Medical Geography

MEDICAL GEOGRAPHY (nosogeography), a branch of medicine that studies the distribution of various diseases, predominantly infectious ones, across the globe. The tasks of medical geography include identifying the territories most affected by a given form of disease, as well as studying the external factors influencing changes in the disease distribution map. The broader tasks of studying all external and internal conditions for the emergence of diseases in various parts of the globe belong to geographical pathology. The number of factors can be extremely large, and their interaction must be strictly accounted for each time. The spread of diseases can depend on the latitude of the locality, altitude above sea level, climate and natural conditions, social and domestic factors, the presence of animals and insect vectors of diseases, conditions favoring their life and development, etc. Recently, in the spread of certain infectious diseases, great importance has been attached to "virus reservoirs," which are usually particular animals in which this virus persists and even increases quantitatively during the interepidemic period. Such a reservoir, for example, in leishmaniasis is considered to be infected dogs, in plague—rodents, etc. Since many of the listed factors can change or even disappear completely, medical geography is also variable. To obtain a clearer idea of the degree of disease spread and the areas covered by them, special nosogeographical maps are compiled (see map). Comparing such maps over a number of years, it can be noted that some diseases remain strictly within their geographical boundaries (so-called endemic foci), others in certain years go beyond their endemic distribution, giving rise to epidemics and pandemics, or, finally, individual foci, decreasing, may completely die out. On the other hand, foci of one disease or another that have died out or remained inactive for many years sometimes begin to function again. The foci of certain diseases can sometimes be sharply limited depending, for example, on the presence of the disease vector insect only in a given area. Thus, in the USSR, in Ganja (formerly Elizavetpol), there is a focus of oriental sore (cutaneous leishmaniasis), and three versts from the city, at the railway station of the same name, not a single case of this disease has been recorded. Foci of diseases also arise anew if, for example, a person ill with the given disease in the period of parasite carriage accidentally gets into an locality where the vectors of the given disease are distributed. An example is the outbreak of dengue fever in 1928 in Greece, which arose in connection with the introduction of infection into an locality where its vector—the mosquito Aedes aegypti—was present. Foci of diseases can disappear along with the rise in the sanitary culture of the population and the implementation of prophylactic measures (see below). Natural and social disasters: famine, wars, etc. (for example, the pandemic of listerial/parasitic typhus and malaria after the World War), can also have a major impact on the revival of foci and the development of epidemics. To prevent epidemics and other mass diseases, it is necessary not only to know the endemic foci, but also to clarify all the conditions contributing to their existence. For example, we can dwell on the medical geography of certain diseases. Endemic foci of goiter (see) are considered to be Switzerland, Manchuria, and some countries of South America, and in the USSR—Svanetia, Transbaikalia, and individual regions of Central Asia (Kokand). Comparing these foci in climatic and geographical relations, one can see that the majority of them are located in mountainous regions, although there are also foci located not high above sea level (Kokand). According to many authors, the cause of goiter is certain properties of drinking water, in particular the bacterial flora of the latter. Nowadays, the microbial theory of goiter is again being brought to the forefront. In South America, Chagas' disease (Chagas) is described, accompanied by symptoms of goiter or myxedema, the causative agent of which is a special animal parasite—Trypanosoma cruzi—and the vectors are flying bugs Triatoma megista and Rhodnius prolixus. In Transbaikalia, Beck's disease (see Beck's disease) is endemic, the causes of the endemicity of which were investigated by Russian researchers (Beck, Barykin, Shchipachev, and others) and are also apparently related to the composition of drinking water. India (mouth of the Ganges) has long been considered an endemic focus of cholera (see), which spread from there