l86 FLEAS, FLUKES AND CUCKOOS 



hosts. It is also not known whether the microfilariae in birds swarm 

 periodically as they do in man. 



The members of the order Enoplida are often called whipworms 

 because, in some species, the posterior end of the body is thickened and 

 looks superficially like the handle of a whip, while the narrow slender 

 anterior portion is reminiscent of the thong. They are found in a wide 

 range of hosts and in some queer situations. The best known whip- 

 worm is Trichinella spiralis, which is the cause of a serious, sometimes 

 fatal disease in man, and which is contracted by eating underdone, 

 infected or so-called "measly" pork. When the-Hfe cycle of this worm 

 was discovered in 1828 it was thought that a great light had been shed 

 on the ancient Hebrew law which bans the consumption of pig. This 

 superficial and facile explanation is made without any foundation, 

 although some scientific books declare it is "without doubt" true. 



Trichurata are particularly common in the crops and intestines of 

 birds. The most familiar genus is Capillaria, and needless to say, the 

 unfortunate chicken has its full share of this particular trouble. These 

 worms live more or less embedded in the intestinal mucosa. One of the 

 best known species is C. columbae, a hair-like worm less than half an inch 

 in length, which also infects pigeons and peacocks. The life-cycle is 

 direct. The eggs require several days to become infective but only hatch 

 after being swallowed by the host. They enter the mucosa of the duode- 

 num and complete development there before returning to the lumen of 

 the intestine. In certain species, such as C. annulata, infecting the 

 crops of chickens and other birds, the embryos have to mature in- 

 side earthworms which serve as true intermediate hosts. There are 

 also various species of Capillaria which undertake long migrations 

 through the host's body before taking up their final position. A com- 

 mon species in British wild birds, ranging from buzzards to robins, is 

 C. contorta. The genus is one of the largest and infects mammals as 

 well as avian hosts. 



Chickens with heavy infections of Capillaria show an inclination for 

 solitude, become extremely thin, and eventually die. Although many 

 species of worm appear to have little or no effect on their bird host, this 

 is, in all probabihty, because we cannot ask them about their symp- 

 toms. Heartburn, dizziness, insomnia, optical illusions, general 

 nervousness, flatulence, abdominal discomfort, reduced perspiration, 

 palpitations of the heart, dirt-eating and loss of vitality due to nematode 

 infections are listed in a book on human parasitology. This type of 



