LXXII. EPIDEMIOLOGICAL OBSERVATIONS IN MADRAS PRESIDEN CY. BY CAPTAIN J. C. KUNHARDT, I.M.S., AND CAPTAIN J. TAYLOR, I.M.S., ASSISTED BY ASSISTANT-SURGEONS R. GANPATI IYER, T. KESAVA MENON, B. V. VARADHACHARI, R. RAG- HAVENDRA RAO AND K. NARAYAN RAO. (With 7 Maps and 30 Charts.) INTRODUCTORY. IT is well known that while many parts of India have suffered severely from plague, the Madras Presidency has been affected relatively slightly by the disease. An inquiry to throw light on this apparent immunity was uindertaken by the Commission in the first instance in Madras City. The resuilt of this preliminary inquiry is embodied in the Seventh Report of Plague Investigations in India published as a supplement to the Joutrnal of Hygiene, 1912. These investigations in Madras City were directed to shov (a) whether the conditions in that city as regards rats, fleas etc. were such as to be favourable or other- wise to the spread of plague, and (b) whether Madras has escaped plaguie becauise infection could inot easily reach it. As was perhaps to be expected in connection with1 an epidemio- logical inquiry of this kind, no single outstanding circumstance was discovered which could account for the freedomii of the city from plague. On the one hand, rats and fleas were not so plentiful as in other plague- infected places investigated by us and perhaps so few as to render implantation of infection difficult, but there were probably sufficienit numbers of both to enable infection to spread when once successfully imiiplanted. On the other hand, the rats were found to be exceptionally susceptible to plague. These facts offered no satisfactory explanation of the immunity of Madras to plague, so that it seemed likely that the city had escaped plague because infection had been unable to reach it, in spite of the Journ. of Hyg. 44 684 -Epidemiological Observations in Madras Presidency fact that considerable traffic exists between Madras and the badly plague-infected town of Bangalore. Assuming that infection travels about the country for the most part in infected fleas associated either with merchandise, such as grain, or with the persons of humnan beings; it is clear that the likelihood of infection travelling any given distance will be proportional to the con- ditions being favoturable to the life of the rat flea. Experiments available at the time this inquiry was set on foot had shown (Seventh Report of Plague Investigations inl India, Supplement to the Journal of Hygiene, 1912, p. 317, see also Eighth Report, p. 613) that mneteorological conditions have a verv large influence on the duration of the life of rat fleas when separated from their normal host, a cool nmoist atmosphere allowing them to survive for about ten times as long as in hot dry air. Evidently, therefore, fleas would have some difficulty in arriving alive at any place which was surrounded by a zone of country where a high temperatuire, especially in conjunction with a low humidity, continuously prevailed. Madras City is, on the whole, a hot place, but though there is no definitely "cold weather" to afford really favouirable conditions for flea importation, the temperature in the cooler months would appar- ently allow fleas to live for some considerable time. Taking these facts into consideration it seemed proper to extend the scope of the inquiry to other parts of the Madras Presidency, paying special attention to the conditions which influence the facilities for the importation of infection. With this object in view, certain places were selected in which to establish small laboratories where investigations on rats and fleas were carried out on the lines adopted by the Commission in other places. Data were also collected bearing on the physical aspects and climate of the Presidency as well as on the facilities for communication between, and within, its various districts. A study of the distribution of plague in the Madras Presidency, as will be shown later in this report, revealed the fact that, so far as the intensity of plague was concerned, this area could be divided into three more or less well-defined zones. 1. The Bellary district, the Mysore plateau and the Nilgiri Hills which had all suffered severely from plaaue; 2. A zone lying immediately below and around the above-mentioned areas wvhich had suffered but lightly from plague; 3. The East Coast and Soutlhern portion of the Presidency which had escaped the ravages of the disease. Reports on Plague Investigations in India 685 Laboratories were therefore established in each of these zones. A large village called Denkanikota was selected as a suitable site for observations on the Mysore plateau. The towns of Coimbatore and Vaniambadi were chosen for observations in the zone below the Mysore plateau, while the town of Madura, with our previous observations in Madras City, represented the conditions in Southern India and on the East