902 Animal Parasites in the Blood. 



8. Animal Parasites in the Blood. Haematozoa. 

 (a) Filaria immitis. 



{Filaria haematica.) 



Occurrence, The blood affection caused by filaria occurs 

 in China and in Japan very frequently among dogs, but it has 

 also been observed in other countries, although less frequently, 

 especially in East India, Tonkin, Brazil and North America. 

 In Europe dogs that were imported from Eastern Asia, or 

 which were kept there for a time became affected mainly, but 

 native dogs are not necessarily spared (Frohner, V. Eatz). 



According to Janson about 50% of dogs in Japan are affected with filaria 

 immitis, but about 75% of the affected animals show no symptoms of disease 

 whatsoever for a long time. 



Petropawlowsky in Charkow found 120 vagrant dogs infected, almost with- 

 out exception, while of 83 other dogs only 3 harbored filaria in the blood. Galli- 

 Valerio demonstrated filariosis haematica in 18.5% out of 162 autopsies on dogs in 

 Milan. 



Etiology. The full grown filaria immitis is a long, white 

 worm, of about 2 millimeter thickness. The male is 12-18 cm. 

 long, its posterior extremity shows a spiral bending ; the female 

 is 20-30 cm. long and gives birth to living embryos. 



The sexually mature filaria live especially in the right half 

 of the heart, more rarely in the pulmonary arteries, very rarely 

 in the vena-cava, and only very exceptionally in the left half 

 of the heart or in the arteries of the large blood circulation. 

 They are found at these places in varying numbers, sometimes 

 up tp several hundred, rolled up in a ball which is difficult to 

 untangle, in which the female's give birth to embryos about % 

 mm. long which may then gain entrance to the circulating blood 

 in very Jarge numbers (Rieck estimated them in one case up 

 to several millions). Not infrequently however the sexually 

 mature filaria may be present at the same time also exclusively 

 in the subcutis. 



The mode and manner of the natural infection is not yet 

 known with certainty. The infection is probably transmitted 

 by impure swampy water, which the frequent occurrence of 

 the disease in marshy localities of the warmer countries seems 

 to substantiate fully. The dogs probably take the larvae of 

 the parasite with their drinking water. These then reach the 

 heart with the venous blood and there they mature. The 

 embryos may leave the animal with some of its blood or some- 

 times with the excrement and the secretions of the air passages 

 (Janson), principally however with the urine, and may then 

 reinfect the drinking water. The artificial transmission of the 

 disease by inoculation of blood containing filaria has never been 

 successful (Frohner). According to Janson and Galep & 

 Pourquier the embryos are supposed to pass, sometimes to the 



