Deworming (sometimes known as worming or drenching) is the giving of an anthelmintic drug (a wormer, dewormer, or drench) to a human or animal to rid them of helminths parasites, such as roundworm, flukes and tapeworm. Purge dewormers for use in livestock can be formulated as a feed supplement that is eaten, a paste or gel that is deposited at the back of the animal's mouth, a liquid drench given orally, an injectable, or as a pour-on which can be applied to the animal's topline. In dogs and cats, purge dewormers come in many forms including a granular form to be added to food, pill form, chew tablets, and liquid suspensions.
Horses are most often dewormed with a paste or gel placed on the back of the animal's mouth via a dosing syringe; feed dewormers are also used, both single-dose varieties and in a daily, "continuous" feed form. Deworming (drenching) a sheep is usually done with a specific drenching gun that squirts an anthelmintic into the sheep's throat.
Mass deworming campaigns of school children have been used both as a preventive as well as a treatment method for helminthiasis which includes soil transmitted helminthiasis in children. Children can be treated by administering for example mebendazole and albendazole. The cost is relatively low.
While testing and treating children who are infected looks like it is effective, there is insufficient evidence to conclude that routine deworming, in the absence of a positive test, improves nutrition, haemoglobin, school attendance or school performance.
History of campaigns
Public health campaigns to reduce helminth infections in the US may be traced as far back as 1910, when the Rockefeller Foundation began the fight against hookworm – the so-called “germ of laziness” – in the American South. This campaign was enthusiastically received by educators throughout the region; as one Virginian school observed: “children who were listless and dull are now active and alert; children who could not study a year ago are not only studying now, but are finding joy in learning...for the first time in their lives their cheeks show the glow of health.” From Louisiana, a grateful school board added: "As a result of your treatment...their lessons are not so hard for them, they pay better attention in class and they have more energy...In short, we have here in our school-rooms today about 120 bright, rosy-faced children, whereas had you not been sent here to treat them we would have had that many pale-faced, stupid children."
Similar (albeit somewhat more imperialist) reports emerged from various other regions of the developing world at the time; for example, two scholars in Puerto Rico found that: "Over all the varied symptoms with which the unfortunate jibaro [peasant], infected by uncinaria [hookworm], is plagued, hangs the pall of a drowsy intellect, of a mind that has received a stunning blow...There is a hypochondriacal, melancholy, hopeless expression, which in severe cases deepens to apparent dense stupidity, with indifference to surroundings and lack of all ambition.’
Such observations made an intuitive connection between worm burden and intellectual performance, but even today this link is anything but well-established. While it seems that worms may impair cognition in some way, the mechanisms driving this relationship are still hotly debated.
- Horse care
- Levamisole, intended for veterinary use as a dewormer for cattle, pigs, and sheep
- Taylor-Robinson DC, Maayan N, Soares-Weiser K, Donegan S, Garner P (2012). "Deworming drugs for soil-transmitted intestinal worms in children: effects on nutritional indicators, haemoglobin and school performance". Cochrane Database Syst Rev 7 (7): CD000371. doi:10.1002/14651858.CD000371.pub6.
- Watkins WE & Pollitt E (1997). "'Stupidity or Worms': Do Intestinal Worms Impair Mental Performance?" (PDF). Psychological Bulletin 121 (2): 171–91. doi:10.1037/0033-2909.121.2.171. PMID 9100486.
- Bleakley, Hoyt (2007). "Disease and Development: Evidence From Hookworm Eradication in the American South". The Quarterly Journal of Economics 122: 73–117. doi:10.1162/qjec.121.1.73. PMC 3800113. PMID 24146438.
- Taylor-Robinson, DC; Maayan, N; Soares-Weiser, K; Donegan, S; Garner, P (14 November 2012). "Deworming drugs for soil-transmitted intestinal worms in children: effects on nutritional indicators, haemoglobin and school performance.". The Cochrane database of systematic reviews 11: CD000371. doi:10.1002/14651858.CD000371.pub5. PMID 23152203.