by two routes: overland—through Afghanistan, Persia, the Volga region, and Transcaucasia, and maritime—through the Red Sea, Egypt, and the port cities of Southern Europe. The exact study of cholera foci and the causes of its epidemic spread, as well as the study of the preservation of the cholera vibrio in the interepidemic period, is one of the important chapters of medical geography. Endemic foci of plague (see) are: China, India, Central Africa, Mesopotamia, Persia, Egypt, California, the Kirghiz steppes, Transbaikalia, Mongolia, and Manchuria (see map). The cause of the endemicity of plague is plague epizootics in local rodents. Such keepers (reservoirs) of the plague virus are rats, and the vector is rat fleas Xenopsylla cheopis, Xenopsylla astia, and others (India, Egypt). In the southeast of the USSR, plague outbreaks are supported thanks to epizootics in gophers and mice. In Transbaikalia (Borzya, Dauria), Mongolia, and Manchuria, the cause of the endemicity of plague is tarbagan disease (tarbagan—Arctomys bobac), in the transmission of which the flea Ceratophyllus silantiewi plays a role. The faunistic and climatic features of endemic foci of plague are the reason for the long-term storage of the virus in a given area and determine periodic epidemic outbreaks here, serving as a source for the further spread of plague. The spread of leprosy (see) also corresponds to certain localities (see map). In Europe, the coastal countries most affected by leprosy are Norway, Estonia, Latvia, Turkey; in the USSR—Astrakhan Governorate and individual localities in the Caucasus. Leprosy is found in large numbers in China, India, in tropical and North Africa, in South America, in Japan, in the Sunda Islands, in Siberia (in the Yakut Republic), the Far Eastern Region, and in Australia. Of great interest is the geographical distribution of yellow fever (see), which until recently was a scourge of South America and Africa (see map). In America, it was distributed mainly along the eastern coast, between 43° north and south latitude; in West Africa, yellow fever is found on the Gold Coast. The geographical distribution of yellow fever does not go beyond the distribution of its vector—the mosquito Aedes aegypti (Stegomyia fasciata)—which, however, is distributed across the globe much more widely (it is also found in the USSR, on the Black Sea coast, south of Sukhumi). Therefore, besides studying the foci of yellow fever themselves, clarifying the distribution zone of Aedes aegypti is of great importance in this regard, since all localities where it is found can become areas of future epidemics. [The attached map shows the global distribution of leprosy (according to Rogers), yellow fever in 1919 (according to Stitt), and plague in 1926 (according to Rapport épidémiologique de la Société des Nations)]. Malaria (see) is distributed much more widely than yellow fever. Its vector, Anopheles maculipennis and other species thereof, develops wherever there are reservoirs of clean standing or slowly flowing water. The distribution of various species of the malaria parasite (Plasmodium vivax, Plasmodium malariae, and Plasmodium praecox) is geographically unequal. The tropical malaria parasite (Plasmodium praecox) prefers hotter localities (the Caucasus, Central Asia), while the tertian fever parasite (Plasmodium vivax) rises significantly further north. For the development of the malaria parasite in the mosquito's body, a temperature of no less than 16–20° is required. Although Anopheles mosquitoes are widespread everywhere, malaria does not develop everywhere due to the absence of sources of their infection (parasite carriers) and due to temperatures not suitable for the development of the parasite in the mosquito's body. The intensity of malaria spread increases from north to south in connection with climatic conditions, and certain localities and countries have acquired the reputation of being exclusively malarial, for example, Italy, tropical Africa, India, the Caucasian-Persian coast of the Caspian Sea, the Lower Volga region, etc. In some areas, conditions favoring severe outbreaks of malaria were sometimes temporarily created, for example, the digging of the Panama Canal, the inappropriate use of the irrigation network in Central Asia and Transcaucasia (Mugan), etc. African sleeping sickness (see Encephalitis), which caused great devastation, is also closely related in its geographical distribution to a specific insect vector, found only when the distribution map of human sleeping sickness (trypanosomiasis) was compared with the distribution map of African blood-sucking insects.

