308 MOSQUITOES OF NORTH AMERICA 



worms and as larvse or so-called microfilarise. The adult filariae are found in 

 the lymphatic vessels or in the connective tissues in various parts of the body. 

 The two sexes are usually associated, coiled about each other, and sometimes 

 several are coiled together. The larvae to which the female worm gives birth 

 find their way, in large numbers, into the blood and sometimes into the urine. 

 Man is the host of several species of Filaria, and, as in the case of the malarial 

 organisms, more than one of these may be present in the same individual. 



Only one species of Filaria is of marked pathological importance. This is 

 Filaria hancrofti, also frequently designated as Filaria (or Microfilaria) noc- 

 turna or Filaria sang uinis-lio minis. The presence of this parasite does not 

 necessarily produce sickness ; in fact it is well known that the filarias are often 

 present without the host showing any symptoms and they are only detected when 

 the blood is examined. However, a series of pathologic conditions are produced 

 by the presence of filariae in man, which, while they are seldom directly fatal, in- 

 capacitate to a greater or less degree. Manson, who is probably the best 

 authority on filariasis, gives as the result of the parasitism of Filaria hancrofti 

 in man the following filarial diseases : 



"Abscess; lymphangitis; varicose groin glands; varicose axillary glands; 

 lymph scrotum; cutaneous and deep lymphatic varix; orchitis; chyluria; ele- 

 phantiasis of the leg, scrotum, vulva, arm, mamma, and elsewhere ; chylous 

 dropsy of the tunica vaginalis ; chylous ascites ; chylous diarrhoea, and probably 

 other forms of disease depending on obstruction or varicosity of the lymphatics, 

 or on death of the parent filarise." 



Filariasis is a widely distributed disease in tropical and subtropical regions 

 and is especially common on the west coast of Africa, in South China, certain 

 parts of India and some of the islands of the Pacific. In certain islands of the 

 Society and Tonga groups, according to some observers, fully 70 per cent of the 

 population are afflicted with filariasis. In America it is very prevalent in the 

 West Indies. Dr. Mario G. Lebredo, in a recent paper, states that in the city of 

 Havana he found 17.82 per cent of filaria infection. He points out its dangerous 

 character and that there is reason to fear its general spread unless effective con- 

 trol measures are adopted. In the United States cases are occasionally found 

 in the Southern States and isolated cases occur further north, but it can not be 

 considered endemic. The forms of the disease appear to vary considerably ac- 

 cording to locality and on this account the belief has been expressed that more 

 than one species of Filaria is included under the name Filaria hancrofti. 



TRANSMISSION BY MOSQUITOES. 



The suggestion that mosquitoes are probably the carriers from man to man 

 of at least one of the parasitic worms of the genus Filaria, in one stage or 

 another, apparently was made about the same time by Bancroft, in Australia, 

 and Manson, in China. The evidence was first gained by Manson about 1878, 

 who thus became the discoverer of the first recognized transfer of a disease or- 

 ganism by mosquitoes. Manson found that mosquitoes which feed upon filarial 

 blood become infected and that the filariae undergo a metamorphosis within the 



