Visceral Leishmaniasis
General Considerations.—There are two types of kala-azar, as the visceral leishmaniasis is termed, one the Indian kala-azar, which prevails in Assam, Madras, Indo-China, China and the Sudan and characterized by a subacute or chronic febrile course and splenomegaly in older children or adults and the other, the infantile type, which in over 90% of cases occurs in children under four years of age.
In 195 cases reported from Assam, by Mackie, 100 were in children between six and ten years of age so that it is hardly true to call Indian kala-azar a disease of adults.
The infantile type, which occurs chiefly in the countries bordering the Mediterranean, is usually stated to be caused by Leishmania infantum while the adult type is said to be caused by L. donovani. If, as is now thought, the two parasites are identical it will be necessary to drop the name L. infantum.
Epidemiology.—Whether Indian kala-azar is transmitted by the bedbug or infantile kala-azar by the flea are points which have not been experimentally proven. It must be admitted that epidemiological evidence supports the bedbug transmission view for the former.
On the other hand, Mackie dissected 322 bedbugs which he had fed on kala-azar cases with practically negative results. He also injected material from 588 bugs into two monkeys with negative results. Mackie was likewise unsuccessful with lice, mosquitoes and sand flies.
Rogers, investigating the disease in Assam, found that the usual history in the villages was that someone with the disease came to a village and subsequently other cases appeared. It was shown that where a village escaped while others near at hand suffered there was a history of nonintercourse with the infected villages. The natives took extreme steps to eradicate the infection, it having been reported that the Garos even burned the patients as well as their huts. All evidence shows that the infection is contracted by sleeping in an infected house. House epidemics and family epidemics are often noted.
At the same time various observers have frequently noted instances where an advanced case may associate intimately with his relatives for months or years and yet none of these develop the disease.
There is little to support the view that it is a contact infection, as such does not occur in hospitals where verminous insects are absent. By isolating the sick and moving the uninfected to new houses, only a short distance away, there is no spread of the disease. The disease practically appears only in those Europeans who live with or among natives.