highlighting the need to maintain post marketing surveillance.

Prompt laboratory diagnosis in timely containment of a plague outbreak in India.

A focal outbreak of pneumonic plague occurred in a hamlet of village Hatkoti, district Shimla, Himachal Pradesh in the first fortnight of February, 2002. A total of 16 cases with 4 deaths were reported. Diagnosis of plague was confirmed by the laboratory in 10 (63%) cases. Y. pestis was isolated from clinical samples of 3 cases and confirmed by bacteriophage lysis. Molecular tests confirmed the presence of Y. pestis specific pla and F1 genes in 4 cases; DNA fingerprinting had identity with the known sequence of plague bacilli. Paired samples from 5 cases showed more than 4 fold rise and 1 case showed more than 4 fold fall in antibodies against F1 antigen of Y. pestis. The present communication emphasises that timely and systematic laboratory investigations give confirmatory diagnosis in shortest possible time which forms the backbone of the outbreak control in a timely fashion and prevents confusion and controversy.

Quick control of bubonic plague outbreak in Uttar Kashi, India.

A localized outbreak of bubonic plague occurred in village Dangud (population 332), district Uttar Kashi, Uttaranchal, India in the second week of October 2004. 8 cases were considered outbreak associated based on their clinical and epidemiological characteristics; 3 (27.3%) of them died within 48 hours of developing illness. All the 3 fatal cases and five surviving cases had enlargement of inguinal lymph nodes. None of them had pneumonia. The age of the cases ranged from 23-70 years and both sexes were affected. No such illness was reported from adjoining villages. The outbreak was fully contained within two weeks of its onset by supervised comprehensive chemoprophylaxis using tetracycline. A total of approximately 1250 persons were given chemoprophylaxis in three villages. There was no clear history of rat fall in the village. No flea was found on rodents or animals. 16 animal serum samples were found to be negative for antibodies against F-1 antigen of Y. pestis. However, Y. pestis was isolated from two rodents (Rattus rattus and Mus musculus) trapped in the village. One case and three animal sera showed borderline sero-positivity against rickettsial infection. The diagnosis of plague was confirmed by detection of four fold rise of antibody titre against F-1 antigen of Yersinia pestis in paired sera of three cases (one of the WHO approved criteria of diagnosis of confirmed plague). This outbreak and the occurrence of earlier outbreaks of plague in Surat (Gujarat) and Beed (Maharashtra) in 1994 and in district Shimla (Himachal Pradesh) in 2002 confirm that plague infection continue to exist in sylvatic foci in many parts of India which is transmitted to humans occasionally. Thus, there is a strong need for the States to monitor the plague activity in known sylvatic foci regularly and have a system of surveillance to facilitate prompt diagnosis and treatment of cases to control the disease. This investigation highlights that with high index of suspicion the disease can be diagnosed early and mounting of supervised comprehensive response can prevent the disease to proceed to pneumonic stage where man to man transmission gets established and outbreak assumes larger dimensions.

An outbreak of human anthrax in Mysore (India).

Anthrax is a zoonotic disease caused by Bacillus anthracis. Intestinal anthrax though a rare entity mostly ends with fatal outcome. Very few cases of intestinal anthrax are reported. Present outbreak of intestinal anthrax is unique in itself that four cases succumbed to the illness within a span of 48-72 hours in a small hamlet of Mysore district of Karnataka, after consuming diseased deer meat. Confirmation of the diagnosis was carried out at NICD, Delhi by bacteriological culture isolation, biochemical tests, animal pathogenicity and polymerase chain reaction (PCR). This outbreak clearly indicates surveillance of anthrax in animals in endemic areas is an essential part in the control of the disease with intersectoral coordination between the departments of health, animal husbandary, agriculture and forest.