Is there an endemic focus of kala azar in Bombay?AV Pathare
Haematology Department, KEM Hospital, Parel, Bombay.
Keywords: Adolescent, Adult, Disease Outbreaks, Disease Reservoirs, Female, Human, India, epidemiology,Leishmaniasis, Visceral, epidemiology,transmission,Leper Colonies, Leprosy, complications,Male, Middle Age,
In India, kala-azar is believed to be confined to the north-eastern part of the country,. Bihar is the state most affected having witnessed two epidemics in 1977 and 1990 in spite of the on-going National Leishmaniasis Control Programme. The state of Maharashtra and the city of Bombay in particular, is considered free of the disease. The few stray cases that have been encountered locally are believed to have been "imported", i.e. the affected individual has caught the infection outside, in some endemic area, and then migrated to Bombay.
However, in the recent past, we have come across a few cases of kala azar in the city of Bombay; none of them had been to any of the known endemic areas of kala azar in our country.
The index case was a patient who was treated earlier for lepromatous leprosy. He had been an inmate of the Acworth Leprosy Hospital (ALH) for the past 42 years. His only known contact outside the leprosy hospital was his relative at Dombivli, a suburb of the city. He was referred to us for evaluation of pyrexia of unknown origin (PLIO) for the past 8 months. His bone marrow aspirate was teeming with Leishmania donovani (LD) bodies. This led us to review cases of PUO with or without sp lenomegaly refered to us from the ALH campus.
Amongst the 23 subjects (inmates and residents) studied, five more cases of leishmaniasis were diagnosed on the basis of demonstration of LD bodies in their bone marrow or splenic aspirates. [Table - 1] gives their demographic data.
Interestingly, case 6 was not a leprosy patient. He was the son of the hospital ambulance, driver who was staying in the hospital campus.
We also conducted a search for the vector for disease transmission, but we were unable to detect the phlebotomous spp. of sandfly amongst the various insects collected from the ALH campus.
Kala azar is a zoonosis and requires a susceptible host for its sustenance (reservoir of infection) anda vector for its transmission and spread. Man is the only known reservoir of infection in Indian Kala azar. There has been no documented animal reservoir as is seen in the other forms of leishmaniasis elsewhere in the world. Thus, the detection of six cases of kala azar in the inmate population of ALH is difficult to explain. The existence of the only known vector for transmission of this disease-the female sandfly was also not established.
A review of literature shows that sporadic cases of kala azar have been reported from Bombay earlier. But their origin could be traced to the endemic areas of Bihar, Bengal or Assam. Raghavan reported the first case from Bombay with no antecedent history of contact with the endemic areas. This patient hailed from Wadala village, which is in close proximity to the ALH campus where our cases have been observed.
A subsequent communication by Bhende et al in 1949, reported cases of kala azar amongst 18 autopsies performed on inmates of the ALH. On further investigations, these workers discovered seven additional cases of kala azars. They were also able to identify the existence of the sandfly locally at the ALH campus. Some of these insects were found to contain the promastigote forms of Leishmania donovani.
This shows that there exists a reservoir of infection amongst the inmates of ALH, since 1949, when the first “non-endemic” case was reported. The disease is probably spread by the phlebotomus spp. of sandfly, whose presence locally has been documented in the earlier report.
Our failure to detect the vector was probably due to the massive DIDT spraying operations, the local authorities undertook soon after we reported the findings of the index case. Also, since the practice of routine autopsies on the inmates dying at the ALH has been discontinued for the past two decades, there has been no report of kala azar in the intervening couple of decades till we found these cases.
I wish to thank the Dean, Seth GS Medical College and King Edward Memorial Hospital and Dr GH Tilve, Professor and Head, Department of Haematology for permitting use of hospital data.
[Table - 1]