The effects of some chlorinated hydrocarbons as systemic acaricides against the cattle tick, Boophilus microplus (Canestrini)

Abstract

Subcutaneous injections of cattle with lindane, dieldrin, and aldrin solutions in peanut oil at the rate of 25 mg toxicant/kg body weight produced marked effects on infestations of Boophilus microplus (Canestrini). The numbers of ticks present at the time of the injection declined, but many developed to maturity. The most striking effect was the prevention of establishment of seed ticks. After injection, the average period of freedom from larvae for the lindane- and dieldrin-treated animals was from the 7th to the 22nd day and from the 12th to the 25th day respectively. For the aldrin-treated group there was a minimum number of larvae from the 16th to the 27th day. Dieldrin and aldrin continued to affect the reinfesting ticks even after they were able to establish as larvae, and the first appearance of each succeeding life history stage was progressively postponed. Animals injected with lindane exhibited their first persistent reinfestation of young adult ticks on the average 43 days after injection, dieldrin-injected animals 67 days after injection, and aldrin-injected aninlals more than 80 days after injection. Lindane was detected in the hair of injected cattle in three out of four experiments, but could not be detected in skin and blood samples. DDT injections at 25 mg/kg were without effect, and DDT could not be detected in skin, hair, and blood samples. Toxaphene, diazinon, and malathion produced no systemic effects on ticks when injected subcutaneously into cattle at 25 mg/kg. Isodrin likewise produced no systemic effect on ticks when injected into cattle a t the rates of 5, 10, and 15 mg/kg. Endrin at 5 mg/kg was also ineffective, but two animals injected respectively with 10 and 15 mg/kg endrin died. Compound L13/59, an organic phosphorus acaricide, produced no effect on ticks when administered orally to cattle at rates up to 50 mg/kg. Inunction of the neck of cattle with peanut oil solutions of lindane and dieldrin at the rate of 26 mg toxicant/kg body weight resulted in marked mortality of ticks over the entire body region, suggesting penetration of the skin and systemic effect from these toxicants. The lindane-anointed animal was free from larval ticks from the 3rd to the 11th day after treatment, and the dieldrin-anointed animal from the 3rd to the 21st day. Similar treatments with aldrin and DDT at 25 mg/kg were without systemic effect on the ticks. Although these results of injection are promising, the technique cannot yet be recommended for general use.