In this way, it was possible to establish that out of three species of blood-sucking insects of these localities, it is precisely the fly Glossina palpalis that is the true vector of sleeping sickness. Leishmaniasis (see), both cutaneous (Pendjeh sore) and visceral (kala-azar, see), is encountered in hot climates, in particular in Central Asia and Transcaucasia, and in its distribution, apparently, depends on insect vectors, with dogs and cats also falling ill with leishmaniasis, possibly playing a certain role in the spread of these diseases. Various spirochetoses, including relapsing fever, depend in their distribution on transmitters, in some cases lice, in others ticks, while European relapsing fever transmitted via lice cannot, for instance, be transmitted by the tick Ornithodorus moubata, and, conversely, tick-borne relapsing fever transmitted by this tick cannot be transmitted through lice. The geography of these fevers is therefore not identical. Dengue fever (see), distributed predominantly along the shores of the Mediterranean and partly the Black Seas, and pappataci fever, distributed in the Crimea and Transcaucasia, likewise depend on the presence of intermediate hosts, which in dengue fever are the mosquitoes Culex fatigans and Aedes aegypti, and in pappataci fever the phlebotomus sandfly Phlebotomus pappatassii. The distribution of the vectors is connected with certain climatic conditions. Some of the mass diseases are connected not only with local climatic conditions, but apparently also with local domestic and everyday conditions, for example, Malta fever, distributed along the shores of the Mediterranean Sea and also encountered in the USSR in the Caucasus and Central Asia, the causative agent of which is a micrococcus (Micrococcus melitensis) and which is spread through milk and dairy products. The same can be said regarding certain helminthic diseases (see Human helminthiases). Thus, infection with the broad tapeworm (Diphyllobothrium latum) is frequently encountered among populations that consume fish, and trichinosis infection is usually observed among populations that consume pork infected with trichinae, and so forth. The Guinea worm of man belongs to the diseases of the hot climate. Its vectors are water cyclopes, and infection occurs through water. To a certain extent, this disease is also occupational, since almost all water-carriers are infected with it. The spread of certain other infectious diseases of an occupational character also has a strict territorial limitation. Thus, the disease tularemia, which affects hunters of water rats, usually spreads only along the course of the rivers where these rats live. To this kind of occupational diseases one should also refer certain other helminthiases, such as, for example, ancylostomiasis (see Ancylostoma), which affects miners in deep mines or workers on earthworks in localities with a hot and humid climate. Characteristic diseases depending on the climate are also fungal skin diseases—favus, trichophytosis, and the like, which are especially strongly distributed in localities with high temperature and high humidity. Enhanced sweating, disturbance of skin respiration, decomposition of sweat, and a change in its reaction are factors contributing to the development of fungi. Under these conditions, precisely in the tropical climate, the skin integuments are more easily traumatized, and in the tropics one observes such special diseases as mycetomas (Madura foot), and the like. To the diseases connected with the climate belong, further, various intestinal diseases distributed in the south, in particular sprue, amoebic dysentery (see), avitaminoses, such as, for example, in the north (in the absence of fresh vegetables and potatoes)—scurvy (see), and in the south (with predominant consumption of corn)—pellagra (see). The monotony of the northern MEDICAL

