Submitted to: Journal of Parasitology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/10/2010
Publication Date: 6/1/2010
Citation: Fetterer, R.H., Jenkins, M.C., Miska, K.B., Cain, G.C. 2010. Metam sodium reduces viability and infectivity of Eimeria oocysts. Journal of Parasitology. 96:632-637. Interpretive Summary: Poultry coccidiosis is the result of an infection with several different species of a protozoan intestinal parasite which causes considerable annual losses to the poultry industry. The primary control for the disease is through application of medications in the feed as birds are raised in confinement housing. The controls by medications are becoming less effective because of increased resistance to the drugs. Current controls target the invasive stage of the parasite within the chicken. However, the oocyst which is shed into the chicken litter by infective birds is the infective stage of the parasite. Inactivation of oocysts by treatment of the contaminated litter has not previously been considered as control strategy for coccidiosis. The current study demonstrates that a widely used agricultural pesticide, metam sodium (MS), significantly reduces the viability and infectivity of isolated oocysts of three important species of poultry coccidia. It was also shown that application of MS to poultry litter containing occysts of several species of poultry coccidia virtually eliminates pathology when the treated litter is fed to chicks. The results of this study demonstrate the possibility of reducing poultry coccidiosis by decontamination of the litter.
Technical Abstract: Metam sodium (MS, sodium N-methyldithiocarbamate) is a widely used soil pesticide. Fumigation or chemical sterilization of poultry litter containing infectious oocysts could be an effective strategy to block the transmission of avian coccidia. In the current study the effect of MS on the viability and infectivity of Eimeria oocysts was investigated. The development of isolated, unsporulated oocysts of both E. tenella and E. maxima was inhibited in a dose related manner (IC50 8 to 14 µg/ml), by exposure to aqueous MS. Most treated oocysts failed to develop beyond early stages of sporulation. To determine the effect of MS on infectivity, isolated oocysts of E. tenella, E. acervulina and E. maxima were exposed for 24 hr to aqueous concentrations of MS ranging from 0 to 1000 µg/ml. Treated oocysts were inoculated into chickens and parameters of coccidiosis infection were compared to chickens inoculated with equal numbers of untreated oocysts. MS significantly reduced the infectivity of oocysts in a dose related manner with maximum effect observed at a dose of 300 µg/ml. When a mixture of oocysts containing three coccidian species was exposed to 300 µg/ml MS from 0 to 24 hr, infectivity of oocysts was significantly reduced after a minimum of 12 hrs of exposure. Treatment of aqueous slurries of litter samples obtained from commercial poultry houses with 300 µg/ml MS for 24 hrs prevented the sporulation of Eimeria oocysts in the litter samples relative to untreated control samples. The results indicate that MS could be used to reduce coccidial contamination of poultry litter.