DlROFlLARiA IMMITIS 



645 



Dirofilaria immitis Leidy, 1856. 

 This worm lives in the right heart and in the veins of the dog, and also of 

 the wolf and the fox, in Europe and tropical regions. It is very common in 

 China and Japan. 



Bowlby is commonly reported to have found it in the portal vein, kidneys, 

 bladder, ureters, and lungs of an Arab, and also in a rectal tumour in a youth, 

 but this is quite erroneous, as he never made any such statement, for the 

 eggs in the bladder and rectum, and the parasites in the portal vein of the 

 Arab, were Schistosoma hcematohium, as he carefully reported, never mentioning 

 D. immitis. Braun, however, seems to think it possible that this worm may 

 occur in man. 



Morphology. — The worm is long, measuring 12 to 18 centimetres by 0*7 to 

 0*9 millimetre in the male and 25 to 30 centimetres by I'O to 1*3 millimetres 

 in the female, and fihform, with a smooth rounded cuticle and a rounded 

 anterior extremity, on which is situated the terminal mouth with six small 

 papillae. The anus is subterminal, and the posterior extremity pointed. 



The male has a twisted tail with a cuticular fold on each side, and four pre- 

 anal and post-anal papillae. In the female the vulva is 7 millimetres from the 

 anterior extremity. Viviparous. 



Life-History. — The young larvae, 285 to 295 ^ by 5 ^, are not enclosed in 

 an egg-case, and have a tapering posterior extremity. They appear in the 

 peripheral blood particularly at night, when they may enter a mosquito if it 

 bites the dog. 



They enter the Malpighian tubules or their epithelial cells, where they 

 moult and grow, eventually passing via the body cavity to the labium. 



They escape through Button's membrane on to the s'dn when the 

 mosquito bites, and so enter the dog. 



liOa Stiles, 1905. 

 Filariidse with bosses on the cuticle and with large caudal papillae. 

 Species.— Loa loa Guiyot, 1778. 



Loa loa Guyot, 1778. 



Synonyms. — -Filaria oculi Gervais and van Beneden, 1859; 

 Dracunculus oculi Diesing, i860; D. loa Cobbold, 1864; F. subcon- 

 junctivalis Guyon, 1864. 



The larval names are: — F. sanguinis hominis vOiT. major Manson, 

 1891; F. diurna Manson, 1891. 



History. — ^That a Filaria occurred in the eye appears to have been 

 known since the end of the sixteenth century in Europe, and prob- 

 ably in Africa, especially in Angola, where it was called ' loa.' That 

 knowledge must have been very ancient. Mongin in 1770 appears 

 to have been the first person to record the presence of a worm 

 in the eye. Guyot, in 1778 and 1805, thought it was a Strongylus, 

 and used the term ' loa ' for the first time in European literature. 

 In 1891 Manson found a microfilaria in the blood of several negroes 

 from the Congo which differed from, those already described, and 

 which he named Fi'aria diurna, and further suggested that it 

 might be the larva of L. loa. Since then this hypothesis has been 

 proved to be correct by the observations of Penel, Prout, Henly, 

 Brumpt, Wurtz, and Kerr. L. loa and Microfilaria diurna are, 

 therefore, simply different stages in the hfe-history of the same 

 parasite. 