climate is reflected also in the mental state of the population and leads to a whole series of nervous diseases (for example, a special form of hysteria—meryecheniye, chiefly among women of the north). To enumerate all the principal diseases from the standpoint of their medical geography is an extremely difficult task, but it is clear that the factors influencing medical geography are extremely diverse. At the same time, one cannot view one or another disease in isolation. Medical geography must embrace not only the diseases of man, but also of animals (tropical piroplasmosis of cattle, trypanosomiasis of camels, and so on) and plants, and study the vectors—insects, crustaceans, mollusks, and the like. Only by comparing these data and studying them in such an aspect can one give a correct assessment of the distribution and territorial factor of one or another disease and establish a true understanding of medical geography. It must be pointed out that historically medical geography as a broad problem of medicine was studied most fully at the end of the 18th century and in the first two thirds of the 19th century. To this period belong the best-known works on medical geography (Hirsch, Boudin, and others). The development of bacteriology to a certain extent delayed the study of medical geography, but only for a certain time. The establishment of the role of living vectors of infections (rodents, insects, etc.) once again brought forward the problems of medical geography.

D. Zabolotny. The role of sanitary culture and prophylaxis in changing the geographical distribution of diseases. It must be especially emphasized that the geographical distribution of diseases is by no means constant and something inevitable. The study of the nature of diseases and the establishment of the causes that cause them has given humanity the opportunity to develop methods for eliminating these causes and, through the implementation of mass preventive measures, to free both individual localities and entire countries from diseases that have dominated for centuries and seemed inevitable. This is especially evident in relation to infectious diseases. Plague, which caused huge devastation in Europe even in the middle of the 19th century, is currently observed in it only in isolated cases, mainly in port cities. Measures to monitor ships arriving from unfavorable places and to monitor the territory of ports, in particular mass deratization, have led to the fact that the penetration of plague deep into most European countries is now completely excluded. An example of the complete destruction of plague in its permanent focus can serve the island of Formosa (Japan). Plague here repeated annually from 1897 to 1917 for 21 years. During this time, about 30,000 cases of the disease and 24,000 deaths from plague were recorded. A series of preventive measures - mass destruction of rats and the reconstruction of buildings (dwellings, warehouses) in order to make them inaccessible to rodents - succeeded in completely destroying plague on this island: after 1917, diseases on Formosa were no longer observed. Preventive measures carried out in the foci of plague in the USSR, and the increase in agricultural and sanitary culture in them, give confidence that these foci will be neutralized in the near future (for details, see Plague). - Cholera struck Europe for almost a century; from Bengal, its permanent focus, in 1823 it first reached Astrakhan, in 1829 it reached the Orenburg province and then gradually struck the eastern provinces of Russia, Finland, Poland and a significant part of Western European countries (in 1831), simultaneously penetrating into North America and Australia. Thanks to the discovery of the cholera pathogen (Koch's work) and the establishment of a system of preventive measures to combat it - improvement of water supply and sewerage, early laboratory diagnosis, mass preventive vaccinations, monitoring of ships arriving from unfavorable places, monitoring of pilgrims, etc. - cholera at present in Western Europe as a mass epidemic has disappeared. In the USSR, where it persisted for over a hundred years and where after the world war it raged on an extremely large scale, cholera, as a result of mass preventive measures, gradually began to disappear, and in recent years (1927-28) not a single case of it was observed throughout the USSR. - The role of preventive measures is no less definitely manifested in the change in the geographical distribution and other intestinal infections, e.g., typhoid fever. The implementation of properly equipped central water supply and sewerage quickly changed the picture of typhoid fever incidence and turned its malicious foci into places with a low incidence of it (examples from Russian cities - Odessa, Moscow). Raising sanitary culture and the systematic implementation of mass vaccination in the Red Army led to the fact that it currently gives minimal morbidity and mortality from typhoid fever, significantly lower than in the pre-war Russian army (for details, see Waterborne infections and Typhoid fever). - The spread of smallpox can also serve as a classic example of the impact of preventive measures on the change in the geographical distribution of diseases. Having produced terrible devastation in Europe until the middle of the 19th century, smallpox, under the influence of mass preventive vaccinations, began to gradually disappear, and at present in most European countries it is found only in isolated cases. In the USSR, thanks to the gradual implementation of compulsory universal vaccination (see), it is now kept well below pre-war times and gives major outbreaks exclusively in the most culturally backward outskirts (see Smallpox). - Relapsing fever (see) until relatively recently was one of the most formidable scourges for Europe. Ireland and England were considered its classical foci. In the 80s of the 19th century, it was still raging in Germany. At present, thanks to the raising of sanitary culture (destruction of lice), it has almost completely disappeared in most countries of Western Europe. The same applies to typhus (see). Many of the malicious foci of malaria (see) have been made completely free of it (Italy, South America, in the USSR resort areas, Bukhara) thanks to preventive measures (drainage of marshy areas, destruction of Anopheles mosquitoes, systematic treatment of parasite carriers, etc.). - The almost complete disappearance of yellow fever (see) in South America, thanks to the systematic destruction of its vector - the mosquito Stegomyia fasciata, can also serve as a typical example of the topic covered here. - This also includes the disappearance in most European countries as a mass disease of anthrax (see) thanks to the organization of proper veterinary and sanitary supervision. - Trachoma (see) has also disappeared in most European countries as a result of raising sanitary culture and the mass implementation of preventive measures. In relation to leprosy (see), humanity began to apply preventive measures (isolation from patients) in deep antiquity, and at present it has survived on the globe in very few foci. - From what has been said, one must come to the conclusion that mankind, having abandoned the view of the origin of diseases as something fatal and having started studying their causes by a purely scientific method, approached the scientific elaboration of ways to eliminate these causes: Applying in practice the results of this study, the mass implementation of preventive measures, it sharply changes the character of the geographical distribution of diseases, in the sense of destroying a number of their foci. Further raising of sanitary culture and the development of the preventive direction in medicine should lead to an even greater restriction and destruction of foci of infectious diseases. At the same time, the general rise in culture and the change in social conditions towards a more uniform distribution of the benefits of life should also lead to a decrease in the incidence of infectious diseases; the transformation of society on socialist foundations will be one of the main factors of this reduction.

I. Dobreytser.

assistant professor of the Military...

department of private pathology and therapy in...

The result of G.'s scientific activity is over 30 scientific works, of which the principal ones are: "To the question of the action of thyroid preparations on the animal organism" (diss., St. Petersburg, 1896); "On the epidemic of trichinosis in Kharkov in November 1907" ("Russian Doctor", 1908, No. 3); "Experimentelle Untersuchung über die Wirkung des Extr. filicis maris aethereum auf das Blut" (Zieglers Beiträge, B. XXIV, 1898); "Phenylcinchoninsäure (Atophan) bei Gicht" (Deutsche med. Wochenschr., 1911, No. 22).