Some Aspects of Tropical Diseases as Seen at Home

PATIENTS who return from the tropics may present a great variety of clinical syndromes. They may present themselves as a pyrexia of unknown origin, requiring special investigations for such conditions as malaria or visceral leishmaniasis, or with the dysenteric syndrome, requiring sigmoidoscopy and search for entamoeba histolytica in scrapings from the bowel. There may be undue loss of weight when sprue may enter the picture, or there may be a typical distribution of phrenic nerve pain produced by a liver abscess. Then there are the great varieties of helminthic infestations. The patient with ankylostominosis may be profoundly anaemic, or he may have abdominal symptoms closely resembling those of duodenal ulcer. Cysti-cercosis must always be borne in mind in those who develop epilepsy; occasionally this condition may be caused by other infestations, such as cerebral schistosomiasis, especially in schistosoma japonicum infestations in people from the Far East. And so it is that tropical diseases can produce diverse symptoms and signs, from fever to sore tongue, abdominal tumours due to splenomegaly, general wasting, abdominal symptoms chiefly related to the large bowel, hematuria, and, more rarely, evidence of filarial infestation, such as lymph scrotum. Recognition of this wide variety of clinical evidence is important, for tropical infections can often be specifically diagnosed and specifically treated. It is not possible in this paper to consider more than a very few points in relation to tropical diseases as seen at home, and so I propose to deal with the commonest condition, that is, malaria. This disease alone may present most varied clinical conclitions, such as recurrent pyrexia, jaundice due to bilious remittent fever, or blackwater fever, coma, or mental symptoms due to cerebral involvement, or chronic ill health. In order to properly understand malaria as seen in the non-immune European, there are certainly fundamental facts first to be considered, for these are the basis of rational treatment with the various specific drugs, and especially paludrine. Malaria infection is acquired under natural conditions in one way only, namely, by the bite of an infective female anopheline mosquito, i.e., the mosquito must have sporozoites in its salivary glands. Can naturally-acquired malaria occur at home? It is possible, for the local species of anopheles, anopheles maculipennis is an efficient vector, but the odds are against it, for the mosquito is cold-blooded, and development of the malaria parasite in the mosquito is very sensitive to the atmospheric temperature. However, …