PARASITES AND PARASITIC DISEASES OF DOGS 11 



CHIGGER INFESTATION 



Cause. — The common American chigger, Trombicula irritans 

 (also called harvest mite), is a small, red or orange-yellow mite 

 (fig. 7) which as a six-legged larva (the adult mite has eight legs) 

 attacks man and the domesticated animals. It occurs from New York 

 to central Mexico and from the Atlantic Ocean to the Rocky Moun- 

 tains. A very closely relates species occurs in the northern and 

 western part of this country. Chiggers have been thought to burrow 

 into the skin and die there, but recent investigations indicate that 

 they do not burrow, but merely attach by the mouth parts, and if 

 left alone become engorged and fall off. 



Symptoms. — Chiggers cause intense itching and 

 this results in scratching and rubbing which in turn 

 often result in the formation of sores with subse- 

 quent bacterial infection. Hunting dogs are espe- 

 cially subject to attack, owing to exposure as they 

 range over chigger-infested territory. The chiggers 

 attach most often about the head, feet, and belly, 

 causing scattering eruptions which may contain pus. 

 Chiggers usually attach singly, but a dozen or so 

 sometimes attach at one point. Under favorable Fl m on\m7rican chf - 

 conditions they may be seen with a hand lens, but ger, Trombicula 

 as a rule chigger infestation in dogs or cats would rfom 5 ' Ewfn g la Tn d d 

 be suspected from signs of itching coupled with a oude Z mans 191 (Micron 

 history of chigger attacks on man at the same time measurements: 

 and in the same vicinity. i?rvl^oio h n|b c yi e 6o 



Treatment. — Sulphur ointment will destroy chig- ilifV.Jrt 



. ■ r J fc> larva, 1.5 mm long by 



gers at the point of attachment and in some cases 320 microns wide. 

 appears to have a favorable effect on infected sores H.^Ewing!) by 

 due to scratching the places attacked by chiggers. 

 Alcohol in free and repeated applications is also good. Solutions of 

 coal-tar creosote dips, in the strengths recommended on the labels for 

 dipping or washing dogs, may be used. Ammonia, sodium bicarbo- 

 nate, or dilute tincture of iodine serves to alleviate the itching. 



Flowers of sulphur has been found of value in preventing attacks 

 on man by chiggers, and it is probable that it would be of value in 

 protecting dogs or cats if dusted into the hair. The coal-tar creosote 

 dips would doubtless be of value for the same purpose. Such dips 

 should not be used for cats. Oil of tar or fish oil, applied diluted with 

 alcohol, would probably be repellent but objectionably messy. The 

 cultivation of ground and the clearing away of underbrush and rank 

 vegetation aid in keeping down chiggers. 



TICK INFESTATION 



Cause. — Various species of ticks will attack dogs and about 14 spe- 

 cies have been reported from the dog in North America. The more 

 important of these in the United States are the American dog tick 

 or wood tick, Dermacentor variabilis, and the brown dog tick, Rhipi- 

 cephalus sanguineus; these ticks rarely occur on cats. 