Coast respectively. At these selected places observations were made, throughout a whole year, on the prevalence of rats and fleas, while visits, for the purpose of collecting, data, extending for periods of about a fortnight at a time were paid to other places in the Presidency such as Ootacamund and Coonoor on the Nilgiri Hills, to Bellary, a town situated on a high lying plain to the north of the Mysore plateau, to the following towns on the West Coast: Mangalore, Calicut and Cochin; to Trichinopoly an inlanid town in the south of the Presidency; and to Cuddalore and Vizianagram on the East Coast, the former town being situated to the south of Madras in the district of the same name, while the latter is considerably further north in the district of Vizagapatam. The information which has been collected in this way is considerable and the reader will perhaps bear with us while we attempt to clear the ground for a proper understanding of the data by describing in the first instance the administrative divisions of the Presidency; secondly, its general physical features; thirdly, its climiatic conditions, and fouirthly, the general distribution of plague in the Presidency, duiring the present pandem-ic, leaving for more detailed discussion the distribution of plague in certain of the more important infected districts. I. Administrative divisions of Madras Presidency. For administrative purposes the Presidency is divided into 23 districts'. The districts have an average area of 7000 square miles and an average population of 1,879,0002. Each is divided into small areas called taluqs. For our purpose the districts may be conveniently divided into the following six main groups which are shown in Map No. 1: I This was the division up to 1910, and, as all the plague figures, maps, etc. available for investigation have been compiled in accordance with this division we have found it necessary to keep to this arrangement for our purposes, although a few rearrangements have recently been made. 2 All figures regarding population have been calculated on the 1901 census. 44-2 686 bEpidemiological Observations inlMadras Presidenc-y MADRAS PRESIDENCY SCALE OF MILES 100 50 100 ISO .L N I Z A M S D O M I N I O N S DISTRICT I Ganjam 13 North Arcot 2 Vizagapatam 14 South Arcot 3 Godavari 15 Salem 4 Kistna 16 Coimbatore 5 Guntur 17 Nilgiris 6 Kurnool 18 Malabar & 7 Bellary Anjengo 8 Anantapur 19 South Canara 9 Cuddapah 20 Trichinopoly 10 Nellore 21 Tahjore 11 C'hingleput 22 Madura 12 Madras 23 Tinnevelly Map 1 Reports on Plague Investigations in India 687 (1) T1he Northernit Circars: Ganjam District. Vizagapatam District. Godavari District. These districts have all been free from plague. Kistna District. Guntur District. ) (2) The Deccan or Ceded Districts: Kurnool District. Bellary District. Bellary has been severely infected while the others Anantapur District. have been affected to a lesser degree. Cuddapah District. (3) The East Coast Districts: Chingleput District. Nellore District. South Arcot District. Tanjore District. | Trichinopoly District. These districts have been practically free from plague. Madura l)istrict. | Tinnevelly District. Madras City. (4) The Central Districts: North Arcot District. t All have been moderately infected with plague, Salem District. especially Salem and Coimbatore. Coimbatore District. f (5) The WVest Coast Districts South Canara District. Localised epidemics have occurred in some of the Malabar District. larger towns of these districts. The few deaths has (6) The Nilgiris. 4 Nilgiris although showing relatively to its population been severely affected. II. The physical features of the Madras Presidency. The physical conformation of the Presidency is mainly determined by the two chief hill ranges-the Eastern and Western Ghauts. The Western Ghauts are a well-marked high range running along the western border of the Mysore.State within about 50 miles of the sea, averaging 4000 feet in height, and with peaks rising in some cases as high as 8000 feet. These mountains are to a large extent covered with forest. The Eastern Ghauts are a nmuch less well-defined range, usually about 2000 feet high, frequently interrupted and much further from the sea. They first form a hill area in the jungle district of the Northern Circars, and are then interrupted for some distance by the 688 Epidemniological Observations in Madras Presidency valleys of the Godavari and Kistna rivers; further south they are coi- tinued through the Guntuir and Kurnool districts as the Nallamalai Hills. The valley of the Penner river then interrupts the continuity of the hills which still fuirther south, however, rise as a series of ranges in the Central districts till they miieet the Western Ghauts at the southern extremity of the Mysore State. At this spot, where the Eastern and Western Ghauts merge into one another, the elevated Nilgiri Hills are situated.