408 PARASITISM A^D DISEASE IN RUFFED GROUSE 



Infections with animal parasites are picked up hy firouse in various ways. Eggs of the 

 intestinal worm ( Ascaridia) and cecal worm (Ileterakis) are passed from the infected birds in 

 the droppings, develop to an infective stage on the ground and are accidently picked up by other 

 birds while they are feeding. Eggs of some of the other parasites cannot develop to the stage 

 which can infect grouse without first being taken into the bodv of some other animal, gener- 

 ally a snail, insect, or other invertebrate. Grouse become infected with the gizzard worm 

 (Cheilospirura) by eating infected grasshoppers. Likewise stomach worms (Dispharynx) be- 

 come established from feeding on infected pill bugs, while tapeworms are contracted from 

 infected snails, beetles, slugs, ants and flies. Earthworms may be of importance in the trans- 

 mission of the crop worm (CapiUaria) and the gape worm (Syngamus). In these cases it is 

 obvious that the size and number of infections will be influenced by the numbers of the 

 intermediate hosts and the extent to which they arc used as food. A typical life cycle is 

 illustrated in figure 31. 



Another mode of infection is by the bite of insects. The one-celled animals which cause 

 malaria-like diseases of birds may be carried by black flics and louse flies. Table 63 presents 

 a list of the animal parasites reported from ruffed grouse. 



Plant Parasites. 



The plants which are commonlv thought of as parasitic in animals are the bacteria or 

 "germs". These are one-celled organisms, some of which can live in various situations outside 

 of animal bodies for long periods and yet under some circumstances cause disease when 

 taken into the body. Others can live but a short time away from flesh and blood. These must 

 depend on rather direct contact for their transmission. Still others may be normally found 

 existing harmlessly in some parts of the body but are capable of producing serious effects when 

 some other factor alters the function of the organ in which they dwell. 



In domestic birds bacteria are the cause of many diseases. Some, such as tuberculosis, are 

 occasicmally encountered in hand-reared grouse. However, the plant parasite which has been 

 identified most frequently as a cause of disease in wild grouse is a mold fAsperpilliis fumi- 

 gatus). TTiese microscopic plants are related to the bacteria but have a more complex struc- 

 ture and reproductive process. 



Filterable Viruses 



The agents causing cptlain diseases are so small that they can not be observed with ordi- 

 nary microscopes. One of their characteristics is the ability to pass through porcelain filters 

 which arrest the passage of organisms as large as bacteria. Because of this thev arc known as 

 filterable viruses. 



A disease of horses, corresponding to sleeping sickness in humans, equine encephalomyel- 

 itis, is caused by organisms of this tvpc. Tliis affliction also attacks humans and has been 

 reported from pheasants in the Easf"" and the prairie chicken in ihc \^'cst''. Recognition of such 

 wild reservoirs of disease is of great importance to puiilic health autborilics in the control of 

 diseases of Inimans ;umI domestic animals. 



Bird ])ox is an important di-casc of this group which is generally seen in domestic poultry 

 and game farm liirds. but it lias also been reported twice from ruffed grouse in New 

 England"'"'^. 



