Antiparasitics, animal

Spinosyns were discovered from the fermentation broth of Saccharopolyspora spinosa by screening for mortality of blowfly larvae, and a mixture of spinosyns A (116) and D (117) was approved and used successfully as a crop protection and an antiparasitic animal health agent. (151) Nodulisporic acids are an indole diterpenoid class discovered from various species of Nodulisporium as orally active antiflea and antitick agents for dogs and cats (152, 153). The most active of the series is... 

Chemically synthesized antimicrobials used in animal and poultry feeds include arsenicals, eg, arsanilic acid [98-50-0] sodium arsanilate [127-85-5] and roxarsone [121-19-7]-, sulfa dmgs, eg, sulfadimethoxine [122-11-2], sulfamethazine [57-68-1], and sulfathiazole [72-14-0]-, carbadox [6804-07-5]-, and nitrofurans, eg, furazoHdone [67 5-8] and nitrofurazone [59-87-0] (see Antibacterial agents, synthetic Antiparasitic agents). 

Parasiticides can be roughly divided according to parasites, host species, or chemical classification (see Antiparasitic agents—anthelmintics Antiparasitic AGENTS—ANTiPROTOZOALs). By any classification, these are ubiquitous in the management and control of parasites of both companion and food-producing animals (2,3). 

The polyether antibiotics exhibit a broad range of biological, antibacterial, antifungal, antiviral, anticoccidial, antiparasitic, and insecticidal activities. They improve feed efficiency and growth performance in mminant and monogastric animals. Only the anticoccidial activity in poultry and catde, and the effect on feed efficiency in mminants such as catde and sheep are of commercial interest. 

By contrast, when allopurinol riboside (11.19), a metabolite of allopuri-nol and an antiparasitic agent, is administered orally to humans, the drug is incompletely absorbed. The residual fraction is then extensively metabolized by the enteric flora to produce metabolites that are absorbed [41], Bacterial metabolism proceeds by cleavage to allopurinol, a reaction that apparently occurs only in the intestine. Although the examples described pertain to different animal species, it is clear that small structural changes can elicit major differences in metabolism. 

Since about 1952, the American public has been amply supplied with meat produced largely from animals that received feed containing antibiotics. These and other chemicals, including sulfonamides and antiparasitic drugs such as anthelmintics and coccidiostats added to feed, have saved labor, feed and space, thus revolutionizing animal agriculture. The record of safety of antibiotics in animal feed in the US has been excellent, including safety to producers and meat handlers as well as to consumers. 

Anthelmintic agents are a smaller, less diverse group than antimicrobial agents. They include levamisole and the benzimidazoles, and the newer avermectins. The benzimidazoles include thiabendazole which has also been used as a pesticide on plants and as a food preservative. Chemical methods have been used widely to quantify the residues of these substances in food, as part of national control programmes. They are an important sub-group of the antiparasitic agents that many consider to be essential for good animal husbandry. 

Crews, P, and Hunter, L., The search for antiparasitic agents from marine animals, in Marine Biotechnology, Volume 1 Pharmaceutical and Bioactive Natural Products, Attaway, D. H. and Zaborsky, O. R., Eds., Plenum Press, New York, 1993, 343. 

The use of pyridine and quinoline derivatives in the growth of poultry and related animal industries is described in CHEC(1984) <1984CHEC(2)511>. In CHEC-II(1996) <1996CHEC-II(5)245>, discussion of veterinary products had subsections covering anthelmintics, antiparasitics, and antibacterials. It is pointed out in CHEC-II(1996) <1996CHEC-II(5)245> that drugs developed for human use often find a place in veterinary medicine. 

With whole-herd applications of antimicrobial and antiparasitic substances and live vaccines in mind, ecotoxicity assessments have been included in the registration reqirements for veterinary products in the EEC and the USA. A defined procedure exists in the USA where a "Finding of no significant impact" (FONSI) certificate by the Animal and Plant Health Inspection Service (APHIS) is a necessary prerequisite for the registration. 

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